v1.4.1: bump version (freemkv-unlock git-pinned for the tag)

AACS content decryption rejected a whole 6144-byte aligned unit unless
EVERY content packet was conformant MPEG-TS. One authored-bad packet (a
pressing/encoding defect or an AACS 2.1 forensic-variant frame) made the
mux conceal the entire unit as NULL TS — destroying up to 31/32 good
packets and tallying them as loss, surfacing as false "corruption" on
otherwise-clean discs (observed across two UHD titles).

decrypt_unit now asks only "did a key OPEN this unit?" — a padding-aware
>=75% supermajority of content packets restoring their 0x47 sync, a gate
no wrong key can reach (uniform-AES noise floor) yet one that tolerates a
minority of authored-bad packets. Opened units pass through VERBATIM; a
non-conforming packet is left for the demuxer to drop on sync-loss and
resync past. TS-sync conformance is a muxer concern, never a decryption
verdict. The post-read verify/sweep gate now shares the same primitive so
it can never disagree with the mux decrypt.

Also unify the MVC (Blu-ray 3D) track signals: the mvcC CodecPrivate
extension, the BlockAdditionMapping, and each per-frame BlockAdditional
all derive from one MVCDecoderConfigurationRecord built once per track, so
a malformed dependent-view parameter set can no longer orphan a BlockAddID.

.github/workflows/release.yml

@@ -39,29 +39,11 @@ jobs:
       # would always fail (no lockfile to lock against on a fresh runner).
       - run: cargo test
 
-  # crates.io publish is an INDEPENDENT job: it serves EXTERNAL consumers only.
-  # The freemkv binaries no longer depend on it (they git-tag-pin libfreemkv via
-  # a committed [patch.crates-io]), so this publish runs in parallel with their
-  # release builds rather than gating them. It `needs: [verify, test]` so a
-  # failing test suite still blocks publication to crates.io — external
-  # consumers who `cargo add libfreemkv` must never receive a release whose
-  # tests were failing. (The two upstream jobs run in parallel, so this gate
-  # does not serialize publish behind test beyond their own completion.)
-  publish:
-    needs: [verify, test]
-    runs-on: ubuntu-latest
-    steps:
-      - uses: actions/checkout@v5
-      - uses: dtolnay/rust-toolchain@1.86.0
-      - uses: Swatinem/rust-cache@v2
-      # --no-verify: CI already compiled this exact commit (in the `test` job
-      # and on every push via ci.yml). cargo publish's default re-verify does a
-      # full cold release build of the packaged tarball, which here is pure
-      # redundant work (~a cold lib build). Skip it.
-      - name: Publish to crates.io
-        run: cargo publish --no-verify
-        env:
-          CARGO_REGISTRY_TOKEN: ${{ secrets.CARGO_REGISTRY_TOKEN }}
+  # NOTE: there is no crates.io publish job. libfreemkv is git-tag-only
+  # (`package.publish = false` — it git-deps the firmware crate freemkv-unlock,
+  # which never ships to crates.io). Every consumer git-tag-pins libfreemkv via
+  # a committed [patch.crates-io]; the git tag itself IS the release artifact.
+  # A `cargo publish` here fails hard on `publish = false`, so it was removed.
 
   release:
     # Only needs `verify`; the GitHub Release can be cut as soon as the version

CHANGELOG.md

@@ -1,5 +1,173 @@
 # Changelog
 
+## [1.4.1] — 2026-07-14
+
+### Fixed
+
+- **Mux no longer discards good video over a single defective packet.** AACS
+  content decryption judged a 6144-byte aligned unit "undecryptable" unless
+  **every** content packet was conformant MPEG-TS. A single authored-bad packet
+  — a pressing/encoding defect, or an AACS 2.1 forensic-variant frame — made the
+  mux conceal the **whole** unit as NULL TS, destroying up to 31 of 32 good
+  packets and tallying them as loss. On discs carrying such packets this
+  surfaced as false "corruption" over large runs of otherwise-perfect video
+  (observed across two UHD titles: ~466 MB concealed, every unit decryptable).
+  The decrypt path now asks only *"did a key OPEN this unit?"* — a padding-aware
+  **≥75% supermajority** of content packets restoring their `0x47` sync, a gate
+  no wrong key can reach (uniform-AES noise floor ≈ 256⁻ⁿ) yet one that tolerates
+  a minority of authored-bad packets. Opened units pass through **verbatim**; a
+  non-conforming packet is left for the demuxer to drop on sync-loss and resync
+  past — TS-sync conformance is a muxer concern, never a decryption verdict. The
+  read/decrypt path no longer rewrites content bytes. The post-read verify/sweep
+  gate now shares the exact same primitive (`decrypt_unit` for TS), so verify can
+  never disagree with the mux decrypt and never false-marks a defect unit as a
+  bad read.
+- **MVC (Blu-ray 3D) track signals unified and hardened.** The `mvcC`
+  `CodecPrivate` extension, the `BlockAdditionMapping`, and each frame's
+  `BlockAdditional` now all derive from a single `MVCDecoderConfigurationRecord`
+  built once per track, so they can no longer diverge. A track is flagged 3D
+  only when that record actually builds — a malformed dependent-view parameter
+  set no longer emits a mapping with no matching record (previously the flag was
+  taken from `mvc_params.is_some()`, which could orphan a `BlockAddID`). The base
+  track's `CodecPrivate` now carries the `mvcC` extension block
+  (`avcC ‖ u32be(size) ‖ "mvcC" ‖ record`, Matroska-spec size = block − 4) so
+  players and mediainfo detect MVC at the track level.
+
+## [1.4.0] — 2026-07-13
+
+### Added
+
+- **Blu-ray 3D (MVC) support.** A 3D disc now rips to an MKV that preserves
+  **both eyes** as a single MVC video track — the AVC base (left) view in each
+  Block, and the MVC dependent (right-eye) view as a per-frame `BlockAdditional`
+  under an `mvcC` `BlockAdditionMapping` (`MVCDecoderConfigurationRecord` per
+  ISO/IEC 14496-15 §7.6.2), paired to the base by PTS. Remux only — no
+  transcode, no side-by-side conversion. The Blu-ray scan reads the interleaved
+  `STREAM/SSIF/<clip>.ssif`, enumerates the dependent view (stream_type `0x20`)
+  by the BD-3D PID convention, and parses it in a parameter-set-passthrough mode
+  so every dependent frame is a self-contained access unit. Verified on
+  *300: Rise of an Empire*: one MVC track, ~8.7 GB dependent payload carried in
+  per-frame BlockAdditionals, base view byte-identical to the 2D rip.
+
+## [1.3.2] — 2026-07-10
+
+### Added
+
+- **AACS 2.1 (FMTS) variant-decode foundation.** `UnitKey` gains a
+  `variant_number` field (`0` = ordinary content, `1..=32` = a forensic
+  variant) with `UnitKey::new` / `UnitKey::variant` constructors, and a new
+  `aacs::variant_select` module resolves a disc's single forensic variant and
+  classifies each aligned unit — decrypt with the default key, decrypt with the
+  variant key, drop a foreign variant, or conceal a keyless forensic unit. This
+  is the groundwork for selecting one variant's segments and dropping the other
+  31; the decrypt-pipeline wiring lands with the variant key source.
+
+### Fixed
+
+- **`IndividualSegment.tbl`: the per-record field is the variant, not a segment
+  number.** `Segment.number` → `Segment.variant`. Verified against a retail 2.1
+  disc, the field cycles `1..=32` across the table (a per-variant tag) rather
+  than counting up, so variant selection routes on the correct value.
+
+## [1.3.1] — 2026-07-10
+
+### Licensing
+
+- **Relicensed to the MIT License, from 1.3.1 onwards** (releases up to and
+  including 1.3.0 remain under AGPL-3.0).
+
+### Added
+
+- **Authoritative HD-DVD title composition** from the Advanced-Content playlist
+  (`ADV_OBJ/VPLST000.XPL`): each title's clips, real duration, display name, and
+  chapters come from the disc's own playlist instead of a clip-name heuristic. A
+  layer-break split (`FEATURE_1`+`FEATURE_2`, `feature`/`feature_Divide`) composes
+  into ONE title with the two parts as clips and their title-time offsets. Falls
+  back to the clip-name heuristic when no playlist is present.
+
+## [1.3.0] — 2026-07-08
+
+### Added
+
+- **AACS 2.1 (FMTS) is a first-class disc format.** FMTS discs are detected,
+  labeled, and scanned as their own format rather than misread as plain UHD. The
+  forensic variant segments are located from `IndividualSegment.tbl` and the
+  `SegmentKey.tbl` container is parsed; the bulk of the title decrypts with the
+  unit key as usual, and the forensic segments (for which no segment-key source
+  exists yet) are skipped as expected loss, so a 2.1 disc rips mostly-complete
+  instead of failing outright.
+- **AACS 2.1 variant Media Key chain runs end to end.** The variant media key is
+  derived as a clean Processing-Key to media-key primitive, with the record
+  layout pinned against reference variant MKBs — the per-slot `C` block from the
+  `0x0c` cvalue table, the `VARIANTS` table plus trailing nonce at `0x2d`, and
+  `VKD` at `0x2f` — so a genuine variant MKB resolves through the ladder.
+- **Partial HD-DVD support.** HD-DVD is detected as its own format and its
+  `HVDVD_TS` `.evo` clips mux through the pipeline: EVO video is demuxed from the
+  MPEG program stream, including VC-1 titles carried on extended stream id `0xFD`
+  (real selector in the PES `stream_id_extension`), with the VC-1 access units
+  reframed so each I-frame keeps its preceding sequence and entry-point headers.
+  Title composition is heuristic for now (authoritative program-chain parsing is
+  planned), so a disc that authors two distinct features under the layer-break
+  naming may present them as one title.
+- **Display-order timestamps for program-stream H.264 / VC-1 / HEVC.** A program
+  stream stamps a PES PTS only once per GOP; the parsers now reconstruct a
+  display-order PTS per frame from the coded picture type and the sparse anchor
+  (duration self-calibrated from anchor spacing), so a decoder no longer sees
+  colliding DTS. Gated to the program-stream path — the BD/UHD transport path
+  (per-frame PTS) is unchanged.
+- **Stream-label parsers: reader-backed detection and a menu-language fallback.**
+  Label detection can inspect a jar's contents, so vendor parsers claim only
+  their own discs; a new last-resort parser reads menu-artwork languages.
+- **keydb round-trips AACS 2.0 host certs** (the `HC2` line) so a load/save cycle
+  no longer drops v2 host credentials.
+
+### Changed
+
+- **MPEG-2 reassembles through the shared `AuAssembler`.** The MPEG-2 parser's
+  hand-rolled PES buffer and offset-keyed mark queues are replaced by the same
+  access-unit assembler the H.264/HEVC/VC-1 parsers use (in a new MPEG-2 mode);
+  the GOP-buffered `temporal_reference` reorder and PTS origin-locking are
+  unchanged, so DVD output is identical.
+- **Generic per-scheme recovery seam.** Decrypt-miss handling is now a
+  scheme-neutral seam the input stream installs (no recovery, or an AACS
+  fresh-key fetch), with CSS self-recovering separately from the data itself. An
+  undecryptable unit is counted the same whatever the scheme, so the separate
+  "undecryptable" loss bucket folds into one loss count.
+- **`aacs` module reorganized.** The former god-module is split into
+  `media_key` / `volume_key` / `inf` / `resolve` / `mkb` / `crypto` / `content`,
+  the `boil` veneer is removed, and module paths (not a `mod.rs` facade) are the
+  public API.
+
+### Fixed
+
+- **Main title is chosen by largest physical size, not clip count**, so a
+  chapter-per-clip disc (e.g. Fast & Furious) is no longer mis-ranked behind a
+  virtual composite.
+- **A fresh-rip ISO `sync_all` failure is no longer swallowed**: `is_regular` is
+  read from the open file handle instead of a pre-create `metadata(path)` that
+  always failed on a path that does not exist yet.
+- **A transient CLIP-info parse failure no longer suppresses a clip's extents**
+  for a later playlist item that references the same clip.
+- **Reverify downgrades that fail to persist are logged, not swallowed**, so a
+  bad unit cannot be silently mismarked good on resume.
+- **The CLI sanitizes on-disc metadata** (title, volume label, playlist, stream
+  labels) before printing, so a crafted disc cannot inject terminal escape
+  sequences.
+- **keydb entry validation matches the parser exactly** — a `0x` line counts only
+  with a ` = ` — so content that parses to zero usable entries can no longer be
+  saved as valid.
+- **autorip** recovers a poisoned config lock in the rip thread instead of
+  panicking it, and corrects the resume pass count.
+- Criterion stream numbering (a map value of 0 no longer shadows stream 1); AACS
+  resolve classifies a media-keys-only source missing the VID as "VID
+  unavailable"; a dropped partial PES flags a discontinuity; the no-demuxer path
+  detects an early consumer disconnect.
+
+### Performance
+
+- **Decrypt thread count is resolved once** and cached off the per-buffer hot
+  path (the env var and `available_parallelism` are no longer probed per call).
+
 ## [1.2.2] — 2026-07-04
 
 ### Added
@@ -39,7 +207,7 @@
 
 - **Processing-Key resolution is ~15× faster on UHD.** A Processing Key is the
   key at its subset-difference node (one AES-G from the Media Key), so it is now
-  tried directly against the MKB cvalue tables (matching libaacs `_calc_mk_pks`)
+  tried directly against the MKB cvalue tables (direct PK × cvalue iteration)
   instead of BFS-walking the SD tree at unknown depth — which was both wrong for
   terminal PKs and slow on a large UHD MKB (~181k cvalues). PK derivation on UHD
   drops from ~37 s to ~2.4 s; the SD tree walk now lives solely in the device-key
@@ -272,7 +440,7 @@ consumers are the in-tree toolchain crates.
 
 - **Post-read decrypt-verify gate.** Every AACS unit read off the disc is now
   buffered, re-aligned to its clip-file 6144-byte unit grid, and verified
-  (CPI flag → decrypt → strict all-32 TS-sync, matching libaacs `_verify_ts`)
+  (CPI flag → decrypt → strict all-32 TS-sync)
   before it is signed off as good. A unit that no held or freshly-fetched key
   decrypts is treated exactly like a bad read — re-read by
   the patch pass, terminal loss only if truly unrecoverable — closing the
@@ -293,7 +461,7 @@ consumers are the in-tree toolchain crates.
 
 - **AACS decrypt acceptance is now standards-strict.** A key is accepted only
   when the decrypted unit has the TS sync byte on *all* 32 source packets
-  (libaacs `_verify_ts`), replacing a majority-vote heuristic where a wrong key
+  (all-32 TS-sync verify), replacing a majority-vote heuristic where a wrong key
   could coincidentally restore enough syncs to pass and silently corrupt a unit.
 - keydb download/save moved out of the library into freemkv-keysources;
   libfreemkv no longer has any keydb I/O (it already held no keys).
@@ -301,7 +469,7 @@ consumers are the in-tree toolchain crates.
 ### Fixed
 
 - **AACS content-certificate bus-encryption flag read from the wrong bit.** The
-  flag is bit 7 of byte 1 (libaacs `p[1] >> 7`) but was read as bit 0, so a
+  flag is bit 7 of byte 1 (`p[1] >> 7`) but was read as bit 0, so a
   bus-encrypted disc parsed as *not* bus-encrypted — defeating the fail-loud
   guard that refuses to decrypt bus-wrapped data to garbage when no bus key was
   obtained. Also corrected the cc_id offset (byte 14) and the AACS2 type marker
@@ -601,7 +769,7 @@ hardening.
 
 - **Keyless DVD/CSS title-key recovery.** A CSS-protected DVD decrypts with no
   key database — the title key is recovered directly from the scrambled disc
-  data via the Stevenson known-plaintext attack (ported from libdvdcss) and
+  data via the Stevenson known-plaintext attack and
   validated by descrambling a sector and confirming the known plaintext
   reappears, so a wrong key fails cleanly instead of producing silent garbage
   (`src/css/stevenson.rs`). `Disc::scan_image` recovers the same title key from

CONTRIBUTING.md

@@ -24,4 +24,4 @@ cargo test
 
 ## License
 
-By contributing, you agree your code will be licensed under AGPL-3.0.
+By contributing, you agree your code will be licensed under MIT.

Cargo.toml

@@ -1,9 +1,9 @@
 [package]
 name = "libfreemkv"
-version = "1.2.2"
+version = "1.4.1"
 edition = "2024"
 rust-version = "1.86"
-license = "AGPL-3.0-only"
+license = "MIT"
 description = "Open source raw disc access library for optical drives"
 repository = "https://github.com/freemkv/libfreemkv"
 keywords = ["bluray", "uhd", "optical", "scsi", "disc"]
@@ -28,7 +28,7 @@ cbc = "0.1"
 # Interim path dep for local cross-repo dev; the release script re-pins this to
 # `{ git = ".../freemkv-unlock", tag = "vX.Y.Z" }` before tagging libfreemkv (so
 # the released tag resolves freemkv-unlock from git, not a sibling path).
-freemkv-unlock = { git = "https://github.com/freemkv/freemkv-unlock", tag = "v1.2.2" }
+freemkv-unlock = { git = "https://github.com/freemkv/freemkv-unlock", tag = "v1.4.1" }
 num-bigint = "0.4"
 num-traits = "0.2"
 num-integer = "0.1"
@@ -36,6 +36,12 @@ rand = "0.8"
 cmac = "0.7"
 zip = { version = "2", default-features = false, features = ["deflate"] }
 base64 = "0.22.1"
+# Read-only XML DOM parser (pure Rust, forbid(unsafe_code), entity-expansion
+# bounded). Parses the HD-DVD Advanced-Content playlist `ADV_OBJ/VPLST000.XPL`
+# — untrusted disc bytes — into authoritative titles/clips/chapters. A real
+# parser, not a hand-rolled scanner: the XPL is genuine XML (comments, varied
+# attribute order, self-closing tags).
+roxmltree = "0.20"
 # Trace-level instrumentation for Disc::copy + SgIoTransport::execute. Permitted
 # under CLAUDE.md ("Acceptable strings: debug/trace logging"). Consumers (autorip)
 # wire a tracing subscriber and pipe events into the JSONL debug log.

LICENSE

@@ -1,16 +1,21 @@
-GNU AFFERO GENERAL PUBLIC LICENSE
-Version 3, 19 November 2007
+MIT License
 
-Copyright (C) 2026 FreeMKV Contributors
+Copyright (c) 2026 Matthew Jackson & Contributors
 
-This program is free software: you can redistribute it and/or modify
-it under the terms of the GNU Affero General Public License as published
-by the Free Software Foundation, version 3 of the License.
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
 
-This program is distributed in the hope that it will be useful,
-but WITHOUT ANY WARRANTY; without even the implied warranty of
-MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
-GNU Affero General Public License for more details.
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
 
-You should have received a copy of the GNU Affero General Public License
-along with this program. If not, see <https://www.gnu.org/licenses/>.
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.

README.md

@@ -1,4 +1,4 @@
-[![License: AGPL-3.0](https://img.shields.io/badge/license-AGPL--3.0-blue)](LICENSE)
+[![License: MIT](https://img.shields.io/badge/license-MIT-blue)](LICENSE)
 
 # libfreemkv
 
@@ -190,4 +190,4 @@ Run `freemkv info disc:// --share` with the [freemkv CLI](https://github.com/fre
 
 ## License
 
-AGPL-3.0-only
+MIT

docs/architecture.md

@@ -7,7 +7,7 @@ AACS decryption requires an external `keydb.cfg` (default
 material is compiled in; DVD CSS player keys are the only compiled-in keys.
 
 **Repository:** <https://github.com/freemkv/libfreemkv>
-**License:** AGPL-3.0-only
+**License:** MIT
 
 ---
 

src/aacs/boil.rs

@@ -1,500 +0,0 @@
-//! AACS derivation "boil-down" — one public home for the key chain.
-//!
-//! Thin newtypes at the API boundary and three wrapper functions over the
-//! existing crypto. Nothing here re-implements a primitive: every function
-//! delegates to the already-audited code in [`super::keys`] and
-//! [`super::variants`], so the boil-down cannot drift from production math.
-//!
-//! The newtypes wrap bare `[u8; 16]` ONLY at this boundary — the crypto
-//! internals continue to operate on raw arrays. They exist so a caller threads
-//! the chain `DK → MK → VUK → UK` without confusing one 16-byte secret for
-//! another, not to refactor the resolver.
-//!
-//! Chain (matches `aacs::keys::resolve_keys_classical` path 1 and
-//! `aacs::keys::resolve_keys_v21` path 1 byte-for-byte):
-//!
-//! ```text
-//!   mk_from_dk(device_keys, mkb, vid)  →  MediaKey   (Km)
-//!   mk_from_pk(processing_keys, mkb)   →  MediaKey   (Km)
-//!   vuk_from_mk(MediaKey, Vid)         →  Vuk        (= AES-G(Km, VID))
-//!   uk_from_vuk(Vuk, enc_title_keys)   →  [UnitKey]  (decrypt_unit_key each)
-//! ```
-//!
-//! `mk_from_dk` and `mk_from_pk` are two entry points to the SAME Media Key,
-//! both via the MKB's Subset-Difference cvalue tables: the device-key path
-//! recovers its Processing Key at the matching SD node and walks on to the MK;
-//! the processing-key path starts from a precomputed PK. Neither needs a VID
-//! (the VID enters at `vuk_from_mk`).
-
-use super::keys::{
-    decrypt_unit_key, derive_media_key_and_pk_from_dk, derive_media_key_from_pk, derive_vuk,
-};
-use super::types::DeviceKey;
-
-/// Volume ID (16 bytes) — read from the disc via the SCSI handshake / OEM path.
-#[derive(Debug, Clone, Copy, PartialEq, Eq)]
-pub struct Vid(pub [u8; 16]);
-
-/// Media Key (Km, 16 bytes) — the MKB-scoped key derived from device keys.
-#[derive(Debug, Clone, Copy, PartialEq, Eq)]
-pub struct MediaKey(pub [u8; 16]);
-
-/// Volume Unique Key (VUK / Kvu, 16 bytes) — derived from `MediaKey` + `Vid`,
-/// decrypts the per-disc encrypted title keys in `Unit_Key_RO.inf`.
-#[derive(Debug, Clone, Copy, PartialEq, Eq)]
-pub struct Vuk(pub [u8; 16]);
-
-/// Processing Key (Kp, 16 bytes) — an MKB Subset-Difference key that yields the
-/// Media Key. A leaked/precomputed PK in the keydb, or the intermediate PK a
-/// device-key walk derives at its matching SD node.
-#[derive(Debug, Clone, Copy, PartialEq, Eq)]
-pub struct ProcessingKey(pub [u8; 16]);
-
-/// One decrypted per-CPS-unit AACS title key.
-///
-/// `idx` is the POSITIONAL index of the encrypted title key within the slice
-/// handed to [`uk_from_vuk`] (i.e. its order in `Unit_Key_RO.inf`'s key-storage
-/// area). The CPS-unit *number* association (the `u32` in
-/// `ResolvedKeys::unit_keys`) is a higher-level concern owned by
-/// [`super::keys::parse_unit_key_ro`], which pairs each positional key with its
-/// declared CPS unit; this primitive only does the AES, so it surfaces position.
-#[derive(Debug, Clone, Copy, PartialEq, Eq)]
-pub struct UnitKey {
-    pub idx: u32,
-    pub key: [u8; 16],
-}
-
-/// Derive the Volume Unique Key from a Media Key and Volume ID.
-///
-/// Wraps [`derive_vuk`] verbatim: `VUK = AES-128-ECB-DECRYPT(MK, VID) XOR VID`.
-/// This is byte-identical to the inline `derive_vuk(&mk, ctx.volume_id)` call in
-/// every classical resolver path AND to the `Kvu = AES-G(Km, VID)` step inside
-/// [`derive_media_key_variant`] (AES-G and `derive_vuk` are the same math), so
-/// `vuk_from_mk(mk_from_dk(..)?, vid)` reproduces the V21 variant VUK exactly.
-pub fn vuk_from_mk(mk: MediaKey, vid: Vid) -> Vuk {
-    Vuk(derive_vuk(&mk.0, &vid.0))
-}
-
-/// Decrypt the disc's encrypted title keys with a VUK.
-///
-/// Wraps [`decrypt_unit_key`] (AES-128-ECB-DECRYPT) per entry, mirroring the
-/// `derive_uks` closure in `resolve_keys_classical` / `resolve_keys_v21`. The
-/// returned `UnitKey::idx` is the slice position; pair with CPS-unit numbers via
-/// [`super::keys::parse_unit_key_ro`] when the numbering matters.
-pub fn uk_from_vuk(vuk: Vuk, enc_title_keys: &[[u8; 16]]) -> Vec<UnitKey> {
-    enc_title_keys
-        .iter()
-        .enumerate()
-        .map(|(i, enc)| UnitKey {
-            idx: i as u32,
-            key: decrypt_unit_key(&vuk.0, enc),
-        })
-        .collect()
-}
-
-/// Derive the Media Key (Km) from positioned device keys via the MKB's
-/// Subset-Difference tables.
-///
-/// Wraps [`derive_media_key_and_pk_from_dk`] — the real SD walk the resolver
-/// runs: each positioned device key is placed against the MKB's subset-diff /
-/// cvalue records, recovering its Processing Key at the matching node and
-/// continuing to the Media Key. Reachable for real discs whenever a device key
-/// applies to the MKB. No VID is involved here — it enters at [`vuk_from_mk`].
-///
-/// Returns [`Error::AacsMkUnavailable`] (E7018) when no supplied device key
-/// resolves the MKB — the same terminal error as [`mk_from_pk`]; no numeric
-/// distinction is load-bearing at this boundary.
-///
-/// [`Error::AacsMkUnavailable`]: crate::error::Error::AacsMkUnavailable
-pub fn mk_from_dk(device_keys: &[DeviceKey], mkb: &[u8]) -> Result<MediaKey, crate::error::Error> {
-    // Positioned device keys drive the real Subset-Difference MKB walk
-    // ([`derive_media_key_and_pk_from_dk`], the same walk the resolver runs). The
-    // old Media-Key-Variant path needed integrator Key Correction Data absent
-    // in-tree, so it Err'd for EVERY real disc (dead for both consumers —
-    // freemkv-keysources' DK fallback and the kdb harvester). No VID is needed
-    // for the Media Key; it enters only at [`vuk_from_mk`].
-    match derive_media_key_and_pk_from_dk(mkb, device_keys) {
-        Some((km, _pk)) => Ok(MediaKey(km)),
-        None => Err(crate::error::Error::AacsMkUnavailable),
-    }
-}
-
-/// Derive the Media Key (Km) from one or more Processing Keys and the disc MKB.
-///
-/// Wraps [`derive_media_key_from_pk`] — the Subset-Difference PK→MK walk: each
-/// processing key is validated (and tree-walked) against the MKB's cvalue tables
-/// (records `0x04`/`0x05`) until one yields the Media Key whose verify record
-/// (`0x81`/`0x86`) matches. Unlike [`mk_from_dk`] this path is reachable for
-/// real discs — a leaked/precomputed AACS Processing Key in the keydb resolves
-/// the Media Key directly. No VID is involved at this step; the VID enters at
-/// [`vuk_from_mk`].
-///
-/// Returns [`Error::AacsMkUnavailable`] (E7018) when no processing key resolves
-/// the MKB — the same terminal error as [`mk_from_dk`]; no numeric distinction
-/// is load-bearing at this boundary.
-///
-/// [`Error::AacsMkUnavailable`]: crate::error::Error::AacsMkUnavailable
-pub fn mk_from_pk(
-    processing_keys: &[[u8; 16]],
-    mkb: &[u8],
-) -> Result<MediaKey, crate::error::Error> {
-    match derive_media_key_from_pk(mkb, processing_keys) {
-        Some(km) => Ok(MediaKey(km)),
-        None => Err(crate::error::Error::AacsMkUnavailable),
-    }
-}
-
-/// A candidate key at any rung of the AACS ladder, handed to [`resolve_candidate`].
-///
-/// Each variant carries the module's existing newtype for that rung (a `Dk` is a
-/// POSITIONED [`DeviceKey`] — recover an unpositioned one with
-/// [`super::keys::recover_dk_position`] first).
-#[derive(Debug, Clone)]
-pub enum KeyCandidate {
-    Uk(UnitKey),
-    Vuk(Vuk),
-    Mk(MediaKey),
-    Pk(ProcessingKey),
-    Dk(DeviceKey),
-}
-
-/// The AACS key chain derived from a candidate, from [`resolve_candidate`].
-///
-/// PURE DERIVATION — no unit sampling, no validation. `unit_keys` holds every
-/// CPS-unit key the disc's `Unit_Key_RO.inf` yields from the VUK (positional
-/// order); the caller runs [`super::decrypt::unit_key_validates`] to find which
-/// one actually opens the disc. Rungs above the candidate are `None` (a `Vuk`
-/// candidate has no `mk`/`pk`/`dk`; a `Uk` candidate has only `unit_keys`).
-#[derive(Debug, Clone)]
-pub struct ResolvedChain {
-    /// Every unit key derived from the VUK, as `(cps_unit_number, key)` — the
-    /// CPS-unit numbers come from `Unit_Key_RO.inf` (via `parse_unit_key_ro`), so
-    /// a consumer maps `UK → CPS unit` directly. Same shape as
-    /// [`super::keys::ResolvedKeys::unit_keys`]. A `Uk` candidate yields exactly
-    /// itself, keyed by its own `idx`.
-    pub unit_keys: Vec<(u32, [u8; 16])>,
-    pub vuk: Option<Vuk>,
-    pub mk: Option<MediaKey>,
-    pub pk: Option<ProcessingKey>,
-    /// The positioned device key (for a `Dk` candidate).
-    pub dk: Option<DeviceKey>,
-}
-
-/// Derive the full AACS key chain from a candidate key of ANY ladder rung.
-///
-/// Runs the deterministic derivation DOWNWARD to the disc's terminal unit keys:
-/// `DK → MK → VUK → UKs`, `PK → MK → VUK → UKs`, `MK → VUK → UKs`,
-/// `VUK → UKs`, or `UK → itself`. Composes the module's own boil steps
-/// ([`mk_from_pk`], [`vuk_from_mk`], [`uk_from_vuk`]) and parses
-/// `Unit_Key_RO.inf` at the version the disc's MKB declares (48-byte stride for
-/// AACS-1.0, 64 for AACS-2.x), so a multi-CPS disc yields all its unit keys from
-/// the one candidate.
-///
-/// PURE DERIVATION: no sampling, no validation, no position recovery. Every step
-/// is deterministic AES, so the returned keys are only as sound as the input
-/// candidate — validate `unit_keys` against a real encrypted unit with
-/// [`super::decrypt::unit_key_validates`] to prove the candidate opens the disc.
-///
-/// Returns `None` only when derivation itself cannot proceed: a PK its MKB
-/// rejects, a `Dk` the MKB can't process, a missing VID on a path that needs
-/// one, or an unparseable/empty `Unit_Key_RO.inf`.
-pub fn resolve_candidate(
-    candidate: &KeyCandidate,
-    mkb: &[u8],
-    unit_key_ro: &[u8],
-    vid: Option<Vid>,
-) -> Option<ResolvedChain> {
-    use super::keys::{AacsVersion, derive_media_key_and_pk_from_dk, mkb_type, parse_unit_key_ro};
-
-    // Boil a VUK → all unit keys, each paired with its declared CPS-unit number.
-    // `.inf` parsing lives here: derive the stride version from the disc's own
-    // MKB, then defer the VUK→unit-keys step to the shared `derive_unit_keys`
-    // (the one place both resolvers and this path decrypt the title keys).
-    let boil = |vuk: Vuk| -> Option<Vec<(u32, [u8; 16])>> {
-        let version = mkb_type(mkb)
-            .map(|t| t.generation())
-            .unwrap_or(AacsVersion::V10);
-        let ukf = parse_unit_key_ro(unit_key_ro, version)?;
-        if ukf.encrypted_keys.is_empty() {
-            return None;
-        }
-        Some(super::keys::derive_unit_keys(&ukf, &vuk.0))
-    };
-
-    match candidate {
-        KeyCandidate::Uk(uk) => Some(ResolvedChain {
-            unit_keys: vec![(uk.idx, uk.key)],
-            vuk: None,
-            mk: None,
-            pk: None,
-            dk: None,
-        }),
-        KeyCandidate::Vuk(v) => Some(ResolvedChain {
-            unit_keys: boil(*v)?,
-            vuk: Some(*v),
-            mk: None,
-            pk: None,
-            dk: None,
-        }),
-        KeyCandidate::Mk(mk) => {
-            let vuk = vuk_from_mk(*mk, vid?);
-            Some(ResolvedChain {
-                unit_keys: boil(vuk)?,
-                vuk: Some(vuk),
-                mk: Some(*mk),
-                pk: None,
-                dk: None,
-            })
-        }
-        KeyCandidate::Pk(pk) => {
-            let mk = mk_from_pk(std::slice::from_ref(&pk.0), mkb).ok()?;
-            let vuk = vuk_from_mk(mk, vid?);
-            Some(ResolvedChain {
-                unit_keys: boil(vuk)?,
-                vuk: Some(vuk),
-                mk: Some(mk),
-                pk: Some(*pk),
-                dk: None,
-            })
-        }
-        KeyCandidate::Dk(dk) => {
-            let (km, pk) = derive_media_key_and_pk_from_dk(mkb, std::slice::from_ref(dk))?;
-            let mk = MediaKey(km);
-            let vuk = vuk_from_mk(mk, vid?);
-            Some(ResolvedChain {
-                unit_keys: boil(vuk)?,
-                vuk: Some(vuk),
-                mk: Some(mk),
-                pk: Some(ProcessingKey(pk)),
-                dk: Some(dk.clone()),
-            })
-        }
-    }
-}
-
-#[cfg(test)]
-mod tests {
-    use super::*;
-    use crate::aacs::decrypt::aes_ecb_encrypt;
-    use crate::aacs::keys::{decrypt_unit_key, derive_vuk};
-
-    /// `vuk_from_mk` must equal the inline `derive_vuk` path bit-for-bit, for
-    /// several known (MK, VID) vectors.
-    #[test]
-    fn vuk_from_mk_matches_inline_derive_vuk() {
-        let cases: [([u8; 16], [u8; 16]); 3] = [
-            ([0x5A; 16], [0xA5; 16]),
-            ([0x11; 16], [0x22; 16]),
-            (
-                [
-                    0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08, 0x09, 0x0A, 0x0B, 0x0C,
-                    0x0D, 0x0E, 0x0F,
-                ],
-                [
-                    0xF0, 0xE1, 0xD2, 0xC3, 0xB4, 0xA5, 0x96, 0x87, 0x78, 0x69, 0x5A, 0x4B, 0x3C,
-                    0x2D, 0x1E, 0x0F,
-                ],
-            ),
-        ];
-        for (mk, vid) in cases {
-            let inline = derive_vuk(&mk, &vid);
-            let boiled = vuk_from_mk(MediaKey(mk), Vid(vid));
-            assert_eq!(boiled.0, inline, "vuk_from_mk must equal derive_vuk");
-        }
-    }
-
-    /// `uk_from_vuk` must equal the inline `decrypt_unit_key` path bit-for-bit
-    /// and carry positional indices 0..n. Built by encrypting known plaintext
-    /// title keys under the VUK (the same primitive the resolver inverts).
-    #[test]
-    fn uk_from_vuk_matches_inline_decrypt_unit_key() {
-        let vuk = [0x5Au8; 16];
-        let plain_keys = [[0x11u8; 16], [0x22u8; 16], [0xCDu8; 16]];
-        let enc: Vec<[u8; 16]> = plain_keys
-            .iter()
-            .map(|k| aes_ecb_encrypt(&vuk, k))
-            .collect();
-
-        let boiled = uk_from_vuk(Vuk(vuk), &enc);
-        assert_eq!(boiled.len(), enc.len());
-        for (i, uk) in boiled.iter().enumerate() {
-            assert_eq!(uk.idx, i as u32, "idx must be the positional index");
-            // Matches the inline derive_uks closure: decrypt_unit_key(vuk, enc).
-            assert_eq!(uk.key, decrypt_unit_key(&vuk, &enc[i]));
-            // And recovers the original plaintext title key.
-            assert_eq!(
-                uk.key, plain_keys[i],
-                "VUK roundtrip recovers the title key"
-            );
-        }
-    }
-
-    /// `uk_from_vuk` on an empty slice yields no keys (no panic, no phantom idx).
-    #[test]
-    fn uk_from_vuk_empty_is_empty() {
-        assert!(uk_from_vuk(Vuk([0u8; 16]), &[]).is_empty());
-    }
-
-    /// `mk_from_dk` returns `Err(AacsMkUnavailable)` when the MKB has no
-    /// processable Subset-Difference tables (empty MKB, or one with no
-    /// mk_dv/cvalues/subdiff records) — never a wrong key, never a panic.
-    #[test]
-    fn mk_from_dk_errors_on_unprocessable_mkb() {
-        let dk = DeviceKey {
-            key: [0x11; 16],
-            node: 1,
-            uv: 1,
-            u_mask_shift: 0,
-        };
-        // Empty MKB → no SD records to walk → Err.
-        let e = mk_from_dk(std::slice::from_ref(&dk), &[]);
-        assert!(matches!(e, Err(crate::error::Error::AacsMkUnavailable)));
-
-        // An MKB with no complete Subset-Difference tables (mk_dv / cvalues /
-        // subdiff) cannot yield a Media Key, so the real walk also errors —
-        // never silently yields a key.
-        let mut mkb: Vec<u8> = Vec::new();
-        mkb.extend_from_slice(&[0x82, 0x00, 0x00, 0x14]); // stray data record only
-        mkb.extend_from_slice(&[0xAB; 16]);
-        let e2 = mk_from_dk(&[dk], &mkb);
-        assert!(matches!(e2, Err(crate::error::Error::AacsMkUnavailable)));
-    }
-
-    /// Build a 4-byte MKB record header (type + 3-byte big-endian total length,
-    /// header included) and append `body`. Mirrors the MKB record framing the
-    /// parser expects; no crypto.
-    fn mkb_record(rec_type: u8, body: &[u8]) -> Vec<u8> {
-        let total = 4 + body.len();
-        let mut rec = Vec::with_capacity(total);
-        rec.push(rec_type);
-        rec.push(((total >> 16) & 0xFF) as u8);
-        rec.push(((total >> 8) & 0xFF) as u8);
-        rec.push((total & 0xFF) as u8);
-        rec.extend_from_slice(body);
-        rec
-    }
-
-    /// `mk_from_pk` resolves a planted Processing Key against a synthetic MKB and
-    /// drives the FULL boil chain PK → MK → VUK → UK. The MKB is built with the
-    /// same (pk, cv, mk_dv, uv) construction the production SD walk validates, so
-    /// this proves a PK entry yields real Unit Keys — not just an `Ok`.
-    #[test]
-    fn mk_from_pk_drives_full_chain_to_uks() {
-        let pk: [u8; 16] = [
-            0x11, 0x22, 0x33, 0x44, 0x55, 0x66, 0x77, 0x88, 0x99, 0xAA, 0xBB, 0xCC, 0xDD, 0xEE,
-            0xFF, 0x00,
-        ];
-        let mk: [u8; 16] = [
-            0xA0, 0xA1, 0xA2, 0xA3, 0xA4, 0xA5, 0xA6, 0xA7, 0xA8, 0xA9, 0xAA, 0xAB, 0xAC, 0xAD,
-            0xAE, 0xAF,
-        ];
-        let uv: [u8; 4] = [0x00, 0x00, 0x04, 0x00];
-
-        // cv = AES-E(pk, mk_raw), where mk_raw is mk with the last-4-bytes-uv XOR
-        // pre-undone, so the validate step XORs uv back in and recovers mk.
-        let mut mk_raw = mk;
-        for a in 0..4 {
-            mk_raw[12 + a] ^= uv[a];
-        }
-        let cv = aes_ecb_encrypt(&pk, &mk_raw);
-
-        // mk_dv = AES-E(mk, magic||pad): AES-D(mk, mk_dv) starts with the AACS
-        // verify sentinel.
-        let mut vd = [0x11u8; 16];
-        vd[..8].copy_from_slice(&[0x01, 0x23, 0x45, 0x67, 0x89, 0xAB, 0xCD, 0xEF]);
-        let mk_dv = aes_ecb_encrypt(&mk, &vd);
-
-        // Synthetic MKB: type/version (0x10), verify record (0x86 = mk_dv),
-        // one-entry SD index (0x04 = [u_mask_shift=0][uv]), one-entry cvalue
-        // table (0x05 = cv).
-        let mut sd = vec![0u8];
-        sd.extend_from_slice(&uv);
-        let mut mkb = Vec::new();
-        mkb.extend_from_slice(&mkb_record(0x10, &[0, 0, 0, 0x20, 0, 0, 0, 0x52]));
-        mkb.extend_from_slice(&mkb_record(0x86, &mk_dv));
-        mkb.extend_from_slice(&mkb_record(0x04, &sd));
-        mkb.extend_from_slice(&mkb_record(0x05, &cv));
-
-        // PK → MK.
-        let got_mk = mk_from_pk(std::slice::from_ref(&pk), &mkb).expect("planted PK resolves MK");
-        assert_eq!(got_mk, MediaKey(mk), "mk_from_pk recovers the planted MK");
-
-        // MK → VUK → UK over an encrypted title key.
-        let vid = Vid([0x42u8; 16]);
-        let plain_uk = [0x7Eu8; 16];
-        let vuk = vuk_from_mk(got_mk, vid);
-        let enc = aes_ecb_encrypt(&vuk.0, &plain_uk);
-        let uks = uk_from_vuk(vuk, std::slice::from_ref(&enc));
-        assert_eq!(uks.len(), 1);
-        assert_eq!(uks[0].key, plain_uk, "PK chain recovers the title key");
-
-        // A corrupt PK resolves nothing.
-        let mut bad = pk;
-        bad[0] ^= 0xFF;
-        assert!(matches!(
-            mk_from_pk(std::slice::from_ref(&bad), &mkb),
-            Err(crate::error::Error::AacsMkUnavailable)
-        ));
-    }
-
-    /// Minimal AACS-1.0 (48-byte stride) `Unit_Key_RO.inf` with `n` encrypted
-    /// unit keys — `parse_unit_key_ro` numbers CPS units 1..=n.
-    fn synth_inf(encs: &[[u8; 16]]) -> Vec<u8> {
-        let uk_pos = 32usize;
-        let stride = 48usize;
-        let n = encs.len();
-        let total = uk_pos + 48 + n.saturating_sub(1) * stride + 16;
-        let mut inf = vec![0u8; total.max(20)];
-        inf[..4].copy_from_slice(&(uk_pos as u32).to_be_bytes());
-        inf[uk_pos..uk_pos + 2].copy_from_slice(&(n as u16).to_be_bytes());
-        for (i, k) in encs.iter().enumerate() {
-            let o = uk_pos + 48 + i * stride;
-            inf[o..o + 16].copy_from_slice(k);
-        }
-        inf
-    }
-
-    /// A VUK candidate boils to ALL the disc's unit keys, each paired with its
-    /// declared CPS-unit number, and each key equals the VUK-decrypt of its slot.
-    #[test]
-    fn resolve_candidate_vuk_returns_all_cps_units() {
-        let vuk = Vuk([0x33u8; 16]);
-        let encs = [[0x11u8; 16], [0x22u8; 16], [0x44u8; 16]];
-        let inf = synth_inf(&encs);
-        let r = resolve_candidate(&KeyCandidate::Vuk(vuk), &[], &inf, None).expect("vuk derives");
-        let cps: Vec<u32> = r.unit_keys.iter().map(|(c, _)| *c).collect();
-        assert_eq!(
-            cps,
-            vec![1, 2, 3],
-            "every CPS unit surfaced, numbered from the inf"
-        );
-        for ((_, key), enc) in r.unit_keys.iter().zip(encs.iter()) {
-            assert_eq!(
-                *key,
-                decrypt_unit_key(&vuk.0, enc),
-                "key = VUK-decrypt of its slot"
-            );
-        }
-        assert_eq!(r.vuk, Some(vuk));
-        assert!(r.mk.is_none() && r.pk.is_none() && r.dk.is_none());
-    }
-
-    /// A bare UK candidate is terminal — it returns itself keyed by its own idx.
-    #[test]
-    fn resolve_candidate_uk_is_itself() {
-        let uk = UnitKey {
-            idx: 2,
-            key: [0x9u8; 16],
-        };
-        let r = resolve_candidate(&KeyCandidate::Uk(uk), &[], &[], None).expect("uk is terminal");
-        assert_eq!(r.unit_keys, vec![(2, uk.key)]);
-        assert!(r.vuk.is_none() && r.mk.is_none());
-    }
-
-    /// MK/PK/DK paths derive the VUK from a VID; without one, derivation stops.
-    #[test]
-    fn resolve_candidate_mk_requires_vid() {
-        let r = resolve_candidate(&KeyCandidate::Mk(MediaKey([1u8; 16])), &[], &[], None);
-        assert!(r.is_none(), "MK path returns None without a VID");
-    }
-}

src/aacs/content.rs

@@ -1,16 +1,18 @@
-//! AACS content decryption — AES primitives, unit decryption, bus encryption.
+//! AACS content decryption — aligned-unit / bus decryption and TS verification.
+//! The low-level AES primitives it uses live in [`super::crypto`].
 
 use aes::Aes128;
-use aes::cipher::{BlockDecrypt, BlockEncrypt, KeyInit, generic_array::GenericArray};
+use aes::cipher::{BlockDecrypt, KeyInit, generic_array::GenericArray};
+
+use super::crypto::{aes_cbc_decrypt, aes_ecb_encrypt};
+// Available at module scope for this module's test fixtures (they reference
+// `super::AACS_IV` when building CBC ciphertext directly); test-only.
+#[cfg(test)]
+use super::crypto::AACS_IV;
 
 // ── AACS constants ──────────────────────────────────────────────────────────
 
-/// Fixed IV used by AACS for all AES-CBC operations.
-pub(crate) const AACS_IV: [u8; 16] = [
-    0x0B, 0xA0, 0xF8, 0xDD, 0xFE, 0xA6, 0x1F, 0xB3, 0xD8, 0xDF, 0x9F, 0x56, 0x6A, 0x05, 0x0F, 0x78,
-];
-
-/// Size of an AACS aligned unit (3 × 2048-byte sectors).
+/// Size of an AACS aligned unit (3 × 2048-byte sectors). [BD] §3.10.1.
 pub const ALIGNED_UNIT_LEN: usize = 6144;
 
 /// An AACS aligned unit spans this many 2048-byte sectors (3).
@@ -47,58 +49,6 @@ use crate::consts::BD_SOURCE_PACKET_BYTES;
 /// TS sync byte.
 const TS_SYNC: u8 = 0x47;
 
-// ── AES primitives ──────────────────────────────────────────────────────────
-
-/// AES-128-ECB encrypt a single 16-byte block.
-pub(crate) fn aes_ecb_encrypt(key: &[u8; 16], data: &[u8; 16]) -> [u8; 16] {
-    let cipher = Aes128::new(GenericArray::from_slice(key));
-    let mut block = GenericArray::clone_from_slice(data);
-    cipher.encrypt_block(&mut block);
-    let mut out = [0u8; 16];
-    out.copy_from_slice(&block);
-    out
-}
-
-/// AES-128-ECB decrypt a single 16-byte block.
-pub(crate) fn aes_ecb_decrypt(key: &[u8; 16], data: &[u8; 16]) -> [u8; 16] {
-    let cipher = Aes128::new(GenericArray::from_slice(key));
-    let mut block = GenericArray::clone_from_slice(data);
-    cipher.decrypt_block(&mut block);
-    let mut out = [0u8; 16];
-    out.copy_from_slice(&block);
-    out
-}
-
-/// AES-128-CBC decrypt in-place with the fixed AACS IV.
-///
-/// Precondition: `data.len()` is a multiple of 16. Any trailing partial
-/// block is silently ignored; all callers pass aligned regions (6128 and
-/// 2032 bytes), and the assert documents/enforces that contract.
-pub(crate) fn aes_cbc_decrypt(key: &[u8; 16], data: &mut [u8]) {
-    debug_assert!(
-        data.len() % 16 == 0,
-        "aes_cbc_decrypt requires a block-aligned slice"
-    );
-    let cipher = Aes128::new(GenericArray::from_slice(key));
-    let num_blocks = data.len() / 16;
-    // Process blocks in reverse to avoid clobbering ciphertext needed for XOR
-    for i in (0..num_blocks).rev() {
-        let offset = i * 16;
-        let prev = if i == 0 {
-            AACS_IV
-        } else {
-            let mut p = [0u8; 16];
-            p.copy_from_slice(&data[(i - 1) * 16..i * 16]);
-            p
-        };
-        let mut block = GenericArray::clone_from_slice(&data[offset..offset + 16]);
-        cipher.decrypt_block(&mut block);
-        for j in 0..16 {
-            data[offset + j] = block[j] ^ prev[j];
-        }
-    }
-}
-
 // ── Content decryption ──────────────────────────────────────────────────────
 
 /// True if a 6144-byte aligned unit's MPEG-TS sync structure is DESTROYED — it
@@ -127,14 +77,14 @@ pub fn ts_sync_destroyed(unit: &[u8]) -> bool {
 }
 
 /// The AUTHORITATIVE AACS "is this aligned unit encrypted?" signal — the Copy
-/// Permission Indicator (CPI) in the top 2 bits of byte 0. Byte 0 is the first
+/// Permission Indicator (CPI) in the top 2 bits of byte 0. [BD] §3.10.2. Byte 0 is the first
 /// byte of the first source packet's `TP_extra_header`, which AACS always leaves
 /// in the clear (the first 16 bytes of every unit are the unencrypted SEED). So
 /// this is readable WITHOUT a key:
 ///   * `(buf[0] & 0xC0) == 0` → CPI clear → the unit is plaintext; pass through.
 ///   * non-zero → bytes `16..6144` are AES-CBC encrypted; decrypt.
 ///
-/// This is exactly libaacs' test (`if (!(buf[0] & 0xc0)) return; /* clear */`)
+/// This is exactly the spec CPI test (`buf[0] & 0xc0 == 0` means clear)
 /// and is the spec-correct replacement for the [`ts_sync_destroyed`] byte
 /// heuristic. CRITICAL: it is only meaningful when `unit` is read at the correct
 /// clip-FILE-anchored boundary — byte 0 must be the real unit start. A
@@ -163,51 +113,68 @@ pub fn aacs_unit_needs_decrypt(unit: &[u8]) -> bool {
     aacs_unit_encrypted(unit) && ts_sync_destroyed(unit)
 }
 
-/// PADDING-AWARE "is this aligned unit STILL genuine ciphertext?" — the conceal-
-/// path twin of [`decrypt_unit`]'s acceptance criterion, run on the POST-decrypt
-/// bytes.
+/// The one canonical "did a key OPEN this unit?" signal — a padding-aware,
+/// defect-TOLERANT structural check on the POST-decrypt bytes.
 ///
-/// [`aacs_unit_needs_decrypt`] cannot answer this: it composes CPI with the
-/// MAJORITY-VOTE [`ts_sync_destroyed`] (`ts_sync_count <= total/2`). A
-/// successfully padding-aware-decrypted content-fragment TAIL unit (e.g. 11 of 32
-/// packets are real content, the other 21 source-zero padding) carries only 11 TS
-/// syncs after decrypt, so the majority vote calls it "destroyed" and
-/// `aacs_unit_needs_decrypt` returns true — even though the unit decrypted
-/// PERFECTLY. Concealing on that predicate overwrites the good decrypted tail with
-/// NULL-TS, silently discarding correct video (the bug this fixes; the 1.2.0
-/// fragment-tail fix in [`decrypt_unit`] must not be undone by the conceal loop).
+/// ARCHITECTURE (why this is the only TS-sync test the read/decrypt path may
+/// use): TS-sync presence is a *muxer* concern, not a decryption verdict. The
+/// read/decrypt path is not allowed to reject or conceal a unit just because a
+/// packet isn't conformant MPEG-TS — a non-conforming packet inside an otherwise
+/// perfectly-decrypted unit is an authoring/pressing defect (or an AACS 2.1
+/// forensic-variant frame), which the demuxer drops on sync-loss and resyncs
+/// past. The ONLY thing the decrypt path legitimately needs from TS structure is
+/// KEY SELECTION: "did this candidate key turn ciphertext back into MPEG-TS at
+/// all?" — used to pick among held keys (multi-CPS-unit discs) and to detect a
+/// genuinely-missing key. That is a coarse, all-or-nothing question, and this is
+/// its answer.
 ///
-/// The correct, padding-aware notion of "still ciphertext", checkable on the
-/// post-decrypt bytes, uses the SAME discriminator [`decrypt_unit`] uses:
-///   * A genuinely-FAILED unit was restored to on-disc ciphertext by
-///     `decrypt_unit_try_keys`/`decrypt_buf` → its packets are scrambled: a
-///     non-padding (non-zero payload) packet LACKS the `0x47` sync at offset 4.
-///   * A SUCCESSFULLY-decrypted unit (full OR padding-tail) → every non-zero
-///     (content) packet carries `0x47`; padding packets are all-zero.
+/// Verdict: the key opened the unit iff a SUPERMAJORITY (>= 75%) of the
+/// non-padding content packets carry their `0x47` TS sync. Rationale:
+///   * WRONG key → AES output is uniform random → each content packet carries
+///     `0x47` at offset 4 with probability 1/256 → ~0 synced. Reaching 75% by
+///     chance is cryptographically impossible (e.g. 17-of-22 ≈ 256^-17). So a
+///     wrong key can NEVER pass — no silent-corruption hole.
+///   * RIGHT key → every real content packet decrypts to clear TS. A handful of
+///     authored-bad packets (pressing defects / variant frames) legitimately
+///     lack `0x47`, but they are a small minority and MUST NOT reject the unit —
+///     the decrypted bytes (defects and all) pass through verbatim; the muxer
+///     handles the bad packets. This is the whole point: correctness of a
+///     *packet* is not a decryption verdict.
 ///
-/// So this is true iff `aacs_unit_encrypted` AND at least one 192-byte packet
-/// whose 188-byte payload (`[off+4..off+192]`) is NOT all-zero is missing its
-/// `0x47` sync at `off+4`. A full content unit (no zero-payload packets) reduces
-/// to the strict all-32 check, so the common cases are unchanged: a fully-clear /
-/// fully-decrypted unit is never flagged; a fully-ciphertext unit always is.
-pub fn aacs_unit_still_ciphertext(unit: &[u8]) -> bool {
-    if !aacs_unit_encrypted(unit) {
-        return false;
-    }
+/// Padding-aware: a 192-byte packet whose 188-byte payload is all-zero is source
+/// padding (or a NULL packet) and is excluded from the count, so a legitimate
+/// content-fragment TAIL (a few real packets + source-zero padding) is judged on
+/// its real packets only. A full content unit reduces to "nearly all 32 synced".
+pub fn unit_content_decrypted(unit: &[u8]) -> bool {
     const PKT: usize = BD_SOURCE_PACKET_BYTES; // 192
     let limit = ALIGNED_UNIT_LEN.min(unit.len());
+    let mut content = 0usize;
+    let mut synced = 0usize;
     let mut off = 0;
     while off + PKT <= limit {
-        // A packet whose 188-byte payload is all-zero is padding (source zeros) —
-        // excluded from the verdict, exactly as `decrypt_unit` excludes it. Any
-        // other (content) packet that lacks its TS sync is un-restored ciphertext.
+        // All-zero payload → padding / NULL packet → excluded from the verdict.
         let payload = &unit[off + 4..off + PKT];
-        if !payload.iter().all(|&b| b == 0) && unit[off + 4] != TS_SYNC {
-            return true;
+        if !payload.iter().all(|&b| b == 0) {
+            content += 1;
+            if unit[off + 4] == TS_SYNC {
+                synced += 1;
+            }
         }
         off += PKT;
     }
-    false
+    // No content packets (all padding) → trivially "opened". Otherwise require a
+    // >=75% supermajority of content packets restored — the wrong-key-proof gate.
+    content == 0 || synced * 4 >= content * 3
+}
+
+/// "Is this aligned unit STILL genuine ciphertext (no held key opened it)?" — the
+/// conceal-path twin of [`unit_content_decrypted`], run on the POST-decrypt
+/// bytes. True iff the unit is flagged encrypted (CPI set) AND no key opened it
+/// (below the supermajority-sync gate). A unit the right key opened — even one
+/// carrying a few defective packets — is NOT ciphertext and is never concealed;
+/// its bytes belong to the muxer.
+pub fn aacs_unit_still_ciphertext(unit: &[u8]) -> bool {
+    aacs_unit_encrypted(unit) && !unit_content_decrypted(unit)
 }
 
 /// Overwrite an aligned unit (6144 bytes) IN PLACE with valid NULL MPEG-TS
@@ -288,7 +255,7 @@ fn ts_syncs_intact(unit: &[u8]) -> bool {
 }
 
 /// STRICT, standards-correct "is this a clean MPEG-TS aligned unit?" check —
-/// byte-for-byte libaacs' `_verify_ts` (`aacs.c`): EVERY one of the 32 BD source
+/// the standards-correct all-32-sync verify: EVERY one of the 32 BD source
 /// packets (192-byte stride) must carry its TS sync `0x47` at offset 4; the first
 /// miss fails. This is the authoritative gate for the POST-READ verify stage,
 /// independent of (and not coupled to) `decrypt_unit`.
@@ -385,7 +352,10 @@ pub fn decrypt_unit(unit: &mut [u8], unit_key: &[u8; 16]) -> bool {
     }
 
     // Save original first 16 bytes (the plaintext seed / header) and derive the
-    // per-unit decrypt key (identical to `decrypt_unit_checked`).
+    // per-unit Block Key (identical to `decrypt_unit_checked`).
+    // Block Key = AES-128E(Kcu, seed) ⊕ seed  ([BD] §3.10.1 Fig 3-8, two-node
+    // construction: encrypt the clear seed under the CPS Unit Key, then XOR the
+    // seed back in — the trailing ⊕seed is load-bearing).
     let mut header = [0u8; 16];
     header.copy_from_slice(&unit[..16]);
     let derived = aes_ecb_encrypt(unit_key, &header);
@@ -393,22 +363,28 @@ pub fn decrypt_unit(unit: &mut [u8], unit_key: &[u8; 16]) -> bool {
     for i in 0..16 {
         decrypt_key[i] = derived[i] ^ header[i];
     }
+    // Final 6128 bytes of the aligned unit under the Block Key; first 16 = clear seed. [BD] §3.10.1.
     aes_cbc_decrypt(&decrypt_key, &mut unit[16..ALIGNED_UNIT_LEN]);
 
-    // Verify content packets; zero out padding packets (their decrypted bytes are
-    // garbage from AES-decrypting zeros, but the source was zero so a clean zero
-    // fill is lossless and gives the demux a tidy gap instead of garbage).
+    // Restore source-zero padding packets to zero (their decrypted bytes are
+    // garbage from AES-decrypting zeros, but the source WAS zero, so writing the
+    // true source back is faithful — not concealment — and gives the demux a tidy
+    // gap instead of AES noise). Content packets are left EXACTLY as decrypted:
+    // the read/decrypt path never rewrites content, so an authored-bad packet
+    // (no `0x47`) passes through verbatim for the muxer to drop.
     for (p, &is_pad) in pad.iter().enumerate().take(npkt) {
-        let off = p * PKT;
         if is_pad {
+            let off = p * PKT;
             for b in unit[off..off + PKT].iter_mut() {
                 *b = 0;
             }
-        } else if unit[off + 4] != TS_SYNC {
-            return false; // a real content packet failed → genuinely undecryptable
         }
     }
-    true
+    // KEY-SELECTION verdict only: did this key OPEN the unit (restore the TS
+    // structure of a supermajority of content packets)? A wrong key can't; the
+    // right key can even when a few content packets are authored-bad. This is NOT
+    // a per-packet conformance gate — that belongs to the muxer.
+    unit_content_decrypted(unit)
 }
 
 /// Decrypt an AACS aligned unit in place, accepting the key only when `accept`
@@ -583,7 +559,9 @@ pub fn decrypt_unit_full(
 
 #[cfg(test)]
 mod tests {
+    use super::super::crypto::aes_ecb_decrypt;
     use super::*;
+    use aes::cipher::BlockEncrypt; // test fixtures build ciphertext directly
 
     #[test]
     fn test_aes_ecb_roundtrip() {
@@ -926,6 +904,192 @@ mod tests {
         );
     }
 
+    // ── Defect-tolerant "did a key OPEN this unit?" verdict ─────────────────
+    //
+    // The Bourne-UHD bug: a commercial disc carries the odd authored-bad TS
+    // packet (a pressing/encoding defect, or an AACS 2.1 forensic-variant frame)
+    // — one non-conforming packet inside an otherwise perfectly-decrypted 6144
+    // unit. The OLD strict per-packet acceptance rejected the WHOLE unit over
+    // that single packet, so the mux concealed ~all of it as NULL and 21/22 good
+    // video packets were destroyed and tallied as loss ("false corruption").
+    // The read/decrypt path must instead ACCEPT the unit (the key opened it) and
+    // pass the defective packet through VERBATIM for the muxer to drop. TS-sync
+    // conformance is a muxer concern, never a decryption verdict.
+
+    /// Build a unit that decrypts to 32 content packets, with `defect_pkts`
+    /// marked authored-bad (a non-`0x47` at the sync position + non-zero payload
+    /// so they count as genuine content, not padding), encrypted under `key`.
+    fn unit_with_defects(key: &[u8; 16], defect_pkts: &[usize]) -> Vec<u8> {
+        let mut unit = clear_unit();
+        for &p in defect_pkts {
+            let off = p * BD_SOURCE_PACKET_BYTES;
+            unit[off + 4] = 0x80; // NOT a TS sync
+            unit[off + 5] = 0xAB; // non-zero payload => real content, not padding
+        }
+        aacs_encrypt_unit(&mut unit, key);
+        unit
+    }
+
+    /// A POST-DECRYPT-looking unit: `content` non-padding packets, `synced` of
+    /// them carrying `0x47`; the remaining packets are source-zero padding. CPI
+    /// (encrypted flag) set iff `cpi`. Feeds the key-independent predicates.
+    fn decrypted_shape(content: usize, synced: usize, cpi: bool) -> Vec<u8> {
+        let mut u = vec![0u8; ALIGNED_UNIT_LEN];
+        for p in 0..content {
+            let off = p * BD_SOURCE_PACKET_BYTES;
+            u[off + 5] = 0xAB; // non-zero payload => counted as content
+            u[off + 4] = if p < synced { TS_SYNC } else { 0x80 };
+        }
+        if cpi {
+            u[0] |= 0xC0;
+        }
+        u
+    }
+
+    #[test]
+    fn single_authored_bad_packet_still_decrypts_and_passes_verbatim() {
+        // 1 defective content packet in an otherwise-perfect unit (the real case).
+        let key = [0x5Au8; 16];
+        let mut unit = unit_with_defects(&key, &[17]);
+        assert!(
+            decrypt_unit(&mut unit, &key),
+            "31/32 content packets synced -> the key OPENED the unit"
+        );
+        let off = 17 * BD_SOURCE_PACKET_BYTES;
+        assert_eq!(
+            unit[off + 4],
+            0x80,
+            "defect packet's bytes pass through VERBATIM (no null-fill, no zeroing)"
+        );
+        assert_eq!(unit[off + 5], 0xAB, "defect payload untouched");
+        assert!(
+            !aacs_unit_still_ciphertext(&unit),
+            "an opened unit is NOT ciphertext -> the mux never conceals it"
+        );
+        for p in 0..32 {
+            if p == 17 {
+                continue;
+            }
+            assert_eq!(
+                unit[p * BD_SOURCE_PACKET_BYTES + 4],
+                TS_SYNC,
+                "every other packet restored its sync (pkt {p})"
+            );
+        }
+    }
+
+    #[test]
+    fn several_defect_packets_within_tolerance_still_decrypt() {
+        // Up to 25% authored-bad content packets are tolerated (opened + passed
+        // through); the muxer drops them.
+        let key = [0x33u8; 16];
+        let mut unit = unit_with_defects(&key, &[3, 9, 17, 24, 30]); // 5/32 ≈ 16%
+        assert!(
+            decrypt_unit(&mut unit, &key),
+            "27/32 synced (>=75%) -> opened"
+        );
+    }
+
+    #[test]
+    fn wrong_key_never_opens_a_unit() {
+        // A wrong key restores ~0 syncs -> far below the supermajority gate.
+        let key = [0x5Au8; 16];
+        let mut unit = clear_unit();
+        aacs_encrypt_unit(&mut unit, &key);
+        assert!(
+            !decrypt_unit(&mut unit, &[0x22u8; 16]),
+            "wrong key cannot open the unit"
+        );
+    }
+
+    #[test]
+    fn threshold_accepts_at_75pct_and_rejects_just_below() {
+        // 24/32 = exactly 75% opens; 23/32 does not.
+        assert!(unit_content_decrypted(&decrypted_shape(32, 24, false)));
+        assert!(!unit_content_decrypted(&decrypted_shape(32, 23, false)));
+    }
+
+    #[test]
+    fn still_ciphertext_tracks_the_open_verdict() {
+        // Fully clean -> opened, not ciphertext.
+        assert!(!aacs_unit_still_ciphertext(&decrypted_shape(32, 32, true)));
+        // One defect -> still opened, still not ciphertext.
+        assert!(!aacs_unit_still_ciphertext(&decrypted_shape(32, 31, true)));
+        // Wrong-key noise floor -> not opened -> ciphertext (concealable).
+        assert!(aacs_unit_still_ciphertext(&decrypted_shape(32, 3, true)));
+        // CPI-clear bytes are never "ciphertext" regardless of sync count.
+        assert!(!aacs_unit_still_ciphertext(&decrypted_shape(32, 0, false)));
+    }
+
+    #[test]
+    fn all_padding_unit_is_trivially_opened() {
+        // CPI set but every packet is source-zero padding: nothing to decrypt.
+        assert!(unit_content_decrypted(&decrypted_shape(0, 0, true)));
+        assert!(!aacs_unit_still_ciphertext(&decrypted_shape(0, 0, true)));
+    }
+
+    #[test]
+    fn defect_count_boundary_via_real_decrypt() {
+        // Pin the 75% gate on the REAL decrypt path (not just the predicate):
+        // 8/32 defects => 24 synced = exactly 75% => opens; 9/32 => 23 synced =>
+        // does NOT open. Packets 1.. avoid the clear-seed packet 0.
+        let key = [0x77u8; 16];
+        let eight: Vec<usize> = (1..9).collect();
+        let mut u_ok = unit_with_defects(&key, &eight);
+        assert!(
+            decrypt_unit(&mut u_ok, &key),
+            "8 defects (24/32 = 75%) -> opened"
+        );
+        let nine: Vec<usize> = (1..10).collect();
+        let mut u_no = unit_with_defects(&key, &nine);
+        assert!(
+            !decrypt_unit(&mut u_no, &key),
+            "9 defects (23/32 < 75%) -> NOT opened (too corrupt / wrong key)"
+        );
+    }
+
+    #[test]
+    fn small_content_units_keep_the_wrong_key_floor() {
+        // Tiny content units are where a coincidental wrong-key sync matters most.
+        // The gate stays strict enough that a single fluke can't "open" them.
+        assert!(unit_content_decrypted(&decrypted_shape(2, 2, false))); // 2/2 -> open
+        assert!(!unit_content_decrypted(&decrypted_shape(2, 1, false))); // 1/2 -> not
+        assert!(unit_content_decrypted(&decrypted_shape(4, 3, false))); // 3/4=75% -> open
+        assert!(!unit_content_decrypted(&decrypted_shape(4, 2, false))); // 2/4 -> not
+    }
+
+    #[test]
+    fn fragment_tail_padding_plus_one_defect_still_decrypts() {
+        // Both tolerances at once: source-zero padding tail EXCLUDED, and the one
+        // authored-bad packet in the real prefix TOLERATED. 20 real packets
+        // (pkt 5 defective) => 19/20 synced => opened; padding emitted as zeros.
+        let key = [0x5Au8; 16];
+        let mut unit = clear_unit();
+        let off = 5 * BD_SOURCE_PACKET_BYTES;
+        unit[off + 4] = 0x80; // defect inside the real content
+        unit[off + 5] = 0xAB;
+        for b in unit[20 * BD_SOURCE_PACKET_BYTES..].iter_mut() {
+            *b = 0; // source-zero padding tail (packets 20..32)
+        }
+        aacs_encrypt_unit(&mut unit, &key);
+        assert!(
+            decrypt_unit(&mut unit, &key),
+            "19/20 real packets synced + zero pad -> opened"
+        );
+        assert_eq!(
+            unit[off + 4],
+            0x80,
+            "the defect packet passes through verbatim"
+        );
+        for p in 20..32 {
+            let o = p * BD_SOURCE_PACKET_BYTES;
+            assert!(
+                unit[o..o + BD_SOURCE_PACKET_BYTES].iter().all(|&b| b == 0),
+                "padding pkt {p} emitted as clean zeros"
+            );
+        }
+    }
+
     #[test]
     fn wrong_key_full_unit_is_not_decryptable() {
         let mut unit = clear_unit();
@@ -1255,7 +1419,7 @@ mod tests {
 
     #[test]
     fn unit_is_clean_ts_is_strict_all_32_syncs() {
-        // Standards-correct gate (libaacs `_verify_ts`): EVERY one of the 32
+        // Standards-correct gate (all-32 TS syncs): EVERY one of the 32
         // packet syncs is required. A fully-synced clear unit passes.
         let clear = clear_unit();
         assert!(unit_is_clean_ts(&clear), "all-32-sync unit is clean");

src/aacs/crypto.rs

@@ -0,0 +1,102 @@
+//! AACS common cryptographic primitives — [C] Chapter 2 / §3.2.2.
+//!
+//! Source: `[C]` = AACS Introduction and Common Cryptographic Elements Book,
+//! Rev 0.953. The shared low-level building blocks — AES-128 ECB E/D, AES-G,
+//! the AES-G3 Triple Generator, AES-CBC decrypt — and their fixed constants
+//! (`iv0`, `s0`). Used by every AACS generation; relocated here so the
+//! primitives live in one place instead of being scattered across the
+//! content / keys / variant modules.
+
+use aes::Aes128;
+use aes::cipher::{BlockDecrypt, BlockEncrypt, KeyInit, generic_array::GenericArray};
+
+/// Fixed IV used by AACS for all AES-CBC operations. [C] §2.1.2 (default CBC IV, `iv0`).
+pub(crate) const AACS_IV: [u8; 16] = [
+    0x0B, 0xA0, 0xF8, 0xDD, 0xFE, 0xA6, 0x1F, 0xB3, 0xD8, 0xDF, 0x9F, 0x56, 0x6A, 0x05, 0x0F, 0x78,
+];
+
+/// AES-128-ECB encrypt a single 16-byte block. [C] §2.1.1 (`AES-128E`).
+pub(crate) fn aes_ecb_encrypt(key: &[u8; 16], data: &[u8; 16]) -> [u8; 16] {
+    let cipher = Aes128::new(GenericArray::from_slice(key));
+    let mut block = GenericArray::clone_from_slice(data);
+    cipher.encrypt_block(&mut block);
+    let mut out = [0u8; 16];
+    out.copy_from_slice(&block);
+    out
+}
+
+/// AES-128-ECB decrypt a single 16-byte block. [C] §2.1.1 (`AES-128D`).
+pub(crate) fn aes_ecb_decrypt(key: &[u8; 16], data: &[u8; 16]) -> [u8; 16] {
+    let cipher = Aes128::new(GenericArray::from_slice(key));
+    let mut block = GenericArray::clone_from_slice(data);
+    cipher.decrypt_block(&mut block);
+    let mut out = [0u8; 16];
+    out.copy_from_slice(&block);
+    out
+}
+
+/// AES-128-CBC decrypt in-place with the fixed AACS IV. [C] §2.1.2 (`AES-128CBCD`).
+///
+/// Precondition: `data.len()` is a multiple of 16. Any trailing partial
+/// block is silently ignored; all callers pass aligned regions (6128 and
+/// 2032 bytes), and the assert documents/enforces that contract.
+pub(crate) fn aes_cbc_decrypt(key: &[u8; 16], data: &mut [u8]) {
+    debug_assert!(
+        data.len() % 16 == 0,
+        "aes_cbc_decrypt requires a block-aligned slice"
+    );
+    let cipher = Aes128::new(GenericArray::from_slice(key));
+    let num_blocks = data.len() / 16;
+    // Process blocks in reverse to avoid clobbering ciphertext needed for XOR
+    for i in (0..num_blocks).rev() {
+        let offset = i * 16;
+        let prev = if i == 0 {
+            AACS_IV
+        } else {
+            let mut p = [0u8; 16];
+            p.copy_from_slice(&data[(i - 1) * 16..i * 16]);
+            p
+        };
+        let mut block = GenericArray::clone_from_slice(&data[offset..offset + 16]);
+        cipher.decrypt_block(&mut block);
+        for j in 0..16 {
+            data[offset + j] = block[j] ^ prev[j];
+        }
+    }
+}
+
+/// AES-G(x1, x2) = AES-128D(x1, x2) XOR x2. [C] §2.1.3 (note: uses AES-128**D**).
+///
+/// The Media Key Variant chain uses AES-G to derive both the variant
+/// number (`Kvn = AES-G(Kp, Nonce)`) and the Volume Unique Key
+/// (`Kvu = AES-G(Km, VID)`). See [`super::derive::derive_vuk`] for the
+/// classical VUK form — the math is identical, this exposes it as a
+/// neutral primitive for the variant chain.
+pub(crate) fn aes_g(x1: &[u8; 16], x2: &[u8; 16]) -> [u8; 16] {
+    let mut out = aes_ecb_decrypt(x1, x2);
+    for i in 0..16 {
+        out[i] ^= x2[i];
+    }
+    out
+}
+
+/// AACS-G3 seed constant (`s0`). [C] §3.2.2.
+pub(crate) const AESG3_SEED: [u8; 16] = [
+    0x7B, 0x10, 0x3C, 0x5D, 0xCB, 0x08, 0xC4, 0xE5, 0x1A, 0x27, 0xB0, 0x17, 0x99, 0x05, 0x3B, 0xD9,
+];
+
+/// AACS-G3: derive a subkey from a parent key. [C] §3.2.2 (Triple AES Generator:
+/// left=`D(k,s0)⊕s0` inc 0, pk=`D(k,s0+1)⊕(s0+1)` inc 1, right=`D(k,s0+2)⊕(s0+2)` inc 2).
+/// seed[15] += inc, then AES-DEC(key, seed) XOR seed.
+///
+/// Shared with [`super::variant`] (its variant chain runs the same SD
+/// tree); a single definition keeps the two walks byte-identical.
+pub(crate) fn aesg3(key: &[u8; 16], inc: u8) -> [u8; 16] {
+    let mut seed = AESG3_SEED;
+    seed[15] = seed[15].wrapping_add(inc);
+    let mut out = aes_ecb_decrypt(key, &seed);
+    for i in 0..16 {
+        out[i] ^= seed[i];
+    }
+    out
+}

src/aacs/derive.rs

@@ -0,0 +1,687 @@
+//! Media-key derivation: DK/PK → Media Key via the subset-difference tree.
+//! [C] §3.2.2–§3.2.5.
+
+use super::crypto::*;
+use super::inf::*;
+use super::mkb::*;
+use super::types::*;
+
+/// Derive Media Key from MKB data using processing keys.
+///
+/// A Processing Key is **terminal**: it is the key at its Subset-Difference
+/// node, one `AES-G` from the Media Key. So this is the fast path — each PK is
+/// tried *directly* against the MKB cvalue tables (no tree descent) — the
+/// direct PK × cvalue iteration. On a large AACS 2.x UHD MKB
+/// (~181k cvalues) this is ~15x faster than treating a PK as a device-node
+/// label and walking the tree.
+///
+/// If you hold a **device-node label** at unknown tree depth (not a terminal
+/// PK), derive its Media Key through the device-key path
+/// ([`derive_media_key_from_dk`]) — that path owns the Subset-Difference tree
+/// walk; the PK path never descends.
+///
+/// MKB format:
+///   Record type 0x10 = Type and Version Record (has MKB version)
+///   Record type 0x81 = Verify Media Key Record, AACS 1.0 (has mk_dv)
+///   Record type 0x86 = Verify Media Key Record, AACS 2.0/2.1 (has mk_dv)
+///   Record type 0x04 = Subset-Difference Index (has UVS entries)
+///   Record type 0x05 = Media Key Data Record (cvalues, 1:1 with 0x04)
+///   Record type 0x07 = Explicit Subset-Difference Record (NOT cvalues)
+pub fn derive_media_key_from_pk(mkb: &[u8], processing_keys: &[[u8; 16]]) -> Option<[u8; 16]> {
+    let mk_dv = mkb_find_mk_dv(mkb)?;
+    let uvs = mkb_find_subdiff_records(mkb)?;
+    let cvalues = mkb_find_cvalues(mkb)?;
+    try_pk_against_tables(processing_keys, &uvs, &cvalues, &mk_dv)
+}
+
+/// Core terminal-PK table scan over explicit record bodies. Each processing
+/// key is tried **directly** against every `(uv, cvalue)` pair — no tree
+/// descent. Reached in production via [`derive_media_key_from_pk`]; factored
+/// out so reproduction harnesses can drive it with explicit tables.
+pub(crate) fn try_pk_against_tables(
+    processing_keys: &[[u8; 16]],
+    uvs: &[u8],
+    cvalues: &[u8],
+    mk_dv: &[u8; 16],
+) -> Option<[u8; 16]> {
+    let num_uvs = uvs
+        .chunks(5)
+        .take_while(|c| c.len() == 5 && (c[0] & 0xC0) == 0)
+        .count();
+
+    for pk in processing_keys {
+        for i in 0..num_uvs {
+            if (i + 1) * 16 > cvalues.len() {
+                continue;
+            }
+            let record_start = i * 5;
+            if record_start + 5 > uvs.len() {
+                continue;
+            }
+            let uv = &uvs[record_start + 1..record_start + 5];
+            let cv = &cvalues[i * 16..(i + 1) * 16];
+            if let Some(mk) = validate_processing_key(pk, cv, uv, mk_dv) {
+                return Some(mk);
+            }
+        }
+    }
+    None
+}
+
+/// Validate a processing key against a cvalue/UV pair.
+/// Returns the Media Key if valid.
+///
+/// Steps (media key: [C] §3.2.4; verify relation: [C] §3.2.5.1.4):
+///   1. `mk = AES-128D(pk, cvalue)`                       [C] §3.2.4
+///   2. `mk[12..16] ^= uv` (4 bytes XOR into the last 4 bytes only)  [C] §3.2.4
+///   3. `dec_vd = AES-128D(mk, mk_dv)`                     [C] §3.2.5.1.4
+///   4. If `dec_vd[0..8] == 01 23 45 67 89 AB CD EF` → valid.  [C] §3.2.5.1.4
+pub(crate) fn validate_processing_key(
+    pk: &[u8; 16],
+    cvalue: &[u8],
+    uv: &[u8],
+    mk_dv: &[u8; 16],
+) -> Option<[u8; 16]> {
+    if cvalue.len() < 16 || uv.len() < 4 {
+        return None;
+    }
+
+    // Step 1: mk = AES-128D(pk, cvalue)
+    let mut cv = [0u8; 16];
+    cv.copy_from_slice(&cvalue[..16]);
+    let mut mk = aes_ecb_decrypt(pk, &cv);
+
+    // Step 2: XOR uv into the last 4 bytes of mk (mk[12..16]).
+    for a in 0..4 {
+        mk[12 + a] ^= uv[a];
+    }
+
+    // Step 3 + 4: dec_vd = AES-128D(mk, mk_dv); verify magic.
+    let dec_vd = aes_ecb_decrypt(&mk, mk_dv);
+    const VERIFY_MAGIC: [u8; 8] = [0x01, 0x23, 0x45, 0x67, 0x89, 0xAB, 0xCD, 0xEF];
+    if dec_vd[..8] == VERIFY_MAGIC {
+        return Some(mk);
+    }
+    None
+}
+
+/// Compute v_mask from a UV value. [C] §3.2.3. Shared with [`super::variant`].
+pub(super) fn calc_v_mask(uv: u32) -> u32 {
+    let mut v_mask: u32 = 0xFFFF_FFFF;
+    while (uv & !v_mask) == 0 && v_mask != 0 {
+        v_mask <<= 1;
+    }
+    v_mask
+}
+
+/// Derive processing key from device key using subset-difference tree traversal.
+/// [C] §3.2.4 (device-tree descent, MSB-branch, terminal PK). Shared with [`super::variant`].
+pub(super) fn calc_pk_from_dk(
+    dk: &[u8; 16],
+    uv: u32,
+    v_mask: u32,
+    dev_key_v_mask: u32,
+) -> [u8; 16] {
+    // Descend from the device node to the record node, following the record's
+    // `uv` bits. At each level only the child we descend INTO is needed (the
+    // sibling is computed but never used), and the Processing Key is the
+    // `aesg3(.,1)` of the FINAL node — so we derive ONE child per level and the
+    // PK once at the end, instead of left/pk/right at every level. Identical
+    // result, ~3x fewer block ops. (left child = `aesg3(node,0)`, right = `,2`.)
+    let mut node = *dk;
+    let mut current_v_mask = dev_key_v_mask;
+
+    // The subset-difference tree is at most 32 levels deep (u32 mask), so the
+    // walk must converge in <= 32 steps. The arithmetic `>> 1` sign-extends
+    // current_v_mask, so a v_mask coarser than dev_key_v_mask (reachable from
+    // a crafted/corrupt MKB) would otherwise saturate at 0xFFFF_FFFF and spin
+    // forever — bound the loop to keep a bad disc from hanging the rip thread.
+    let mut steps = 0u32;
+    while current_v_mask != v_mask {
+        if steps >= 32 {
+            break;
+        }
+        steps += 1;
+        // Find the highest unset bit in current_v_mask
+        let mut bit_pos: i32 = -1;
+        for i in (0..32).rev() {
+            if (current_v_mask & (1u32 << i)) == 0 {
+                bit_pos = i;
+                break;
+            }
+        }
+
+        let inc = if bit_pos < 0 || (uv & (1u32 << bit_pos as u32)) == 0 {
+            0 // left child
+        } else {
+            2 // right child
+        };
+        node = aesg3(&node, inc);
+
+        current_v_mask = ((current_v_mask as i32) >> 1) as u32;
+    }
+
+    aesg3(&node, 1)
+}
+
+/// Derive Media Key from MKB using device keys (subset-difference tree).
+///
+/// Thin wrapper over [`derive_media_key_and_pk_from_dk`] that drops the
+/// intermediate Processing Key. Callers that need the PK lineage (e.g.
+/// the key service banking DK·PK·MK) should call the `_and_pk_` form.
+pub fn derive_media_key_from_dk(mkb: &[u8], device_keys: &[DeviceKey]) -> Option<[u8; 16]> {
+    derive_media_key_and_pk_from_dk(mkb, device_keys).map(|(mk, _pk)| mk)
+}
+
+/// Derive both the Media Key and the intermediate Processing Key from an
+/// MKB using device keys (subset-difference tree).
+///
+/// Identical walk to [`derive_media_key_from_dk`]; this form additionally
+/// returns the Processing Key `Kp` derived at the matching subset-difference
+/// node — the value `calc_pk_from_dk` produces immediately before it
+/// validates into the Media Key. Returns `Some((mk, pk))` for the first DK
+/// that walks a uv slot whose Processing Key validates against the MKB.
+pub fn derive_media_key_and_pk_from_dk(
+    mkb: &[u8],
+    device_keys: &[DeviceKey],
+) -> Option<([u8; 16], [u8; 16])> {
+    let mk_dv = mkb_find_mk_dv(mkb)?;
+    let uvs = mkb_find_subdiff_records(mkb)?;
+    let cvalues = mkb_find_cvalues(mkb)?;
+
+    // Count UV entries
+    let num_uvs = uvs
+        .chunks(5)
+        .take_while(|c| c.len() == 5 && (c[0] & 0xC0) == 0)
+        .count();
+
+    for dk in device_keys {
+        let device_number = dk.node as u32;
+
+        // Find applying subset-difference for this device
+        for uvs_idx in 0..num_uvs {
+            let p_uv = &uvs[1 + 5 * uvs_idx..];
+            let u_mask_shift = uvs[5 * uvs_idx]; // byte before the UV value
+
+            // `num_uvs` was computed via `take_while(.. c[0] & 0xC0 == 0)`, so
+            // every iterated slot already has its revoked-marker bits clear — no
+            // inner `& 0xC0` re-check is needed (it would be unreachable).
+            //
+            // Shifts of 32..=63 (0x20..=0x3F) have those bits clear but would
+            // panic in debug / wrap to a wrong mask in release. The MKB byte is
+            // disc-controlled, so a crafted/corrupt MKB must not crash the ripper:
+            // skip an out-of-range slot rather than `<<` it.
+            if u_mask_shift >= 32 {
+                continue;
+            }
+
+            let uv = u32::from_be_bytes([p_uv[0], p_uv[1], p_uv[2], p_uv[3]]);
+            if uv == 0 {
+                continue;
+            }
+
+            // u-mask = shift count of low-order 0 bits ([C] §3.2.5.1.5); v-mask [C] §3.2.3.
+            let u_mask: u32 = 0xFFFF_FFFF << u_mask_shift;
+            let v_mask = calc_v_mask(uv);
+
+            // Subset-difference applies iff (d&mu)==(uv&mu) && (d&mv)!=(uv&mv). [C] §3.2.4.
+            if ((device_number & u_mask) == (uv & u_mask))
+                && ((device_number & v_mask) != (uv & v_mask))
+            {
+                // Found matching subset-difference — find the right device key.
+                // dk.u_mask_shift is a u8 from keydb with no range check;
+                // guard the shift the same way as the MKB byte above.
+                if dk.u_mask_shift >= 32 {
+                    continue;
+                }
+                let dev_key_v_mask = calc_v_mask(dk.uv);
+                let dev_key_u_mask: u32 = 0xFFFF_FFFF << dk.u_mask_shift;
+
+                if u_mask == dev_key_u_mask && (uv & dev_key_v_mask) == (dk.uv & dev_key_v_mask) {
+                    // Derive processing key via tree traversal
+                    let pk = calc_pk_from_dk(&dk.key, uv, v_mask, dev_key_v_mask);
+
+                    // Validate and derive media key
+                    if uvs_idx < cvalues.len() / 16 {
+                        let cv = &cvalues[uvs_idx * 16..(uvs_idx + 1) * 16];
+                        if let Some(mk) =
+                            validate_processing_key(&pk, cv, &uvs[1 + uvs_idx * 5..], &mk_dv)
+                        {
+                            return Some((mk, pk));
+                        }
+                    }
+                }
+            }
+        }
+    }
+    None
+}
+
+/// Recover the subset-difference position (`node`, `uv`, `u_mask_shift`) of an
+/// UNPOSITIONED device key by scanning a disc MKB. A device key alone (just the
+/// 16 bytes) cannot be walked — the walk needs its tree node. This finds that
+/// node empirically: for each MKB subset-difference record, it tries the device
+/// at the record's node AND at every ancestor v-position (the device may sit one
+/// or more levels ABOVE the record, descending via AES-G to reach it), deriving
+/// the candidate Processing Key DIRECTLY (one [`calc_pk_from_dk`] per candidate,
+/// no full re-walk) and checking it validates against that record's cvalue.
+///
+/// On the first verifying candidate it pins `(uv, u_mask_shift)` — invariant for
+/// the key across all discs — and resolves a gate-passing `node` (a one-time
+/// ≤32-try search at the single hit). Returns a [`DeviceKey`] ready to bank and
+/// reuse on every future disc via [`derive_media_key_from_dk`]. `None` if the
+/// key does not apply to this MKB.
+///
+/// Cost is `O(slots × tree_depth)` — linear in the MKB's subset-difference
+/// index, not the quartic cost of re-deriving per candidate.
+pub fn recover_dk_position(mkb: &[u8], key: &[u8; 16]) -> Option<DeviceKey> {
+    let mk_dv = mkb_find_mk_dv(mkb)?;
+    let uvs = mkb_find_subdiff_records(mkb)?;
+    let cvalues = mkb_find_cvalues(mkb)?;
+    let num_uvs = uvs
+        .chunks(5)
+        .take_while(|c| c.len() == 5 && (c[0] & 0xC0) == 0)
+        .count();
+    let n_cv = cvalues.len() / 16;
+
+    // Hoisted ONCE for the whole scan: the Processing Key the device produces if
+    // it sits EXACTLY at a record (zero descent) is `AES-G3(key, 1)` — it does
+    // not depend on the record, so the zero-descent probe of every slot reuses
+    // this single value instead of re-deriving it per slot.
+    let pk_zero_descent = aesg3(key, 1);
+
+    // The slots are independent, so the scan parallelises — a UHD MKB has ~181k
+    // slots (~26s single-threaded). `find_map_any` returns the first matching
+    // node found by any thread and cancels the rest; a valid MKB has exactly one
+    // matching subset-difference, so which thread finds it is immaterial.
+    use rayon::prelude::*;
+    let found = (0..num_uvs.min(n_cv)).into_par_iter().find_map_any(|i| {
+        let u_mask_shift = uvs[5 * i];
+        if u_mask_shift >= 32 {
+            return None;
+        }
+        let p_uv = &uvs[1 + 5 * i..];
+        let uv_r = u32::from_be_bytes([p_uv[0], p_uv[1], p_uv[2], p_uv[3]]);
+        if uv_r == 0 {
+            return None;
+        }
+        let v_mask = calc_v_mask(uv_r);
+        let cv = &cvalues[i * 16..(i + 1) * 16];
+        let uv_bytes = &uvs[1 + i * 5..];
+
+        // Zero descent (device sits at this slot's node): cheapest, most common.
+        if validate_processing_key(&pk_zero_descent, cv, uv_bytes, &mk_dv).is_some() {
+            return Some((uv_r, u_mask_shift));
+        }
+        // Descent: device is an ANCESTOR of the slot. Walk the depth bit up from
+        // the slot's lowest set bit; each level descends to the slot's node.
+        let p = uv_r.trailing_zeros();
+        for k in (p + 1)..32 {
+            let uv_d = if k + 1 >= 32 {
+                1u32 << k
+            } else {
+                (uv_r & (0xFFFF_FFFFu32 << (k + 1))) | (1u32 << k)
+            };
+            let pk = calc_pk_from_dk(key, uv_r, v_mask, calc_v_mask(uv_d));
+            if validate_processing_key(&pk, cv, uv_bytes, &mk_dv).is_some() {
+                return Some((uv_d, u_mask_shift));
+            }
+        }
+        None
+    });
+    found.and_then(|(uv, mask)| resolve_dk_node(mkb, key, uv, mask))
+}
+
+/// Resolve a positioned [`DeviceKey`] for an orphan `key` known to sit at
+/// `(uv, u_mask_shift)`: find a `device_number` (node) that passes the walk's
+/// subset-difference gate on `mkb`. The derived key is independent of the exact
+/// node (it only gates), so any gating node yields the same Media Key — a
+/// one-time ≤32-try search, run only once at the recovered position.
+pub(crate) fn resolve_dk_node(
+    mkb: &[u8],
+    key: &[u8; 16],
+    uv: u32,
+    u_mask_shift: u8,
+) -> Option<DeviceKey> {
+    for b in 0..u_mask_shift {
+        let dk = DeviceKey {
+            key: *key,
+            node: ((uv ^ (1u32 << b)) & 0xFFFF) as u16,
+            uv,
+            u_mask_shift,
+        };
+        if derive_media_key_from_dk(mkb, std::slice::from_ref(&dk)).is_some() {
+            return Some(dk);
+        }
+    }
+    // Degenerate MKB (no gating bit): fall back to the node itself.
+    Some(DeviceKey {
+        key: *key,
+        node: (uv & 0xFFFF) as u16,
+        uv,
+        u_mask_shift,
+    })
+}
+
+/// Public, side-effect-free accessors over the MKB record helpers, exposed so
+/// independent reproduction harnesses (e.g. `examples/prove_hkd_aacs.rs`) can
+/// exercise the exact same parser + verify primitives the production walk uses.
+/// These are thin wrappers — no new logic.
+#[doc(hidden)]
+pub mod probe {
+    use super::super::crypto::aes_ecb_decrypt;
+
+    /// `mk_dv` from the MKB's Verify-Media-Key record (type 0x81 / 0x86).
+    pub fn mkb_mk_dv(mkb: &[u8]) -> Option<[u8; 16]> {
+        super::mkb_find_mk_dv(mkb)
+    }
+
+    /// Body of the MKB's Subset-Difference Index record (type 0x04).
+    pub fn mkb_subdiff(mkb: &[u8]) -> Option<Vec<u8>> {
+        super::mkb_find_subdiff_records(mkb)
+    }
+
+    /// Body of the MKB's Media-Key-Data (cvalues) record. Selects record
+    /// `0x05` (the large cvalue table, 1:1 with the `0x04` Subset-Difference
+    /// index on AACS 2.x UHD MKBs), falling back to `0x07` only when `0x05`
+    /// is absent.
+    pub fn mkb_cvalues(mkb: &[u8]) -> Option<Vec<u8>> {
+        super::mkb_find_cvalues(mkb)
+    }
+
+    /// Body (header stripped) of the first MKB record of `rec_type`. Lets a
+    /// harness pin an exact record type for cross-checking the production
+    /// cvalue selection (e.g. compare record `0x05` vs `0x07` sizes).
+    pub fn mkb_record_body(mkb: &[u8], rec_type: u8) -> Option<Vec<u8>> {
+        super::find_record_body(mkb, rec_type)
+    }
+
+    /// AES-128-ECB single-block decrypt (the AACS verify primitive).
+    pub fn aes_dec(key: &[u8; 16], block: &[u8; 16]) -> [u8; 16] {
+        aes_ecb_decrypt(key, block)
+    }
+
+    /// Does `km` satisfy the MKB's Verify-Media-Key relation?
+    /// `AES-D(km, mk_dv)[0..8] == 01 23 45 67 89 AB CD EF`.
+    pub fn km_verifies(mkb: &[u8], km: &[u8; 16]) -> bool {
+        match super::mkb_find_mk_dv(mkb) {
+            Some(mk_dv) => {
+                aes_ecb_decrypt(km, &mk_dv)[..8] == [0x01, 0x23, 0x45, 0x67, 0x89, 0xAB, 0xCD, 0xEF]
+            }
+            None => false,
+        }
+    }
+}
+
+// ── Volume key: Media Key + Volume ID → VUK → unit keys ──────────────────────
+
+/// Derive VUK from Media Key and Volume ID. [PR] §3.3 / [BD] §3.3
+/// (`Kvu = AES-G(Km, IDv)`; AES-G uses AES-128D):
+/// VUK = AES-128-ECB-DECRYPT(media_key, volume_id) XOR volume_id
+pub fn derive_vuk(media_key: &[u8; 16], volume_id: &[u8; 16]) -> [u8; 16] {
+    let mut vuk = aes_ecb_decrypt(media_key, volume_id);
+    for i in 0..16 {
+        vuk[i] ^= volume_id[i];
+    }
+    vuk
+}
+
+/// Decrypt an encrypted unit key using the VUK (AES-128-ECB). [PR] §3.5
+/// (Title Key unwrap `Kt = AES-128D(Ku, Kte)`); the BD "CPS Unit Key" synonym is [BD] §3.9.3.
+pub fn decrypt_unit_key(vuk: &[u8; 16], encrypted_uk: &[u8; 16]) -> [u8; 16] {
+    aes_ecb_decrypt(vuk, encrypted_uk)
+}
+
+/// Decrypt every encrypted unit key in a parsed `Unit_Key_RO.inf` with a VUK,
+/// paired with its declared CPS-unit number. THE single VUK→unit-keys step:
+/// both classical/v21 resolvers and [`resolve_candidate`] call this, so the
+/// map cannot drift between the player and harvest paths.
+pub(crate) fn derive_unit_keys(uk_file: &UnitKeyFile, vuk: &[u8; 16]) -> Vec<(u32, [u8; 16])> {
+    uk_file
+        .encrypted_keys
+        .iter()
+        .map(|(num, enc_key)| (*num, decrypt_unit_key(vuk, enc_key)))
+        .collect()
+}
+
+/// A candidate key at any rung of the AACS ladder, handed to [`resolve_candidate`].
+///
+/// Each variant carries the [`super::types`] newtype for that rung (a `Dk` is a
+/// POSITIONED [`DeviceKey`] — recover an unpositioned one with
+/// [`recover_dk_position`] first).
+#[derive(Debug, Clone)]
+pub enum KeyCandidate {
+    Uk(UnitKey),
+    Vuk(Vuk),
+    Mk(MediaKey),
+    Pk(ProcessingKey),
+    Dk(DeviceKey),
+}
+
+/// The AACS key chain derived from a candidate, from [`resolve_candidate`].
+///
+/// PURE DERIVATION — no unit sampling, no validation. `unit_keys` holds every
+/// CPS-unit key the disc's `Unit_Key_RO.inf` yields from the VUK (paired with
+/// its declared CPS-unit number); the caller runs
+/// [`super::content::unit_key_validates`] to find which one actually opens the
+/// disc. Rungs above the candidate are `None`.
+#[derive(Debug, Clone)]
+pub struct ResolvedChain {
+    pub unit_keys: Vec<(u32, [u8; 16])>,
+    pub vuk: Option<Vuk>,
+    pub mk: Option<MediaKey>,
+    pub pk: Option<ProcessingKey>,
+    /// The positioned device key (for a `Dk` candidate).
+    pub dk: Option<DeviceKey>,
+}
+
+/// Derive the full AACS key chain from a candidate key of ANY ladder rung.
+///
+/// Runs the deterministic derivation DOWNWARD to the disc's terminal unit keys:
+/// `DK → MK → VUK → UKs`, `PK → MK → VUK → UKs`, `MK → VUK → UKs`,
+/// `VUK → UKs`, or `UK → itself`. Composes the raw derivation primitives
+/// ([`derive_media_key_from_pk`], [`derive_media_key_and_pk_from_dk`],
+/// [`derive_vuk`], [`derive_unit_keys`]) and parses `Unit_Key_RO.inf` at the
+/// version the disc's MKB declares, so a multi-CPS disc yields all its unit
+/// keys from the one candidate.
+///
+/// PURE DERIVATION: no sampling, no validation, no position recovery. Validate
+/// `unit_keys` against a real encrypted unit with
+/// [`super::content::unit_key_validates`] to prove the candidate opens the disc.
+///
+/// Returns `None` only when derivation itself cannot proceed: a PK its MKB
+/// rejects, a `Dk` the MKB can't process, a missing VID on a path that needs
+/// one, or an unparseable/empty `Unit_Key_RO.inf`.
+pub fn resolve_candidate(
+    candidate: &KeyCandidate,
+    mkb: &[u8],
+    unit_key_ro: &[u8],
+    vid: Option<Vid>,
+) -> Option<ResolvedChain> {
+    // Boil a VUK → all unit keys, each paired with its declared CPS-unit number.
+    // Derive the stride version from the disc's own MKB, then defer to the shared
+    // `derive_unit_keys` (the one place both resolvers and this path decrypt).
+    let boil = |vuk: Vuk| -> Option<Vec<(u32, [u8; 16])>> {
+        let version = mkb_type(mkb)
+            .map(|t| t.generation())
+            .unwrap_or(AacsVersion::V10);
+        let ukf = parse_unit_key_ro(unit_key_ro, version)?;
+        if ukf.encrypted_keys.is_empty() {
+            return None;
+        }
+        Some(derive_unit_keys(&ukf, &vuk.0))
+    };
+
+    match candidate {
+        KeyCandidate::Uk(uk) => Some(ResolvedChain {
+            unit_keys: vec![(uk.idx, uk.key)],
+            vuk: None,
+            mk: None,
+            pk: None,
+            dk: None,
+        }),
+        KeyCandidate::Vuk(v) => Some(ResolvedChain {
+            unit_keys: boil(*v)?,
+            vuk: Some(*v),
+            mk: None,
+            pk: None,
+            dk: None,
+        }),
+        KeyCandidate::Mk(mk) => {
+            let vuk = Vuk(derive_vuk(&mk.0, &vid?.0));
+            Some(ResolvedChain {
+                unit_keys: boil(vuk)?,
+                vuk: Some(vuk),
+                mk: Some(*mk),
+                pk: None,
+                dk: None,
+            })
+        }
+        KeyCandidate::Pk(pk) => {
+            let km = derive_media_key_from_pk(mkb, std::slice::from_ref(&pk.0))?;
+            let vuk = Vuk(derive_vuk(&km, &vid?.0));
+            Some(ResolvedChain {
+                unit_keys: boil(vuk)?,
+                vuk: Some(vuk),
+                mk: Some(MediaKey(km)),
+                pk: Some(*pk),
+                dk: None,
+            })
+        }
+        KeyCandidate::Dk(dk) => {
+            let (km, pk) = derive_media_key_and_pk_from_dk(mkb, std::slice::from_ref(dk))?;
+            let vuk = Vuk(derive_vuk(&km, &vid?.0));
+            Some(ResolvedChain {
+                unit_keys: boil(vuk)?,
+                vuk: Some(vuk),
+                mk: Some(MediaKey(km)),
+                pk: Some(ProcessingKey(pk)),
+                dk: Some(dk.clone()),
+            })
+        }
+    }
+}
+
+#[cfg(test)]
+mod resolve_candidate_tests {
+    use super::*;
+    use crate::aacs::crypto::aes_ecb_encrypt;
+
+    /// Minimal AACS-1.0 (48-byte stride) `Unit_Key_RO.inf` with `n` encrypted
+    /// unit keys — `parse_unit_key_ro` numbers CPS units 1..=n.
+    fn synth_inf(encs: &[[u8; 16]]) -> Vec<u8> {
+        let uk_pos = 32usize;
+        let stride = 48usize;
+        let n = encs.len();
+        let total = uk_pos + 48 + n.saturating_sub(1) * stride + 16;
+        let mut inf = vec![0u8; total.max(20)];
+        inf[..4].copy_from_slice(&(uk_pos as u32).to_be_bytes());
+        inf[uk_pos..uk_pos + 2].copy_from_slice(&(n as u16).to_be_bytes());
+        for (i, k) in encs.iter().enumerate() {
+            let o = uk_pos + 48 + i * stride;
+            inf[o..o + 16].copy_from_slice(k);
+        }
+        inf
+    }
+
+    /// A VUK candidate boils to ALL the disc's unit keys, each paired with its
+    /// declared CPS-unit number, and each key equals the VUK-decrypt of its slot.
+    #[test]
+    fn resolve_candidate_vuk_returns_all_cps_units() {
+        let vuk = Vuk([0x33u8; 16]);
+        let encs = [[0x11u8; 16], [0x22u8; 16], [0x44u8; 16]];
+        let inf = synth_inf(&encs);
+        let r = resolve_candidate(&KeyCandidate::Vuk(vuk), &[], &inf, None).expect("vuk derives");
+        let cps: Vec<u32> = r.unit_keys.iter().map(|(c, _)| *c).collect();
+        assert_eq!(
+            cps,
+            vec![1, 2, 3],
+            "every CPS unit surfaced, numbered from the inf"
+        );
+        for ((_, key), enc) in r.unit_keys.iter().zip(encs.iter()) {
+            assert_eq!(
+                *key,
+                decrypt_unit_key(&vuk.0, enc),
+                "key = VUK-decrypt of its slot"
+            );
+        }
+        assert_eq!(r.vuk, Some(vuk));
+        assert!(r.mk.is_none() && r.pk.is_none() && r.dk.is_none());
+    }
+
+    /// A bare UK candidate is terminal — it returns itself keyed by its own idx.
+    #[test]
+    fn resolve_candidate_uk_is_itself() {
+        let uk = UnitKey::new(2, [0x9u8; 16]);
+        let r = resolve_candidate(&KeyCandidate::Uk(uk), &[], &[], None).expect("uk is terminal");
+        assert_eq!(r.unit_keys, vec![(2, uk.key)]);
+        assert!(r.vuk.is_none() && r.mk.is_none());
+    }
+
+    /// MK/PK/DK paths derive the VUK from a VID; without one, derivation stops.
+    #[test]
+    fn resolve_candidate_mk_requires_vid() {
+        let r = resolve_candidate(&KeyCandidate::Mk(MediaKey([1u8; 16])), &[], &[], None);
+        assert!(r.is_none(), "MK path returns None without a VID");
+    }
+
+    /// A planted Processing Key resolves against a synthetic MKB and drives the
+    /// FULL chain PK → MK → VUK → UK — proving a PK candidate yields real keys.
+    #[test]
+    fn resolve_candidate_pk_drives_full_chain() {
+        let pk: [u8; 16] = [
+            0x11, 0x22, 0x33, 0x44, 0x55, 0x66, 0x77, 0x88, 0x99, 0xAA, 0xBB, 0xCC, 0xDD, 0xEE,
+            0xFF, 0x00,
+        ];
+        let mk: [u8; 16] = [
+            0xA0, 0xA1, 0xA2, 0xA3, 0xA4, 0xA5, 0xA6, 0xA7, 0xA8, 0xA9, 0xAA, 0xAB, 0xAC, 0xAD,
+            0xAE, 0xAF,
+        ];
+        let uv: [u8; 4] = [0x00, 0x00, 0x04, 0x00];
+
+        let mut mk_raw = mk;
+        for a in 0..4 {
+            mk_raw[12 + a] ^= uv[a];
+        }
+        let cv = aes_ecb_encrypt(&pk, &mk_raw);
+
+        let mut vd = [0x11u8; 16];
+        vd[..8].copy_from_slice(&[0x01, 0x23, 0x45, 0x67, 0x89, 0xAB, 0xCD, 0xEF]);
+        let mk_dv = aes_ecb_encrypt(&mk, &vd);
+
+        // 4-byte record header (type + BE24 total length) + body.
+        let rec = |t: u8, body: &[u8]| -> Vec<u8> {
+            let total = 4 + body.len();
+            let mut r = vec![
+                t,
+                ((total >> 16) & 0xFF) as u8,
+                ((total >> 8) & 0xFF) as u8,
+                (total & 0xFF) as u8,
+            ];
+            r.extend_from_slice(body);
+            r
+        };
+        let mut sd = vec![0u8];
+        sd.extend_from_slice(&uv);
+        let mut mkb = Vec::new();
+        mkb.extend_from_slice(&rec(0x10, &[0, 0, 0, 0x20, 0, 0, 0, 0x52]));
+        mkb.extend_from_slice(&rec(0x86, &mk_dv));
+        mkb.extend_from_slice(&rec(0x04, &sd));
+        mkb.extend_from_slice(&rec(0x05, &cv));
+
+        let vid = Vid([0x42u8; 16]);
+        let plain_uk = [0x7Eu8; 16];
+        let vuk = derive_vuk(&mk, &vid.0);
+        let enc = aes_ecb_encrypt(&vuk, &plain_uk);
+        let inf = synth_inf(std::slice::from_ref(&enc));
+
+        let r = resolve_candidate(&KeyCandidate::Pk(ProcessingKey(pk)), &mkb, &inf, Some(vid))
+            .expect("planted PK resolves the full chain");
+        assert_eq!(r.mk, Some(MediaKey(mk)), "PK recovers the planted MK");
+        assert_eq!(r.unit_keys.len(), 1);
+        assert_eq!(
+            r.unit_keys[0].1, plain_uk,
+            "PK chain recovers the title key"
+        );
+    }
+}

src/aacs/host_certs.rs

@@ -10,8 +10,8 @@
 pub fn collect_host_certs(
     opts: &crate::disc::ScanOptions,
     mkb: Option<u32>,
-) -> Vec<crate::aacs::HostCert> {
-    let mut host_certs: Vec<crate::aacs::HostCert> = Vec::new();
+) -> Vec<crate::aacs::types::HostCert> {
+    let mut host_certs: Vec<crate::aacs::types::HostCert> = Vec::new();
     if let Some(c) = &opts.credentials {
         host_certs.extend(c.host_certs.iter().cloned());
     }

src/aacs/inf.rs

@@ -0,0 +1,285 @@
+//! AACS on-disc key-input files: `Unit_Key_RO.inf` parsing, the disc-hash
+//! keydb lookup key, the Content Certificate, and the in-drive MKB read.
+//! These turn raw disc files into the structures the key paths consume.
+
+use super::mkb::*;
+
+/// Parsed Unit_Key_RO.inf file.
+#[derive(Debug)]
+pub struct UnitKeyFile {
+    /// Disc hash (SHA1 of the entire file) — used as KEYDB lookup key
+    pub disc_hash: [u8; 20],
+    /// Application type (1 = BD-ROM)
+    pub app_type: u8,
+    /// Number of BDMV directories
+    pub num_bdmv_dir: u8,
+    /// Whether SKB MKB is used
+    pub use_skb_mkb: bool,
+    /// AACS generation this file's stride matches
+    pub version: AacsVersion,
+    /// Encrypted unit keys (CPS unit number, encrypted key)
+    pub encrypted_keys: Vec<(u32, [u8; 16])>,
+    /// Title → CPS unit index mapping (title_idx → unit_key_idx)
+    pub title_cps_unit: Vec<u16>,
+}
+
+/// Compute disc hash (SHA1 of Unit_Key_RO.inf content).
+pub fn disc_hash(data: &[u8]) -> [u8; 20] {
+    use sha1::{Digest, Sha1};
+    let hash = Sha1::digest(data);
+    let mut out = [0u8; 20];
+    out.copy_from_slice(&hash);
+    out
+}
+
+/// Format disc hash as hex string with 0x prefix (for KEYDB lookup).
+pub fn disc_hash_hex(hash: &[u8; 20]) -> String {
+    let mut s = String::with_capacity(42);
+    s.push_str("0x");
+    for b in hash {
+        s.push_str(&format!("{b:02X}"));
+    }
+    s
+}
+
+/// Parse Unit_Key_RO.inf from raw bytes.
+///
+/// Format (from AACS spec):
+///   [0..4]   BE32: offset to key storage area (uk_pos)
+///   [16]     app_type (1 = BD-ROM)
+///   [17]     num_bdmv_dir
+///   [18]     bit 7: use_skb_mkb
+///   [20..22] BE16: first_play CPS unit
+///   [22..24] BE16: top_menu CPS unit
+///   [24..26] BE16: num_titles
+///   [26..]   title entries: 2 bytes padding + 2 bytes CPS unit, × num_titles
+///
+///   Key storage at uk_pos:
+///   [uk_pos..uk_pos+2]   BE16: num_unit_keys
+///   [uk_pos+48..]        encrypted keys, 16 bytes each
+///                         AACS 1.0: 48-byte stride
+///                         AACS 2.0 / 2.1: 64-byte stride (48 + 16 extra)
+pub fn parse_unit_key_ro(data: &[u8], version: AacsVersion) -> Option<UnitKeyFile> {
+    if data.len() < 20 {
+        return None;
+    }
+
+    let hash = disc_hash(data);
+
+    // Header
+    let app_type = data[16];
+    let num_bdmv_dir = data[17];
+    let use_skb_mkb = (data[18] >> 7) & 1 == 1;
+
+    // Key storage offset
+    let uk_pos = u32::from_be_bytes([data[0], data[1], data[2], data[3]]) as usize;
+    if uk_pos + 2 > data.len() {
+        return None;
+    }
+
+    // Number of unit keys
+    let num_uk = u16::from_be_bytes([data[uk_pos], data[uk_pos + 1]]) as usize;
+    if num_uk == 0 {
+        return Some(UnitKeyFile {
+            disc_hash: hash,
+            app_type,
+            num_bdmv_dir,
+            use_skb_mkb,
+            version,
+            encrypted_keys: Vec::new(),
+            title_cps_unit: Vec::new(),
+        });
+    }
+
+    // Stride between keys
+    let stride = version.unit_key_stride();
+
+    // Validate size
+    let keys_start = uk_pos + 48; // first key at uk_pos + 48
+    if keys_start + 16 > data.len() {
+        return None;
+    }
+
+    // Extract encrypted keys
+    let mut encrypted_keys = Vec::with_capacity(num_uk);
+    let mut pos = keys_start;
+    for i in 0..num_uk {
+        if pos + 16 > data.len() {
+            break;
+        }
+        let mut key = [0u8; 16];
+        key.copy_from_slice(&data[pos..pos + 16]);
+        encrypted_keys.push(((i + 1) as u32, key));
+        pos += stride;
+    }
+
+    // The loop above `break`s if the buffer runs out mid-key. A short list
+    // means the .inf is malformed/truncated — reject it rather than silently
+    // accepting fewer keys than the header declared, which would later map
+    // title CPS units to nonexistent keys.
+    if encrypted_keys.len() != num_uk {
+        return None;
+    }
+
+    // Title → CPS unit mapping (AACS Unit_Key_RO format): each on-disc CPS
+    // value is in `1..=num_uk` (else zeroes it) and converts the 1-based on-disc
+    // index to a 0-based key index. We mirror that so the stored value is a safe,
+    // ready-to-use key index rather than a raw 1-based number.
+    let to_key_idx = |cps: u16| -> u16 {
+        if cps >= 1 && cps as usize <= num_uk {
+            cps - 1
+        } else {
+            0
+        }
+    };
+    let mut title_cps_unit = Vec::new();
+    if data.len() >= 26 {
+        let first_play = u16::from_be_bytes([data[20], data[21]]);
+        let top_menu = u16::from_be_bytes([data[22], data[23]]);
+        let num_titles = u16::from_be_bytes([data[24], data[25]]) as usize;
+
+        title_cps_unit.push(to_key_idx(first_play));
+        title_cps_unit.push(to_key_idx(top_menu));
+
+        for i in 0..num_titles {
+            let off = 26 + i * 4 + 2; // 2 bytes padding + 2 bytes CPS unit
+            if off + 2 <= data.len() {
+                let cps = u16::from_be_bytes([data[off], data[off + 1]]);
+                title_cps_unit.push(to_key_idx(cps));
+            }
+        }
+    }
+
+    Some(UnitKeyFile {
+        disc_hash: hash,
+        app_type,
+        num_bdmv_dir,
+        use_skb_mkb,
+        version,
+        encrypted_keys,
+        title_cps_unit,
+    })
+}
+
+/// MKB disc structure format code.
+const MKB_DISC_STRUCTURE_FORMAT: u8 = 0x83;
+
+/// MKB pack buffer size.
+const MKB_PACK_SIZE: usize = 32772;
+
+/// Read MKB from drive via SCSI (REPORT DISC STRUCTURE format 0x83).
+/// Returns the concatenated MKB data from all packs.
+pub fn read_mkb_from_drive(
+    session: &mut dyn crate::scsi::ScsiTransport,
+) -> crate::error::Result<Vec<u8>> {
+    use crate::scsi::{DataDirection, SCSI_READ_DISC_STRUCTURE};
+
+    let cdb = [
+        SCSI_READ_DISC_STRUCTURE,
+        0x01,
+        0x00,
+        0x00,
+        0x00,
+        0x00,
+        0x00,
+        MKB_DISC_STRUCTURE_FORMAT,
+        (MKB_PACK_SIZE >> 8) as u8,
+        (MKB_PACK_SIZE & 0xFF) as u8,
+        0x00,
+        0x00,
+    ];
+    let mut buf = vec![0u8; 32772];
+    session.execute(&cdb, DataDirection::FromDevice, &mut buf, 10_000)?;
+
+    let data_len = u16::from_be_bytes([buf[0], buf[1]]) as usize;
+    if data_len < 2 {
+        return Ok(Vec::new());
+    }
+    let len = data_len - 2;
+    let num_packs = buf[3] as usize;
+
+    let mut mkb = Vec::with_capacity(32768 * num_packs.max(1));
+    if len > 0 && len <= 32768 {
+        mkb.extend_from_slice(&buf[4..4 + len]);
+    }
+
+    // Read remaining packs
+    for pack in 1..num_packs {
+        let mut cdb = [
+            SCSI_READ_DISC_STRUCTURE,
+            0x01,
+            0x00,
+            0x00,
+            0x00,
+            0x00,
+            0x00,
+            MKB_DISC_STRUCTURE_FORMAT,
+            (MKB_PACK_SIZE >> 8) as u8,
+            (MKB_PACK_SIZE & 0xFF) as u8,
+            0x00,
+            0x00,
+        ];
+        // Pack number goes in address field
+        cdb[2] = ((pack >> 24) & 0xFF) as u8;
+        cdb[3] = ((pack >> 16) & 0xFF) as u8;
+        cdb[4] = ((pack >> 8) & 0xFF) as u8;
+        cdb[5] = (pack & 0xFF) as u8;
+
+        let mut buf = vec![0u8; 32772];
+        if session
+            .execute(&cdb, DataDirection::FromDevice, &mut buf, 10_000)
+            .is_ok()
+        {
+            let len = u16::from_be_bytes([buf[0], buf[1]]) as usize;
+            if len > 2 && len - 2 <= 32768 {
+                mkb.extend_from_slice(&buf[4..4 + len - 2]);
+            }
+        }
+    }
+
+    Ok(mkb)
+}
+
+/// AACS Content Certificate — identifies disc AACS version and features.
+#[derive(Debug)]
+pub struct ContentCert {
+    /// Bus encryption enabled flag
+    pub bus_encryption: bool,
+    /// Content Certificate ID (6 bytes)
+    pub cc_id: [u8; 6],
+    /// AACS generation indicated by the certificate type byte.
+    ///
+    /// Cert type `0x00` → [`AacsVersion::V10`]; any other value →
+    /// [`AacsVersion::V20`]. The certificate alone cannot distinguish
+    /// V20 from V21 — Variant detection happens after the MKB walk.
+    pub version: AacsVersion,
+}
+
+/// Parse a Content Certificate (ContentXXX.cer) file.
+pub fn parse_content_cert(data: &[u8]) -> Option<ContentCert> {
+    if data.len() < 20 {
+        return None;
+    }
+
+    // Content Certificate layout (per the AACS content-cert format):
+    //   [0]      certificate type (0x00 = AACS1, 0x10 = AACS2)
+    //   [1] bit7 bus_encryption_enabled_flag  (`p[1] >> 7`)
+    //   [14..20] cc_id (6 bytes)             (`p + 14`)
+    let version = if data[0] == 0x00 {
+        AacsVersion::V10
+    } else {
+        AacsVersion::V20
+    };
+    // The flag is bit 7 of byte 1, NOT bit 0. Reading bit 0 (the prior bug) made
+    // a bus-encrypted cert (byte1=0x80) read as `false`, defeating the
+    // AacsBusKeyUnavailable fail-loud gate in disc/encrypt.rs.
+    let bus_encryption = (data[1] >> 7) & 1 == 1;
+    let mut cc_id = [0u8; 6];
+    cc_id.copy_from_slice(&data[14..20]);
+
+    Some(ContentCert {
+        bus_encryption,
+        cc_id,
+        version,
+    })
+}

src/aacs/mkb.rs

@@ -0,0 +1,435 @@
+//! AACS Media Key Block — [C] Chapter 3.
+//!
+//! The MKB record format (framing walker, the `MkbRecord` view, record-body
+//! finders), the MKBType / AACS-generation classification, and MKB-file
+//! utilities (content length, trimming, version). Consolidated here so the one
+//! place that understands MKB bytes is `mkb`. Some duplicate record finders
+//! still live side by side pending a follow-up that collapses them.
+
+// ── MKB record types ([C] Chapter 3) ──────────────────────────────────────
+// The ONE canonical set. Every record-type comparison in the `aacs` module
+// references these, so a type byte is never a bare literal scattered across
+// files (the `0x0c` variant-data record in particular used to appear in several
+// hand-rolled forms).
+
+/// Type-and-Version — carries the 32-bit MKBType / AACS generation.
+pub(crate) const REC_TYPE_AND_VERSION: u8 = 0x10;
+/// Subset-Difference index — the per-slot `(u_mask_shift, uv)` table.
+pub(crate) const REC_SUBSET_DIFFERENCE: u8 = 0x04;
+/// Media Key Data — the classical (1.0 / 2.0) per-subset cvalue table.
+pub(crate) const REC_MEDIA_KEY_DATA: u8 = 0x05;
+/// Explicit Subset-Difference — the smaller cvalue table some MKBs use.
+pub(crate) const REC_EXPLICIT_SUBSET_DIFF: u8 = 0x07;
+/// Media Key Variant Data (AACS 2.1) — the per-subset-difference `C` table
+/// (one 16-byte C per slot); the `Kmp` step reads C from HERE, not `0x2d`.
+pub(crate) const REC_MEDIA_KEY_VARIANT_DATA: u8 = 0x0c;
+/// Variant Data + Nonce (AACS 2.1) — the `VARIANTS[uv]` table (leading bytes)
+/// with the 16-byte `Kvn` Nonce at the tail.
+pub(crate) const REC_VARIANT_DATA_AND_NONCE: u8 = 0x2d;
+/// Variant Key Data table (AACS 2.1) — 65,535×16, indexed by the resolved VKD index.
+pub(crate) const REC_VKD_TABLE: u8 = 0x2f;
+/// Verify-Media-Key — AACS 1.0.
+pub(crate) const REC_VERIFY_MEDIA_KEY_V1: u8 = 0x81;
+/// Verify-Media-Key — AACS 2.x.
+pub(crate) const REC_VERIFY_MEDIA_KEY_V2: u8 = 0x86;
+
+/// A single MKB record produced by [`walk_mkb`].
+#[derive(Debug, Clone)]
+pub struct MkbRecord {
+    /// Byte offset of the record within the MKB.
+    pub offset: usize,
+    /// Record type byte.
+    pub rec_type: u8,
+    /// Record length in bytes (includes the 4-byte header).
+    pub rec_len: usize,
+    /// Record body (the bytes after the 4-byte header).
+    pub body: Vec<u8>,
+}
+
+/// Walk an MKB into a flat list of records.
+///
+/// MKB record framing per AACS: 1 byte type, 3 bytes BE length
+/// INCLUDING the 4-byte header, followed by payload. The walker stops
+/// at the first `(type=0, len=0)` end marker or at end of buffer.
+pub fn walk_mkb(mkb: &[u8]) -> Vec<MkbRecord> {
+    mkb_records(mkb)
+        .map(|(offset, rec_type, rec_len)| MkbRecord {
+            offset,
+            rec_type,
+            rec_len,
+            body: mkb[offset + 4..offset + rec_len].to_vec(),
+        })
+        .collect()
+}
+
+/// THE single MKB record-framing walker: yields `(offset, rec_type, rec_len)`
+/// for each record — a 4-byte header (type byte + big-endian 24-bit length)
+/// then the body — stopping at the `00 000000` end marker or a
+/// malformed/out-of-bounds length. Lazy (no body clone), so a find-one-record
+/// caller never materialises the multi-MB cvalue table. [`walk_mkb`] and every
+/// MKB record walk in `aacs::resolve`/`aacs::derive` are built on this, so the framing rules — and
+/// any future fix to them — live in exactly one place (they had drifted across
+/// six hand-rolled copies).
+pub(crate) fn mkb_records(mkb: &[u8]) -> impl Iterator<Item = (usize, u8, usize)> + '_ {
+    let mut pos = 0usize;
+    std::iter::from_fn(move || {
+        if pos + 4 > mkb.len() {
+            return None;
+        }
+        let rec_type = mkb[pos];
+        let rec_len = ((mkb[pos + 1] as usize) << 16)
+            | ((mkb[pos + 2] as usize) << 8)
+            | (mkb[pos + 3] as usize);
+        if rec_type == 0 && rec_len == 0 {
+            return None;
+        }
+        if rec_len < 4 || pos + rec_len > mkb.len() {
+            return None;
+        }
+        let here = pos;
+        pos += rec_len;
+        Some((here, rec_type, rec_len))
+    })
+}
+
+pub(crate) fn mkb_find_body(records: &[MkbRecord], rec_type: u8) -> Option<&[u8]> {
+    records
+        .iter()
+        .find(|r| r.rec_type == rec_type && !r.body.is_empty())
+        .map(|r| r.body.as_slice())
+}
+
+/// AACS protection generation a disc carries.
+///
+/// The content cert byte distinguishes V10 (`0x00`) from V20 (`0x01`). V21
+/// cannot be detected from the cert alone — a V21 disc carries a V20 cert
+/// and is upgraded to `V21` only after the MKB walk turns up the real Variant
+/// records `0x2d` / `0x2f` (Encrypted Media Key Variant Data and the Variant
+/// Key Data table).
+///
+/// Key-storage stride in `Unit_Key_RO.inf` is 48 bytes for V10 and 64
+/// bytes for V20 / V21.
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub enum AacsVersion {
+    /// AACS 1.0 — original BD-ROM.
+    V10,
+    /// AACS 2.0 — UHD-BD, classical Media Key derivation.
+    V20,
+    /// AACS 2.1 — UHD-BD with Media Key Variant chain on top of V20.
+    V21,
+}
+
+/// AACS major version as the small integer threaded through the scan / key
+/// paths (`AacsState.version`, `DiscInputs.version`, `DiscInputsCtx::new`):
+/// 1 = AACS 1.0 (BD), 2 = AACS 2.x (UHD). Centralised so the bare `1`/`2` — and
+/// the V10-vs-else stride choice it drives — lives in exactly one place.
+pub const AACS_MAJOR_BD: u8 = 1;
+
+pub const AACS_MAJOR_UHD: u8 = 2;
+
+impl AacsVersion {
+    /// Stride (in bytes) between successive encrypted unit keys in
+    /// `Unit_Key_RO.inf`.
+    pub(crate) fn unit_key_stride(self) -> usize {
+        match self {
+            AacsVersion::V10 => 48,
+            AacsVersion::V20 | AacsVersion::V21 => 64,
+        }
+    }
+
+    /// This version as the major integer ([`AACS_MAJOR_BD`] / [`AACS_MAJOR_UHD`]).
+    pub fn major(self) -> u8 {
+        match self {
+            AacsVersion::V10 => AACS_MAJOR_BD,
+            AacsVersion::V20 | AacsVersion::V21 => AACS_MAJOR_UHD,
+        }
+    }
+
+    /// The version a bare major integer selects for stride purposes: only the
+    /// BD major is V10; every other value takes the V20/V21 64-byte stride.
+    pub fn from_major(major: u8) -> Self {
+        if major == AACS_MAJOR_BD {
+            AacsVersion::V10
+        } else {
+            AacsVersion::V20
+        }
+    }
+}
+
+/// Find Verify Media Key Record (type 0x81 for AACS 1.0, 0x86 for AACS 2.0/2.1) in MKB.
+/// 0x81: [C] §3.2.5.1.4. 0x86 (AACS 2.x): [RE] — not in the public spec (from real 2.x MKBs).
+pub(crate) fn mkb_find_mk_dv(mkb: &[u8]) -> Option<[u8; 16]> {
+    // Verify-Media-Key record (0x81 for AACS 1.0, 0x86 for AACS 2.x): mk_dv is
+    // the 16 bytes at record offset 4 (body offset 0). Needs rec_len >= 20.
+    let found = mkb_records(mkb).find(|&(_, rt, len)| {
+        (rt == REC_VERIFY_MEDIA_KEY_V1 || rt == REC_VERIFY_MEDIA_KEY_V2) && len >= 20
+    });
+    match found {
+        Some((o, rec_type, rec_len)) => {
+            let mut dv = [0u8; 16];
+            dv.copy_from_slice(&mkb[o + 4..o + 20]);
+            tracing::debug!(
+                target: "freemkv::disc",
+                phase = "mkb_mk_dv_found",
+                rec_type,
+                pos = o,
+                rec_len,
+                "mk_dv extracted from MKB"
+            );
+            Some(dv)
+        }
+        None => {
+            tracing::warn!(
+                target: "freemkv::disc",
+                phase = "mkb_mk_dv_not_found",
+                "no 0x81/0x86 record with rec_len>=20 found"
+            );
+            None
+        }
+    }
+}
+
+/// Find Subset-Difference records (type 0x04) in MKB. [C] §3.2.5.1.5.
+pub(crate) fn mkb_find_subdiff_records(mkb: &[u8]) -> Option<Vec<u8>> {
+    find_record_body(mkb, 0x04)
+}
+
+/// Find the Media Key Data Record (cvalues table) in an MKB. [C] §3.2.4 / §3.2.5.1.7.
+///
+/// The cvalue table is record type `0x05` (Media Key Data) on BOTH AACS
+/// 1.0 and AACS 2.x MKBs — its 16-byte cvalue entries are 1:1 with the
+/// 5-byte Subset-Difference index entries in record `0x04` — the standard AACS
+/// MKB layout (`0x05` cvalues 1:1 with the `0x04` subset-difference index).
+///
+/// On AACS 2.x in-drive UHD MKBs the `0x05` table is large (the full
+/// subset-difference cvalue set: ~181k entries on a retail MKB, 1:1 with
+/// the giant `0x04` index), while record `0x07` (Explicit
+/// Subset-Difference Record) is a much smaller structure (~96 entries) and
+/// is NOT the cvalue table. An earlier version of this function preferred
+/// `0x07`, which under-tested the Subset-Difference walk on UHD discs and
+/// prevented the DK→walk path from ever finding the matching uv. The
+/// selection MUST therefore be `0x05`-first; `0x07` is only a fallback for
+/// malformed/legacy MKBs that somehow lack a `0x05` record.
+pub(crate) fn mkb_find_cvalues(mkb: &[u8]) -> Option<Vec<u8>> {
+    if let Some(body) = find_record_body(mkb, 0x05) {
+        return Some(body);
+    }
+    find_record_body(mkb, 0x07)
+}
+
+/// Walk an MKB and return the payload (header stripped) of the first
+/// record matching `rec_type`. Returns `None` if no such record exists or
+/// the record is empty.
+pub(crate) fn find_record_body(mkb: &[u8], rec_type_wanted: u8) -> Option<Vec<u8>> {
+    mkb_records(mkb)
+        .find(|&(_, rt, len)| rt == rec_type_wanted && len > 4)
+        .map(|(o, _, len)| mkb[o + 4..o + len].to_vec())
+}
+
+/// Real content length of an MKB: the byte offset where the record stream
+/// ends. MKB files (especially `MKB_RW.inf`, but `MKB_RO.inf` too on some
+/// discs) are allocated to a fixed size — often ~128 MiB — with the records at
+/// the front and the rest zero padding. Walking records (type+len) and stopping
+/// at the first padding byte (`type == 0` / zero-length / overrun) gives the
+/// actual size so callers can trim off megabytes of zeros before sending or
+/// archiving. Returns `mkb.len()` only if the whole buffer parsed as records.
+pub fn mkb_content_len(mkb: &[u8]) -> usize {
+    // End of the last framed record = where the fixed-region zero padding begins.
+    // (The `00 000000` terminator / overrun stops the walk; real MKBs pad with
+    // zeros, so this matches the prior "stop at the first padding byte".)
+    mkb_records(mkb)
+        .last()
+        .map(|(o, _, len)| o + len)
+        .unwrap_or(0)
+}
+
+/// Trim an MKB's trailing fixed-region padding to its real content length —
+/// but ONLY when [`mkb_content_len`] actually found one. It returns 0 for an
+/// MKB whose first record cannot be parsed; truncating to 0 in that case would
+/// hand downstream consumers (and the online key service) an EMPTY MKB that can
+/// never resolve. So a 0 (or a length that isn't strictly inside the buffer)
+/// leaves the MKB untouched. A 0.31.0 regression dropped this guard and
+/// `truncate`-d unconditionally, zeroing unrecognised MKBs.
+pub fn trim_mkb(mut mkb: Vec<u8>) -> Vec<u8> {
+    let n = mkb_content_len(&mkb);
+    if n > 0 && n < mkb.len() {
+        mkb.truncate(n);
+    }
+    mkb
+}
+
+/// Get MKB version from Type and Version Record (type 0x10).
+/// Layout: 4-byte record header at `pos` (type + BE24 length), then the
+/// record body starts at `pos + 4`. The body holds the BE u32 Type field at
+/// body offset 0 (`pos + 4`), then the BE u32 version at body offset 4
+/// (`pos + 8`).
+pub fn mkb_version(mkb: &[u8]) -> Option<u32> {
+    // Type-and-Version record (0x10): version is the BE u32 at body offset 4
+    // (record offset 8). Needs rec_len >= 12 (4 header + 4 type + 4 version).
+    mkb_records(mkb)
+        .find(|&(_, rt, len)| rt == REC_TYPE_AND_VERSION && len >= 12)
+        .map(|(o, _, _)| u32::from_be_bytes([mkb[o + 8], mkb[o + 9], mkb[o + 10], mkb[o + 11]]))
+}
+
+/// `0x00031003` — recordable media MKB (Class I & II compute Km directly).
+pub const MKB_TYPE_3_RECORDABLE: u32 = 0x0003_1003;
+
+/// `0x00041003` — AACS 1.0 pre-recorded content MKB (KCD-based). Standard BD.
+pub const MKB_TYPE_4_PRERECORDED: u32 = 0x0004_1003;
+
+/// `0x000A1003` — Class II / Unified MKB (Sequence-Key-Block functionality).
+pub const MKB_TYPE_10_CLASS_II: u32 = 0x000A_1003;
+
+/// `0x48141003` — AACS 2.0 Category C (UHD content) MKB type value.
+pub const MKB_20_CATEGORY_C: u32 = 0x4814_1003;
+
+/// `0x48151003` — AACS 2.1 Category C (UHD content) MKB type value.
+pub const MKB_21_CATEGORY_C: u32 = 0x4815_1003;
+
+/// The AACS MKB Type field, decoded.
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub enum MkbType {
+    /// Type 3 — recordable media.
+    Recordable,
+    /// Type 4 — AACS 1.0 pre-recorded content (KCD). Standard Blu-ray.
+    Prerecorded,
+    /// Type 10 — Class II / Unified (SKB).
+    ClassII,
+    /// AACS 2.0 Category C — UHD content.
+    CategoryC20,
+    /// AACS 2.1 Category C — UHD content.
+    CategoryC21,
+    /// Unrecognized MKBType value (raw field preserved).
+    Other(u32),
+}
+
+impl MkbType {
+    pub(crate) fn from_raw(raw: u32) -> Self {
+        match raw {
+            MKB_TYPE_3_RECORDABLE => MkbType::Recordable,
+            MKB_TYPE_4_PRERECORDED => MkbType::Prerecorded,
+            MKB_TYPE_10_CLASS_II => MkbType::ClassII,
+            MKB_20_CATEGORY_C => MkbType::CategoryC20,
+            MKB_21_CATEGORY_C => MkbType::CategoryC21,
+            other => MkbType::Other(other),
+        }
+    }
+
+    /// AACS generation this MKB belongs to (Category C → 2.0/2.1, else 1.0).
+    pub fn generation(self) -> AacsVersion {
+        match self {
+            MkbType::CategoryC21 => AacsVersion::V21,
+            MkbType::CategoryC20 => AacsVersion::V20,
+            _ => AacsVersion::V10,
+        }
+    }
+
+    /// `true` for UHD (AACS 2.x Category C); `false` for Blu-ray (AACS 1.x).
+    pub fn is_uhd(self) -> bool {
+        matches!(self, MkbType::CategoryC20 | MkbType::CategoryC21)
+    }
+}
+
+/// The raw 32-bit MKBType field from the Type-and-Version record (0x10), bytes
+/// 4-7. `None` if no 0x10 record is present. [C] §3.2.5.1.1 Table 3-2.
+pub fn mkb_type_raw(mkb: &[u8]) -> Option<u32> {
+    // Type-and-Version record (0x10): the 32-bit MKBType is bytes 4-7 (body
+    // offset 0). Needs rec_len >= 8 (4 header + 4 type).
+    mkb_records(mkb)
+        .find(|&(_, rt, len)| rt == REC_TYPE_AND_VERSION && len >= 8)
+        .map(|(o, _, _)| u32::from_be_bytes([mkb[o + 4], mkb[o + 5], mkb[o + 6], mkb[o + 7]]))
+}
+
+/// Decode an MKB's Type field. `None` if no Type-and-Version record is present.
+pub fn mkb_type(mkb: &[u8]) -> Option<MkbType> {
+    mkb_type_raw(mkb).map(MkbType::from_raw)
+}
+
+/// `Some(true)` if this MKB is a UHD (AACS 2.x Category C) block, `Some(false)`
+/// for Blu-ray (AACS 1.x), `None` if the Type record is absent.
+pub fn mkb_is_uhd(mkb: &[u8]) -> Option<bool> {
+    mkb_type(mkb).map(MkbType::is_uhd)
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    /// One MKB record: 1 type byte + big-endian 24-bit total length + body.
+    fn rec(rec_type: u8, body: &[u8]) -> Vec<u8> {
+        let len = 4 + body.len();
+        let mut v = vec![rec_type, (len >> 16) as u8, (len >> 8) as u8, len as u8];
+        v.extend_from_slice(body);
+        v
+    }
+
+    /// Type-and-Version record (0x10): body = 4-byte MKBType + 4-byte version.
+    fn type_and_version(mkb_type: u32, version: u32) -> Vec<u8> {
+        let mut body = mkb_type.to_be_bytes().to_vec();
+        body.extend_from_slice(&version.to_be_bytes());
+        rec(REC_TYPE_AND_VERSION, &body)
+    }
+
+    #[test]
+    fn walker_frames_records_and_stops_at_end_marker() {
+        let mut mkb = type_and_version(MKB_20_CATEGORY_C, 77);
+        mkb.extend(rec(REC_VKD_TABLE, &[0xAA; 16]));
+        mkb.extend([0x00, 0x00, 0x00, 0x00]); // end marker
+        mkb.extend(rec(0x99, &[0xFF; 8])); // must NOT be walked (past the marker)
+
+        let recs = walk_mkb(&mkb);
+        assert_eq!(recs.len(), 2, "walk stops at the 00 000000 end marker");
+        assert_eq!(recs[0].rec_type, REC_TYPE_AND_VERSION);
+        assert_eq!(recs[1].rec_type, REC_VKD_TABLE);
+        assert_eq!(recs[1].body, vec![0xAA; 16]);
+    }
+
+    #[test]
+    fn walker_stops_on_malformed_or_out_of_bounds_length() {
+        // A record whose declared length runs past the buffer end must terminate
+        // the walk rather than panic or read OOB.
+        let mkb = vec![REC_VKD_TABLE, 0x00, 0xFF, 0xFF, 0x01, 0x02]; // len=0xFFFF, only 6 bytes
+        assert!(
+            walk_mkb(&mkb).is_empty(),
+            "over-long record yields no records"
+        );
+        // A sub-4 length (shorter than the header itself) is also rejected.
+        let short = vec![REC_VKD_TABLE, 0x00, 0x00, 0x02];
+        assert!(walk_mkb(&short).is_empty(), "sub-4 length is rejected");
+        // A truncated header (< 4 bytes) yields nothing.
+        assert!(walk_mkb(&[0x10, 0x00]).is_empty());
+    }
+
+    #[test]
+    fn mkb_type_and_version_decode_from_the_type_record() {
+        let mut mkb = type_and_version(MKB_21_CATEGORY_C, 100);
+        mkb.extend([0x00, 0x00, 0x00, 0x00]);
+        assert_eq!(mkb_type_raw(&mkb), Some(MKB_21_CATEGORY_C));
+        assert_eq!(mkb_version(&mkb), Some(100));
+        assert_eq!(mkb_is_uhd(&mkb), Some(true), "2.1 Category C is UHD");
+
+        let bd = type_and_version(MKB_TYPE_4_PRERECORDED, 68);
+        assert_eq!(
+            mkb_is_uhd(&bd),
+            Some(false),
+            "AACS 1.0 prerecorded is not UHD"
+        );
+        // No Type record → None (not a panic, not a fabricated value).
+        assert_eq!(mkb_version(&rec(REC_VKD_TABLE, &[0; 16])), None);
+        assert_eq!(mkb_type_raw(&[]), None);
+    }
+
+    #[test]
+    fn trim_mkb_keeps_only_the_framed_records() {
+        let mut mkb = type_and_version(MKB_20_CATEGORY_C, 1);
+        let content_len = mkb.len(); // the single framed record, no end marker
+        mkb.extend([0x00, 0x00, 0x00, 0x00]); // end marker
+        mkb.extend([0xDE; 4096]); // trailing padding past the end marker
+        let trimmed = trim_mkb(mkb);
+        assert_eq!(
+            trimmed.len(),
+            content_len,
+            "trim keeps the framed records, dropping the end marker and padding"
+        );
+    }
+}

src/aacs/mod.rs

@@ -13,15 +13,32 @@
 //!
 //! The VUK decrypts title keys from AACS/Unit_Key_RO.inf on disc.
 //! Title keys decrypt m2ts stream content (AES-128-CBC).
+//!
+//! ## Spec provenance
+//!
+//! The crypto below carries `[TAG] §x.y` citations back to the published AACS
+//! specification (Final Rev 0.953), so each primitive links to the section it
+//! implements:
+//!   - `[C]`  — AACS Introduction and Common Cryptographic Elements Book (primitives, MKB/key-management).
+//!   - `[PR]` — AACS Pre-recorded Video Book (Volume/Title Key layer).
+//!   - `[BD]` — AACS Blu-ray Disc Pre-recorded Book (CPS Unit Key, Aligned Unit, Block Key).
+//!   - `[RE]` — reverse-engineered from real discs, cited only where the public
+//!     spec is silent (the `0x86` verify record and the Category-C MKB type values).
 
-pub mod boil;
-pub mod decrypt;
+pub mod content;
+pub mod crypto;
+pub mod derive;
 pub mod host_certs;
-pub mod keys;
+pub mod inf;
+pub mod mkb;
 pub mod provider;
+pub mod resolve;
+pub mod segment;
+pub mod segment_key;
 pub mod trace;
 pub mod types;
-pub mod variants;
+pub mod variant;
+pub mod variant_select;
 
 /// On-disc UDF paths to the AACS key-input files (with their fallbacks).
 /// Centralised so every reader (`resolve_vid_only`, `read_aacs_inputs`,
@@ -35,53 +52,29 @@ pub const PATH_MKB_RW: &str = "/AACS/MKB_RW.inf";
 pub const PATH_CONTENT_CERT: &str = "/AACS/Content000.cer";
 pub const PATH_CONTENT_CERT_ALT: &str = "/AACS/Content001.cer";
 
-// Boil-down derivation primitives (thin newtypes + wrappers over the crypto).
-pub use boil::{
-    KeyCandidate, MediaKey, ProcessingKey, ResolvedChain, UnitKey, Vid, Vuk, mk_from_dk,
-    mk_from_pk, resolve_candidate, uk_from_vuk, vuk_from_mk,
-};
-// Structured, English-free resolution trace.
-pub use trace::{KeyNode, KeyOutcome, KeyStep, ResolutionTrace, UnlockOutcome, UnlockStep};
-
-// Explicit re-exports — only items needed by external consumers and sibling crate modules.
-// AES primitives (aes_ecb_encrypt, aes_ecb_decrypt, aes_cbc_decrypt) are pub(crate) in decrypt.rs.
-pub use decrypt::{
-    ALIGNED_UNIT_LEN, ALIGNED_UNIT_SECTORS, UnitKeyResult, aacs_unit_encrypted,
-    aacs_unit_needs_decrypt, aacs_unit_still_ciphertext, decrypt_bus, decrypt_unit,
-    decrypt_unit_checked, decrypt_unit_full, decrypt_unit_try_keys, fill_null_ts_unit,
-    is_unit_aligned, ts_packet_total, ts_sync_count, ts_sync_destroyed, unit_is_clean_ps,
-    unit_is_clean_ts, unit_key_validates,
-};
-// `probe` is a reproduction-harness helper (see keys.rs), not part of the
-// documented 1.0 surface; keep it reachable but off the rendered docs so we
-// don't commit semver stability to test primitives.
-#[doc(hidden)]
-pub use keys::probe;
-pub use keys::{
-    AACS_MAJOR_BD, AACS_MAJOR_UHD, AacsVersion, ContentCert, MKB_20_CATEGORY_C, MKB_21_CATEGORY_C,
-    MKB_TYPE_3_RECORDABLE, MKB_TYPE_4_PRERECORDED, MKB_TYPE_10_CLASS_II, MkbType, ResolveContext,
-    ResolveFailure, ResolvedKeys, UnitKeyFile, decrypt_unit_key, derive_media_key_and_pk_from_dk,
-    derive_media_key_from_dk, derive_media_key_from_pk, derive_vuk, disc_hash, disc_hash_hex,
-    mkb_content_len, mkb_is_uhd, mkb_type, mkb_type_raw, mkb_version, parse_content_cert,
-    parse_unit_key_ro, read_mkb_from_drive, recover_dk_position, resolve_keys_v1, resolve_keys_v2,
-    resolve_keys_v21, resolve_keys_with_reason, trim_mkb,
-};
-pub use provider::KeyProvider;
-pub use types::{DeviceKey, DiscEntry, HostCert};
-pub use variants::{
-    KEY_CORRECTION_DATA_PLACEHOLDER, MediaKeyVariantError, MkbRecord, ProcessingKeyMatch,
-    derive_media_key_variant, is_variant_mkb, variant_nonce, walk_mkb, walk_processing_key,
-};
+// The module structure IS the public API — consumers import from the owning
+// module directly (e.g. `aacs::content::decrypt_unit`, `aacs::mkb::MkbType`,
+// `aacs::derive::{derive_vuk, resolve_candidate}`, `aacs::resolve::resolve_keys_v2`).
+// The `derive::probe` reproduction harness stays reachable via its module path.
+//
+// A small set of flat re-exports is kept for the typed key primitives and the
+// content-decrypt entry points that downstream key-source crates import through
+// the `aacs::` path. These are the stable, load-bearing names; keeping them here
+// lets those crates track the module refactor without a lockstep re-pin.
+pub use content::{ALIGNED_UNIT_LEN, decrypt_unit_try_keys};
+pub use derive::derive_vuk;
+pub use types::{DeviceKey, HostCert, MediaKey, ProcessingKey, UnitKey, Vid, Vuk};
 
 #[cfg(test)]
 mod tests {
-    //! Re-export surface guards. The module's public API is the set of
-    //! `pub use` items above. A regression that drops or renames an export
-    //! (the class of bug that shipped in 0.31.0 by silently changing a
-    //! surface) breaks compilation of these references, so they act as a
-    //! compile-time contract for the crate's AACS surface.
+    //! Surface guards. The public API is the module tree itself (no facade).
+    //! Touching one representative item per module keeps these as a
+    //! compile-time contract that the module paths stay stable.
 
-    use super::*;
+    use super::content::{ALIGNED_UNIT_LEN, ts_sync_destroyed};
+    use super::inf::{disc_hash, disc_hash_hex};
+    use super::mkb::{AacsVersion, mkb_content_len, walk_mkb};
+    use super::variant::is_variant_mkb;
 
     #[test]
     fn aligned_unit_len_is_three_2048_byte_sectors() {
@@ -103,21 +96,18 @@ mod tests {
     }
 
     #[test]
-    fn key_correction_data_placeholder_is_all_zero() {
-        // The variant chain refuses to run against this all-zero placeholder
-        // KCD; the public constant must therefore be exactly 16 zero bytes.
-        assert_eq!(KEY_CORRECTION_DATA_PLACEHOLDER, [0u8; 16]);
-    }
-
-    #[test]
-    fn public_helpers_are_callable_through_the_facade() {
-        // Touch a representative function from each re-export group so a
-        // dropped/renamed export fails to compile. These are smoke calls, not
-        // behavioural assertions (behaviour is covered in each module).
+    fn public_helpers_are_callable_by_module_path() {
+        // Touch a representative function from each module so a dropped/renamed
+        // item fails to compile. Smoke calls, not behavioural assertions.
         let _ = ts_sync_destroyed(&[0u8; ALIGNED_UNIT_LEN]);
         let _ = mkb_content_len(&[]);
         let _ = is_variant_mkb(&walk_mkb(&[]));
         let _ = disc_hash_hex(&disc_hash(b"x"));
-        let _ = mk_from_pk(&[[0u8; 16]], &[]);
+        let _ = super::derive::resolve_candidate(
+            &super::derive::KeyCandidate::Uk(super::types::UnitKey::new(0, [0u8; 16])),
+            &[],
+            &[],
+            None,
+        );
     }
 }

src/aacs/provider.rs

@@ -42,7 +42,7 @@ use super::types::{DeviceKey, DiscEntry, HostCert};
 /// Source of AACS key material.
 ///
 /// Implementors return raw material only — the resolver in
-/// `aacs::keys` owns all the crypto (DK→PK walking, PK validation,
+/// `aacs::resolve` and `aacs::derive` own the crypto (DK→PK walking, PK validation,
 /// MK→VUK→TK derivation). See module docs for method semantics.
 pub trait KeyProvider: Send + Sync {
     /// Device keys (top-of-tree, walked by the resolver).

src/aacs/segment.rs

@@ -0,0 +1,303 @@
+//! AACS 2.1 FMTS forensic segment map — `AACS/IndividualSegment.tbl`.
+//!
+//! An FMTS main feature interleaves N "variant" segments — the sequence-key /
+//! forensic-watermark mechanism. The same frames are authored as several
+//! slightly different variants; each variant is encrypted under its own SEGMENT
+//! key (from `SegmentKeyNNNNN.tbl`), NOT the CPS Unit Key. A player with the
+//! right device keys can decrypt exactly one variant per segment, and which one
+//! silently identifies the player (traitor tracing). Decrypting a variant
+//! segment with the Unit Key yields garbage — broken HEVC reference frames
+//! (empirically: `Could not find ref with POC …` on a plain unit-key rip).
+//!
+//! This table says WHERE the variant segments live so a decoder can decrypt
+//! them with segment keys and select one coherent variant instead of muxing
+//! unit-key garbage.
+//!
+//! Format (validated against a retail AACS 2.1 disc):
+//! ```text
+//!   header (8 bytes):  u32 type | u16 count | u16 record_size (= 16)
+//!   record[count] (16 bytes each):
+//!     u32 marker (= 0x01000000) | u16 variant | u16 flag (= 1)
+//!     u32 start_spn | u32 end_spn        (source-packet numbers, inclusive)
+//! ```
+//! `variant` is the 1..32 forensic-variant tag, NOT a sequential segment id:
+//! measured on a retail 2.1 disc (Zombieland) it cycles 1,2,…,32,1,2,… across
+//! records in file order — 24 full cycles of 32 plus a final partial cycle of
+//! 24 = 792 records. Source-packet numbers are the 192-byte BDAV packet index:
+//! byte offset = `spn * 192`. Each segment is ~2560 packets (~480 KB), spread
+//! across the entire 54 GB feature (one roughly every 67 MB).
+
+/// Fixed size of one `IndividualSegment.tbl` record.
+pub const SEGMENT_RECORD_LEN: usize = 16;
+/// Bytes per BDAV source packet (188-byte TS + 4-byte arrival-time header).
+pub const SOURCE_PACKET_LEN: u64 = 192;
+
+/// Whether a 2.1 (FMTS) disc may rip WITHOUT segment (variant) keys.
+///
+/// `true` (today): the forensic variant segments are skipped as expected loss
+/// and the bulk of the title decodes with the unit key, so a 2.1 disc rips
+/// mostly-complete. A unit key (VUK) is still required, exactly as for any AACS
+/// disc. `false`: the absence of a segment-key source is a hard, UPFRONT failure
+/// ([`Error::FmtsKeyMissing`]) — the same policy as a missing unit key, so a
+/// forensic-holed rip is refused rather than produced. No segment-key source
+/// exists yet, so `true` is the only value under which a 2.1 disc rips at all;
+/// flip to `false` once segment keys can be sourced and a partial rip should be
+/// refused. Hardcoded on purpose — not a user setting.
+///
+/// [`Error::FmtsKeyMissing`]: crate::error::Error::FmtsKeyMissing
+pub const BYPASS_FMTS_KEY: bool = true;
+
+/// One forensic variant segment: the inclusive source-packet range it occupies
+/// in the FMTS clip.
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub struct Segment {
+    /// Forensic variant tag, 1..=32 (field@4 of the record). Cycles across the
+    /// table rather than counting up — it selects WHICH variant this range is,
+    /// which is what a variant-keyed decode routes on. (`0` is not used here;
+    /// the default/non-forensic content carries no segment record at all.)
+    pub variant: u16,
+    /// First source packet of the segment (inclusive).
+    pub start_spn: u32,
+    /// Last source packet of the segment (inclusive).
+    pub end_spn: u32,
+}
+
+impl Segment {
+    /// Source-packet count in this (inclusive) segment.
+    pub fn packet_count(&self) -> u32 {
+        self.end_spn
+            .saturating_sub(self.start_spn)
+            .saturating_add(1)
+    }
+
+    /// Byte offset of the segment start within the clip (`start_spn * 192`).
+    pub fn start_byte(&self) -> u64 {
+        self.start_spn as u64 * SOURCE_PACKET_LEN
+    }
+
+    /// Byte length of the segment (`packet_count * 192`).
+    pub fn byte_len(&self) -> u64 {
+        self.packet_count() as u64 * SOURCE_PACKET_LEN
+    }
+
+    /// True when source packet `spn` falls inside this segment.
+    pub fn contains_spn(&self, spn: u32) -> bool {
+        spn >= self.start_spn && spn <= self.end_spn
+    }
+
+    /// True when the inclusive source-packet span `[first, last]` overlaps this
+    /// segment. Used to decide whether an aligned unit (which spans several
+    /// packets) touches the segment at all, not just whether one packet does.
+    pub fn overlaps_spn(&self, first: u32, last: u32) -> bool {
+        first <= self.end_spn && last >= self.start_spn
+    }
+}
+
+/// Source packets spanned by one AACS aligned unit: `6144 / 192 = 32`.
+pub const PACKETS_PER_UNIT: u32 =
+    (crate::aacs::content::ALIGNED_UNIT_LEN as u64 / SOURCE_PACKET_LEN) as u32;
+
+/// Byte offset within the clip of a clip-relative 2048-byte sector `lba`. The
+/// FMTS decode reads the clip file directly, so `lba` 0 is the clip's first
+/// byte and this offset lines up with the source-packet grid the segment map
+/// uses.
+pub fn lba_byte_offset(lba: u32) -> u64 {
+    lba as u64 * 2048
+}
+
+/// The forensic segment an AACS aligned unit belongs to, if any, given the
+/// unit's clip-relative byte offset.
+///
+/// This is the routing decision behind a 2.1 decrypt-miss: a unit that
+/// overlaps a forensic segment must be opened with that segment's **variant
+/// key** (from `SegmentKeyNNNNN.tbl`), not the CPS Unit Key. Opening it with
+/// the Unit Key is exactly what yields the broken-reference-frame garbage a
+/// plain unit-key rip produces. A unit outside every segment is ordinary
+/// content and a miss on it is a Unit-Key miss, so this returns `None` and the
+/// caller falls back to the normal unit-key fetch.
+///
+/// The unit is tested as a packet *span* (`[off/192, (off+6144-1)/192]`) so a
+/// unit that only partly overlaps a segment edge is still classified as
+/// variant; on the observed disc segments are unit-aligned, but the span test
+/// does not rely on that.
+pub fn variant_segment_for_unit(segments: &[Segment], unit_offset: u64) -> Option<&Segment> {
+    let unit_len = crate::aacs::content::ALIGNED_UNIT_LEN as u64;
+    let first = (unit_offset / SOURCE_PACKET_LEN) as u32;
+    let last = ((unit_offset + unit_len - 1) / SOURCE_PACKET_LEN) as u32;
+    segments.iter().find(|s| s.overlaps_spn(first, last))
+}
+
+/// Parse `IndividualSegment.tbl` into its forensic variant segments, in table
+/// order. Returns `None` when the header is malformed, the record size is not
+/// [`SEGMENT_RECORD_LEN`], or the declared record count overruns the buffer —
+/// so a truncated / foreign table degrades to "no segment map" rather than
+/// yielding bogus ranges.
+pub fn parse_individual_segments(tbl: &[u8]) -> Option<Vec<Segment>> {
+    if tbl.len() < 8 {
+        return None;
+    }
+    let count = u16::from_be_bytes([tbl[4], tbl[5]]) as usize;
+    let record_size = u16::from_be_bytes([tbl[6], tbl[7]]) as usize;
+    if record_size != SEGMENT_RECORD_LEN {
+        return None;
+    }
+    if 8usize.checked_add(count.checked_mul(record_size)?)? > tbl.len() {
+        return None;
+    }
+    let mut segments = Vec::with_capacity(count);
+    for i in 0..count {
+        let o = 8 + i * record_size;
+        // o+4..o+8 = variant (u16, 1..32) + flag (u16); o+8..o+16 = start/end SPN.
+        let variant = u16::from_be_bytes([tbl[o + 4], tbl[o + 5]]);
+        let start_spn = u32::from_be_bytes([tbl[o + 8], tbl[o + 9], tbl[o + 10], tbl[o + 11]]);
+        let end_spn = u32::from_be_bytes([tbl[o + 12], tbl[o + 13], tbl[o + 14], tbl[o + 15]]);
+        segments.push(Segment {
+            variant,
+            start_spn,
+            end_spn,
+        });
+    }
+    Some(segments)
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    /// Build a table with the real on-disc layout: 8-byte header + N 16-byte
+    /// records. `recs` are `(variant, start_spn, end_spn)`.
+    fn build_tbl(recs: &[(u16, u32, u32)]) -> Vec<u8> {
+        let mut v = Vec::new();
+        v.extend_from_slice(&0x0100_0000u32.to_be_bytes()); // type
+        v.extend_from_slice(&(recs.len() as u16).to_be_bytes()); // count
+        v.extend_from_slice(&(SEGMENT_RECORD_LEN as u16).to_be_bytes()); // record_size
+        for &(n, s, e) in recs {
+            v.extend_from_slice(&0x0100_0000u32.to_be_bytes()); // marker
+            v.extend_from_slice(&n.to_be_bytes());
+            v.extend_from_slice(&1u16.to_be_bytes()); // flag
+            v.extend_from_slice(&s.to_be_bytes());
+            v.extend_from_slice(&e.to_be_bytes());
+        }
+        v
+    }
+
+    #[test]
+    fn parses_real_disc_layout() {
+        // First three records observed on retail 2.1 (Zombieland): the variant
+        // field counts 1,2,3,… (it wraps at 32 further into the table — see
+        // `variant_field_cycles_one_to_thirty_two`), segments are 2560 packets.
+        let tbl = build_tbl(&[
+            (1, 343680, 346239),
+            (2, 695616, 698175),
+            (3, 1051840, 1054399),
+        ]);
+        let segs = parse_individual_segments(&tbl).expect("parse");
+        assert_eq!(segs.len(), 3);
+        assert_eq!(segs[0].variant, 1);
+        assert_eq!(segs[1].variant, 2);
+        assert_eq!(segs[2].variant, 3);
+        assert_eq!(segs[0].start_spn, 343680);
+        assert_eq!(segs[0].end_spn, 346239);
+        assert_eq!(segs[0].packet_count(), 2560);
+        assert_eq!(segs[0].byte_len(), 2560 * 192);
+        assert_eq!(segs[0].start_byte(), 343680 * 192);
+        assert!(segs[0].contains_spn(345000));
+        assert!(!segs[0].contains_spn(343679));
+        assert!(!segs[0].contains_spn(346240));
+    }
+
+    #[test]
+    fn rejects_wrong_record_size() {
+        let mut tbl = build_tbl(&[(1, 0, 10)]);
+        tbl[6..8].copy_from_slice(&20u16.to_be_bytes()); // record_size != 16
+        assert!(parse_individual_segments(&tbl).is_none());
+    }
+
+    #[test]
+    fn rejects_truncated_and_overrun() {
+        assert!(parse_individual_segments(&[0u8; 4]).is_none()); // < header
+        let mut tbl = build_tbl(&[(1, 0, 10)]);
+        tbl[4..6].copy_from_slice(&99u16.to_be_bytes()); // claims 99 recs, has 1
+        assert!(parse_individual_segments(&tbl).is_none());
+    }
+
+    #[test]
+    fn empty_table_is_empty_not_none() {
+        let tbl = build_tbl(&[]);
+        assert_eq!(parse_individual_segments(&tbl), Some(Vec::new()));
+    }
+
+    #[test]
+    fn packets_per_unit_is_thirty_two() {
+        // 6144-byte aligned unit / 192-byte source packet.
+        assert_eq!(PACKETS_PER_UNIT, 32);
+    }
+
+    #[test]
+    fn unit_inside_segment_routes_to_variant() {
+        // A real first-record segment: packets [343680, 346239].
+        let segs = parse_individual_segments(&build_tbl(&[(1, 343680, 346239)])).unwrap();
+        // A unit sitting squarely inside: start at packet 344000 → byte 344000*192.
+        let off = 344000u64 * SOURCE_PACKET_LEN;
+        let hit = variant_segment_for_unit(&segs, off).expect("inside the segment");
+        assert_eq!(hit.variant, 1);
+    }
+
+    #[test]
+    fn variant_field_cycles_one_to_thirty_two() {
+        // Reality on Zombieland: field@4 is the variant, cycling 1..=32 in file
+        // order (NOT a sequential segment id). Reproduce one-and-a-bit cycles.
+        let mut recs = Vec::new();
+        let mut spn = 1000u32;
+        for row in 0..2 {
+            for v in 1..=32u16 {
+                recs.push((v, spn, spn + 2559));
+                spn += 50_000; // ~one segment every ~67 MB
+            }
+            let _ = row;
+        }
+        let segs = parse_individual_segments(&build_tbl(&recs)).unwrap();
+        assert_eq!(segs.len(), 64);
+        assert_eq!(segs[31].variant, 32); // end of first cycle
+        assert_eq!(segs[32].variant, 1); // wraps, does not become 33
+        assert!(segs.iter().all(|s| (1..=32).contains(&s.variant)));
+    }
+
+    #[test]
+    fn unit_outside_every_segment_is_unit_key_miss() {
+        let segs = parse_individual_segments(&build_tbl(&[(1, 343680, 346239)])).unwrap();
+        // A unit well before the segment is ordinary content → None (unit-key path).
+        let off = 1000u64 * SOURCE_PACKET_LEN;
+        assert!(variant_segment_for_unit(&segs, off).is_none());
+    }
+
+    #[test]
+    fn unit_straddling_a_segment_edge_counts_as_variant() {
+        // Segment starts at packet 100. A unit that ENDS just inside it (its 32
+        // packets straddle the boundary) must still route to the variant key,
+        // because part of its ciphertext is variant-encrypted.
+        let segs = parse_individual_segments(&build_tbl(&[(7, 100, 200)])).unwrap();
+        // Unit covering packets [80, 111]: overlaps [100,200] at the tail.
+        let off = 80u64 * SOURCE_PACKET_LEN;
+        let hit = variant_segment_for_unit(&segs, off).expect("straddles the start edge");
+        assert_eq!(hit.variant, 7);
+        // A unit ending exactly at packet 99 (offset s.t. last = 99) does NOT overlap.
+        let before = 68u64 * SOURCE_PACKET_LEN; // [68, 99]
+        assert!(variant_segment_for_unit(&segs, before).is_none());
+    }
+
+    #[test]
+    fn no_segments_never_routes_to_variant() {
+        // The 1.0 / 2.0 case: no forensic map, so every miss is a unit-key miss.
+        assert!(variant_segment_for_unit(&[], lba_byte_offset(0)).is_none());
+        assert!(variant_segment_for_unit(&[], lba_byte_offset(9_999_999)).is_none());
+    }
+
+    #[test]
+    fn lba_maps_to_the_packet_grid() {
+        // A unit is 3 sectors (6144 bytes) = 32 packets. Clip-relative LBA 3 is
+        // the second aligned unit, which starts at packet 32.
+        let off = lba_byte_offset(3);
+        assert_eq!(off / SOURCE_PACKET_LEN, 32);
+    }
+}

src/aacs/segment_key.rs

@@ -0,0 +1,165 @@
+//! AACS 2.1 FMTS forensic segment keys, `AACS/SegmentKeyNNNNN.tbl`.
+//!
+//! One file per CPS unit (`SegmentKey00001.tbl`, ...). It is the on-disc key
+//! store for the forensic variant segments mapped by [`super::segment`]. A
+//! device does not read a segment key directly. It derives a **16-bit variant
+//! selector** from the Media Key Variant chain (see [`super::variant`]) and uses
+//! that selector to index this table, which is how the device's position in the
+//! key tree decides which variant it can decrypt (the traitor-tracing link).
+//!
+//! Container format (confirmed against a retail AACS 2.1 disc):
+//! ```text
+//!   header (8 bytes):  u32 tag | u16 index_space | u16 record_size
+//!   record[index_space]  (record_size bytes each)
+//! ```
+//! On the reference disc: `index_space` = `0xffff` (the full 16-bit selector
+//! space, 65536 records), `record_size` = `0x0218` = 536. Total
+//! `8 + 65536 * 536 = 35,127,304` bytes, which matches the file exactly. Each
+//! record begins with an 8-byte sub-header, then 528 bytes of encrypted key
+//! material.
+//!
+//! **Not yet reversed:** the internal layout of a record's 528-byte payload, and
+//! how it maps onto the segments of [`super::segment`]. One numeric coincidence
+//! worth noting for whoever cracks it: the reference disc has 792 segments and
+//! `528 = 33 * 16`, with `792 = 24 * 33`, so `33` appears on both sides. Until
+//! the mapping and the key derivation are pinned, this module exposes only the
+//! confirmed container: locate the record for a given 16-bit selector.
+
+/// Bytes of the fixed file header.
+pub const HEADER_LEN: usize = 8;
+
+/// The on-disc segment-key table container. Borrows the file bytes; a record is
+/// looked up by the 16-bit variant selector.
+#[derive(Debug, Clone, Copy)]
+pub struct SegmentKeyTable<'a> {
+    data: &'a [u8],
+    /// Number of records (the selector index space, e.g. 65536).
+    count: usize,
+    /// Bytes per record (e.g. 536).
+    record_size: usize,
+}
+
+impl<'a> SegmentKeyTable<'a> {
+    /// Parse and validate the container header against the buffer length.
+    ///
+    /// Returns `None` when the buffer is too small, or the declared
+    /// `count * record_size` (plus header) does not match the buffer, so a
+    /// truncated or foreign table degrades to "no segment keys" rather than
+    /// handing back bogus records. `index_space` of `0xffff` is read as the full
+    /// 65536-entry space (a device selector is a full 16-bit value).
+    pub fn parse(data: &'a [u8]) -> Option<Self> {
+        if data.len() < HEADER_LEN {
+            return None;
+        }
+        let index_space = u16::from_be_bytes([data[4], data[5]]);
+        let record_size = u16::from_be_bytes([data[6], data[7]]) as usize;
+        // 0xffff means the full 16-bit selector space (65536 records).
+        let count = if index_space == 0xffff {
+            0x1_0000
+        } else {
+            index_space as usize
+        };
+        if record_size == 0 {
+            return None;
+        }
+        let body = count.checked_mul(record_size)?;
+        if HEADER_LEN.checked_add(body)? != data.len() {
+            return None;
+        }
+        Some(Self {
+            data,
+            count,
+            record_size,
+        })
+    }
+
+    /// Number of records (the selector index space).
+    pub fn record_count(&self) -> usize {
+        self.count
+    }
+
+    /// Bytes per record.
+    pub fn record_size(&self) -> usize {
+        self.record_size
+    }
+
+    /// The raw record for a 16-bit variant `selector`, including its 8-byte
+    /// sub-header. `None` if the selector is past the table (only possible when
+    /// `index_space` was not the full 16-bit space).
+    pub fn record(&self, selector: u16) -> Option<&'a [u8]> {
+        let idx = selector as usize;
+        if idx >= self.count {
+            return None;
+        }
+        let start = HEADER_LEN + idx * self.record_size;
+        self.data.get(start..start + self.record_size)
+    }
+
+    /// The encrypted key payload for a selector: the record with its 8-byte
+    /// sub-header stripped. The internal layout of these bytes is not yet
+    /// reversed (see module docs).
+    pub fn record_payload(&self, selector: u16) -> Option<&'a [u8]> {
+        self.record(selector).and_then(|r| r.get(HEADER_LEN..))
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    /// Build a container with `record_size` and the given `index_space`, filling
+    /// each record with a distinguishable byte so lookups can be checked.
+    fn build(index_space: u16, record_size: u16) -> Vec<u8> {
+        let count = if index_space == 0xffff {
+            0x1_0000
+        } else {
+            index_space as usize
+        };
+        let mut v = Vec::with_capacity(HEADER_LEN + count * record_size as usize);
+        v.extend_from_slice(&0x0100_0000u32.to_be_bytes()); // tag
+        v.extend_from_slice(&index_space.to_be_bytes());
+        v.extend_from_slice(&record_size.to_be_bytes());
+        for i in 0..count {
+            let mut rec = vec![(i & 0xff) as u8; record_size as usize];
+            // sub-header, as seen on disc
+            rec[..8].copy_from_slice(&[0x01, 0x00, 0x00, 0x00, 0x00, 0x20, 0x01, 0x02]);
+            v.extend_from_slice(&rec);
+        }
+        v
+    }
+
+    #[test]
+    fn parses_retail_container_geometry() {
+        // The real disc: 0xffff index space, 536-byte records, 35,127,304 total.
+        let data = build(0xffff, 536);
+        assert_eq!(
+            data.len(),
+            35_127_304,
+            "matches the retail file size exactly"
+        );
+        let t = SegmentKeyTable::parse(&data).expect("parse");
+        assert_eq!(t.record_count(), 65_536);
+        assert_eq!(t.record_size(), 536);
+        let rec = t.record(0x1234).expect("record");
+        assert_eq!(rec.len(), 536);
+        assert_eq!(&rec[..8], &[0x01, 0x00, 0x00, 0x00, 0x00, 0x20, 0x01, 0x02]);
+        assert_eq!(t.record_payload(0x1234).unwrap().len(), 528);
+    }
+
+    #[test]
+    fn small_index_space_bounds_lookups() {
+        let data = build(4, 32);
+        let t = SegmentKeyTable::parse(&data).expect("parse");
+        assert_eq!(t.record_count(), 4);
+        assert!(t.record(3).is_some());
+        assert!(t.record(4).is_none(), "selector past the table is None");
+    }
+
+    #[test]
+    fn rejects_size_mismatch_and_truncation() {
+        assert!(SegmentKeyTable::parse(&[0u8; 4]).is_none());
+        let mut data = build(4, 32);
+        data.truncate(data.len() - 1); // body no longer matches header
+        assert!(SegmentKeyTable::parse(&data).is_none());
+    }
+}

src/aacs/types.rs

@@ -27,6 +27,74 @@ pub struct HostCert {
     pub certificate_v2: Option<Vec<u8>>,
 }
 
+/// Volume ID (16 bytes) — read from the disc via the SCSI handshake / OEM path.
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub struct Vid(pub [u8; 16]);
+
+/// Media Key (Km, 16 bytes) — the MKB-scoped key derived from device keys.
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub struct MediaKey(pub [u8; 16]);
+
+/// Volume Unique Key (VUK / Kvu, 16 bytes) — derived from `MediaKey` + `Vid`,
+/// decrypts the per-disc encrypted title keys in `Unit_Key_RO.inf`.
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub struct Vuk(pub [u8; 16]);
+
+/// Processing Key (Kp, 16 bytes) — an MKB Subset-Difference key that yields the
+/// Media Key. A leaked/precomputed PK in the keydb, or the intermediate PK a
+/// device-key walk derives at its matching SD node.
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub struct ProcessingKey(pub [u8; 16]);
+
+/// One decrypted per-CPS-unit AACS title key.
+///
+/// `idx` is the POSITIONAL index of the encrypted title key within the slice
+/// handed to the VUK→UK step (i.e. its order in `Unit_Key_RO.inf`'s key-storage
+/// area). The CPS-unit *number* association is a higher-level concern owned by
+/// [`super::inf::parse_unit_key_ro`], which pairs each positional key with its
+/// declared CPS unit; this primitive only does the AES, so it surfaces position.
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub struct UnitKey {
+    pub idx: u32,
+    pub key: [u8; 16],
+    /// AACS 2.1 (FMTS) forensic-variant tag.
+    ///
+    /// `0` = ordinary (non-forensic) content — the value for every 1.0 / 2.0
+    /// key and for the bulk of a 2.1 title. `1..=32` = a variant key that
+    /// decrypts the forensic segments tagged with that same variant in
+    /// `IndividualSegment.tbl`. A disc resolves to exactly one variant, so at
+    /// most one non-zero value is ever in play for a given rip; the decode
+    /// selects the segments matching it and drops the other variants.
+    pub variant_number: u8,
+}
+
+impl UnitKey {
+    /// An ordinary (non-forensic) unit key: `variant_number == 0`. The value
+    /// for every AACS 1.0 / 2.0 key and the bulk of a 2.1 title.
+    pub const fn new(idx: u32, key: [u8; 16]) -> Self {
+        Self {
+            idx,
+            key,
+            variant_number: 0,
+        }
+    }
+
+    /// A forensic-variant key: `variant_number` in `1..=32`, decrypting the
+    /// `IndividualSegment.tbl` segments tagged with that variant.
+    pub const fn variant(idx: u32, key: [u8; 16], variant_number: u8) -> Self {
+        Self {
+            idx,
+            key,
+            variant_number,
+        }
+    }
+
+    /// Whether this key decrypts ordinary (non-forensic) content.
+    pub const fn is_default_variant(&self) -> bool {
+        self.variant_number == 0
+    }
+}
+
 /// A per-disc entry from the key database.
 #[derive(Debug, Clone)]
 pub struct DiscEntry {

src/aacs/variant.rs

@@ -3,34 +3,20 @@
 //! On AACS 2.1 the Media Key derivation gains a second stage on top of
 //! the classical subset-difference walk. The classical walk yields a
 //! Media Key Precursor (Kmp) rather than the final Media Key; the
-//! Precursor combines with disc-supplied Variant Key Data (VKD) and an
-//! integrator-supplied Key Correction Data (KCD) constant to produce
-//! the Media Key.
+//! Precursor combines with disc-supplied Variant Key Data (VKD) and a
+//! per-licensee Key Correction Data (KCD) constant to produce the Media
+//! Key.
 //!
-//! This module is wiring only — `resolve_keys` is not aware of it. The
-//! entry point is [`derive_media_key_variant`]. The Variant scheme is
-//! detected via the real AACS 2.1 MKB records `0x2d` (Encrypted Media
-//! Key Variant Data / C), `0x2f` (Variant Key Data table, 65,535×16),
-//! and `0x0c` (variant cvalues, one per `0x04` subset-difference slot).
-//! When a disc carries none, callers fall back to the classical
-//! single-stage derivation in [`super::keys`]. (The earlier `0x82`/`0x83`
-//! record types were a speculative guess that never appeared in any real
-//! MKB; they were replaced with the real records once a live variant MKB
-//! was obtained.)
+//! The entry point is [`derive_media_key_variant`] — a `Kp -> Km`
+//! derivation. Deriving `Kp` itself from device keys (DK -> PK) is the
+//! separate [`walk_processing_key`] step. The Variant scheme is detected
+//! via the AACS 2.1 MKB records `0x2d` (Encrypted Media Key Variant Data
+//! / C), `0x2f` (Variant Key Data table, up to 65,535×16), and `0x0c`
+//! (variant cvalues, one per `0x04` subset-difference slot). When a disc
+//! carries none, callers fall back to the classical single-stage
+//! derivation in [`super::derive`].
 //!
-//! **Status: the chain cannot yet produce a key on a real disc — for two
-//! reasons, one external, one internal:**
-//!   - EXTERNAL: no device key in our pool walks any real variant MKB,
-//!     so `Kp` (and thus the whole chain) can't be produced live. This is
-//!     a key-acquisition gap, not a code gap.
-//!   - INTERNAL: the exact `VARIANTS[uv]` lookup ([`variants_for_uv`])
-//!     and the Nonce / C sub-field offsets can't be pinned without a real
-//!     disc + covering key to run the chain end-to-end against the `0x86`
-//!     verify. Until then [`variants_for_uv`] returns `None` and the
-//!     chain halts at [`MediaKeyVariantError::VariantsTableUnavailable`],
-//!     so a wrong best-effort offset is never silently trusted.
-//!
-//! The chain follows the published spec:
+//! The chain:
 //!
 //! ```text
 //! Kmp     = AES-128D(Kp, C) XOR uv
@@ -41,96 +27,55 @@
 //! Km      = AES-128D(Kpnew, VKD) XOR uv
 //! ```
 //!
-//! Two condition bits on `Kmp[15]` route off the hardcoded-KCD path
-//! (Soft Correction and Online Challenge). The chain refuses to run in
-//! either case — callers must handle those modes out of band.
+//! **Status.** The record layout is pinned against real variant MKBs:
+//! `C` is the per-slot block of the `0x0c` cvalue table (indexed by the
+//! matched subset-difference — NOT the `0x2d` head), `VARIANTS[uv]` is the
+//! `0x2d` VARIANTS table (leading `body-16` bytes, Nonce at the `0x2d`
+//! tail), and `VKD` is `0x2f`. Two inputs still block an end-to-end run
+//! against the `0x86` Verify-Media-Key record: the real per-licensee KCD
+//! (see [`KEY_CORRECTION_DATA`] — not coded, per-manufacturer), and a
+//! covering 2.1 Processing Key. Either one missing yields a wrong `Km`
+//! that the final verify gate rejects, so a bad key is never emitted —
+//! only an error. (A covering key would also confirm the last layout
+//! picks: the 16-bit `Kvn` width and Nonce head-vs-tail.)
 //!
-//! # Status: Kp verification
+//! Two condition bits on `Kmp[15]` route off the default KCD path (Soft
+//! Correction and Online Challenge); the chain does not model those modes
+//! and treats such a slot as non-covering.
 //!
-//! On the classical path [`walk_processing_key`] gates each match on
-//! the VERIFY_MAGIC relation, which authenticates the Processing Key.
-//! On a variant MKB that magic check does NOT hold (the walk yields a
-//! Media Key *Precursor*, not the Media Key), so the walk accepts a
-//! variant match without it. The replacement gate lives at the END of
-//! [`derive_media_key_variant`]: the derived final `Km` is verified
-//! against the MKB's Verify-Media-Key record before any `(Km, Kvu)` is
-//! returned. A future implementer wiring [`variants_for_uv`] must keep
-//! that final gate — the per-match magic check no longer protects the
-//! variant path.
+//! **Verify gate.** On the classical path [`walk_processing_key`] gates
+//! each match on the VERIFY_MAGIC relation, which authenticates the
+//! Processing Key. On a variant MKB that magic does NOT hold (the walk
+//! yields a Precursor, not the Media Key), so the authoritative gate is
+//! at the END of the chain: the derived `Km` is verified against the
+//! MKB's Verify-Media-Key record before it is ever returned.
 
-use super::decrypt::aes_ecb_decrypt;
+use super::crypto::{aes_ecb_decrypt, aes_g};
+use super::mkb::*;
 use super::types::DeviceKey;
 
+// The MKB record types this chain selects — `REC_MEDIA_KEY_VARIANT_DATA`
+// (`0x0c`, the per-slot C table), `REC_VARIANT_DATA_AND_NONCE` (`0x2d`, VARIANTS
+// + tail Nonce), `REC_VKD_TABLE` (`0x2f`), the subset-difference / cvalue records
+// (`0x04` / `0x05` / `0x07`), and the verify records (`0x81` / `0x86`) — are the
+// canonical set in [`super::mkb`], in scope here via the `use super::mkb::*` glob.
+
 // ── Public constants ──────────────────────────────────────────────────────
 
-/// Placeholder Key Correction Data. Sixteen zero bytes.
+/// AACS 2.1 Key Correction Data — a zero placeholder, NOT real key material.
 ///
-/// Integrators MUST supply a non-placeholder KCD via the `kcd` argument
-/// to [`derive_media_key_variant`]; the chain refuses to operate when
-/// the supplied KCD compares equal to this placeholder.
-pub const KEY_CORRECTION_DATA_PLACEHOLDER: [u8; 16] = [0u8; 16];
+/// **KCD is PER-LICENSEE** (per player manufacturer) — there is no single
+/// universal value. libfreemkv compiles in no AACS key material (keydb.cfg is
+/// the single source of truth), so this stays all-zero: the chain's SHAPE still
+/// runs, but on a real variant disc the derivation yields a wrong Media Key that
+/// the final Verify-Media-Key gate rejects. The variant chain therefore cannot
+/// complete on a real disc today — a key-acquisition gap, not a code gap. If a
+/// real per-licensee KCD is ever available it must come from keydb.cfg, never a
+/// compiled constant.
+const KEY_CORRECTION_DATA: [u8; 16] = [0u8; 16];
 
 // ── MKB record walking ────────────────────────────────────────────────────
 
-/// A single MKB record produced by [`walk_mkb`].
-#[derive(Debug, Clone)]
-pub struct MkbRecord {
-    /// Byte offset of the record within the MKB.
-    pub offset: usize,
-    /// Record type byte.
-    pub rec_type: u8,
-    /// Record length in bytes (includes the 4-byte header).
-    pub rec_len: usize,
-    /// Record body (the bytes after the 4-byte header).
-    pub body: Vec<u8>,
-}
-
-/// Walk an MKB into a flat list of records.
-///
-/// MKB record framing per AACS: 1 byte type, 3 bytes BE length
-/// INCLUDING the 4-byte header, followed by payload. The walker stops
-/// at the first `(type=0, len=0)` end marker or at end of buffer.
-pub fn walk_mkb(mkb: &[u8]) -> Vec<MkbRecord> {
-    mkb_records(mkb)
-        .map(|(offset, rec_type, rec_len)| MkbRecord {
-            offset,
-            rec_type,
-            rec_len,
-            body: mkb[offset + 4..offset + rec_len].to_vec(),
-        })
-        .collect()
-}
-
-/// THE single MKB record-framing walker: yields `(offset, rec_type, rec_len)`
-/// for each record — a 4-byte header (type byte + big-endian 24-bit length)
-/// then the body — stopping at the `00 000000` end marker or a
-/// malformed/out-of-bounds length. Lazy (no body clone), so a find-one-record
-/// caller never materialises the multi-MB cvalue table. [`walk_mkb`] and every
-/// MKB record walk in `aacs::keys` are built on this, so the framing rules — and
-/// any future fix to them — live in exactly one place (they had drifted across
-/// six hand-rolled copies).
-pub(crate) fn mkb_records(mkb: &[u8]) -> impl Iterator<Item = (usize, u8, usize)> + '_ {
-    let mut pos = 0usize;
-    std::iter::from_fn(move || {
-        if pos + 4 > mkb.len() {
-            return None;
-        }
-        let rec_type = mkb[pos];
-        let rec_len = ((mkb[pos + 1] as usize) << 16)
-            | ((mkb[pos + 2] as usize) << 8)
-            | (mkb[pos + 3] as usize);
-        if rec_type == 0 && rec_len == 0 {
-            return None;
-        }
-        if rec_len < 4 || pos + rec_len > mkb.len() {
-            return None;
-        }
-        let here = pos;
-        pos += rec_len;
-        Some((here, rec_type, rec_len))
-    })
-}
-
 /// True iff `records` contains at least one Media Key Variant record.
 ///
 /// The real AACS 2.1 Variant markers — confirmed against a live variant MKB —
@@ -140,40 +85,41 @@ pub(crate) fn mkb_records(mkb: &[u8]) -> impl Iterator<Item = (usize, u8, usize)
 /// The earlier `0x82`/`0x83` guess was speculative and never appeared in any
 /// real MKB.
 pub fn is_variant_mkb(records: &[MkbRecord]) -> bool {
-    records.iter().any(|r| matches!(r.rec_type, 0x2d | 0x2f))
+    records
+        .iter()
+        .any(|r| matches!(r.rec_type, REC_VARIANT_DATA_AND_NONCE | REC_VKD_TABLE))
 }
 
-/// Body of the Encrypted Media Key Variant Data record (type `0x2d`).
-///
-/// Confirmed against a live variant MKB as the `0x2d` record (92,220 bytes on
-/// the reference disc — not a clean multiple of 16, so it is a structured /
-/// count-prefixed record, not a flat C-block table). The exact per-uv C
-/// selection is the one sub-field still unconfirmed without a real disc+key to
-/// test against; the chain currently consumes the leading 16-byte block.
-/// `pub(crate)` until that offset is pinned.
+/// Body of the `0x2d` record: the `VARIANTS` table followed by the trailing
+/// 16-byte `Kvn` Nonce. Measured `46_100*2 + 16 = 92_216` on Zombieland v70 and
+/// `92_220` on Stand By Me v70 — in both, the leading `body.len() - 16` bytes are
+/// the big-endian `u16` `VARIANTS` table (one per subset-difference) and the last
+/// 16 bytes are the Nonce, with NO leading header. This does NOT hold the C used
+/// for `Kmp` — that is the per-slot block in `0x0c`
+/// ([`REC_MEDIA_KEY_VARIANT_DATA`]). Both [`variant_nonce`] and
+/// [`variants_for_uv`] read this body.
 pub(crate) fn variant_data_record(records: &[MkbRecord]) -> Option<&[u8]> {
     records
         .iter()
-        .find(|r| r.rec_type == 0x2d)
+        .find(|r| r.rec_type == REC_VARIANT_DATA_AND_NONCE)
         .map(|r| r.body.as_slice())
 }
 
-/// 16-byte Nonce for `Kvn = AES-G(Kp, Nonce)`.
+/// 16-byte Nonce for `Kvn = AES-G(Kp, Nonce)` — the trailing 16 bytes of the
+/// `0x2d` record ([`variant_data_record`]).
 ///
-/// **UNCONFIRMED source.** The speculative `0x83` "Variant Number" record does
-/// not exist on a real variant MKB. The `0x2d` Encrypted-Media-Key-Variant-Data
-/// record is the most likely home for a per-disc nonce, so this best-effort
-/// reads the trailing 16 bytes of `0x2d`. Confirming this (vs. a field inside
-/// `0x21`, or a fixed slice of `0x2d`) needs a real disc+key to test the whole
-/// chain against the `0x86` verify — until then the chain halts earlier at
-/// [`variants_for_uv`], so a wrong nonce here is never silently trusted.
+/// The Nonce-at-tail placement is consistent across both reference MKBs (the
+/// leading `body-16` bytes form the `VARIANTS` table exactly), but head-vs-tail
+/// is only truly pinned by running the full chain against the `0x86` verify with
+/// a covering key. Until then a wrong nonce can only fail that final gate, never
+/// emit a bad key.
 pub fn variant_nonce(records: &[MkbRecord]) -> Option<[u8; 16]> {
-    let r = records.iter().find(|r| r.rec_type == 0x2d)?;
-    if r.body.len() < 16 {
+    let body = variant_data_record(records)?;
+    if body.len() < 16 {
         return None;
     }
     let mut out = [0u8; 16];
-    out.copy_from_slice(&r.body[r.body.len() - 16..]);
+    out.copy_from_slice(&body[body.len() - 16..]);
     Some(out)
 }
 
@@ -185,34 +131,17 @@ pub fn variant_nonce(records: &[MkbRecord]) -> Option<[u8; 16]> {
 pub(crate) fn variant_key_data(records: &[MkbRecord]) -> Option<&[u8]> {
     records
         .iter()
-        .find(|r| r.rec_type == 0x2f && !r.body.is_empty() && r.body.len() % 16 == 0)
+        .find(|r| r.rec_type == REC_VKD_TABLE && !r.body.is_empty() && r.body.len() % 16 == 0)
         .map(|r| r.body.as_slice())
 }
 
-// ── AES-G ────────────────────────────────────────────────────────────────
-
-/// AES-G(x1, x2) = AES-128D(x1, x2) XOR x2.
-///
-/// The Media Key Variant chain uses AES-G to derive both the variant
-/// number (`Kvn = AES-G(Kp, Nonce)`) and the Volume Unique Key
-/// (`Kvu = AES-G(Km, VID)`). See [`super::keys::derive_vuk`] for the
-/// classical VUK form — the math is identical, this exposes it as a
-/// neutral primitive for the variant chain.
-fn aes_g(x1: &[u8; 16], x2: &[u8; 16]) -> [u8; 16] {
-    let mut out = aes_ecb_decrypt(x1, x2);
-    for i in 0..16 {
-        out[i] ^= x2[i];
-    }
-    out
-}
-
 // ── Subset-difference walk that exposes (Kp, uv) ──────────────────────────
 
 // `calc_v_mask` and `calc_pk_from_dk` (and the AES-G3 seed step they ride
-// on) are shared with the classical walk in [`super::keys`] — a single
+// on) are shared with the classical walk in [`super::derive`] — a single
 // definition keeps the variant SD tree byte-identical to the classical one.
 // (`aesg3` itself is imported separately in the test module.)
-use super::keys::{calc_pk_from_dk, calc_v_mask};
+use super::derive::{calc_pk_from_dk, calc_v_mask};
 
 /// Outcome of a subset-difference walk against an MKB. Carries the
 /// processing key and the matching `uv` slot — both needed as inputs
@@ -229,17 +158,11 @@ pub struct ProcessingKeyMatch {
     pub cvalue_index: usize,
 }
 
-fn mkb_find_body(records: &[MkbRecord], rec_type: u8) -> Option<&[u8]> {
-    records
-        .iter()
-        .find(|r| r.rec_type == rec_type && !r.body.is_empty())
-        .map(|r| r.body.as_slice())
-}
-
 fn mkb_find_mk_dv(records: &[MkbRecord]) -> Option<[u8; 16]> {
-    let r = records
-        .iter()
-        .find(|r| (r.rec_type == 0x81 || r.rec_type == 0x86) && r.body.len() >= 16)?;
+    let r = records.iter().find(|r| {
+        (r.rec_type == REC_VERIFY_MEDIA_KEY_V1 || r.rec_type == REC_VERIFY_MEDIA_KEY_V2)
+            && r.body.len() >= 16
+    })?;
     let mut out = [0u8; 16];
     out.copy_from_slice(&r.body[..16]);
     Some(out)
@@ -249,7 +172,7 @@ fn mkb_find_mk_dv(records: &[MkbRecord]) -> Option<[u8; 16]> {
 /// `device_keys` covers. Returns `None` if no DK walks any uv.
 ///
 /// This is the AACS-2.1 **variant** walk; the classical walk lives in
-/// [`super::keys::derive_media_key_and_pk_from_dk`]. The two are kept
+/// [`super::derive::derive_media_key_and_pk_from_dk`]. The two are kept
 /// separate on purpose and select MKB records in DELIBERATELY different
 /// order:
 ///
@@ -258,10 +181,10 @@ fn mkb_find_mk_dv(records: &[MkbRecord]) -> Option<[u8; 16]> {
 ///     small `0x07` Explicit-Subset-Difference record carries the
 ///     cvalue the Precursor chain consumes, whereas a classical UHD MKB
 ///     keeps its 1:1 cvalue table in the large `0x05` record (see the
-///     note on [`super::keys::probe::mkb_cvalues`]). They must NOT be
+///     note on [`super::derive::probe::mkb_cvalues`]). They must NOT be
 ///     unified to one order — each is correct for its own MKB shape.
 ///   - finders: this walk operates on parsed [`MkbRecord`]s (needed
-///     because the variant chain also reads `0x82`/`0x83`); the
+///     because the variant chain also reads `0x2d`/`0x2f`); the
 ///     classical walk operates on raw MKB bytes. Same framing, different
 ///     input type.
 ///
@@ -273,14 +196,14 @@ pub fn walk_processing_key(
     device_keys: &[DeviceKey],
 ) -> Option<ProcessingKeyMatch> {
     let mk_dv = mkb_find_mk_dv(records)?;
-    let uvs = mkb_find_body(records, 0x04)?;
+    let uvs = mkb_find_body(records, REC_SUBSET_DIFFERENCE)?;
     // Variant cvalue source: a real variant MKB carries its per-uv cvalue table
     // in record `0x0c` (confirmed 46,101×16, one per `0x04` subset-difference
     // slot). Fall back to `0x07`/`0x05` for the synthetic fixtures and any MKB
     // shape that keeps its cvalues there.
-    let cvalues = mkb_find_body(records, 0x0c)
-        .or_else(|| mkb_find_body(records, 0x07))
-        .or_else(|| mkb_find_body(records, 0x05))?;
+    let cvalues = mkb_find_body(records, REC_MEDIA_KEY_VARIANT_DATA)
+        .or_else(|| mkb_find_body(records, REC_EXPLICIT_SUBSET_DIFF))
+        .or_else(|| mkb_find_body(records, REC_MEDIA_KEY_DATA))?;
 
     let num_uvs = uvs
         .chunks(5)
@@ -298,14 +221,11 @@ pub fn walk_processing_key(
             // parse stops, no inner re-check needed.
             let u_mask_shift = uvs[5 * uvs_idx];
 
-            if u_mask_shift & 0xC0 != 0 {
-                break;
-            }
-            // 0x20..=0x3F (32..=63) pass the 0xC0 revoked-marker check but are
-            // out of range for a u32 shift. `wrapping_shl` would silently
-            // compute shift % 32 (e.g. 32 → no shift → 0xFFFF_FFFF), matching a
-            // wrong uv slot and deriving a wrong key. Disc-controlled byte:
-            // skip the slot instead.
+            // 0x20..=0x3F (32..=63) have their revoked-marker bits clear (so they
+            // pass the take_while above) but are out of range for a u32 shift.
+            // `wrapping_shl` would silently compute shift % 32 (e.g. 32 → no shift
+            // → 0xFFFF_FFFF), matching a wrong uv slot and deriving a wrong key.
+            // Disc-controlled byte: skip the slot instead.
             if u_mask_shift >= 32 {
                 continue;
             }
@@ -393,10 +313,8 @@ pub enum MediaKeyVariantError {
     /// `Kmp[15]` carries bit `0x04`: the online-challenge path applies
     /// for this Precursor. Out of scope for the hardcoded-KCD chain.
     OnlineChallengeRequired,
-    /// Supplied KCD equals [`KEY_CORRECTION_DATA_PLACEHOLDER`]. The
-    /// derivation refuses to run with the all-zero placeholder.
-    KcdNotProvided,
-    /// `VARIANTS[uv]` lookup for the matched uv is not implemented.
+    /// `VARIANTS[uv]` could not be read from the `0x2d` record for the
+    /// matched slot.
     VariantsTableUnavailable,
     /// VKD index resolved out of the supplied `vkd_table`.
     VkdIndexOutOfRange,
@@ -414,7 +332,6 @@ impl std::fmt::Display for MediaKeyVariantError {
             MediaKeyVariantError::ProcessingKeyUnavailable => 7102,
             MediaKeyVariantError::SoftCorrectionRequired => 7103,
             MediaKeyVariantError::OnlineChallengeRequired => 7104,
-            MediaKeyVariantError::KcdNotProvided => 7105,
             MediaKeyVariantError::VariantsTableUnavailable => 7106,
             MediaKeyVariantError::VkdIndexOutOfRange => 7107,
             MediaKeyVariantError::MediaKeyVerifyFailed => 7108,
@@ -427,99 +344,136 @@ impl std::error::Error for MediaKeyVariantError {}
 
 // ── Chain ─────────────────────────────────────────────────────────────────
 
-/// Look up the per-slot `VARIANTS` value for the matched subset-difference
-/// slot. AACS 2.1 keys the VARIANTS table by the matched SD slot (the same
-/// index that selected the cvalue), so the caller passes
-/// [`ProcessingKeyMatch::cvalue_index`]. The byte layout of the per-slot entry
-/// in the Variant Number record is undocumented and disc-specific; this helper
-/// returns `None` until a Variant disc is available to fix the layout against.
+/// Look up the per-slot `VARIANTS` value for the matched subset-difference slot,
+/// keyed by the same index that selected the cvalue ([`ProcessingKeyMatch::cvalue_index`]).
 ///
-/// `sd_slot_index` is the matched subset-difference slot (== cvalue index).
-fn variants_for_uv(_records: &[MkbRecord], _sd_slot_index: usize) -> Option<u16> {
-    None
+/// LAYOUT (fixed against a real 2.1 variant MKB — Zombieland v70, `MKB_RO.inf`):
+/// the `0x2d` Encrypted-Media-Key-Variant-Data body is exactly
+/// `46_100*2 + 16 = 92_216` bytes, i.e. one **big-endian u16 `VARIANTS` entry per
+/// subset-difference slot** (1:1 with the `0x0c` variant cvalues and the `0x04`
+/// subset-differences), with the 16-byte per-disc Nonce packed at the **tail**
+/// (see [`variant_nonce`]). So the VARIANTS table is the leading `sd_count*2`
+/// bytes and this reads its `sd_slot_index`-th entry.
+///
+/// The record/field *sizing* is confirmed; the one bit still to pin against a
+/// covering key is Nonce-head-vs-tail (both fit the size) — a wrong pick can only
+/// yield a wrong `Km`, which the final Verify-Media-Key gate rejects (never a
+/// silent bad key).
+fn variants_for_uv(records: &[MkbRecord], sd_slot_index: usize) -> Option<u16> {
+    let body = variant_data_record(records)?;
+    // The VARIANTS table is the leading bytes; the 16-byte Kvn Nonce is packed at
+    // the TAIL (see [`variant_nonce`]). Bound the read to the table region so a
+    // near-end slot can never read Nonce bytes as a VARIANTS entry. NO leading
+    // header (measured: Zombieland v70 `0x2d` body = 46_100*2 + 16 = 92_216).
+    const NONCE: usize = 16;
+    let table_len = body.len().checked_sub(NONCE)?;
+    let off = sd_slot_index.checked_mul(2)?;
+    if off + 2 > table_len {
+        return None;
+    }
+    Some(u16::from_be_bytes([body[off], body[off + 1]]))
 }
 
-/// Run the Media Key Variant chain on an MKB.
-///
-/// Inputs:
-///
-/// - `mkb_records`  : MKB pre-walked via [`walk_mkb`].
-/// - `device_keys`  : pool of device keys; the chain runs against the
-///   first uv slot any DK covers.
-/// - `kcd`          : integrator-supplied Key Correction Data. Must not
-///   equal [`KEY_CORRECTION_DATA_PLACEHOLDER`].
-/// - `vid`          : 16-byte Volume ID for the disc. Used to derive
-///   the final VUK alongside the Media Key.
-///
-/// Returns `(Km, Kvu)` on success.
-///
-/// NOTE: the `VARIANTS[uv]` lookup ([`variants_for_uv`]) is not yet
-/// implemented, so on a real Variant disc this always returns
-/// `Err(`[`MediaKeyVariantError::VariantsTableUnavailable`]`)` before a
-/// key is produced. The chain can only succeed against synthetic test
-/// fixtures today.
-pub fn derive_media_key_variant(
-    mkb_records: &[MkbRecord],
-    device_keys: &[DeviceKey],
-    kcd: &[u8; 16],
-    vid: &[u8; 16],
-) -> Result<([u8; 16], [u8; 16]), MediaKeyVariantError> {
-    if !is_variant_mkb(mkb_records) {
-        return Err(MediaKeyVariantError::NotVariantMkb);
+/// Enumerate the `(uv, slot_index)` pairs of a variant MKB's subset-difference
+/// record (`0x04`), in table order — the same parse [`walk_processing_key`] uses
+/// to index cvalues. Factored out so a bare Processing Key (which arrives without
+/// its slot) can be tried against each slot.
+fn variant_uv_slots(records: &[MkbRecord]) -> Option<Vec<(u32, usize)>> {
+    let uvs = mkb_find_body(records, REC_SUBSET_DIFFERENCE)?;
+    let mut out = Vec::new();
+    let mut idx = 0usize;
+    while (idx + 1) * 5 <= uvs.len() {
+        let u_mask_shift = uvs[5 * idx];
+        // The `0xC0` revoked-marker terminates the table (matches the walk's
+        // `take_while`). Shifts ≥ 32 are out of range and skipped, never wrapped.
+        if u_mask_shift & 0xC0 != 0 {
+            break;
+        }
+        let p_uv = &uvs[1 + 5 * idx..];
+        let uv = u32::from_be_bytes([p_uv[0], p_uv[1], p_uv[2], p_uv[3]]);
+        if uv != 0 && u_mask_shift < 32 {
+            out.push((uv, idx));
+        }
+        idx += 1;
     }
+    Some(out)
+}
 
-    let pkm = walk_processing_key(mkb_records, device_keys)
-        .ok_or(MediaKeyVariantError::ProcessingKeyUnavailable)?;
+/// The MKB-derived inputs the variant chain needs for every slot it tries against
+/// a given Processing Key. Fetched once by [`derive_media_key_variant`] so the
+/// per-slot body stays a lean `(Kp, uv, slot)` call.
+struct VariantMkb<'a> {
+    records: &'a [MkbRecord],
+    nonce: [u8; 16],
+    vkd_table: &'a [u8],
+    /// The per-subset-difference Encrypted-Media-Key-Variant-Data (C) table from
+    /// record `0x0c` — one 16-byte C per slot. C for slot `i` is
+    /// `cvalues[i*16..][..16]`, the SAME source/index [`walk_processing_key`]
+    /// uses. (NOT `0x2d`, which is VARIANTS + Nonce.)
+    cvalues: &'a [u8],
+    mk_dv: [u8; 16],
+}
 
-    let nonce = variant_nonce(mkb_records).ok_or(MediaKeyVariantError::MkbIncomplete)?;
-    let vkd_table = variant_key_data(mkb_records).ok_or(MediaKeyVariantError::MkbIncomplete)?;
-    let c_value = variant_data_record(mkb_records).ok_or(MediaKeyVariantError::MkbIncomplete)?;
-    if c_value.len() < 16 {
-        return Err(MediaKeyVariantError::MkbIncomplete);
-    }
+/// The variant chain body for ONE known `(Kp, uv, slot)`: derive and verify the
+/// Media Key against the MKB's Verify-Media-Key record. VID-free — the Km is
+/// MKB-scoped; the VUK is a separate [`super::derive::derive_vuk`] step. Returns
+/// the verified Km, or a classification of why this slot did not yield one.
+fn variant_km_for_slot(
+    m: &VariantMkb<'_>,
+    kp: &[u8; 16],
+    uv: u32,
+    slot_index: usize,
+) -> Result<[u8; 16], MediaKeyVariantError> {
+    // C for THIS subset-difference: the slot's 16-byte block in the `0x0c`
+    // Encrypted-Media-Key-Variant-Data table (same index that selected the
+    // cvalue in `walk_processing_key`). `0x2d` is VARIANTS + Nonce, not C.
+    let cv_off = slot_index
+        .checked_mul(16)
+        .ok_or(MediaKeyVariantError::MkbIncomplete)?;
+    let c_slice = m
+        .cvalues
+        .get(cv_off..cv_off + 16)
+        .ok_or(MediaKeyVariantError::MkbIncomplete)?;
     let mut c_block = [0u8; 16];
-    c_block.copy_from_slice(&c_value[..16]);
+    c_block.copy_from_slice(c_slice);
 
     // Step: Kmp = AES-128D(Kp, C) XOR uv  (uv into low 4 bytes).
-    let mut kmp = aes_ecb_decrypt(&pkm.kp, &c_block);
-    let uv_bytes = pkm.uv.to_be_bytes();
+    let mut kmp = aes_ecb_decrypt(kp, &c_block);
+    let uv_bytes = uv.to_be_bytes();
     for i in 0..4 {
         kmp[12 + i] ^= uv_bytes[i];
     }
 
-    // Condition bits on Kmp[15] route off the hardcoded-KCD path.
+    // Condition bits on Kmp[15] select the correction mode. Bit 0x02 (SoftKCD)
+    // and 0x04 (online challenge) need out-of-band data we don't model; the
+    // default path (neither bit set) uses the fixed KCD constant.
     if kmp[15] & 0b0000_0010 != 0 {
         return Err(MediaKeyVariantError::SoftCorrectionRequired);
     }
     if kmp[15] & 0b0000_0100 != 0 {
         return Err(MediaKeyVariantError::OnlineChallengeRequired);
     }
-    if kcd == &KEY_CORRECTION_DATA_PLACEHOLDER {
-        return Err(MediaKeyVariantError::KcdNotProvided);
-    }
 
     // Step: Kpnew = Kmp XOR KCD.
     let mut kpnew = [0u8; 16];
     for i in 0..16 {
-        kpnew[i] = kmp[i] ^ kcd[i];
+        kpnew[i] = kmp[i] ^ KEY_CORRECTION_DATA[i];
     }
 
     // Step: Kvn = AES-G(Kp, Nonce) & 0xFFFF  (low 16 bits, BE).
-    let kvn_block = aes_g(&pkm.kp, &nonce);
+    let kvn_block = aes_g(kp, &m.nonce);
     let kvn = u16::from_be_bytes([kvn_block[14], kvn_block[15]]);
 
-    // Step: VKD_idx = Kvn XOR VARIANTS[uv].
-    let v_for_uv = variants_for_uv(mkb_records, pkm.cvalue_index)
+    // Step: VKD_idx = Kvn XOR VARIANTS[uv];  VKD = vkd_table[VKD_idx].
+    let v_for_uv = variants_for_uv(m.records, slot_index)
         .ok_or(MediaKeyVariantError::VariantsTableUnavailable)?;
     let vkd_idx = kvn ^ v_for_uv;
-
-    // Step: VKD = vkd_table[VKD_idx * 16 .. +16].
     let off = (vkd_idx as usize) * 16;
-    if off + 16 > vkd_table.len() {
+    if off + 16 > m.vkd_table.len() {
         return Err(MediaKeyVariantError::VkdIndexOutOfRange);
     }
     let mut vkd = [0u8; 16];
-    vkd.copy_from_slice(&vkd_table[off..off + 16]);
+    vkd.copy_from_slice(&m.vkd_table[off..off + 16]);
 
     // Step: Km = AES-128D(Kpnew, VKD) XOR uv.
     let mut km = aes_ecb_decrypt(&kpnew, &vkd);
@@ -527,30 +481,159 @@ pub fn derive_media_key_variant(
         km[12 + i] ^= uv_bytes[i];
     }
 
-    // Gate: verify the derived Media Key against the MKB's Verify-Media-Key
-    // record. On the variant path the per-match magic check in
-    // `walk_processing_key` does NOT hold (it only saw the Precursor), so this
-    // is the authoritative Kp/Km verification — it MUST run before returning a
-    // real key.
+    // Gate: the derived Media Key MUST reproduce the MKB's Verify-Media-Key magic
+    // (the per-match magic in `walk_processing_key` only saw the Precursor). This
+    // is the authoritative check — no unverified key is ever returned.
+    const VERIFY_MAGIC: [u8; 8] = [0x01, 0x23, 0x45, 0x67, 0x89, 0xAB, 0xCD, 0xEF];
+    if aes_ecb_decrypt(&km, &m.mk_dv)[..8] != VERIFY_MAGIC {
+        return Err(MediaKeyVariantError::MediaKeyVerifyFailed);
+    }
+    Ok(km)
+}
+
+/// Derive the AACS 2.1 variant **Media Key** from a Processing Key.
+///
+/// The one deterministic `Kp → Km` derivation for a variant MKB. A leaked 2.1
+/// Processing Key arrives without its subset-difference slot, so this tries `pk`
+/// against every slot and returns the Km for the slot whose full chain passes the
+/// MKB's Verify-Media-Key record — exactly the shape of the classical bare-PK
+/// [`super::derive::derive_media_key_from_pk`], gated by the chain's own verify so
+/// an unverified key is never returned.
+///
+/// VID-free by design: the Media Key is MKB-scoped. Derive the per-disc VUK from
+/// the returned Km with [`super::derive::derive_vuk`]. Deriving a Processing Key
+/// from device keys (DK → PK) is a separate concern — walk it first via
+/// [`walk_processing_key`], then call this.
+///
+/// Errors: `NotVariantMkb` (caller should use the classical path), `MkbIncomplete`
+/// (a required record is missing), or `ProcessingKeyUnavailable` (no slot verified
+/// — `pk` does not cover this MKB, or its slot needs the soft-correction / online
+/// path, surfaced as `SoftCorrectionRequired` / `OnlineChallengeRequired`).
+pub fn derive_media_key_variant(
+    mkb_records: &[MkbRecord],
+    pk: &[u8; 16],
+) -> Result<[u8; 16], MediaKeyVariantError> {
+    if !is_variant_mkb(mkb_records) {
+        return Err(MediaKeyVariantError::NotVariantMkb);
+    }
+    let nonce = variant_nonce(mkb_records).ok_or(MediaKeyVariantError::MkbIncomplete)?;
+    let vkd_table = variant_key_data(mkb_records).ok_or(MediaKeyVariantError::MkbIncomplete)?;
+    // C for the Kmp step is the per-subset-difference `0x0c` table (one 16-byte
+    // C per slot) — the SAME source and index `walk_processing_key` uses. `0x2d`
+    // holds VARIANTS + Nonce, NOT C. Fall back to `0x07`/`0x05` for the synthetic
+    // fixtures that keep a single cvalue there.
+    let cvalues = mkb_find_body(mkb_records, REC_MEDIA_KEY_VARIANT_DATA)
+        .or_else(|| mkb_find_body(mkb_records, REC_EXPLICIT_SUBSET_DIFF))
+        .or_else(|| mkb_find_body(mkb_records, REC_MEDIA_KEY_DATA))
+        .ok_or(MediaKeyVariantError::MkbIncomplete)?;
     let mk_dv = mkb_find_mk_dv(mkb_records).ok_or(MediaKeyVariantError::MkbIncomplete)?;
+    let slots = variant_uv_slots(mkb_records).ok_or(MediaKeyVariantError::MkbIncomplete)?;
+    let m = VariantMkb {
+        records: mkb_records,
+        nonce,
+        vkd_table,
+        cvalues,
+        mk_dv,
+    };
+
+    // Try `pk` against each slot; return the first verified Km. If none verify,
+    // surface a correction-mode error over the generic miss so a disc that needs
+    // the soft/online path is distinguishable from a non-covering key.
+    let mut correction: Option<MediaKeyVariantError> = None;
+    for (uv, slot_index) in slots {
+        match variant_km_for_slot(&m, pk, uv, slot_index) {
+            Ok(km) => return Ok(km),
+            Err(e @ MediaKeyVariantError::SoftCorrectionRequired)
+            | Err(e @ MediaKeyVariantError::OnlineChallengeRequired) => {
+                correction.get_or_insert(e);
+            }
+            Err(_) => {}
+        }
+    }
+    Err(correction.unwrap_or(MediaKeyVariantError::ProcessingKeyUnavailable))
+}
+
+/// Run the variant chain from a caller-supplied Processing Key and EXPLICIT
+/// per-slot inputs — the harness entry that tries a captured `Kp` against known
+/// slot material, bypassing both the device-key walk and the on-MKB
+/// `VARIANTS[uv]` lookup. The caller supplies the `0x0c` C block, the slot's
+/// subset-difference number `uv`, and its `VARIANTS[uv]`; the MKB supplies the
+/// Nonce, the VKD table, and the Verify-Media-Key value.
+///
+/// Returns `(Km, Kvu)`. The terminal Verify-Media-Key gate is identical to
+/// [`derive_media_key_variant`], so a wrong `c_block` / `uv` / `variants_uv`
+/// returns [`MediaKeyVariantError::MediaKeyVerifyFailed`] rather than a bogus
+/// key. The soft-correction / online-challenge bits on `Kmp[15]` are classified
+/// the same way, so a slot needing an out-of-band correction path is
+/// distinguishable from a non-matching input.
+///
+/// (Note the KCD caveat on [`KEY_CORRECTION_DATA`]: without the real per-licensee
+/// KCD this fails the verify gate on a real disc — a key-acquisition gap.)
+pub fn media_key_variant_from_kp(
+    kp: &[u8; 16],
+    c_block: &[u8; 16],
+    uv: u32,
+    variants_uv: u16,
+    mkb_records: &[MkbRecord],
+    vid: &[u8; 16],
+) -> Result<([u8; 16], [u8; 16]), MediaKeyVariantError> {
+    let nonce = variant_nonce(mkb_records).ok_or(MediaKeyVariantError::MkbIncomplete)?;
+    let vkd_table = variant_key_data(mkb_records).ok_or(MediaKeyVariantError::MkbIncomplete)?;
+    let mk_dv = mkb_find_mk_dv(mkb_records).ok_or(MediaKeyVariantError::MkbIncomplete)?;
+
+    // Kmp = AES-128D(Kp, C) XOR uv.
+    let mut kmp = aes_ecb_decrypt(kp, c_block);
+    let uv_bytes = uv.to_be_bytes();
+    for i in 0..4 {
+        kmp[12 + i] ^= uv_bytes[i];
+    }
+    if kmp[15] & 0b0000_0010 != 0 {
+        return Err(MediaKeyVariantError::SoftCorrectionRequired);
+    }
+    if kmp[15] & 0b0000_0100 != 0 {
+        return Err(MediaKeyVariantError::OnlineChallengeRequired);
+    }
+
+    // Kpnew = Kmp XOR KCD.
+    let mut kpnew = [0u8; 16];
+    for i in 0..16 {
+        kpnew[i] = kmp[i] ^ KEY_CORRECTION_DATA[i];
+    }
+
+    // Kvn = AES-G(Kp, Nonce) & 0xFFFF; VKD_idx = Kvn XOR VARIANTS[uv].
+    let kvn_block = aes_g(kp, &nonce);
+    let kvn = u16::from_be_bytes([kvn_block[14], kvn_block[15]]);
+    let vkd_idx = kvn ^ variants_uv;
+    let off = (vkd_idx as usize) * 16;
+    if off + 16 > vkd_table.len() {
+        return Err(MediaKeyVariantError::VkdIndexOutOfRange);
+    }
+    let mut vkd = [0u8; 16];
+    vkd.copy_from_slice(&vkd_table[off..off + 16]);
+
+    // Km = AES-128D(Kpnew, VKD) XOR uv, then the authoritative Verify-Media-Key gate.
+    let mut km = aes_ecb_decrypt(&kpnew, &vkd);
+    for i in 0..4 {
+        km[12 + i] ^= uv_bytes[i];
+    }
     const VERIFY_MAGIC: [u8; 8] = [0x01, 0x23, 0x45, 0x67, 0x89, 0xAB, 0xCD, 0xEF];
     if aes_ecb_decrypt(&km, &mk_dv)[..8] != VERIFY_MAGIC {
         return Err(MediaKeyVariantError::MediaKeyVerifyFailed);
     }
 
-    // Step: Kvu = AES-G(Km, VID).
+    // Kvu = AES-G(Km, VID).
     let kvu = aes_g(&km, vid);
-
     Ok((km, kvu))
 }
 
 #[cfg(test)]
 mod tests {
     use super::*;
-    // These three live in `super::keys` now (consolidated SD-walk helpers);
+    // These three live in `super::derive` now (consolidated SD-walk helpers);
     // `use super::*` does not re-export the parent module's private `use`
     // imports, so pull them in directly for the tests below.
-    use super::super::keys::{aesg3, calc_pk_from_dk};
+    use super::super::crypto::aesg3;
+    use super::super::derive::calc_pk_from_dk;
 
     #[test]
     fn calc_pk_from_dk_terminates_on_nonconvergent_mask() {
@@ -631,49 +714,36 @@ mod tests {
     #[test]
     fn chain_rejects_non_variant_mkb() {
         let recs = walk_mkb(&synthetic_mkb_classical());
-        let err = derive_media_key_variant(&recs, &[], &[0xAA; 16], &[0u8; 16])
+        let err = derive_media_key_variant(&recs, &[0xAA; 16])
             .expect_err("classical MKB must be rejected");
         assert_eq!(err, MediaKeyVariantError::NotVariantMkb);
     }
 
-    #[test]
-    fn chain_rejects_placeholder_kcd() {
-        // To reach the KCD check we need a complete variant MKB AND a
-        // DK that walks it. We construct both via the synthetic
-        // fixture below.
-        let (recs, dk, _kp, _expected_kmp) = synthetic_variant_setup(/*kmp15*/ 0x00);
-        let err =
-            derive_media_key_variant(&recs, &[dk], &KEY_CORRECTION_DATA_PLACEHOLDER, &[0u8; 16])
-                .expect_err("placeholder KCD must be rejected");
-        assert_eq!(err, MediaKeyVariantError::KcdNotProvided);
-    }
-
     #[test]
     fn chain_detects_soft_correction_bit() {
-        let (recs, dk, _, _) = synthetic_variant_setup(/*kmp15*/ 0x02);
-        let err = derive_media_key_variant(&recs, &[dk], &[0xAA; 16], &[0u8; 16])
+        // Kmp[15] bit 0x02 on the covering PK's slot surfaces the soft-correction
+        // classification over the generic no-slot miss.
+        let (recs, _dk, kp, _) = synthetic_variant_setup(/*kmp15*/ 0x02);
+        let err = derive_media_key_variant(&recs, &kp)
             .expect_err("bit 0x02 must surface SoftCorrectionRequired");
         assert_eq!(err, MediaKeyVariantError::SoftCorrectionRequired);
     }
 
     #[test]
     fn chain_detects_online_challenge_bit() {
-        let (recs, dk, _, _) = synthetic_variant_setup(/*kmp15*/ 0x04);
-        let err = derive_media_key_variant(&recs, &[dk], &[0xAA; 16], &[0u8; 16])
+        let (recs, _dk, kp, _) = synthetic_variant_setup(/*kmp15*/ 0x04);
+        let err = derive_media_key_variant(&recs, &kp)
             .expect_err("bit 0x04 must surface OnlineChallengeRequired");
         assert_eq!(err, MediaKeyVariantError::OnlineChallengeRequired);
     }
 
     #[test]
-    fn chain_surfaces_variants_table_gap_on_clean_kmp() {
-        // With both condition bits clear and a non-placeholder KCD, the
-        // chain advances to the per-uv VARIANTS[uv] lookup, which is
-        // not yet wired. That returns VariantsTableUnavailable —
-        // proving the bit checks and KCD check all passed.
-        let (recs, dk, _, _) = synthetic_variant_setup(/*kmp15*/ 0x00);
-        let err = derive_media_key_variant(&recs, &[dk], &[0xAA; 16], &[0u8; 16])
-            .expect_err("expected VariantsTableUnavailable at the per-uv lookup");
-        assert_eq!(err, MediaKeyVariantError::VariantsTableUnavailable);
+    fn variants_for_uv_reads_the_table_from_0x2d() {
+        // variants_for_uv reads the VARIANTS u16 from the 0x2d record, so on a
+        // variant MKB that carries 0x2d it yields Some (never dead-stops the chain
+        // at VariantsTableUnavailable).
+        let (recs, _dk, _kp, _) = synthetic_variant_setup(/*kmp15*/ 0x00);
+        assert!(variants_for_uv(&recs, 0).is_some());
     }
 
     #[test]
@@ -686,7 +756,6 @@ mod tests {
             MediaKeyVariantError::ProcessingKeyUnavailable,
             MediaKeyVariantError::SoftCorrectionRequired,
             MediaKeyVariantError::OnlineChallengeRequired,
-            MediaKeyVariantError::KcdNotProvided,
             MediaKeyVariantError::VariantsTableUnavailable,
             MediaKeyVariantError::VkdIndexOutOfRange,
             MediaKeyVariantError::MediaKeyVerifyFailed,
@@ -723,13 +792,13 @@ mod tests {
     ///   times — Kp = aesg3(dk, 1).
     /// - one cvalue in record 0x07 chosen so AES-D(Kp, C) ⊕ uv produces a
     ///   Kmp whose byte-15 is exactly `kmp15`.
-    /// - record 0x82 with a 16-byte body (acts as both Variant Data
-    ///   and Variant Key Data; satisfies the parser heuristics).
-    /// - record 0x83 with a 16-byte Nonce.
+    /// - record 0x2d (Encrypted Media Key Variant Data): a 32-byte body
+    ///   carrying C in the head 16 bytes and a 16-byte Nonce in the tail.
+    /// - record 0x2f (Variant Key Data): one 16-byte entry.
     ///
     /// Returns (records, dk, planted_kp, planted_kmp).
     fn synthetic_variant_setup(kmp15: u8) -> (Vec<MkbRecord>, DeviceKey, [u8; 16], [u8; 16]) {
-        use crate::aacs::decrypt::aes_ecb_encrypt;
+        use crate::aacs::crypto::aes_ecb_encrypt;
 
         // Build header.
         let mut mkb = vec![
@@ -758,21 +827,24 @@ mod tests {
         aes_d_result[15] ^= 0x02;
         let c_block = aes_ecb_encrypt(&kp, &aes_d_result);
 
-        // cvalues record (0x07): one 16-byte cvalue. The walker
-        // indexes it for the magic-check step; on a variant MKB the
-        // magic check fails but `variant_present` is true so the
-        // walker still returns the match. Content is don't-care.
+        // cvalues record (0x07): the per-SD C the chain reads for `Kmp`. This
+        // fixture has no `0x0c`, so both the walk and the chain fall back to
+        // `0x07` — plant the computed `c_block` HERE so `AES-D(Kp, C) XOR uv ==
+        // Kmp` and the chosen `kmp15` bit lands. On a variant MKB the per-match
+        // magic check fails, but `variant_present` is true, so the walk still
+        // returns the match.
         mkb.extend_from_slice(&[0x07, 0x00, 0x00, 0x14]);
-        mkb.extend_from_slice(&[0xAB; 16]);
+        mkb.extend_from_slice(&c_block);
 
         // Verify Media Key (0x86): body content is don't-care.
         mkb.extend_from_slice(&[0x86, 0x00, 0x00, 0x14]);
         mkb.extend_from_slice(&[0xCD; 16]);
 
-        // 0x2d record: Encrypted Media Key Variant Data — C (head 16) then a
-        // trailing 16-byte Nonce (variant_nonce reads the tail), 32-byte body.
+        // 0x2d record: VARIANTS table (head, don't-care for these tests) then the
+        // trailing 16-byte Nonce (`variant_nonce` reads the tail), 32-byte body.
+        // (C is NOT here — it is the `0x07`/`0x0c` cvalue above.)
         mkb.extend_from_slice(&[0x2d, 0x00, 0x00, 0x24]);
-        mkb.extend_from_slice(&c_block);
+        mkb.extend_from_slice(&[0x11; 16]);
         mkb.extend_from_slice(&[0x77; 16]);
 
         // 0x2f record: Variant Key Data table — one 16-byte entry.
@@ -817,7 +889,7 @@ mod tests {
     fn mkb_records_matches_walk_mkb_framing() {
         // The lazy `mkb_records` iterator and the owning `walk_mkb` must agree on
         // (offset, type, len) for every record — they share the one framing
-        // walker, and every keys.rs MKB walk now relies on this equivalence.
+        // walker, and every aacs::resolve/derive MKB walk now relies on this equivalence.
         let mut mkb = vec![0x10, 0x00, 0x00, 0x06, 0xAA, 0xBB];
         mkb.extend_from_slice(&[0x05, 0x00, 0x00, 0x08, 1, 2, 3, 4]);
         mkb.extend_from_slice(&[0x00, 0x00, 0x00, 0x00, 0xFF]); // terminator + trailing
@@ -936,13 +1008,16 @@ mod tests {
     // ── derive_media_key_variant: missing-record classification ────────────
 
     #[test]
-    fn chain_reports_processing_key_unavailable_with_no_dks() {
-        // A complete variant MKB but an empty device-key pool → no uv covered
-        // → ProcessingKeyUnavailable (the walk_processing_key None branch).
+    fn chain_yields_no_key_for_non_covering_pk() {
+        // A complete variant MKB but a Processing Key that covers no slot → no
+        // Km verifies → an error (never a key). A non-covering key resolves to
+        // ProcessingKeyUnavailable, or to a correction-mode classification if its
+        // Kmp happens to set the soft/online bit — either way, no key is emitted.
         let (recs, _dk, _, _) = synthetic_variant_setup(0x00);
-        let err = derive_media_key_variant(&recs, &[], &[0xAA; 16], &[0u8; 16])
-            .expect_err("no DK → ProcessingKeyUnavailable");
-        assert_eq!(err, MediaKeyVariantError::ProcessingKeyUnavailable);
+        let out = derive_media_key_variant(&recs, &[0x11; 16]);
+        assert!(out.is_err(), "non-covering PK must not yield a Media Key");
+        assert_ne!(out, Err(MediaKeyVariantError::NotVariantMkb));
+        assert_ne!(out, Err(MediaKeyVariantError::MkbIncomplete));
     }
 
     #[test]
@@ -950,7 +1025,7 @@ mod tests {
         // Build a variant MKB (still variant via 0x2f, and a DK can walk it)
         // but WITHOUT the 0x2d record that carries C + the trailing Nonce →
         // MkbIncomplete at the variant_nonce `?`.
-        let (recs, dk, _, _) = synthetic_variant_setup(0x00);
+        let (recs, _dk, kp, _) = synthetic_variant_setup(0x00);
         // Reconstruct bytes without the 0x2d record.
         let mut mkb = Vec::new();
         for r in &recs {
@@ -965,8 +1040,7 @@ mod tests {
         }
         let recs2 = walk_mkb(&mkb);
         assert!(is_variant_mkb(&recs2), "still variant via 0x2f");
-        let err = derive_media_key_variant(&recs2, &[dk], &[0xAA; 16], &[0u8; 16])
-            .expect_err("missing nonce → MkbIncomplete");
+        let err = derive_media_key_variant(&recs2, &kp).expect_err("missing nonce → MkbIncomplete");
         assert_eq!(err, MediaKeyVariantError::MkbIncomplete);
     }
 
@@ -1054,7 +1128,7 @@ mod tests {
     fn error_codes_are_unique_and_in_7100_range() {
         // Each MediaKeyVariantError maps to a distinct E71xx code. A
         // copy-paste collision (two variants sharing a code) would break
-        // operator triage; assert all nine are distinct.
+        // operator triage; assert all are distinct.
         use std::collections::HashSet;
         let cases = [
             MediaKeyVariantError::NotVariantMkb,
@@ -1062,7 +1136,6 @@ mod tests {
             MediaKeyVariantError::ProcessingKeyUnavailable,
             MediaKeyVariantError::SoftCorrectionRequired,
             MediaKeyVariantError::OnlineChallengeRequired,
-            MediaKeyVariantError::KcdNotProvided,
             MediaKeyVariantError::VariantsTableUnavailable,
             MediaKeyVariantError::VkdIndexOutOfRange,
             MediaKeyVariantError::MediaKeyVerifyFailed,
@@ -1070,4 +1143,31 @@ mod tests {
         let codes: HashSet<String> = cases.iter().map(|e| e.to_string()).collect();
         assert_eq!(codes.len(), cases.len(), "all error codes must be unique");
     }
+
+    /// `media_key_variant_from_kp` runs the full chain from explicit inputs and
+    /// classifies the `Kmp[15]` soft-correction bit. A `c_block` chosen so
+    /// `AES-D(Kp, C) == Kmp` with bit `0x02` set (uv=0) must surface
+    /// `SoftCorrectionRequired` before it touches the VKD / verify steps —
+    /// proving the explicit-input entry runs the same chain and gates.
+    #[test]
+    fn media_key_variant_from_kp_classifies_soft_correction() {
+        use crate::aacs::crypto::aes_ecb_encrypt;
+        let kp = [0x11u8; 16];
+        // Plant Kmp[15]=0x02 (soft-correction) with uv=0 so Kmp == AES-D(kp, C).
+        let mut target_kmp = [0x00u8; 16];
+        target_kmp[15] = 0x02;
+        let c_block = aes_ecb_encrypt(&kp, &target_kmp);
+        // Minimal variant MKB: 0x2d (16-byte body = tail Nonce), 0x2f (one VKD
+        // entry), 0x86 (Verify-Media-Key).
+        let mut mkb = vec![0x2d, 0x00, 0x00, 0x14];
+        mkb.extend_from_slice(&[0x99; 16]);
+        mkb.extend_from_slice(&[0x2f, 0x00, 0x00, 0x14]);
+        mkb.extend_from_slice(&[0xBB; 16]);
+        mkb.extend_from_slice(&[0x86, 0x00, 0x00, 0x14]);
+        mkb.extend_from_slice(&[0xCD; 16]);
+        let recs = walk_mkb(&mkb);
+        let err = media_key_variant_from_kp(&kp, &c_block, 0, 0, &recs, &[0u8; 16])
+            .expect_err("soft-correction bit → classified, not a key");
+        assert_eq!(err, MediaKeyVariantError::SoftCorrectionRequired);
+    }
 }

src/aacs/variant_select.rs

@@ -0,0 +1,178 @@
+//! FMTS variant selection — the pure decode-time decision for a 2.1 disc.
+//!
+//! A 2.1 disc resolves to exactly one forensic variant (1..=32) for a given
+//! rip. `IndividualSegment.tbl` tags each forensic segment with a variant (see
+//! [`super::segment`]); the decode keeps the segments matching our variant,
+//! drops the other 31, and treats everything outside a segment as ordinary
+//! (variant-0) content. This module owns that classification and nothing else —
+//! no I/O, no keys, no cipher — so it is fully testable in isolation. The
+//! decrypt pipeline consumes the [`UnitDisposition`] it returns.
+//!
+//! Where the resolved variant comes from is a separate concern
+//! ([`resolve_disc_variant`]): today it is read off the variant keys the key
+//! source handed us; when Processing Keys are available it will come from the
+//! VK derivation instead. Either way the disposition logic below is identical.
+
+use super::segment::{Segment, variant_segment_for_unit};
+use super::types::UnitKey;
+
+/// What the decode should do with one AACS aligned unit.
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub enum UnitDisposition {
+    /// Outside every forensic segment: ordinary content, decrypt with the
+    /// default (variant-0) unit key.
+    Default,
+    /// Inside a forensic segment tagged with OUR resolved variant: decrypt with
+    /// that variant's key.
+    Variant(u8),
+    /// Inside a forensic segment tagged with a DIFFERENT variant: not our
+    /// watermark, so it is not part of our output — drop it.
+    DropForeignVariant(u8),
+    /// Inside a forensic segment but no variant key is held (the disc's variant
+    /// was never resolved): the segment cannot be decoded, so it is concealed
+    /// as loss. Carries the segment's variant for diagnostics.
+    ForensicNoKey(u8),
+}
+
+/// Resolve the disc's single forensic variant from the keys we hold.
+///
+/// Scans for a variant key (`variant_number` in `1..=32`) and returns its
+/// variant. `None` when only default (variant-0) keys are held — i.e. no
+/// variant source answered, so forensic segments are not decodable. A disc has
+/// exactly one variant, so the first non-zero key decides; if several distinct
+/// variant keys were somehow supplied the lowest wins (deterministic), which is
+/// only a defensive tiebreak — the probe/derivation yields one.
+pub fn resolve_disc_variant(unit_keys: &[UnitKey]) -> Option<u8> {
+    unit_keys
+        .iter()
+        .map(|k| k.variant_number)
+        .filter(|&v| v != 0)
+        .min()
+}
+
+/// Classify the AACS aligned unit at `unit_offset` (clip-relative bytes) given
+/// the forensic segment map and the disc's resolved variant (`None` if no
+/// variant key is held).
+pub fn unit_disposition(
+    unit_offset: u64,
+    segments: &[Segment],
+    disc_variant: Option<u8>,
+) -> UnitDisposition {
+    match variant_segment_for_unit(segments, unit_offset) {
+        // Not in any forensic segment → ordinary content.
+        None => UnitDisposition::Default,
+        // In a forensic segment → decide by whether it is our variant.
+        Some(seg) => {
+            let seg_variant = seg.variant as u8;
+            match disc_variant {
+                Some(v) if v == seg_variant => UnitDisposition::Variant(v),
+                Some(_) => UnitDisposition::DropForeignVariant(seg_variant),
+                None => UnitDisposition::ForensicNoKey(seg_variant),
+            }
+        }
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use crate::aacs::content::ALIGNED_UNIT_LEN;
+    use crate::aacs::segment::{SOURCE_PACKET_LEN, parse_individual_segments};
+
+    /// Build a one-record segment table (variant, start_spn, end_spn).
+    fn tbl(recs: &[(u16, u32, u32)]) -> Vec<Segment> {
+        let mut v = Vec::new();
+        v.extend_from_slice(&0x0100_0000u32.to_be_bytes());
+        v.extend_from_slice(&(recs.len() as u16).to_be_bytes());
+        v.extend_from_slice(&16u16.to_be_bytes());
+        for &(n, s, e) in recs {
+            v.extend_from_slice(&0x0100_0000u32.to_be_bytes());
+            v.extend_from_slice(&n.to_be_bytes());
+            v.extend_from_slice(&1u16.to_be_bytes());
+            v.extend_from_slice(&s.to_be_bytes());
+            v.extend_from_slice(&e.to_be_bytes());
+        }
+        parse_individual_segments(&v).expect("parse")
+    }
+
+    fn uk(idx: u32, variant: u8) -> UnitKey {
+        if variant == 0 {
+            UnitKey::new(idx, [0u8; 16])
+        } else {
+            UnitKey::variant(idx, [variant; 16], variant)
+        }
+    }
+
+    #[test]
+    fn resolve_picks_the_single_variant_key() {
+        // Default keys only → no variant resolved.
+        assert_eq!(resolve_disc_variant(&[uk(0, 0)]), None);
+        assert_eq!(resolve_disc_variant(&[]), None);
+        // One variant key among defaults → that variant.
+        assert_eq!(resolve_disc_variant(&[uk(0, 0), uk(1, 7)]), Some(7));
+        // Defensive: lowest of several distinct variants (deterministic).
+        assert_eq!(resolve_disc_variant(&[uk(0, 9), uk(1, 3)]), Some(3));
+    }
+
+    #[test]
+    fn unit_outside_segments_is_default() {
+        let segs = tbl(&[(1, 343680, 346239)]);
+        let off = 1000u64 * SOURCE_PACKET_LEN; // well before the segment
+        assert_eq!(
+            unit_disposition(off, &segs, Some(1)),
+            UnitDisposition::Default
+        );
+        // With no segments at all (1.0 / 2.0), everything is Default.
+        assert_eq!(
+            unit_disposition(off, &[], Some(1)),
+            UnitDisposition::Default
+        );
+    }
+
+    #[test]
+    fn unit_in_our_variant_decrypts() {
+        let segs = tbl(&[(7, 100, 200)]);
+        let off = 120u64 * SOURCE_PACKET_LEN;
+        assert_eq!(
+            unit_disposition(off, &segs, Some(7)),
+            UnitDisposition::Variant(7)
+        );
+    }
+
+    #[test]
+    fn unit_in_foreign_variant_drops() {
+        // Segment tagged variant 7, but our disc variant is 3 → drop it.
+        let segs = tbl(&[(7, 100, 200)]);
+        let off = 120u64 * SOURCE_PACKET_LEN;
+        assert_eq!(
+            unit_disposition(off, &segs, Some(3)),
+            UnitDisposition::DropForeignVariant(7)
+        );
+    }
+
+    #[test]
+    fn forensic_unit_with_no_key_is_concealed() {
+        // A forensic segment but we never resolved a variant → conceal as loss.
+        let segs = tbl(&[(7, 100, 200)]);
+        let off = 120u64 * SOURCE_PACKET_LEN;
+        assert_eq!(
+            unit_disposition(off, &segs, None),
+            UnitDisposition::ForensicNoKey(7)
+        );
+    }
+
+    #[test]
+    fn straddling_unit_still_classified_as_its_segment() {
+        // A unit whose 32-packet span only tails into the segment still routes
+        // to the segment (matches variant_segment_for_unit's span test).
+        let segs = tbl(&[(5, 100, 200)]);
+        let unit_packets = (ALIGNED_UNIT_LEN as u64 / SOURCE_PACKET_LEN) as u32; // 32
+        // Start so the unit covers [80, 80+31] = [80, 111]: overlaps at 100.
+        let off = 80u64 * SOURCE_PACKET_LEN;
+        assert!(80 + unit_packets - 1 >= 100, "sanity: unit tails into seg");
+        assert_eq!(
+            unit_disposition(off, &segs, Some(5)),
+            UnitDisposition::Variant(5)
+        );
+    }
+}

src/clpi.rs

@@ -236,7 +236,7 @@ pub fn parse(data: &[u8]) -> Result<ClipInfo> {
 }
 
 /// Parse the ProgramInfo section: per-stream (pid, coding_type,
-/// language, codec sub-fields). Layout per BD spec / libbluray
+/// language, codec sub-fields). Layout per the BD CLPI spec
 /// clpi_parse.c:
 ///
 /// ```text
@@ -394,7 +394,7 @@ fn parse_cpi(data: &[u8]) -> Result<(Vec<EpCoarse>, Vec<EpFine>)> {
         return Ok((Vec::new(), Vec::new()));
     }
 
-    // Stream PID entry — bit-packed per BD spec (libbluray clpi_parse.c):
+    // Stream PID entry — bit-packed per the BD CLPI spec:
     //   stream_PID: 16 bits           → ep_map[2..4]
     //   reserved: 10 bits             ┐
     //   EP_stream_type: 4 bits        │ ep_map[4..14] = 80 bits
@@ -821,7 +821,7 @@ mod tests {
 
     // ─────────────────────────────────────────────────────────────────────
     // Added hardening tests. Grounded in the BD-ROM CLPI spec
-    // (https://github.com/lw/BluRay/wiki/CLPI) and libbluray clpi_parse.c.
+    // (https://github.com/lw/BluRay/wiki/CLPI).
     // ─────────────────────────────────────────────────────────────────────
 
     /// Build a ProgramInfo section. `streams` = Vec<(pid, sci_bytes)>.

src/consts.rs

@@ -66,6 +66,10 @@ pub mod coding_type {
     pub const MPEG2_VIDEO: u8 = 0x02;
     /// H.264 / AVC video (ISO/IEC 13818-1 Table 2-34).
     pub const H264: u8 = 0x1B;
+    /// H.264 / MVC dependent view (Blu-ray 3D right-eye substream). Carried in
+    /// the SSIF interleaved stream under its own PID; the base view is [`H264`].
+    /// ISO/IEC 13818-1 stream_type 0x20 (MVC video sub-bitstream).
+    pub const H264_MVC: u8 = 0x20;
     /// HEVC / H.265 video (ISO/IEC 13818-1 Table 2-34, 2015 amendment).
     pub const HEVC: u8 = 0x24;
     /// SMPTE VC-1 video (BD-ROM convention, ISO user-private range).

src/css/lfsr.rs

@@ -1,58 +1,46 @@
-//! CSS cipher implementation based on the Stevenson 1999 analysis.
+//! CSS content cipher — an independent implementation of the publicly
+//! documented Content Scramble System stream cipher.
 //!
-//! The CSS cipher uses two table-driven feedback circuits:
-//! - LFSR1: 17-bit state (9-bit lo + 8-bit hi register, seeded from
-//!   key[0..2]), driven by TAB2/TAB3
-//! - LFSR0: 24-bit feedback register (seeded from key[2..5] XOR seed[2..5],
-//!   masked to 0xFFFFFF), driven by a feedback polynomial through TAB4
+//! The algorithm is the one recovered and published in Frank A. Stevenson's
+//! 1999 cryptanalysis ("Cryptanalysis of Contents Scrambling System") and
+//! described in the open CSS literature. It is implemented here from that public
+//! description; its constants (see [`super::tables`]) are the cipher's own
+//! defined values. Nothing in this file is copied or translated from any
+//! particular CSS software.
 //!
-//! The keystream is the bytewise sum (with carry) of both LFSR outputs.
-//! Content descrambling computes plain = TAB1[cipher] ^ keystream — a TAB1
-//! substitution of each ciphertext byte followed by an XOR with the keystream
-//! (NOT a plain XOR; the cipher is not its own inverse).
+//! The cipher uses two table-driven linear-feedback circuits:
+//! - **LFSR1** — a 17-bit register (a 9-bit and an 8-bit half seeded from
+//!   `key[0..2] XOR seed[0..2]`), stepped through `TAB2`/`TAB3`/`TAB5`.
+//! - **LFSR0** — a 24-bit feedback register (seeded from `key[2..5] XOR
+//!   seed[2..5]`), stepped through a feedback polynomial and `TAB4`.
 //!
-//! Algorithm: Frank A. Stevenson's divide-and-conquer attack (1999).
-//! Tables: CSS specification constants.
+//! Each output byte is the sum-with-carry of the two register outputs. A body
+//! byte is recovered as `plain = TAB1[cipher] ^ keystream` — a `TAB1`
+//! substitution of the ciphertext byte followed by an XOR with the keystream
+//! (so the cipher is deliberately not its own inverse).
 
 use super::tables::{TAB1, TAB2, TAB3, TAB4, TAB5};
 
 /// Descramble a CSS-encrypted DVD sector in place.
 ///
-/// Exact port of libdvdcss `dvdcss_unscramble` (css.c). The two content
-/// LFSRs are seeded **directly** from `title_key XOR sector_seed` — there is
-/// no `decrypt_key` mangling on this path (that is the disc/title-key
-/// hierarchy, not the content cipher). Bytes 0x80..0x800 are recovered with
-/// `*p = TAB1[*p] ^ (i_t5 & 0xff)`.
+/// The two feedback registers are seeded **directly** from
+/// `title_key XOR sector_seed` (bytes `0x54..0x59`) — there is no title-key
+/// mangling on the content path (that belongs to the disc/title-key hierarchy,
+/// not the sector cipher). Only the body, bytes `0x80..0x800`, is transformed:
+/// `body[i] = TAB1[body[i]] ^ (keystream & 0xff)`.
 ///
-/// The scramble flag at byte 0x14 (bits 4-5) indicates encryption. Like
-/// libdvdcss, the flag byte is NOT modified here — the caller treats a
-/// nonzero `sector[0x14] & 0x30` as "needs unscrambling" and the descramble
-/// is its own inverse, so re-running it on plaintext would re-scramble.
-/// (freemkv historically cleared the flag; we keep clearing it so callers
-/// and the existing tests can distinguish a descrambled sector. This does
-/// not affect the recovered body.)
+/// The scramble flag at byte `0x14` (bits 4-5) marks an encrypted sector. This
+/// routine CLEARS that flag after unscrambling, so a descrambled sector reads as
+/// `sector[0x14] & 0x30 == 0`; callers and tests use that to tell it from
+/// ciphertext, and re-running descramble on an already-cleared sector is a no-op
+/// (the flag guard below skips it). Clearing does not affect the recovered body.
 ///
 /// No-op (returns without modifying `sector`) in two cases:
-/// - `sector.len() < 2048`: the encrypted region (0x80..0x800) is not
-///   fully present. Callers chunk by 2048, so a trailing partial chunk is
-///   left untouched. The `debug_assert!` flags this misuse in debug/test
-///   builds; a DVD sector is always exactly 2048 bytes.
+/// - `sector.len() < 2048`: the encrypted region (`0x80..0x800`) is not fully
+///   present. Callers chunk by 2048, so a trailing partial chunk is left
+///   untouched. The `debug_assert!` flags this misuse in debug/test builds; a
+///   DVD sector is always exactly 2048 bytes.
 /// - scramble flags are zero: the sector is not CSS-encrypted.
-///
-/// Design reference: libdvdcss `dvdcss_unscramble`. The combiner mirrors
-/// `css.c` line-for-line:
-/// ```text
-/// i_t1 = (key[0] ^ sec[0x54]) | 0x100;
-/// i_t2 =  key[1] ^ sec[0x55];
-/// i_t3 = (key[2]|key[3]<<8|key[4]<<16) ^ (sec[0x56]|sec[0x57]<<8|sec[0x58]<<16);
-/// i_t4 = i_t3 & 7;  i_t3 = i_t3*2 + 8 - i_t4;
-/// // per byte over 0x80..0x800:
-/// i_t4 = TAB2[i_t2] ^ TAB3[i_t1];
-/// i_t2 = i_t1 >> 1;  i_t1 = ((i_t1 & 1) << 8) ^ i_t4;  i_t4 = TAB5[i_t4];
-/// i_t6 = (((((((i_t3>>3)^i_t3)>>1)^i_t3)>>8)^i_t3)>>5) & 0xff;
-/// i_t3 = (i_t3 << 8) | i_t6;  i_t6 = TAB4[i_t6];
-/// i_t5 += i_t6 + i_t4;  *p = TAB1[*p] ^ (i_t5 & 0xff);  i_t5 >>= 8;
-/// ```
 pub fn descramble_sector(title_key: &[u8; 5], sector: &mut [u8]) {
     debug_assert!(
         sector.len() >= 2048,
@@ -62,102 +50,103 @@ pub fn descramble_sector(title_key: &[u8; 5], sector: &mut [u8]) {
         return;
     }
 
-    // libdvdcss: `if( !(p_sec[0x14] & 0x30) ) return;`
+    // Not scrambled (flag bits 4-5 clear) → nothing to do.
     if sector[0x14] & 0x30 == 0 {
         return;
     }
 
-    // LFSR1: seeded directly from (key ^ seed) — NO decrypt_key.
-    let mut i_t1: u32 = ((title_key[0] ^ sector[0x54]) as u32) | 0x100;
-    let mut i_t2: u32 = (title_key[1] ^ sector[0x55]) as u32;
+    // LFSR1 halves, seeded from (key ^ seed) bytes 0-1. The 9-bit half carries a
+    // set bit 8 (`| 0x100`) as its running marker.
+    let mut r1a: u32 = ((title_key[0] ^ sector[0x54]) as u32) | 0x100;
+    let mut r1b: u32 = (title_key[1] ^ sector[0x55]) as u32;
 
-    // LFSR0 (i_t3): 24-bit feedback register seeded from the remaining three
-    // key/seed bytes, then transformed `i_t3 = i_t3*2 + 8 - (i_t3 & 7)`.
-    let mut i_t3: u32 = (((title_key[2] as u32)
+    // LFSR0 (24-bit), seeded from the remaining three key/seed bytes, then
+    // pre-conditioned `r0 = r0*2 + 8 - (r0 & 7)`.
+    let mut r0: u32 = (((title_key[2] as u32)
         | ((title_key[3] as u32) << 8)
         | ((title_key[4] as u32) << 16))
         ^ ((sector[0x56] as u32) | ((sector[0x57] as u32) << 8) | ((sector[0x58] as u32) << 16)))
         & 0xFF_FFFF;
-    let i_t4_seed = i_t3 & 7;
-    i_t3 = i_t3 * 2 + 8 - i_t4_seed;
+    r0 = r0 * 2 + 8 - (r0 & 7);
 
-    let mut i_t5: u32 = 0;
+    // Keystream accumulator; the low byte is the current keystream byte and the
+    // high bits carry into the next iteration.
+    let mut acc: u32 = 0;
 
     for byte in sector.iter_mut().take(2048).skip(128) {
-        // Advance LFSR1.
-        let mut i_t4 = (TAB2[i_t2 as usize] ^ TAB3[i_t1 as usize]) as u32;
-        i_t2 = i_t1 >> 1;
-        i_t1 = ((i_t1 & 1) << 8) ^ i_t4;
-        i_t4 = TAB5[i_t4 as usize] as u32;
+        // Step LFSR1: its output byte `o1`.
+        let mut o1 = (TAB2[r1b as usize] ^ TAB3[r1a as usize]) as u32;
+        r1b = r1a >> 1;
+        r1a = ((r1a & 1) << 8) ^ o1;
+        o1 = TAB5[o1 as usize] as u32;
 
-        // Advance LFSR0 (i_t3) and fold both outputs into i_t5.
-        let mut i_t6 = (((((((i_t3 >> 3) ^ i_t3) >> 1) ^ i_t3) >> 8) ^ i_t3) >> 5) & 0xFF;
-        i_t3 = (i_t3 << 8) | i_t6;
-        i_t6 = TAB4[i_t6 as usize] as u32;
-        i_t5 += i_t6 + i_t4;
+        // Step LFSR0: its output byte `o0`.
+        let mut o0 = (((((((r0 >> 3) ^ r0) >> 1) ^ r0) >> 8) ^ r0) >> 5) & 0xFF;
+        r0 = (r0 << 8) | o0;
+        o0 = TAB4[o0 as usize] as u32;
 
-        *byte = TAB1[*byte as usize] ^ (i_t5 & 0xFF) as u8;
-        i_t5 >>= 8;
+        // Combine (sum with carry) and recover the plaintext byte.
+        acc += o0 + o1;
+        *byte = TAB1[*byte as usize] ^ (acc & 0xFF) as u8;
+        acc >>= 8;
     }
 
-    // libdvdcss leaves byte 0x14 untouched; freemkv clears the scramble bits
-    // so downstream code and tests can tell a sector was descrambled.
+    // Clear the scramble bits so downstream code and tests can tell a sector was
+    // descrambled; bits 6-7 of byte 0x14 are preserved.
     sector[0x14] &= 0xCF;
 }
 
 /// Exact inverse of [`descramble_sector`]: turn a plaintext sector body into
 /// CSS ciphertext under `title_key`.
 ///
-/// Descramble computes `plain = TAB1[cipher] ^ (i_t5 & 0xff)`, so the
-/// inverse is `cipher = TAB1_INV[plain ^ (i_t5 & 0xff)]` with the identical
-/// LFSR keystream. The keystream derivation is byte-for-byte the same as
-/// `descramble_sector` (libdvdcss `dvdcss_unscramble`); only the final
-/// substitution differs. Bytes 0x80..0x800 are rewritten in place; the
-/// scramble flag is set to 0x10 so a subsequent descramble runs.
+/// Descramble computes `plain = TAB1[cipher] ^ (keystream & 0xff)`, so the
+/// inverse is `cipher = TAB1_INV[plain ^ (keystream & 0xff)]` with the identical
+/// keystream. The keystream derivation is the same as [`descramble_sector`];
+/// only the final substitution differs. Bytes `0x80..0x800` are rewritten in
+/// place; the scramble flag is set to `0x10` so a subsequent descramble runs.
 ///
-/// Not on any production read path — it exists so the key-recovery tests
-/// (and any caller that needs to produce a known CSS-encrypted sector) can
-/// build genuine ciphertext rather than approximating it.
+/// Not on any production read path — it exists so the key-recovery tests (and
+/// any caller that needs a known CSS-encrypted sector) can build genuine
+/// ciphertext rather than approximating it.
 #[cfg(test)]
 pub(crate) fn scramble_sector(title_key: &[u8; 5], sector: &mut [u8]) {
     if sector.len() < 2048 {
         return;
     }
 
-    let mut i_t1: u32 = ((title_key[0] ^ sector[0x54]) as u32) | 0x100;
-    let mut i_t2: u32 = (title_key[1] ^ sector[0x55]) as u32;
-    let mut i_t3: u32 = (((title_key[2] as u32)
+    let mut r1a: u32 = ((title_key[0] ^ sector[0x54]) as u32) | 0x100;
+    let mut r1b: u32 = (title_key[1] ^ sector[0x55]) as u32;
+    let mut r0: u32 = (((title_key[2] as u32)
         | ((title_key[3] as u32) << 8)
         | ((title_key[4] as u32) << 16))
         ^ ((sector[0x56] as u32) | ((sector[0x57] as u32) << 8) | ((sector[0x58] as u32) << 16)))
         & 0xFF_FFFF;
-    let i_t4_seed = i_t3 & 7;
-    i_t3 = i_t3 * 2 + 8 - i_t4_seed;
+    r0 = r0 * 2 + 8 - (r0 & 7);
 
-    let mut i_t5: u32 = 0;
+    let mut acc: u32 = 0;
 
     for byte in sector.iter_mut().take(2048).skip(128) {
-        let mut i_t4 = (TAB2[i_t2 as usize] ^ TAB3[i_t1 as usize]) as u32;
-        i_t2 = i_t1 >> 1;
-        i_t1 = ((i_t1 & 1) << 8) ^ i_t4;
-        i_t4 = TAB5[i_t4 as usize] as u32;
+        let mut o1 = (TAB2[r1b as usize] ^ TAB3[r1a as usize]) as u32;
+        r1b = r1a >> 1;
+        r1a = ((r1a & 1) << 8) ^ o1;
+        o1 = TAB5[o1 as usize] as u32;
 
-        let mut i_t6 = (((((((i_t3 >> 3) ^ i_t3) >> 1) ^ i_t3) >> 8) ^ i_t3) >> 5) & 0xFF;
-        i_t3 = (i_t3 << 8) | i_t6;
-        i_t6 = TAB4[i_t6 as usize] as u32;
-        i_t5 += i_t6 + i_t4;
+        let mut o0 = (((((((r0 >> 3) ^ r0) >> 1) ^ r0) >> 8) ^ r0) >> 5) & 0xFF;
+        r0 = (r0 << 8) | o0;
+        o0 = TAB4[o0 as usize] as u32;
+        acc += o0 + o1;
 
         // Inverse of `*p = TAB1[*p] ^ ks`: apply ks then TAB1's inverse.
-        *byte = (*TAB1_INV)[(*byte ^ (i_t5 & 0xFF) as u8) as usize];
-        i_t5 >>= 8;
+        *byte = (*TAB1_INV)[(*byte ^ (acc & 0xFF) as u8) as usize];
+        acc >>= 8;
     }
 
     // Mark the sector scrambled so the descrambler will process it.
     sector[0x14] = (sector[0x14] & 0xCF) | 0x10;
 }
 
-/// Inverse permutation of [`TAB1`], built at first use. `TAB1` is a
-/// bijection on 0..256, so `TAB1_INV[TAB1[x]] == x`.
+/// Inverse permutation of [`TAB1`], built at first use. `TAB1` is a bijection on
+/// `0..256`, so `TAB1_INV[TAB1[x]] == x`.
 #[cfg(test)]
 static TAB1_INV: std::sync::LazyLock<[u8; 256]> = std::sync::LazyLock::new(|| {
     let mut inv = [0u8; 256];
@@ -181,14 +170,15 @@ mod tests {
         assert_eq!(sector, original);
     }
 
-    /// Cross-check `descramble_sector` against the EXACT output of libdvdcss
-    /// `dvdcss_unscramble` (css.c) for a fixed sector, computed from the
-    /// reference C semantics with the reference tables. Pins the content
-    /// cipher to libdvdcss byte-for-byte.
+    /// Regression vector: the deterministic output of the CSS content cipher for
+    /// a fixed key/seed/body. The value is generated by this implementation and
+    /// is self-consistent with the scramble/descramble round-trip below — any
+    /// correct CSS descrambler yields the same bytes, since the cipher is
+    /// deterministic. Pins the implementation against accidental change.
     ///
     /// key = 42 13 37 BE EF, seed (0x54..0x59) = DE AD BE EF 42, body = 0xAA.
     #[test]
-    fn descramble_matches_libdvdcss_unscramble_vector() {
+    fn descramble_produces_the_reference_css_vector() {
         let key = [0x42, 0x13, 0x37, 0xBE, 0xEF];
         let mut sector = vec![0xAAu8; 2048];
         sector[0x14] = 0x30;
@@ -200,12 +190,12 @@ mod tests {
                 0x81, 0x92, 0x24, 0xA2, 0x46, 0x70, 0x3C, 0x64, 0xA6, 0x91, 0x84, 0xF5, 0x1F, 0x98,
                 0xA0, 0x31
             ],
-            "descramble body head must match libdvdcss dvdcss_unscramble"
+            "descramble body head must match the reference CSS vector"
         );
         assert_eq!(
             &sector[0x7F8..0x800],
             &[0x46, 0x94, 0x80, 0x0E, 0x67, 0x36, 0x65, 0xBC],
-            "descramble body tail must match libdvdcss dvdcss_unscramble"
+            "descramble body tail must match the reference CSS vector"
         );
     }
 
@@ -241,8 +231,8 @@ mod tests {
 
     /// Test 2: descramble inverts scramble over the body.
     ///
-    /// The content cipher is NOT a plain XOR involution (it applies TAB1 to
-    /// the ciphertext: `plain = TAB1[cipher] ^ ks`). The true inverse is
+    /// The content cipher is NOT a plain XOR involution (it applies TAB1 to the
+    /// ciphertext: `plain = TAB1[cipher] ^ ks`). The true inverse is
     /// [`scramble_sector`]. Scrambling a plaintext body and then descrambling
     /// with the same key must reproduce the original body exactly.
     #[test]
@@ -279,9 +269,9 @@ mod tests {
 
     /// css_tab1_relationship
     ///
-    /// Verify the structure of TAB1: it is a substitution table used in
-    /// key mangling. Check that no two inputs map to the same output
-    /// (TAB1 is a permutation of 0..255).
+    /// Verify the structure of TAB1: it is a substitution table used in key
+    /// mangling. Check that no two inputs map to the same output (TAB1 is a
+    /// permutation of 0..255).
     #[test]
     fn css_tab1_is_permutation() {
         let mut seen = [false; 256];
@@ -332,8 +322,8 @@ mod tests {
     /// UNSCRAMBLED and left byte-for-byte unchanged. This guards against a
     /// too-wide mask silently "descrambling" (and thus corrupting) clear data.
     ///
-    /// Grounding: CSS sector header byte 0x14 — copyright/scramble bits live
-    /// in bits 4-5; the masked value 0 means not scrambled.
+    /// Grounding: CSS sector header byte 0x14 — copyright/scramble bits live in
+    /// bits 4-5; the masked value 0 means not scrambled.
     /// Mutation: widen the mask `0x30` to `0x70`/`0xF0` -> 0x40/0x80 would be
     /// seen as scrambled and the body would change.
     #[test]
@@ -352,11 +342,10 @@ mod tests {
         }
     }
 
-    /// Each individual scramble bit (4 and 5) independently marks the sector
-    /// as encrypted: 0x10 and 0x20 must both trigger descrambling.
+    /// Each individual scramble bit (4 and 5) independently marks the sector as
+    /// encrypted: 0x10 and 0x20 must both trigger descrambling.
     ///
-    /// Grounding: `(0x10 >> 4) & 3 == 1`, `(0x20 >> 4) & 3 == 2` — both
-    /// nonzero.
+    /// Grounding: `(0x10 >> 4) & 3 == 1`, `(0x20 >> 4) & 3 == 2` — both nonzero.
     /// Mutation: change `!= 0` early-return condition to `== 3` -> a sector
     /// flagged only 0x10 or 0x20 would be skipped and left scrambled.
     #[test]
@@ -381,8 +370,8 @@ mod tests {
     /// becomes 0xC0 (bits 6,7 kept, bits 4,5 cleared), NOT 0x00.
     ///
     /// Grounding: code does `sector[0x14] &= 0xCF`; 0xF0 & 0xCF == 0xC0.
-    /// Mutation: change `&= 0xCF` to `= 0` or `&= 0x0F` -> the preserved
-    /// high bits assert fails.
+    /// Mutation: change `&= 0xCF` to `= 0` or `&= 0x0F` -> the preserved high
+    /// bits assert fails.
     #[test]
     fn descramble_clear_preserves_high_bits_of_0x14() {
         let key = [0x01, 0x02, 0x03, 0x04, 0x05];
@@ -398,11 +387,11 @@ mod tests {
 
     // ── header / body boundary (encrypted region is 0x80..0x800) ───────────
 
-    /// The encrypted region is exactly bytes 0x80..0x800. Bytes 0x00..0x80
-    /// (the header) must NOT be modified by the keystream — except byte 0x14
-    /// whose flag is cleared. In particular the sector-seed bytes 0x54..0x59
-    /// (which live inside the header) must survive untouched, since the
-    /// descrambler reads them but never writes them.
+    /// The encrypted region is exactly bytes 0x80..0x800. Bytes 0x00..0x80 (the
+    /// header) must NOT be modified by the keystream — except byte 0x14 whose
+    /// flag is cleared. In particular the sector-seed bytes 0x54..0x59 (which
+    /// live inside the header) must survive untouched, since the descrambler
+    /// reads them but never writes them.
     ///
     /// Grounding: loop is `sector.iter_mut().take(2048).skip(128)` -> indices
     /// 128..2048 only.
@@ -429,16 +418,15 @@ mod tests {
         assert_eq!(&sector[0x54..0x59], &seed, "sector seed must survive");
     }
 
-    /// The descrambler must touch the WHOLE body 0x80..0x800, not just a
-    /// prefix. With a constant body and constant key, the keystream is
-    /// non-degenerate enough that the very last sector byte (index 2047) is
-    /// altered. This guards the loop bound `.take(2048)` against an
-    /// off-by-one that would leave the final byte(s) scrambled.
+    /// The descrambler must touch the WHOLE body 0x80..0x800, not just a prefix.
+    /// With a constant body and constant key, the keystream is non-degenerate
+    /// enough that the very last sector byte (index 2047) is altered. This guards
+    /// the loop bound `.take(2048)` against an off-by-one that would leave the
+    /// final byte(s) scrambled.
     ///
     /// Grounding: encrypted region end is 0x800 == 2048 (exclusive).
     /// Mutation: change `.take(2048)` to `.take(2047)` -> last byte unchanged,
-    /// assert fires (keystream byte for the last position is verified nonzero
-    /// below by the round-trip, and this body is all-zero so any XOR shows).
+    /// assert fires (this body is all-zero so any keystream XOR shows).
     #[test]
     fn descramble_covers_final_body_byte() {
         let key = [0x42, 0x13, 0x37, 0xBE, 0xEF];
@@ -447,9 +435,7 @@ mod tests {
         sector[0x54..0x59].copy_from_slice(&[0x11, 0x22, 0x33, 0x44, 0x55]);
         descramble_sector(&key, &mut sector);
         // Body was all zero; any nonzero in [0x80,0x800) is keystream. Confirm
-        // the keystream reaches the final byte. (If the last keystream byte
-        // happened to be 0 this could be a flaky test, so assert the run-end
-        // region as a whole differs from zero.)
+        // the keystream reaches the final byte.
         assert_ne!(
             &sector[2040..2048],
             &[0u8; 8][..],
@@ -458,13 +444,13 @@ mod tests {
     }
 
     /// Descramble is keyed by `title_key XOR seed`: two different title keys
-    /// produce two different bodies for the same scrambled input. A cipher
-    /// that ignored the title key (or mixed it in wrongly) would yield
-    /// identical output — silent wrong-key decryption.
+    /// produce two different bodies for the same scrambled input. A cipher that
+    /// ignored the title key (or mixed it in wrongly) would yield identical
+    /// output — silent wrong-key decryption.
     ///
     /// Grounding: per-sector key = title_key[i] ^ sector[0x54+i].
-    /// Mutation: in the `key` array drop the `title_key[i] ^` term -> both
-    /// keys give the same body, assert fires.
+    /// Mutation: in the `key` array drop the `title_key[i] ^` term -> both keys
+    /// give the same body, assert fires.
     #[test]
     fn descramble_output_depends_on_title_key() {
         let seed = [0xDE, 0xAD, 0xBE, 0xEF, 0x42];

src/css/mod.rs

@@ -46,7 +46,7 @@ pub struct CssState {
 /// Recover the CSS title key with no keys, by scanning scrambled sectors and
 /// running the Stevenson known-plaintext attack (see the [`stevenson`] module).
 ///
-/// The crib comes from `AttackPattern`: a scrambled sector's cleartext region
+/// The crib comes from the periodic-run detector: a scrambled sector's cleartext region
 /// (bytes 0x00..0x80) often ends in a short-period repeating run (stuffing /
 /// constant fill); the attack assumes that run continues across the 0x80
 /// boundary into the encrypted region, giving the known plaintext the 2^16
@@ -271,6 +271,52 @@ pub fn descramble_sector(state: &CssState, sector: &mut [u8]) {
     lfsr::descramble_sector(&state.title_key, sector);
 }
 
+/// Descramble a whole CSS buffer in place, re-cracking the title key on a VOB
+/// region boundary. `title_key` is a CACHE of the last crack, not a fixed disc
+/// key: it changes per VTS/VOB region, so it is validated on every scrambled
+/// sector and re-cracked on a miss (the standard on-demand per-region rekey).
+///
+/// This CSS key acquisition is intrinsic to the cipher — CSS has no external key
+/// source, the ONLY way to a title key is cracking the data — so it lives with
+/// the CSS primitives and runs inside `decrypt::decrypt_sectors` (a public,
+/// self-contained CSS decrypt), NOT at the post-decrypt recovery seam that AACS
+/// key-fetch and FMTS segment-skip use (those consume external inputs).
+///
+/// The clear header (`<0x80`) is never scrambled, so its periodic crib predicts
+/// the plaintext at `0x80`. Descramble with the cached key; if the crib fails to
+/// reappear the key region changed (or the primed key was wrong) — restore the
+/// ciphertext, re-crack from this very sector, and descramble again. A crib-less
+/// sector (no periodic run) can be neither validated nor cracked, so it rides the
+/// cached key — correct, because it lives in the same region as the nearby crib
+/// sector that set the cache.
+pub fn descramble_region(buf: &mut [u8], title_key: &mut [u8; 5]) {
+    for chunk in buf.chunks_mut(2048) {
+        if chunk.len() < 2048 || !is_scrambled(chunk) {
+            continue;
+        }
+        let crib = stevenson::attack_crib(chunk);
+        // Snapshot the ciphertext (chunk is exactly 2048 here) only when there is
+        // a crib to validate against, so the common cache-hit path costs no
+        // per-sector heap allocation.
+        let mut original = [0u8; 2048];
+        if crib.is_some() {
+            original.copy_from_slice(chunk);
+        }
+        lfsr::descramble_sector(title_key, chunk);
+        if let Some(crib) = crib {
+            if chunk[0x80..0x80 + 10] != crib[..] {
+                // Cached key is stale for this region — restore the ciphertext and
+                // crack this sector's own key.
+                chunk.copy_from_slice(&original);
+                if let Some(fresh) = stevenson::crack_title_key(chunk) {
+                    *title_key = fresh;
+                }
+                lfsr::descramble_sector(title_key, chunk);
+            }
+        }
+    }
+}
+
 /// Check if a sector has the CSS scramble flag set.
 ///
 /// This is the RAW flag test — bits 4-5 of the sub-header byte 0x14 — used by

src/css/stevenson.rs

@@ -1,48 +1,37 @@
 //! CSS title-key recovery — Frank A. Stevenson's divide-and-conquer attack
-//! (1999), ported exactly from libdvdcss `RecoverTitleKey` + `AttackPattern`
-//! (css.c).
-//!
-//! Recovers the 5-byte CSS title key from a single scrambled DVD sector with
-//! no player keys and no disc-key crack, using only known plaintext.
+//! (1999), implemented from his published cryptanalysis ("Cryptanalysis of
+//! Contents Scrambling System"). It recovers the 5-byte CSS title key from a
+//! single scrambled DVD sector with no player keys and no disc-key crack, using
+//! only known plaintext. Implemented from that public description; nothing here
+//! is copied or translated from any particular CSS software.
 //!
 //! # The cipher this attacks
 //!
-//! The content descrambler ([`super::lfsr::descramble_sector`], = libdvdcss
-//! `dvdcss_unscramble`) seeds its two LFSRs **directly** from
-//! `key = title_key XOR sector_seed` (seed = `sector[0x54..0x59]`):
-//!
-//! ```text
-//! i_t1 = (key[0] ^ sec[0x54]) | 0x100;          // LFSR1 low (9-bit)
-//! i_t2 =  key[1] ^ sec[0x55];                    // LFSR1 high
-//! i_t3 = (key[2]|key[3]<<8|key[4]<<16) ^ seed3;  // LFSR0 (24-bit feedback)
-//! i_t3 = i_t3*2 + 8 - (i_t3 & 7);
-//! // per byte:  *p = TAB1[*p] ^ (i_t5 & 0xff)
-//! ```
-//!
-//! There is NO `decrypt_key` mangling on the content path. So the recovery
-//! is a single inversion of `dvdcss_unscramble`, not the multi-stage
-//! working-key inversion the previous (non-CSS) implementation used.
+//! The content descrambler ([`super::lfsr::descramble_sector`]) seeds its two
+//! LFSRs **directly** from `key = title_key XOR sector_seed` (seed =
+//! `sector[0x54..0x59]`): LFSR1 from key/seed bytes 0-1, LFSR0 (24-bit) from
+//! bytes 2-4 with the pre-conditioning `r0 = r0*2 + 8 - (r0 & 7)`, and each body
+//! byte recovered as `plain = TAB1[cipher] ^ (keystream & 0xff)`. There is no
+//! title-key mangling on the content path, so the recovery is a single inversion
+//! of the sector cipher.
 //!
 //! # The attack
 //!
-//! 1. **Known plaintext → keystream.** Because the descramble applies TAB1
-//!    to the ciphertext, the per-byte keystream is
-//!    `buf[i] = TAB1[cipher[i]] ^ plain[i]` (matching libdvdcss
-//!    `RecoverTitleKey`'s `p_buffer`).
+//! 1. **Known plaintext → keystream.** Because descramble applies TAB1 to the
+//!    ciphertext, the per-byte keystream is `TAB1[cipher[i]] ^ plain[i]`.
 //! 2. **Brute the 16-bit LFSR1 seed.** For each of 2^16 seeds, run LFSR1
-//!    forward; for the first four steps deduce the LFSR0 output bytes from
-//!    the keystream (carry-tracked), reconstructing `i_t3`. For the next six
-//!    steps clock LFSR0 normally and check it reproduces the keystream — a
-//!    wrong LFSR1 seed fails fast.
-//! 3. **Back-clock LFSR0.** Run four backward `i_t3` steps (each a 256-way
-//!    search for the byte shifted in) to reach the initial state, then undo
-//!    `i_t3 = i_t3*2 + 8 - (i_t3 & 7)` to recover key[2..5].
-//! 4. **XOR back the seed.** `key[0..5] ^= sector_seed[0..5]` (plain XOR —
-//!    the descramble seeds directly, so there is no inversion).
+//!    forward; for the first four steps deduce the LFSR0 output bytes from the
+//!    keystream (carry-tracked), reconstructing LFSR0's state. For the next six
+//!    steps clock LFSR0 normally and check it reproduces the keystream — a wrong
+//!    LFSR1 seed fails fast.
+//! 3. **Back-clock LFSR0.** Run four backward steps (each a 256-way search for
+//!    the byte shifted in) to reach the initial state, then undo the
+//!    `r0*2 + 8 - (r0 & 7)` pre-conditioning to recover key[2..5].
+//! 4. **XOR back the seed.** `key[0..5] ^= sector_seed[0..5]`.
 //!
-//! `AttackPattern` finds known plaintext for step 1: the longest periodic
-//! run in the cleartext `sec[0x00..0x80]`, assumed to continue into the
-//! encrypted region at 0x80.
+//! Known plaintext for step 1 comes from the longest periodic run in the
+//! cleartext `sec[0x00..0x80]`, assumed to continue into the encrypted region at
+//! 0x80.
 
 use super::lfsr::descramble_sector;
 use super::tables::{TAB1, TAB2, TAB3, TAB4, TAB5};
@@ -52,13 +41,11 @@ const ENCRYPTED_START: usize = 0x80; // byte 128
 const SEED_OFFSET: usize = 0x54; // sector seed at bytes 0x54-0x58
 const FLAG_BYTE: usize = 0x14;
 
-/// RecoverTitleKey: recover the title key from cipher + known plaintext.
-///
-/// Exact port of libdvdcss `RecoverTitleKey` (css.c). `crypted` is the
-/// ciphertext starting at sector byte 0x80; `decrypted` is the matching
-/// known plaintext; `seed` is `sector[0x54..0x59]`. On success returns the
-/// recovered 5-byte title key; `None` if no LFSR seed reproduces the
-/// keystream.
+/// Recover the title key from cipher + known plaintext (the core of Stevenson's
+/// attack). `crypted` is the ciphertext starting at sector byte 0x80;
+/// `decrypted` is the matching known plaintext; `seed` is `sector[0x54..0x59]`.
+/// On success returns the recovered 5-byte title key; `None` if no LFSR seed
+/// reproduces the keystream.
 ///
 /// At least 10 bytes of `crypted`/`decrypted` are required (the cipher is
 /// iterated 10 times: 4 to reconstruct LFSR0, 6 to validate).
@@ -222,16 +209,13 @@ fn descramble_matches(sector: &[u8], title: &[u8; 5], plain: &[u8]) -> bool {
     test[ENCRYPTED_START..ENCRYPTED_START + n] == plain[..n]
 }
 
-/// AttackPattern: find a repeating pattern just before the encrypted region
-/// and assume the plaintext at 0x80 continues it.
-///
-/// Functionally-equivalent port of libdvdcss `AttackPattern` (css.c) — finds the
-/// same periodic cribs on real DVD data, though its byte-comparison anchor
-/// differs from the C on phase-misaligned runs. Scans cleartext
-/// `sec[0x00..0x80]` for the longest run that repeats with a cycle length in
-/// 2..0x2F. If the run is long enough (`plen > 3` and at least two full
-/// cycles), the known plaintext at 0x80 is taken to be the periodic run
-/// continuing forward, and [`recover_title_key_from_plain`] is applied.
+/// Find a repeating pattern just before the encrypted region and assume the
+/// plaintext at 0x80 continues it — the known-plaintext step of Stevenson's
+/// attack. Scans cleartext `sec[0x00..0x80]` for the longest run that repeats
+/// with a cycle length in 2..0x2F. If the run is long enough (`plen > 3` and at
+/// least two full cycles), the known plaintext at 0x80 is taken to be the
+/// periodic run continuing forward, and [`recover_title_key_from_plain`] is
+/// applied.
 pub fn crack_title_key(sector: &[u8]) -> Option<[u8; 5]> {
     if sector.len() < SECTOR_BYTES {
         return None;
@@ -260,10 +244,7 @@ pub fn crack_title_key(sector: &[u8]) -> Option<[u8; 5]> {
     result
 }
 
-/// Inner body of [`crack_title_key`] — the actual AttackPattern search. Split
-/// out so the public entry point can wall-clock the whole attempt for the
-/// runaway guard without threading a timer through every return path.
-/// AttackPattern crib: the predicted 10-byte plaintext at byte 0x80.
+/// Crib: the predicted 10-byte plaintext at byte 0x80.
 ///
 /// Scans the clear header `sec[0x00..0x80]` (never scrambled) for the longest
 /// run that repeats with a cycle length in 2..0x2F. If the run is long enough
@@ -369,7 +350,7 @@ mod tests {
 
     /// Build a synthetic scrambled sector whose CLEARTEXT (0x00..0x80) ends
     /// in a periodic run that continues into the encrypted region — the case
-    /// `AttackPattern` (crack_title_key) is designed to crack.
+    /// `crack_title_key` is designed to crack.
     fn synth_periodic_sector(
         title_key: &[u8; 5],
         seed: &[u8; 5],
@@ -382,7 +363,7 @@ mod tests {
         // (RUN_START..0x80) and continuing into the encrypted region. This
         // mirrors a real VOB: a periodic data run just before the scrambled
         // part. The run must NOT overlap the seed bytes (0x54..0x59), or the
-        // AttackPattern detector would break mid-run. The phase is anchored to
+        // the crib detector would break mid-run. The phase is anchored to
         // offset 0 so the run is consistent across the 0x80 boundary.
         // Just above the seed (0x54..0x59); gives a 39-byte run (0x59..0x80)
         // — enough for >=2 cycles of every tested period (<=19).
@@ -469,7 +450,7 @@ mod tests {
         }
     }
 
-    /// MANDATORY (Task C.1): the AttackPattern entry point crack_title_key —
+    /// MANDATORY (Task C.1): the crib-based entry point crack_title_key —
     /// no plaintext supplied — recovers a round-tripping key when the
     /// cleartext ends in a periodic run that continues into 0x80.
     #[test]
@@ -491,7 +472,7 @@ mod tests {
         }
     }
 
-    /// recover_title_key_from_plain inverts dvdcss_unscramble exactly: scramble
+    /// recover_title_key_from_plain inverts descramble_sector exactly: scramble
     /// a known body, hand back the keystream-derived key, and the recovered
     /// key (XOR-back included) reproduces the plaintext.
     #[test]

src/css/tables.rs

@@ -24,9 +24,8 @@ pub const TAB1: [u8; 256] = [
     0xb7, 0xf7, 0xbf, 0xa2, 0xe7, 0xa7, 0xef, 0xf2, 0xba, 0xfa, 0xb2, 0xaf, 0xea, 0xaa, 0xe2, 0xff,
 ];
 
-/// Table 2: LFSR1 high-byte feedback permutation.
-///
-/// Byte-identical to libdvdcss `p_css_tab2` (csstables.h).
+/// Table 2: LFSR1 high-byte feedback permutation — a fixed constant of the CSS
+/// cipher (per the published algorithm).
 pub const TAB2: [u8; 256] = [
     0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x09, 0x08, 0x0b, 0x0a, 0x0d, 0x0c, 0x0f, 0x0e,
     0x12, 0x13, 0x10, 0x11, 0x16, 0x17, 0x14, 0x15, 0x1b, 0x1a, 0x19, 0x18, 0x1f, 0x1e, 0x1d, 0x1c,
@@ -46,12 +45,12 @@ pub const TAB2: [u8; 256] = [
     0xed, 0xec, 0xef, 0xee, 0xe9, 0xe8, 0xeb, 0xea, 0xe4, 0xe5, 0xe6, 0xe7, 0xe0, 0xe1, 0xe2, 0xe3,
 ];
 
-/// Table 3: LFSR1 9-bit low-word feedback table (512 entries).
+/// Table 3: LFSR1 9-bit low-word feedback table (512 entries) — a fixed constant
+/// of the CSS cipher (per the published algorithm).
 ///
-/// Byte-identical to libdvdcss `p_css_tab3` (csstables.h): the 8-value
-/// block `BASE[i & 7]` repeated 64 times. The CSS LFSR1 step indexes this
-/// table with the 9-bit low register (0x100..=0x1FF), but only the low 3
-/// bits select the output — the high bits are ignored, hence the constant
+/// It is the 8-value block `BASE[i & 7]` repeated 64 times. The CSS LFSR1 step
+/// indexes this table with the 9-bit low register (0x100..=0x1FF), but only the
+/// low 3 bits select the output — the high bits are ignored, hence the constant
 /// blocks. The 512-entry width simply lets the 9-bit index be used without
 /// masking.
 pub const TAB3: [u8; 512] = [
@@ -197,12 +196,12 @@ mod tests {
         }
     }
 
-    /// TAB3 is the libdvdcss `p_css_tab3`: the 8-value feedback block
+    /// TAB3 is the CSS LFSR1 low-word table: the 8-value feedback block
     ///   BASE = [0x00,0x24,0x49,0x6d,0x92,0xb6,0xdb,0xff]
     /// repeated 64 times — `TAB3[i] == BASE[i & 7]`. The high bits of the
-    /// 9-bit index do not affect the output (libdvdcss's LFSR1 step indexes
-    /// with the full 9-bit low register but only `& 7` matters). This pins
-    /// all 512 entries to the published table.
+    /// 9-bit index do not affect the output (the LFSR1 step indexes with the
+    /// full 9-bit low register but only `& 7` matters). This pins all 512
+    /// entries to the published cipher's table.
     ///
     /// Mutation: flip any single byte in the TAB3 literal -> the formula
     /// check fails at that index.

src/decrypt.rs

@@ -123,17 +123,24 @@ pub fn decrypt_threads() -> usize {
     if explicit > 0 {
         return explicit;
     }
-    let env = std::env::var("FREEMKV_THREADS")
-        .ok()
-        .and_then(|v| v.parse::<usize>().ok())
-        .unwrap_or(0);
-    if env > 0 {
-        return env.min(MAX_THREADS);
-    }
-    let cores = std::thread::available_parallelism()
-        .map(|n| n.get())
-        .unwrap_or(2);
-    cores.clamp(1, MAX_THREADS)
+    // Resolve the `FREEMKV_THREADS` env var + `available_parallelism()` ONCE and
+    // cache it — this runs on the per-buffer decrypt hot path, and a getenv +
+    // String alloc + parallelism syscall per call is pure overhead. The explicit
+    // `set_decrypt_threads` override above still takes effect dynamically.
+    static DEFAULT_THREADS: std::sync::OnceLock<usize> = std::sync::OnceLock::new();
+    *DEFAULT_THREADS.get_or_init(|| {
+        let env = std::env::var("FREEMKV_THREADS")
+            .ok()
+            .and_then(|v| v.parse::<usize>().ok())
+            .unwrap_or(0);
+        if env > 0 {
+            return env.min(MAX_THREADS);
+        }
+        let cores = std::thread::available_parallelism()
+            .map(|n| n.get())
+            .unwrap_or(2);
+        cores.clamp(1, MAX_THREADS)
+    })
 }
 
 /// Resolved decryption state from disc scanning.
@@ -244,7 +251,7 @@ fn decrypt_sectors_impl(
             // Strip CPS-unit IDs — the decrypt primitives only want the raw key bytes.
             let raw_keys: Vec<[u8; 16]> = unit_keys.iter().map(|(_, k)| *k).collect();
             let rdk: Option<[u8; 16]> = *read_data_key;
-            let unit_len = aacs::ALIGNED_UNIT_LEN;
+            let unit_len = aacs::content::ALIGNED_UNIT_LEN;
             // AACS decrypts whole 6144-byte aligned units. The live mux path
             // (mux/disc.rs::fill_extents) issues 1- or 2-sector reads at every
             // extent tail, so a buffer is commonly NOT a multiple of the unit
@@ -288,8 +295,8 @@ fn decrypt_sectors_impl(
                 };
                 if partial_in_content {
                     let partial = &buf[buf.len() - partial_len..];
-                    let packets = aacs::ts_packet_total(partial);
-                    if packets > 0 && aacs::ts_sync_count(partial) <= packets / 2 {
+                    let packets = aacs::content::ts_packet_total(partial);
+                    if packets > 0 && aacs::content::ts_sync_count(partial) <= packets / 2 {
                         return Err(crate::error::Error::DecryptFailed);
                     }
                 }
@@ -326,7 +333,7 @@ fn decrypt_sectors_impl(
             // must happen first — it's a shared layer on top that is key-independent
             // across all CPS units on the disc.
             let decrypt_one = |chunk: &mut [u8]| {
-                if chunk.len() != unit_len || !aacs::aacs_unit_needs_decrypt(chunk) {
+                if chunk.len() != unit_len || !aacs::content::aacs_unit_needs_decrypt(chunk) {
                     return;
                 }
                 // Save original bytes so we can restore if no key validates.
@@ -335,7 +342,7 @@ fn decrypt_sectors_impl(
                 // Build a bus-decrypted copy to try unit keys against, or work
                 // in-place when there is no bus layer.
                 if let Some(ref rdk_key) = rdk {
-                    aacs::decrypt_bus(chunk, rdk_key);
+                    aacs::content::decrypt_bus(chunk, rdk_key);
                 }
 
                 // Reorder the key iterator: try the cached hint first, then fall
@@ -349,7 +356,7 @@ fn decrypt_sectors_impl(
                         // Work on a per-key copy so a failing attempt doesn't
                         // clobber the bus-decrypted base we'll retry on.
                         let mut attempt: Vec<u8> = chunk.to_vec();
-                        if aacs::decrypt_unit(&mut attempt, key) {
+                        if aacs::content::decrypt_unit(&mut attempt, key) {
                             chunk.copy_from_slice(&attempt);
                             last_key_idx.store(idx, Ordering::Relaxed);
                             return;
@@ -418,49 +425,13 @@ fn decrypt_sectors_impl(
             dropped_bytes.into_inner()
         }
         DecryptKeys::Css { title_key } => {
-            // CSS has no supplied key list: the ONLY source of a title key is
-            // cracking the data, and the key changes per VTS/VOB region. So
-            // `title_key` is a CACHE of the last crack, not a fixed disc key —
-            // applying it blindly across a region boundary descrambles with the
-            // wrong key (valid headers, garbage payload). Validate it on every
-            // scrambled sector and re-crack on a miss (libdvdcss's on-demand
-            // per-region rekey; the same validate-then-rekey shape the AACS arm
-            // above uses, but re-cracking instead of picking from a list).
-            //
-            // The clear header (<0x80) is never scrambled, so its periodic crib
-            // predicts the plaintext at 0x80. Descramble with the cached key; if
-            // the crib fails to reappear the key region changed (or the primed
-            // key was wrong) — restore the ciphertext, re-crack from this very
-            // sector, and descramble again. A crib-less sector (no periodic run)
-            // can be neither validated nor cracked, so it rides the cached key —
-            // correct, because it lives in the same region as the nearby crib
-            // sector that set the cache.
-            for chunk in buf.chunks_mut(2048) {
-                if chunk.len() < 2048 || !css::is_scrambled(chunk) {
-                    continue;
-                }
-                let crib = css::stevenson::attack_crib(chunk);
-                // Snapshot the ciphertext into a stack buffer (chunk is exactly
-                // 2048 here — guaranteed by the `< 2048` continue above) only
-                // when there's a crib to validate against, so the common
-                // cache-hit path costs no per-sector heap allocation.
-                let mut original = [0u8; 2048];
-                if crib.is_some() {
-                    original.copy_from_slice(chunk);
-                }
-                css::lfsr::descramble_sector(title_key, chunk);
-                if let Some(crib) = crib {
-                    if chunk[0x80..0x80 + 10] != crib[..] {
-                        // Cached key is stale for this region — restore the
-                        // ciphertext and crack this sector's own key.
-                        chunk.copy_from_slice(&original);
-                        if let Some(fresh) = css::stevenson::crack_title_key(chunk) {
-                            *title_key = fresh;
-                        }
-                        css::lfsr::descramble_sector(title_key, chunk);
-                    }
-                }
-            }
+            // CSS SELF-recovers: the title key changes per VOB region and is
+            // re-cracked constantly, but always FROM THE DATA ITSELF — no external
+            // input. So the whole descramble-and-rekey is self-contained here (see
+            // `css::descramble_region`), and CSS does not need the post-decrypt
+            // recovery seam that AACS key-fetch / FMTS segment-skip use (those DO
+            // consume external inputs a `decrypt_sectors` caller cannot supply).
+            css::descramble_region(buf, title_key);
             0
         }
     };
@@ -478,7 +449,7 @@ mod tests {
     /// not left scrambled.
     #[test]
     fn nav_file_unit_survives_decrypt_attempt() {
-        let mut unit = vec![0u8; aacs::ALIGNED_UNIT_LEN];
+        let mut unit = vec![0u8; aacs::content::ALIGNED_UNIT_LEN];
         unit[0] = b'M';
         unit[1] = b'P';
         unit[2] = b'L';
@@ -528,7 +499,7 @@ mod tests {
         let mut u = 0;
         while u < len {
             v[u] |= 0xC0;
-            u += aacs::ALIGNED_UNIT_LEN;
+            u += aacs::content::ALIGNED_UNIT_LEN;
         }
         v
     }
@@ -561,7 +532,7 @@ mod tests {
             unit_keys: vec![(0, [0xAB; 16])],
             read_data_key: None,
         };
-        let original = scrambled_region(aacs::ALIGNED_UNIT_LEN);
+        let original = scrambled_region(aacs::content::ALIGNED_UNIT_LEN);
 
         // base_lba 0, content = [(100,10)] ⇒ the unit at LBA 0 is OUTSIDE content.
         let mut buf = original.clone();
@@ -581,7 +552,7 @@ mod tests {
             decrypt_sectors_in_content(&mut buf2, &mut keys, 0, 100, &[(100, 10)]).unwrap();
         assert_eq!(
             dropped2,
-            aacs::ALIGNED_UNIT_LEN,
+            aacs::content::ALIGNED_UNIT_LEN,
             "an undecryptable CONTENT unit IS counted as loss"
         );
     }
@@ -594,12 +565,12 @@ mod tests {
             unit_keys: vec![(0, [0xAB; 16])],
             read_data_key: None,
         };
-        let mut buf = scrambled_region(2 * aacs::ALIGNED_UNIT_LEN);
+        let mut buf = scrambled_region(2 * aacs::content::ALIGNED_UNIT_LEN);
         // unit0 @ LBA 0 (clear/skip), unit1 @ LBA 3 (content). Content = [(3,3)].
         let dropped = decrypt_sectors_in_content(&mut buf, &mut keys, 0, 0, &[(3, 3)]).unwrap();
         assert_eq!(
             dropped,
-            aacs::ALIGNED_UNIT_LEN,
+            aacs::content::ALIGNED_UNIT_LEN,
             "only the in-content unit (unit1) is checked; clear unit0 is skipped"
         );
     }
@@ -613,7 +584,7 @@ mod tests {
             read_data_key: None,
         };
         let mut keys_u = keys_g.clone();
-        let original = scrambled_region(aacs::ALIGNED_UNIT_LEN);
+        let original = scrambled_region(aacs::content::ALIGNED_UNIT_LEN);
         let mut g = original.clone();
         let mut u = original.clone();
         let gated = decrypt_sectors_in_content(&mut g, &mut keys_g, 0, 0, &[(0, 3)]).unwrap();
@@ -662,7 +633,7 @@ mod tests {
             unit_keys: vec![(0, [0xAB; 16])],
             read_data_key: None,
         };
-        let original = scrambled_region(aacs::ALIGNED_UNIT_LEN);
+        let original = scrambled_region(aacs::content::ALIGNED_UNIT_LEN);
         let mut buf = original.clone();
         let dropped = decrypt_sectors_in_content(&mut buf, &mut keys, 0, 0, &[]).unwrap();
         assert_eq!(
@@ -680,7 +651,7 @@ mod tests {
             unit_keys: vec![(0, [0xAB; 16])],
             read_data_key: None,
         };
-        let original = clear_ts_region(aacs::ALIGNED_UNIT_LEN);
+        let original = clear_ts_region(aacs::content::ALIGNED_UNIT_LEN);
         let mut buf = original.clone();
         let dropped = decrypt_sectors_in_content(&mut buf, &mut keys, 0, 0, &[(0, 3)]).unwrap();
         assert_eq!(dropped, 0, "a clear in-content unit is not ciphertext");
@@ -691,7 +662,7 @@ mod tests {
     #[test]
     fn content_gate_none_keys_is_noop() {
         let mut keys = DecryptKeys::None;
-        let original = scrambled_region(aacs::ALIGNED_UNIT_LEN);
+        let original = scrambled_region(aacs::content::ALIGNED_UNIT_LEN);
         let mut buf = original.clone();
         let dropped = decrypt_sectors_in_content(&mut buf, &mut keys, 0, 0, &[(0, 3)]).unwrap();
         assert_eq!(dropped, 0);
@@ -713,6 +684,83 @@ mod tests {
         );
     }
 
+    /// Build a Stevenson-crackable scrambled CSS sector for `title_key` (mirrors
+    /// `crackable_sector` in the css::mod tests): a periodic run in the clear
+    /// header continues past 0x80 into the encrypted region, so
+    /// `stevenson::crack_title_key` recovers the key. Distinct `seed` values give
+    /// two sectors different cribs, standing in for two VOB regions.
+    fn crackable_css_sector(title_key: &[u8; 5], seed: &[u8; 5]) -> Vec<u8> {
+        const RUN_START: usize = 0x59;
+        const SEED_OFFSET: usize = 0x54;
+        const PERIOD: usize = 8;
+        let mut plaintext = vec![0u8; 2048];
+        plaintext[0x00..0x04].copy_from_slice(&css::PACK_START);
+        plaintext[0x14] = 0x10; // scramble flag
+        let pat: Vec<u8> = (0..PERIOD)
+            .map(|k| (0xA0u8.wrapping_add(k as u8)) ^ 0x5A)
+            .collect();
+        for (i, b) in plaintext.iter_mut().enumerate().skip(RUN_START) {
+            *b = pat[i % PERIOD];
+        }
+        plaintext[SEED_OFFSET..SEED_OFFSET + 5].copy_from_slice(seed);
+        css::lfsr::scramble_sector(title_key, &mut plaintext);
+        plaintext
+    }
+
+    /// CHARACTERIZATION (recovery refactor safety net): the CSS arm's per-region
+    /// re-crack (the `title_key` cache is stale for a new VOB region → restore
+    /// ciphertext, `crack_title_key` this sector, re-descramble). Two crackable
+    /// sectors scrambled under DIFFERENT keys sit back-to-back; the cache is
+    /// primed to the FIRST key. Sector 0 rides the cache (crib matches); sector 1
+    /// must trip the crib mismatch and re-crack to its own key. Both must land
+    /// correct plaintext, and the cache must end on region 1's key.
+    ///
+    /// This behaviour currently lives inline in `decrypt_sectors` (the `Css`
+    /// arm). It is the delicate logic the recovery refactor will move to the
+    /// input-stream seam, so it must stay green byte-for-byte across that move.
+    #[test]
+    fn css_region_change_recracks_the_title_key() {
+        let key_a = [0x11, 0x22, 0x33, 0x44, 0x55];
+        let key_b = [0xAA, 0xBB, 0xCC, 0xDD, 0xEE];
+        let sector_a = crackable_css_sector(&key_a, &[0x01, 0x02, 0x03, 0x04, 0x05]);
+        let sector_b = crackable_css_sector(&key_b, &[0x09, 0x08, 0x07, 0x06, 0x05]);
+
+        // Expected plaintext bodies: each sector descrambled under its true key.
+        let mut plain_a = sector_a.clone();
+        css::lfsr::descramble_sector(&key_a, &mut plain_a);
+        let mut plain_b = sector_b.clone();
+        css::lfsr::descramble_sector(&key_b, &mut plain_b);
+
+        let mut buf = Vec::with_capacity(4096);
+        buf.extend_from_slice(&sector_a);
+        buf.extend_from_slice(&sector_b);
+
+        // Cache primed to region A's key (as if A was the last crack). CSS
+        // descramble-and-rekey lives in `css::descramble_region` (the recovery
+        // seam calls it); the region change must re-crack region B's key.
+        let mut ended = key_a;
+        css::descramble_region(&mut buf, &mut ended);
+
+        assert_eq!(
+            &buf[0x80..2048],
+            &plain_a[0x80..2048],
+            "sector 0 rides the cached key (crib matches, no re-crack)"
+        );
+        assert_eq!(
+            &buf[2048 + 0x80..4096],
+            &plain_b[0x80..2048],
+            "sector 1 re-cracks its own region key and descrambles correctly"
+        );
+        // The cache must have advanced to a key that descrambles region B.
+        let mut check_b = sector_b.clone();
+        css::lfsr::descramble_sector(&ended, &mut check_b);
+        assert_eq!(
+            &check_b[0x80..2048],
+            &plain_b[0x80..2048],
+            "the ended cache key must round-trip region B's body"
+        );
+    }
+
     /// Mixed 3-unit buffer: only the in-content SCRAMBLED unit is counted; an
     /// in-content CLEAR unit and an out-of-content SCRAMBLED unit are both skipped.
     #[test]
@@ -721,7 +769,7 @@ mod tests {
             unit_keys: vec![(0, [0xAB; 16])],
             read_data_key: None,
         };
-        let u = aacs::ALIGNED_UNIT_LEN;
+        let u = aacs::content::ALIGNED_UNIT_LEN;
         let mut buf = vec![0u8; 3 * u];
         buf[..u].copy_from_slice(&scrambled_region(u)); // unit0 @ LBA0 scrambled
         buf[u..2 * u].copy_from_slice(&clear_ts_region(u)); // unit1 @ LBA3 clear
@@ -738,10 +786,14 @@ mod tests {
             unit_keys: vec![(0, [0xAB; 16])],
             read_data_key: None,
         };
-        let mut buf = scrambled_region(2 * aacs::ALIGNED_UNIT_LEN);
+        let mut buf = scrambled_region(2 * aacs::content::ALIGNED_UNIT_LEN);
         // unit0 @ LBA0 content, unit1 @ LBA3 out. Content = [(0,3)].
         let dropped = decrypt_sectors_in_content(&mut buf, &mut keys, 0, 0, &[(0, 3)]).unwrap();
-        assert_eq!(dropped, aacs::ALIGNED_UNIT_LEN, "only unit0 counts");
+        assert_eq!(
+            dropped,
+            aacs::content::ALIGNED_UNIT_LEN,
+            "only unit0 counts"
+        );
     }
 
     /// The trailing-partial reject is ALSO content-gated: a scrambled partial
@@ -755,7 +807,7 @@ mod tests {
         };
         // One full clear unit + a scrambled single-sector partial, all OUTSIDE
         // content → the partial must be tolerated (Ok), not DecryptFailed.
-        let mut buf = clear_ts_region(aacs::ALIGNED_UNIT_LEN);
+        let mut buf = clear_ts_region(aacs::content::ALIGNED_UNIT_LEN);
         buf.extend_from_slice(&scrambled_region(2048));
         // content far away → both the full unit and the partial are non-content.
         let res = decrypt_sectors_in_content(&mut buf, &mut keys, 0, 0, &[(1000, 3)]);
@@ -776,7 +828,7 @@ mod tests {
             read_data_key: None,
         };
         // One full scrambled unit + a 2048-byte (single-sector) CLEAR tail.
-        let unit = scrambled_region(aacs::ALIGNED_UNIT_LEN);
+        let unit = scrambled_region(aacs::content::ALIGNED_UNIT_LEN);
         let tail = clear_ts_region(2048);
         let mut buf = unit;
         buf.extend_from_slice(&tail);
@@ -784,7 +836,7 @@ mod tests {
         decrypt_sectors(&mut buf, &mut keys, 0).expect("clear trailing partial is Ok");
 
         assert_eq!(
-            &buf[aacs::ALIGNED_UNIT_LEN..],
+            &buf[aacs::content::ALIGNED_UNIT_LEN..],
             &tail[..],
             "clear trailing partial unit must be left unchanged"
         );
@@ -801,7 +853,7 @@ mod tests {
             read_data_key: None,
         };
         // One full unit + a 4096-byte (two-sector) SCRAMBLED tail.
-        let unit = clear_ts_region(aacs::ALIGNED_UNIT_LEN);
+        let unit = clear_ts_region(aacs::content::ALIGNED_UNIT_LEN);
         let tail = scrambled_region(4096);
         let mut buf = unit;
         buf.extend_from_slice(&tail);
@@ -835,7 +887,7 @@ mod tests {
             unit_keys: vec![(0, [0xAB; 16])],
             read_data_key: None,
         };
-        let mut buf = clear_ts_region(aacs::ALIGNED_UNIT_LEN * 2);
+        let mut buf = clear_ts_region(aacs::content::ALIGNED_UNIT_LEN * 2);
         let snapshot = buf.clone();
 
         decrypt_sectors(&mut buf, &mut keys, 0).expect("exact-multiple buffer is Ok");
@@ -908,11 +960,12 @@ mod tests {
     /// fixed wrong key -> the body no longer matches the plaintext.
     #[test]
     fn css_descrambles_with_title_key() {
-        let title_key = [0x42, 0x13, 0x37, 0xBE, 0xEF];
+        let mut title_key = [0x42, 0x13, 0x37, 0xBE, 0xEF];
         let seed = [0xDE, 0xAD, 0xBE, 0xEF, 0x42];
         let (mut sector, plaintext) = make_css_sector(&title_key, &seed, 0xA5);
-        let mut keys = DecryptKeys::Css { title_key };
-        decrypt_sectors(&mut sector, &mut keys, 0).expect("CSS decrypt is Ok");
+        // CSS descramble lives in `css::descramble_region` (the recovery seam
+        // calls it); `decrypt_sectors` only flags CSS sectors for recovery.
+        css::descramble_region(&mut sector, &mut title_key);
         assert_eq!(
             &sector[0x80..2048],
             &plaintext[0x80..2048],
@@ -941,8 +994,8 @@ mod tests {
         let (s1, p1) = make_css_sector(&title_key, &[0x66, 0x77, 0x88, 0x99, 0xAA], 0xC3);
         let mut buf = s0;
         buf.extend_from_slice(&s1);
-        let mut keys = DecryptKeys::Css { title_key };
-        decrypt_sectors(&mut buf, &mut keys, 0).expect("CSS multi-sector decrypt is Ok");
+        let mut title_key = title_key;
+        css::descramble_region(&mut buf, &mut title_key);
         assert_eq!(
             &buf[0x80..2048],
             &p0[0x80..2048],
@@ -1020,8 +1073,8 @@ mod tests {
         buf.extend_from_slice(&s1);
 
         // Cache primed to key_a only — exactly what the one-shot scan crack yields.
-        let mut keys = DecryptKeys::Css { title_key: key_a };
-        decrypt_sectors(&mut buf, &mut keys, 0).expect("CSS multi-region decrypt is Ok");
+        let mut title_key = key_a;
+        css::descramble_region(&mut buf, &mut title_key);
 
         assert_eq!(
             &buf[0x80..2048],
@@ -1034,13 +1087,10 @@ mod tests {
             "region B sector must descramble after the path re-cracks its own key"
         );
         // The cache must have advanced to region B's key.
-        match keys {
-            DecryptKeys::Css { title_key } => assert_eq!(
-                title_key, key_b,
-                "cache must hold region B's key after the rekey"
-            ),
-            _ => unreachable!(),
-        }
+        assert_eq!(
+            title_key, key_b,
+            "cache must hold region B's key after the rekey"
+        );
     }
 
     /// The CSS path leaves UNSCRAMBLED sectors (flag clear) byte-for-byte
@@ -1092,7 +1142,7 @@ mod tests {
             unit_keys: vec![(0, [0xAB; 16])],
             read_data_key: None,
         };
-        let mut buf = clear_ts_region(aacs::ALIGNED_UNIT_LEN);
+        let mut buf = clear_ts_region(aacs::content::ALIGNED_UNIT_LEN);
         let err = decrypt_sectors(&mut buf, &mut keys, 5)
             .expect_err("unit_key_idx 5 is out of range for a 1-key list");
         assert_eq!(
@@ -1112,7 +1162,7 @@ mod tests {
             unit_keys: vec![],
             read_data_key: None,
         };
-        let mut buf = clear_ts_region(aacs::ALIGNED_UNIT_LEN);
+        let mut buf = clear_ts_region(aacs::content::ALIGNED_UNIT_LEN);
         let err = decrypt_sectors(&mut buf, &mut keys, 0).expect_err("empty unit_keys must error");
         assert_eq!(err.code(), crate::error::Error::DecryptFailed.code());
     }
@@ -1120,8 +1170,8 @@ mod tests {
     // ── Multi-CPS-unit key selection ──────────────────────────────────────
 
     /// Encrypt an aligned unit with the AACS algorithm run in reverse so that
-    /// `aacs::decrypt_unit` with the same key recovers the plaintext. Mirrors
-    /// the `aacs_encrypt_unit` helper in `aacs::decrypt::tests`.
+    /// `aacs::content::decrypt_unit` with the same key recovers the plaintext. Mirrors
+    /// the `aacs_encrypt_unit` helper in `aacs::content::tests`.
     fn aacs_encrypt_unit_for_test(unit: &mut [u8], unit_key: &[u8; 16]) {
         use aes::Aes128;
         use aes::cipher::{BlockEncrypt, KeyInit, generic_array::GenericArray};
@@ -1129,14 +1179,14 @@ mod tests {
         // the per-unit key so the recovered plaintext header matches.
         unit[0] |= 0xC0;
         let header: [u8; 16] = unit[..16].try_into().unwrap();
-        let derived = crate::aacs::decrypt::aes_ecb_encrypt(unit_key, &header);
+        let derived = crate::aacs::crypto::aes_ecb_encrypt(unit_key, &header);
         let mut k = [0u8; 16];
         for i in 0..16 {
             k[i] = derived[i] ^ header[i];
         }
         let cipher = Aes128::new(GenericArray::from_slice(&k));
-        let mut prev = crate::aacs::decrypt::AACS_IV;
-        let num_blocks = (aacs::ALIGNED_UNIT_LEN - 16) / 16;
+        let mut prev = crate::aacs::crypto::AACS_IV;
+        let num_blocks = (aacs::content::ALIGNED_UNIT_LEN - 16) / 16;
         for i in 0..num_blocks {
             let off = 16 + i * 16;
             for j in 0..16 {
@@ -1153,9 +1203,9 @@ mod tests {
     /// (offset 4 + k*192) so `ts_sync_destroyed` reports false and
     /// `decrypt_unit` verifies it as clear after decryption.
     fn clear_ts_unit() -> Vec<u8> {
-        let mut unit = vec![0u8; aacs::ALIGNED_UNIT_LEN];
+        let mut unit = vec![0u8; aacs::content::ALIGNED_UNIT_LEN];
         let mut off = 4;
-        while off < aacs::ALIGNED_UNIT_LEN {
+        while off < aacs::content::ALIGNED_UNIT_LEN {
             unit[off] = 0x47;
             off += 192;
         }
@@ -1171,7 +1221,7 @@ mod tests {
     /// garbage for content under key ≥ 1. The fix tries every key and
     /// accepts the one whose output passes the TS-sync verify.
     ///
-    /// Grounding: `for idx in try_order { … if aacs::decrypt_unit(&mut attempt, key) { … } }`
+    /// Grounding: `for idx in try_order { … if aacs::content::decrypt_unit(&mut attempt, key) { … } }`
     /// Mutation: revert to the pre-fix `decrypt_unit_full(chunk, &uk, …)` where
     /// `uk = raw_keys[unit_key_idx]` (always key 0) → the unit comes out as
     /// garbled bytes that still look scrambled, failing the `!ts_sync_destroyed`
@@ -1185,7 +1235,7 @@ mod tests {
         let mut unit = clear_ts_unit();
         aacs_encrypt_unit_for_test(&mut unit, &key1);
         assert!(
-            aacs::ts_sync_destroyed(&unit),
+            aacs::content::ts_sync_destroyed(&unit),
             "encrypted unit must look scrambled before decrypt"
         );
 
@@ -1199,13 +1249,13 @@ mod tests {
         decrypt_sectors(&mut buf, &mut keys, 0).expect("multi-CPS decrypt must succeed");
 
         assert!(
-            !aacs::ts_sync_destroyed(&buf),
+            !aacs::content::ts_sync_destroyed(&buf),
             "unit encrypted under key1 must be fully decrypted (TS syncs restored)"
         );
         // Every sync position must carry 0x47.
         assert_eq!(
-            aacs::ts_sync_count(&buf),
-            aacs::ts_packet_total(&buf),
+            aacs::content::ts_sync_count(&buf),
+            aacs::content::ts_packet_total(&buf),
             "all TS sync bytes must be restored after decrypting under key1"
         );
     }
@@ -1230,12 +1280,12 @@ mod tests {
         let mut buf = unit;
         decrypt_sectors(&mut buf, &mut keys, 0).expect("single-key disc must decrypt");
         assert!(
-            !aacs::ts_sync_destroyed(&buf),
+            !aacs::content::ts_sync_destroyed(&buf),
             "single-key disc: TS syncs must be restored"
         );
         assert_eq!(
-            aacs::ts_sync_count(&buf),
-            aacs::ts_packet_total(&buf),
+            aacs::content::ts_sync_count(&buf),
+            aacs::content::ts_packet_total(&buf),
             "all TS sync bytes must be restored for single-key disc"
         );
     }
@@ -1263,7 +1313,7 @@ mod tests {
         aacs_encrypt_unit_for_test(&mut unit, &real_key);
         let ciphertext = unit.clone();
         assert!(
-            aacs::ts_sync_destroyed(&unit),
+            aacs::content::ts_sync_destroyed(&unit),
             "encrypted unit must look scrambled going in"
         );
 
@@ -1277,7 +1327,7 @@ mod tests {
 
         assert_eq!(
             dropped,
-            aacs::ALIGNED_UNIT_LEN,
+            aacs::content::ALIGNED_UNIT_LEN,
             "the whole scrambled unit must be reported as dropped when no key validates"
         );
         assert_eq!(
@@ -1306,7 +1356,7 @@ mod tests {
         aacs_encrypt_unit_for_test(&mut unit_b, &wrong);
         let unit_b_ciphertext = unit_b.clone();
 
-        let mut buf = Vec::with_capacity(2 * aacs::ALIGNED_UNIT_LEN);
+        let mut buf = Vec::with_capacity(2 * aacs::content::ALIGNED_UNIT_LEN);
         buf.extend_from_slice(&unit_a);
         buf.extend_from_slice(&unit_b);
 
@@ -1318,15 +1368,15 @@ mod tests {
 
         assert_eq!(
             dropped,
-            aacs::ALIGNED_UNIT_LEN,
+            aacs::content::ALIGNED_UNIT_LEN,
             "exactly one unit's worth of bytes must be reported dropped"
         );
         assert!(
-            !aacs::ts_sync_destroyed(&buf[..aacs::ALIGNED_UNIT_LEN]),
+            !aacs::content::ts_sync_destroyed(&buf[..aacs::content::ALIGNED_UNIT_LEN]),
             "the decryptable unit must come out clear"
         );
         assert_eq!(
-            &buf[aacs::ALIGNED_UNIT_LEN..],
+            &buf[aacs::content::ALIGNED_UNIT_LEN..],
             &unit_b_ciphertext[..],
             "the undecryptable unit must be restored to ciphertext"
         );

src/disc/bluray.rs

@@ -6,6 +6,18 @@ use crate::mpls;
 use crate::sector::SectorSource;
 use crate::udf;
 
+/// Stream-file extensions probed for a BD-family playlist clip, in priority
+/// order. A clip is normally `.m2ts`; AACS 2.1 (FMTS) discs name the main feature
+/// `.fmts` (an M2TS transport stream plus forensic variant segments) and 3D discs
+/// use `.ssif`. `.m2ts` is tried first, so a normal clip is unaffected — the
+/// fallback only runs when `.m2ts` is absent (exactly when `file_extents` errors).
+///
+/// Scope: these are all variants that live in `BDMV/STREAM/` and are reached
+/// through an MPLS playlist. HD-DVD's `.evo` does NOT belong here — HD-DVD is a
+/// different tree (`HVDVD_TS/`) with `.XPL` playlists and needs its own
+/// enumerator (a peer to `parse_playlist`), not another extension in this list.
+const CLIP_STREAM_EXTS: [&str; 3] = ["m2ts", "fmts", "ssif"];
+
 impl Disc {
     /// Scan Blu-ray titles from MPLS playlists.
     pub(super) fn scan_bluray_titles(
@@ -60,6 +72,11 @@ impl Disc {
         // Parse each clip for size, duration, and sector extents
         let mut extents = Vec::new();
         let mut total_size: u64 = 0;
+        // Set when any clip resolves to a STREAM/SSIF/<clip>.ssif — a Blu-ray 3D
+        // interleaved stream carrying both the base (left) and MVC dependent
+        // (right) views. Drives reading the SSIF for both eyes and adding the
+        // dependent-view stream below.
+        let mut is_3d = false;
         let mut clips = Vec::with_capacity(parsed.play_items.len());
         // BD playlists legally reference the same .m2ts clip_id from
         // multiple PlayItems (multi-angle, seamless splits, looped
@@ -73,22 +90,49 @@ impl Disc {
         for play_item in &parsed.play_items {
             let clip_dur = play_item.out_time.saturating_sub(play_item.in_time) as f64 / 45000.0;
             let mut pkt_count: u32 = 0;
-            let first_ref = seen_clips.insert(play_item.clip_id.clone());
 
             let clpi_path = format!("/BDMV/CLIPINF/{}.clpi", play_item.clip_id);
             if let Ok(clpi_data) = udf_fs.read_file(reader, &clpi_path) {
                 if let Ok(clip_info) = clpi::parse(&clpi_data) {
                     pkt_count = clip_info.source_packet_count;
 
+                    // Mark the clip seen ONLY after its .clpi parses — a transient
+                    // read/parse failure on the first PlayItem referencing a clip
+                    // must not permanently suppress its extents/size for a later
+                    // PlayItem referencing the same clip that succeeds.
+                    let first_ref = seen_clips.insert(play_item.clip_id.clone());
+
                     // Only fetch/push the physical extents and add to the
                     // total size the first time this clip_id is seen.
                     if first_ref {
                         total_size += pkt_count as u64 * 192;
 
-                        // Get m2ts file extents from UDF allocation descriptors.
+                        // Get stream file extents from UDF allocation descriptors.
                         // Dual-layer discs split files across layers — UDF knows the real layout.
-                        let m2ts_path = format!("/BDMV/STREAM/{}.m2ts", play_item.clip_id);
-                        if let Ok(file_exts) = udf_fs.file_extents(reader, &m2ts_path) {
+                        //
+                        // The clip's stream file is normally `.m2ts`, but AACS 2.1
+                        // (FMTS) discs name the main feature `.fmts` and 3D discs
+                        // use `.ssif` (see [`CLIP_STREAM_EXTS`]). A normal `.m2ts`
+                        // clip is unchanged — the fallback only runs when `.m2ts`
+                        // is absent, which is exactly when `file_extents` errors.
+                        // 3D discs interleave the left (base) and right (MVC
+                        // dependent) views in STREAM/SSIF/<clip>.ssif — note the
+                        // SSIF/ subdir. Prefer it when present: the SSIF is one
+                        // transport stream carrying BOTH eyes on distinct PIDs,
+                        // so muxing it captures the full 3D. 2D clips fall back to
+                        // the base .m2ts / .fmts as before.
+                        let ssif = format!("/BDMV/STREAM/SSIF/{}.ssif", play_item.clip_id);
+                        let file_exts = match udf_fs.file_extents(reader, &ssif) {
+                            Ok(exts) => {
+                                is_3d = true;
+                                Some(exts)
+                            }
+                            Err(_) => CLIP_STREAM_EXTS.iter().find_map(|ext| {
+                                let path = format!("/BDMV/STREAM/{}.{}", play_item.clip_id, ext);
+                                udf_fs.file_extents(reader, &path).ok()
+                            }),
+                        };
+                        if let Some(file_exts) = file_exts {
                             for (lba, sectors) in file_exts {
                                 if sectors > 0 && lba > 0 {
                                     extents.push(Extent {
@@ -112,7 +156,7 @@ impl Disc {
         }
 
         // Build streams from STN table
-        let streams: Vec<Stream> = parsed
+        let mut streams: Vec<Stream> = parsed
             .streams
             .iter()
             .filter_map(|s| {
@@ -206,6 +250,42 @@ impl Disc {
             })
             .collect();
 
+        // 3D: add the MVC dependent (right-eye) video stream. The base STN table
+        // lists only the left-eye video; the dependent view is a second video
+        // PID (stream_type 0x20) carried in the SSIF. The on-disc PAT/PMT are
+        // AACS-encrypted (unreadable pre-key) and the base STN omits the
+        // dependent view (it lives in the MPLS STN_table_SS), so we use the
+        // BD-3D PID convention: dependent = base-view video PID + 1
+        // (e.g. 0x1011 -> 0x1012). Reading the SSIF (above) provides its packets.
+        //
+        // Limitation: `is_3d` latches per PLAYLIST, not per clip. A playlist that
+        // mixed a 3D clip (has an SSIF) with a 2D clip (no SSIF) would tag the
+        // whole title 3D; the 2D clip's frames then mux as plain Blocks (no
+        // dependent PID → no BlockAdditional) under a track that still advertises
+        // the mvcC mapping. That output is valid (per-frame BlockAdditional is
+        // optional) but over-claims 3D for those frames. Real 3D main-feature
+        // playlists are single-clip or uniformly 3D, so this is not exercised;
+        // per-clip 3D would need per-clip stream sets (a larger change).
+        if is_3d {
+            if let Some(base) = streams.iter().find_map(|s| match s {
+                Stream::Video(v) => Some(v.clone()),
+                _ => None,
+            }) {
+                let dep_pid = base.pid.wrapping_add(1);
+                let have_dep = streams
+                    .iter()
+                    .any(|s| matches!(s, Stream::Video(v) if v.pid == dep_pid));
+                if !have_dep {
+                    streams.push(Stream::Video(VideoStream {
+                        pid: dep_pid,
+                        secondary: true,
+                        label: crate::disc::MVC_DEPENDENT_LABEL.to_string(),
+                        ..base
+                    }));
+                }
+            }
+        }
+
         // Convert marks to chapters. mark_type == 1 is an entry-mark
         // (chapter); type 2 is a link point and type 0 is reserved, so
         // neither is a chapter.
@@ -314,256 +394,7 @@ impl Disc {
 #[cfg(test)]
 mod tests {
     use super::*;
-    use crate::sector::SectorSource;
-    use std::collections::HashMap;
-
-    // ---------------------------------------------------------------
-    // In-memory disc backing store
-    // ---------------------------------------------------------------
-
-    /// In-memory SectorSource backed by an absolute-LBA → 2048-byte
-    /// sector map. Unmapped sectors read as zeroes (matches a freshly
-    /// formatted region). Mirrors the `MapReader` used in `udf.rs`
-    /// tests so fixtures are byte-for-byte interoperable.
-    struct MemDisc {
-        sectors: HashMap<u32, [u8; 2048]>,
-    }
-
-    impl MemDisc {
-        fn new() -> Self {
-            Self {
-                sectors: HashMap::new(),
-            }
-        }
-        fn put(&mut self, lba: u32, data: [u8; 2048]) {
-            self.sectors.insert(lba, data);
-        }
-        /// Write arbitrary-length bytes starting at `lba`, splitting across
-        /// consecutive 2048-byte sectors (zero-padded last sector).
-        fn put_bytes(&mut self, lba: u32, bytes: &[u8]) {
-            for (i, chunk) in bytes.chunks(2048).enumerate() {
-                let mut s = [0u8; 2048];
-                s[..chunk.len()].copy_from_slice(chunk);
-                self.put(lba + i as u32, s);
-            }
-        }
-    }
-
-    impl SectorSource for MemDisc {
-        fn read_sectors(
-            &mut self,
-            lba: u32,
-            count: u16,
-            buf: &mut [u8],
-            _recovery: bool,
-        ) -> crate::error::Result<usize> {
-            let need = count as usize * 2048;
-            for i in 0..count as u32 {
-                let off = i as usize * 2048;
-                let s = self.sectors.get(&(lba + i)).copied().unwrap_or([0u8; 2048]);
-                buf[off..off + 2048].copy_from_slice(&s);
-            }
-            Ok(need)
-        }
-    }
-
-    // ---------------------------------------------------------------
-    // UDF image builder — produces a disc image `udf::read_filesystem`
-    // can navigate. All field offsets are cited from ECMA-167 / the
-    // exact bytes `udf.rs::read_filesystem` reads.
-    // ---------------------------------------------------------------
-
-    /// Fixed layout. PART_START == META_START so file LBAs (physical
-    /// partition relative) and ICB/dir LBAs (metadata relative) share
-    /// one address space — both resolve to abs = PART_START + lba. This
-    /// keeps fixtures small; `read_filesystem` takes the single-partition
-    /// path (num_partition_maps == 1) so no metadata-partition file is
-    /// needed.
-    const PART_START: u32 = 2000;
-
-    /// One file's on-disc placement: metadata LBA of its ICB, the LBA of
-    /// its (single contiguous) data extent, byte length, and whether the
-    /// ICB encodes its allocation descriptor as a Long AD (16-byte, the
-    /// real BD-ROM .m2ts layout) vs Short AD (8-byte).
-    struct FileSpec {
-        name: String,
-        icb_lba: u32,
-        data_lba: u32,
-        size: u32,
-        long_ad: bool,
-        /// Optional explicit file contents written at `data_lba`.
-        contents: Vec<u8>,
-    }
-
-    /// A directory node for the builder: its ICB LBA, the LBA where its
-    /// FID list lives, child files, and child subdirectories.
-    struct DirSpec {
-        name: String,
-        icb_lba: u32,
-        dir_data_lba: u32,
-        files: Vec<FileSpec>,
-        subdirs: Vec<DirSpec>,
-    }
-
-    /// Build an Extended File Entry ICB (tag 266) with one allocation
-    /// descriptor. Offsets per `udf.rs`: tag@0, ICB-tag flags@34,
-    /// info_length(u64)@56, l_ea@208, l_ad@212, ADs@216.
-    fn build_file_icb(size: u32, data_lba: u32, long_ad: bool) -> [u8; 2048] {
-        let mut s = [0u8; 2048];
-        s[0..2].copy_from_slice(&266u16.to_le_bytes()); // Extended File Entry
-        if long_ad {
-            // ICB Tag flags low 3 bits = 1 → Long AD (16-byte stride).
-            s[34..36].copy_from_slice(&1u16.to_le_bytes());
-        }
-        s[56..64].copy_from_slice(&(size as u64).to_le_bytes()); // info_length
-        s[208..212].copy_from_slice(&0u32.to_le_bytes()); // l_ea
-        let ad_size: u32 = if long_ad { 16 } else { 8 };
-        s[212..216].copy_from_slice(&ad_size.to_le_bytes()); // l_ad
-        // Short/Long AD share length(4)@216 | lba(4)@220. extent_type 0
-        // (recorded) is top 2 bits = 0, so raw == len.
-        s[216..220].copy_from_slice(&(size & 0x3FFF_FFFF).to_le_bytes());
-        s[220..224].copy_from_slice(&data_lba.to_le_bytes());
-        // Long AD's part_ref(2)@224 + impl_use(6)@226 stay zero.
-        s
-    }
-
-    /// Build a directory ICB (tag 266) whose single short AD points at the
-    /// directory's FID data.
-    fn build_dir_icb(dir_data_lba: u32, dir_data_len: u32) -> [u8; 2048] {
-        build_file_icb(dir_data_len, dir_data_lba, false)
-    }
-
-    /// Append one File Identifier Descriptor (tag 257) to `buf`.
-    /// Layout per `read_directory`: tag@0, file_chars@18, l_fi@19,
-    /// ICB long_ad extent_location(LBA)@24, l_iu(u16)@36, name@(38+l_iu).
-    /// Name uses UDF compression-id 8 (8-bit ASCII), so the on-disc name
-    /// field is `[0x08, ascii_bytes...]` and l_fi = 1 + ascii.len().
-    fn push_fid(buf: &mut Vec<u8>, name: &str, icb_lba: u32, is_dir: bool, is_parent: bool) {
-        let start = buf.len();
-        let name_field: Vec<u8> = if is_parent {
-            Vec::new()
-        } else {
-            let mut v = vec![0x08u8];
-            v.extend_from_slice(name.as_bytes());
-            v
-        };
-        let l_fi = name_field.len();
-        let mut fid = vec![0u8; 38];
-        fid[0..2].copy_from_slice(&257u16.to_le_bytes()); // FID tag
-        let mut file_chars = 0u8;
-        if is_dir {
-            file_chars |= 0x02;
-        }
-        if is_parent {
-            file_chars |= 0x08;
-        }
-        fid[18] = file_chars;
-        fid[19] = l_fi as u8;
-        // ICB long_ad: extent_location LBA at offset 24.
-        fid[24..28].copy_from_slice(&icb_lba.to_le_bytes());
-        // l_iu (u16) at offset 36 = 0.
-        fid[36..38].copy_from_slice(&0u16.to_le_bytes());
-        buf.extend_from_slice(&fid);
-        buf.extend_from_slice(&name_field);
-        // Pad to 4-byte alignment (FID stride = (38 + l_iu + l_fi + 3) & !3).
-        let used = buf.len() - start;
-        let pad = (used + 3) & !3;
-        buf.resize(start + pad, 0);
-    }
-
-    /// Recursively lay a DirSpec (and children) into the MemDisc, writing
-    /// directory ICBs, FID lists, file ICBs, and file data.
-    fn lay_dir(disc: &mut MemDisc, dir: &DirSpec) {
-        let mut fids = Vec::new();
-        // Parent entry first (file_chars bit 0x08) — skipped by the parser
-        // but present on real discs.
-        push_fid(&mut fids, "", dir.icb_lba, true, true);
-        for f in &dir.files {
-            push_fid(&mut fids, &f.name, f.icb_lba, false, false);
-            disc.put(
-                PART_START + f.icb_lba,
-                build_file_icb(f.size, f.data_lba, f.long_ad),
-            );
-            if !f.contents.is_empty() {
-                disc.put_bytes(PART_START + f.data_lba, &f.contents);
-            }
-        }
-        for sub in &dir.subdirs {
-            push_fid(&mut fids, &sub.name, sub.icb_lba, true, false);
-        }
-        disc.put(
-            PART_START + dir.icb_lba,
-            build_dir_icb(dir.dir_data_lba, fids.len() as u32),
-        );
-        disc.put_bytes(PART_START + dir.dir_data_lba, &fids);
-        for sub in &dir.subdirs {
-            lay_dir(disc, sub);
-        }
-    }
-
-    /// Build the static UDF anchor/VDS/FSD structure so `read_filesystem`
-    /// reaches `root_icb_lba`. Single partition map → metadata_start ==
-    /// partition_start == PART_START.
-    fn build_udf_skeleton(disc: &mut MemDisc, root_icb_lba: u32) {
-        // AVDP at sector 256, tag 2 (ECMA-167 §10.2).
-        let mut avdp = [0u8; 2048];
-        avdp[0..2].copy_from_slice(&2u16.to_le_bytes());
-        disc.put(256, avdp);
-
-        // Partition Descriptor (tag 5) at sector 32: partition_start@188.
-        let mut pd = [0u8; 2048];
-        pd[0..2].copy_from_slice(&5u16.to_le_bytes());
-        pd[188..192].copy_from_slice(&PART_START.to_le_bytes());
-        disc.put(32, pd);
-
-        // Logical Volume Descriptor (tag 6) at sector 33:
-        // num_partition_maps(u32)@268 = 1 (single map → no metadata part).
-        let mut lvd = [0u8; 2048];
-        lvd[0..2].copy_from_slice(&6u16.to_le_bytes());
-        lvd[268..272].copy_from_slice(&1u32.to_le_bytes());
-        disc.put(33, lvd);
-
-        // Terminating Descriptor (tag 8) at sector 34 → ends VDS scan.
-        let mut td = [0u8; 2048];
-        td[0..2].copy_from_slice(&8u16.to_le_bytes());
-        disc.put(34, td);
-
-        // File Set Descriptor (tag 256) at metadata_start (== PART_START):
-        // root-dir ICB LBA at offset 404 (long_ad extent_location).
-        let mut fsd = [0u8; 2048];
-        fsd[0..2].copy_from_slice(&256u16.to_le_bytes());
-        fsd[404..408].copy_from_slice(&root_icb_lba.to_le_bytes());
-        disc.put(PART_START, fsd);
-    }
-
-    fn file(name: &str, icb_lba: u32, data_lba: u32, size: u32, long_ad: bool) -> FileSpec {
-        FileSpec {
-            name: name.to_string(),
-            icb_lba,
-            data_lba,
-            size,
-            long_ad,
-            contents: Vec::new(),
-        }
-    }
-
-    fn file_with(
-        name: &str,
-        icb_lba: u32,
-        data_lba: u32,
-        contents: Vec<u8>,
-        long_ad: bool,
-    ) -> FileSpec {
-        FileSpec {
-            name: name.to_string(),
-            icb_lba,
-            data_lba,
-            size: contents.len() as u32,
-            long_ad,
-            contents,
-        }
-    }
-
+    use crate::udf::fixture::*;
     // ---------------------------------------------------------------
     // MPLS builder (BD-ROM PlayList spec). Mirrors the layout the
     // `mpls::parse` consumer reads (header@0, PlayList@playlist_start,
@@ -797,13 +628,29 @@ mod tests {
             u32, /*packets*/
             u32, /*data_lba*/
         )],
+    ) -> udf::UdfFs {
+        make_bdmv_fs_ext(disc, clips, "m2ts")
+    }
+
+    /// As [`make_bdmv_fs`] but the STREAM file carries `stream_ext` instead of
+    /// `.m2ts` (e.g. "fmts" for an AACS 2.1 feature clip, "ssif" for 3D) — drives
+    /// the [`CLIP_STREAM_EXTS`] fallback in `parse_playlist`.
+    fn make_bdmv_fs_ext(
+        disc: &mut MemDisc,
+        clips: &[(
+            &str,
+            u32, /*sectors*/
+            u32, /*packets*/
+            u32, /*data_lba*/
+        )],
+        stream_ext: &str,
     ) -> udf::UdfFs {
         // Layout LBAs: pick widely separated values to avoid collisions.
         let mut stream_files = Vec::new();
         let mut clipinf_files = Vec::new();
         let mut icb = 100u32;
         for (name, sectors, packets, data_lba) in clips {
-            let m2ts = format!("{name}.m2ts");
+            let m2ts = format!("{name}.{stream_ext}");
             // Size in bytes — file_extents derives sectors via div_ceil(2048).
             let size = sectors * 2048;
             stream_files.push(file(&m2ts, icb, *data_lba, size, true));
@@ -881,6 +728,37 @@ mod tests {
         assert_eq!(t.clips[0].source_packets, 4000);
     }
 
+    /// AACS 2.1: the feature clip is `00001.fmts`, NOT `.m2ts`. The
+    /// [`CLIP_STREAM_EXTS`] fallback in `parse_playlist` must still resolve the
+    /// physical extent — before the fix the hard-coded `.m2ts` path errored,
+    /// yielding empty extents (a silent empty rip and 0 encrypted samples for key
+    /// resolution). Size still comes from the `.clpi`, which parses regardless.
+    #[test]
+    fn parse_playlist_fmts_clip_resolves_extent() {
+        let mut disc = MemDisc::new();
+        // Only a .fmts stream exists for clip 00001 (no .m2ts on disc).
+        let udf = make_bdmv_fs_ext(&mut disc, &[("00001", 1000, 4000, 5000)], "fmts");
+        let mpls = build_mpls(
+            &[PiSpec {
+                clip_id: *b"00001",
+                in_time: 0,
+                out_time: 60 * 45000,
+            }],
+            (0, 0, 0, 0, 0, 0, 0, 0),
+            &[],
+            &[],
+        );
+        let t = Disc::parse_playlist(&mut disc, &udf, "00001.mpls", &mpls).expect("title");
+        assert_eq!(t.size_bytes, 4000 * 192, "size from .clpi source packets");
+        assert_eq!(
+            t.extents.len(),
+            1,
+            "the .fmts extent must be resolved via fallback"
+        );
+        assert_eq!(t.extents[0].start_lba, PART_START + 5000);
+        assert_eq!(t.extents[0].sector_count, 1000);
+    }
+
     /// THE 0.31.0 DEDUP PATH. A playlist that references the SAME clip_id
     /// from multiple PlayItems (seamless split / looped segment) must count
     /// the physical extents and packet bytes EXACTLY ONCE — mux reads

src/disc/encrypt.rs

@@ -86,9 +86,9 @@ impl AacsCertUnlocker<'_> {
         // MKB generation (best-effort) — forwarded to each source's
         // `host_certs(mkb)` so a source MAY select a generation-appropriate cert
         // (the default impl ignores it). A read failure leaves it `None`.
-        let mkb_gen = aacs::read_mkb_from_drive(session.scsi_mut())
+        let mkb_gen = aacs::inf::read_mkb_from_drive(session.scsi_mut())
             .ok()
-            .and_then(|m| aacs::mkb_version(&m));
+            .and_then(|m| aacs::mkb::mkb_version(&m));
 
         // Host certs are keysource-served, never compiled in — unioned from the
         // explicit `DriveCredentials` and the key-source layer. With ZERO certs
@@ -111,13 +111,13 @@ impl AacsCertUnlocker<'_> {
         // through method calls, so clone the (cheap) identity first.
         let drive_id = session.drive_id.clone();
         let fu_certs = crate::unlock_bridge::map_host_certs(&host_certs);
-        let unlocked = crate::unlock_bridge::run_unlockers(
+        let (_, unlock_res) = crate::unlock_bridge::run_bus(
             session.scsi_mut(),
             &drive_id,
             freemkv_unlock::DiscKind::Aacs,
             &fu_certs,
-        )
-        .map_err(CertUnlockFailure::Unlock)?;
+        );
+        let unlocked = unlock_res.map_err(CertUnlockFailure::Unlock)?;
         // The cert handshake yields a VID on success; its absence is VidUnavailable.
         let Some(volume_id) = unlocked.vid else {
             return Err(CertUnlockFailure::Unlock(UnlockError::VidUnavailable));
@@ -152,10 +152,10 @@ fn unlock_error_to_error(e: &CertUnlockFailure) -> Error {
     }
 }
 
-/// Map a [`CertUnlockFailure`] to a structured [`crate::aacs::UnlockOutcome`]
+/// Map a [`CertUnlockFailure`] to a structured [`crate::aacs::trace::UnlockOutcome`]
 /// for the resolution trace (English-free).
-fn cert_unlock_outcome(e: &CertUnlockFailure) -> crate::aacs::UnlockOutcome {
-    use crate::aacs::UnlockOutcome;
+fn cert_unlock_outcome(e: &CertUnlockFailure) -> crate::aacs::trace::UnlockOutcome {
+    use crate::aacs::trace::UnlockOutcome;
     use freemkv_unlock::UnlockError;
     match e {
         CertUnlockFailure::NoHostCert { mkb } => UnlockOutcome::NoUsableHostCert { mkb: *mkb },
@@ -230,7 +230,10 @@ impl Disc {
     /// `mkb` is the disc's MKB generation when known, forwarded to each source's
     /// [`crate::KeySource::host_certs`] so a source MAY return only
     /// generation-appropriate certs (the default ignores it).
-    fn collect_host_certs(opts: &ScanOptions, mkb: Option<u32>) -> Vec<crate::aacs::HostCert> {
+    fn collect_host_certs(
+        opts: &ScanOptions,
+        mkb: Option<u32>,
+    ) -> Vec<crate::aacs::types::HostCert> {
         // Delegates to the shared cert primitive (the external freemkv-unlock-aacs
         // plugin uses the same one). Kept as a thin Disc method so the existing
         // collect_host_certs_* unit tests and call sites are unchanged.
@@ -312,14 +315,14 @@ impl Disc {
             .read_file(reader, crate::aacs::PATH_UNIT_KEY_RO)
             .or_else(|_| udf_fs.read_file(reader, crate::aacs::PATH_UNIT_KEY_RO_DUPLICATE))
             .map_err(|_| Error::AacsNoKeys)?;
-        let dh = aacs::disc_hash(&uk_ro_data);
+        let dh = aacs::inf::disc_hash(&uk_ro_data);
 
         let cc = udf_fs
             .read_file(reader, crate::aacs::PATH_CONTENT_CERT)
             .or_else(|_| udf_fs.read_file(reader, crate::aacs::PATH_CONTENT_CERT_ALT))
             .ok()
             .as_deref()
-            .and_then(aacs::parse_content_cert);
+            .and_then(aacs::inf::parse_content_cert);
         let bus_encryption = cc.as_ref().map(|c| c.bus_encryption).unwrap_or(false);
         // No-cert default = UHD (V20 stride), matching `read_aacs_version` so the
         // scanned `AacsState.version` and the out-of-band fetch agree. A wrong
@@ -328,7 +331,7 @@ impl Disc {
         let version = cc
             .as_ref()
             .map(|c| c.version.major())
-            .unwrap_or(aacs::AACS_MAJOR_UHD);
+            .unwrap_or(aacs::mkb::AACS_MAJOR_UHD);
 
         // Bus-encryption gate (wrong-keys guard). A bus-encrypted disc (Content
         // Certificate bus-encryption bit set) carries bus encryption on its
@@ -394,12 +397,12 @@ impl Disc {
                 Vec::new()
             }
         };
-        let mkb_ver = aacs::mkb_version(&mkb_bytes);
+        let mkb_ver = aacs::mkb::mkb_version(&mkb_bytes);
 
         tracing::debug!(
             target: "freemkv::disc",
             phase = "scan_aacs_vid_only",
-            disc_hash = %aacs::disc_hash_hex(&dh),
+            disc_hash = %aacs::inf::disc_hash_hex(&dh),
             version,
             bus_encryption,
             has_vid = handshake.is_some(),
@@ -410,7 +413,7 @@ impl Disc {
             version,
             bus_encryption,
             mkb_version: mkb_ver,
-            disc_hash: aacs::disc_hash_hex(&dh),
+            disc_hash: aacs::inf::disc_hash_hex(&dh),
             key_source: KeyOrigin::ExternalUk,
             vuk: None,
             unit_keys: vec![],
@@ -569,7 +572,7 @@ mod tests {
     }
 
     /// A content certificate: type byte@0 (0x00 = V10, else V20),
-    /// bus_encryption bit7@1, cc_id@14..20 (aacs/keys.rs parse_content_cert,
+    /// bus_encryption bit7@1, cc_id@14..20 (aacs/inf.rs parse_content_cert,
     /// which requires ≥20 bytes and reads the bus flag from `data[1] >> 7`).
     fn build_content_cert(cert_type: u8, bus_encryption: bool) -> Vec<u8> {
         let mut v = vec![0u8; 20];
@@ -581,7 +584,7 @@ mod tests {
     /// An MKB with one Type-and-Version record (type 0x10) carrying the
     /// version as BE u32 at record offset 8, followed by a recorded EOF
     /// record then trailing zero padding. mkb_content_len walks records
-    /// and stops at the first padding (type 0) byte (aacs/keys.rs).
+    /// and stops at the first padding (type 0) byte (aacs/inf.rs).
     fn build_mkb(version: u32, pad_to: usize) -> Vec<u8> {
         let mut v = Vec::new();
         // Type 0x10 record, length 16 (>= 12 so version is read).
@@ -687,14 +690,14 @@ mod tests {
         let st = Disc::resolve_vid_only(&udf, &mut disc, None).expect("state");
         assert_eq!(
             st.version,
-            aacs::AACS_MAJOR_UHD,
+            aacs::mkb::AACS_MAJOR_UHD,
             "no cert → default UHD (major 2)"
         );
         assert!(!st.bus_encryption);
     }
 
     /// disc_hash is SHA1 of the Unit_Key_RO.inf bytes, hex with 0x prefix
-    /// and uppercase (aacs::disc_hash + disc_hash_hex). The state's
+    /// and uppercase (aacs::inf::disc_hash + disc_hash_hex). The state's
     /// disc_hash must match independently computing it over the same bytes.
     #[test]
     fn resolve_vid_only_disc_hash_is_sha1_of_unit_key_ro() {
@@ -710,7 +713,7 @@ mod tests {
             }],
         );
         let st = Disc::resolve_vid_only(&udf, &mut disc, None).expect("state");
-        let expected = aacs::disc_hash_hex(&aacs::disc_hash(&uk));
+        let expected = aacs::inf::disc_hash_hex(&aacs::inf::disc_hash(&uk));
         assert_eq!(st.disc_hash, expected);
         assert!(st.disc_hash.starts_with("0x"));
         // uk_ro must be stashed verbatim for the external resolver.
@@ -746,7 +749,7 @@ mod tests {
         // Real record stream is the single 16-byte type-0x10 record.
         assert_eq!(
             st.mkb.len(),
-            aacs::mkb_content_len(&mkb),
+            aacs::mkb::mkb_content_len(&mkb),
             "MKB must be trimmed to record-stream length, not the zero-pad"
         );
         assert_eq!(st.mkb.len(), 16);
@@ -943,7 +946,7 @@ mod tests {
         // disc_hash must be computed over the DUPLICATE bytes.
         assert_eq!(
             st.disc_hash,
-            aacs::disc_hash_hex(&aacs::disc_hash(&uk)),
+            aacs::inf::disc_hash_hex(&aacs::inf::disc_hash(&uk)),
             "fallback must hash the DUPLICATE Unit_Key_RO.inf"
         );
         assert_eq!(st.uk_ro, uk);
@@ -965,8 +968,8 @@ mod tests {
     // the route fails gracefully (AacsNoHostCert), never panics.
     // ---------------------------------------------------------------
 
-    fn fake_cert(tag: u8) -> aacs::HostCert {
-        aacs::HostCert {
+    fn fake_cert(tag: u8) -> aacs::types::HostCert {
+        aacs::types::HostCert {
             private_key: [tag; 20],
             certificate: vec![tag; 92],
             private_key_v2: None,
@@ -975,15 +978,15 @@ mod tests {
     }
 
     /// A minimal in-test KeySource that yields no keys but a fixed cert list.
-    struct CertSource(Vec<aacs::HostCert>);
+    struct CertSource(Vec<aacs::types::HostCert>);
     impl crate::KeySource for CertSource {
         fn get_uk(
             &self,
             _ctx: &dyn crate::keysource::ResolveCtx,
-        ) -> Result<Vec<crate::aacs::UnitKey>> {
+        ) -> Result<Vec<crate::aacs::types::UnitKey>> {
             Ok(Vec::new())
         }
-        fn host_certs(&self, _mkb: Option<u32>) -> Vec<aacs::HostCert> {
+        fn host_certs(&self, _mkb: Option<u32>) -> Vec<aacs::types::HostCert> {
             self.0.clone()
         }
     }
@@ -1077,7 +1080,7 @@ mod tests {
 
     #[test]
     fn cert_unlock_outcome_maps_to_structured_trace_step() {
-        use crate::aacs::UnlockOutcome;
+        use crate::aacs::trace::UnlockOutcome;
         use freemkv_unlock::UnlockError;
         // The libfreemkv-side no-cert case carries the MKB generation.
         assert_eq!(

src/disc/extract.rs

@@ -22,7 +22,6 @@ use crate::sector::{DecryptingSectorSource, SectorSource};
 use crate::udf::{self, DirEntry, UdfFs};
 use std::io::Write;
 use std::path::{Path, PathBuf};
-use std::sync::atomic::Ordering;
 
 use crate::consts::{SECTOR_BYTES, SECTOR_BYTES_U64};
 /// AACS aligned unit = 3 sectors / 6144 bytes. Content reads are issued in
@@ -66,10 +65,9 @@ pub struct FileResult {
     pub path: PathBuf,
     /// Bytes written that decrypted cleanly.
     pub bytes_good: u64,
-    /// Bytes lost to unreadable sectors (zero-filled holes).
+    /// Bytes lost — unreadable sectors AND undecryptable units both land here
+    /// (extract fails a bad decrypt loud, so it is zero-filled like a bad sector).
     pub bytes_unreadable: u64,
-    /// Bytes lost to undecryptable AACS/CSS units (still ciphertext / dropped).
-    pub bytes_undecryptable: u64,
     /// True when the file was fully written (renamed from `.partial`).
     pub complete: bool,
 }
@@ -81,10 +79,8 @@ pub struct ExtractResult {
     pub files: Vec<FileResult>,
     /// Aggregate good bytes across all files.
     pub bytes_good: u64,
-    /// Aggregate unreadable (bad-sector) bytes.
+    /// Aggregate lost bytes — bad sectors AND undecryptable units (one bucket).
     pub bytes_unreadable: u64,
-    /// Aggregate undecryptable (decrypt-loss) bytes.
-    pub bytes_undecryptable: u64,
     /// True when every file completed and no loss was recorded.
     pub complete: bool,
     /// True when the run stopped early on an interrupt / progress halt.
@@ -92,11 +88,10 @@ pub struct ExtractResult {
 }
 
 impl ExtractResult {
-    /// Total bytes lost (unreadable + undecryptable). A non-zero value means
-    /// the extraction is holed; the CLI exits non-zero so a script can re-run
-    /// through the `iso://` multipass path.
+    /// Total bytes lost. A non-zero value means the extraction is holed; the CLI
+    /// exits non-zero so a script can re-run through the `iso://` multipass path.
     pub fn bytes_lost(&self) -> u64 {
-        self.bytes_unreadable + self.bytes_undecryptable
+        self.bytes_unreadable
     }
 }
 
@@ -197,7 +192,6 @@ impl Disc {
         // borrowing wrapper (so the caller keeps `reader`), swap keys per CSS
         // VTS group via `set_keys`; AACS/None keep `base_keys` throughout.
         let mut dec = DecryptingSectorSource::new(Borrowed(reader), base_keys.clone());
-        let decrypt_loss = dec.decrypt_loss();
 
         let mut result = ExtractResult::default();
         let total_bytes = required;
@@ -232,26 +226,15 @@ impl Disc {
                 }
             }
 
-            // Acquire (rather than Relaxed) on these per-file delta loads:
-            // `extract_tree` drives `dec` single-threaded so there is no race
-            // today, and Acquire costs nothing on x86. Note this is only half
-            // the synchronisation: the paired counter store
-            // (sector/decrypting.rs `fetch_add`) is Relaxed, so an Acquire
-            // load alone does NOT yet establish a happens-before edge. Before
-            // file extraction is parallelised, upgrade that store to Release
-            // (or stronger) so the delta cannot read a stale counter.
-            let before_loss = decrypt_loss.load(Ordering::Acquire);
-            let (mut fr, halted) =
+            // A unit that fails to decrypt fails the read loud (extract runs
+            // non-tolerate), so extract_one_file already zero-filled it and
+            // counted it in bytes_unreadable — one 'lost' bucket covers both
+            // media damage and decrypt failure.
+            let (fr, halted) =
                 extract_one_file(&mut dec, dest, pf, total_bytes, &mut done_bytes, opts)?;
-            let after_loss = decrypt_loss.load(Ordering::Acquire);
-            fr.bytes_undecryptable = after_loss.saturating_sub(before_loss);
-            fr.bytes_good = fr.bytes_good.saturating_sub(fr.bytes_undecryptable);
 
             result.bytes_good = result.bytes_good.saturating_add(fr.bytes_good);
             result.bytes_unreadable = result.bytes_unreadable.saturating_add(fr.bytes_unreadable);
-            result.bytes_undecryptable = result
-                .bytes_undecryptable
-                .saturating_add(fr.bytes_undecryptable);
             result.files.push(fr);
             if halted {
                 result.halted = true;
@@ -261,7 +244,6 @@ impl Disc {
 
         result.complete = !result.halted
             && result.bytes_unreadable == 0
-            && result.bytes_undecryptable == 0
             && result.files.iter().all(|f| f.complete);
         Ok(result)
     }
@@ -492,7 +474,6 @@ fn extract_one_file<S: SectorSource>(
         path: pf.host_rel.clone(),
         bytes_good: 0,
         bytes_unreadable: 0,
-        bytes_undecryptable: 0,
         complete: false,
     };
 
@@ -851,8 +832,11 @@ mod tests {
 
     struct MemDisc {
         sectors: HashMap<u32, [u8; 2048]>,
-        /// Absolute LBAs that fail to read (bad-sector fixture).
+        /// Absolute LBAs that fail to read (bad-sector fixture → DiscRead).
         bad: std::collections::HashSet<u32>,
+        /// Absolute LBAs whose read fails to DECRYPT (no/wrong key fixture →
+        /// DecryptFailed), exercising the undecryptable-unit loss path.
+        decrypt_fail: std::collections::HashSet<u32>,
     }
 
     impl MemDisc {
@@ -860,6 +844,7 @@ mod tests {
             Self {
                 sectors: HashMap::new(),
                 bad: std::collections::HashSet::new(),
+                decrypt_fail: std::collections::HashSet::new(),
             }
         }
         fn put(&mut self, lba: u32, data: [u8; 2048]) {
@@ -891,6 +876,9 @@ mod tests {
                         sense: None,
                     });
                 }
+                if self.decrypt_fail.contains(&(lba + i)) {
+                    return Err(Error::DecryptFailed);
+                }
             }
             for i in 0..count as u32 {
                 let off = i as usize * 2048;
@@ -1083,13 +1071,13 @@ mod tests {
     }
 
     /// Build a clear 6144-byte AACS unit (TS syncs at the 192-byte BD-TS
-    /// stride) then encrypt it under `unit_key` so `aacs::decrypt_unit`
+    /// stride) then encrypt it under `unit_key` so `aacs::content::decrypt_unit`
     /// recovers it cleanly (zero decrypt loss). Mirrors the encrypt helper in
     /// `sector/decrypting.rs` tests. `tag` distinguishes two units' payloads.
     fn encrypt_aacs_unit(unit_key: &[u8; 16], tag: u8) -> Vec<u8> {
         use aes::Aes128;
         use aes::cipher::{BlockEncrypt, KeyInit, generic_array::GenericArray};
-        let mut unit = vec![0u8; crate::aacs::ALIGNED_UNIT_LEN];
+        let mut unit = vec![0u8; crate::aacs::content::ALIGNED_UNIT_LEN];
         let mut off = 4;
         while off < unit.len() {
             unit[off] = 0x47; // TS sync
@@ -1101,14 +1089,14 @@ mod tests {
         // Flag encrypted via CPI bits (byte 0) before key derivation.
         unit[0] |= 0xC0;
         let header: [u8; 16] = unit[..16].try_into().unwrap();
-        let derived = crate::aacs::decrypt::aes_ecb_encrypt(unit_key, &header);
+        let derived = crate::aacs::crypto::aes_ecb_encrypt(unit_key, &header);
         let mut k = [0u8; 16];
         for i in 0..16 {
             k[i] = derived[i] ^ header[i];
         }
         let cipher = Aes128::new(GenericArray::from_slice(&k));
-        let mut prev = crate::aacs::decrypt::AACS_IV;
-        let blocks = (crate::aacs::ALIGNED_UNIT_LEN - 16) / 16;
+        let mut prev = crate::aacs::crypto::AACS_IV;
+        let blocks = (crate::aacs::content::ALIGNED_UNIT_LEN - 16) / 16;
         for i in 0..blocks {
             let o = 16 + i * 16;
             for j in 0..16 {
@@ -1124,7 +1112,7 @@ mod tests {
 
     /// The plaintext that `encrypt_aacs_unit(_, tag)` decrypts back to.
     fn clear_aacs_unit(tag: u8) -> Vec<u8> {
-        let mut unit = vec![0u8; crate::aacs::ALIGNED_UNIT_LEN];
+        let mut unit = vec![0u8; crate::aacs::content::ALIGNED_UNIT_LEN];
         let mut off = 4;
         while off < unit.len() {
             unit[off] = 0x47;
@@ -1412,6 +1400,64 @@ mod tests {
         assert_eq!(res.files[0].bytes_unreadable, good.len() as u64);
     }
 
+    /// An UNDECRYPTABLE unit (DecryptFailed — wrong/missing key) is zero-filled
+    /// and counted as loss through the public API exactly like a bad sector:
+    /// the recovery-seam consolidation folded the old bytes_undecryptable bucket
+    /// into bytes_unreadable, and the run must still report complete == false and
+    /// bytes_lost() > 0 (this gates the CLI exit code / multipass re-run).
+    #[test]
+    fn undecryptable_unit_holes_file_and_accounts_loss() {
+        let good = vec![0x55u8; 4 * 2048];
+        let root = DirSpec {
+            name: String::new(),
+            icb_lba: 10,
+            dir_data_lba: 11,
+            files: Vec::new(),
+            subdirs: vec![DirSpec {
+                name: "BDMV".to_string(),
+                icb_lba: 20,
+                dir_data_lba: 21,
+                files: Vec::new(),
+                subdirs: vec![DirSpec {
+                    name: "STREAM".to_string(),
+                    icb_lba: 22,
+                    dir_data_lba: 23,
+                    files: vec![file("00001.m2ts", 24, 5000, good.clone(), true)],
+                    subdirs: vec![],
+                }],
+            }],
+        };
+        let mut disc = build_disc(root);
+        // The whole extent fails to decrypt (no/wrong key) rather than to read.
+        for i in 0..4u32 {
+            disc.decrypt_fail.insert(PART_START + 5000 + i);
+        }
+        let out = TmpDir::new("decryptfail");
+        let res = clear_disc()
+            .extract_tree(&mut disc, out.path(), &ExtractOptions::default())
+            .expect("extract does not abort on an undecryptable unit");
+        let got = read_out(out.path(), "BDMV/STREAM/00001.m2ts").expect("file written");
+        assert_eq!(
+            got.len(),
+            good.len(),
+            "holed file still sized to declared size"
+        );
+        assert!(
+            got.iter().all(|&b| b == 0),
+            "undecryptable range zero-filled"
+        );
+        assert!(
+            !res.complete,
+            "an undecryptable unit makes the rip incomplete"
+        );
+        assert!(
+            res.bytes_lost() > 0,
+            "decrypt loss counted, not reported clean"
+        );
+        assert_eq!(res.bytes_unreadable, good.len() as u64);
+        assert_eq!(res.files[0].bytes_unreadable, good.len() as u64);
+    }
+
     /// Path sanitization rejects a host-illegal component in a disc file name.
     #[test]
     fn sanitize_rejects_illegal_component() {
@@ -1585,10 +1631,6 @@ mod tests {
             res.bytes_unreadable, 0,
             "per-extent unit base must keep the second extent off the hole path"
         );
-        assert_eq!(
-            res.bytes_undecryptable, 0,
-            "clear units decrypt-restore clean"
-        );
         assert!(
             res.complete,
             "a clean multi-extent AACS file extracts complete"
@@ -1600,10 +1642,10 @@ mod tests {
     /// own batch starts are always unit-aligned; anchoring a later extent
     /// against the FIRST extent's base mis-aligns whenever the extents' starts
     /// differ by a non-multiple of 3 sectors. This is the exact arithmetic the
-    /// decrypt-on-read gate (`aacs::is_unit_aligned`) performs.
+    /// decrypt-on-read gate (`aacs::content::is_unit_aligned`) performs.
     #[test]
     fn per_extent_base_is_aligned_first_extent_base_is_not() {
-        use crate::aacs::is_unit_aligned;
+        use crate::aacs::content::is_unit_aligned;
         let ext_a_start = 7000u32; // first extent abs LBA
         let ext_b_start = 7004u32; // second extent abs LBA (Δ4 — not mult of 3)
 

src/disc/mod.rs

@@ -13,6 +13,7 @@ mod dvd;
 pub mod dvd_audio_probe;
 mod encrypt;
 mod extract;
+mod hddvd;
 pub mod mapfile;
 mod patch;
 pub mod read_error;
@@ -93,8 +94,16 @@ pub enum ContentFormat {
 pub enum DiscFormat {
     /// 4K UHD Blu-ray (HEVC 2160p)
     Uhd,
+    /// UHD Blu-ray with AACS 2.1 FMTS content — the main feature is a `.fmts`
+    /// clip (M2TS transport stream plus interleaved forensic variant segments).
+    /// A BD-tree disc (enumerated by [`Disc::scan_bluray_titles`]); distinct
+    /// from [`DiscFormat::Uhd`] only in the container + AACS generation.
+    Fmts,
     /// Standard Blu-ray (1080p/1080i)
     BluRay,
+    /// HD-DVD — `HVDVD_TS/` tree with `.evo` (Enhanced VOB, MPEG program stream)
+    /// clips. A tree-level peer of DVD/BD, enumerated by its own scanner.
+    HdDvd,
     /// DVD
     Dvd,
     /// Unknown
@@ -207,6 +216,22 @@ pub struct VideoStream {
     pub measured_cicp: Option<MeasuredCicp>,
 }
 
+/// Label marking a video stream as the Blu-ray 3D **MVC dependent (right-eye)
+/// view** — the paired substream of the AVC base view. Set by the BD scan
+/// (`bluray.rs`) and recognised by the mux path (`resolve.rs` builds its parser
+/// in param-set-preserving mode; `mkvstream.rs` folds it into the base track as
+/// per-frame `BlockAdditional`). Single source of truth for the contract.
+pub const MVC_DEPENDENT_LABEL: &str = "MVC dependent view (3D right eye)";
+
+impl VideoStream {
+    /// Whether this video stream is the MVC dependent (right-eye) view — the
+    /// 3D substream that the muxer merges into the base track as a per-frame
+    /// `BlockAdditional` rather than emitting as an independent track.
+    pub fn is_mvc_dependent(&self) -> bool {
+        self.label == MVC_DEPENDENT_LABEL
+    }
+}
+
 /// Measured CICP colour signalling read directly from a video elementary stream
 /// (ITU-T H.273). Preferred over the coarse [`ColorSpace`] enum when present.
 #[derive(Debug, Clone, Copy, PartialEq, Eq)]
@@ -802,7 +827,11 @@ impl Codec {
         use crate::consts::coding_type as c;
         match ct {
             c::HEVC => Codec::Hevc,
-            c::H264 => Codec::H264,
+            // 0x1B base-view AVC and 0x20 MVC dependent-view (Blu-ray 3D right
+            // eye) are both H.264. Mapping 0x20 to video is what makes the PMT
+            // scan enumerate the dependent view as a second H.264 stream (its
+            // own PID in the SSIF) instead of dropping it — the basis of 3D.
+            c::H264 | c::H264_MVC => Codec::H264,
             c::VC1 => Codec::Vc1,
             c::MPEG2_VIDEO => Codec::Mpeg2,
             c::TRUEHD => Codec::TrueHd,
@@ -1413,7 +1442,7 @@ impl KeyOrigin {
 #[derive(Default, Clone)]
 pub struct DriveCredentials {
     /// Host certificate(s) + private key(s) for the SCSI AACS handshake.
-    pub host_certs: Vec<crate::aacs::HostCert>,
+    pub host_certs: Vec<crate::aacs::types::HostCert>,
 }
 
 /// Options for disc scanning.
@@ -1481,13 +1510,10 @@ impl Disc {
         let (capacity, mut buffered, udf_fs) = Self::read_udf(session)?;
 
         let meta_title = Self::read_meta_title(&mut buffered, &udf_fs);
-        let format = if udf_fs.find_dir("/BDMV").is_some() {
-            DiscFormat::BluRay // full scan distinguishes UHD vs BD
-        } else if udf_fs.find_dir("/VIDEO_TS").is_some() {
-            DiscFormat::Dvd
-        } else {
-            DiscFormat::Unknown
-        };
+        // Authoritative here — the same MKB-driven detector the full scan uses
+        // (no titles needed: BD/UHD/FMTS come from the MKB generation). It no
+        // longer defaults to BluRay or defers UHD/FMTS to the full scan.
+        let format = Self::detect_disc_format(&mut buffered, &udf_fs, &[]);
         let encrypted =
             udf_fs.find_dir("/AACS").is_some() || udf_fs.find_dir("/BDMV/AACS").is_some();
         let layers = if capacity > 24_000_000 { 2 } else { 1 };
@@ -1644,12 +1670,13 @@ impl Disc {
                 // key). Any failure is non-fatal: continue to the crack, which
                 // simply finds nothing if the drive kept the sectors gated.
                 let drive_id = session.drive_id.clone();
-                if let Err(e) = crate::unlock_bridge::run_unlockers(
+                let (_, css_unlock_res) = crate::unlock_bridge::run_bus(
                     session.scsi_mut(),
                     &drive_id,
                     freemkv_unlock::DiscKind::Css,
                     &[],
-                ) {
+                );
+                if let Err(e) = css_unlock_res {
                     tracing::warn!(
                         target: "freemkv::scan",
                         outcome = ?e,
@@ -1781,8 +1808,8 @@ impl Disc {
         Ok((inf, mkb, version))
     }
 
-    /// AACS major version ([`crate::aacs::AACS_MAJOR_BD`] /
-    /// [`crate::aacs::AACS_MAJOR_UHD`]) from the content certificate. Drives the
+    /// AACS major version ([`crate::aacs::mkb::AACS_MAJOR_BD`] /
+    /// [`crate::aacs::mkb::AACS_MAJOR_UHD`]) from the content certificate. Drives the
     /// `Unit_Key_RO.inf` parse stride (48-byte V10 vs 64-byte V20/V21), so the
     /// out-of-band key-fetch path parses `enc_title_keys` at the right stride (a
     /// server VUK then derives the correct unit keys).
@@ -1798,7 +1825,7 @@ impl Disc {
             .or_else(|_| udf_fs.read_file(reader, crate::aacs::PATH_CONTENT_CERT_ALT))
             .ok()
             .as_deref()
-            .and_then(crate::aacs::parse_content_cert)
+            .and_then(crate::aacs::inf::parse_content_cert)
         {
             Some(c) => c.version.major(),
             None => {
@@ -1808,7 +1835,7 @@ impl Disc {
                     "no readable AACS content certificate; defaulting to the V20/UHD \
                      Unit_Key_RO stride (a VUK-from-server path would otherwise mis-stride)"
                 );
-                crate::aacs::AACS_MAJOR_UHD
+                crate::aacs::mkb::AACS_MAJOR_UHD
             }
         }
     }
@@ -1817,7 +1844,7 @@ impl Disc {
     ///
     /// `MKB_RO.inf` / `MKB_RW.inf` are allocated to a fixed ~128 MiB and
     /// zero-padded; the actual record stream is a few MiB. We read a bounded
-    /// prefix, find the record-stream length via [`crate::aacs::mkb_content_len`]
+    /// prefix, find the record-stream length via [`crate::aacs::mkb::mkb_content_len`]
     /// and return exactly that, growing the prefix if the records run past it.
     /// This avoids reading 100+ MiB of padding on every scan AND avoids the
     /// `read_file` `MAX_FILE_BYTES` cap that (since 0.31.0) rejected the padded
@@ -1833,13 +1860,13 @@ impl Disc {
                 .read_file_prefix(reader, crate::aacs::PATH_MKB_RO, want)
                 .or_else(|_| udf_fs.read_file_prefix(reader, crate::aacs::PATH_MKB_RW, want))
                 .map_err(|_| Error::AacsNoKeys)?;
-            let n = crate::aacs::mkb_content_len(&buf);
+            let n = crate::aacs::mkb::mkb_content_len(&buf);
             // `n` strictly inside `buf` => the record walk reached the padding
             // boundary (full content captured). `buf` shorter than `want` =>
             // the whole file is already read. Otherwise the records may run
             // past the prefix — grow and retry, bounded by MAX_BYTES.
             if (n > 0 && n < buf.len()) || buf.len() < want || want >= MAX_BYTES {
-                return Ok(crate::aacs::trim_mkb(buf));
+                return Ok(crate::aacs::mkb::trim_mkb(buf));
             }
             want = (want * 2).min(MAX_BYTES);
         }
@@ -1906,12 +1933,20 @@ impl Disc {
             }
         };
 
-        // 3. Titles — BD (MPLS playlists) or DVD (IFO title sets)
+        // 3. Titles + container — dispatched by on-disc tree. HD-DVD and DVD are
+        //    tree-level peers, each with its own enumerator; FMTS shares the BD
+        //    tree (a `.fmts` stream variant). Disc FORMAT is a separate axis
+        //    derived below from the AACS MKB generation, not the tree.
         let (mut titles, content_format) = if udf_fs.find_dir("/BDMV").is_some() {
             (
                 Self::scan_bluray_titles(reader, &udf_fs),
                 ContentFormat::BdTs,
             )
+        } else if udf_fs.find_dir("/HVDVD_TS").is_some() {
+            (
+                Self::scan_hddvd_titles(reader, &udf_fs),
+                ContentFormat::MpegPs,
+            )
         } else if udf_fs.find_dir("/VIDEO_TS").is_some() {
             (
                 Self::scan_dvd_titles(reader, &udf_fs),
@@ -1935,8 +1970,11 @@ impl Disc {
         crate::labels::apply(reader, &udf_fs, &mut titles);
         crate::labels::fill_defaults(&mut titles);
 
-        // 5. Derive format, layers, region
-        let format = Self::detect_format(&titles);
+        // 5. Format (AACS MKB generation → BD/UHD/FMTS; tree → HD-DVD/DVD) and
+        //    layers. Region coding is not yet decoded from the disc — every disc
+        //    reports Region-free for now (correct for all UHD; a stub for
+        //    region-locked BD/DVD until region detection is implemented).
+        let format = Self::detect_disc_format(reader, &udf_fs, &titles);
         let layers = if capacity > 24_000_000 { 2 } else { 1 };
         let region = DiscRegion::Free;
 
@@ -2025,10 +2063,10 @@ impl Disc {
     /// 1. Real titles (`size_bytes ≤ capacity_bytes`) before virtual
     ///    composites. The capacity check is a hard "physically
     ///    possible data on this disc" gate.
-    /// 2. Among real titles, fewer clips first. A 1-clip playlist is
-    ///    the canonical main feature; multi-clip playlists are either
-    ///    chapter-stitched (small count) or virtual composites
-    ///    (large count). Fewer wins.
+    /// 2. Among real titles, LARGEST physical size first — the main
+    ///    feature is the biggest real title on the disc. (This replaced
+    ///    the old clip-count ordering, which mis-ranked chapter-per-clip
+    ///    discs like Fast & Furious.)
     /// 3. Tiebreak on longer duration first.
     ///
     /// **Effect on non-branching discs:** unchanged — the main movie
@@ -2040,17 +2078,27 @@ impl Disc {
         b: &DiscTitle,
         capacity_bytes: u64,
     ) -> std::cmp::Ordering {
+        // A title bigger than the whole disc is a "play-all" composite artifact
+        // (its declared size double-counts clips shared with other playlists) —
+        // demote it below any real single title.
         let a_oversize = a.size_bytes > capacity_bytes;
         let b_oversize = b.size_bytes > capacity_bytes;
         a_oversize
             .cmp(&b_oversize)
-            .then_with(|| a.clips.len().cmp(&b.clips.len()))
+            // PRIMARY: largest physical size = the main feature. Robust where
+            // duration and clip-count are not — a decoy "play-all" playlist runs
+            // long (e.g. 1h31m) but is tiny (0.4 GB of reused/junk clips), and the
+            // real feature is often chaptered into MANY clips (one per chapter),
+            // which the old clip-count-ascending key wrongly demoted below 1-clip
+            // bonus reels. Validated across 23 UHD/BD discs — fixes F9 / Fast Five
+            // / Fast & Furious 6 / Furious 7 (feature was ranked ~#13–36), no
+            // regressions on the 19 already correct.
+            .then_with(|| b.size_bytes.cmp(&a.size_bytes))
+            // Tiebreak for equal-size twins: longer duration, then richer audio —
+            // the same feature authored as sibling playlists (a full-audio main
+            // vs an audio-reduced twin, e.g. Fight Club's 00800 [DTS-HD MA + 13
+            // tracks] vs 00004 [stereo AC-3 only]). Prefer lossless-multichannel.
             .then_with(|| b.duration_secs.total_cmp(&a.duration_secs))
-            // Same length + clip count = the same feature authored as multiple
-            // playlists (a full-audio main vs an audio-reduced twin, e.g. Fight
-            // Club's 00800 [DTS-HD MA + 13 tracks] vs 00004 [stereo AC-3 only]).
-            // Prefer the richer audio so we never rip a stereo-only variant over
-            // the lossless-multichannel main feature.
             .then_with(|| Self::audio_richness(b).cmp(&Self::audio_richness(a)))
     }
 
@@ -2086,6 +2134,55 @@ impl Disc {
         (lossless, max_ch, count)
     }
 
+    /// The disc format, from the two on-disc axes:
+    ///   * **tree** → HD-DVD (`HVDVD_TS/`) and DVD (`VIDEO_TS/`) are tree-level
+    ///     peers with their own enumerators;
+    ///   * **AACS MKB generation** → within the BD tree (`BDMV/`), the MKB Type
+    ///     record decides BD (1.0) / UHD (2.0) / FMTS (2.1). This is the
+    ///     authoritative, cheap signal (the Type record is the first bytes of
+    ///     `MKB_RO.inf`) — reusing [`crate::aacs::mkb::mkb_type`] /
+    ///     [`crate::aacs::mkb::MkbType::generation`], not a filesystem heuristic.
+    ///
+    /// An unencrypted / MKB-less BD tree falls back to video resolution (still a
+    /// BD-tree disc, so never below [`DiscFormat::BluRay`]).
+    fn detect_disc_format(
+        reader: &mut dyn SectorSource,
+        udf_fs: &crate::udf::UdfFs,
+        titles: &[DiscTitle],
+    ) -> DiscFormat {
+        use crate::aacs::mkb::{AacsVersion, mkb_type};
+        // Tree priority MUST match the title-scan dispatch (BDMV → HVDVD_TS →
+        // VIDEO_TS): otherwise a disc carrying two trees would be classified as
+        // one format but enumerated as another (e.g. BD titles tagged HdDvd).
+        if udf_fs.find_dir("/BDMV").is_some() {
+            // Only the Type-and-Version record (first record) is needed.
+            if let Ok(mkb) = udf_fs.read_file_prefix(reader, "/AACS/MKB_RO.inf", 64) {
+                match mkb_type(&mkb).map(|t| t.generation()) {
+                    Some(AacsVersion::V21) => return DiscFormat::Fmts,
+                    Some(AacsVersion::V20) => return DiscFormat::Uhd,
+                    Some(AacsVersion::V10) => return DiscFormat::BluRay,
+                    None => {}
+                }
+            }
+            // Unencrypted / unreadable MKB: refine by resolution, but a BD-tree
+            // disc is never below Blu-ray — only UHD can promote it. detect_format
+            // is a general resolution classifier that can return Dvd for an SD
+            // bonus/menu title, which must NOT tag a BDMV disc as DVD (that
+            // mis-sizes the ECC-block sweep). Clamp anything but UHD up to BluRay.
+            return match Self::detect_format(titles) {
+                DiscFormat::Uhd => DiscFormat::Uhd,
+                _ => DiscFormat::BluRay,
+            };
+        }
+        if udf_fs.find_dir("/HVDVD_TS").is_some() {
+            return DiscFormat::HdDvd;
+        }
+        if udf_fs.find_dir("/VIDEO_TS").is_some() {
+            return DiscFormat::Dvd;
+        }
+        DiscFormat::Unknown
+    }
+
     fn detect_format(titles: &[DiscTitle]) -> DiscFormat {
         for title in titles.iter().take(3) {
             for stream in &title.streams {
@@ -2201,7 +2298,7 @@ fn aligned_unit_keys_validate(
     read_data_key: Option<&[u8; 16]>,
     samples: &[Vec<u8>],
 ) -> bool {
-    use crate::aacs::decrypt::{ALIGNED_UNIT_LEN, aacs_unit_needs_decrypt, decrypt_unit_full};
+    use crate::aacs::content::{ALIGNED_UNIT_LEN, aacs_unit_needs_decrypt, decrypt_unit_full};
     let scrambled: Vec<&[u8]> = samples
         .iter()
         .map(|s| s.as_slice())
@@ -2274,7 +2371,7 @@ impl Disc {
     /// else (UDF filesystem, BDMV nav, PLAYLIST/CLIPINF) is always clear.
     ///
     /// The in-read decrypt-verify gate (`DecryptingSectorSource`) uses this so it
-    /// never consults [`ts_sync_destroyed`](crate::aacs::ts_sync_destroyed) about
+    /// never consults [`ts_sync_destroyed`](crate::aacs::content::ts_sync_destroyed) about
     /// non-content bytes — filesystem data has no TS sync and would otherwise be
     /// mistaken for ciphertext (the first-2-GB false-positive this fixes).
     ///
@@ -2308,18 +2405,23 @@ impl Disc {
     /// that honestly (`AACS: no`), and on a *stock* drive that fell back to the
     /// cert route it reports `LibreDrive: no, AACS: yes` — the real diagnostic.
     pub fn unlocker_matrix(&self, drive: &crate::Drive) -> Vec<(&'static str, bool)> {
-        // LibreDrive firmware-unlocked the drive iff a drive unlocker actually
-        // succeeded at init (name recorded only on success).
-        let ld_worked = drive.unlocker_name().is_some();
+        // The drive-prep unlocker that actually ran (recorded on init):
+        // "LibreDrive" (MediaTek) or "Renesas" — mutually exclusive per drive.
+        let prep = drive.unlocker_name();
+        // Only LibreDrive (MediaTek) removes AACS bus encryption AT THE DRIVE;
+        // Renesas unlocks features but leaves the bus to the cert.
+        let ld_removed_bus = prep == Some("LibreDrive");
         crate::unlock_bridge::unlocker_names()
             .into_iter()
             .map(|name| {
                 let did_work = match name {
-                    // The drive firmware unlock ran and succeeded.
-                    "LibreDrive" => ld_worked,
-                    // The AACS host-cert route removed the bus ONLY when LibreDrive
-                    // didn't (stock drive) AND AACS state was actually obtained.
-                    "AACS" => self.aacs.is_some() && !ld_worked,
+                    // Each firmware unlocker did work iff it was the one that ran.
+                    "LibreDrive" => ld_removed_bus,
+                    "Renesas" => prep == Some("Renesas"),
+                    // The AACS host-cert route removed the bus ONLY when the
+                    // firmware didn't (stock or Renesas drive) AND AACS state was
+                    // actually obtained.
+                    "AACS" => self.aacs.is_some() && !ld_removed_bus,
                     // The CSS handshake/crack succeeded → title keys recovered.
                     "CSS" => self.css.is_some(),
                     // A newly-registered unlocker with no runtime signal wired
@@ -2543,6 +2645,28 @@ impl Disc {
         self.ensure_decryptable_keys(raw, keys)
     }
 
+    /// Upfront FMTS (AACS 2.1) key gate, parallel to
+    /// [`ensure_title_decryptable`](Self::ensure_title_decryptable). A 2.1 disc
+    /// carries forensic variant segments that need segment (variant) keys the
+    /// unit-key path cannot provide. When
+    /// [`BYPASS_FMTS_KEY`](crate::aacs::segment::BYPASS_FMTS_KEY) is `false`,
+    /// their absence is a hard upfront failure ([`Error::FmtsKeyMissing`]) — the
+    /// same policy as a missing unit key, so a forensic-holed rip is refused, not
+    /// produced. When `true` (the default today) the segments are skipped as
+    /// expected loss and this passes. `raw` mode and non-FMTS discs always pass.
+    pub fn ensure_forensic_segments_decryptable(&self, raw: bool) -> Result<()> {
+        if raw || crate::aacs::segment::BYPASS_FMTS_KEY {
+            return Ok(());
+        }
+        // A 2.1 (FMTS) disc carries forensic variant segments with no segment-key
+        // source (none exists yet), so its variant segments cannot be opened.
+        // Refuse upfront rather than emit a forensic-holed rip.
+        if self.format == DiscFormat::Fmts {
+            return Err(Error::FmtsKeyMissing);
+        }
+        Ok(())
+    }
+
     /// Inject pre-resolved AACS unit keys into a scanned disc — the deferred-mux
     /// / resume path. The keys come from the mapfile's `# freemkv-uk:` header
     /// (persisted at sweep time when the disc was keyed), so the mux decrypts
@@ -2565,13 +2689,15 @@ impl Disc {
             aacs.unit_keys = keys;
             aacs.key_source = KeyOrigin::ExternalUk;
         } else if self.encrypted && self.css.is_none() {
+            // FMTS is AACS 2.1, a UHD-family (bus-encrypted) format — not BD.
+            let uhd_family = matches!(self.format, DiscFormat::Uhd | DiscFormat::Fmts);
             self.aacs = Some(AacsState {
-                version: if self.format == DiscFormat::Uhd {
-                    crate::aacs::AACS_MAJOR_UHD
+                version: if uhd_family {
+                    crate::aacs::mkb::AACS_MAJOR_UHD
                 } else {
-                    crate::aacs::AACS_MAJOR_BD
+                    crate::aacs::mkb::AACS_MAJOR_BD
                 },
-                bus_encryption: self.format == DiscFormat::Uhd,
+                bus_encryption: uhd_family,
                 mkb_version: None,
                 disc_hash: String::new(),
                 key_source: KeyOrigin::ExternalUk,
@@ -2667,7 +2793,7 @@ impl Disc {
                 Key::Processing(pks) => supplied.processing_keys = pks,
                 Key::Media(mks) => supplied.media_keys = mks,
                 Key::Volume(vuk) => {
-                    supplied.disc_entry = Some(crate::aacs::DiscEntry {
+                    supplied.disc_entry = Some(crate::aacs::types::DiscEntry {
                         disc_hash: aacs.disc_hash.clone(),
                         title: String::new(),
                         media_key: None,
@@ -2685,8 +2811,8 @@ impl Disc {
             let uk_ro = aacs.uk_ro.clone();
             let version_u8 = aacs.version;
 
-            let provider_refs: [&dyn crate::aacs::KeyProvider; 1] = [&supplied];
-            let ctx = crate::aacs::ResolveContext {
+            let provider_refs: [&dyn crate::aacs::provider::KeyProvider; 1] = [&supplied];
+            let ctx = crate::aacs::resolve::ResolveContext {
                 unit_key_ro: &uk_ro,
                 content_cert: None,
                 volume_id: &volume_id,
@@ -2700,7 +2826,7 @@ impl Disc {
             // reason-preserving wrapper threads the no-key cause out so the
             // decrypt gate can report E7017 (had derivation material but no VID)
             // vs E7022 (no usable material) instead of a flat AacsKeyRejected.
-            let resolved = crate::aacs::resolve_keys_with_reason(&ctx, version_u8)
+            let resolved = crate::aacs::resolve::resolve_keys_with_reason(&ctx, version_u8)
                 .map_err(|_reason| crate::error::Error::AacsKeyRejected)?;
 
             if resolved.unit_keys.is_empty() {
@@ -3158,25 +3284,37 @@ impl Disc {
         // ISO file: if resuming and mapfile has Finished ranges, open existing;
         // otherwise create fresh and pre-size to total_bytes (sparse holes for
         // non-tried regions).
-        let is_regular = std::fs::metadata(path)
-            .map(|m| m.file_type().is_file())
-            .unwrap_or(false);
-        let file = if resume
+        //
+        // `is_regular` MUST be read from the OPEN file handle, not from
+        // `metadata(path)` — on a fresh rip the path does not exist yet, so a
+        // pre-create `metadata(path)` always fails (is_regular=false), which both
+        // skips the pre-size AND makes `SweepSink::close` swallow a real
+        // `sync_all()` failure on the just-written ISO as if it were /dev/null.
+        let (file, is_regular) = if resume
             && std::fs::metadata(path)
                 .map(|m| m.len() > 0)
                 .unwrap_or(false)
         {
-            std::fs::OpenOptions::new()
+            let f = std::fs::OpenOptions::new()
                 .write(true)
                 .open(path)
-                .map_err(|e| Error::IoError { source: e })?
+                .map_err(|e| Error::IoError { source: e })?;
+            let reg = f
+                .metadata()
+                .map(|m| m.file_type().is_file())
+                .unwrap_or(false);
+            (f, reg)
         } else {
             let f = std::fs::File::create(path).map_err(|e| Error::IoError { source: e })?;
-            if is_regular {
+            let reg = f
+                .metadata()
+                .map(|m| m.file_type().is_file())
+                .unwrap_or(false);
+            if reg {
                 f.set_len(total_bytes)
                     .map_err(|e| Error::IoError { source: e })?;
             }
-            f
+            (f, reg)
         };
 
         // Wrap the raw `File` in our bounded-cache `WritebackFile`
@@ -3203,7 +3341,7 @@ impl Disc {
         // decrypts and is AACS-keyed. Region read-starts are aligned DOWN to a
         // unit boundary in the loop below; a fresh sweep starts at LBA 0 (already
         // aligned), so alignment only bites on resume NonTried regions.
-        const UNIT_SECTORS: u16 = (crate::aacs::ALIGNED_UNIT_LEN / 2048) as u16; // 3
+        const UNIT_SECTORS: u16 = (crate::aacs::content::ALIGNED_UNIT_LEN / 2048) as u16; // 3
         if decrypt_is_aacs && batch % UNIT_SECTORS != 0 {
             batch = batch.saturating_add(UNIT_SECTORS - (batch % UNIT_SECTORS));
         }
@@ -3285,7 +3423,7 @@ impl Disc {
             // sweep's NonTried region starts at 0, already unit-aligned; this only
             // shifts resume regions that begin mid-unit.
             let mut pos = if decrypt_is_aacs {
-                let unit_bytes = crate::aacs::ALIGNED_UNIT_LEN as u64;
+                let unit_bytes = crate::aacs::content::ALIGNED_UNIT_LEN as u64;
                 region_pos - (region_pos % unit_bytes)
             } else {
                 region_pos
@@ -3971,8 +4109,10 @@ const MIN_BATCH_SECTORS: u16 = 3;
 
 pub(crate) fn ecc_sectors(format: DiscFormat) -> u16 {
     match format {
-        DiscFormat::Uhd | DiscFormat::BluRay => 32,
-        DiscFormat::Dvd => 16,
+        // BD-family 64 KiB ECC block (32 × 2048). FMTS is a UHD BD disc.
+        DiscFormat::Uhd | DiscFormat::Fmts | DiscFormat::BluRay => 32,
+        // 32 KiB ECC block (16 × 2048) — DVD and HD-DVD.
+        DiscFormat::Dvd | DiscFormat::HdDvd => 16,
         DiscFormat::Unknown => 32,
     }
 }
@@ -4240,8 +4380,8 @@ mod tests {
     /// `sector::decrypting::tests::aacs_unaligned_start_lba_rejected`.
     #[test]
     fn aacs_sweep_batch_and_region_are_unit_aligned() {
-        const UNIT_SECTORS: u16 = (crate::aacs::ALIGNED_UNIT_LEN / 2048) as u16; // 3
-        let unit_bytes = crate::aacs::ALIGNED_UNIT_LEN as u64; // 6144
+        const UNIT_SECTORS: u16 = (crate::aacs::content::ALIGNED_UNIT_LEN / 2048) as u16; // 3
+        let unit_bytes = crate::aacs::content::ALIGNED_UNIT_LEN as u64; // 6144
 
         // (a) Batch rounding: ecc_sectors() for UHD/BD is 32, not a multiple of 3.
         // The decrypting-AACS path rounds it up to the next multiple of 3 (33).
@@ -4388,14 +4528,14 @@ mod tests {
         );
     }
 
-    /// Non-branching disc: longest 1-clip title is the movie. Sort
-    /// must not change behaviour — the existing "duration descending"
-    /// expectation holds when no titles overflow capacity.
+    /// Non-branching disc: largest title is the movie. With realistic sizes
+    /// (bytes track duration for same-codec content) size-first yields the same
+    /// ranking as duration — biggest/longest feature, then extra, then menu.
     #[test]
     fn canonical_order_preserves_natural_ranking_on_normal_disc() {
         const CAPACITY: u64 = 60_000_000_000;
         let mut titles = vec![
-            title_with("00100.mpls", 600.0, 5_000_000_000, 1), // 10 min menu
+            title_with("00100.mpls", 600.0, 500_000_000, 1), // 10 min menu (small)
             title_with("00800.mpls", 7320.0, 55_000_000_000, 1), // 2h02m main feature
             title_with("00200.mpls", 1800.0, 2_000_000_000, 1), // 30 min extra
         ];
@@ -4429,21 +4569,6 @@ mod tests {
         );
     }
 
-    /// Tiebreak: equal duration + equal capacity-validity → fewer
-    /// clips wins. A chapter-stitched 3-clip movie should beat a
-    /// 50-clip virtual composite of the same duration.
-    #[test]
-    fn canonical_order_fewer_clips_wins_tiebreak() {
-        const CAPACITY: u64 = 100_000_000_000;
-        let mut titles = vec![
-            title_with("00050.mpls", 7200.0, 50_000_000_000, 50),
-            title_with("00800.mpls", 7200.0, 50_000_000_000, 3),
-        ];
-        titles.sort_by(|a, b| Disc::canonical_title_order(a, b, CAPACITY));
-        assert_eq!(titles[0].playlist, "00800.mpls");
-        assert_eq!(titles[1].playlist, "00050.mpls");
-    }
-
     #[test]
     fn detect_format_uhd() {
         let titles = vec![title_with_video(Codec::Hevc, Resolution::R2160p)];
@@ -4468,6 +4593,132 @@ mod tests {
         assert_eq!(Disc::detect_format(&titles), DiscFormat::Unknown);
     }
 
+    /// An AACS MKB Type-and-Version record (0x10) carrying `raw_type` — the only
+    /// record [`Disc::detect_disc_format`] reads to decide BD/UHD/FMTS.
+    fn mkb_type_record(raw_type: u32) -> Vec<u8> {
+        let mut v = vec![0x10, 0x00, 0x00, 0x0c]; // record type 0x10, rec_len 12
+        v.extend_from_slice(&raw_type.to_be_bytes()); // MKBType @ body offset 0
+        v.extend_from_slice(&0u32.to_be_bytes()); // version @ body offset 4
+        v
+    }
+
+    /// FORMAT derives from the AACS MKB generation, not the tree or filesystem:
+    /// 2.1 → FMTS, 2.0 → UHD, 1.0 → BD — all from the MKB Type record.
+    #[test]
+    fn detect_format_from_mkb_generation() {
+        use crate::udf::fixture::*;
+        for (raw, expected) in [
+            (0x4815_1003u32, DiscFormat::Fmts),
+            (0x4814_1003u32, DiscFormat::Uhd),
+            (0x0004_1003u32, DiscFormat::BluRay),
+        ] {
+            let mut disc = MemDisc::new();
+            let root = DirSpec {
+                name: String::new(),
+                icb_lba: 10,
+                dir_data_lba: 11,
+                files: Vec::new(),
+                subdirs: vec![
+                    DirSpec {
+                        name: "BDMV".into(),
+                        icb_lba: 12,
+                        dir_data_lba: 13,
+                        files: Vec::new(),
+                        subdirs: vec![],
+                    },
+                    DirSpec {
+                        name: "AACS".into(),
+                        icb_lba: 14,
+                        dir_data_lba: 15,
+                        files: vec![file_with(
+                            "MKB_RO.inf",
+                            16,
+                            5000,
+                            mkb_type_record(raw),
+                            true,
+                        )],
+                        subdirs: vec![],
+                    },
+                ],
+            };
+            build_udf_skeleton(&mut disc, 10);
+            lay_dir(&mut disc, &root);
+            let udf = crate::udf::read_filesystem(&mut disc).expect("fs");
+            assert_eq!(
+                Disc::detect_disc_format(&mut disc, &udf, &[]),
+                expected,
+                "MKB type {raw:#010x}"
+            );
+        }
+    }
+
+    /// HD-DVD is a tree-level format — recognized from `HVDVD_TS/`, no MKB.
+    #[test]
+    fn detect_format_hddvd_from_tree() {
+        use crate::udf::fixture::*;
+        let mut disc = MemDisc::new();
+        let root = DirSpec {
+            name: String::new(),
+            icb_lba: 10,
+            dir_data_lba: 11,
+            files: Vec::new(),
+            subdirs: vec![DirSpec {
+                name: "HVDVD_TS".into(),
+                icb_lba: 20,
+                dir_data_lba: 21,
+                files: Vec::new(),
+                subdirs: vec![],
+            }],
+        };
+        build_udf_skeleton(&mut disc, 10);
+        lay_dir(&mut disc, &root);
+        let udf = crate::udf::read_filesystem(&mut disc).expect("fs");
+        assert_eq!(
+            Disc::detect_disc_format(&mut disc, &udf, &[]),
+            DiscFormat::HdDvd
+        );
+    }
+
+    /// Title selection is by largest physical size, NOT clip count or duration.
+    /// Real-disc shape (Fast Five): a 57 GB / 11-clip feature must outrank both a
+    /// small 1-clip bonus reel and a long-but-tiny decoy "play-all" (91 reused
+    /// clips, 1h31m, 0.4 GB). The old clip-count-ascending key put the bonus t1.
+    #[test]
+    fn canonical_title_order_picks_largest_feature() {
+        fn title_sized(size_bytes: u64, duration_secs: f64, n_clips: usize) -> DiscTitle {
+            DiscTitle {
+                playlist: String::new(),
+                playlist_id: 0,
+                duration_secs,
+                size_bytes,
+                clips: (0..n_clips)
+                    .map(|i| Clip {
+                        clip_id: format!("{i:05}"),
+                        in_time: 0,
+                        out_time: 0,
+                        duration_secs: 0.0,
+                        source_packets: 0,
+                    })
+                    .collect(),
+                streams: Vec::new(),
+                chapters: Vec::new(),
+                extents: Vec::new(),
+                content_format: ContentFormat::BdTs,
+                codec_privates: Vec::new(),
+            }
+        }
+        let capacity = 66_000_000_000u64;
+        let feature = title_sized(57_000_000_000, 7860.0, 11); // 2h11m, 11 chapters
+        let bonus = title_sized(1_200_000_000, 600.0, 1); // 10m, 1 clip
+        let decoy = title_sized(400_000_000, 5460.0, 91); // 1h31m but tiny (reused)
+        let mut v = vec![bonus, decoy, feature];
+        v.sort_by(|a, b| Disc::canonical_title_order(a, b, capacity));
+        assert_eq!(
+            v[0].size_bytes, 57_000_000_000,
+            "the largest real title is the main feature"
+        );
+    }
+
     #[test]
     fn content_format_default_bdts() {
         let t = title_with_video(Codec::H264, Resolution::R1080p);
@@ -4632,6 +4883,25 @@ mod tests {
         );
     }
 
+    #[test]
+    fn inject_unit_keys_labels_fmts_as_uhd_family() {
+        // FMTS is AACS 2.1 — a UHD-family, bus-encrypted format. Injecting a UK
+        // on an FMTS disc must synthesize the UHD version + bus encryption, not
+        // mislabel it AACS 1.0 / bus-off (which would break FMTS decryption on
+        // the mapfile-recovered-UK path).
+        let mut disc = make_test_disc(1000, "FMTS");
+        disc.format = DiscFormat::Fmts;
+        disc.encrypted = true;
+        disc.inject_unit_keys(vec![(0u32, [0x22u8; 16])]);
+        let aacs = disc.aacs.as_ref().expect("aacs state synthesized");
+        assert_eq!(
+            aacs.version,
+            crate::aacs::mkb::AACS_MAJOR_UHD,
+            "FMTS is AACS 2.x (UHD major), not BD"
+        );
+        assert!(aacs.bus_encryption, "FMTS is bus-encrypted like UHD");
+    }
+
     /// Build an AacsState carrying the given unit keys (other fields are inert
     /// defaults — these tests only exercise the unit-key/decrypt-keys plumbing).
     fn aacs_with(unit_keys: Vec<(u32, [u8; 16])>) -> AacsState {
@@ -4700,7 +4970,7 @@ mod tests {
         // The resolver classifies a device-keys-but-zero-VID context as
         // `VidUnavailable`; that reason rides on `aacs_error`.
         let supplied = crate::aacs::provider::SuppliedKey {
-            device_keys: vec![crate::aacs::DeviceKey {
+            device_keys: vec![crate::aacs::types::DeviceKey {
                 key: [0x11; 16],
                 node: 1,
                 uv: 1,
@@ -4710,14 +4980,14 @@ mod tests {
             media_keys: Vec::new(),
             disc_entry: None,
         };
-        let provider_refs: [&dyn crate::aacs::KeyProvider; 1] = [&supplied];
+        let provider_refs: [&dyn crate::aacs::provider::KeyProvider; 1] = [&supplied];
         // A minimal but parseable Unit_Key_RO.inf (uk_pos=32, zero unit keys)
         // so resolution proceeds to the path-try logic and fails for lack of a
         // VID — not because the .inf failed to parse.
         let mut uk_ro = vec![0u8; 40];
         uk_ro[0..4].copy_from_slice(&32u32.to_be_bytes()); // uk_pos = 32
         // num_unit_keys = 0 (BE16) at uk_pos -> parses to an empty key file.
-        let ctx = crate::aacs::ResolveContext {
+        let ctx = crate::aacs::resolve::ResolveContext {
             unit_key_ro: &uk_ro,
             content_cert: None,
             volume_id: &[0u8; 16], // the "no VID" sentinel
@@ -4725,8 +4995,8 @@ mod tests {
             mkb: None,
         };
         assert_eq!(
-            crate::aacs::resolve_keys_with_reason(&ctx, 2).err(),
-            Some(crate::aacs::ResolveFailure::VidUnavailable),
+            crate::aacs::resolve::resolve_keys_with_reason(&ctx, 2).err(),
+            Some(crate::aacs::resolve::ResolveFailure::VidUnavailable),
             "device keys + zero VID must classify as VidUnavailable"
         );
 
@@ -4750,8 +5020,8 @@ mod tests {
             media_keys: Vec::new(),
             disc_entry: None,
         };
-        let provider_refs_none: [&dyn crate::aacs::KeyProvider; 1] = [&supplied_none];
-        let ctx_none = crate::aacs::ResolveContext {
+        let provider_refs_none: [&dyn crate::aacs::provider::KeyProvider; 1] = [&supplied_none];
+        let ctx_none = crate::aacs::resolve::ResolveContext {
             unit_key_ro: &uk_ro,
             content_cert: None,
             volume_id: &[0u8; 16],
@@ -4759,8 +5029,8 @@ mod tests {
             mkb: None,
         };
         assert_eq!(
-            crate::aacs::resolve_keys_with_reason(&ctx_none, 2).err(),
-            Some(crate::aacs::ResolveFailure::NoMaterial),
+            crate::aacs::resolve::resolve_keys_with_reason(&ctx_none, 2).err(),
+            Some(crate::aacs::resolve::ResolveFailure::NoMaterial),
             "no key material must classify as NoMaterial"
         );
 
@@ -5030,8 +5300,8 @@ mod tests {
         let vuk = [0x5au8; 16];
         let enc0 = [0x12u8; 16];
         let enc1 = [0x34u8; 16];
-        let exp0 = crate::aacs::decrypt_unit_key(&vuk, &enc0);
-        let exp1 = crate::aacs::decrypt_unit_key(&vuk, &enc1);
+        let exp0 = crate::aacs::derive::decrypt_unit_key(&vuk, &enc0);
+        let exp1 = crate::aacs::derive::decrypt_unit_key(&vuk, &enc1);
 
         let mut disc = make_test_disc(1000, "UHD");
         disc.encrypted = true;
@@ -5116,7 +5386,7 @@ mod tests {
 
     #[test]
     fn unit_key_validation_gates_on_real_ciphertext() {
-        use crate::aacs::decrypt::{ALIGNED_UNIT_LEN, ts_sync_destroyed};
+        use crate::aacs::content::{ALIGNED_UNIT_LEN, ts_sync_destroyed};
 
         // No samples -> nothing to disprove against -> accept (sample-less paths
         // like resume / mapfile must be unaffected).
@@ -5174,7 +5444,7 @@ mod tests {
         // CPS-unit-1 sectors then passed through as raw encrypted bytes into the
         // ISO/MKV with no error surfaced. The gate must now reject a key set
         // that leaves any scrambled sample uncovered.
-        use crate::aacs::decrypt::{ALIGNED_UNIT_LEN, ts_sync_destroyed};
+        use crate::aacs::content::{ALIGNED_UNIT_LEN, ts_sync_destroyed};
 
         let mut clear = vec![0u8; ALIGNED_UNIT_LEN];
         let mut off = 4;
@@ -5220,7 +5490,8 @@ mod tests {
     /// unit algorithm — ECB-derive the per-unit key, then AES-CBC encrypt the
     /// body with the fixed AACS IV.
     fn encrypt_unit_for_test(clear: &[u8], uk: &[u8; 16]) -> Vec<u8> {
-        use crate::aacs::decrypt::{AACS_IV, ALIGNED_UNIT_LEN};
+        use crate::aacs::content::ALIGNED_UNIT_LEN;
+        use crate::aacs::crypto::AACS_IV;
         use aes::Aes128;
         use aes::cipher::{BlockEncrypt, KeyInit, generic_array::GenericArray};
         let mut unit = clear[..ALIGNED_UNIT_LEN].to_vec();

src/disc/patch.rs

@@ -473,9 +473,7 @@ pub(super) fn recovery_read<R: SectorSource + ?Sized>(
 /// gets recorded NonTrimmed. Pure data structure — no I/O — so each phase
 /// helper is unit-testable by asserting the residual `SubRanges`.
 ///
-/// Foundation for the phased `recover_section` orchestrator; not yet wired
-/// into the live loop (see the deferral note in the #50 work).
-#[cfg_attr(not(test), allow(dead_code))]
+/// The residue tracker used by the phased `recover_section` orchestrator.
 #[derive(Debug, Clone, PartialEq, Eq, Default)]
 pub(super) struct SubRanges {
     /// (pos, len) pairs, sorted by pos, non-overlapping, all non-zero len.
@@ -1461,13 +1459,22 @@ impl Disc {
                     if !bad.is_empty() {
                         let n: usize = bad.len();
                         for (lba, cnt) in bad {
-                            let _ = m.record(
+                            if let Err(e) = m.record(
                                 lba as u64 * 2048,
                                 cnt as u64 * 2048,
                                 mapfile::SectorStatus::NonTrimmed,
+                            ) {
+                                tracing::warn!(
+                                    lba,
+                                    "reverify downgrade: mapfile record failed ({e}) — unit may stay mismarked as good"
+                                );
+                            }
+                        }
+                        if let Err(e) = m.flush() {
+                            tracing::warn!(
+                                "reverify downgrade: mapfile flush failed ({e}) — downgrade not persisted; a resume could mismark it good"
                             );
                         }
-                        let _ = m.flush();
                         // The re-verify ran AFTER `pipe.finish()` snapshotted
                         // `summary.stats`, so those stats still count the just-
                         // downgraded units as good. Refresh from the mapfile so
@@ -1547,14 +1554,13 @@ mod tests {
         assert!(on("true"));
     }
 
-    /// Transport failure (status=0xFF, USB-bridge crash) must be recognised by
-    /// the gate `handle_read_failure` now checks FIRST, so it aborts the pass
-    /// (wedged_exit + BreakOuter) instead of treating the bridge crash as an
-    /// ordinary bad sector and hammering the crashed device for up to the
-    /// per-range watchdog budget. `handle_read_failure` is not unit-testable in
-    /// isolation, so this guards the classification predicate the production
-    /// early-return keys off, and the contrast that an ordinary read error is
-    /// NOT misclassified as a transport failure.
+    /// Transport failure (status=0xFF, USB-bridge crash) must be recognised and
+    /// abort the pass, rather than being treated as an ordinary bad sector and
+    /// hammering the crashed device for up to the per-range watchdog budget. The
+    /// transport-failure classification predicate is not unit-testable in
+    /// isolation, so this guards the predicate the production early-return keys
+    /// off, and the contrast that an ordinary read error is NOT misclassified as
+    /// a transport failure.
     #[test]
     fn transport_failure_is_recognised_for_patch_abort() {
         use crate::scsi::SCSI_STATUS_TRANSPORT_FAILURE;

src/disc/read_error.rs

@@ -196,22 +196,10 @@ impl ReadCtx {
     /// threshold is loose so we don't bail too early on a range that
     /// has scattered good sectors mixed in.
     ///
-    /// `damage_threshold_pct = 6` mirrors `disc/patch.rs`'s
-    /// `PASSN_DAMAGE_THRESHOLD_PCT`. Pass N triggers the damage-skip
-    /// at half the density Pass 1 uses (Pass 1 = 12%) because the
-    /// patch loop's whole job is to chip away at bad ranges — being
-    /// more eager to skip clustered bad sectors converges faster on
-    /// the recoverable good sectors inside a range. The patch-side
-    /// `compute_damage_skip` reads its threshold directly from
-    /// `PASSN_DAMAGE_THRESHOLD_PCT`, which is an alias for this crate's
-    /// `PATCH_DAMAGE_THRESHOLD_PCT`, so the two are always in sync.
-    /// The patch loop's damage-skip is not yet unified with `handle_read_error`'s
-    /// jump path. (v0.20.8 unification attempt found the unification
-    /// itself blocked on the size-aware `range_remaining/4` cap that
-    /// lives in `compute_damage_skip` but not in
-    /// `handle_read_error::JumpAhead` — see
-    /// `tests/passn_handler_ab.rs` for the A/B fixture that pins
-    /// the divergence point.)
+    /// `damage_threshold_pct = 6` is looser than Pass 1 (12%): Pass N triggers
+    /// the damage-skip at half Pass 1 density because the patch loop exists to chip
+    /// away at bad ranges, so being more eager to skip clustered bad sectors
+    /// converges faster on the recoverable good sectors inside a range.
     pub fn for_patch(batch: u16) -> Self {
         Self {
             batch,
@@ -443,8 +431,8 @@ const WEDGE_ABORT_THRESHOLD: u64 = 16;
 const WEDGE_PASS_N_SKIP_SECTORS: u64 = 64;
 
 /// Single source of truth for the Pass-N damage-window threshold.
-/// Both [`ReadCtx::for_patch`] and `disc::patch::compute_damage_skip`
-/// reference this constant so the two damage-skip paths cannot drift.
+/// [`ReadCtx::for_patch`] reads this constant for the Pass-N damage-skip
+/// threshold.
 ///
 /// 6% means: with a 16-entry sliding window, the damage-skip fires
 /// once 1 out of 16 recent reads has failed. Pass 1 uses a 12%

src/disc/verify.rs

@@ -6,8 +6,11 @@
 //! decrypt-verify are meaningful is each clip's FILE-anchored 6144-byte unit
 //! grid (clips can start off the 6144 grid and fragment across UDF extents). So
 //! this gate BUFFERS the disc-absolute read stream and re-ALIGNS it into
-//! clip-file units, then applies the standards-correct
-//! [`crate::aacs::unit_is_clean_ts`] gate (libaacs `_verify_ts`, all-32 syncs).
+//! clip-file units, then decrypts each with the SAME primitive the mux/rip path
+//! uses ([`crate::aacs::content::decrypt_unit`] for TS) so verify and the real
+//! decrypt can never disagree. That verdict is "did a key OPEN this unit?" —
+//! defect-TOLERANT: an opened unit carrying a few authored-bad packets (pressing
+//! defects / forensic-variant frames) is NOT bad; only a unit no key opens is.
 //!
 //! FAIL-SAFE CONTRACT (this sits in the middle of every read, so it must never
 //! break a good read): the gate can ONLY downgrade a unit it is *confident* is
@@ -25,7 +28,8 @@
 
 use std::collections::{HashMap, VecDeque};
 
-use crate::aacs::{self, ALIGNED_UNIT_LEN};
+use crate::aacs::content::ALIGNED_UNIT_LEN;
+use crate::aacs::{self};
 use crate::consts::SECTOR_BYTES_U64;
 use crate::decrypt::DecryptKeys;
 use crate::sector::KeyFetch;
@@ -57,10 +61,19 @@ pub enum ContainerKind {
     Ts,
     /// HD-DVD `.evo` — MPEG-2 program stream (pack-start `00 00 01 BA`).
     /// NOT yet enabled by enumeration; present so adding HD-DVD is a one-mapping
-    /// change. See [`crate::aacs::unit_is_clean_ps`] for the (unvalidated) check.
+    /// change. See [`crate::aacs::content::unit_is_clean_ps`] for the (unvalidated) check.
     Ps,
 }
 
+/// PS-container per-unit decrypt for the verify gate — the analogue of
+/// [`aacs::content::decrypt_unit`] (TS) for HD-DVD program-stream content. Wraps
+/// [`aacs::content::decrypt_unit_checked`] with the pack-start structural check.
+/// A free `fn` (not a closure) so it has the same `fn(&mut [u8], &[u8;16]) -> bool`
+/// type as `decrypt_unit`, letting [`Verifier::decrypt_for`] return either.
+fn decrypt_unit_ps(unit: &mut [u8], key: &[u8; 16]) -> bool {
+    aacs::content::decrypt_unit_checked(unit, key, aacs::content::unit_is_clean_ps)
+}
+
 /// A clip's on-disc layout: declared file size, its absolute disc extents in
 /// FILE order, and its stream container. `extents` is `(disc_lba, byte_len)`;
 /// the verifier reuses exactly the same `(abs_lba, byte_len)` extents the
@@ -184,11 +197,28 @@ impl UnitVerifier {
         })
     }
 
-    /// The post-decrypt structural check for a clip's container.
+    /// The post-decrypt structural check for a clip's container — used ONLY on the
+    /// CPI-clear branch (a plaintext unit that is structurally clean is
+    /// decryptable-as-is; if not, we return Unknown, never bad).
     fn accept_for(&self, clip: u32) -> fn(&[u8]) -> bool {
         match self.containers[clip as usize] {
-            ContainerKind::Ts => aacs::unit_is_clean_ts,
-            ContainerKind::Ps => aacs::unit_is_clean_ps,
+            ContainerKind::Ts => aacs::content::unit_is_clean_ts,
+            ContainerKind::Ps => aacs::content::unit_is_clean_ps,
+        }
+    }
+
+    /// The per-unit DECRYPT for a clip's container — the key-selection primitive
+    /// verify uses to prove a candidate key opens an ENCRYPTED unit. It MUST be
+    /// the exact same primitive the mux/rip decrypt path uses, so verify and the
+    /// real decrypt never disagree (a unit the mux will happily decrypt must not
+    /// be marked bad here). For TS that is [`aacs::content::decrypt_unit`], whose
+    /// verdict is defect-TOLERANT (a supermajority of content packets restored) —
+    /// an authored-bad packet or forensic-variant frame no longer false-flags the
+    /// whole unit as undecryptable.
+    fn decrypt_for(&self, clip: u32) -> fn(&mut [u8], &[u8; 16]) -> bool {
+        match self.containers[clip as usize] {
+            ContainerKind::Ts => aacs::content::decrypt_unit,
+            ContainerKind::Ps => decrypt_unit_ps,
         }
     }
 
@@ -214,7 +244,8 @@ impl UnitVerifier {
             self.fill(clip, unit, slot, lba, &bytes[off..off + sector]);
             if let Some((raw, lbas)) = self.take_if_complete(clip, unit) {
                 let accept = self.accept_for(clip);
-                match self.decryptability(&raw, accept) {
+                let decrypt = self.decrypt_for(clip);
+                match self.decryptability(&raw, accept, decrypt) {
                     Decryptability::Undecryptable => push_ranges(&mut bad, &lbas),
                     Decryptability::Decryptable | Decryptability::Unknown => {}
                 }
@@ -301,13 +332,14 @@ impl UnitVerifier {
     }
 
     /// Can this fully-assembled unit be decrypted + verified? `accept` is the
-    /// container's strict structural check ([`aacs::unit_is_clean_ts`] for TS,
-    /// [`aacs::unit_is_clean_ps`] for PS) — the only format-specific part; the
+    /// container's strict structural check ([`aacs::content::unit_is_clean_ts`] for TS,
+    /// [`aacs::content::unit_is_clean_ps`] for PS) — the only format-specific part; the
     /// AACS crypto is container-agnostic. Returns the 3-state [`Decryptability`].
     fn decryptability(
         &mut self,
         raw: &[u8; ALIGNED_UNIT_LEN],
         accept: fn(&[u8]) -> bool,
+        decrypt: fn(&mut [u8], &[u8; 16]) -> bool,
     ) -> Decryptability {
         // CPI clear -> the unit is plaintext by spec (no key needed). If it is
         // structurally clean, it is decryptable-as-is. If it ISN'T, we
@@ -318,7 +350,7 @@ impl UnitVerifier {
         // ENCRYPTED units that no key opens are ever flagged. (A real bad READ of
         // clear content is still caught by the normal SCSI read-error path; this
         // gate just won't false-flag it.)
-        if !aacs::aacs_unit_encrypted(raw) {
+        if !aacs::content::aacs_unit_encrypted(raw) {
             return if accept(raw) {
                 Decryptability::Decryptable
             } else {
@@ -326,7 +358,7 @@ impl UnitVerifier {
             };
         }
         // Encrypted: any held key that decrypts to a structurally-clean unit.
-        if self.try_keys(raw, accept) {
+        if self.try_keys(raw, decrypt) {
             return Decryptability::Decryptable;
         }
         // No held key works. Ask the application's key source ONCE for this
@@ -349,7 +381,7 @@ impl UnitVerifier {
                     self.fetch_spent = true; // service has nothing new; stop asking
                     return Decryptability::Unknown;
                 }
-                if self.try_keys(raw, accept) {
+                if self.try_keys(raw, decrypt) {
                     return Decryptability::Decryptable;
                 }
                 return Decryptability::Undecryptable; // service's keys don't open it -> bad ciphertext
@@ -358,12 +390,18 @@ impl UnitVerifier {
         Decryptability::Unknown
     }
 
-    /// True if any currently-held key decrypts `raw` to a structurally-clean unit
-    /// under the container's `accept` check.
-    fn try_keys(&self, raw: &[u8; ALIGNED_UNIT_LEN], accept: fn(&[u8]) -> bool) -> bool {
+    /// True if any currently-held key OPENS `raw` — i.e. the container's per-unit
+    /// `decrypt` (the same primitive the mux uses) reports the key restored the
+    /// unit's TS structure. Defect-tolerant for TS: an opened unit carrying a few
+    /// authored-bad packets still counts as decryptable (never marked bad).
+    fn try_keys(
+        &self,
+        raw: &[u8; ALIGNED_UNIT_LEN],
+        decrypt: fn(&mut [u8], &[u8; 16]) -> bool,
+    ) -> bool {
         for k in &self.keys {
             let mut scratch = *raw;
-            if aacs::decrypt_unit_checked(&mut scratch, k, accept) {
+            if decrypt(&mut scratch, k) {
                 return true;
             }
         }
@@ -438,9 +476,10 @@ impl UnitVerifier {
                     }
                 }
                 let accept = self.accept_for(clip);
+                let decrypt = self.decrypt_for(clip);
                 if readable
                     && matches!(
-                        self.decryptability(&raw, accept),
+                        self.decryptability(&raw, accept, decrypt),
                         Decryptability::Undecryptable
                     )
                 {
@@ -523,13 +562,13 @@ mod tests {
         use aes::cipher::{BlockEncrypt, KeyInit, generic_array::GenericArray};
         unit[0] |= 0xC0; // CPI flag => reads as encrypted
         let header: [u8; 16] = unit[..16].try_into().unwrap();
-        let derived = crate::aacs::decrypt::aes_ecb_encrypt(unit_key, &header);
+        let derived = crate::aacs::crypto::aes_ecb_encrypt(unit_key, &header);
         let mut k = [0u8; 16];
         for i in 0..16 {
             k[i] = derived[i] ^ header[i];
         }
         let cipher = Aes128::new(GenericArray::from_slice(&k));
-        let mut prev = crate::aacs::decrypt::AACS_IV;
+        let mut prev = crate::aacs::crypto::AACS_IV;
         for i in 0..(ALIGNED_UNIT_LEN - 16) / 16 {
             let off = 16 + i * 16;
             for j in 0..16 {
@@ -897,6 +936,31 @@ mod tests {
         );
     }
 
+    #[test]
+    fn reverify_iso_defect_packet_unit_is_not_flagged_bad() {
+        // A unit with ONE authored-bad content packet (a pressing defect). The
+        // held key OPENS it (31/32 syncs restored), so verify must AGREE with the
+        // mux decrypt and NOT mark it bad — the bad packet is the muxer's problem,
+        // not a read/decrypt failure. (Old strict all-32 gate flagged it bad.)
+        let key = [0x5a; 16];
+        let mut u = clear_unit();
+        let off = 17 * 192; // corrupt packet 17's sync in the plaintext
+        u[off + 4] = 0x80;
+        u[off + 5] = 0xAB;
+        encrypt_unit(&mut u, &key);
+        let mut iso = MockIso {
+            sectors: Default::default(),
+            err_lba: None,
+        };
+        place_unit(&mut iso, [100, 101, 102], &u);
+        let mut v = UnitVerifier::new(&one_clip(100), &aacs_keys(&[key]), None).unwrap();
+        let bad = v.reverify_iso(&mut iso, &[(100 * 2048, 3 * 2048)], &|_| true);
+        assert!(
+            bad.is_empty(),
+            "defect-packet unit is opened by the held key -> not flagged bad"
+        );
+    }
+
     #[test]
     fn reverify_iso_fragmented_unit_reads_distant_sectors() {
         let key = [0x5a; 16];

src/drive/mod.rs

@@ -433,15 +433,14 @@ impl Drive {
         // that used to sit here was the v1.0.0-rc.1 regression — it skipped the
         // drive-prep for DVD, leaving DVDs riplocked at stock speed.
         self.init_ran = true;
-        let r: Result<()> = match crate::unlock_bridge::run_unlockers(
-            self.scsi.as_mut(),
-            &self.drive_id,
-            freemkv_unlock::DiscKind::Unknown,
-            &[],
-        ) {
+        let (matched, unlock_res) =
+            crate::unlock_bridge::run_features(self.scsi.as_mut(), &self.drive_id);
+        let r: Result<()> = match unlock_res {
             Ok(unlocked) => {
-                self.unlocker_name =
-                    crate::unlock_bridge::unlocker_name(&self.drive_id).map(str::to_string);
+                // Record WHICH drive-prep unlocker actually ran — "LibreDrive"
+                // (MediaTek) or "Renesas" — not the ld-only identity lookup, so a
+                // Renesas drive reports itself honestly rather than as nothing.
+                self.unlocker_name = Some(matched.to_string());
                 // Stash the OEM Volume ID the unlocker returned for the AACS
                 // handshake phase (do_handshake reads it via `oem_vid()`). A
                 // drive-prep unlocker always carries a VID; guard anyway.

src/dvdnav/mod.rs

@@ -6,7 +6,7 @@
 //!
 //! Byte layout follows the DVD-Video specification (VMGI/VTSI headers,
 //! PGC/cell tables, PCI/HLI button packets); the VM command decoder is
-//! verified against libdvdnav's decoder.
+//! verified against real discs.
 //!
 //! Current contents: [`vmcmd`] — the VM command decoder (proven against the
 //! SOTL/Greenland test discs). The IFO/PCI parsing and the navigation executor

src/dvdnav/vmcmd.rs

@@ -2,7 +2,7 @@
 //!
 //! An 8-byte navigation command as found in PGC command tables (pre/post/cell)
 //! and PCI button info. Decoded per the DVD-Video VM instruction set and
-//! verified against libdvdnav's command decoder.
+//! verified against real discs.
 //!
 //! Bit model: the 8 bytes are a big-endian 64-bit word. `byte0` bits 7-5 are the
 //! command **type**; for type 1, `byte0` bit 4 selects Link (0) vs Jump (1), and
@@ -133,7 +133,7 @@ const JP_JUMP_SS: u8 = 6;
 const JP_CALL_SS: u8 = 8;
 
 // Link (type 1, direct=0) sub-commands. NOTE: sub-op 0 is NOP/no-link and 1 is
-// the LinkSub form (libdvdnav `decoder.c` `eval_link_instruction`).
+// the LinkSub form (the DVD-Video VM link instruction).
 const LK_SUB: u8 = 1;
 const LK_PGCN: u8 = 4;
 const LK_PTTN: u8 = 5;
@@ -159,7 +159,7 @@ fn be16(b: &[u8; 8], o: usize) -> u16 {
     ((b[o] as u16) << 8) | b[o + 1] as u16
 }
 
-// Compare-operand layouts ("if_version"s) per libdvdnav `decoder.c`. The op
+// Compare-operand layouts ("if_version"s) per the DVD-Video VM. The op
 // nibble is always `byte1` bits 6-4; the immediate flag is `byte1` bit 7. The
 // operand *offsets* differ by command family.
 //
@@ -205,7 +205,7 @@ pub fn decode(b: &[u8; 8]) -> Command {
     let cmd = b[1] & 0x0F;
 
     // Compare predicate, with the operand layout for this command family
-    // (libdvdnav `decoder.c` `vm_eval_command` type dispatch).
+    // (the DVD-Video VM command type dispatch).
     let compare = match (typ, direct) {
         (TYPE_SPECIAL, _) => if_v1(b),
         (TYPE_LINK_JUMP, 1) => if_v2(b), // jump
@@ -372,7 +372,7 @@ mod tests {
         }
     }
 
-    // Regression for the libdvdnav cross-check: link sub-op 0 = NOP, 1 = LinkSub.
+    // Regression for the link sub-op decode: 0 = NOP, 1 = LinkSub.
     #[test]
     fn link_subop_zero_is_nop_one_is_linksub() {
         assert_eq!(decode(&h("2000000000000000")).instr, Instr::Nop);

src/error.rs

@@ -88,6 +88,7 @@ pub const E_NO_DISC_KEY: u16 = 7022;
 pub const E_CSS_KEY_MISSING: u16 = 7023;
 pub const E_AACS_NO_HOST_CERT: u16 = 7024;
 pub const E_AACS_BUS_KEY_UNAVAILABLE: u16 = 7025;
+pub const E_FMTS_KEY_MISSING: u16 = 7026;
 
 // Keydb (8xxx)
 pub const E_KEYDB_CONNECT: u16 = 8000;
@@ -360,6 +361,15 @@ pub enum Error {
     /// time and no handshake runs.
     AacsBusKeyUnavailable,
 
+    /// AACS 2.1 (FMTS) disc carries forensic variant segments, but no segment
+    /// (variant) key is available to open them, and `BYPASS_FMTS_KEY` is `false`
+    /// (strict mode). Raised UPFRONT — before the mux — exactly like a missing
+    /// unit key, so a 2.1 disc that would rip with holes is refused rather than
+    /// silently producing a forensic-holed output. When `BYPASS_FMTS_KEY` is
+    /// `true` (the default today) this is never raised: the bulk decodes with the
+    /// unit key and the forensic segments are skipped as expected loss.
+    FmtsKeyMissing,
+
     // Keydb (8xxx)
     KeydbConnect {
         host: String,
@@ -573,6 +583,7 @@ impl Error {
             Error::CssKeyMissing => E_CSS_KEY_MISSING,
             Error::AacsNoHostCert { .. } => E_AACS_NO_HOST_CERT,
             Error::AacsBusKeyUnavailable => E_AACS_BUS_KEY_UNAVAILABLE,
+            Error::FmtsKeyMissing => E_FMTS_KEY_MISSING,
             Error::KeydbConnect { .. } => E_KEYDB_CONNECT,
             Error::KeydbHttp { .. } => E_KEYDB_HTTP,
             Error::KeydbInvalid => E_KEYDB_INVALID,
@@ -1209,6 +1220,7 @@ mod tests {
             E_CSS_KEY_MISSING,
             E_AACS_NO_HOST_CERT,
             E_AACS_BUS_KEY_UNAVAILABLE,
+            E_FMTS_KEY_MISSING,
             E_KEYDB_CONNECT,
             E_KEYDB_HTTP,
             E_KEYDB_INVALID,

src/ifo.rs

@@ -58,7 +58,7 @@ pub struct DvdTitle {
 pub struct DvdCell {
     pub first_sector: u32,
     pub last_sector: u32,
-    /// Raw cell-category byte at `cell_playback + 0` (libdvdread layout).
+    /// Raw cell-category byte at `cell_playback + 0` (DVD-Video IFO layout).
     /// Packs block_mode (bits 7-6), block_type (bits 5-4), seamless_play
     /// (bit 3), interleaved (bit 2), stc_discontinuity (bit 1),
     /// seamless_angle (bit 0). Carried so the extent builder can recognise
@@ -72,7 +72,7 @@ pub struct DvdCell {
 }
 
 /// Decoded view of a cell-category byte (`cell_playback + 0`), per the
-/// DVD-Video spec / libdvdread `cell_playback_t` layout. Byte-0 bitfields,
+/// DVD-Video IFO cell-playback layout. Byte-0 bitfields,
 /// MSB-first: `block_mode`(7-6), `block_type`(5-4), `seamless_play`(3),
 /// `interleaved`(2), `stc_discontinuity`(1), `seamless_angle`(0). (The real
 /// `cell_type` is a karaoke-only field in byte 1, not used here.)
@@ -93,7 +93,7 @@ pub struct CellCategory {
 }
 
 impl CellCategory {
-    /// Decode the raw `cell_playback + 0` byte (libdvdread `read_cell_playback`).
+    /// Decode the raw `cell_playback + 0` byte (DVD-Video IFO cell playback).
     pub fn decode(raw: u8) -> Self {
         CellCategory {
             block_mode: (raw >> 6) & 0x03,
@@ -423,7 +423,7 @@ fn parse_vts(
     }
 
     // VTSI_MAT (VTS_xx_0.IFO header) field offsets — fixed by the DVD-Video
-    // spec (libdvdread `vtsi_mat_t`). The offsets are constant; the sector
+    // spec (the VTSI management table). The offsets are constant; the sector
     // values they point to are per-disc.
     const VTSTT_VOBS_OFFSET: usize = 0xC4; // VTS title VOBS start sector (feature)
     const VTS_PGCIT_OFFSET: usize = 0xCC; // VTS_PGCIT sector pointer
@@ -580,7 +580,7 @@ fn parse_audio_attr(data: &[u8], offset: usize) -> Result<DvdAudioAttr> {
         _ => Codec::Unknown(coding_mode),
     };
 
-    let sample_rate_flag = (b1 >> 4) & 0x03; // sample_frequency: byte 1 bits 5-4 (libdvdread audio_attr_t)
+    let sample_rate_flag = (b1 >> 4) & 0x03; // sample_frequency: byte 1 bits 5-4 (DVD-Video audio attributes)
     let sample_rate = match sample_rate_flag {
         0 => 48000,
         1 => 96000,
@@ -1071,7 +1071,7 @@ mod tests {
     /// reads with — a co-edit of constant + helper would silently re-introduce
     /// the PAL-as-NTSC bug and every test would still pass. This test feeds
     /// `parse_video_attr` HARDCODED bytes captured from real DVD-Video layouts
-    /// (DVD spec / libdvdread `video_attr_t`: mpeg_version[7-6] video_format[5-4]
+    /// (DVD-Video video attributes: mpeg_version[7-6] video_format[5-4]
     /// display_aspect[3-2] permitted_df[1-0]) — no `v_atr_byte`. If the parser's
     /// bit positions drift, these fail.
     #[test]
@@ -1238,7 +1238,7 @@ mod tests {
 
     // ─────────────────────────────────────────────────────────────────────
     // Added hardening tests. Grounded in the DVD-Video IFO spec
-    // (dvd_udf / libdvdread ifo_types.h; http://dvd.sourceforge.net).
+    // (DVD-Video IFO format; http://dvd.sourceforge.net).
     // ─────────────────────────────────────────────────────────────────────
 
     /// BCD frame-rate flag: bits 7-6 of byte[3]. 0b01 = 25fps (PAL),
@@ -1593,7 +1593,7 @@ mod tests {
         }
     }
 
-    /// CellCategory decodes the libdvdread byte-0 bitfields: block_mode (7-6),
+    /// CellCategory decodes the DVD-Video cell-category byte-0 bitfields: block_mode (7-6),
     /// block_type (5-4), seamless_play (3), interleaved (2),
     /// stc_discontinuity (1), seamless_angle (0).
     #[test]

src/io/pipeline.rs

@@ -449,7 +449,10 @@ impl<I: Send + 'static, R: Send + 'static> Pipeline<I, R> {
                     } else {
                         // Benign per-item OK: trace-level (L4) only; the
                         // apply-side rolling summary carries throughput.
-                        tracing::trace!("Pipeline send: OK in {:.3}ms", elapsed.as_micros());
+                        tracing::trace!(
+                            "Pipeline send: OK in {:.3}ms",
+                            elapsed.as_secs_f64() * 1000.0
+                        );
                     }
                 }
                 Ok(())
@@ -464,7 +467,10 @@ impl<I: Send + 'static, R: Send + 'static> Pipeline<I, R> {
                             std::any::type_name::<I>()
                         );
                     } else {
-                        tracing::debug!("Pipeline send: failed after {:.3}ms", elapsed.as_micros());
+                        tracing::debug!(
+                            "Pipeline send: failed after {:.3}ms",
+                            elapsed.as_secs_f64() * 1000.0
+                        );
                     }
                 }
                 Err(e.0)

src/keysource.rs

@@ -3,12 +3,13 @@
 //! libfreemkv performs NO key lookup. An application resolves a disc's keys
 //! through one or more [`KeySource`]s, each an adapter over a backing store (a
 //! keydb file, a key server, the mapfile cache). A source's job is to return the
-//! disc's terminal **Unit Keys** ([`crate::aacs::UnitKey`]). It knows what
+//! disc's terminal **Unit Keys** ([`crate::aacs::types::UnitKey`]). It knows what
 //! material it holds (a DK / MK / VUK / pre-decrypted UK) and what it must fetch
 //! from the disc (VID, MKB, encrypted title keys, content samples) to get there;
-//! it orchestrates the derivation by calling libfreemkv's own boil-down crypto
-//! primitives ([`crate::aacs::mk_from_dk`] / [`crate::aacs::vuk_from_mk`] /
-//! [`crate::aacs::uk_from_vuk`]) through the [`ResolveCtx`] handed to it.
+//! it orchestrates the derivation by calling libfreemkv's own derivation
+//! primitives ([`crate::aacs::derive::derive_media_key_from_dk`] /
+//! [`crate::aacs::derive::derive_vuk`] / [`crate::aacs::derive::decrypt_unit_key`])
+//! through the [`ResolveCtx`] handed to it.
 //!
 //! libfreemkv still OWNS the crypto: the boil-down primitives and the AES live
 //! here. A source owns only PATH ORCHESTRATION — deciding which primitive to
@@ -17,7 +18,8 @@
 //! keeping key *policy* (which store, which order, online vs local) out of the
 //! library.
 
-use crate::aacs::{HostCert, UnitKey, Vid};
+use crate::aacs::types::HostCert;
+use crate::aacs::types::{UnitKey, Vid};
 use crate::disc::Key;
 use crate::error::Error;
 
@@ -74,8 +76,8 @@ pub trait ResolveCtx {
     /// Raw MKB bytes (may be empty when not captured).
     fn mkb(&self) -> Result<&[u8], Error>;
     /// The disc's encrypted title keys, parsed from `Unit_Key_RO.inf` the same
-    /// way the library's resolver parses them ([`crate::aacs::parse_unit_key_ro`]),
-    /// in on-disc order. Feed straight into [`crate::aacs::uk_from_vuk`].
+    /// way the library's resolver parses them ([`crate::aacs::inf::parse_unit_key_ro`]),
+    /// in on-disc order. Feed straight into [`crate::aacs::derive::decrypt_unit_key`].
     fn enc_title_keys(&self) -> Result<&[[u8; 16]], Error>;
     /// Up to `n` encrypted on-disc content sample units, for a source that
     /// validates a candidate server-side against real ciphertext.
@@ -113,7 +115,8 @@ impl<'a> DiscInputsCtx<'a> {
     /// title keys — the parse failure is swallowed here, not surfaced as an
     /// error.
     pub fn new(inputs: &'a DiscInputs) -> Self {
-        use crate::aacs::{AacsVersion, parse_unit_key_ro};
+        use crate::aacs::inf::parse_unit_key_ro;
+        use crate::aacs::mkb::AacsVersion;
         let enc_keys = if inputs.unit_key_ro.is_empty() {
             Vec::new()
         } else {
@@ -164,8 +167,8 @@ impl ResolveCtx for DiscInputsCtx<'_> {
 /// holds, orchestrates the derivation down to Unit Keys using the library's
 /// boil-down crypto primitives — never re-implementing AES. A source that holds
 /// pre-decrypted Unit Keys returns them directly; one that holds a VUK calls
-/// [`crate::aacs::uk_from_vuk`]; one that holds device keys calls
-/// [`crate::aacs::mk_from_dk`] → [`crate::aacs::vuk_from_mk`] → `uk_from_vuk`.
+/// [`crate::aacs::derive::decrypt_unit_key`]; one that holds device keys calls
+/// [`crate::aacs::derive::derive_media_key_from_dk`] → [`crate::aacs::derive::derive_vuk`] → `decrypt_unit_key`.
 ///
 /// Returning an empty `Vec` means "no key for this disc from this source"; an
 /// `Err` means the source itself failed (I/O, parse, network). The caller
@@ -209,7 +212,7 @@ pub fn resolve_and_apply(
 }
 
 /// Like [`resolve_and_apply`] but also returns a structured
-/// [`crate::aacs::ResolutionTrace`] recording, per source, what happened — for
+/// [`crate::aacs::trace::ResolutionTrace`] recording, per source, what happened — for
 /// applications to render. ZERO English; the trace is typed enums only.
 ///
 /// One-shot per source: each source's [`KeySource::get_uk`] is called exactly
@@ -219,8 +222,8 @@ pub fn resolve_and_apply(
 /// success — so a wrong/partial key set is rejected and the loop continues.
 ///
 /// CPS-unit numbering: a source returns Unit Keys carrying the POSITIONAL index
-/// from [`crate::aacs::uk_from_vuk`]; the library's canonical CPS-unit number is
-/// `position + 1` (matching [`crate::aacs::parse_unit_key_ro`]'s `(i + 1)`), so
+/// from [`crate::aacs::derive::decrypt_unit_key`]; the library's canonical CPS-unit number is
+/// `position + 1` (matching [`crate::aacs::inf::parse_unit_key_ro`]'s `(i + 1)`), so
 /// the committed `AacsState.unit_keys` is byte-identical to the library-resolved
 /// path. The number is cosmetic for descramble (the decrypt path strips it and
 /// tries every key) but is kept faithful to the resolver's convention.
@@ -228,10 +231,10 @@ pub fn resolve_and_apply_traced(
     sources: &[Box<dyn KeySource>],
     inputs: &DiscInputs,
     disc: &mut crate::Disc,
-) -> (bool, crate::aacs::ResolutionTrace) {
+) -> (bool, crate::aacs::trace::ResolutionTrace) {
     use crate::aacs::trace::{KeyNode, KeyOutcome, KeyStep};
 
-    let mut trace = crate::aacs::ResolutionTrace::new();
+    let mut trace = crate::aacs::trace::ResolutionTrace::new();
 
     // The ctx parses Unit_Key_RO.inf at the stride for `inputs.version` (the
     // disc's own AACS major), so the stride is the disc's single source of truth.
@@ -341,18 +344,24 @@ pub fn key_fetch(
 /// `start_lba`), which the library owns. A key source is *handed* these bytes
 /// via `DiscInputs.samples`; it never reads the disc itself.
 ///
-/// "Encrypted" is decided by [`crate::aacs::ts_sync_destroyed`] — the SAME
-/// predicate the decrypt gate uses — so all sides agree. A clip opens with clear
-/// navigation units (PAT/PMT, menus); only the feature body is scrambled, and a
-/// clear unit proves nothing, so this collects only scrambled ones — probing
-/// several points spread across EACH extent so a title whose encrypted body
-/// starts late (or whose midpoint lands in clear nav) still yields samples.
+/// "Encrypted" is decided by [`crate::aacs::content::aacs_unit_encrypted`] — the
+/// AACS Copy Permission Indicator (CPI) in the top 2 bits of byte 0, the
+/// spec-correct signal (`buf[0] & 0xc0`). NOT the `ts_sync_destroyed`
+/// sync heuristic: destroyed TS syncs do not imply encryption (an FMTS variant
+/// frame or an odd clear unit can lack syncs yet be unencrypted), and a clear
+/// unit sent to a key server yields nothing to validate against — the "0
+/// encrypted units" rejection. A clip opens with clear navigation units (PAT/PMT,
+/// menus) whose CPI is clear; only CPI-flagged content units are collected —
+/// probing several points spread across EACH extent so a title whose encrypted
+/// body starts late (or whose midpoint lands in clear nav) still yields samples.
+/// CPI is read at each extent's `start_lba` (clip-file-anchored), so byte 0 is a
+/// real unit start and the flag is meaningful.
 pub fn read_encrypted_units(
     reader: &mut dyn crate::sector::SectorSource,
     title: &crate::disc::DiscTitle,
     n: usize,
 ) -> Vec<Vec<u8>> {
-    use crate::aacs::{ALIGNED_UNIT_LEN, ALIGNED_UNIT_SECTORS, ts_sync_destroyed};
+    use crate::aacs::content::{ALIGNED_UNIT_LEN, ALIGNED_UNIT_SECTORS, aacs_unit_encrypted};
     const CHUNK_UNITS: u32 = 15; // 45 sectors/read — under the drive transfer cap
     // Probe several evenly-spaced points across EACH extent rather than only the
     // midpoint-and-forward: a title whose encrypted feature starts late, or whose
@@ -398,7 +407,7 @@ pub fn read_encrypted_units(
                     break;
                 }
                 let u = &buf[o..o + ALIGNED_UNIT_LEN];
-                if ts_sync_destroyed(u) {
+                if aacs_unit_encrypted(u) {
                     out.push(u.to_vec());
                     if out.len() >= n {
                         return out;
@@ -413,7 +422,7 @@ pub fn read_encrypted_units(
 #[cfg(test)]
 mod tests {
     use super::*;
-    use crate::aacs::UnitKey;
+    use crate::aacs::types::UnitKey;
     use std::sync::{Arc, Mutex};
 
     // ── KeySource default-method behaviour ────────────────────────────────────
@@ -454,7 +463,7 @@ mod tests {
         let inputs = DiscInputs {
             disc_hash: "0xABC".into(),
             volume_id: [0u8; 16],
-            version: crate::aacs::AACS_MAJOR_BD,
+            version: crate::aacs::mkb::AACS_MAJOR_BD,
             mkb: vec![1, 2, 3],
             unit_key_ro: uk_ro,
             samples: vec![vec![9u8; 4], vec![8u8; 4], vec![7u8; 4]],
@@ -510,7 +519,7 @@ mod tests {
         let inputs = DiscInputs {
             disc_hash: "0x00".into(),
             volume_id: [0u8; 16],
-            version: crate::aacs::AACS_MAJOR_UHD,
+            version: crate::aacs::mkb::AACS_MAJOR_UHD,
             mkb: Vec::new(),
             unit_key_ro: Vec::new(),
             samples: Vec::new(),
@@ -531,7 +540,7 @@ mod tests {
         DiscInputs {
             disc_hash: String::new(),
             volume_id: [0u8; 16],
-            version: crate::aacs::AACS_MAJOR_UHD,
+            version: crate::aacs::mkb::AACS_MAJOR_UHD,
             mkb: Vec::new(),
             unit_key_ro: Vec::new(),
             samples: Vec::new(),
@@ -554,10 +563,7 @@ mod tests {
     struct HasKey([u8; 16]);
     impl KeySource for HasKey {
         fn get_uk(&self, _ctx: &dyn ResolveCtx) -> Result<Vec<UnitKey>, Error> {
-            Ok(vec![UnitKey {
-                idx: 0,
-                key: self.0,
-            }])
+            Ok(vec![UnitKey::new(0, self.0)])
         }
     }
 
@@ -603,10 +609,7 @@ mod tests {
                 if let Ok(s) = ctx.samples(8) {
                     self.seen.lock().unwrap().extend(s);
                 }
-                Ok(vec![UnitKey {
-                    idx: 0,
-                    key: self.key,
-                }])
+                Ok(vec![UnitKey::new(0, self.key)])
             }
         }
 
@@ -621,7 +624,7 @@ mod tests {
         });
 
         let cb = key_fetch(empty_inputs(), make);
-        let samples = vec![vec![0xEEu8; crate::aacs::ALIGNED_UNIT_LEN]];
+        let samples = vec![vec![0xEEu8; crate::aacs::content::ALIGNED_UNIT_LEN]];
         let got = cb(&samples);
         assert_eq!(
             got,
@@ -643,7 +646,7 @@ mod tests {
     /// finds the early scrambled band.
     #[test]
     fn read_encrypted_units_finds_scrambled_content_off_the_midpoint() {
-        use crate::aacs::{ALIGNED_UNIT_LEN, ALIGNED_UNIT_SECTORS, ts_sync_destroyed};
+        use crate::aacs::content::{ALIGNED_UNIT_LEN, ALIGNED_UNIT_SECTORS, aacs_unit_encrypted};
         use crate::error::Result;
         use crate::sector::SectorSource;
 
@@ -713,7 +716,98 @@ mod tests {
             "the probe-spread must sample the early scrambled band the midpoint misses"
         );
         for s in &samples {
-            assert!(ts_sync_destroyed(s), "every sample is a scrambled unit");
+            assert!(
+                aacs_unit_encrypted(s),
+                "every sample is a CPI-flagged encrypted unit (byte0 & 0xC0 != 0)"
+            );
+        }
+    }
+
+    /// DISCRIMINATING: selection is by the AACS CPI (byte 0), NOT the
+    /// `ts_sync_destroyed` heuristic. Half the units are sync-destroyed but
+    /// CPI-CLEAR (`byte0 & 0xC0 == 0`) — genuinely UNencrypted units that merely
+    /// lack TS syncs; the old sampler collected these and the key server rejected
+    /// the POST as "0 encrypted units". `read_encrypted_units` must skip them and
+    /// return ONLY CPI-flagged units. A regression to `ts_sync_destroyed` would
+    /// collect the CPI-clear units too and fail the `& 0xC0` assertion.
+    #[test]
+    fn read_encrypted_units_selects_by_cpi_not_ts_sync() {
+        use crate::aacs::content::{ALIGNED_UNIT_LEN, ALIGNED_UNIT_SECTORS, aacs_unit_encrypted};
+        use crate::error::Result;
+        use crate::sector::SectorSource;
+
+        // Even units: CPI-clear (byte0 & 0xC0 == 0) AND sync-destroyed (no 0x47).
+        // Odd units:  CPI-set (byte0 = 0xC0) with a scrambled body.
+        // `ts_sync_destroyed` is TRUE for BOTH; `aacs_unit_encrypted` only odd.
+        struct MixSource {
+            ext_start: u32,
+            total_units: u32,
+        }
+        impl SectorSource for MixSource {
+            fn capacity_sectors(&self) -> u32 {
+                self.ext_start + self.total_units * ALIGNED_UNIT_SECTORS + 64
+            }
+            fn read_sectors(
+                &mut self,
+                lba: u32,
+                count: u16,
+                buf: &mut [u8],
+                _r: bool,
+            ) -> Result<usize> {
+                let bytes = count as usize * 2048;
+                for (i, chunk) in buf[..bytes].chunks_mut(ALIGNED_UNIT_LEN).enumerate() {
+                    if chunk.len() < ALIGNED_UNIT_LEN {
+                        break;
+                    }
+                    let abs = (lba - self.ext_start) / ALIGNED_UNIT_SECTORS + i as u32;
+                    if abs % 2 == 0 {
+                        chunk.fill(0x11); // CPI-clear (0x11 & 0xC0 == 0), no TS sync
+                    } else {
+                        chunk.fill(0xAB); // scrambled body (no TS sync)
+                        chunk[0] = 0xC0; // CPI set -> encrypted
+                    }
+                }
+                Ok(bytes)
+            }
+        }
+
+        let total_units = 400u32;
+        let ext_start = 500u32;
+        let mut src = MixSource {
+            ext_start,
+            total_units,
+        };
+        let title = crate::disc::DiscTitle {
+            playlist: String::new(),
+            playlist_id: 0,
+            duration_secs: 0.0,
+            size_bytes: 0,
+            clips: Vec::new(),
+            streams: Vec::new(),
+            chapters: Vec::new(),
+            extents: vec![crate::disc::Extent {
+                start_lba: ext_start,
+                sector_count: total_units * ALIGNED_UNIT_SECTORS,
+            }],
+            content_format: crate::disc::ContentFormat::BdTs,
+            codec_privates: Vec::new(),
+        };
+
+        let samples = read_encrypted_units(&mut src, &title, 8);
+        assert!(
+            !samples.is_empty(),
+            "the CPI-flagged (odd) units must still be collected"
+        );
+        for s in &samples {
+            assert!(
+                aacs_unit_encrypted(s),
+                "only CPI-flagged units are selected"
+            );
+            assert_eq!(
+                s[0] & 0xC0,
+                0xC0,
+                "a CPI-clear sync-destroyed unit must never be sampled"
+            );
         }
     }
 
@@ -725,7 +819,7 @@ mod tests {
     /// prior single-key fixtures passed regardless of stride.
     #[test]
     fn disc_inputs_ctx_parses_unit_keys_at_the_version_stride() {
-        use crate::aacs::{AACS_MAJOR_BD, AACS_MAJOR_UHD};
+        use crate::aacs::mkb::{AACS_MAJOR_BD, AACS_MAJOR_UHD};
         const UK_POS: usize = 64;
         let mut inf = vec![0u8; 200];
         inf[0..4].copy_from_slice(&(UK_POS as u32).to_be_bytes()); // uk_pos

src/labels/criterion.rs

@@ -16,7 +16,7 @@ use std::collections::HashMap;
 
 /// Cheap signature check: a Criterion disc ships `streamproperties.xml`
 /// inside a `/BDMV/JAR/*` archive.
-pub fn detect(udf: &UdfFs) -> bool {
+pub fn detect(_reader: &mut dyn SectorSource, udf: &UdfFs) -> bool {
     super::jar_file_exists(udf, "streamproperties.xml")
 }
 
@@ -77,11 +77,18 @@ pub fn parse(reader: &mut dyn SectorSource, udf: &UdfFs) -> Option<ParseResult>
 /// `apply_labels` matches on `(type, stream_number)`, so a collision
 /// would mislabel tracks.)
 fn assign_stream_numbers(infos: &[StreamInfo], stream_map: &HashMap<String, u16>) -> Vec<u16> {
-    // Numbers already claimed by the map, per type.
+    // Numbers already claimed by the map, per type. A map value of 0 is NOT a
+    // claim: apply_labels binds on 1-based stream numbers, so 0 is unmatchable.
+    // Treat 0 as "unmapped" here (defense in depth — parse_playback_config also
+    // filters it) so such a stream gets a real synthesized number instead of an
+    // orphan 0 that collides with / shadows a genuine stream 1.
     let mut taken_audio: Vec<u16> = Vec::new();
     let mut taken_sub: Vec<u16> = Vec::new();
     for info in infos {
         if let Some(&n) = stream_map.get(&info.id) {
+            if n == 0 {
+                continue;
+            }
             match info.stream_type {
                 StreamLabelType::Audio => taken_audio.push(n),
                 StreamLabelType::Subtitle => taken_sub.push(n),
@@ -94,8 +101,8 @@ fn assign_stream_numbers(infos: &[StreamInfo], stream_map: &HashMap<String, u16>
     let mut out = Vec::with_capacity(infos.len());
     for info in infos {
         let n = match stream_map.get(&info.id).copied() {
-            Some(n) => n,
-            None => {
+            Some(n) if n != 0 => n,
+            _ => {
                 let (idx, taken) = match info.stream_type {
                     StreamLabelType::Audio => (&mut audio_idx, &taken_audio),
                     StreamLabelType::Subtitle => (&mut sub_idx, &taken_sub),
@@ -277,27 +284,34 @@ mod tests {
         assert_eq!(nums[3], 2); // subtitle 2
     }
 
-    /// Spec: map stream_num=0 is explicitly rejected (apply_labels uses 1-based).
-    /// This is documented in parse_playback_config: `if stream_num != 0`.
-    /// Mutation: remove the `!= 0` guard → zero is stored in map.
+    /// Spec: a map value of 0 is unmatchable (apply_labels is 1-based), so
+    /// assign_stream_numbers must treat it as unmapped and synthesize a real
+    /// 1-based number rather than emit an orphan 0.
+    /// Mutation: read the map value verbatim → stream_number 0 leaks out.
     #[test]
-    fn map_zero_stream_num_is_skipped() {
-        // parse_playback_config skips zero; simulate that: the zero shouldn't
-        // end up in the map. We test assign_stream_numbers with a zero-containing
-        // map to verify it won't freeze the fallback counter at 1 forever.
+    fn map_zero_stream_num_is_synthesized_not_emitted() {
         let mut map = HashMap::new();
-        map.insert("a0".to_string(), 0u16); // zero — per spec, was filtered by parse_playback_config
+        map.insert("a0".to_string(), 0u16); // 0 must not be treated as a claim
         let infos = vec![info("a0", StreamLabelType::Audio)];
-        // If 0 IS in the map and assign_stream_numbers uses it, stream_number=0
-        // is not matchable (apply_labels is 1-based). The fallback counter
-        // would assign 1 instead. Test both paths:
         let nums = assign_stream_numbers(&infos, &map);
-        // If the map has 0 for a0, assign_stream_numbers returns 0 (map wins).
-        // This is a known limitation — the guard lives in parse_playback_config.
-        // The test documents the ACTUAL behavior so a code change that introduces
-        // the guard in assign_stream_numbers would be caught.
-        // Current behavior: map wins → 0.
-        assert_eq!(nums[0], 0);
+        // 0 is treated as unmapped → the fallback counter assigns 1.
+        assert_eq!(nums[0], 1);
+    }
+
+    /// A stream genuinely mapped to 1 plus another stream whose map value is 0
+    /// must NOT both land on 1: the 0-stream is synthesized past the claimed 1.
+    #[test]
+    fn map_zero_does_not_collide_with_a_real_stream_one() {
+        let mut map = HashMap::new();
+        map.insert("real".to_string(), 1u16);
+        map.insert("bad".to_string(), 0u16);
+        let infos = vec![
+            info("real", StreamLabelType::Audio),
+            info("bad", StreamLabelType::Audio),
+        ];
+        let nums = assign_stream_numbers(&infos, &map);
+        assert_eq!(nums[0], 1); // the genuinely-mapped stream keeps 1
+        assert_eq!(nums[1], 2); // the 0-stream is synthesized to the next free slot
     }
 
     /// Spec: collision-avoidance works across audio AND subtitle independently.

src/labels/ctrm.rs

@@ -11,7 +11,7 @@ use std::collections::HashMap;
 
 /// Cheap signature check: a CTRM disc ships `menu_base.prop` and/or
 /// `language_streams.txt` inside a `/BDMV/JAR/*` archive.
-pub fn detect(udf: &UdfFs) -> bool {
+pub fn detect(_reader: &mut dyn SectorSource, udf: &UdfFs) -> bool {
     super::jar_file_exists(udf, "menu_base.prop")
         || super::jar_file_exists(udf, "language_streams.txt")
 }

src/labels/dbp.rs

@@ -35,14 +35,16 @@ use crate::sector::SectorSource;
 use crate::udf::UdfFs;
 use std::collections::BTreeMap;
 
-/// dbp detect can't peek inside a jar without a SectorSource (the
-/// trait function only takes `&UdfFs`), so we trigger on the cheap
-/// signal "any top-level .jar in /BDMV/JAR/." That fires on every
-/// BD-J disc, but parse() does the real `com/dbp/` check and
-/// returns None on a mismatch — so this parser only ever consumes
-/// time on discs that fell through every earlier parser.
-pub fn detect(udf: &UdfFs) -> bool {
-    jar::has_any_top_level_jar(udf)
+/// The real dbp signal is the `com/dbp/` package prefix inside a top-level
+/// jar's central directory. With a reader in `detect`, we check that directly
+/// (a cheap central-directory scan, no class decode) so this parser claims
+/// only dbp discs instead of firing on every BD-J disc. `parse()` repeats the
+/// check as belt-and-suspenders.
+pub fn detect(reader: &mut dyn SectorSource, udf: &UdfFs) -> bool {
+    jar::for_each_jar(reader, udf, |_entry, archive| {
+        jar::has_path_prefix(archive, "com/dbp/").then_some(())
+    })
+    .is_some()
 }
 
 /// Scan every top-level `/BDMV/JAR/*.jar` for the dbp framework and

src/labels/deluxe.rs

@@ -64,11 +64,15 @@ use crate::sector::SectorSource;
 use crate::udf::UdfFs;
 use std::collections::{HashMap, HashSet};
 
-pub fn detect(udf: &UdfFs) -> bool {
-    // Cheap pre-check at the dir level; the real signal is
-    // `com/bydeluxe/` inside any top-level jar's central directory,
-    // which `parse()` confirms when given a `SectorSource`.
-    jar::has_any_top_level_jar(udf)
+pub fn detect(reader: &mut dyn SectorSource, udf: &UdfFs) -> bool {
+    // The real signal is `com/bydeluxe/` inside a top-level jar's central
+    // directory. With a reader in detect we check it directly (cheap
+    // central-directory scan, no bytecode walk) so this parser claims only
+    // Deluxe discs; `parse()` repeats the check.
+    jar::for_each_jar(reader, udf, |_entry, archive| {
+        jar::has_path_prefix(archive, "com/bydeluxe/").then_some(())
+    })
+    .is_some()
 }
 
 pub fn parse(reader: &mut dyn SectorSource, udf: &UdfFs) -> Option<ParseResult> {

src/labels/jar.rs

@@ -26,21 +26,6 @@ const MAX_CLASS_BYTES: u64 = 64 * 1024 * 1024;
 /// etc.
 pub type Jar = ZipArchive<Cursor<Vec<u8>>>;
 
-/// True if `/BDMV/JAR/` contains at least one top-level `.jar` file
-/// (not under a subdir). Used by `detect()` in parsers whose real
-/// signal lives inside a jar — they can't open the jar without a
-/// `SectorSource`, so they use this cheap pre-check and do the real
-/// `com/<vendor>/` discriminator in `parse()`.
-pub fn has_any_top_level_jar(udf: &UdfFs) -> bool {
-    let Some(jar_dir) = udf.find_dir("/BDMV/JAR") else {
-        return false;
-    };
-    jar_dir
-        .entries
-        .iter()
-        .any(|e| !e.is_dir && e.name.to_lowercase().ends_with(".jar"))
-}
-
 /// Open every top-level `*.jar` entry in `/BDMV/JAR/` and yield each
 /// `(entry_name, Jar)` to `f`. Returns the first `Some(R)` the callback
 /// produces, or `None` if every jar was visited without a hit.

src/labels/mod.rs

@@ -20,6 +20,7 @@ pub(crate) mod jar;
 mod mpls_universal;
 mod paramount;
 mod pixelogic;
+mod png_filenames;
 pub(crate) mod text;
 pub mod vocab;
 pub(crate) mod xml;
@@ -91,7 +92,11 @@ pub enum LabelQualifier {
 // the registry picks the highest-confidence parse result, falling back
 // to array order on confidence ties.
 
-type DetectFn = fn(&UdfFs) -> bool;
+// `detect` takes the reader too, so a parser can look INSIDE a jar's central
+// directory (real vendor-prefix / project-file check) rather than firing on
+// "any jar present". Precise detection is what lets the registry scale to many
+// parsers without cross-parser collisions.
+type DetectFn = fn(&mut dyn SectorSource, &UdfFs) -> bool;
 type ParseFn = fn(&mut dyn SectorSource, &UdfFs) -> Option<ParseResult>;
 
 /// Per-parser claim of how reliable its output is. Used by the
@@ -158,11 +163,11 @@ const PARSERS: &[(&str, DetectFn, ParseFn)] = &[
     ("criterion", criterion::detect, criterion::parse),
     ("pixelogic", pixelogic::detect, pixelogic::parse),
     ("ctrm", ctrm::detect, ctrm::parse),
-    // dbp and deluxe both detect on "any top-level .jar in /BDMV/JAR/"
-    // (every BD-J disc trips that) and do the real vendor-prefix check
-    // in parse(). Order between them is the tiebreaker on equal
-    // confidence; dbp goes first because its parse path is cheaper
-    // (constant-pool iteration vs. deluxe's bytecode walking).
+    // dbp and deluxe now detect via the real `com/<vendor>/` central-directory
+    // prefix (reader-backed), so they claim only their own discs. Order between
+    // them is the tiebreaker on equal confidence; dbp goes first because its
+    // parse path is cheaper (constant-pool iteration vs. deluxe's bytecode
+    // walking).
     ("dbp", dbp::detect, dbp::parse),
     ("deluxe", deluxe::detect, deluxe::parse),
     // Universal MPLS fallback. Returns Confidence::Low so framework
@@ -176,6 +181,11 @@ const PARSERS: &[(&str, DetectFn, ParseFn)] = &[
         mpls_universal::detect,
         mpls_universal::parse,
     ),
+    // Menu-graphic filename language hints (Low). AFTER mpls_universal so the
+    // richer spec-derived floor wins the Low tie whenever it produces anything;
+    // this only becomes the chosen parser when even MPLS yields nothing but the
+    // menu artwork still names its languages. A last-resort language source.
+    ("png_filenames", png_filenames::detect, png_filenames::parse),
 ];
 
 /// Search disc for config files, extract labels, apply to streams.
@@ -521,7 +531,7 @@ fn generate_audio_label_inner(
 fn extract(reader: &mut dyn SectorSource, udf: &UdfFs) -> Vec<StreamLabel> {
     let mut best: Option<(&'static str, ParseResult)> = None;
     for (name, detect, parse) in PARSERS {
-        if !detect(udf) {
+        if !detect(reader, udf) {
             continue;
         }
         tracing::info!(parser = name, "label parser detected");
@@ -788,7 +798,7 @@ pub fn analyze(reader: &mut dyn SectorSource, udf: &UdfFs) -> LabelAnalysis {
     let mut all_results: Vec<(&'static str, ParseResult)> = Vec::new();
 
     for (name, detect, parse) in PARSERS {
-        if !detect(udf) {
+        if !detect(reader, udf) {
             continue;
         }
         tracing::info!(parser = name, "label parser detected");
@@ -961,8 +971,9 @@ pub struct ChapterSummary {
 
 /// List filenames found under any `/BDMV/JAR/<x>/` subdirectory of
 /// the disc. Deduped, sorted. Returns an empty vec if no JAR dir is
-/// present.
-fn jar_inventory(udf: &UdfFs) -> Vec<String> {
+/// present. `pub(crate)` so filename-based parsers (e.g. `png_filenames`)
+/// can scan menu-asset names without a reader.
+pub(crate) fn jar_inventory(udf: &UdfFs) -> Vec<String> {
     let Some(jar_dir) = udf.find_dir("/BDMV/JAR") else {
         return Vec::new();
     };
@@ -1042,12 +1053,14 @@ mod registry_tests {
                 "dbp",
                 "deluxe",
                 "mpls_universal",
+                "png_filenames",
             ],
-            "PARSERS array order changed — confirm dbp + deluxe stay just \
-             before mpls_universal (loose detect, real check in parse), \
-             stricter parsers (paramount/criterion/pixelogic/ctrm — all \
-             file-presence gated detect) stay first, and mpls_universal \
-             stays LAST as the universal Low-confidence fallback."
+            "PARSERS array order changed — file-presence/reader-gated High \
+             parsers (paramount/criterion/pixelogic/ctrm) stay first; dbp + \
+             deluxe (now real com/<vendor>/ prefix detect) stay before \
+             mpls_universal; mpls_universal stays the universal Low fallback; \
+             png_filenames (Low, language-only hint) stays LAST so MPLS wins \
+             the Low tie whenever it produces anything."
         );
     }
 

src/labels/mpls_universal.rs

@@ -29,7 +29,7 @@ use crate::udf::UdfFs;
 
 /// True iff `/BDMV/PLAYLIST/` exists and contains at least one
 /// `.mpls` file. Cheap directory walk only — no sector reads.
-pub fn detect(udf: &UdfFs) -> bool {
+pub fn detect(_reader: &mut dyn SectorSource, udf: &UdfFs) -> bool {
     let Some(dir) = udf.find_dir("/BDMV/PLAYLIST") else {
         return false;
     };

src/labels/paramount.rs

@@ -16,7 +16,7 @@ use super::{LabelPurpose, LabelQualifier, ParseResult, StreamLabel, StreamLabelT
 use crate::sector::SectorSource;
 use crate::udf::UdfFs;
 
-pub fn detect(udf: &UdfFs) -> bool {
+pub fn detect(_reader: &mut dyn SectorSource, udf: &UdfFs) -> bool {
     super::jar_file_exists(udf, "playlists.xml")
 }
 

src/labels/pixelogic.rs

@@ -25,7 +25,7 @@ const REGIONS: &[&str] = &[
     "US", "UK", "CF", "PF", "CS", "LS", "BP", "PP", "SM", "TM", "CAN", "DUM", "FLE",
 ];
 
-pub fn detect(udf: &UdfFs) -> bool {
+pub fn detect(_reader: &mut dyn SectorSource, udf: &UdfFs) -> bool {
     super::jar_file_exists(udf, "bluray_project.bin")
 }
 

src/labels/png_filenames.rs

@@ -0,0 +1,149 @@
+//! Menu-graphic filename language hints.
+//!
+//! Some BD-J discs encode per-language menu artwork with the language in the
+//! filename, e.g. `Dune_UHD01_Eng_Composite1.png`,
+//! `VForVendetta_UHD01_FRE_Composite2.png`. The `_UHD01_{LANG}_Composite`
+//! marker is authored deliberately, so the set of `{LANG}` tokens is the set
+//! of menu languages the disc ships.
+//!
+//! This is a language-only hint (no per-stream purpose/codec), so it runs at
+//! [`Confidence::Low`] — it never displaces a real framework parser, and it
+//! sits at the same tier as the MPLS floor. It is here so the pattern is a
+//! first-class, testable parser that keeps picking up discs as the corpus
+//! grows, rather than lost logic. Detection is precise: it fires only on the
+//! `_UHD01_{LANG}_Composite` grammar with a `{LANG}` the vocab recognizes.
+
+use super::{LabelPurpose, LabelQualifier, ParseResult, StreamLabel, StreamLabelType, vocab};
+use crate::sector::SectorSource;
+use crate::udf::UdfFs;
+
+pub fn detect(_reader: &mut dyn SectorSource, udf: &UdfFs) -> bool {
+    super::jar_inventory(udf)
+        .iter()
+        .any(|f| filename_lang(f).is_some())
+}
+
+pub fn parse(_reader: &mut dyn SectorSource, udf: &UdfFs) -> Option<ParseResult> {
+    let names = super::jar_inventory(udf);
+    let labels = labels_from_filenames(&names);
+    if labels.is_empty() {
+        return None;
+    }
+    // Low: language-only, derived from menu-asset filenames. A real framework
+    // parser (and even the MPLS floor's per-stream data) is preferred; this is
+    // a hint of which languages the disc menus offer.
+    Some(ParseResult::low(labels))
+}
+
+/// One audio [`StreamLabel`] per distinct menu language found, in first-seen
+/// order, numbered 1-based. Split out from `parse` so it is unit-testable
+/// without a `UdfFs`.
+fn labels_from_filenames(names: &[String]) -> Vec<StreamLabel> {
+    let mut seen: Vec<&'static str> = Vec::new();
+    for name in names {
+        if let Some(code) = filename_lang(name) {
+            if !seen.contains(&code) {
+                seen.push(code);
+            }
+        }
+    }
+    seen.into_iter()
+        .enumerate()
+        .map(|(i, code)| StreamLabel {
+            stream_number: (i as u16).saturating_add(1),
+            stream_type: StreamLabelType::Audio,
+            language: code.to_string(),
+            name: String::new(),
+            purpose: LabelPurpose::Normal,
+            qualifier: LabelQualifier::None,
+            codec_hint: String::new(),
+            variant: String::new(),
+        })
+        .collect()
+}
+
+/// Extract the ISO-639-2 language code from a `{title}_UHD01_{LANG}_Composite`
+/// menu-graphic filename, or `None` if the name does not match the grammar or
+/// carries a `{LANG}` the vocab does not recognize.
+///
+/// The `_UHD01_` marker plus the `_Composite` suffix keep this from firing on
+/// unrelated PNGs (`KeyComposite4.png`, `LoadingComposite1.png` have no
+/// `_UHD01_{LANG}_` segment).
+fn filename_lang(name: &str) -> Option<&'static str> {
+    // Case-fold once; the marker/suffix are matched case-insensitively.
+    let lower = name.to_ascii_lowercase();
+    let marker = "_uhd01_";
+    let m = lower.find(marker)?;
+    let after = m + marker.len();
+    // The language token runs from `after` up to the next `_`.
+    let rest = &lower[after..];
+    let end = rest.find('_')?;
+    if !rest[end..].starts_with("_composite") {
+        return None;
+    }
+    let token = &name[after..after + end];
+    vocab::menu_lang(token)
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn extracts_confirmed_samples() {
+        assert_eq!(filename_lang("Dune_UHD01_Eng_Composite1.png"), Some("eng"));
+        assert_eq!(filename_lang("Dune_UHD01_Ger_Composite2.png"), Some("deu"));
+        assert_eq!(
+            filename_lang("VForVendetta_UHD01_FRE_Composite2.png"),
+            Some("fra")
+        );
+    }
+
+    #[test]
+    fn ignores_non_language_composites() {
+        assert_eq!(filename_lang("KeyComposite4.png"), None);
+        assert_eq!(filename_lang("LoadingComposite1.png"), None);
+        assert_eq!(
+            filename_lang("FourKWarningsComposite1_bt2020_HDR.png"),
+            None
+        );
+        assert_eq!(filename_lang("Fast9_UPK75_Composite1.png"), None);
+    }
+
+    #[test]
+    fn unknown_language_token_is_none() {
+        // A UHD01 marker but a token the vocab does not recognize must not
+        // produce a bogus language.
+        assert_eq!(filename_lang("Movie_UHD01_Zzz_Composite1.png"), None);
+    }
+
+    #[test]
+    fn dedups_and_numbers_distinct_languages() {
+        let names = vec![
+            "Dune_UHD01_Eng_Composite1.png".to_string(),
+            "Dune_UHD01_Eng_Composite2.png".to_string(),
+            "Dune_UHD01_Ger_Composite1.png".to_string(),
+            "LoadingComposite1.png".to_string(),
+        ];
+        let labels = labels_from_filenames(&names);
+        assert_eq!(labels.len(), 2);
+        assert_eq!(labels[0].language, "eng");
+        assert_eq!(labels[0].stream_number, 1);
+        assert_eq!(labels[1].language, "deu");
+        assert_eq!(labels[1].stream_number, 2);
+        assert!(
+            labels
+                .iter()
+                .all(|l| l.stream_type == StreamLabelType::Audio)
+        );
+    }
+
+    #[test]
+    fn no_matching_names_yields_empty() {
+        let names = vec![
+            "KeyComposite4.png".to_string(),
+            "disc.properties".to_string(),
+        ];
+        assert!(labels_from_filenames(&names).is_empty());
+    }
+}

src/labels/vocab.rs

@@ -176,6 +176,49 @@ const BARE_LANGS: &[(&str, &str)] = &[
     ("galician", "glg"),
 ];
 
+/// Map a short menu-graphic language token (as embedded in authoring
+/// filenames like `Dune_UHD01_Eng_Composite1.png`) to an ISO-639-2/T code.
+///
+/// These filename tokens are compact 2/3-letter abbreviations, NOT the full
+/// language names [`lang`] handles, so they get their own certain table.
+/// Accepts the ISO-639-2/B spellings some tools emit (`ger`, `fre`, `chi`)
+/// and normalizes them to the /T code the rest of the pipeline uses (`deu`,
+/// `fra`, `zho`). Case-insensitive. Returns `None` for anything not in the
+/// table — never guesses, so an unrecognized token drops rather than
+/// mislabels.
+pub fn menu_lang(token: &str) -> Option<&'static str> {
+    let t = token.trim().to_ascii_lowercase();
+    let code = match t.as_str() {
+        "eng" | "en" => "eng",
+        "ger" | "deu" | "de" => "deu",
+        "fre" | "fra" | "fr" => "fra",
+        "spa" | "es" => "spa",
+        "ita" | "it" => "ita",
+        "por" | "pt" => "por",
+        "jpn" | "jap" | "ja" => "jpn",
+        "kor" | "ko" => "kor",
+        "chi" | "zho" | "zh" => "zho",
+        "rus" | "ru" => "rus",
+        "dut" | "nld" | "nl" => "nld",
+        "pol" | "pl" => "pol",
+        "cze" | "ces" | "cs" => "ces",
+        "dan" | "da" => "dan",
+        "fin" | "fi" => "fin",
+        "nor" | "no" => "nor",
+        "swe" | "sv" => "swe",
+        "hun" | "hu" => "hun",
+        "gre" | "ell" | "el" => "ell",
+        "tur" | "tr" => "tur",
+        "ara" | "ar" => "ara",
+        "hin" | "hi" => "hin",
+        "tha" | "th" => "tha",
+        "ukr" | "uk" => "ukr",
+        "cat" | "ca" => "cat",
+        _ => return None,
+    };
+    Some(code)
+}
+
 // ── Purpose ──────────────────────────────────────────────────────────────────
 
 /// Classify a free-form English label string into a [`LabelPurpose`].

src/mux/au_assembly.rs

@@ -0,0 +1,844 @@
+//! Access-unit assembly — a codec-parser helper.
+//!
+//! The contract a codec parser converts is `PES → access units (Frames)`. A
+//! *transport* stream hands the parser one AU per PES for free (BD aligns one
+//! access unit per PES; the TS demuxer reassembles to the
+//! `payload_unit_start_indicator`). A *program* stream does not — the PS muxer
+//! chops the elementary stream into fixed-size PES fragments with no AU
+//! alignment, and only the first fragment of an AU carries a PTS. So a parser
+//! that assumes one-AU-per-PES (h264/hevc/vc1, written against TS) mis-frames a
+//! program stream, while `mpeg2` — the DVD/PS codec — must reassemble across PES.
+//!
+//! [`AuAssembler`] is that reassembly, factored out so EVERY program-stream video
+//! parser shares one implementation instead of hand-rolling the buffer. The
+//! h264/hevc/vc1 parsers ([`Mode::StartCode`] / [`Mode::Vc1`]) and the MPEG-2
+//! parser ([`Mode::Mpeg2`], via [`AuAssembler::mpeg2`]) all drive it. It buffers
+//! PES-fragment bytes and emits one AU per codec AU boundary, carrying the
+//! AU-start timing/source forward. Since the boundary is a codec start code, it
+//! lives with the codec parser (which picks the marker); only the generic
+//! buffering + timing-carry is shared here.
+//!
+//! This is *inside* the parser, not a pipeline stage: the pipeline stays
+//! `Demuxer → PES → Parser → Frames`, and the demuxer stays codec-agnostic. Every
+//! stream a parser sees runs through one of these — self-framing codecs (MPEG-2,
+//! audio) use [`Mode::Passthrough`] so the parser code path is uniform.
+
+use crate::disc::Codec;
+use crate::pes::SourcePos;
+use std::collections::VecDeque;
+
+/// Safety cap on a single in-progress access unit. A real coded picture is far
+/// below this; a stream that never yields a second AU boundary is force-flushed
+/// at the cap rather than buffering without bound on hostile/corrupt input.
+const MAX_AU_BUFFER: usize = 8 * 1024 * 1024;
+
+/// Cap on buffered timing/discontinuity marks. A real access unit spans a few
+/// hundred PES fragments at most; this bounds the mark deques so a run of
+/// zero-length (or start-code-free) timed fragments — which grow no buffer bytes
+/// and so never trip the `MAX_AU_BUFFER` mark-prune — cannot accumulate marks
+/// without bound on hostile/corrupt disc input.
+const MAX_MARKS: usize = 64 * 1024;
+
+/// One AU-complete unit drained from the buffer: its elementary-stream bytes plus
+/// the timing/source/discontinuity of the fragment that opened the AU.
+pub(crate) struct AssembledAu {
+    pub data: Vec<u8>,
+    pub pts: Option<i64>,
+    pub dts: Option<i64>,
+    pub source: Option<SourcePos>,
+    pub discontinuity: bool,
+}
+
+/// VC-1 (SMPTE 421M Annex E) BDU start-code suffixes, `00 00 01 <type>`.
+const VC1_FRAME: u8 = 0x0D; // coded picture
+const VC1_ENTRY: u8 = 0x0E; // entry-point header
+const VC1_SEQ: u8 = 0x0F; // sequence header
+
+/// MPEG-2 (ISO/IEC 13818-2) start-code suffixes, `00 00 01 <type>`.
+const MP2_PICTURE: u8 = 0x00; // picture_start_code
+const MP2_SEQ: u8 = 0xB3; // sequence_header_code
+const MP2_GOP: u8 = 0xB8; // group_start_code
+
+/// How a stream's fragments become AU-complete units.
+#[derive(Clone, Copy)]
+enum Mode {
+    /// Split the elementary stream on the codec's single AU-delimiter start code
+    /// `00 00 01 <marker>` (H.264 AUD `0x09`, HEVC AUD `0x46`). Every AU opens with
+    /// exactly that code, so a plain split is correct.
+    StartCode(u8),
+    /// VC-1 has no single AU delimiter: an access unit is a `[sequence header?]
+    /// [entry point?][frame][slices…]` group. The sequence-header (`0x0F`) and
+    /// entry-point (`0x0E`) BDUs precede the frame (`0x0D`) they belong to, so a
+    /// plain `0x0D` split would glue them onto the *previous* AU and strip every
+    /// I-frame of its headers. The boundary is instead the next `0x0F`/`0x0E`/`0x0D`
+    /// start code that follows a frame already seen in the current AU.
+    Vc1,
+    /// MPEG-2 access unit: `[sequence header?][GOP header?][picture][slices…]`.
+    /// Structurally identical to [`Mode::Vc1`] — the sequence (`0xB3`) and GOP
+    /// (`0xB8`) headers precede the picture (`0x00`) they introduce, so the
+    /// boundary is the next picture / sequence / GOP start code that follows a
+    /// picture already seen. Slice (`0x01..=0xAF`), extension (`0xB5`),
+    /// user-data (`0xB2`) and sequence-end (`0xB7`) codes are NOT boundaries.
+    Mpeg2,
+    /// The codec self-frames (MPEG-2 reassembles in its own parser; audio resyncs
+    /// on syncwords), so each fragment passes straight through as one unit. Lets
+    /// the caller run EVERY stream through an assembler with no per-codec branch.
+    Passthrough,
+}
+
+/// A timing/source mark taken at the absolute stream offset of a fragment that
+/// carried it, so it survives `buf.drain(..)` and can be attributed to the AU
+/// whose byte range contains it.
+struct Mark {
+    off: u64,
+    pts: Option<i64>,
+    dts: Option<i64>,
+    source: Option<SourcePos>,
+}
+
+/// Reassembles PES fragments into AU-complete units. One per stream; stateful
+/// across `push` calls.
+pub(crate) struct AuAssembler {
+    mode: Mode,
+    /// Buffered elementary-stream bytes not yet emitted as a complete AU.
+    buf: Vec<u8>,
+    /// Absolute stream offset of `buf[0]`, so marks (taken at absolute offsets)
+    /// survive `buf.drain(..)`.
+    base: u64,
+    /// Timing/source marks, in fragment order.
+    marks: VecDeque<Mark>,
+    /// Absolute offsets of fragments flagged with an upstream discontinuity.
+    disc_marks: VecDeque<u64>,
+    /// Incremental boundary-scan cursor: the offset into `buf` up to which the
+    /// current AU has already been searched for its end without finding one. Each
+    /// `push` resumes the boundary search from here instead of rescanning the
+    /// whole buffer, so reassembling one AU split across N PES fragments costs
+    /// O(AU bytes) total, not O(AU bytes²/fragment). Reset to 0 whenever `buf[0]`
+    /// moves (an AU drained, or leading bytes dropped).
+    scan_pos: usize,
+    /// Whether the current AU has already contained a coded frame/picture — the
+    /// state the VC-1/MPEG-2 boundary rule carries across a resumed scan (their
+    /// boundary is "the next opener after a frame is already seen"). Meaningless
+    /// for `Mode::StartCode`. Reset with `scan_pos`.
+    seen_unit: bool,
+    /// Pre-sync opener-search cursor: the offset up to which the buffer has been
+    /// searched for the FIRST AU opener with none found. Resumes the opener scan
+    /// so a long run of junk with no start code (hostile/corrupt input) costs
+    /// O(bytes) total, not O(buffer) per push. Reset when `buf[0]` moves.
+    opener_pos: usize,
+}
+
+impl AuAssembler {
+    /// An assembler for `codec`. Video codecs whose parsers assume AU-complete PES
+    /// (H.264 / HEVC / VC-1) get a [`Mode::StartCode`] assembler; MPEG-2 (self-
+    /// reassembles) and audio/subtitle codecs (self-framing) get [`Mode::Passthrough`]
+    /// so callers can run every stream through this uniformly.
+    pub(crate) fn for_codec(codec: Codec) -> Self {
+        let mode = match codec {
+            Codec::H264 => Mode::StartCode(0x09), // access_unit_delimiter NAL (type 9)
+            Codec::Hevc => Mode::StartCode(0x46), // AUD NAL (type 35 → (35 << 1) = 0x46)
+            Codec::Vc1 => Mode::Vc1,              // frame + preceding seq/entry headers
+            _ => Mode::Passthrough,
+        };
+        Self {
+            mode,
+            // Passthrough never writes `buf` (one fragment → one unit); only the
+            // reassembling modes need reserve. Avoids ~256 KiB per audio/subtitle
+            // stream (and every TS/BD stream, which never feeds the assembler).
+            buf: match mode {
+                Mode::Passthrough => Vec::new(),
+                _ => Vec::with_capacity(256 * 1024),
+            },
+            base: 0,
+            marks: VecDeque::new(),
+            disc_marks: VecDeque::new(),
+            scan_pos: 0,
+            seen_unit: false,
+            opener_pos: 0,
+        }
+    }
+
+    /// An assembler that reassembles MPEG-2 access units. The MPEG-2 parser owns
+    /// one of these directly (rather than hand-rolling the buffer): the demux
+    /// layer runs MPEG-2 through [`Mode::Passthrough`] and hands each fragment to
+    /// the parser, which feeds them here to be reframed on picture boundaries.
+    pub(crate) fn mpeg2() -> Self {
+        Self {
+            mode: Mode::Mpeg2,
+            buf: Vec::with_capacity(128 * 1024),
+            base: 0,
+            marks: VecDeque::new(),
+            disc_marks: VecDeque::new(),
+            scan_pos: 0,
+            seen_unit: false,
+            opener_pos: 0,
+        }
+    }
+
+    /// Feed one PES fragment the caller OWNS; return every AU now complete. For
+    /// a self-framing (`Passthrough`) stream the payload is MOVED straight into
+    /// the emitted unit with no copy — the common DVD/HD-DVD case (MPEG-2 video,
+    /// all audio). A buffering mode copies into `buf` exactly as [`Self::push`].
+    pub(crate) fn push_owned(
+        &mut self,
+        data: Vec<u8>,
+        pts: Option<i64>,
+        dts: Option<i64>,
+        source: Option<SourcePos>,
+        discontinuity: bool,
+    ) -> Vec<AssembledAu> {
+        if matches!(self.mode, Mode::Passthrough) {
+            return vec![AssembledAu {
+                data,
+                pts,
+                dts,
+                source,
+                discontinuity,
+            }];
+        }
+        self.push(&data, pts, dts, source, discontinuity)
+    }
+
+    /// Feed one PES fragment (borrowed); return every AU that is now complete.
+    pub(crate) fn push(
+        &mut self,
+        data: &[u8],
+        pts: Option<i64>,
+        dts: Option<i64>,
+        source: Option<SourcePos>,
+        discontinuity: bool,
+    ) -> Vec<AssembledAu> {
+        // Self-framing codecs pass through unchanged — one fragment, one unit,
+        // its own timing. (This is exactly today's behaviour for mpeg2/audio.)
+        if matches!(self.mode, Mode::Passthrough) {
+            return vec![AssembledAu {
+                data: data.to_vec(),
+                pts,
+                dts,
+                source,
+                discontinuity,
+            }];
+        }
+        let off = self.base + self.buf.len() as u64;
+        if pts.is_some() || dts.is_some() || source.is_some() {
+            self.marks.push_back(Mark {
+                off,
+                pts,
+                dts,
+                source,
+            });
+            // Backstop: the `buf`-size cap prunes marks only when bytes accumulate.
+            // A run of zero-length (or start-code-free) timed fragments grows no
+            // bytes, so bound the deque directly — drop the oldest (stalest) mark,
+            // which belongs to an already-emitted or lost AU. A real AU spans far
+            // fewer fragments than this cap.
+            if self.marks.len() > MAX_MARKS {
+                self.marks.pop_front();
+            }
+        }
+        if discontinuity {
+            self.disc_marks.push_back(off);
+            if self.disc_marks.len() > MAX_MARKS {
+                self.disc_marks.pop_front();
+            }
+        }
+        self.buf.extend_from_slice(data);
+        self.drain(false)
+    }
+
+    /// Emit the trailing in-progress AU at end of stream (no following boundary).
+    pub(crate) fn flush(&mut self) -> Vec<AssembledAu> {
+        if matches!(self.mode, Mode::Passthrough) {
+            return Vec::new();
+        }
+        self.drain(true)
+    }
+
+    fn drain(&mut self, force: bool) -> Vec<AssembledAu> {
+        if matches!(self.mode, Mode::Passthrough) {
+            return Vec::new();
+        }
+        let mut out = Vec::new();
+        loop {
+            // Locate the AU start code that opens the buffered run (resumes from
+            // opener_pos so an unsynced junk run is scanned once, not per push).
+            let Some(a0) = self.au_opener_resumable() else {
+                // No AU boundary buffered. Bound memory: drop all but a 3-byte
+                // tail (enough to catch a start-code prefix straddling the cut)
+                // once over the cap; otherwise wait for more data.
+                if self.buf.len() > MAX_AU_BUFFER {
+                    let drop = self.buf.len() - 3;
+                    self.buf.drain(..drop);
+                    self.base += drop as u64;
+                    self.reset_scan();
+                    self.drop_marks_before(self.base);
+                }
+                break;
+            };
+            if a0 > 0 {
+                // Leading bytes before the first AU boundary are a partial AU from
+                // before we synced (or junk) — discard them and any stale marks.
+                self.buf.drain(..a0);
+                self.base += a0 as u64;
+                self.reset_scan();
+                self.drop_marks_before(self.base);
+                continue;
+            }
+            // The AU runs from here (buf[0]) to the NEXT AU boundary. The search
+            // resumes from `scan_pos` (bytes already searched with no boundary),
+            // so one AU spread across many fragments is scanned once, not per push.
+            let end = match self.au_boundary_resumable() {
+                Some(next) => next,
+                // No next boundary yet: on EOF (or over-cap backstop) the rest of
+                // the buffer is this AU; otherwise wait for more data.
+                None if force => self.buf.len(),
+                None if self.buf.len() > MAX_AU_BUFFER => self.buf.len(),
+                None => break,
+            };
+            if end == 0 {
+                break;
+            }
+            let end_abs = self.base + end as u64;
+
+            // The AU's own timing/source: take the FIRST Some of each field
+            // across every mark in this AU's range [base, end_abs), independently
+            // — one PES fragment may carry the source while a later fragment of
+            // the same AU carries the PTS (and vice versa), so reading only the
+            // front mark would drop the other field. This restores the semantics
+            // of the pre-consolidation separate pts/source mark deques.
+            let (mut pts, mut dts, mut source) = (None, None, None);
+            while self.marks.front().is_some_and(|m| m.off < end_abs) {
+                let m = self.marks.pop_front().unwrap();
+                pts = pts.or(m.pts);
+                dts = dts.or(m.dts);
+                source = source.or(m.source);
+            }
+            let mut discontinuity = false;
+            if self.disc_marks.front().is_some_and(|&o| o < end_abs) {
+                discontinuity = true;
+            }
+            while self.disc_marks.front().is_some_and(|&o| o < end_abs) {
+                self.disc_marks.pop_front();
+            }
+
+            let data = self.buf[..end].to_vec();
+            self.buf.drain(..end);
+            self.base += end as u64;
+            self.reset_scan();
+            out.push(AssembledAu {
+                data,
+                pts,
+                dts,
+                source,
+                discontinuity,
+            });
+        }
+        out
+    }
+
+    /// Reset the incremental boundary-scan cursor. Called whenever `buf[0]` moves
+    /// (an AU drained, or leading bytes discarded) so the next scan starts fresh
+    /// from the new AU opener.
+    fn reset_scan(&mut self) {
+        self.scan_pos = 0;
+        self.seen_unit = false;
+        self.opener_pos = 0;
+    }
+
+    /// Locate the first AU opener in `buf`, resuming the search from `opener_pos`
+    /// (bytes already searched with no opener) so a long unsynced run costs
+    /// O(bytes) total, not O(buffer) per push. Advances `opener_pos` on a miss.
+    fn au_opener_resumable(&mut self) -> Option<usize> {
+        match au_opener_from(self.mode, &self.buf, self.opener_pos) {
+            Some(o) => Some(o),
+            None => {
+                // Nothing yet; next call resumes here (back up 3 for a straddling
+                // start-code prefix). Never advance past what is searchable.
+                self.opener_pos = self.buf.len().saturating_sub(3).max(self.opener_pos);
+                None
+            }
+        }
+    }
+
+    /// Find the end of the AU that opens at `buf[0]`, resuming from `scan_pos`
+    /// (and, for VC-1/MPEG-2, the carried `seen_unit`) instead of rescanning the
+    /// whole buffer. On no boundary yet, advances `scan_pos`/`seen_unit` so the
+    /// next call continues where this one stopped. Equivalent result to a
+    /// from-scratch whole-buffer scan, but O(total AU bytes) across all pushes.
+    fn au_boundary_resumable(&mut self) -> Option<usize> {
+        match self.mode {
+            Mode::StartCode(marker) => {
+                // Stateless: the AU ends at the next delimiter after the opener at
+                // buf[0]. Resume from the furthest searched offset (never before 4,
+                // to skip the opening delimiter). find_start_code needs 4 bytes, so
+                // back up 3 to catch a code straddling the previous buffer end.
+                let from = self.scan_pos.max(4);
+                match find_start_code(&self.buf, from, marker) {
+                    Some(e) => Some(e),
+                    None => {
+                        self.scan_pos = self.buf.len().saturating_sub(3).max(from);
+                        None
+                    }
+                }
+            }
+            Mode::Vc1 => self.scan_unit_boundary(VC1_FRAME, &[VC1_ENTRY, VC1_SEQ]),
+            Mode::Mpeg2 => self.scan_unit_boundary(MP2_PICTURE, &[MP2_SEQ, MP2_GOP]),
+            Mode::Passthrough => None,
+        }
+    }
+
+    /// Resumable form of the VC-1/MPEG-2 boundary rule: scan from `scan_pos`,
+    /// carrying `seen_unit`; the AU ends at the next `frame` / `header` start code
+    /// once a frame is already seen. Advances `scan_pos`/`seen_unit` when no
+    /// boundary is found so the next push continues, not restarts.
+    fn scan_unit_boundary(&mut self, frame: u8, headers: &[u8]) -> Option<usize> {
+        let buf = &self.buf;
+        let mut i = self.scan_pos;
+        let mut seen = self.seen_unit;
+        while i + 4 <= buf.len() {
+            if buf[i] == 0 && buf[i + 1] == 0 && buf[i + 2] == 1 {
+                let c = buf[i + 3];
+                let is_frame = c == frame;
+                if (is_frame || headers.contains(&c)) && i > 0 && seen {
+                    // The AU ends at the next frame/header once a frame is seen.
+                    return Some(i);
+                }
+                if is_frame {
+                    seen = true;
+                }
+                i += 4;
+            } else {
+                i += 1;
+            }
+        }
+        // No boundary yet. Persist the scan state so the next append resumes here
+        // rather than rescanning from 0 (the i+=4 stride is preserved exactly).
+        self.scan_pos = i;
+        self.seen_unit = seen;
+        None
+    }
+
+    fn drop_marks_before(&mut self, off: u64) {
+        while self.marks.front().is_some_and(|m| m.off < off) {
+            self.marks.pop_front();
+        }
+        while self.disc_marks.front().is_some_and(|&o| o < off) {
+            self.disc_marks.pop_front();
+        }
+    }
+}
+
+/// Offset of the start code that opens the next AU in `buf` (at or after 0), or
+/// `None` if no AU-opening start code is buffered yet.
+fn au_opener_from(mode: Mode, buf: &[u8], from: usize) -> Option<usize> {
+    match mode {
+        Mode::StartCode(marker) => find_start_code(buf, from, marker),
+        // Any of the three AU-opening BDU types opens a VC-1 access unit.
+        Mode::Vc1 => find_vc1_start(buf, from),
+        // A sequence header, GOP header, or picture opens an MPEG-2 access unit.
+        Mode::Mpeg2 => find_mpeg2_start(buf, from),
+        Mode::Passthrough => None,
+    }
+}
+
+/// Find the next `00 00 01 <marker>` start code at or after `from`.
+fn find_start_code(buf: &[u8], from: usize, marker: u8) -> Option<usize> {
+    let mut i = from;
+    while i + 4 <= buf.len() {
+        if buf[i] == 0 && buf[i + 1] == 0 && buf[i + 2] == 1 && buf[i + 3] == marker {
+            return Some(i);
+        }
+        i += 1;
+    }
+    None
+}
+
+/// Find the next VC-1 AU-opening BDU start code (`00 00 01` followed by a
+/// sequence header, entry point, or frame) at or after `from`.
+fn find_vc1_start(buf: &[u8], from: usize) -> Option<usize> {
+    let mut i = from;
+    while i + 4 <= buf.len() {
+        if buf[i] == 0
+            && buf[i + 1] == 0
+            && buf[i + 2] == 1
+            && matches!(buf[i + 3], VC1_FRAME | VC1_ENTRY | VC1_SEQ)
+        {
+            return Some(i);
+        }
+        i += 1;
+    }
+    None
+}
+
+/// Find the next MPEG-2 AU-opening start code (`00 00 01` followed by a picture,
+/// sequence header, or GOP header) at or after `from`.
+fn find_mpeg2_start(buf: &[u8], from: usize) -> Option<usize> {
+    let mut i = from;
+    while i + 4 <= buf.len() {
+        if buf[i] == 0
+            && buf[i + 1] == 0
+            && buf[i + 2] == 1
+            && matches!(buf[i + 3], MP2_PICTURE | MP2_SEQ | MP2_GOP)
+        {
+            return Some(i);
+        }
+        i += 1;
+    }
+    None
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    const AUD: &[u8] = &[0x00, 0x00, 0x01, 0x09]; // H.264 access-unit delimiter
+
+    fn au(payload: u8, len: usize) -> Vec<u8> {
+        let mut v = AUD.to_vec();
+        v.extend(std::iter::repeat_n(payload, len));
+        v
+    }
+
+    #[test]
+    fn self_framing_codecs_pass_through_each_fragment_unchanged() {
+        // MPEG-2 (self-reassembles in its parser) and audio (syncword resync) run
+        // through a Passthrough assembler: every fragment emerges immediately as
+        // one unit with its own timing — byte-identical to today's path.
+        for codec in [Codec::Mpeg2, Codec::Ac3Plus, Codec::Dts, Codec::Lpcm] {
+            let mut a = AuAssembler::for_codec(codec);
+            let out = a.push(&[1, 2, 3, 4], Some(42), None, None, false);
+            assert_eq!(
+                out.len(),
+                1,
+                "{codec:?} passes each fragment straight through"
+            );
+            assert_eq!(out[0].data, vec![1, 2, 3, 4]);
+            assert_eq!(out[0].pts, Some(42));
+            assert!(a.flush().is_empty(), "passthrough buffers nothing");
+        }
+    }
+
+    #[test]
+    fn video_codecs_reassemble_across_fragments() {
+        // H.264 buffers: one fragment is NOT a complete AU on its own.
+        let mut a = AuAssembler::for_codec(Codec::H264);
+        assert!(
+            a.push(&[0, 0, 1, 0x09, 0xAB], Some(1), None, None, false)
+                .is_empty(),
+            "holds an AU until the next boundary"
+        );
+    }
+
+    #[test]
+    fn one_au_split_across_fragments_reassembles_with_start_pts() {
+        // A single AU (AUD + 100 bytes) arrives as three fragments; only the
+        // first carries a PTS. It must emit exactly ONE AU with that PTS.
+        let mut a = AuAssembler::for_codec(Codec::H264);
+        let full = au(0xAB, 100);
+        assert!(
+            a.push(&full[..40], Some(9000), None, None, false)
+                .is_empty()
+        );
+        assert!(a.push(&full[40..80], None, None, None, false).is_empty());
+        assert!(a.push(&full[80..], None, None, None, false).is_empty());
+        let out = a.flush();
+        assert_eq!(out.len(), 1);
+        assert_eq!(
+            out[0].pts,
+            Some(9000),
+            "AU carries its START pts, not 0/None"
+        );
+        assert_eq!(out[0].data, full);
+    }
+
+    #[test]
+    fn two_aus_emit_when_the_second_boundary_arrives() {
+        let mut a = AuAssembler::for_codec(Codec::H264);
+        let au1 = au(0x11, 50);
+        let au2 = au(0x22, 60);
+        let mut buf = au1.clone();
+        buf.extend_from_slice(&au2);
+        // AU1 + AU2's opening AUD → AU1 completes, tagged pts1.
+        let out = a.push(&buf[..au1.len() + 4], Some(1000), None, None, false);
+        assert_eq!(out.len(), 1);
+        assert_eq!(out[0].data, au1);
+        assert_eq!(out[0].pts, Some(1000));
+        a.push(&buf[au1.len() + 4..], None, None, None, false);
+        let out2 = a.flush();
+        assert_eq!(out2.len(), 1);
+        assert_eq!(out2[0].data, au2);
+    }
+
+    #[test]
+    fn au_merges_pts_and_source_from_different_fragments() {
+        // One fragment of an AU may carry the source stamp while a later fragment
+        // of the SAME AU carries the PTS (each PES gets a source; only the anchor
+        // gets a PTS). The AU must keep BOTH — reading only the front mark would
+        // drop whichever field the first fragment lacked.
+        let src = crate::pes::SourcePos::at_byte(4242);
+        let mut a = AuAssembler::for_codec(Codec::H264);
+        let full = au(0xAB, 80);
+        // Fragment 1: source only, no PTS.
+        assert!(a.push(&full[..30], None, None, Some(src), false).is_empty());
+        // Fragment 2 (same AU): PTS only, no source.
+        assert!(
+            a.push(&full[30..], Some(9000), None, None, false)
+                .is_empty()
+        );
+        let out = a.flush();
+        assert_eq!(out.len(), 1);
+        assert_eq!(out[0].pts, Some(9000), "PTS from the 2nd fragment retained");
+        assert_eq!(
+            out[0].source.map(|s| s.byte),
+            Some(4242),
+            "source from the 1st fragment retained"
+        );
+    }
+
+    #[test]
+    fn discontinuity_flag_attaches_to_the_au_it_opens() {
+        // A discontinuity-flagged fragment opens AU2; that flag must land on AU2,
+        // not AU1 (the B1 resync gate keys off it).
+        let mut a = AuAssembler::for_codec(Codec::H264);
+        let au1 = au(0x11, 30);
+        let au2 = au(0x22, 30);
+        a.push(&au1, Some(1), None, None, false);
+        // AU2 arrives flagged; its opening AUD completes AU1 first.
+        let out = a.push(&au2, Some(2), None, None, true);
+        assert_eq!(out.len(), 1, "AU1 completes when AU2's boundary arrives");
+        assert!(!out[0].discontinuity, "AU1 is NOT the discontinuity");
+        let out2 = a.flush();
+        assert_eq!(out2.len(), 1);
+        assert!(out2[0].discontinuity, "AU2 carries the discontinuity");
+    }
+
+    #[test]
+    fn leading_bytes_before_first_au_are_discarded() {
+        let mut a = AuAssembler::for_codec(Codec::H264);
+        let mut buf = vec![0xFF, 0xFF, 0xFF, 0xFF];
+        buf.extend_from_slice(&au(0x33, 20));
+        a.push(&buf, Some(500), None, None, false);
+        let out = a.flush();
+        assert_eq!(out.len(), 1);
+        assert_eq!(out[0].data, au(0x33, 20), "leading junk dropped, AU intact");
+    }
+
+    // ── VC-1 AU grouping ──────────────────────────────────────────────────
+
+    fn bdu(ty: u8, payload: u8, len: usize) -> Vec<u8> {
+        let mut v = vec![0x00, 0x00, 0x01, ty];
+        v.extend(std::iter::repeat_n(payload, len));
+        v
+    }
+
+    #[test]
+    fn vc1_i_frame_keeps_its_preceding_seq_and_entry_headers() {
+        // An I-frame AU is [seq 0x0F][entry 0x0E][frame 0x0D][slices]; a following
+        // P-frame is just [frame 0x0D][slices]. A plain 0x0D split would strand the
+        // seq/entry headers on the P-frame's AU — the decode bug. The VC-1 mode must
+        // group them with the I-frame that follows them.
+        let mut a = AuAssembler::for_codec(Codec::Vc1);
+        let mut iframe = bdu(VC1_SEQ, 0xAA, 8);
+        iframe.extend(bdu(VC1_ENTRY, 0xBB, 6));
+        iframe.extend(bdu(VC1_FRAME, 0xCC, 20)); // frame + slice bytes
+        let pframe = bdu(VC1_FRAME, 0xDD, 15);
+
+        // Feed the I-frame; it stays open until the P-frame's boundary arrives.
+        assert!(a.push(&iframe, Some(9000), None, None, false).is_empty());
+        let out = a.push(&pframe, Some(9376), None, None, false);
+        assert_eq!(out.len(), 1, "I-frame AU completes at the P-frame boundary");
+        assert_eq!(out[0].data, iframe, "I-frame AU retains seq+entry+frame");
+        assert_eq!(out[0].pts, Some(9000));
+
+        let tail = a.flush();
+        assert_eq!(tail.len(), 1);
+        assert_eq!(tail[0].data, pframe, "P-frame is its own AU");
+        assert_eq!(tail[0].pts, Some(9376));
+    }
+
+    #[test]
+    fn vc1_consecutive_frames_split_one_per_au() {
+        // Back-to-back frames with no headers between them each form their own AU.
+        let mut a = AuAssembler::for_codec(Codec::Vc1);
+        let f1 = bdu(VC1_FRAME, 0x11, 30);
+        let f2 = bdu(VC1_FRAME, 0x22, 40);
+        let mut both = f1.clone();
+        both.extend_from_slice(&f2);
+        both.extend(bdu(VC1_FRAME, 0x33, 4)); // opening boundary of a 3rd frame
+        let out = a.push(&both, Some(1), None, None, false);
+        assert_eq!(out.len(), 2, "two complete frames emit");
+        assert_eq!(out[0].data, f1);
+        assert_eq!(out[1].data, f2);
+    }
+
+    #[test]
+    fn vc1_entry_point_without_seq_header_still_groups_with_frame() {
+        // Mid-GOP open points can carry an entry-point header with no sequence
+        // header; it must still attach to the frame that follows it.
+        let mut a = AuAssembler::for_codec(Codec::Vc1);
+        let mut au = bdu(VC1_ENTRY, 0xEE, 5);
+        au.extend(bdu(VC1_FRAME, 0xFF, 12));
+        let mut done = a.push(&au, Some(500), None, None, false);
+        // Next frame's opening boundary closes the entry+frame AU.
+        done.extend(a.push(&bdu(VC1_FRAME, 0x00, 4), None, None, None, false));
+        done.extend(a.flush());
+        assert_eq!(done.len(), 2);
+        assert_eq!(done[0].data, au, "entry+frame grouped");
+        assert_eq!(done[0].pts, Some(500));
+    }
+
+    // ── MPEG-2 AU grouping ────────────────────────────────────────────────
+
+    #[test]
+    fn mpeg2_keeps_seq_and_gop_headers_with_their_picture() {
+        // A GOP-opening AU is [seq 0xB3][gop 0xB8][picture 0x00][slices]; the next
+        // picture (no headers) is its own AU. The seq/GOP headers must stay with
+        // the picture they introduce, not glue onto the previous AU.
+        let mut a = AuAssembler::mpeg2();
+        let mut gop = bdu(MP2_SEQ, 0xAA, 10);
+        gop.extend(bdu(MP2_GOP, 0xBB, 8));
+        gop.extend(bdu(MP2_PICTURE, 0xCC, 20)); // picture + slice bytes
+        let pic2 = bdu(MP2_PICTURE, 0xDD, 15);
+
+        assert!(a.push(&gop, Some(9000), None, None, false).is_empty());
+        let out = a.push(&pic2, Some(9376), None, None, false);
+        assert_eq!(
+            out.len(),
+            1,
+            "first AU completes at the next picture boundary"
+        );
+        assert_eq!(out[0].data, gop, "AU retains seq + GOP + picture");
+        assert_eq!(out[0].pts, Some(9000));
+
+        let tail = a.flush();
+        assert_eq!(tail.len(), 1);
+        assert_eq!(tail[0].data, pic2, "second picture is its own AU");
+        assert_eq!(tail[0].pts, Some(9376));
+    }
+
+    #[test]
+    fn mpeg2_slice_codes_are_not_au_boundaries() {
+        // Slice start codes (0x01..=0xAF) inside a picture must not split the AU.
+        let mut a = AuAssembler::mpeg2();
+        let mut pic = bdu(MP2_PICTURE, 0x11, 4);
+        pic.extend(bdu(0x01, 0x22, 10)); // slice 1
+        pic.extend(bdu(0xAF, 0x33, 10)); // slice 175 (max slice code)
+        let next = bdu(MP2_PICTURE, 0x44, 4); // opening boundary of the next AU
+        let out = a.push(&[pic.clone(), next].concat(), Some(1), None, None, false);
+        assert_eq!(out.len(), 1, "slices stay inside the one picture AU");
+        assert_eq!(out[0].data, pic, "AU spans the picture and all its slices");
+    }
+
+    #[test]
+    fn mpeg2_reassembles_one_picture_split_across_fragments() {
+        // A picture split across three PES fragments; only the first carries a PTS.
+        let mut a = AuAssembler::mpeg2();
+        let full = bdu(MP2_PICTURE, 0xEE, 100);
+        assert!(a.push(&full[..40], Some(500), None, None, false).is_empty());
+        assert!(a.push(&full[40..80], None, None, None, false).is_empty());
+        assert!(a.push(&full[80..], None, None, None, false).is_empty());
+        let out = a.flush();
+        assert_eq!(out.len(), 1);
+        assert_eq!(out[0].pts, Some(500), "AU carries its START pts");
+        assert_eq!(out[0].data, full);
+    }
+
+    /// Split `stream` into fragments of `frag` bytes, push them through the given
+    /// assembler mode, and return the reassembled AU byte-payloads.
+    fn reassemble_with(mut a: AuAssembler, stream: &[u8], frag: usize) -> Vec<Vec<u8>> {
+        let mut out = Vec::new();
+        let mut i = 0;
+        while i < stream.len() {
+            let end = (i + frag).min(stream.len());
+            for au in a.push(&stream[i..end], None, None, None, false) {
+                out.push(au.data);
+            }
+            i = end;
+        }
+        for au in a.flush() {
+            out.push(au.data);
+        }
+        out
+    }
+
+    #[test]
+    fn resumable_boundary_matches_from_scratch_across_all_fragmentations() {
+        // The incremental scan_pos cursor must produce byte-identical AUs to a
+        // whole-buffer rescan, at EVERY fragment granularity (this is what makes
+        // the O(n) resume equivalent to the old O(n^2) from-scratch scan). Build a
+        // multi-AU stream per codec, reassemble it fed 1 byte at a time up to
+        // whole, and require one canonical result.
+        let h264 = {
+            let mut s = au(0x11, 40); // AU1 (AUD + payload)
+            s.extend(au(0x22, 70)); // AU2
+            s.extend(au(0x33, 25)); // AU3
+            s
+        };
+        let vc1 = {
+            let mut s = bdu(VC1_SEQ, 0xAA, 8);
+            s.extend(bdu(VC1_ENTRY, 0xBB, 6));
+            s.extend(bdu(VC1_FRAME, 0xCC, 50)); // I-frame AU
+            s.extend(bdu(VC1_FRAME, 0xDD, 30)); // P-frame AU
+            s.extend(bdu(VC1_FRAME, 0xEE, 20)); // P-frame AU
+            s
+        };
+        let mpeg2 = {
+            let mut s = bdu(MP2_SEQ, 0xAA, 10);
+            s.extend(bdu(MP2_GOP, 0xBB, 8));
+            s.extend(bdu(MP2_PICTURE, 0xCC, 60)); // GOP-opening picture AU
+            s.extend(bdu(MP2_PICTURE, 0xDD, 40)); // picture AU
+            s
+        };
+        // (label, stream, assembler factory). MPEG-2 uses the dedicated mpeg2()
+        // assembler (Mode::Mpeg2); the AUD/VC-1 codecs use for_codec().
+        type MakeAsm = fn() -> AuAssembler;
+        let cases: [(&str, &[u8], MakeAsm); 3] = [
+            ("h264", &h264, || AuAssembler::for_codec(Codec::H264)),
+            ("vc1", &vc1, || AuAssembler::for_codec(Codec::Vc1)),
+            ("mpeg2", &mpeg2, AuAssembler::mpeg2),
+        ];
+        for (label, stream, make) in cases {
+            let whole = reassemble_with(make(), stream, stream.len());
+            assert!(!whole.is_empty(), "{label}: baseline produced AUs");
+            for frag in 1..=stream.len() {
+                let got = reassemble_with(make(), stream, frag);
+                assert_eq!(
+                    got, whole,
+                    "{label}: fragmented at {frag} differs from whole-buffer reassembly"
+                );
+            }
+        }
+    }
+
+    #[test]
+    fn marks_deques_stay_bounded_on_zero_length_timed_fragments() {
+        // A run of zero-length fragments that each carry a PTS (or a
+        // discontinuity) grows no buffer bytes, so the buf-size cap never prunes
+        // the mark deques. The MAX_MARKS backstop must bound them regardless.
+        let mut a = AuAssembler::for_codec(Codec::H264);
+        for i in 0..(MAX_MARKS * 2) {
+            a.push(&[], Some(i as i64), None, None, true);
+        }
+        assert!(
+            a.marks.len() <= MAX_MARKS,
+            "marks bounded at MAX_MARKS, got {}",
+            a.marks.len()
+        );
+        assert!(
+            a.disc_marks.len() <= MAX_MARKS,
+            "disc_marks bounded at MAX_MARKS, got {}",
+            a.disc_marks.len()
+        );
+    }
+
+    #[test]
+    fn over_cap_without_boundary_force_flushes() {
+        let mut a = AuAssembler::for_codec(Codec::H264);
+        let big = au(0x44, MAX_AU_BUFFER + 16);
+        let emitted = a.push(&big, Some(1), None, None, false);
+        assert!(
+            !emitted.is_empty(),
+            "over-cap AU is force-flushed, not buffered forever"
+        );
+    }
+}

src/mux/codec/dts.rs

@@ -37,7 +37,7 @@ pub struct DtsParser {
     /// timestamp instead of the later PES's. Offsets are kept relative to the
     /// current `buf` start and rebased whenever bytes are drained from the
     /// front.
-    pts_marks: Vec<(usize, i64)>,
+    pts_marks: std::collections::VecDeque<(usize, i64)>,
     /// The `front_pts` of the PREVIOUS emitted access unit. When the current
     /// AU's `front_pts` differs, it began a new PES → re-base to it. When it is
     /// unchanged, this AU shares the previous AU's PES → advance one frame
@@ -62,7 +62,7 @@ impl DtsParser {
         Self {
             buf: Vec::with_capacity(32768),
             pending_pts: 0,
-            pts_marks: Vec::new(),
+            pts_marks: std::collections::VecDeque::new(),
             last_front_pts: PTS_UNSET,
             next_pts_ns: PTS_UNSET,
         }
@@ -194,7 +194,7 @@ impl CodecParser for DtsParser {
         // discontinuity-carrying PES is a PUSI with a PTS in practice.
         let pts_ns = pes.pts.map(pts_to_ns).unwrap_or_else(|| {
             self.pts_marks
-                .last()
+                .back()
                 .map(|&(_, p)| p)
                 .filter(|&p| p >= 0)
                 .unwrap_or(if self.pending_pts >= 0 {
@@ -230,7 +230,10 @@ impl CodecParser for DtsParser {
         // (see `front_pts`), so an AU whose core arrived in an earlier PES keeps
         // that core's timestamp even when its extensions / the following core
         // arrive (with a later PTS) in this same parse() call.
-        self.pts_marks.push((self.buf.len(), pts_ns));
+        // (pts_marks is bounded implicitly: an empty PES returns above without
+        // pushing a mark, and a non-empty run grows `buf`, which is cleared —
+        // along with pts_marks — once it exceeds MAX_AU_BYTES.)
+        self.pts_marks.push_back((self.buf.len(), pts_ns));
         self.buf.extend_from_slice(&pes.data);
 
         let mut frames = Vec::new();
@@ -915,6 +918,37 @@ mod tests {
         assert_eq!(dts_core_sample_rate(&core), 48_000);
     }
 
+    #[test]
+    fn dts_core_sfreq_table_matches_the_dca_spec() {
+        // Lock the SFREQ → sample-rate table to ffmpeg's authoritative
+        // `avpriv_dca_sample_rates` (ETSI TS 102 114 Table 6-4). The high-rate
+        // triad in particular — 48 k / 96 k / 192 k at indices 13/14/15 — must not
+        // be shifted; a wrong entry would compute an N× frame duration and
+        // reintroduce PTS drift on a 96/192 kHz DTS stream.
+        let mut core = make_dts_core(512);
+        let set_sfreq = |c: &mut [u8], idx: u8| c[8] = (c[8] & !0x3C) | ((idx & 0x0F) << 2);
+        for (idx, want) in [
+            (1u8, 8_000u32),
+            (2, 16_000),
+            (3, 32_000),
+            (6, 11_025),
+            (7, 22_050),
+            (8, 44_100),
+            (11, 12_000),
+            (12, 24_000),
+            (13, 48_000),
+            (14, 96_000),
+            (15, 192_000),
+        ] {
+            set_sfreq(&mut core, idx);
+            assert_eq!(
+                dts_core_sample_rate(&core),
+                want,
+                "SFREQ {idx} must be {want} Hz"
+            );
+        }
+    }
+
     #[test]
     fn new_pes_rebases_to_its_own_pts_no_drift() {
         // Regression for the drift bug: a global running clock overshot a
@@ -922,6 +956,14 @@ mod tests {
         // PES arrives whose PTS is BEHIND where accumulated frame durations
         // would put a running clock, the AU must re-base to that PES's OWN
         // timestamp — tracking the container, not drifting ahead of it.
+        //
+        // The re-base can make one emitted PTS sit just below the previous AU's
+        // (a fresh PES whose PTS lands under the within-PES cursor). That is
+        // CORRECT here and is NOT a muxer defect: the parser reports the true
+        // container timestamps, and the mkv muxer applies the strictly-monotonic
+        // per-track nudge to AUDIO at emit time (`mkv::block_ts` / `monotonic_ts`,
+        // tested in `mkv.rs`), so the written block DTS is always monotonic. The
+        // alternative — clamping in the parser — is what reintroduced the drift.
         let mut parser = DtsParser::new();
         // PES A: core1 + core2 (2 frames), pts 90000.
         let mut pes_a = make_dts_core(512);

src/mux/codec/h264.rs

@@ -52,6 +52,17 @@ pub struct H264Parser {
     // the stale avcC copy after a mid-title redefinition.
     cur_sps: Option<Vec<u8>>,
     cur_pps: Option<Vec<u8>>,
+    /// Display-order PTS reconstruction, enabled only on the program-stream
+    /// (HD-DVD EVO) path where the source stamps a PTS once per GOP. `None` on
+    /// the BD/UHD transport path, which carries a per-frame PTS.
+    reorder: Option<super::reorder::SparsePtsReorder>,
+    /// MVC dependent-view (Blu-ray 3D right-eye) passthrough mode. When set, the
+    /// parser does NOT strip SPS/PPS (nor re-assert at keyframes): every NAL —
+    /// subset SPS (type 15), prefix (14), coded-slice-extension (20), PPS (8) —
+    /// is length-prefixed in-band, so each emitted frame is a self-contained
+    /// dependent access unit suitable for a Matroska `BlockAdditional`. The base
+    /// view's avcC/param-set stripping is unchanged (separate parser instance).
+    mvc_passthrough: bool,
 }
 
 impl Default for H264Parser {
@@ -68,6 +79,35 @@ impl H264Parser {
             pps: None,
             cur_sps: None,
             cur_pps: None,
+            reorder: None,
+            mvc_passthrough: false,
+        }
+    }
+
+    /// Enable display-order PTS reconstruction for a program-stream source.
+    /// No-op (leaves timestamps as parsed) for a transport-stream source.
+    pub(crate) fn with_ps_reorder(mut self, enabled: bool) -> Self {
+        if enabled {
+            self.reorder = Some(super::reorder::SparsePtsReorder::new());
+        }
+        self
+    }
+
+    /// Enable MVC dependent-view passthrough (see the `mvc_passthrough` field):
+    /// keep every parameter set in-band so each frame is a self-contained
+    /// dependent access unit for a Matroska `BlockAdditional`. Used only for the
+    /// Blu-ray 3D dependent (right-eye) stream.
+    pub(crate) fn with_mvc_passthrough(mut self, enabled: bool) -> Self {
+        self.mvc_passthrough = enabled;
+        self
+    }
+
+    /// Route a finished frame through the PTS reorderer when enabled, else emit
+    /// it directly (unchanged transport-stream behaviour).
+    fn finish(&mut self, explicit: Option<i64>, frame: Frame) -> Vec<Frame> {
+        match self.reorder.as_mut() {
+            Some(r) => r.push(explicit, frame),
+            None => vec![frame],
         }
     }
 }
@@ -152,7 +192,8 @@ impl CodecParser for H264Parser {
         // decode order and the player reorders by timecode. Use PTS, not DTS —
         // DTS presents B-frames in decode order (visible judder) and breaks
         // PTS-based seeking. Fall back to DTS only if PTS is absent.
-        let pts_ns = pes.pts.or(pes.dts).map(pts_to_ns).unwrap_or(0);
+        let explicit_pts = pes.pts.or(pes.dts).map(pts_to_ns);
+        let pts_ns = explicit_pts.unwrap_or(0);
 
         // Single pass: detect IDR keyframes, seed/strip param sets, and convert
         // Annex B (start-code prefixed) NALUs to length-prefixed NALUs (MKV with
@@ -168,17 +209,23 @@ impl CodecParser for H264Parser {
         // frame in the mux hot path (mirrors the HEVC parser).
         let mut frame_data = Vec::with_capacity(pes.data.len() + 64);
 
+        // MVC dependent-view passthrough: keep ALL param sets in-band (the frame
+        // is a self-contained BlockAdditional access unit), never strip/re-assert.
+        let mvc = self.mvc_passthrough;
+
         for nal in NalIterator::new(&pes.data) {
             let nal_type = nal[0] & 0x1F;
 
             match nal_type {
                 // Param sets: seed avcC, strip if unchanged vs the active set,
                 // emit in-band on any change (incl. reverting to the avcC copy).
-                NAL_SPS => {
+                // In MVC passthrough these fall through to the default arm so the
+                // subset SPS / PPS stay in-band (self-contained dependent AU).
+                NAL_SPS if !mvc => {
                     emitted_sps |=
                         handle_param_set(&mut self.sps, &mut self.cur_sps, nal, &mut frame_data)
                 }
-                NAL_PPS => {
+                NAL_PPS if !mvc => {
                     emitted_pps |=
                         handle_param_set(&mut self.pps, &mut self.cur_pps, nal, &mut frame_data)
                 }
@@ -226,7 +273,7 @@ impl CodecParser for H264Parser {
         // ahead of the slices (even when unchanged vs codecPrivate) so a decoder
         // that dropped the set at a reset recovers, and a stale avcC re-apply
         // can't revert it. Skipped per-type only when this AU already carried it.
-        if keyframe {
+        if keyframe && !mvc {
             let mut prefix = Vec::new();
             reassert_active(&mut prefix, &self.cur_sps, emitted_sps);
             reassert_active(&mut prefix, &self.cur_pps, emitted_pps);
@@ -236,7 +283,7 @@ impl CodecParser for H264Parser {
             }
         }
 
-        vec![Frame {
+        let frame = Frame {
             // Coding-type only: H.264 field order is not decoded here, so
             // `field_order()` stays `None` — honestly absent, never guessed.
             coding: coding_type.map(PictureInfo::coding_type_only),
@@ -248,7 +295,15 @@ impl CodecParser for H264Parser {
             discontinuity: pes.discontinuity,
             data: frame_data,
             duration_ns: None,
-        }]
+        };
+        self.finish(explicit_pts, frame)
+    }
+
+    fn flush(&mut self) -> Vec<Frame> {
+        match self.reorder.as_mut() {
+            Some(r) => r.flush(),
+            None => Vec::new(),
+        }
     }
 
     fn codec_private(&self) -> Option<Vec<u8>> {
@@ -619,6 +674,94 @@ mod tests {
         v
     }
 
+    #[test]
+    fn mvc_passthrough_keeps_param_sets_inband() {
+        // A dependent-view access unit: subset SPS (NAL 15) + PPS (NAL 8) +
+        // coded-slice-extension (NAL 20). No IDR (type 5), so keyframe stays
+        // false and there is no keyframe re-assertion.
+        let au = || {
+            let mut d = Vec::new();
+            d.extend_from_slice(&h264_nal(0x6F, &[0x80, 0x00, 0x33, 0xAA])); // subset SPS (15)
+            d.extend_from_slice(&h264_nal(0x68, &[0xCE, 0x01])); // PPS (8)
+            d.extend_from_slice(&h264_nal(0x74, &[0x11, 0x22])); // slice-ext (20)
+            d
+        };
+        let nal_types =
+            |f: &Frame| -> Vec<u8> { h264_nals_in(&f.data).iter().map(|n| n[0] & 0x1F).collect() };
+
+        // Normal parser strips the PPS from a non-keyframe AU (it is captured for
+        // the avcC and, without an IDR, never re-asserted in-band).
+        let mut normal = H264Parser::new();
+        let f = normal.parse(&make_pes(au(), Some(90000)));
+        assert_eq!(f.len(), 1);
+        assert!(
+            !nal_types(&f[0]).contains(&8),
+            "normal parser strips PPS from a non-keyframe AU: {:?}",
+            nal_types(&f[0])
+        );
+
+        // Passthrough keeps EVERY parameter set in-band, so each dependent frame
+        // is a self-contained access unit for a BlockAdditional.
+        let mut pt = H264Parser::new().with_mvc_passthrough(true);
+        let f = pt.parse(&make_pes(au(), Some(90000)));
+        assert_eq!(f.len(), 1);
+        let types = nal_types(&f[0]);
+        assert!(types.contains(&15), "subset SPS kept in-band: {types:?}");
+        assert!(
+            types.contains(&8),
+            "PPS kept in-band under passthrough: {types:?}"
+        );
+        assert!(types.contains(&20), "slice kept: {types:?}");
+    }
+
+    #[test]
+    fn parser_for_mvc_dependent_h264_is_passthrough() {
+        // The dependent-view stream must get a passthrough parser: a PPS in a
+        // non-keyframe AU is kept in-band, not stripped like the base parser.
+        let mut p = crate::mux::codec::parser_for_mvc_dependent(crate::disc::Codec::H264, false);
+        let mut d = Vec::new();
+        d.extend_from_slice(&h264_nal(0x68, &[0xCE, 0x01])); // PPS (8)
+        d.extend_from_slice(&h264_nal(0x74, &[0x11, 0x22])); // slice-ext (20)
+        let f = p.parse(&make_pes(d, Some(90000)));
+        assert_eq!(f.len(), 1);
+        let types: Vec<u8> = h264_nals_in(&f[0].data)
+            .iter()
+            .map(|n| n[0] & 0x1F)
+            .collect();
+        assert!(
+            types.contains(&8),
+            "dependent parser keeps PPS in-band (passthrough): {types:?}"
+        );
+    }
+
+    #[test]
+    fn mvc_passthrough_with_idr_does_not_reassert_param_sets() {
+        // With an IDR present (keyframe=true), passthrough must NOT re-assert the
+        // param sets (the `keyframe && !mvc` guard), so SPS/PPS appear exactly
+        // once — a duplicate would corrupt the dependent BlockAdditional.
+        let mut p = H264Parser::new().with_mvc_passthrough(true);
+        let mut d = Vec::new();
+        d.extend_from_slice(&h264_nal(0x67, &[0x42, 0x00, 0x1E, 0x01])); // SPS (7)
+        d.extend_from_slice(&h264_nal(0x68, &[0xCE, 0x01])); // PPS (8)
+        d.extend_from_slice(&h264_nal(0x65, &[0x88, 0x00])); // IDR slice (5)
+        let f = p.parse(&make_pes(d, Some(90000)));
+        assert_eq!(f.len(), 1);
+        let types: Vec<u8> = h264_nals_in(&f[0].data)
+            .iter()
+            .map(|n| n[0] & 0x1F)
+            .collect();
+        assert_eq!(
+            types.iter().filter(|&&t| t == 7).count(),
+            1,
+            "exactly one SPS, no keyframe re-assert under passthrough: {types:?}"
+        );
+        assert_eq!(
+            types.iter().filter(|&&t| t == 8).count(),
+            1,
+            "exactly one PPS, no keyframe re-assert under passthrough: {types:?}"
+        );
+    }
+
     #[test]
     fn h264_populates_measured_coding_type_and_source() {
         use super::super::coding::CodingType;
@@ -667,6 +810,71 @@ mod tests {
         );
     }
 
+    /// End-to-end sparse-PTS reconstruction through the REAL parser + reorder:
+    /// a program-stream source (`with_ps_reorder(true)`) that stamps a PTS only
+    /// on each GOP's I-frame must yield distinct, display-ordered PTS for every
+    /// frame — the property the mkv muxer needs so a decoder derives monotonic
+    /// DTS. Without the reorder the non-anchor frames all collapse to one PTS.
+    #[test]
+    fn h264_ps_reorder_reconstructs_distinct_display_pts() {
+        use super::super::coding::CodingType;
+        // slice bodies: 0x88 → I (IDR), 0x98 → P, 0x9C → B (non-IDR).
+        // Decode order of a classic single-B GOP: I P B P B.
+        let gop = |anchor_pts: Option<i64>| {
+            vec![
+                (NAL_SLICE_IDR, 0x88u8, anchor_pts),
+                (NAL_SLICE_NON_IDR, 0x98, None),
+                (NAL_SLICE_NON_IDR, 0x9C, None),
+                (NAL_SLICE_NON_IDR, 0x98, None),
+                (NAL_SLICE_NON_IDR, 0x9C, None),
+            ]
+        };
+
+        let feed = |reorder: bool| -> Vec<super::super::Frame> {
+            let mut p = H264Parser::new().with_ps_reorder(reorder);
+            let mut out = Vec::new();
+            // Two GOPs; the second I carries an anchor 5 frames later (90 kHz:
+            // 5 * 3750 = 18750 ticks) so the reorder can calibrate a duration.
+            for (nal, body, pts) in gop(Some(0)).into_iter().chain(gop(Some(18750))) {
+                out.extend(p.parse(&make_pes(h264_nal(nal, &[body]), pts)));
+            }
+            out.extend(p.flush());
+            out
+        };
+
+        // With reorder ON: all 10 frames emitted, every PTS distinct.
+        let recon = feed(true);
+        assert_eq!(recon.len(), 10, "no frame dropped");
+        let mut pts: Vec<i64> = recon.iter().map(|f| f.pts_ns).collect();
+        let n = pts.len();
+        pts.sort_unstable();
+        pts.dedup();
+        assert_eq!(
+            pts.len(),
+            n,
+            "reconstructed PTS are all distinct (no DTS collision)"
+        );
+
+        // The GOP's first-displayed frame is the I; the B in decode position 2
+        // must display BEFORE the P in decode position 1 (classic reorder).
+        let g1 = &recon[0..5];
+        assert_eq!(g1[0].coding.unwrap().coding_type(), CodingType::I);
+        assert!(
+            g1[2].pts_ns < g1[1].pts_ns,
+            "B (decode idx 2) displays before its forward-anchor P (decode idx 1)"
+        );
+        assert_eq!(g1[0].pts_ns, 0, "GOP anchor locks the I to its true PTS");
+
+        // With reorder OFF (transport-stream behaviour): the non-anchor frames
+        // collapse to a single colliding PTS — the bug this fix removes.
+        let raw = feed(false);
+        let collisions = raw.iter().filter(|f| f.pts_ns == 0).count();
+        assert!(
+            collisions >= 8,
+            "without reorder the sparse-PTS frames collide on 0 (got {collisions})"
+        );
+    }
+
     /// Regression (Fight Club bug, H.264 variant): PPS id 0 = body A (→ avcC),
     /// redefined to B, then switched BACK to A. A streaming decoder is on B; the
     /// revert to A == avcC must still be emitted in-band or the A-segment

src/mux/codec/hevc.rs

@@ -166,6 +166,10 @@ pub struct HevcParser {
     // colour-volume metadata is ever fabricated.
     sei_mastering: Option<MasteringDisplay>,
     sei_content_light: Option<ContentLightLevel>,
+    /// Display-order PTS reconstruction, enabled only on the program-stream
+    /// path where the source stamps a PTS once per GOP. `None` on the BD/UHD
+    /// transport path (the common HEVC case), which carries a per-frame PTS.
+    reorder: Option<super::reorder::SparsePtsReorder>,
 }
 
 /// Mastering Display Colour Volume payload (Rec. ITU-T H.265 D.2.28),
@@ -234,6 +238,25 @@ impl HevcParser {
             pts_wrap_offset: 0,
             sei_mastering: None,
             sei_content_light: None,
+            reorder: None,
+        }
+    }
+
+    /// Enable display-order PTS reconstruction for a program-stream source.
+    /// No-op (leaves timestamps as parsed) for a transport-stream source.
+    pub(crate) fn with_ps_reorder(mut self, enabled: bool) -> Self {
+        if enabled {
+            self.reorder = Some(super::reorder::SparsePtsReorder::new());
+        }
+        self
+    }
+
+    /// Route a finished frame through the PTS reorderer when enabled, else emit
+    /// it directly (unchanged transport-stream behaviour).
+    fn finish(&mut self, explicit: Option<i64>, frame: Frame) -> Vec<Frame> {
+        match self.reorder.as_mut() {
+            Some(r) => r.push(explicit, frame),
+            None => vec![frame],
         }
     }
 
@@ -443,7 +466,8 @@ impl CodecParser for HevcParser {
         // block timecode monotonic in storage order, which presents B-frames in
         // decode order (visible judder / wrong frames) and breaks PTS-based
         // seeking. Fall back to DTS only if PTS is somehow absent.
-        let pts_ns = pes.pts.or(pes.dts).map(pts_to_ns).unwrap_or(0);
+        let explicit_pts = pes.pts.or(pes.dts).map(pts_to_ns);
+        let pts_ns = explicit_pts.unwrap_or(0);
 
         // Auto-detect a non-seamless clip boundary from the bitstream. freemkv
         // reads a BD title's clips as ONE concatenated sector stream and the
@@ -651,7 +675,7 @@ impl CodecParser for HevcParser {
         // from the first coded picture before writing the track header). `None`
         // until both SEI present → SDR / no-SEI tracks carry nothing.
         let hdr10 = self.hdr10();
-        vec![Frame {
+        let frame = Frame {
             // Coding-type only: HEVC field order (pic_struct, from a pic_timing
             // SEI) is not decoded here, so field_order() stays None — honestly
             // absent, never guessed. HDR10 metadata is attached when measured.
@@ -666,7 +690,15 @@ impl CodecParser for HevcParser {
             discontinuity: pes.discontinuity,
             data: frame_data,
             duration_ns: None,
-        }]
+        };
+        self.finish(explicit_pts, frame)
+    }
+
+    fn flush(&mut self) -> Vec<Frame> {
+        match self.reorder.as_mut() {
+            Some(r) => r.flush(),
+            None => Vec::new(),
+        }
     }
 
     fn codec_private(&self) -> Option<Vec<u8>> {

src/mux/codec/mod.rs

@@ -25,6 +25,8 @@ pub mod lpcm;
 pub mod mpeg2;
 /// HDMV PGS (Presentation Graphics Stream) subtitle parser.
 pub mod pgs;
+/// Display-order PTS reconstruction for sparse-PTS program-stream video.
+pub(crate) mod reorder;
 /// Shared MPEG/Annex-B start-code scanning helpers.
 pub(crate) mod startcode;
 /// Dolby TrueHD / Atmos elementary-stream parser.
@@ -166,10 +168,14 @@ pub fn parser_for_codec(
     is_dvd_ps: bool,
 ) -> Box<dyn CodecParser> {
     match codec {
-        Codec::H264 => Box::new(h264::H264Parser::new()),
-        Codec::Hevc => Box::new(hevc::HevcParser::new()),
+        // `is_dvd_ps` marks a program-stream source (DVD VOB / HD-DVD EVO), whose
+        // video is timestamped only at GOP granularity. On that path the H.264 /
+        // HEVC / VC-1 parsers reconstruct a display-order PTS per frame; on the
+        // BD/UHD transport path (per-frame PTS) they leave timestamps untouched.
+        Codec::H264 => Box::new(h264::H264Parser::new().with_ps_reorder(is_dvd_ps)),
+        Codec::Hevc => Box::new(hevc::HevcParser::new().with_ps_reorder(is_dvd_ps)),
         Codec::Mpeg2 => Box::new(mpeg2::Mpeg2Parser::new()),
-        Codec::Vc1 => Box::new(vc1::Vc1Parser::new()),
+        Codec::Vc1 => Box::new(vc1::Vc1Parser::new().with_ps_reorder(is_dvd_ps)),
         Codec::Ac3 | Codec::Ac3Plus => Box::new(ac3::Ac3Parser::new()),
         Codec::DtsHdMa | Codec::DtsHdHr | Codec::Dts => Box::new(dts::DtsParser::new()),
         Codec::TrueHd => Box::new(truehd::TrueHdParser::new()),
@@ -201,6 +207,22 @@ pub fn parser_for_codec(
     }
 }
 
+/// Build the codec parser for a Blu-ray 3D **MVC dependent (right-eye)** video
+/// stream. Same codec space as the base view (H.264), but in param-set
+/// passthrough mode so each emitted frame is a self-contained dependent access
+/// unit for a Matroska `BlockAdditional`. Non-H.264 (unexpected) falls back to
+/// the ordinary parser.
+pub fn parser_for_mvc_dependent(codec: Codec, is_dvd_ps: bool) -> Box<dyn CodecParser> {
+    match codec {
+        Codec::H264 => Box::new(
+            h264::H264Parser::new()
+                .with_ps_reorder(is_dvd_ps)
+                .with_mvc_passthrough(true),
+        ),
+        _ => parser_for_codec(codec, None, is_dvd_ps),
+    }
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;

src/mux/codec/mpeg2.rs

@@ -26,13 +26,10 @@
 //! - Extension (seq/pic):00 00 01 B5
 //! - GOP header:         00 00 01 B8
 
-use std::collections::VecDeque;
-
 use super::coding::{CodingType, Mpeg2Coding, PictureInfo};
 use super::startcode::find_start_code;
 use super::{CodecParser, Frame, pts_to_ns};
 use crate::mux::ts::PesPacket;
-use crate::pes::SourcePos;
 
 /// Sequence header start code suffix.
 const SEQ_HEADER_CODE: u8 = 0xB3;
@@ -49,10 +46,10 @@ const PICTURE_CODE: u8 = 0x00;
 /// Picture coding type: I-frame.
 const PICTURE_TYPE_I: u8 = 1;
 
-/// Hard cap on the access-unit reassembly buffer. A real MPEG-2 frame is well
-/// under 1 MiB (DVD I-frames ~100 KB); past this cap a corrupt stream that
-/// never produces a second access-unit boundary is force-flushed as a single
-/// frame rather than driving unbounded allocation.
+/// The access-unit reassembly cap now lives in [`crate::mux::au_assembly`] (the
+/// `AuAssembler` owns cross-PES buffering); this mirror exists only so the
+/// force-flush test below can size an over-cap fixture against the same bound.
+#[cfg(test)]
 const MAX_AU_BUFFER: usize = 8 * 1024 * 1024;
 
 /// Cap on frames held awaiting the first PES PTS anchor. A DVD stamps a PTS in
@@ -94,20 +91,11 @@ pub struct Mpeg2Parser {
     /// Raw bytes of the last seen sequence header (+ sequence extension if
     /// present), captured for MKV codecPrivate.
     seq_header: Option<Vec<u8>>,
-    /// Unemitted elementary-stream bytes: the in-progress access unit plus any
-    /// lookahead needed to detect the next AU boundary.
-    buf: Vec<u8>,
-    /// Absolute ES byte offset of `buf[0]`. Used to associate PES PTS marks
-    /// (recorded by absolute offset) with the access units they belong to.
-    base_offset: u64,
-    /// `(absolute ES offset of a PES's first byte, PTS in ns)` for every PES
-    /// that carried a timestamp, in ascending offset order.
-    pts_marks: VecDeque<(u64, i64)>,
-    /// `(absolute ES offset of a PES's first byte, SourcePos)` for every PES
-    /// that carried byte-exact provenance, parallel to `pts_marks` and drained
-    /// by the SAME mark-drain invariant. Attaches the source position to each
-    /// access unit so the index carries it — never reconstructed.
-    source_marks: VecDeque<(u64, SourcePos)>,
+    /// Reassembles PES fragments into complete access units (one coded picture
+    /// with its leading sequence/GOP headers) and carries each AU's start
+    /// timing / source / discontinuity forward — the shared machinery the
+    /// H.264/HEVC/VC-1 parsers also use, in its MPEG-2 mode.
+    au_asm: crate::mux::au_assembly::AuAssembler,
     /// Full-frame presentation interval (ns) at the sequence-header display rate
     /// (`1/frame_rate`). The field period is half this. Per-frame durations are
     /// `nb_fields × field_period`, so 2:3-telecined frames alternate 2- and
@@ -122,6 +110,10 @@ pub struct Mpeg2Parser {
     /// without ever reordering emitted blocks (B-frames keep decode order; only
     /// their PTS is lower).
     gop_buf: Vec<BufferedPicture>,
+    /// Running total of `data` bytes buffered in `gop_buf` — the byte-cap counter,
+    /// incremented on each push and reset when the GOP flushes. Avoids re-summing
+    /// the whole buffer per picture (which would be O(pictures²)).
+    gop_bytes: usize,
     /// Total field-display periods of all frames already emitted, in display
     /// order — the running base for each new frame's display time.
     emitted_fields: u64,
@@ -129,15 +121,6 @@ pub struct Mpeg2Parser {
     /// each GOP's first PES PTS so video stays in sync with the PES-timestamped
     /// audio. None until the first PES timestamp is seen.
     origin_pts_ns: Option<i64>,
-    /// B1: absolute ES offsets at which a concealed/lost-gap PES began, parallel
-    /// to `pts_marks`/`source_marks` and drained by the SAME mark-drain invariant.
-    /// MPEG-2 emits whole GOPs asynchronously, so a per-PES flag can't ride
-    /// through to the right frame (the PES that carries the gap completes the
-    /// PREVIOUS picture); associating by OFFSET instead stamps `discontinuity` on
-    /// the access unit whose own bytes begin after the gap — the first post-gap
-    /// picture — surviving GOP buffering + temporal reorder. The consumer's
-    /// ResyncGate then arms at that exact picture, mid-GOP if need be.
-    disc_marks: VecDeque<u64>,
 }
 
 /// One coded picture buffered awaiting its GOP's completion (see `gop_buf`).
@@ -165,16 +148,13 @@ impl Mpeg2Parser {
     pub fn new() -> Self {
         Self {
             seq_header: None,
-            buf: Vec::with_capacity(128 * 1024),
-            base_offset: 0,
-            pts_marks: VecDeque::new(),
-            source_marks: VecDeque::new(),
+            au_asm: crate::mux::au_assembly::AuAssembler::mpeg2(),
             frame_duration_ns: 0,
             progressive_sequence: false,
             gop_buf: Vec::new(),
+            gop_bytes: 0,
             emitted_fields: 0,
             origin_pts_ns: None,
-            disc_marks: VecDeque::new(),
         }
     }
 
@@ -199,195 +179,98 @@ impl Mpeg2Parser {
         parse_aspect_ratio(hdr)
     }
 
-    /// Drain every complete access unit from `buf`, returning one Frame each.
-    /// When `force` is true (EOF flush, or buffer-cap backstop) the trailing
-    /// in-progress access unit is emitted even without a following boundary.
-    fn drain_complete_aus(&mut self, force: bool) -> Vec<Frame> {
-        let mut out = Vec::new();
-        loop {
-            // An access unit must contain a coded picture; without one there is
-            // nothing to emit yet (leading sequence/GOP headers wait for it).
-            let Some(pic) = find_code(&self.buf, 0, PICTURE_CODE) else {
-                // No coded picture in an over-cap buffer means we are
-                // accumulating unparseable data (a stream with no picture
-                // start codes). Drop all but a 3-byte tail — enough to catch a
-                // start-code prefix straddling the boundary — and advance the
-                // absolute offset so the PES-mark invariant holds. Mirrors the
-                // post-picture buffer backstop in the AU-boundary search below.
-                if self.buf.len() > MAX_AU_BUFFER {
-                    let drop = self.buf.len() - 3;
-                    self.base_offset += drop as u64;
-                    self.buf.drain(..drop);
-                    let cutoff = self.base_offset;
-                    while let Some(&(off, _)) = self.pts_marks.front() {
-                        if off < cutoff {
-                            self.pts_marks.pop_front();
-                        } else {
-                            break;
-                        }
-                    }
-                    while let Some(&(off, _)) = self.source_marks.front() {
-                        if off < cutoff {
-                            self.source_marks.pop_front();
-                        } else {
-                            break;
-                        }
-                    }
-                    while let Some(&off) = self.disc_marks.front() {
-                        if off < cutoff {
-                            self.disc_marks.pop_front();
-                        } else {
-                            break;
-                        }
-                    }
-                }
-                break;
-            };
-            // The current AU ends where the next one begins: the first
-            // picture / sequence / GOP start code after this picture.
-            let end = match find_au_start(&self.buf, pic + 4) {
-                Some(b) => b,
-                None if force => self.buf.len(),
-                None if self.buf.len() > MAX_AU_BUFFER => self.buf.len(),
-                None => break, // AU not yet complete — await the next boundary
-            };
-            if end == 0 {
-                break;
-            }
-
-            // Phase 1 — read everything from `buf` before any mutation of self
-            // (the slice borrow must end before we touch self fields).
-            let hdr = extract_seq_header(&self.buf[..end]);
-            // A GOP header (0xB8) or a fresh sequence header (0xB3) starts a new
-            // GOP, resetting temporal_reference to 0.
-            let gop_boundary = find_code(&self.buf[..end], 0, GOP_CODE).is_some()
-                || find_code(&self.buf[..end], 0, SEQ_HEADER_CODE).is_some();
-            // picture_coding_type: the full 3-bit value (bits 5-3 of buf[pic+5]).
-            // 0 when the picture header is truncated (no coding type available).
-            let raw_coding_type = if pic + 5 < end {
-                (self.buf[pic + 5] >> 3) & 0x07
-            } else {
-                0
-            };
-            // temporal_reference: the 10 bits immediately after the picture
-            // start code = display order within the GOP.
-            let tr = if pic + 5 < end {
-                (((self.buf[pic + 4] as u64) << 2) | ((self.buf[pic + 5] as u64) >> 6)) & 0x3FF
-            } else {
-                0
-            };
-            let end_abs = self.base_offset + end as u64;
-            let data = self.buf[..end].to_vec();
-
-            // Phase 2 — mutate self.
-            if let Some(h) = hdr {
-                self.progressive_sequence = parse_progressive_sequence(&h);
-                self.seq_header = Some(h);
-                if let Some((num, den)) = self.frame_rate() {
-                    if num > 0 {
-                        self.frame_duration_ns = 1_000_000_000i64 * den as i64 / num as i64;
-                    }
-                }
-            }
-            // Decode the picture coding extension ONCE here and fold every
-            // per-picture datum (coding type + tff/rff/progressive_frame/
-            // frame_picture, plus the sequence's progressive flag) into one
-            // codec-agnostic `PictureInfo`. `nb_fields()`, `keyframe()`, and
-            // `field_order()` all derive from it; nothing downstream re-parses
-            // the elementary stream.
-            let (tff, rff, progressive_frame, frame_picture) = picture_coding_flags(&data);
-            let info = PictureInfo::mpeg2(
-                coding_type_from_raw(raw_coding_type),
-                Mpeg2Coding {
-                    top_field_first: tff,
-                    repeat_first_field: rff,
-                    progressive_frame,
-                    progressive_sequence: self.progressive_sequence,
-                    frame_picture,
-                },
-            );
-            let keyframe = info.keyframe();
-
-            // An explicit PES PTS for this access unit, if any. By the mark-drain
-            // invariant the front mark's offset is >= this AU's start, so a front
-            // mark inside [start, end) is this AU's own timestamp.
-            let explicit = self
-                .pts_marks
-                .front()
-                .filter(|&&(off, _)| off < end_abs)
-                .map(|&(_, p)| p);
-
-            // Byte-exact source provenance for this AU, by the same mark-drain
-            // invariant as the PTS: the front source mark inside [start, end)
-            // belongs to this access unit.
-            let src = self
-                .source_marks
-                .front()
-                .filter(|&&(off, _)| off < end_abs)
-                .map(|&(_, s)| s);
-
-            // A GOP boundary means the buffered run is a COMPLETE GOP (all its
-            // pictures display before the next GOP's), so flush it before
-            // starting the new one. `temporal_reference` resets to 0 at the
-            // boundary, keeping each GOP's display order self-contained.
-            if gop_boundary && !self.gop_buf.is_empty() {
-                self.flush_gop(&mut out);
-            }
-            // A concealed-gap mark inside this AU's range [start, end_abs) means
-            // this picture's own bytes begin after the gap — the first post-gap
-            // AU. Same front-mark invariant as PTS/source. Carries through GOP
-            // buffering/reorder to the ResyncGate (which arms at this picture).
-            let discontinuity = self.disc_marks.front().is_some_and(|&off| off < end_abs);
-            self.gop_buf.push(BufferedPicture {
-                tr,
-                info,
-                explicit_pts: explicit,
-                frame: Frame {
-                    pts_ns: 0,
-                    keyframe,
-                    discontinuity,
-                    data,
-                    duration_ns: None,
-                    coding: Some(info),
-                    source: src,
-                },
-            });
-            // Safety cap: a stream with no GOP/sequence boundaries would buffer
-            // unbounded. Force-flush a pathologically long run as its own GOP.
-            if self.gop_buf.len() >= MAX_PENDING_FRAMES {
-                self.flush_gop(&mut out);
-            }
-            self.buf.drain(..end);
-            self.base_offset = end_abs;
-            // Drop PTS marks fully consumed by the emitted AU; keep the mark at
-            // the boundary (it belongs to the next AU).
-            while let Some(&(off, _)) = self.pts_marks.front() {
-                if off < end_abs {
-                    self.pts_marks.pop_front();
-                } else {
-                    break;
-                }
-            }
-            while let Some(&(off, _)) = self.source_marks.front() {
-                if off < end_abs {
-                    self.source_marks.pop_front();
-                } else {
-                    break;
-                }
-            }
-            while let Some(&off) = self.disc_marks.front() {
-                if off < end_abs {
-                    self.disc_marks.pop_front();
-                } else {
-                    break;
+    /// Process one reassembled access unit (from [`AuAssembler`]): decode its
+    /// per-picture coding info, capture a new sequence header, and buffer the
+    /// picture into the current GOP for display-order timestamping. The AU's
+    /// timing / source / discontinuity were already attributed by the assembler.
+    fn process_au(&mut self, au: crate::mux::au_assembly::AssembledAu, out: &mut Vec<Frame>) {
+        let data = au.data;
+        // An access unit must contain a coded picture; a fragment that assembled
+        // without one (only headers, or truncated at EOF) yields nothing.
+        let Some(pic) = find_code(&data, 0, PICTURE_CODE) else {
+            return;
+        };
+        let end = data.len();
+        // Capture a sequence header for codecPrivate; a new one replaces the
+        // stored value and re-locks the frame duration.
+        if let Some(h) = extract_seq_header(&data) {
+            self.progressive_sequence = parse_progressive_sequence(&h);
+            self.seq_header = Some(h);
+            if let Some((num, den)) = self.frame_rate() {
+                if num > 0 {
+                    self.frame_duration_ns = 1_000_000_000i64 * den as i64 / num as i64;
                 }
             }
         }
-        // EOF: emit the final (possibly incomplete) GOP so nothing is dropped.
-        if force {
-            self.flush_gop(&mut out);
+        // A GOP header (0xB8) or a fresh sequence header (0xB3) starts a new GOP,
+        // resetting temporal_reference to 0.
+        let gop_boundary = find_code(&data, 0, GOP_CODE).is_some()
+            || find_code(&data, 0, SEQ_HEADER_CODE).is_some();
+        // picture_coding_type: the full 3-bit value (bits 5-3 of data[pic+5]).
+        // 0 when the picture header is truncated (no coding type available).
+        let raw_coding_type = if pic + 5 < end {
+            (data[pic + 5] >> 3) & 0x07
+        } else {
+            0
+        };
+        // temporal_reference: the 10 bits immediately after the picture start
+        // code = display order within the GOP.
+        let tr = if pic + 5 < end {
+            (((data[pic + 4] as u64) << 2) | ((data[pic + 5] as u64) >> 6)) & 0x3FF
+        } else {
+            0
+        };
+        // Decode the picture coding extension ONCE here and fold every
+        // per-picture datum (coding type + tff/rff/progressive_frame/
+        // frame_picture, plus the sequence's progressive flag) into one
+        // codec-agnostic `PictureInfo`. `nb_fields()`, `keyframe()`, and
+        // `field_order()` all derive from it; nothing downstream re-parses the
+        // elementary stream.
+        let (tff, rff, progressive_frame, frame_picture) = picture_coding_flags(&data);
+        let info = PictureInfo::mpeg2(
+            coding_type_from_raw(raw_coding_type),
+            Mpeg2Coding {
+                top_field_first: tff,
+                repeat_first_field: rff,
+                progressive_frame,
+                progressive_sequence: self.progressive_sequence,
+                frame_picture,
+            },
+        );
+        let keyframe = info.keyframe();
+
+        // A GOP boundary means the buffered run is a COMPLETE GOP (all its
+        // pictures display before the next GOP's), so flush it before starting
+        // the new one. `temporal_reference` resets to 0 at the boundary, keeping
+        // each GOP's display order self-contained.
+        if gop_boundary && !self.gop_buf.is_empty() {
+            self.flush_gop(out);
+        }
+        self.gop_bytes += data.len();
+        self.gop_buf.push(BufferedPicture {
+            tr,
+            info,
+            explicit_pts: au.pts,
+            frame: Frame {
+                pts_ns: 0,
+                keyframe,
+                // The assembler attributes the concealed-gap flag to the AU whose
+                // own bytes begin after the gap — the first post-gap picture — so
+                // it rides through GOP buffering/reorder to the ResyncGate.
+                discontinuity: au.discontinuity,
+                data,
+                duration_ns: None,
+                coding: Some(info),
+                source: au.source,
+            },
+        });
+        // Safety cap: a stream with no GOP/sequence boundaries would buffer
+        // unbounded. Force-flush a pathologically long run as its own GOP —
+        // bounded by BOTH the frame count and the total buffered bytes, so a
+        // crafted stream of few-but-huge pictures cannot over-allocate either.
+        if self.gop_buf.len() >= MAX_PENDING_FRAMES || self.gop_bytes >= MAX_PENDING_BYTES {
+            self.flush_gop(out);
         }
-        out
     }
 
     /// Emit the buffered GOP. Each frame's PTS is the display-order prefix-sum of
@@ -403,6 +286,8 @@ impl Mpeg2Parser {
         if n == 0 {
             return;
         }
+        // The GOP is fully drained below; reset the running byte counter.
+        self.gop_bytes = 0;
         let field_period = self.frame_duration_ns / 2;
         if field_period <= 0 {
             // No sequence header / frame rate yet (malformed lead-in): emit in
@@ -448,31 +333,31 @@ impl CodecParser for Mpeg2Parser {
         if pes.data.is_empty() {
             return Vec::new();
         }
-        // Record this PES's timestamp against the absolute offset of its first
-        // ES byte, BEFORE appending. MKV block timecodes are presentation
-        // timestamps; prefer PTS (DTS shows B-frames in decode order — judder
-        // and broken seeking), falling back to DTS only when PTS is absent.
-        let off = self.base_offset + self.buf.len() as u64;
-        if let Some(ts) = pes.pts.or(pes.dts) {
-            self.pts_marks.push_back((off, pts_to_ns(ts)));
+        // Feed the fragment to the assembler, which reframes the elementary
+        // stream on picture boundaries and hands back each complete access unit
+        // with its start timing. MKV block timecodes are presentation timestamps;
+        // prefer PTS (DTS shows B-frames in decode order — judder and broken
+        // seeking), falling back to DTS only when PTS is absent.
+        let pts = pes.pts.or(pes.dts).map(pts_to_ns);
+        let aus = self
+            .au_asm
+            .push(&pes.data, pts, None, pes.source, pes.discontinuity);
+        let mut out = Vec::new();
+        for au in aus {
+            self.process_au(au, &mut out);
         }
-        if let Some(src) = pes.source {
-            self.source_marks.push_back((off, src));
-        }
-        // A concealed/lost gap on this PES marks the access unit its bytes begin —
-        // associated by offset (like PTS/source) so it lands on the first post-gap
-        // picture, not the previous one that completes when this PES arrives.
-        if pes.discontinuity {
-            self.disc_marks.push_back(off);
-        }
-        self.buf.extend_from_slice(&pes.data);
-        self.drain_complete_aus(false)
+        out
     }
 
     fn flush(&mut self) -> Vec<Frame> {
-        // drain_complete_aus(true) force-completes the trailing access unit and
-        // flushes the final GOP, so nothing is left buffered at EOF.
-        self.drain_complete_aus(true)
+        // Force-complete the trailing access unit, then flush the final GOP so
+        // nothing is left buffered at EOF.
+        let mut out = Vec::new();
+        for au in self.au_asm.flush() {
+            self.process_au(au, &mut out);
+        }
+        self.flush_gop(&mut out);
+        out
     }
 
     fn codec_private(&self) -> Option<Vec<u8>> {
@@ -518,25 +403,6 @@ fn find_code(data: &[u8], from: usize, want: u8) -> Option<usize> {
     None
 }
 
-/// Find the next access-unit boundary at or after `from`: the position of a
-/// picture (0x00), sequence header (0xB3), or GOP (0xB8) start code. Extension
-/// (0xB5), slice (0x01..=0xAF), user-data (0xB2) and sequence-end (0xB7) codes
-/// belong to the current access unit and are NOT boundaries.
-fn find_au_start(data: &[u8], from: usize) -> Option<usize> {
-    let mut pos = from;
-    while let Some(sc) = find_start_code(data, pos) {
-        if sc + 3 >= data.len() {
-            return None;
-        }
-        let code = data[sc + 3];
-        if code == PICTURE_CODE || code == SEQ_HEADER_CODE || code == GOP_CODE {
-            return Some(sc);
-        }
-        pos = sc + 4;
-    }
-    None
-}
-
 /// Parse horizontal and vertical resolution from sequence header bytes.
 /// The sequence header must start with 00 00 01 B3.
 fn parse_resolution(hdr: &[u8]) -> Option<(u16, u16)> {
@@ -1546,13 +1412,12 @@ mod tests {
         let mut data = make_picture_header(PICTURE_TYPE_I);
         // > MAX_AU_BUFFER of slice bytes with no following picture/seq/GOP.
         data.extend(std::iter::repeat_n(0xAA, MAX_AU_BUFFER + 1024));
-        let frames = parser.parse(&make_pes(data, Some(0)));
-        assert!(
-            frames.is_empty(),
-            "over-cap AU is force-COMPLETED (bounded) but buffered in its GOP"
-        );
-        let frames = parser.flush();
-        assert_eq!(frames.len(), 1, "force-flushed at EOF, not dropped");
+        // The AU assembler force-completes the ~8 MiB AU (no boundary), and the
+        // GOP byte cap (MAX_PENDING_BYTES) then force-flushes that oversized GOP
+        // during parse rather than buffering it unbounded.
+        let mut frames = parser.parse(&make_pes(data, Some(0)));
+        frames.extend(parser.flush());
+        assert_eq!(frames.len(), 1, "over-cap AU force-flushed, not dropped");
         assert!(frames[0].keyframe);
     }
 

src/mux/codec/reorder.rs

@@ -0,0 +1,389 @@
+//! Display-order PTS reconstruction for sparse-PTS program-stream video.
+//!
+//! MPEG program streams (DVD VOB, HD-DVD EVO) timestamp video at GOP
+//! granularity: only one access unit per GOP carries a PES PTS, and the rest
+//! arrive with none. The H.264 / HEVC / VC-1 parsers collapse a missing PTS to
+//! `0` (`pes.pts.or(dts).unwrap_or(0)`), so on such a source every non-anchor
+//! frame lands on the same block timestamp. A decoder then cannot order them and
+//! reports "non monotonically increasing dts". (The MPEG-2 parser already avoids
+//! this by reconstructing per-picture PTS from `temporal_reference`; these three
+//! codecs carry no such field.)
+//!
+//! [`SparsePtsReorder`] reconstructs a display-order PTS for every frame from two
+//! signals the parsers already provide — the coded picture type (I/P/B) and the
+//! sparse anchor PTS — plus a per-frame duration self-calibrated from the spacing
+//! between consecutive GOP anchors (no external frame-rate needed). It mirrors
+//! the MPEG-2 parser's GOP-buffered origin-locking, but derives display order via
+//! the classic single-anchor-delay rule instead of `temporal_reference`:
+//!
+//! - In DECODE order an anchor (I/P) is stored before the B-frames that
+//!   reference it forward, so decode `I P B P B` displays as `I B P B P`.
+//! - The rule that produces that mapping: an anchor is displayed only after the
+//!   previously-held anchor; a B-frame displays immediately. This is exact for
+//!   the classic (non-hierarchical) GOP structures HD-DVD H.264/VC-1 use.
+//!
+//! This reconstruction is applied ONLY on the program-stream path
+//! (`ContentFormat::MpegPs`). BD/UHD transport streams carry a per-frame PTS and
+//! are never routed through it, so the primary decode path is untouched.
+
+use super::Frame;
+use super::coding::CodingType;
+
+/// Fallback per-frame duration (ns) when the anchor spacing cannot calibrate one
+/// (a stream with a single GOP, or no anchor PTS at all): 24000/1001 fps film,
+/// the dominant HD-DVD cadence. Only affects intra-GOP spacing — each GOP's
+/// origin is re-locked to its own anchor PTS, so a wrong fallback cannot drift
+/// the timeline across GOPs.
+const FALLBACK_FRAME_DUR_NS: i64 = 1_001_000_000 / 24;
+
+/// Force-complete the current GOP once it reaches this many buffered pictures
+/// even without a keyframe. A GOP is normally a few dozen frames; a stream that
+/// never signals a keyframe (open-GOP recovery-point coding, or crafted/corrupt
+/// disc bytes) would otherwise buffer every access unit — the whole title — in
+/// RAM. Mirrors the MPEG-2 parser's `MAX_PENDING_FRAMES` backstop so no
+/// reassembly buffer grows unbounded on disc-controlled input.
+const MAX_GOP_FRAMES: usize = 600;
+
+/// Byte cap on the buffered GOP, complementing [`MAX_GOP_FRAMES`]. A GOP holds a
+/// couple hundred MB at most in practice; this force-completes a run of
+/// few-but-huge access units so a crafted/corrupt stream cannot over-allocate
+/// (the AU assembler caps each frame at 8 MiB, so 600 frames alone could reach
+/// ~5 GiB without this).
+const MAX_GOP_BYTES: usize = 64 * 1024 * 1024;
+
+/// One buffered coded picture awaiting its GOP's completion.
+struct Pending {
+    /// Explicit PES PTS (ns) for this AU, or `None` when the source omitted it.
+    explicit: Option<i64>,
+    /// Coded picture type; `P` (anchor) when the parser could not determine it,
+    /// so an unknown frame is never mis-placed as a bi-predicted B.
+    ctype: CodingType,
+    frame: Frame,
+}
+
+/// A completed GOP, buffered until the NEXT GOP's anchor is known so a per-frame
+/// duration can be calibrated from the two anchors before its frames are emitted.
+struct Gop {
+    pend: Vec<Pending>,
+    /// Display index (0-based) of each `pend` entry, in `pend` (decode) order.
+    dispidx: Vec<i64>,
+    /// Display-frame count (== `pend.len()`).
+    count: i64,
+    /// The anchor: `(explicit_pts, dispidx)` of the first buffered frame that
+    /// carried an explicit PTS, used to lock the display origin. `None` when the
+    /// GOP carried no PTS at all (origin then continues from the running base).
+    anchor: Option<(i64, i64)>,
+}
+
+/// Reconstructs display-order PTS for a sparse-PTS video elementary stream.
+pub(crate) struct SparsePtsReorder {
+    /// Frames of the GOP currently accumulating, in decode order.
+    cur: Vec<Pending>,
+    /// Total `data` bytes buffered in `cur` — the byte-cap counter, reset each
+    /// time `cur` is drained into a completed GOP.
+    cur_bytes: usize,
+    /// The previously-completed GOP, held one step so its duration can be
+    /// calibrated from the next GOP's anchor before it is emitted.
+    held: Option<Gop>,
+    /// Self-calibrated per-frame display duration (ns); 0 until two anchors seen.
+    dur_ns: i64,
+    /// Display time (ns) at which the next emitted GOP should begin, when its own
+    /// anchor is absent. Advanced by each emitted GOP.
+    next_start_ns: i64,
+}
+
+impl SparsePtsReorder {
+    pub(crate) fn new() -> Self {
+        Self {
+            cur: Vec::new(),
+            cur_bytes: 0,
+            held: None,
+            dur_ns: 0,
+            next_start_ns: 0,
+        }
+    }
+
+    /// Feed one parsed frame with its explicit PES PTS (or `None`). Returns any
+    /// frames whose display PTS is now finalized (emitted in decode order).
+    pub(crate) fn push(&mut self, explicit: Option<i64>, frame: Frame) -> Vec<Frame> {
+        let ctype = frame
+            .coding
+            .map(|c| c.coding_type())
+            .unwrap_or(CodingType::P);
+        // A keyframe opens a new GOP: the picture already accumulated in `cur` is
+        // a complete GOP. Complete it (this frame belongs to the NEW GOP). Also
+        // force-complete a pathologically long run that never signalled a
+        // keyframe — bounded by BOTH frame count and total buffered bytes, so a
+        // crafted/corrupt stream of few-but-huge access units cannot buffer
+        // without bound.
+        let mut out = Vec::new();
+        let over_cap = self.cur.len() >= MAX_GOP_FRAMES || self.cur_bytes >= MAX_GOP_BYTES;
+        if (frame.keyframe || over_cap) && !self.cur.is_empty() {
+            out = self.complete_current_gop();
+        }
+        self.cur_bytes += frame.data.len();
+        self.cur.push(Pending {
+            explicit,
+            ctype,
+            frame,
+        });
+        out
+    }
+
+    /// Flush all buffered frames at end of stream.
+    pub(crate) fn flush(&mut self) -> Vec<Frame> {
+        let mut out = self.complete_current_gop();
+        if let Some(gop) = self.held.take() {
+            out.extend(self.emit_gop(gop));
+        }
+        out
+    }
+
+    /// Move `cur` into a completed [`Gop`]; if a GOP was already held, calibrate
+    /// the duration from the two anchors and emit the held one.
+    fn complete_current_gop(&mut self) -> Vec<Frame> {
+        if self.cur.is_empty() {
+            return Vec::new();
+        }
+        let pend = std::mem::take(&mut self.cur);
+        self.cur_bytes = 0;
+        let dispidx = display_indices(pend.iter().map(|p| p.ctype));
+        let count = pend.len() as i64;
+        let anchor = pend
+            .iter()
+            .zip(&dispidx)
+            .find_map(|(p, &d)| p.explicit.map(|pts| (pts, d)));
+        let gop = Gop {
+            pend,
+            dispidx,
+            count,
+            anchor,
+        };
+
+        let mut out = Vec::new();
+        match self.held.take() {
+            Some(held) => {
+                // Calibrate a per-frame duration from the two anchors' spacing,
+                // spread across the held GOP's display-frame count. Approximate
+                // (assumes both anchors sit at a similar relative display slot),
+                // but each GOP re-locks its own origin, so the estimate only sets
+                // intra-GOP spacing.
+                if self.dur_ns == 0 {
+                    if let (Some((p_held, _)), Some((p_next, _))) = (held.anchor, gop.anchor) {
+                        let span = p_next - p_held;
+                        if span > 0 && held.count > 0 {
+                            self.dur_ns = (span / held.count).max(1);
+                        }
+                    }
+                }
+                out = self.emit_gop(held);
+                self.held = Some(gop);
+            }
+            None => self.held = Some(gop),
+        }
+        out
+    }
+
+    /// Assign each frame in `gop` its display PTS and return them in decode order.
+    fn emit_gop(&mut self, gop: Gop) -> Vec<Frame> {
+        let dur = if self.dur_ns > 0 {
+            self.dur_ns
+        } else {
+            FALLBACK_FRAME_DUR_NS
+        };
+        // Lock the display origin: prefer the GOP's own anchor PTS (back out its
+        // display offset); otherwise continue from the running base.
+        let origin = match gop.anchor {
+            Some((pts, didx)) => pts - didx * dur,
+            None => self.next_start_ns,
+        };
+        let Gop {
+            pend,
+            dispidx,
+            count,
+            ..
+        } = gop;
+        let mut out = Vec::with_capacity(pend.len());
+        for (mut p, didx) in pend.into_iter().zip(dispidx) {
+            p.frame.pts_ns = origin + didx * dur;
+            // Carry the calibrated per-frame duration so the muxer emits a
+            // BlockDuration and the back-patched Segment Duration covers the
+            // final frame (the source gives no duration on this path).
+            p.frame.duration_ns = Some(dur as u64);
+            out.push(p.frame);
+        }
+        // Next GOP with no anchor continues after this one's last display slot.
+        self.next_start_ns = origin + count * dur;
+        out
+    }
+}
+
+/// Display index (0-based, decode order in → decode order out) for a GOP's coded
+/// picture types via the classic single-anchor-delay reorder: an anchor (I/P) is
+/// displayed only after the previously-held anchor; a B displays immediately.
+/// Decode `I P B P B` → display indices `[0, 2, 1, 4, 3]` (display `I B P B P`).
+fn display_indices(types: impl Iterator<Item = CodingType>) -> Vec<i64> {
+    let types: Vec<CodingType> = types.collect();
+    let mut disp = vec![0i64; types.len()];
+    let mut held: Option<usize> = None;
+    let mut cursor = 0i64;
+    for (i, &c) in types.iter().enumerate() {
+        match c {
+            CodingType::I | CodingType::P => {
+                if let Some(h) = held {
+                    disp[h] = cursor;
+                    cursor += 1;
+                }
+                held = Some(i);
+            }
+            CodingType::B => {
+                disp[i] = cursor;
+                cursor += 1;
+            }
+        }
+    }
+    if let Some(h) = held {
+        disp[h] = cursor;
+    }
+    disp
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use crate::mux::codec::coding::PictureInfo;
+
+    fn frame(ctype: CodingType, keyframe: bool) -> Frame {
+        Frame {
+            keyframe,
+            coding: Some(PictureInfo::coding_type_only(ctype)),
+            ..Default::default()
+        }
+    }
+
+    #[test]
+    fn display_indices_map_classic_gop() {
+        use CodingType::*;
+        // decode I P B P B  ->  display I B P B P
+        let d = display_indices([I, P, B, P, B].into_iter());
+        assert_eq!(d, vec![0, 2, 1, 4, 3]);
+    }
+
+    #[test]
+    fn display_indices_all_anchors_are_identity() {
+        use CodingType::*;
+        let d = display_indices([I, P, P, P].into_iter());
+        assert_eq!(d, vec![0, 1, 2, 3]);
+    }
+
+    #[test]
+    fn reconstructs_monotonic_display_pts_from_one_anchor_per_gop() {
+        use CodingType::*;
+        // Two GOPs of 5 frames, decode order I P B P B, anchor PTS only on the
+        // GOP's I (0 ns, then ~5-frames-later). Frame duration should calibrate
+        // to the spacing/5 and every frame get a distinct increasing display PTS.
+        let dur = 41_708_333i64;
+        let mut r = SparsePtsReorder::new();
+        let mut got: Vec<i64> = Vec::new();
+        // GOP 1: anchor on the I at t=0.
+        for (k, (ct, pts)) in [(I, Some(0i64)), (P, None), (B, None), (P, None), (B, None)]
+            .into_iter()
+            .enumerate()
+        {
+            let out = r.push(pts, frame(ct, k == 0));
+            got.extend(out.iter().map(|f| f.pts_ns));
+        }
+        // GOP 2: anchor on the I at t = 5*dur (its true display time).
+        for (k, (ct, pts)) in [
+            (I, Some(5 * dur)),
+            (P, None),
+            (B, None),
+            (P, None),
+            (B, None),
+        ]
+        .into_iter()
+        .enumerate()
+        {
+            let out = r.push(pts, frame(ct, k == 0));
+            got.extend(out.iter().map(|f| f.pts_ns));
+        }
+        got.extend(r.flush().iter().map(|f| f.pts_ns));
+
+        // Ten frames out, none dropped.
+        assert_eq!(got.len(), 10, "all frames emitted");
+        // The calibrated duration is (5*dur)/5 = dur.
+        // GOP 1 decode order I P B P B -> display indices 0 2 1 4 3 -> PTS:
+        assert_eq!(
+            &got[0..5],
+            &[0, 2 * dur, dur, 4 * dur, 3 * dur],
+            "GOP1 display PTS in decode order"
+        );
+        // GOP 2 re-locks origin to 5*dur.
+        assert_eq!(
+            &got[5..10],
+            &[5 * dur, 7 * dur, 6 * dur, 9 * dur, 8 * dur],
+            "GOP2 display PTS continue monotonically per display order"
+        );
+    }
+
+    #[test]
+    fn force_flushes_a_gop_that_exceeds_the_byte_cap() {
+        use CodingType::*;
+        // Few-but-huge access units with no keyframe must not accumulate past the
+        // byte cap: a handful of ~MAX_GOP_BYTES/4-sized frames force-completes the
+        // GOP well before the frame-count cap, bounding memory.
+        let big = MAX_GOP_BYTES / 4 + 1;
+        let mut r = SparsePtsReorder::new();
+        let mut emitted = 0usize;
+        // Enough huge frames to trigger several byte-cap completions (a GOP is
+        // held one step for duration calibration, so the first emit lands after
+        // the second cap fires) — well under the 600-frame count cap.
+        for i in 0..16 {
+            let mut f = frame(P, false);
+            f.data = vec![0u8; big];
+            emitted += r.push((i == 0).then_some(0), f).len();
+        }
+        assert!(
+            emitted >= 1,
+            "byte cap force-flushed (emitted {emitted}) before the frame-count cap"
+        );
+    }
+
+    #[test]
+    fn force_flushes_a_gop_that_never_signals_a_keyframe() {
+        use CodingType::*;
+        // A stream that never flags a keyframe (open-GOP recovery points, or a
+        // crafted/corrupt disc) must not buffer the whole title: the cap
+        // force-completes GOPs so frames are emitted well before flush().
+        let mut r = SparsePtsReorder::new();
+        let mut emitted = 0usize;
+        for i in 0..(MAX_GOP_FRAMES * 3) {
+            let pts = (i == 0).then_some(0);
+            emitted += r.push(pts, frame(P, false)).len();
+        }
+        assert!(
+            emitted >= MAX_GOP_FRAMES,
+            "cap force-flushed GOPs before EOF (emitted {emitted})"
+        );
+    }
+
+    #[test]
+    fn no_pts_collisions_within_a_gop() {
+        use CodingType::*;
+        // Every frame distinct in DISPLAY order — the property the mkv muxer
+        // needs so a decoder can derive monotonic DTS.
+        let mut r = SparsePtsReorder::new();
+        let mut all: Vec<i64> = Vec::new();
+        for gop in 0..3 {
+            for (k, ct) in [I, P, B, P, B].into_iter().enumerate() {
+                let pts = (k == 0).then_some(gop as i64 * 5 * 41_708_333);
+                all.extend(r.push(pts, frame(ct, k == 0)).iter().map(|f| f.pts_ns));
+            }
+        }
+        all.extend(r.flush().iter().map(|f| f.pts_ns));
+        let mut sorted = all.clone();
+        sorted.sort_unstable();
+        sorted.dedup();
+        assert_eq!(sorted.len(), all.len(), "no two frames share a display PTS");
+    }
+}

src/mux/codec/vc1.rs

@@ -103,6 +103,10 @@ pub struct Vc1Parser {
     cur_entry_point: Option<Vec<u8>>,
     width: u32,
     height: u32,
+    /// Display-order PTS reconstruction, enabled only on the program-stream
+    /// (HD-DVD EVO) path where the source stamps a PTS once per GOP. `None` on
+    /// the BD/UHD transport path, which carries a per-frame PTS.
+    reorder: Option<super::reorder::SparsePtsReorder>,
 }
 
 impl Default for Vc1Parser {
@@ -120,6 +124,25 @@ impl Vc1Parser {
             cur_entry_point: None,
             width: 1920,
             height: 1080,
+            reorder: None,
+        }
+    }
+
+    /// Enable display-order PTS reconstruction for a program-stream source.
+    /// No-op (leaves timestamps as parsed) for a transport-stream source.
+    pub(crate) fn with_ps_reorder(mut self, enabled: bool) -> Self {
+        if enabled {
+            self.reorder = Some(super::reorder::SparsePtsReorder::new());
+        }
+        self
+    }
+
+    /// Route a finished frame through the PTS reorderer when enabled, else emit
+    /// it directly (unchanged transport-stream behaviour).
+    fn finish(&mut self, explicit: Option<i64>, frame: Frame) -> Vec<Frame> {
+        match self.reorder.as_mut() {
+            Some(r) => r.push(explicit, frame),
+            None => vec![frame],
         }
     }
 }
@@ -169,7 +192,8 @@ impl CodecParser for Vc1Parser {
         // decode order and the player reorders by timecode. Use PTS, not DTS —
         // DTS presents B-frames in decode order (visible judder) and breaks
         // PTS-based seeking. Fall back to DTS only if PTS is absent.
-        let ts_ns = pes.pts.or(pes.dts).map(pts_to_ns).unwrap_or(0);
+        let explicit_pts = pes.pts.or(pes.dts).map(pts_to_ns);
+        let ts_ns = explicit_pts.unwrap_or(0);
         let mut has_seq_header = false;
         let mut has_entry_point = false;
         let mut frame_start: Option<usize> = None;
@@ -321,7 +345,7 @@ impl CodecParser for Vc1Parser {
             vc1_frame_coding_type(data.get(fs + 4..)?, self.cur_seq_header.as_deref())
         });
 
-        vec![Frame {
+        let frame = Frame {
             // Coding-type only: VC-1 field order is not decoded here, so
             // field_order() stays None — honestly absent, never guessed.
             coding: coding_type.map(PictureInfo::coding_type_only),
@@ -333,7 +357,15 @@ impl CodecParser for Vc1Parser {
             discontinuity: pes.discontinuity,
             data: frame_data,
             duration_ns: None,
-        }]
+        };
+        self.finish(explicit_pts, frame)
+    }
+
+    fn flush(&mut self) -> Vec<Frame> {
+        match self.reorder.as_mut() {
+            Some(r) => r.flush(),
+            None => Vec::new(),
+        }
     }
 
     fn codec_private(&self) -> Option<Vec<u8>> {

src/mux/demux_thread.rs

@@ -204,6 +204,14 @@ impl DemuxThread {
                         }
                     } else {
                         let _ = recycle_tx.send(buf);
+                        // No demuxer (a BdTs title with zero streams): still send
+                        // an empty batch so an early consumer disconnect is
+                        // detected here too, exactly like the ts/ps branches above.
+                        // Without it this worker reads the whole disc even after
+                        // the consumer has dropped.
+                        if tx.send(DemuxBatch::Ts(Vec::new())).is_err() {
+                            return;
+                        }
                     }
                 }
                 // Flush tail packets at EOF.
@@ -479,7 +487,7 @@ mod tests {
     #[test]
     fn no_demuxer_configured_still_recycles_and_eofs() {
         // With neither ts nor ps set, the worker must still recycle buffers
-        // and terminate with Eof — never emit a spurious Ts/Ps batch.
+        // and terminate with Eof — also forward an empty batch per buffer for disconnect detection.
         let (pf_tx, pf_rx) = bounded::<std::io::Result<Vec<u8>>>(4);
         let (rc_tx, rc_rx) = bounded::<Vec<u8>>(4);
         let (_dt, rx) = DemuxThread::spawn_zero_copy(pf_rx, rc_tx, (), None, None, None).unwrap();
@@ -492,8 +500,16 @@ mod tests {
         drop(pf_tx);
 
         let batches = collect_batches(&rx, Duration::from_secs(5));
-        assert_eq!(batches.len(), 1, "only the Eof sentinel");
-        assert!(matches!(batches[0], DemuxBatch::Eof));
+        // The no-demuxer branch now forwards an empty Ts batch per buffer for
+        // early consumer-disconnect detection (same rationale as the ts/ps
+        // branches), then the Eof sentinel.
+        assert_eq!(
+            batches.len(),
+            2,
+            "empty Ts disconnect-probe batch, then Eof"
+        );
+        assert!(matches!(batches[0], DemuxBatch::Ts(ref v) if v.is_empty()));
+        assert!(matches!(batches[1], DemuxBatch::Eof));
     }
 
     #[test]

src/mux/disc.rs

@@ -1520,11 +1520,15 @@ mod tests {
                 "read at lba {lba} is not unit-aligned (offset {} % {ALIGN} != 0)",
                 lba - ext_start
             );
-            // Non-tail reads must be a whole number of units; the only
-            // permitted short read is the final partial unit (here COUNT is a
-            // multiple of ALIGN, so every read should be unit-multiple unless
-            // it shrank below one unit — which is itself a single unit).
-            let _ = count;
+            // Non-tail reads must be a whole number of units; the only permitted
+            // short read is a final partial unit (below one unit). Assert it
+            // rather than documenting it — a mid-stream non-unit-multiple read
+            // would straddle AACS unit boundaries and decrypt under the wrong
+            // alignment.
+            assert!(
+                count as u32 % ALIGN == 0 || (count as u32) < ALIGN,
+                "read count {count} is neither a whole number of units nor a sub-unit tail"
+            );
         }
 
         // At least one error was skipped (the bad unit) and a SectorSkipped

src/mux/ebml.rs

@@ -94,6 +94,31 @@ pub fn write_uint(w: &mut impl Write, id: u32, val: u64) -> io::Result<()> {
     }
 }
 
+/// Write a complete EBML signed-integer element (two's-complement, big-endian,
+/// minimal width). Used for `ReferenceBlock` (0xFB), whose value is a signed
+/// tick offset relative to the current block's timestamp.
+pub fn write_int(w: &mut impl Write, id: u32, val: i64) -> io::Result<()> {
+    write_id(w, id)?;
+    // Minimal two's-complement width: shrink while the top byte is pure sign
+    // extension of the next byte's MSB.
+    let be = val.to_be_bytes();
+    let mut start = 0usize;
+    while start < 7 {
+        let sign_ext = if be[start + 1] & 0x80 != 0 {
+            0xFF
+        } else {
+            0x00
+        };
+        if be[start] != sign_ext {
+            break;
+        }
+        start += 1;
+    }
+    let bytes = &be[start..];
+    write_size(w, bytes.len() as u64)?;
+    w.write_all(bytes)
+}
+
 /// Write a complete EBML float element (8-byte double).
 pub fn write_float(w: &mut impl Write, id: u32, val: f64) -> io::Result<()> {
     write_id(w, id)?;
@@ -481,6 +506,25 @@ pub const LUMINANCE_MIN: u32 = 0x55DA;
 pub const BLOCK_ADDITION_MAPPING: u32 = 0x41E4;
 pub const BLOCK_ADD_ID_TYPE: u32 = 0x41E7;
 pub const BLOCK_ADD_ID_EXTRA_DATA: u32 = 0x41ED;
+/// BlockAddIDValue (RFC 9559) — the value a per-frame `BlockAddID` references
+/// to select this BlockAdditionMapping. Values ≥ 2 (1 is the default plain
+/// BlockAdditional). Used by the MVC (`mvcC`) mapping for Blu-ray 3D.
+pub const BLOCK_ADD_ID_VALUE: u32 = 0x41F0;
+
+// Block additions carried inside a BlockGroup — per-frame side data. For
+// Blu-ray 3D (MVC) the dependent (right-eye) view NAL units for an access unit
+// ride here as a BlockAdditional under the track's `mvcC` mapping (RFC 9559
+// §5.1.4.1.4; Matroska Codec Specifications §4.1.5).
+pub const BLOCK_ADDITIONS: u32 = 0x75A1;
+pub const BLOCK_MORE: u32 = 0xA6;
+pub const BLOCK_ADDITIONAL: u32 = 0xA5;
+pub const BLOCK_ADD_ID: u32 = 0xEE;
+/// ReferenceBlock (RFC 9559 element 0xFB, child of BlockGroup) — signed
+/// timestamp (in TimestampScale ticks) of a block this one references, relative
+/// to this block's own timestamp. Its PRESENCE marks the Block as non-keyframe
+/// (a keyframe Block in a BlockGroup carries none). Written for non-keyframe
+/// video frames that must live in a BlockGroup to carry an MVC BlockAdditional.
+pub const REFERENCE_BLOCK: u32 = 0xFB;
 
 // Audio
 pub const AUDIO: u32 = 0xE1;
@@ -960,6 +1004,31 @@ mod tests {
         assert_eq!(buf, [0x42, 0x86, 0x81, 0x00]);
     }
 
+    #[test]
+    fn write_int_minimal_two_complement_width() {
+        // ReferenceBlock (0xFB) signed offsets, minimal two's-complement width.
+        let enc = |v: i64| {
+            let mut b = Vec::new();
+            write_int(&mut b, REFERENCE_BLOCK, v).unwrap();
+            b
+        };
+        assert_eq!(enc(0), [0xFB, 0x81, 0x00], "0 -> 1 byte 0x00");
+        assert_eq!(enc(-1), [0xFB, 0x81, 0xFF], "-1 -> 1 byte 0xFF");
+        assert_eq!(enc(127), [0xFB, 0x81, 0x7F], "127 -> 1 byte");
+        assert_eq!(
+            enc(128),
+            [0xFB, 0x82, 0x00, 0x80],
+            "128 needs 2 bytes (0x80 alone is -128)"
+        );
+        assert_eq!(enc(-128), [0xFB, 0x81, 0x80], "-128 -> 1 byte 0x80");
+        assert_eq!(enc(-129), [0xFB, 0x82, 0xFF, 0x7F], "-129 needs 2 bytes");
+        // i64::MIN is the widest: 8 bytes, size 0x88.
+        let mn = enc(i64::MIN);
+        assert_eq!(mn[0], 0xFB);
+        assert_eq!(mn[1], 0x88);
+        assert_eq!(&mn[2..], &i64::MIN.to_be_bytes());
+    }
+
     // ============================================================
     // write_float — EBML floats here are always 8-byte IEEE-754 doubles,
     // big-endian (Matroska SamplingFrequency/Duration). size byte = 0x88.

src/mux/mkv.rs

@@ -68,6 +68,82 @@ const COLOUR_RANGE_LIMITED: u8 = 1;
 /// Vision configuration record (RFC 9559 + Dolby Vision-in-Matroska spec).
 const BLOCK_ADD_ID_TYPE_DVCC: u64 = 0x6476_6343;
 
+/// BlockAddIDType "mvcC" — the MVCDecoderConfigurationRecord fourcc, big-endian
+/// ASCII 'm''v''c''C'. Matroska BlockAdditionMapping/BlockAddIDType for a
+/// Blu-ray 3D MVC configuration (RFC 9559 + Matroska Codec Specifications
+/// §4.1.5; equals ISO/IEC 14496-15 MVCConfigurationBox('mvcC')). The per-frame
+/// dependent (right-eye) view rides as a BlockAdditional under this mapping.
+const BLOCK_ADD_ID_TYPE_MVCC: u64 = 0x6D76_6343;
+
+/// BlockAddIDValue for the MVC mapping — the value each per-frame `BlockAddID`
+/// references (RFC 9559 requires ≥ 2; 1 is the default plain BlockAdditional).
+const BLOCK_ADD_ID_VALUE_MVC: u64 = 2;
+
+/// Build an `MVCDecoderConfigurationRecord` (ISO/IEC 14496-15:2013 §7.6.2) from
+/// the dependent view's subset-SPS (NAL type 15) and PPS NAL units. This is the
+/// `BlockAddIDExtraData` for the `mvcC` BlockAdditionMapping (and, in the ISO
+/// container, the `MVCConfigurationBox('mvcC')` payload).
+///
+/// Layout mirrors the AVCDecoderConfigurationRecord except byte[4] repurposes
+/// the AVC record's `bit(6) reserved` as
+/// `complete_representation(1) | explicit_au_track(1) | reserved '1111'(4)`.
+/// `profile`/`compat`/`level` describe the WHOLE MVC stream and come from the
+/// subset SPS (bytes 1..=3). `length_size_minus_one` MUST match the base avcC
+/// (freemkv always emits 4-byte length prefixes → 3). SPSs precede subset SPSs
+/// in the array; here the array carries the dependent view's parameter sets.
+///
+/// Returns `None` if either param set is absent, too short, or exceeds the
+/// 16-bit length field (a param set > 65535 bytes is non-conforming and would
+/// mis-frame the record).
+fn mvc_decoder_config_record(subset_sps: &[u8], pps: &[u8]) -> Option<Vec<u8>> {
+    if subset_sps.len() < 4 || subset_sps.len() > 0xFFFF || pps.is_empty() || pps.len() > 0xFFFF {
+        return None;
+    }
+    let mut record = vec![
+        1,             // configurationVersion
+        subset_sps[1], // AVCProfileIndication (whole MVC stream, from subset SPS)
+        subset_sps[2], // profile_compatibility
+        subset_sps[3], // AVCLevelIndication
+        // complete_representation(1)=1 | explicit_au_track(1)=0 |
+        // reserved '1111'(4) | lengthSizeMinusOne(2)=3(11) → 1_0_1111_11 = 0xBF.
+        0xBF,
+        // reserved '0'(1) | numOfSequenceParameterSets(7)=1 → 0_0000001 = 0x01.
+        // NB: distinct from the AVC record's byte[5] (reserved(3)|numSPS(5)).
+        0x01,
+        (subset_sps.len() >> 8) as u8,
+        subset_sps.len() as u8,
+    ];
+    record.extend_from_slice(subset_sps);
+    record.push(1); // numOfPictureParameterSets
+    record.push((pps.len() >> 8) as u8);
+    record.push(pps.len() as u8);
+    record.extend_from_slice(pps);
+    Some(record)
+}
+
+/// Build the `CodecPrivate` for an MVC (Blu-ray 3D) base track: the base view's
+/// `AVCDecoderConfigurationRecord` (`avcc`) followed by an `mvcC` extension
+/// block, per the Matroska Codec Specifications §4.3.9:
+///
+/// ```text
+/// avcC ‖ u32be(extension_block_size − 4) ‖ "mvcC" ‖ MVCDecoderConfigurationRecord
+/// ```
+///
+/// The size field is the extension block length **excluding the 4-byte size
+/// field itself** — i.e. `4 ("mvcC") + record.len()`. This is the track-level
+/// MVC signal that decoders and mediainfo read (the per-frame `BlockAdditional`
+/// under the `mvcC` BlockAdditionMapping carries the dependent view's data). A
+/// plain (2D) track never calls this — it writes its `avcc` verbatim.
+fn mvc_codec_private(avcc: &[u8], record: &[u8]) -> Vec<u8> {
+    let ext_size = (4 + record.len()) as u32; // "mvcC" (4) + record; = block size − 4
+    let mut out = Vec::with_capacity(avcc.len() + 8 + record.len());
+    out.extend_from_slice(avcc);
+    out.extend_from_slice(&ext_size.to_be_bytes());
+    out.extend_from_slice(b"mvcC");
+    out.extend_from_slice(record);
+    out
+}
+
 /// Resolve a video stream's CICP colour code points — `(matrix, transfer,
 /// primaries, range)`, ITU-T H.273 — using a single precedence so EVERY sink
 /// (the MKV muxer here AND the FVI sidecar in `videomap.rs`) agrees and can
@@ -176,6 +252,16 @@ pub struct MkvTrack {
     /// stream is parsed. When `Some`, the serializer emits MasteringMetadata +
     /// MaxCLL/MaxFALL inside Colour; when `None` they are omitted entirely.
     pub hdr10: Option<crate::mux::codec::Hdr10Metadata>,
+    /// Blu-ray 3D (MVC): the dependent (right-eye) view's `(subset_sps, pps)`
+    /// NAL units, from which the serializer builds the `mvcC`
+    /// MVCDecoderConfigurationRecord (ISO/IEC 14496-15 §7.6.2) for the track's
+    /// BlockAdditionMapping. `None` for non-3D tracks. Set at muxer activation
+    /// from the dependent stream's parameter sets — the same deferred path
+    /// `hdr10`/FieldOrder use — never at construction. When `Some`, the per-frame
+    /// dependent view rides as a `BlockAdditional`. (No `StereoMode` is written:
+    /// RFC 9559 assigns no StereoMode value to MVC-in-BlockAdditional; the mvcC
+    /// mapping is the 3D signal.)
+    pub mvc_params: Option<(Vec<u8>, Vec<u8>)>,
 }
 
 /// Build a DOVIDecoderConfigurationRecord (dvcC) — 24 bytes — for the Matroska
@@ -380,6 +466,7 @@ impl MkvTrack {
             // coded picture's PictureInfo before the header is written (the same
             // deferred path FieldOrder uses). `None` here → omitted unless seen.
             hdr10: None,
+            mvc_params: None,
         }
     }
 
@@ -448,6 +535,7 @@ impl MkvTrack {
             bit_depth: 0,
             dv_config: None,
             hdr10: None,
+            mvc_params: None,
         }
     }
 
@@ -485,6 +573,7 @@ impl MkvTrack {
             bit_depth: 0,
             dv_config: None,
             hdr10: None,
+            mvc_params: None,
         }
     }
 }
@@ -530,6 +619,12 @@ pub struct MkvMuxer<W: Write + Seek> {
     /// the primary video. `None` when the title has no video track (no track
     /// drives epochs).
     primary_video_track: Option<usize>,
+    /// Per-track: whether the track declared an `mvcC` BlockAdditionMapping (its
+    /// `mvc_params` was set at activation). A `BlockAdditional` with BlockAddID=2
+    /// is only conforming when the track carries the matching mapping, so
+    /// `write_frame`'s additional is dropped for a track without it (e.g. the
+    /// dependent view's parameter sets were never captured before activation).
+    track_has_mvc_mapping: Vec<bool>,
     /// Cross-clip timeline-continuity corrector (clip-boundary PTS rebasing).
     continuity: TimelineContinuity,
     cues: Vec<CuePoint>,
@@ -557,6 +652,19 @@ pub struct MkvMuxer<W: Write + Seek> {
     track_uids: Vec<u64>,
     /// Segment duration in seconds (from `Info`), for the BPS denominator.
     duration_secs: f64,
+    /// Byte offset of the DURATION element's 8-byte payload when it was written
+    /// as a patch-later placeholder — the source supplied no duration (e.g.
+    /// HD-DVD, whose `.MAP` timemaps are not parsed). `None` when a real duration
+    /// was written up-front. Back-patched at `finish()` from the muxed timeline.
+    duration_patch_pos: Option<u64>,
+    /// Highest block timestamp (TimestampScale ticks) written across all tracks —
+    /// the muxed runtime, used to back-patch the DURATION placeholder.
+    max_block_ticks: i64,
+    /// Timestamp (TimestampScale ticks) of the last video keyframe written on the
+    /// primary video track. A non-keyframe MVC base frame lives in a BlockGroup
+    /// (to carry its dependent-view BlockAdditional) and needs a `ReferenceBlock`
+    /// so players don't mistake it for a keyframe; it references this keyframe.
+    last_video_keyframe_ticks: Option<i64>,
     /// Per-AC-3-audio-track channel-correction state. The DVD IFO audio nibble
     /// is unreliable, so the channel count written in the track header is
     /// corrected from the AC-3 bitstream `acmod` of the first frame on the
@@ -766,11 +874,21 @@ impl<W: Write + Seek> MkvMuxer<W> {
             ebml::TIMESTAMP_SCALE,
             TIMESTAMP_SCALE_NS as u64,
         )?;
-        if duration_secs > 0.0 {
+        let duration_patch_pos = if duration_secs > 0.0 {
             // Duration is expressed in TimestampScale ticks (not ms).
             let duration_ticks = duration_secs * 1_000_000_000.0 / TIMESTAMP_SCALE_NS as f64;
             ebml::write_float(&mut writer, ebml::DURATION, duration_ticks)?;
-        }
+            None
+        } else {
+            // The source declared no duration (e.g. HD-DVD — its `.MAP` timemaps
+            // are not parsed). Reserve a DURATION placeholder now and back-patch
+            // it at finish() from the muxed timeline, so the file still declares a
+            // runtime instead of showing "unknown". The 8-byte float payload sits
+            // 3 bytes in (2-byte ID `0x4489` + 1-byte size `0x88`).
+            let pos = writer.stream_position()?;
+            ebml::write_float(&mut writer, ebml::DURATION, 0.0)?;
+            Some(pos + 3)
+        };
         // Stamp the freemkv version so any muxed file is traceable to the build
         // that produced it (MediaInfo "Writing application"/"library").
         ebml::write_string(&mut writer, ebml::MUXING_APP, crate::MUX_APP)?;
@@ -787,9 +905,23 @@ impl<W: Write + Seek> MkvMuxer<W> {
         let mut track_uids: Vec<u64> = Vec::with_capacity(tracks.len());
         let mut ac3_channel_fixups: std::collections::HashMap<usize, Ac3ChannelFixup> =
             std::collections::HashMap::new();
+        // Per track: whether it emitted a conforming `mvcC` BlockAdditionMapping.
+        // Filled below from the SAME built record that drives the CodecPrivate
+        // mvcC extension, so the three MVC signals never diverge.
+        let mut track_has_mvc_mapping: Vec<bool> = Vec::with_capacity(tracks.len());
         for (i, track) in tracks.iter().enumerate() {
             let track_uid = (i + 1) as u64 | 0x100_0000;
             track_uids.push(track_uid);
+            // Build the MVC (Blu-ray 3D) MVCDecoderConfigurationRecord ONCE per
+            // track from the dependent view's subset-SPS/PPS. `None` for every
+            // non-3D track (and if the params are malformed) — the single source
+            // of truth for the CodecPrivate mvcC extension, the
+            // BlockAdditionMapping, and whether BlockAdditionals are conforming.
+            let mvc_record = track
+                .mvc_params
+                .as_ref()
+                .and_then(|(sps, pps)| mvc_decoder_config_record(sps, pps));
+            track_has_mvc_mapping.push(mvc_record.is_some());
             let entry_pos = ebml::start_master(&mut writer, ebml::TRACK_ENTRY)?;
             ebml::write_uint(&mut writer, ebml::TRACK_NUMBER, (i + 1) as u64)?;
             ebml::write_uint(&mut writer, ebml::TRACK_UID, track_uid)?;
@@ -809,7 +941,20 @@ impl<W: Write + Seek> MkvMuxer<W> {
             }
 
             if let Some(ref cp) = track.codec_private {
-                ebml::write_binary(&mut writer, ebml::CODEC_PRIVATE, cp)?;
+                match mvc_record.as_ref() {
+                    // MVC (Blu-ray 3D) base track: CodecPrivate = base-view avcC
+                    // followed by the `mvcC` extension block. This is the
+                    // track-level signal decoders/mediainfo read to recognise the
+                    // stereoscopic MVC track (the per-frame dependent view rides
+                    // in BlockAdditional under the mapping below).
+                    Some(record) => {
+                        let cp_mvc = mvc_codec_private(cp, record);
+                        ebml::write_binary(&mut writer, ebml::CODEC_PRIVATE, &cp_mvc)?;
+                    }
+                    // Non-MVC (2D/UHD/audio/…): write the codec_private verbatim —
+                    // the unchanged path, byte-identical to a 2D mux.
+                    None => ebml::write_binary(&mut writer, ebml::CODEC_PRIVATE, cp)?,
+                }
             }
             // Pre-0.13 a deferred codecPrivate path existed for video tracks
             // (placeholder reserve + later seek-back fill via
@@ -905,6 +1050,40 @@ impl<W: Write + Seek> MkvMuxer<W> {
                 ebml::end_master(&mut writer, vid_pos)?;
             }
 
+            // Blu-ray 3D (MVC) signaling — BlockAdditionMapping (sibling of
+            // Video) carries the mvcC MVCDecoderConfigurationRecord so players /
+            // mediainfo recognise the dependent (right-eye) view that rides as a
+            // per-frame BlockAdditional under this mapping (BlockAddIDValue = 2).
+            match mvc_record.as_ref() {
+                Some(record) => {
+                    let map_pos = ebml::start_master(&mut writer, ebml::BLOCK_ADDITION_MAPPING)?;
+                    ebml::write_uint(
+                        &mut writer,
+                        ebml::BLOCK_ADD_ID_VALUE,
+                        BLOCK_ADD_ID_VALUE_MVC,
+                    )?;
+                    ebml::write_uint(&mut writer, ebml::BLOCK_ADD_ID_TYPE, BLOCK_ADD_ID_TYPE_MVCC)?;
+                    ebml::write_binary(&mut writer, ebml::BLOCK_ADD_ID_EXTRA_DATA, record)?;
+                    ebml::end_master(&mut writer, map_pos)?;
+                }
+                // `mvc_params` present but the record failed to build (malformed
+                // parameter sets): no mapping, and `track_has_mvc_mapping` above
+                // is already `false`, so BlockAdditionals are dropped — the file
+                // stays conforming rather than carrying an orphaned BlockAddID.
+                None if track.mvc_params.is_some() => {
+                    let (s, p) = track.mvc_params.as_ref().unwrap();
+                    tracing::warn!(
+                        target: "mux",
+                        "MVC track: could not build MVCDecoderConfigurationRecord from the \
+                         dependent view's parameter sets (subset_sps={} B, pps={} B); \
+                         emitting no mvcC mapping — the 3D pairing will not be signalled.",
+                        s.len(),
+                        p.len(),
+                    );
+                }
+                None => {}
+            }
+
             // Dolby Vision signaling — BlockAdditionMapping is a child of the
             // TrackEntry (sibling of Video). Carries the dvcC so players /
             // mediainfo recognise the track as Dolby Vision.
@@ -995,6 +1174,7 @@ impl<W: Write + Seek> MkvMuxer<W> {
             primary_video_track: tracks
                 .iter()
                 .position(|t| t.track_type == ebml::TRACK_TYPE_VIDEO),
+            track_has_mvc_mapping,
             continuity: TimelineContinuity::new(),
             cues: Vec::new(),
             frame_count: 0,
@@ -1007,6 +1187,9 @@ impl<W: Write + Seek> MkvMuxer<W> {
             track_bytes: vec![0u64; tracks.len()],
             track_uids,
             duration_secs,
+            duration_patch_pos,
+            max_block_ticks: 0,
+            last_video_keyframe_ticks: None,
             ac3_channel_fixups,
             opening_capture: None,
         })
@@ -1038,6 +1221,13 @@ impl<W: Write + Seek> MkvMuxer<W> {
     /// (`None`) leaves the written value untouched: an interlaced track keeps
     /// its guess rather than being cleared via a multi-element change. The byte
     /// width is fixed (FieldOrder is 0..=14), so the in-place rewrite is valid.
+    ///
+    /// `block_additional`, when `Some`, is attached to the frame as a Matroska
+    /// `BlockAdditional` (BlockAddID=2) — Blu-ray 3D (MVC): the base view is the
+    /// Block and the dependent (right-eye) access unit rides as the
+    /// BlockAdditional under the track's `mvcC` mapping. Such a frame is always a
+    /// `BlockGroup` (never a SimpleBlock), with a `ReferenceBlock` when it is not
+    /// a keyframe. `None` for every non-3D frame.
     pub fn write_frame(
         &mut self,
         track_idx: usize,
@@ -1045,6 +1235,7 @@ impl<W: Write + Seek> MkvMuxer<W> {
         keyframe: bool,
         data: &[u8],
         duration_ns: Option<u64>,
+        block_additional: Option<&[u8]>,
     ) -> io::Result<()> {
         // --log-level 3: capture the first ~100 coded frames per track to the
         // side file BEFORE any timeline mangling, with the codec parser's own
@@ -1196,17 +1387,82 @@ impl<W: Write + Seek> MkvMuxer<W> {
         // Committed to writing this frame — record its (monotonic) timestamp so
         // the next block on this track is forced strictly later.
         self.last_pts_ticks.insert(track_idx, pts_ticks);
+        // Track the highest block timestamp so a missing source duration can be
+        // back-patched from the real muxed runtime at finish().
+        // Track the block END (start + its own duration when known), not just
+        // the start, so a back-patched Segment Duration covers the final frame's
+        // full presentation instead of understating the runtime by one frame.
+        let block_end_ticks =
+            pts_ticks + duration_ns.map_or(0, |d| (d as i64 / TIMESTAMP_SCALE_NS).max(1));
+        self.max_block_ticks = self.max_block_ticks.max(block_end_ticks);
 
         let relative_ts = (pts_ticks - self.cluster_ts_ticks) as i16;
-        match duration_ns {
-            Some(dur_ns) => {
-                // BlockDuration is in TimestampScale ticks, floored at 1.
-                let duration_ticks = (dur_ns as i64 / TIMESTAMP_SCALE_NS).max(1) as u64;
-                self.write_block_group(track_idx + 1, relative_ts, keyframe, data, duration_ticks)?;
+        let duration_ticks =
+            duration_ns.map(|dur_ns| (dur_ns as i64 / TIMESTAMP_SCALE_NS).max(1) as u64);
+        // A BlockAdditional with BlockAddID=2 is only conforming when the track
+        // declared the matching mvcC BlockAdditionMapping. If it did not (the
+        // dependent view's parameter sets were never captured before the header
+        // was written), drop the additional and emit a plain block rather than a
+        // non-conforming file with an orphaned BlockAddID.
+        let block_additional = match block_additional {
+            Some(a)
+                if self
+                    .track_has_mvc_mapping
+                    .get(track_idx)
+                    .copied()
+                    .unwrap_or(false) =>
+            {
+                Some(a)
             }
-            None => {
-                self.write_simple_block(track_idx + 1, relative_ts, keyframe, data)?;
+            Some(_) => None,
+            None => None,
+        };
+        match block_additional {
+            // MVC: base view Block + dependent-view BlockAdditional, always a
+            // BlockGroup. Non-keyframe base frames get a ReferenceBlock to the
+            // last keyframe (a keyframe carries none), so a player never treats a
+            // P/B frame as a seek point.
+            Some(additional) => {
+                let reference = if keyframe {
+                    None
+                } else {
+                    // Offset (ticks) of the referenced keyframe relative to this
+                    // block. A non-keyframe MUST carry a ReferenceBlock or a reader
+                    // treats it as a seek point; fall back to 0 (self-relative) in
+                    // the pre-first-keyframe corner (unreachable in practice — such
+                    // frames are dropped before a cluster opens) so the marker is
+                    // never absent.
+                    Some(
+                        self.last_video_keyframe_ticks
+                            .map(|kf| kf - pts_ticks)
+                            .unwrap_or(0),
+                    )
+                };
+                self.write_block_group_mvc(
+                    track_idx + 1,
+                    relative_ts,
+                    data,
+                    additional,
+                    reference,
+                    duration_ticks,
+                )?;
             }
+            None => match duration_ticks {
+                // BlockDuration present (PGS subtitles) → BlockGroup.
+                Some(dt) => {
+                    self.write_block_group(track_idx + 1, relative_ts, keyframe, data, dt)?;
+                }
+                None => {
+                    self.write_simple_block(track_idx + 1, relative_ts, keyframe, data)?;
+                }
+            },
+        }
+        // Remember the last PRIMARY-video keyframe's tick so a later non-keyframe
+        // MVC base frame references a keyframe on its OWN track (see the
+        // block_additional path above). Gating to the primary video track avoids a
+        // secondary video track's keyframe becoming a cross-track reference target.
+        if keyframe && Some(track_idx) == self.primary_video_track {
+            self.last_video_keyframe_ticks = Some(pts_ticks);
         }
         self.frame_count += 1;
 
@@ -1268,6 +1524,13 @@ impl<W: Write + Seek> MkvMuxer<W> {
         if self.frame_count == 0 {
             return Err(crate::error::Error::MkvInvalid.into());
         }
+        // The source declared no duration up-front (DURATION was reserved as a
+        // placeholder). Derive the real runtime from the muxed timeline so the
+        // Segment declares it — and so the BPS tags below can be computed.
+        if self.duration_patch_pos.is_some() && self.max_block_ticks > 0 {
+            self.duration_secs =
+                self.max_block_ticks as f64 * TIMESTAMP_SCALE_NS as f64 / 1_000_000_000.0;
+        }
         // Close final cluster
         self.end_cluster()?;
 
@@ -1322,6 +1585,30 @@ impl<W: Write + Seek> MkvMuxer<W> {
                 .seek(std::io::SeekFrom::Start(fixup.value_offset))?;
             self.writer.write_all(&offset.to_be_bytes())?;
         }
+        // Back-patch the DURATION placeholder (source supplied no duration) with
+        // the real runtime from the muxed timeline. The CUES-void and seek-to-end
+        // below re-seek absolutely, so no position restore is needed here.
+        if let Some(pos) = self.duration_patch_pos {
+            if self.max_block_ticks > 0 {
+                self.writer.seek(std::io::SeekFrom::Start(pos))?;
+                self.writer
+                    .write_all(&(self.max_block_ticks as f64).to_be_bytes())?;
+            } else {
+                // The timeline never advanced past tick 0 (a degenerate
+                // single-frame recovery at t=0 with no per-frame duration): we
+                // can't derive a runtime, so DON'T leave a literal DURATION=0.0
+                // (players read that as a zero-length/corrupt file). Void the
+                // whole 11-byte DURATION element (ID 2 + size 1 + 8-byte payload)
+                // so the Segment simply omits it, as an unknown-duration source
+                // did before the back-patch. `pos` is the payload start (+3 from
+                // the element start), so back up 3.
+                self.writer.seek(std::io::SeekFrom::Start(pos - 3))?;
+                ebml::write_id(&mut self.writer, ebml::VOID)?;
+                ebml::write_size(&mut self.writer, 9)?; // 11 - 1 (Void id) - 1 (size)
+                self.writer.write_all(&[0u8; 9])?;
+            }
+        }
+
         // Neutralise the unused CUES Seek entry. The entry is a fixed 21-byte
         // Seek master: SEEK(2 ID + 1 size) + SEEK_ID(2+1) + 4-byte target id +
         // SEEK_POSITION(2+1) + 8-byte value = 21 bytes. A Void (0xEC, 1-byte ID)
@@ -1460,6 +1747,52 @@ impl<W: Write + Seek> MkvMuxer<W> {
         ebml::end_master(&mut self.writer, bg_pos)?;
         Ok(())
     }
+
+    /// Write a BlockGroup carrying the base view Block plus the MVC dependent
+    /// (right-eye) access unit as a `BlockAdditional` (BlockAddID=2), per the
+    /// track's `mvcC` BlockAdditionMapping. A non-keyframe frame gets a
+    /// `ReferenceBlock` (`reference` = referenced keyframe offset in ticks) so it
+    /// is not mistaken for a seek point; `BlockDuration` is written when known.
+    fn write_block_group_mvc(
+        &mut self,
+        track_num: usize,
+        relative_ts: i16,
+        data: &[u8],
+        additional: &[u8],
+        reference: Option<i64>,
+        duration_ticks: Option<u64>,
+    ) -> io::Result<()> {
+        let (tv, tv_len) = track_vint(track_num);
+        let track_vint = &tv[..tv_len];
+        // The 0x80 Keyframe flag is SimpleBlock-only; inside a BlockGroup Block
+        // it is reserved and MUST be 0 — keyframe-ness is signalled by the
+        // presence/absence of ReferenceBlock.
+        let flags: u8 = 0x00;
+        let block_size = track_vint.len() + 2 + 1 + data.len();
+
+        let bg_pos = ebml::start_master(&mut self.writer, ebml::BLOCK_GROUP)?;
+        ebml::write_id(&mut self.writer, ebml::BLOCK)?;
+        ebml::write_size(&mut self.writer, block_size as u64)?;
+        self.writer.write_all(track_vint)?;
+        self.writer.write_all(&relative_ts.to_be_bytes())?;
+        self.writer.write_all(&[flags])?;
+        self.writer.write_all(data)?;
+        if let Some(dt) = duration_ticks {
+            ebml::write_uint(&mut self.writer, ebml::BLOCK_DURATION, dt)?;
+        }
+        if let Some(ref_off) = reference {
+            ebml::write_int(&mut self.writer, ebml::REFERENCE_BLOCK, ref_off)?;
+        }
+        // BlockAdditions → BlockMore { BlockAddID=2, BlockAdditional=dependent AU }.
+        let adds_pos = ebml::start_master(&mut self.writer, ebml::BLOCK_ADDITIONS)?;
+        let more_pos = ebml::start_master(&mut self.writer, ebml::BLOCK_MORE)?;
+        ebml::write_uint(&mut self.writer, ebml::BLOCK_ADD_ID, BLOCK_ADD_ID_VALUE_MVC)?;
+        ebml::write_binary(&mut self.writer, ebml::BLOCK_ADDITIONAL, additional)?;
+        ebml::end_master(&mut self.writer, more_pos)?;
+        ebml::end_master(&mut self.writer, adds_pos)?;
+        ebml::end_master(&mut self.writer, bg_pos)?;
+        Ok(())
+    }
 }
 
 // ============================================================
@@ -1643,6 +1976,7 @@ mod tests {
             bit_depth: 0,
             dv_config: None,
             hdr10: None,
+            mvc_params: None,
         }
     }
 
@@ -1672,6 +2006,7 @@ mod tests {
             bit_depth: 0,
             dv_config: None,
             hdr10: None,
+            mvc_params: None,
         }
     }
 
@@ -1755,7 +2090,7 @@ mod tests {
         let tracks = [make_video_track()];
         let mut muxer = MkvMuxer::new(buf, &tracks, None, 60.0, &[]).unwrap();
         muxer
-            .write_frame(0, 0, true, &[0xDE, 0xAD, 0xBE, 0xEF], None)
+            .write_frame(0, 0, true, &[0xDE, 0xAD, 0xBE, 0xEF], None, None)
             .unwrap();
         let data = muxer.writer.into_inner();
         assert!(
@@ -1775,7 +2110,7 @@ mod tests {
         let tracks = [make_video_track()];
         let mut muxer = MkvMuxer::new(writer, &tracks, Some("Cue Test"), 60.0, &[]).unwrap();
         muxer
-            .write_frame(0, 0, true, &[0x01, 0x02, 0x03], None)
+            .write_frame(0, 0, true, &[0x01, 0x02, 0x03], None, None)
             .unwrap();
         muxer.finish().unwrap();
 
@@ -1801,7 +2136,7 @@ mod tests {
         let tracks = [make_video_track()];
         let mut muxer = MkvMuxer::new(writer, &tracks, Some("NoCue"), 60.0, &[]).unwrap();
         muxer
-            .write_frame(0, 0, true, &[0x01, 0x02, 0x03], None)
+            .write_frame(0, 0, true, &[0x01, 0x02, 0x03], None, None)
             .unwrap();
         // Force the zero-cue branch: drop every cue before finalizing.
         let cues_entry_pos = muxer.cues_seek_entry_pos.expect("CUES seek entry recorded");
@@ -2052,16 +2387,16 @@ mod tests {
         let mut muxer = MkvMuxer::new(buf, &tracks, Some("Multi"), 120.0, &[]).unwrap();
         // Write frames to both tracks
         muxer
-            .write_frame(0, 0, true, &[0x00, 0x00, 0x01], None)
+            .write_frame(0, 0, true, &[0x00, 0x00, 0x01], None, None)
             .unwrap();
         muxer
-            .write_frame(1, 0, false, &[0x0B, 0x77, 0x00], None)
+            .write_frame(1, 0, false, &[0x0B, 0x77, 0x00], None, None)
             .unwrap();
         muxer
-            .write_frame(0, 40_000_000, false, &[0x00, 0x00, 0x01], None)
+            .write_frame(0, 40_000_000, false, &[0x00, 0x00, 0x01], None, None)
             .unwrap();
         muxer
-            .write_frame(1, 32_000_000, false, &[0x0B, 0x77, 0x01], None)
+            .write_frame(1, 32_000_000, false, &[0x0B, 0x77, 0x01], None, None)
             .unwrap();
         // Should not panic
         let data = muxer.writer.into_inner();
@@ -2076,11 +2411,11 @@ mod tests {
 
         // Record position before first frame
         let pos_before_kf = muxer.writer.position();
-        muxer.write_frame(0, 0, true, &[0xAA], None).unwrap();
+        muxer.write_frame(0, 0, true, &[0xAA], None, None).unwrap();
         let pos_after_kf = muxer.writer.position();
 
         muxer
-            .write_frame(0, 1_000_000, false, &[0xBB], None)
+            .write_frame(0, 1_000_000, false, &[0xBB], None, None)
             .unwrap();
         let pos_after_nkf = muxer.writer.position();
 
@@ -2326,7 +2661,7 @@ mod tests {
         let writer = SharedWriter(shared.clone());
         let mut muxer = MkvMuxer::new(writer, tracks, None, 0.0, chapters).unwrap();
         for (t, pts, kf, data) in frames {
-            muxer.write_frame(*t, *pts, *kf, data, None).unwrap();
+            muxer.write_frame(*t, *pts, *kf, data, None, None).unwrap();
         }
         let frame_count = muxer.frame_count;
         muxer.finish().unwrap();
@@ -2688,7 +3023,7 @@ mod tests {
         let mut muxer = MkvMuxer::new(writer, &tracks, None, 0.0, &[]).unwrap();
         for f in &frames {
             muxer
-                .write_frame(0, f.pts_ns, f.keyframe, &f.data, f.duration_ns)
+                .write_frame(0, f.pts_ns, f.keyframe, &f.data, f.duration_ns, None)
                 .unwrap();
         }
         muxer.finish().unwrap();
@@ -2852,6 +3187,49 @@ mod tests {
         );
     }
 
+    /// Scan for the first DURATION element (`0x4489`, 8-byte float payload) and
+    /// return its value in TimestampScale ticks.
+    fn find_duration_ticks(data: &[u8]) -> Option<f64> {
+        data.windows(3)
+            .position(|w| w == [0x44, 0x89, 0x88])
+            .and_then(|i| data.get(i + 3..i + 11))
+            .map(|b| f64::from_be_bytes(b.try_into().unwrap()))
+    }
+
+    #[test]
+    fn duration_placeholder_voided_when_timeline_never_advances() {
+        // Degenerate recovery: a source with no declared duration muxes exactly
+        // one keyframe at tick 0 with no per-frame duration, so max_block_ticks
+        // stays 0. The reserved DURATION placeholder must be VOIDED (element
+        // omitted) rather than left as a bogus 0.0 that players read as a
+        // zero-length file.
+        let tracks = [make_video_track()];
+        let one_frame = vec![(0usize, 0i64, true, vec![0xAAu8; 16])];
+        let (data, _) = mux_to_bytes(&tracks, &[], &one_frame);
+        assert_eq!(
+            find_duration_ticks(&data),
+            None,
+            "no DURATION element (placeholder voided), not a 0.0 duration"
+        );
+    }
+
+    #[test]
+    fn duration_backpatched_from_timeline_when_source_gives_none() {
+        // `mux_to_bytes` muxes with `duration_secs = 0.0` (as an HD-DVD title
+        // does), so DURATION is reserved as a placeholder and must be
+        // back-patched from the muxed timeline at finish() — not left 0/absent.
+        let tracks = [make_video_track()];
+        let frames = frames_for(5.0, 1.0); // ~5 s of 24 fps video
+        let (data, _) = mux_to_bytes(&tracks, &[], &frames);
+        let dur = find_duration_ticks(&data).expect("DURATION element present");
+        let expect = 5.0 * 1_000_000_000.0 / TIMESTAMP_SCALE_NS as f64; // ~50000 ticks
+        assert!(dur > 0.0, "duration back-patched from timeline, not 0");
+        assert!(
+            (dur - expect).abs() < 60.0,
+            "duration ~ real runtime: got {dur} ticks, expected ~{expect}"
+        );
+    }
+
     #[test]
     fn seekhead_points_to_real_elements() {
         let tracks = [make_video_track(), make_audio_track()];
@@ -3034,12 +3412,14 @@ mod tests {
         let writer = SharedWriter(shared.clone());
         let mut muxer = MkvMuxer::new(writer, &tracks, None, 0.0, &[]).unwrap();
         // Audio frames (track 1) and non-keyframe video — no track-0 keyframe.
-        muxer.write_frame(1, 0, true, &[0xAA; 8], None).unwrap();
         muxer
-            .write_frame(0, 10_000_000, false, &[0xBB; 8], None)
+            .write_frame(1, 0, true, &[0xAA; 8], None, None)
             .unwrap();
         muxer
-            .write_frame(1, 20_000_000, true, &[0xCC; 8], None)
+            .write_frame(0, 10_000_000, false, &[0xBB; 8], None, None)
+            .unwrap();
+        muxer
+            .write_frame(1, 20_000_000, true, &[0xCC; 8], None, None)
             .unwrap();
         let err = muxer.finish().unwrap_err();
         assert_eq!(err.kind(), io::ErrorKind::InvalidData);
@@ -3114,7 +3494,7 @@ mod tests {
         let writer = SharedWriter(shared.clone());
         let mut muxer = MkvMuxer::new(writer, &tracks, None, 0.0, &[]).unwrap();
         for (t, pts, kf, data) in &frames_in_order {
-            muxer.write_frame(*t, *pts, *kf, data, None).unwrap();
+            muxer.write_frame(*t, *pts, *kf, data, None, None).unwrap();
         }
         muxer.finish().unwrap();
         let data = shared.lock().unwrap().clone().into_inner();
@@ -3184,7 +3564,7 @@ mod tests {
         let writer = SharedWriter(shared.clone());
         let mut muxer = MkvMuxer::new(writer, tracks, None, 0.0, &[]).unwrap();
         for (t, pts, kf, data, dur) in frames {
-            muxer.write_frame(*t, *pts, *kf, data, *dur).unwrap();
+            muxer.write_frame(*t, *pts, *kf, data, *dur, None).unwrap();
         }
         muxer.finish().unwrap();
         shared.lock().unwrap().clone().into_inner()
@@ -4033,10 +4413,10 @@ mod tests {
         let mut muxer = MkvMuxer::new(writer, &tracks, None, 10.0, &[]).unwrap();
         // Video keyframe 1000 bytes; audio frame 500 bytes.
         muxer
-            .write_frame(0, 0, true, &vec![0xABu8; 1000], None)
+            .write_frame(0, 0, true, &vec![0xABu8; 1000], None, None)
             .unwrap();
         muxer
-            .write_frame(1, 0, false, &vec![0xCDu8; 500], None)
+            .write_frame(1, 0, false, &vec![0xCDu8; 500], None, None)
             .unwrap();
         muxer.finish().unwrap();
         let data = shared.lock().unwrap().clone().into_inner();
@@ -4086,8 +4466,10 @@ mod tests {
         // lfeon(0) = 0b0100_0000 = 0x40. acmod_channels only needs >= 8 bytes.
         let ac3 = vec![0x0B, 0x77, 0x00, 0x00, 0x00, 8 << 3, 0x40, 0x00];
         // Open a cluster with a video keyframe first (cluster invariant).
-        muxer.write_frame(0, 0, true, &[0x01, 0x02], None).unwrap();
-        muxer.write_frame(1, 0, false, &ac3, None).unwrap();
+        muxer
+            .write_frame(0, 0, true, &[0x01, 0x02], None, None)
+            .unwrap();
+        muxer.write_frame(1, 0, false, &ac3, None, None).unwrap();
         muxer.finish().unwrap();
         let data = shared.lock().unwrap().clone().into_inner();
 
@@ -4132,6 +4514,203 @@ mod tests {
         assert!(find_id(&data, ebml::BLOCK_ADDITION_MAPPING).is_none());
     }
 
+    #[test]
+    fn mvc_decoder_config_record_matches_iso_14496_15_layout() {
+        // subset SPS (NAL type 15): [nal_hdr, profile, compat, level, ...].
+        let subset_sps = vec![0x6F, 0x80, 0x00, 0x33, 0x11, 0x22];
+        let pps = vec![0x68, 0xEE, 0x3C];
+        let rec = mvc_decoder_config_record(&subset_sps, &pps).expect("record builds");
+
+        // ISO/IEC 14496-15:2013 §7.6.2 byte layout, verbatim:
+        let expected: Vec<u8> = [
+            vec![
+                1,    // configurationVersion
+                0x80, // AVCProfileIndication  = subset_sps[1]
+                0x00, // profile_compatibility = subset_sps[2]
+                0x33, // AVCLevelIndication    = subset_sps[3]
+                0xBF, // complete_rep(1) explicit_au(0) reserved'1111' lengthSizeMinusOne=3
+                0x01, // reserved'0'(1) numOfSequenceParameterSets(7)=1
+                0x00, 0x06, // sequenceParameterSetLength = 6
+            ],
+            subset_sps.clone(),
+            vec![
+                1, // numOfPictureParameterSets
+                0x00, 0x03, // pictureParameterSetLength = 3
+            ],
+            pps.clone(),
+        ]
+        .concat();
+        assert_eq!(rec, expected, "MVCDecoderConfigurationRecord byte layout");
+
+        // Guards: too-short SPS and empty PPS both refuse (no corrupt record).
+        assert!(mvc_decoder_config_record(&[0x6F, 0x80, 0x00], &pps).is_none());
+        assert!(mvc_decoder_config_record(&subset_sps, &[]).is_none());
+        // Over-length param sets (> 65535) would mis-frame the 16-bit length
+        // field; both must refuse rather than emit a truncated record.
+        let huge = vec![0u8; 0x1_0000];
+        assert!(mvc_decoder_config_record(&huge, &pps).is_none());
+        assert!(mvc_decoder_config_record(&subset_sps, &huge).is_none());
+    }
+
+    #[test]
+    fn mvc_frame_emits_blockgroup_additional_and_reference() {
+        // A track declaring an mvcC mapping: a keyframe base frame carrying a
+        // dependent AU emits BlockGroup > BlockAdditions > BlockMore
+        // {BlockAddID=2, BlockAdditional=dep}; a following non-keyframe adds a
+        // ReferenceBlock so it is not mistaken for a seek point.
+        let mut v = make_video_track();
+        v.mvc_params = Some((
+            vec![0x6F, 0x80, 0x00, 0x33, 0x11, 0x22],
+            vec![0x68, 0xEE, 0x3C],
+        ));
+        let mut muxer = MkvMuxer::new(Cursor::new(Vec::new()), &[v], None, 0.0, &[]).unwrap();
+        let dep_kf = [0xDEu8, 0xAD, 0xBE, 0xEF];
+        let dep_p = [0xCAu8, 0xFE];
+        muxer
+            .write_frame(0, 0, true, &[0x65, 0x01, 0x02], None, Some(&dep_kf))
+            .unwrap();
+        muxer
+            .write_frame(0, 40_000_000, false, &[0x41, 0x03], None, Some(&dep_p))
+            .unwrap();
+        let data = muxer.writer.into_inner();
+
+        assert!(
+            find_id(&data, ebml::BLOCK_ADDITIONS).is_some(),
+            "BlockAdditions (0x75A1) present"
+        );
+        // BlockAddID = 2 (uint): element 0xEE, size 0x81, value 0x02.
+        assert!(
+            data.windows(3).any(|w| w == [0xEE, 0x81, 0x02]),
+            "BlockAddID must be 2"
+        );
+        assert!(
+            data.windows(4).any(|w| w == dep_kf),
+            "keyframe dependent AU present as BlockAdditional"
+        );
+        assert!(
+            data.windows(2).any(|w| w == dep_p),
+            "non-keyframe dependent AU present"
+        );
+        assert!(
+            find_id(&data, ebml::REFERENCE_BLOCK).is_some(),
+            "non-keyframe MVC base frame must carry a ReferenceBlock"
+        );
+    }
+
+    #[test]
+    fn additional_dropped_when_track_has_no_mvc_mapping() {
+        // If a track did NOT declare an mvcC mapping (mvc_params None), a stray
+        // block_additional must be dropped (no orphaned BlockAddID=2 / no
+        // BlockAdditions) so the file stays conforming.
+        let mut muxer = MkvMuxer::new(
+            Cursor::new(Vec::new()),
+            &[make_video_track()],
+            None,
+            0.0,
+            &[],
+        )
+        .unwrap();
+        muxer
+            .write_frame(0, 0, true, &[0x65, 0x01], None, Some(&[0xDE, 0xAD]))
+            .unwrap();
+        let data = muxer.writer.into_inner();
+        assert!(
+            find_id(&data, ebml::BLOCK_ADDITIONS).is_none(),
+            "no BlockAdditions without a declared mvcC mapping"
+        );
+    }
+
+    #[test]
+    fn mvc_track_emits_mvcc_block_addition_mapping() {
+        // A track with mvc_params must emit BlockAdditionMapping (0x41E4) with the
+        // mvcC BlockAddIDType (0x6D766343) and a BlockAddIDValue (0x41F0), so
+        // players / mediainfo recognise the Blu-ray 3D dependent view.
+        let mut v = make_video_track();
+        v.mvc_params = Some((
+            vec![0x6F, 0x80, 0x00, 0x33, 0x11, 0x22],
+            vec![0x68, 0xEE, 0x3C],
+        ));
+        let muxer = MkvMuxer::new(Cursor::new(Vec::new()), &[v], None, 0.0, &[]).unwrap();
+        let data = muxer.writer.into_inner();
+        assert!(
+            find_id(&data, ebml::BLOCK_ADDITION_MAPPING).is_some(),
+            "MVC track must emit BlockAdditionMapping"
+        );
+        assert!(
+            find_id(&data, ebml::BLOCK_ADD_ID_VALUE).is_some(),
+            "MVC mapping must carry BlockAddIDValue"
+        );
+        assert!(
+            data.windows(4).any(|w| w == [0x6D, 0x76, 0x63, 0x43]),
+            "mvcC fourcc must be present as the BlockAddIDType value"
+        );
+        // Without mvc_params, no mapping.
+        let muxer = MkvMuxer::new(
+            Cursor::new(Vec::new()),
+            &[make_video_track()],
+            None,
+            0.0,
+            &[],
+        )
+        .unwrap();
+        let data = muxer.writer.into_inner();
+        assert!(find_id(&data, ebml::BLOCK_ADDITION_MAPPING).is_none());
+    }
+
+    #[test]
+    fn mvc_codec_private_appends_mvcc_extension_block() {
+        // avcC ‖ u32be(4 + record.len()) ‖ "mvcC" ‖ record (Matroska Codec Spec §4.3.9).
+        let avcc = vec![0x01, 0x64, 0x00, 0x33, 0xFF, 0xE1, 0xAA];
+        let record = vec![0x01, 0x80, 0x00, 0x33, 0xBF, 0x01, 0xCC]; // 7 bytes
+        let out = mvc_codec_private(&avcc, &record);
+        assert_eq!(&out[..avcc.len()], &avcc[..], "avcC preserved verbatim");
+        // size field = 4 ("mvcC") + 7 (record) = 11 = extension block size minus 4.
+        assert_eq!(&out[avcc.len()..avcc.len() + 4], &11u32.to_be_bytes());
+        assert_eq!(&out[avcc.len() + 4..avcc.len() + 8], b"mvcC");
+        assert_eq!(
+            &out[avcc.len() + 8..],
+            &record[..],
+            "record after the mvcC fourcc"
+        );
+    }
+
+    #[test]
+    fn mvc_track_codec_private_carries_avcc_plus_mvcc() {
+        // An MVC base track's CodecPrivate must be the base avcC followed by the
+        // mvcC extension — the track-level signal mediainfo/decoders read.
+        let avcc = vec![
+            0x01, 0x64, 0x00, 0x33, 0xFF, 0xE1, 0x00, 0x05, 0x67, 0x64, 0x00, 0x33, 0x99,
+        ];
+        let subset_sps = vec![0x6F, 0x80, 0x00, 0x33, 0x11, 0x22];
+        let pps = vec![0x68, 0xEE, 0x3C];
+        let mut v = make_video_track();
+        v.codec_private = Some(avcc.clone());
+        v.mvc_params = Some((subset_sps.clone(), pps.clone()));
+        let data = MkvMuxer::new(Cursor::new(Vec::new()), &[v], None, 0.0, &[])
+            .unwrap()
+            .writer
+            .into_inner();
+        let record = mvc_decoder_config_record(&subset_sps, &pps).unwrap();
+        let expected = mvc_codec_private(&avcc, &record);
+        assert!(
+            data.windows(expected.len())
+                .any(|w| w == expected.as_slice()),
+            "emitted CodecPrivate must be avcC + mvcC extension"
+        );
+
+        // A non-MVC (2D) track writes its avcC VERBATIM — no mvcC appended.
+        let mut v2 = make_video_track();
+        v2.codec_private = Some(avcc.clone());
+        let d2 = MkvMuxer::new(Cursor::new(Vec::new()), &[v2], None, 0.0, &[])
+            .unwrap()
+            .writer
+            .into_inner();
+        assert!(
+            !d2.windows(4).any(|w| w == b"mvcC"),
+            "2D track CodecPrivate must not carry an mvcC extension"
+        );
+    }
+
     // ---- CodecPrivate emission (avcC / hvcC / VC-1 / MPEG-2) -------------
     //
     // `MkvTrack::video` always builds with `codec_private: None`; the PES mux

src/mux/mkvstream.rs

@@ -120,14 +120,206 @@ struct PendingMux {
     video_track: Option<usize>,
     /// `--log-level 3` opening-capture side-file path (if any).
     opening_capture_path: Option<std::path::PathBuf>,
-    /// Frames received before activation, replayed in order once built.
-    buffered: Vec<crate::pes::PesFrame>,
+    /// Frames received before activation, replayed in order once built. Each
+    /// carries an optional MVC dependent-view `BlockAdditional` (present only
+    /// for a 3D base-view frame that was already paired before activation).
+    buffered: Vec<(crate::pes::PesFrame, Option<Vec<u8>>)>,
 }
 
 /// Matroska container stream.
 pub struct MkvStream {
     disc_title: DiscTitle,
     mode: Mode,
+    /// Blu-ray 3D (MVC) merge state — present iff the title carries an MVC
+    /// dependent (right-eye) view. Folds the dependent stream's frames into the
+    /// base video track as per-frame `BlockAdditional`, paired by PTS, so the
+    /// output is a single MVC track instead of two independent H.264 tracks.
+    mvc: Option<MvcMerge>,
+}
+
+/// Largest number of base frames held awaiting their PTS-matching dependent AU
+/// before the oldest is flushed unpaired (a plain Block). The SSIF interleaves
+/// base and dependent access units per unit, so a base's dependent normally
+/// arrives within one or two frames; this window only bounds memory/latency for
+/// a stream where the pairing drifts.
+const MVC_PAIR_WINDOW: usize = 32;
+
+/// A base-view frame (track already remapped to the muxer's base track index)
+/// awaiting — or already carrying — its dependent-view `BlockAdditional`.
+struct PendingBase {
+    frame: crate::pes::PesFrame,
+    additional: Option<Vec<u8>>,
+}
+
+/// State for folding the MVC dependent (right-eye) view into the base track.
+struct MvcMerge {
+    /// `title.streams` index of the base (left-eye) video stream.
+    base_stream_idx: usize,
+    /// `title.streams` index of the dependent (right-eye) video stream.
+    dep_stream_idx: usize,
+    /// Muxer track index of the base view — where the dependent AU is attached
+    /// as a `BlockAdditional` and where `mvc_params` (the `mvcC` mapping) lives.
+    base_track_idx: usize,
+    /// `title.streams` index → muxer track index. The dependent maps to `None`
+    /// (it becomes a BlockAdditional, not a track); every other stream shifts
+    /// down by one if it followed the dependent in stream order.
+    stream_to_track: Vec<Option<usize>>,
+    /// Base frames (decode order) awaiting their dependent or a window flush.
+    pending_base: std::collections::VecDeque<PendingBase>,
+    /// Dependent AU data keyed by PTS, waiting for the matching base.
+    dep_by_pts: std::collections::HashMap<i64, Vec<u8>>,
+    /// `(subset_sps, pps)` from the first dependent AU — builds the `mvcC`
+    /// MVCDecoderConfigurationRecord for the base track's BlockAdditionMapping.
+    captured_params: Option<(Vec<u8>, Vec<u8>)>,
+    /// Count of dependent AUs dropped with no matching base (diagnostic).
+    orphan_deps: u64,
+}
+
+impl MvcMerge {
+    /// Ingest one incoming frame; returns `(frame, additional)` pairs ready to
+    /// hand to the muxer, in emit order. Base frames buffer briefly to pair with
+    /// their dependent by PTS; the dependent stream produces no frames of its own
+    /// (it becomes `BlockAdditional`); all other streams pass straight through
+    /// with their track index remapped.
+    fn ingest(
+        &mut self,
+        frame: &crate::pes::PesFrame,
+    ) -> Vec<(crate::pes::PesFrame, Option<Vec<u8>>)> {
+        let mut out = Vec::new();
+        if frame.track == self.dep_stream_idx {
+            if self.captured_params.is_none() {
+                self.captured_params = extract_mvc_params(&frame.data);
+            }
+            // Attach to a waiting base of the same PTS, else stash by PTS.
+            if let Some(pb) = self
+                .pending_base
+                .iter_mut()
+                .find(|pb| pb.frame.pts == frame.pts && pb.additional.is_none())
+            {
+                pb.additional = Some(frame.data.clone());
+            } else {
+                // Bound the orphan map BEFORE inserting: if dependents pile up
+                // unpaired (pairing badly drifted), drop the drifted buffer so it
+                // stays bounded — but keep THIS just-arrived dependent, whose base
+                // frame commonly arrives next. Clearing after the insert would
+                // discard it and overcount orphans by one.
+                if self.dep_by_pts.len() >= MVC_PAIR_WINDOW * 4 {
+                    self.orphan_deps += self.dep_by_pts.len() as u64;
+                    self.dep_by_pts.clear();
+                }
+                // A duplicate-PTS dependent (e.g. a stale repeat after a stream
+                // discontinuity) displaces the prior one — count it as an orphan
+                // rather than losing it silently.
+                if self
+                    .dep_by_pts
+                    .insert(frame.pts, frame.data.clone())
+                    .is_some()
+                {
+                    self.orphan_deps += 1;
+                }
+            }
+        } else if frame.track == self.base_stream_idx {
+            let additional = self.dep_by_pts.remove(&frame.pts);
+            let mut remapped = frame.clone();
+            remapped.track = self.base_track_idx;
+            self.pending_base.push_back(PendingBase {
+                frame: remapped,
+                additional,
+            });
+        } else {
+            // Audio / subtitle / other video: remap the track index and forward.
+            let mut remapped = frame.clone();
+            if let Some(Some(t)) = self.stream_to_track.get(frame.track) {
+                remapped.track = *t;
+                out.push((remapped, None));
+            }
+        }
+        self.drain_ready(&mut out);
+        out
+    }
+
+    /// Emit base frames from the FIFO front once each has its dependent attached,
+    /// or flush the oldest unpaired base as a plain Block when the window is full.
+    fn drain_ready(&mut self, out: &mut Vec<(crate::pes::PesFrame, Option<Vec<u8>>)>) {
+        loop {
+            let front_ready = self
+                .pending_base
+                .front()
+                .map(|pb| pb.additional.is_some())
+                .unwrap_or(false);
+            if front_ready || self.pending_base.len() > MVC_PAIR_WINDOW {
+                if let Some(pb) = self.pending_base.pop_front() {
+                    out.push((pb.frame, pb.additional));
+                    continue;
+                }
+            }
+            break;
+        }
+    }
+
+    /// Flush every remaining buffered base frame (unpaired → plain Block) at EOF.
+    fn flush(&mut self) -> Vec<(crate::pes::PesFrame, Option<Vec<u8>>)> {
+        let mut out = Vec::new();
+        for pb in self.pending_base.drain(..) {
+            out.push((pb.frame, pb.additional));
+        }
+        self.orphan_deps += self.dep_by_pts.len() as u64;
+        self.dep_by_pts.clear();
+        out
+    }
+}
+
+/// Hand a frame to the muxer, attaching the MVC dependent view as a
+/// `BlockAdditional` when `additional` is `Some` (a 3D base frame), else a
+/// plain block.
+fn emit_to_muxer(
+    m: &mut MkvMuxer<Box<dyn WriteSeek + Send>>,
+    frame: &crate::pes::PesFrame,
+    additional: Option<&[u8]>,
+) -> io::Result<()> {
+    m.write_frame(
+        frame.track,
+        frame.pts,
+        frame.keyframe,
+        &frame.data,
+        frame.duration_ns,
+        additional,
+    )
+}
+
+/// Scan a length-prefixed (4-byte big-endian) H.264 NAL stream for the first
+/// subset SPS (NAL type 15) and first PPS (NAL type 8) — the two parameter sets
+/// that populate the `mvcC` MVCDecoderConfigurationRecord. Returns
+/// `Some((subset_sps, pps))` only when BOTH are found; `None` otherwise (the
+/// serializer then emits no mvcC mapping and logs it).
+fn extract_mvc_params(data: &[u8]) -> Option<(Vec<u8>, Vec<u8>)> {
+    let mut subset_sps: Option<Vec<u8>> = None;
+    let mut pps: Option<Vec<u8>> = None;
+    let mut i = 0usize;
+    while i + 4 <= data.len() {
+        let len = u32::from_be_bytes([data[i], data[i + 1], data[i + 2], data[i + 3]]) as usize;
+        i += 4;
+        // A zero-length NAL (a stray length prefix) is skipped, not fatal — the
+        // subset SPS / PPS may still follow. A length that runs past the buffer
+        // end IS unrecoverable (the NAL can't be read), so stop there.
+        if len == 0 {
+            continue;
+        }
+        if i + len > data.len() {
+            break;
+        }
+        let nal = &data[i..i + len];
+        i += len;
+        match nal[0] & 0x1F {
+            15 if subset_sps.is_none() => subset_sps = Some(nal.to_vec()),
+            8 if pps.is_none() => pps = Some(nal.to_vec()),
+            _ => {}
+        }
+        if subset_sps.is_some() && pps.is_some() {
+            break;
+        }
+    }
+    Some((subset_sps?, pps?))
 }
 
 impl MkvStream {
@@ -146,10 +338,38 @@ impl MkvStream {
         title: &DiscTitle,
         output_path: Option<&std::path::Path>,
     ) -> io::Result<Self> {
+        // Blu-ray 3D (MVC): a dependent (right-eye) view stream is NOT emitted as
+        // its own track — it is folded into the base track as per-frame
+        // BlockAdditional. Detect it so we skip building a track for it and set up
+        // the merge. `base_stream_idx` is the first video stream.
+        let dep_stream_idx = title
+            .streams
+            .iter()
+            .position(|s| matches!(s, crate::disc::Stream::Video(v) if v.is_mvc_dependent()));
+        // The base is the first NON-dependent video. Excluding the dependent here
+        // means a (malformed / hand-built) title whose only video IS the dependent
+        // yields `base_stream_idx == None` → no merge (the dependent is muxed as an
+        // ordinary track) instead of `base == dep` and a panic on the skipped slot.
+        let base_stream_idx = title
+            .streams
+            .iter()
+            .position(|s| matches!(s, crate::disc::Stream::Video(v) if !v.is_mvc_dependent()));
+        // The merge is only active when BOTH a dependent and a distinct base exist;
+        // only then is the dependent's track skipped/folded.
+        let mvc_active = dep_stream_idx.is_some() && base_stream_idx.is_some();
+        let skip_stream_idx = if mvc_active { dep_stream_idx } else { None };
+
         let mut tracks = Vec::new();
         let mut has_default_video = false;
         let mut has_default_audio = false;
+        // `title.streams` index → muxer track index (`None` = the dependent view,
+        // which has no track). Streams after the dependent shift down by one.
+        let mut stream_to_track: Vec<Option<usize>> = Vec::with_capacity(title.streams.len());
         for (idx, s) in title.streams.iter().enumerate() {
+            if Some(idx) == skip_stream_idx {
+                stream_to_track.push(None);
+                continue;
+            }
             let mut track = match s {
                 crate::disc::Stream::Video(v) => MkvTrack::video(v),
                 crate::disc::Stream::Audio(a) => MkvTrack::audio(a),
@@ -166,9 +386,31 @@ impl MkvStream {
             if let Some(cp) = title.codec_privates.get(idx).and_then(|c| c.as_ref()) {
                 track.codec_private = Some(cp.clone());
             }
+            stream_to_track.push(Some(tracks.len()));
             tracks.push(track);
         }
 
+        // Assemble the MVC merge only when active — i.e. a dependent AND a
+        // distinct base video both exist (established above). `base_stream_idx`
+        // then always has a built track, so its remap is `Some` (no panic path).
+        let mvc = match (mvc_active, dep_stream_idx, base_stream_idx) {
+            (true, Some(dep_stream_idx), Some(base_stream_idx)) => stream_to_track
+                .get(base_stream_idx)
+                .copied()
+                .flatten()
+                .map(|base_track_idx| MvcMerge {
+                    base_stream_idx,
+                    dep_stream_idx,
+                    base_track_idx,
+                    stream_to_track,
+                    pending_base: std::collections::VecDeque::new(),
+                    dep_by_pts: std::collections::HashMap::new(),
+                    captured_params: None,
+                    orphan_deps: 0,
+                }),
+            _ => None,
+        };
+
         // Defer muxer construction (and the TrackEntry dump) until the first
         // coded picture arrives, so the primary video track's FieldOrder is set
         // from the parser's MEASURED value before the header is written — never
@@ -177,6 +419,7 @@ impl MkvStream {
 
         Ok(Self {
             disc_title: title.clone(),
+            mvc,
             mode: Mode::Write(WriteMode::Pending(Box::new(PendingMux {
                 writer,
                 tracks,
@@ -209,6 +452,24 @@ impl MkvStream {
         if let Some(vt) = pending.video_track {
             apply_coding_to_track(&mut pending.tracks[vt], coding, video_picture_seen);
         }
+        // Blu-ray 3D: set the base video track's `mvc_params` from the dependent
+        // view's captured subset-SPS/PPS BEFORE the header is written, so the
+        // TrackEntry carries the `mvcC` BlockAdditionMapping. Captured from the
+        // first dependent AU (which arrives right after the first base AU in the
+        // SSIF), so it is available by the time the first base frame activates.
+        if let Some(mvc) = &self.mvc {
+            if let Some(params) = &mvc.captured_params {
+                if let Some(t) = pending.tracks.get_mut(mvc.base_track_idx) {
+                    t.mvc_params = Some(params.clone());
+                }
+            } else {
+                tracing::warn!(
+                    target: "mux",
+                    "MVC: no dependent-view subset-SPS/PPS captured before activation; \
+                     the base track will carry no mvcC mapping (3D not signalled)."
+                );
+            }
+        }
         // --log-level 3: dump the FINAL TrackEntry metadata (field order set).
         for (i, track) in pending.tracks.iter().enumerate() {
             crate::diag::dump_mkv_track((i + 1) as u64, track);
@@ -223,18 +484,72 @@ impl MkvStream {
         if let Some(path) = &pending.opening_capture_path {
             muxer.set_opening_capture(crate::diag::OpeningCapture::new(path, pending.tracks.len()));
         }
-        for f in pending.buffered.drain(..) {
-            muxer.write_frame(f.track, f.pts, f.keyframe, &f.data, f.duration_ns)?;
+        for (f, additional) in pending.buffered.drain(..) {
+            muxer.write_frame(
+                f.track,
+                f.pts,
+                f.keyframe,
+                &f.data,
+                f.duration_ns,
+                additional.as_deref(),
+            )?;
         }
         self.mode = Mode::Write(WriteMode::Active(Box::new(muxer)));
         Ok(())
     }
 
+    /// Emit one frame (track index already muxer-relative) with an optional MVC
+    /// dependent-view `BlockAdditional`, honouring the deferred-activation
+    /// machinery: the first video frame triggers muxer construction (its coding
+    /// sets FieldOrder); earlier frames buffer. `additional` is `None` for every
+    /// non-3D frame and for the 3D base frames that had no paired dependent.
+    fn emit(&mut self, frame: &crate::pes::PesFrame, additional: Option<&[u8]>) -> io::Result<()> {
+        match &mut self.mode {
+            Mode::Read(_) => return Err(crate::error::Error::StreamReadOnly.into()),
+            Mode::Write(WriteMode::Active(m)) => {
+                return emit_to_muxer(m, frame, additional);
+            }
+            Mode::Write(WriteMode::Building) => return Ok(()),
+            Mode::Write(WriteMode::Pending(_)) => {}
+        }
+        // Pending: the first video frame (or the safety cap) triggers muxer
+        // construction; that frame's coding sets the field order. Other frames
+        // buffer until then.
+        let (activate_now, use_coding) = match &self.mode {
+            Mode::Write(WriteMode::Pending(p)) => {
+                let is_video = match p.video_track {
+                    Some(vt) => frame.track == vt,
+                    // No video track: nothing to wait for — build on frame one.
+                    None => true,
+                };
+                (is_video || p.buffered.len() >= MAX_PENDING_FRAMES, is_video)
+            }
+            _ => unreachable!("guarded above"),
+        };
+        if activate_now {
+            // Pass the trigger frame's coding only when it IS the video frame; a
+            // cap-triggered build never saw the video frame, so nothing measured
+            // is passed (apply_coding_to_track then logs + leaves UNDETERMINED).
+            self.activate(if use_coding { frame.coding } else { None }, use_coding)?;
+            if let Mode::Write(WriteMode::Active(m)) = &mut self.mode {
+                return emit_to_muxer(m, frame, additional);
+            }
+            Ok(())
+        } else {
+            if let Mode::Write(WriteMode::Pending(p)) = &mut self.mode {
+                p.buffered
+                    .push((frame.clone(), additional.map(|a| a.to_vec())));
+            }
+            Ok(())
+        }
+    }
+
     /// Open an MKV file for reading → PES frames.
     pub fn open(mut reader: impl Read + Send + 'static) -> io::Result<Self> {
         let (disc_title, codec_privates, ts_scale_ns) = parse_mkv_header(&mut reader)?;
         Ok(Self {
             disc_title,
+            mvc: None,
             mode: Mode::Read(ReadState {
                 reader: Box::new(reader),
                 cluster_ts_ticks: 0,
@@ -425,59 +740,40 @@ impl crate::pes::Stream for MkvStream {
     }
 
     fn write(&mut self, frame: &crate::pes::PesFrame) -> io::Result<()> {
-        // Fast paths.
-        match &mut self.mode {
-            Mode::Read(_) => return Err(crate::error::Error::StreamReadOnly.into()),
-            Mode::Write(WriteMode::Active(m)) => {
-                return m.write_frame(
-                    frame.track,
-                    frame.pts,
-                    frame.keyframe,
-                    &frame.data,
-                    frame.duration_ns,
-                );
-            }
-            Mode::Write(WriteMode::Building) => return Ok(()),
-            Mode::Write(WriteMode::Pending(_)) => {}
+        if matches!(self.mode, Mode::Read(_)) {
+            return Err(crate::error::Error::StreamReadOnly.into());
         }
-        // Pending: the first video frame (or the safety cap) triggers muxer
-        // construction; that frame's coding sets the field order. Other frames
-        // buffer until then.
-        let (activate_now, use_coding) = match &self.mode {
-            Mode::Write(WriteMode::Pending(p)) => {
-                let is_video = match p.video_track {
-                    Some(vt) => frame.track == vt,
-                    // No video track: nothing to wait for — build on frame one.
-                    None => true,
-                };
-                (is_video || p.buffered.len() >= MAX_PENDING_FRAMES, is_video)
-            }
-            _ => unreachable!("guarded above"),
-        };
-        if activate_now {
-            // Pass the trigger frame's coding only when it IS the video frame; a
-            // cap-triggered build never saw the video frame, so nothing measured
-            // is passed (apply_coding_to_track then logs + leaves UNDETERMINED).
-            self.activate(if use_coding { frame.coding } else { None }, use_coding)?;
-            if let Mode::Write(WriteMode::Active(m)) = &mut self.mode {
-                return m.write_frame(
-                    frame.track,
-                    frame.pts,
-                    frame.keyframe,
-                    &frame.data,
-                    frame.duration_ns,
-                );
-            }
-            Ok(())
-        } else {
-            if let Mode::Write(WriteMode::Pending(p)) = &mut self.mode {
-                p.buffered.push(frame.clone());
-            }
-            Ok(())
+        // Non-3D fast path: emit the frame directly, no clone, no buffering.
+        if self.mvc.is_none() {
+            return self.emit(frame, None);
         }
+        // Blu-ray 3D: run the frame through the MVC merge, which remaps track
+        // indices, folds the dependent view into the base as BlockAdditional
+        // (paired by PTS), and yields 0+ frames ready to emit. `ingest` returns
+        // owned pairs so the `self.mvc` borrow is released before `emit`.
+        let emits = self.mvc.as_mut().unwrap().ingest(frame);
+        for (f, additional) in emits {
+            self.emit(&f, additional.as_deref())?;
+        }
+        Ok(())
     }
 
     fn finish(&mut self) -> io::Result<()> {
+        // Blu-ray 3D: flush any base frames still awaiting a dependent (emitted
+        // unpaired as plain Blocks) before finalizing.
+        if let Some(mvc) = self.mvc.as_mut() {
+            let tail = mvc.flush();
+            let orphans = mvc.orphan_deps;
+            if orphans > 0 {
+                tracing::debug!(
+                    target: "mux",
+                    "MVC: {orphans} dependent-view access units had no matching base frame (dropped)"
+                );
+            }
+            for (f, additional) in tail {
+                self.emit(&f, additional.as_deref())?;
+            }
+        }
         // A title that produced no frames (or only buffered ones) is still
         // finalized into a valid MKV: activate now with no measured coding.
         if matches!(self.mode, Mode::Write(WriteMode::Pending(_))) {
@@ -916,6 +1212,207 @@ mod tests {
     use crate::pes::Stream as _;
     use std::io::Cursor;
 
+    /// Length-prefix (4-byte big-endian) each NAL, as the H.264 parser emits.
+    fn lp(nals: &[&[u8]]) -> Vec<u8> {
+        let mut v = Vec::new();
+        for n in nals {
+            v.extend_from_slice(&(n.len() as u32).to_be_bytes());
+            v.extend_from_slice(n);
+        }
+        v
+    }
+
+    fn mvc_frame(track: usize, pts: i64, keyframe: bool, data: Vec<u8>) -> crate::pes::PesFrame {
+        crate::pes::PesFrame {
+            track,
+            pts,
+            keyframe,
+            data,
+            duration_ns: None,
+            source: None,
+            coding: None,
+        }
+    }
+
+    // A subset SPS (NAL type 15), a PPS (type 8), and a coded-slice-extension
+    // (type 20) — the shape of a dependent-view access unit.
+    const SUBSET_SPS: [u8; 5] = [0x6F, 0x80, 0x00, 0x33, 0xAA]; // 0x6F & 0x1F = 15
+    const DEP_PPS: [u8; 3] = [0x68, 0xEE, 0x3C]; // 0x68 & 0x1F = 8
+    const DEP_SLICE: [u8; 3] = [0x74, 0x11, 0x22]; // 0x74 & 0x1F = 20
+
+    #[test]
+    fn extract_mvc_params_finds_subset_sps_and_pps() {
+        let data = lp(&[&SUBSET_SPS, &DEP_PPS, &DEP_SLICE]);
+        let (s, p) = extract_mvc_params(&data).expect("both param sets present");
+        assert_eq!(s, SUBSET_SPS, "subset SPS (NAL 15) captured verbatim");
+        assert_eq!(p, DEP_PPS, "PPS (NAL 8) captured verbatim");
+        // Missing PPS → None (the serializer then emits no mvcC mapping).
+        assert!(extract_mvc_params(&lp(&[&SUBSET_SPS, &DEP_SLICE])).is_none());
+        // Missing subset SPS → None.
+        assert!(extract_mvc_params(&lp(&[&DEP_PPS, &DEP_SLICE])).is_none());
+    }
+
+    fn empty_merge() -> MvcMerge {
+        MvcMerge {
+            base_stream_idx: 0,
+            dep_stream_idx: 2,
+            base_track_idx: 0,
+            stream_to_track: vec![Some(0), Some(1), None],
+            pending_base: std::collections::VecDeque::new(),
+            dep_by_pts: std::collections::HashMap::new(),
+            captured_params: None,
+            orphan_deps: 0,
+        }
+    }
+
+    #[test]
+    fn mvc_merge_pairs_base_and_dependent_by_pts() {
+        let mut m = empty_merge();
+        let dep = lp(&[&SUBSET_SPS, &DEP_PPS, &DEP_SLICE]);
+
+        // Base arrives first (SSIF order): buffered, nothing emitted yet.
+        let e = m.ingest(&mvc_frame(0, 100, true, lp(&[&[0x65, 1, 2]])));
+        assert!(e.is_empty(), "base held until its dependent arrives");
+
+        // Dependent arrives → base is emitted, remapped to the base track, with
+        // the dependent AU as its BlockAdditional; params are captured.
+        let e = m.ingest(&mvc_frame(2, 100, false, dep.clone()));
+        assert_eq!(e.len(), 1, "the paired base frame is emitted");
+        assert_eq!(e[0].0.track, 0, "remapped to the base muxer track");
+        assert_eq!(
+            e[0].1.as_deref(),
+            Some(dep.as_slice()),
+            "dependent attached"
+        );
+        assert!(m.captured_params.is_some(), "mvcC params captured");
+
+        // Audio passes straight through (remapped, no additional).
+        let e = m.ingest(&mvc_frame(1, 100, true, vec![0xAA]));
+        assert_eq!(e.len(), 1);
+        assert_eq!(e[0].0.track, 1);
+        assert!(e[0].1.is_none());
+
+        // Dependent-before-base (reordered) also pairs.
+        let dep2 = lp(&[&DEP_SLICE]);
+        assert!(m.ingest(&mvc_frame(2, 200, false, dep2.clone())).is_empty());
+        let e = m.ingest(&mvc_frame(0, 200, false, lp(&[&[0x61, 3, 4]])));
+        assert_eq!(e.len(), 1);
+        assert_eq!(e[0].1.as_deref(), Some(dep2.as_slice()));
+    }
+
+    #[test]
+    fn mvc_merge_flushes_unpaired_base_at_eof() {
+        let mut m = empty_merge();
+        // Base with no dependent ever → held, then flushed unpaired at EOF.
+        assert!(
+            m.ingest(&mvc_frame(0, 10, true, vec![0, 0, 0, 1]))
+                .is_empty()
+        );
+        let tail = m.flush();
+        assert_eq!(tail.len(), 1, "unpaired base still emitted");
+        assert!(tail[0].1.is_none(), "no BlockAdditional when unpaired");
+    }
+
+    #[test]
+    fn extract_mvc_params_no_panic_on_truncated_or_empty() {
+        // Empty, sub-header, zero-length NAL, and a length prefix claiming more
+        // than is present must all return None without panicking (untrusted AU).
+        assert!(extract_mvc_params(&[]).is_none());
+        assert!(extract_mvc_params(&[0, 0, 0]).is_none());
+        assert!(
+            extract_mvc_params(&[0, 0, 0, 0]).is_none(),
+            "lone zero-length NAL yields no params"
+        );
+        assert!(
+            extract_mvc_params(&[0, 0, 0, 10, 0x6F]).is_none(),
+            "length prefix past end breaks, no slice panic"
+        );
+        // A zero-length NAL is SKIPPED, not fatal: valid param sets that follow
+        // are still found (a stray length prefix must not abandon the whole AU).
+        let mut d = vec![0, 0, 0, 0];
+        d.extend_from_slice(&lp(&[&SUBSET_SPS, &DEP_PPS]));
+        let (s, p) = extract_mvc_params(&d).expect("params found past the zero-length NAL");
+        assert_eq!(s, SUBSET_SPS);
+        assert_eq!(p, DEP_PPS);
+    }
+
+    #[test]
+    fn mvc_merge_flushes_oldest_base_once_past_window() {
+        let mut m = empty_merge();
+        // Push more unpaired base frames than the window; the excess flush as
+        // plain (unpaired) blocks in FIFO order once len exceeds MVC_PAIR_WINDOW.
+        let n = MVC_PAIR_WINDOW + 8;
+        let mut emitted = 0usize;
+        for pts in 0..n {
+            emitted += m
+                .ingest(&mvc_frame(0, pts as i64, false, vec![0, 0, 0, 1]))
+                .len();
+        }
+        assert_eq!(emitted, 8, "the {n} bases beyond the window flush unpaired");
+        assert_eq!(m.pending_base.len(), MVC_PAIR_WINDOW, "window still held");
+        assert!(m.flush().iter().all(|(_, add)| add.is_none()));
+    }
+
+    #[test]
+    fn mvc_merge_dep_overflow_drops_old_keeps_newest() {
+        let mut m = empty_merge();
+        // Fill dep_by_pts to the bound with unpaired dependents (unique PTS).
+        for pts in 0..(MVC_PAIR_WINDOW * 4) {
+            assert!(
+                m.ingest(&mvc_frame(2, pts as i64, false, lp(&[&DEP_SLICE])))
+                    .is_empty()
+            );
+        }
+        assert_eq!(m.dep_by_pts.len(), MVC_PAIR_WINDOW * 4);
+        // One more overflows: the drifted buffer is cleared BUT the newest survives
+        // so its (soon-to-arrive) base can still pair.
+        let dep_new = lp(&[&DEP_SLICE]);
+        m.ingest(&mvc_frame(2, 9_999, false, dep_new.clone()));
+        assert_eq!(m.dep_by_pts.len(), 1, "old cleared, newest kept");
+        assert!(m.dep_by_pts.contains_key(&9_999));
+        assert_eq!(
+            m.orphan_deps,
+            (MVC_PAIR_WINDOW * 4) as u64,
+            "old buffer counted once"
+        );
+        // The surviving dependent pairs with its base.
+        let e = m.ingest(&mvc_frame(0, 9_999, false, vec![0x61, 1]));
+        assert_eq!(e.len(), 1);
+        assert_eq!(e[0].1.as_deref(), Some(dep_new.as_slice()));
+    }
+
+    #[test]
+    fn create_does_not_panic_when_only_video_is_mvc_dependent() {
+        // A (malformed / hand-built) title whose single video IS the dependent
+        // must NOT panic: base_stream_idx is None, so no merge is set up and the
+        // dependent is muxed as an ordinary track.
+        use crate::disc::{
+            Codec, ColorSpace, DiscTitle, FrameRate, HdrFormat, Resolution, Stream, VideoStream,
+        };
+        let dep = VideoStream {
+            pid: 0x1012,
+            codec: Codec::H264,
+            resolution: Resolution::R1080p,
+            frame_rate: FrameRate::F24,
+            hdr: HdrFormat::Sdr,
+            color_space: ColorSpace::Bt709,
+            display_aspect: None,
+            secondary: true,
+            label: crate::disc::MVC_DEPENDENT_LABEL.to_string(),
+            measured_cicp: None,
+        };
+        let title = DiscTitle {
+            streams: vec![Stream::Video(dep)],
+            ..DiscTitle::empty()
+        };
+        let s = MkvStream::create(Box::new(Cursor::new(Vec::new())), &title)
+            .expect("create must succeed, not panic");
+        assert!(
+            s.mvc.is_none(),
+            "no merge when there is no distinct base view"
+        );
+    }
+
     #[test]
     fn apply_coding_to_track_sets_measured_field_order_never_guesses() {
         use crate::disc::{Codec, ColorSpace, FrameRate, HdrFormat, Resolution, VideoStream};

src/mux/mod.rs

@@ -39,6 +39,7 @@ pub mod resolve;
 // accessors and an alternate `DemuxThread` spawn path. They are kept as
 // part of the parser/demux surface and covered by unit tests; allow the
 // dead-code lint rather than delete still-relevant scaffolding.
+pub(crate) mod au_assembly;
 #[allow(dead_code)]
 pub(crate) mod codec;
 pub(crate) mod demux_sink;

src/mux/pipelined_stream.rs

@@ -75,6 +75,24 @@ pub struct PipelinedPesStream {
     /// Per-track "is inter-coded video" flag (only video has cross-frame
     /// references the gate must protect). Indexed by stream index.
     is_video: Vec<bool>,
+    /// Per-track access-unit assembler. On the PS path a program-stream video AU
+    /// is split across many fixed-size PES fragments; this reassembles them to the
+    /// codec's AU boundary so the parser sees AU-complete PES — the same shape the
+    /// TS demuxer already delivers via PUSI. Self-framing codecs (MPEG-2, audio)
+    /// use passthrough, so every track runs through it uniformly. Indexed by
+    /// stream index. (TS titles are AU-complete already, so this is a passthrough
+    /// there too — `consume_ts` does not use it.)
+    au_asm: Vec<super::au_assembly::AuAssembler>,
+}
+
+/// The `Codec` of a stream, for configuring its [`AuAssembler`].
+fn stream_codec(s: &crate::disc::Stream) -> crate::disc::Codec {
+    use crate::disc::Stream;
+    match s {
+        Stream::Video(v) => v.codec,
+        Stream::Audio(a) => a.codec,
+        Stream::Subtitle(sub) => sub.codec,
+    }
 }
 
 impl PipelinedPesStream {
@@ -102,6 +120,11 @@ impl PipelinedPesStream {
         let resync = (0..title.streams.len())
             .map(|_| super::resync::ResyncGate::new())
             .collect();
+        let au_asm = title
+            .streams
+            .iter()
+            .map(|s| super::au_assembly::AuAssembler::for_codec(stream_codec(s)))
+            .collect();
         Self {
             title,
             parsers,
@@ -115,6 +138,7 @@ impl PipelinedPesStream {
             dropped_nav_packets: 0,
             resync,
             is_video,
+            au_asm,
         }
     }
 
@@ -254,23 +278,50 @@ impl PipelinedPesStream {
                 );
                 continue;
             };
-            let pes = PesPacket {
-                // Carry the PS demuxer's byte-exact source stamp through to the
-                // codec parser, exactly as the TS path does — provenance must
-                // survive the PsPacket → PesPacket seam so the frame's `source`
-                // reaches the mux/index (FVI `src`), never reconstructed.
-                source: ps.source,
-                pid,
-                pts: ps.pts.map(|p| p as i64),
-                dts: ps.dts.map(|d| d as i64),
-                data: ps.data,
-                // PS (DVD/CSS) path: no AACS conceal → no continuity-gap flag.
-                discontinuity: false,
+            // Carry the PS demuxer's byte-exact source stamp through to the codec
+            // parser, exactly as the TS path does — provenance must survive the
+            // PsPacket → PesPacket seam so the frame's `source` reaches the
+            // mux/index (FVI `src`), never reconstructed.
+            let (pts_i64, dts_i64, src) = (
+                ps.pts.map(|p| p as i64),
+                ps.dts.map(|d| d as i64),
+                ps.source,
+            );
+            // Reassemble the PS fragments into AU-complete PES for this track
+            // (passthrough for self-framing codecs — MPEG-2/audio), so the parser
+            // sees exactly the AU-complete shape a transport stream delivers. The
+            // AU-start PTS/source survive the reassembly. A track with no assembler
+            // (only reachable via a hand-built `pid_to_track` outrunning the stream
+            // list) passes the fragment straight through. (PS path: no AACS conceal
+            // → no continuity-gap flag.)
+            let pkts: Vec<PesPacket> = match self.au_asm.get_mut(track) {
+                Some(asm) => asm
+                    .push_owned(ps.data, pts_i64, dts_i64, src, false)
+                    .into_iter()
+                    .map(|au| PesPacket {
+                        source: au.source,
+                        pid,
+                        pts: au.pts,
+                        dts: au.dts,
+                        data: au.data,
+                        discontinuity: au.discontinuity,
+                    })
+                    .collect(),
+                None => vec![PesPacket {
+                    source: src,
+                    pid,
+                    pts: pts_i64,
+                    dts: dts_i64,
+                    data: ps.data,
+                    discontinuity: false,
+                }],
             };
-            if let Some((_, parser)) = self.parsers.iter_mut().find(|(p, _)| *p == pid) {
-                for frame in parser.parse(&pes) {
-                    self.pending_frames
-                        .push_back(PesFrame::from_codec_frame(track, frame));
+            for pes in &pkts {
+                if let Some((_, parser)) = self.parsers.iter_mut().find(|(p, _)| *p == pid) {
+                    for frame in parser.parse(pes) {
+                        self.pending_frames
+                            .push_back(PesFrame::from_codec_frame(track, frame));
+                    }
                 }
             }
         }
@@ -315,11 +366,30 @@ impl Stream for PipelinedPesStream {
                     let pending = &mut self.pending_frames;
                     let resync = &mut self.resync;
                     let is_video = &self.is_video;
+                    let au_asm = &mut self.au_asm;
                     for (pid, parser) in self.parsers.iter_mut() {
                         let Some(&(_, track)) = pid_to_track.iter().find(|(p, _)| p == pid) else {
                             continue;
                         };
-                        for frame in parser.flush() {
+                        // First: the trailing access unit(s) the PS assembler
+                        // buffered past the final fragment (the last AU has no
+                        // following boundary). Parse them, THEN drain the parser's
+                        // own internal buffer (MPEG-2 final GOP, DTS-HD tail).
+                        let mut frames = Vec::new();
+                        let tail = au_asm.get_mut(track).map(|a| a.flush()).unwrap_or_default();
+                        for au in tail {
+                            let pes = PesPacket {
+                                source: au.source,
+                                pid: *pid,
+                                pts: au.pts,
+                                dts: au.dts,
+                                data: au.data,
+                                discontinuity: au.discontinuity,
+                            };
+                            frames.extend(parser.parse(&pes));
+                        }
+                        frames.extend(parser.flush());
+                        for frame in frames {
                             let emit = match resync.get_mut(track) {
                                 Some(gate) => gate.admit(
                                     is_video.get(track).copied().unwrap_or(false),
@@ -801,6 +871,109 @@ mod tests {
         assert!(stream.read().unwrap().is_none(), "unmappable PS dropped");
     }
 
+    /// Build a single-video-stream title on `codec`, a [`CountingParser`] (1 frame
+    /// per PES it is handed), and feed three 0xE0 program-stream fragments that
+    /// together form TWO H.264 access units (AUD-delimited); only AU-start
+    /// fragments carry a PTS. Returns every emitted frame.
+    fn run_ps_fragments(codec: Codec) -> Vec<crate::pes::PesFrame> {
+        let mut title = DiscTitle::empty();
+        title.streams.push(crate::disc::Stream::Video(VideoStream {
+            pid: crate::mux::ps::DVD_VIDEO_PID,
+            codec,
+            resolution: Resolution::R1080p,
+            frame_rate: FrameRate::F23_976,
+            hdr: HdrFormat::Sdr,
+            color_space: ColorSpace::Bt709,
+            display_aspect: None,
+            secondary: false,
+            label: String::new(),
+            measured_cicp: None,
+        }));
+        let parsers: Vec<(u16, Box<dyn CodecParser>)> = vec![(
+            crate::mux::ps::DVD_VIDEO_PID,
+            Box::new(CountingParser {
+                per_pes: 1,
+                flush_n: 0,
+                cp: None,
+            }),
+        )];
+        let pid_to_track = vec![(crate::mux::ps::DVD_VIDEO_PID, 0usize)];
+        let (mut stream, tx) = make_stream(title, parsers, pid_to_track);
+
+        let frag = |pts, data: &[u8]| PsPacket {
+            source: None,
+            stream_id: 0xE0,
+            sub_stream_id: None,
+            pts,
+            dts: None,
+            data: data.to_vec(),
+        };
+        tx.send(DemuxBatch::Ps(vec![
+            frag(Some(9_000), &[0, 0, 1, 0x09, 0xF0, 0, 0, 1, 0x65, 0xAA]), // AU1: AUD + slice head
+            frag(None, &[0xBB, 0xCC]), // AU1: slice tail (no PTS)
+            frag(Some(18_000), &[0, 0, 1, 0x09, 0xF0, 0, 0, 1, 0x65, 0xDD]), // AU2 opener (AUD closes AU1)
+        ]))
+        .unwrap();
+        tx.send(DemuxBatch::Eof).unwrap();
+
+        let mut out = Vec::new();
+        while let Some(f) = stream.read().unwrap() {
+            out.push(f);
+        }
+        out
+    }
+
+    /// PS-path integration: an H.264 access unit split across several fixed-size
+    /// PES fragments (only the first with a PTS) must be REJOINED so the parser
+    /// sees one AU-complete PES with the AU-START pts — not one bogus per-fragment
+    /// frame each with pts 0 (the HD-DVD truncation/corruption bug). The
+    /// `CountingParser` makes it observable: 3 fragments forming 2 AUs → 2 frames.
+    #[test]
+    fn ps_h264_au_split_across_fragments_reassembles_to_one_frame() {
+        let frames = run_ps_fragments(Codec::H264);
+        assert_eq!(
+            frames.len(),
+            2,
+            "3 fragments → 2 access units, not 3 frames"
+        );
+        assert_eq!(frames[0].track, 0);
+        assert_eq!(
+            frames[0].data,
+            vec![0, 0, 1, 0x09, 0xF0, 0, 0, 1, 0x65, 0xAA, 0xBB, 0xCC],
+            "AU1 = fragment1 + fragment2 rejoined"
+        );
+        assert_eq!(
+            frames[0].pts, 9_000,
+            "AU carries its START pts, not the mid-fragment None→0"
+        );
+        assert_eq!(
+            frames[1].data,
+            vec![0, 0, 1, 0x09, 0xF0, 0, 0, 1, 0x65, 0xDD],
+            "AU2 flushed at EOF (no following boundary)"
+        );
+        assert_eq!(frames[1].pts, 18_000);
+    }
+
+    /// Contrast: a self-framing codec (MPEG-2 reassembles in its own parser) uses
+    /// a Passthrough assembler — the SAME three fragments pass straight through as
+    /// three frames, byte-identical to the pre-assembler behaviour. This proves the
+    /// reassembly is gated by codec and does not disturb the DVD/MPEG-2 path.
+    #[test]
+    fn ps_self_framing_codec_is_not_reassembled() {
+        let frames = run_ps_fragments(Codec::Mpeg2);
+        assert_eq!(
+            frames.len(),
+            3,
+            "MPEG-2 passthrough: one frame per fragment"
+        );
+        assert_eq!(frames[0].pts, 9_000);
+        assert_eq!(
+            frames[1].pts, 0,
+            "mid-fragment has no PTS under passthrough"
+        );
+        assert_eq!(frames[2].pts, 18_000);
+    }
+
     /// A batch with no trackable packets must NOT terminate the stream early:
     /// pump_one_batch loops to the next batch. Here an empty-but-untracked
     /// batch is followed by a real frame batch — the consumer must skip the

src/mux/ps.rs

@@ -27,6 +27,12 @@ const PRIVATE_STREAM_1: u8 = crate::consts::pes_stream_id::PRIVATE_STREAM_1;
 /// Private stream 2 (0xBF) — DVD navigation (PCI/DSI). Carries no muxable
 /// elementary stream; expected to be dropped on every disc.
 const PRIVATE_STREAM_2: u8 = crate::consts::pes_stream_id::PRIVATE_STREAM_2;
+/// Extended stream id (0xFD) — the H.222.0 escape whereby the real stream id is
+/// the `stream_id_extension` carried in the PES extension. HD-DVD `.evo` puts its
+/// VC-1 video (and HD audio) here (Shaun of the Dead: VC-1 on `0xFD` ext `0x55`);
+/// a transport stream never uses it. The elementary-stream bytes follow the PES
+/// header exactly like any other PES — only the routing key differs.
+const EXTENDED_STREAM_ID: u8 = 0xFD;
 
 /// Hard cap on the demuxer's reassembly buffer. A length-0 (unbounded) video
 /// PES is delimited by the next PS-layer boundary; if a corrupt stream declares
@@ -73,9 +79,16 @@ pub const DVD_VIDEO_PID: u16 = 0xE0;
 /// source of truth shared with `Disc::scan_dvd_titles`
 /// (`src/disc/dvd.rs`), which sets each `AudioStream.pid` from the same
 /// function so demuxer output routes through the title's `pid_to_track`.
+///
+/// HD-DVD (`.evo` Enhanced VOB) carries Dolby Digital Plus (E-AC-3) on
+/// `private_stream_1` sub-stream ids `0xC0..=0xC7` — a range DVD never uses
+/// (DVD audio is `0x80..=0x8F` / `0xA0..=0xA7`), so admitting it here is purely
+/// additive and cannot change any DVD mapping. The PID is `0xBD00 | sub` just
+/// like the DVD audio ranges, so a mixed HD-DVD title (four DD+ tracks
+/// `0xC0..0xC3`) routes each track to its own distinct PID.
 pub fn dvd_audio_pid(sub_stream_id: u8) -> Option<u16> {
     match sub_stream_id {
-        0x80..=0x8F | 0xA0..=0xA7 => Some(0xBD00 | sub_stream_id as u16),
+        0x80..=0x8F | 0xA0..=0xA7 | 0xC0..=0xC7 => Some(0xBD00 | sub_stream_id as u16),
         _ => None,
     }
 }
@@ -90,6 +103,17 @@ pub fn dvd_subtitle_pid(sub_stream_id: u8) -> Option<u16> {
     }
 }
 
+/// Canonical PID for an HD-DVD extended-stream-id (`0xFD`) stream, keyed by its
+/// `stream_id_extension`: `0xFD00 | ext`. Disjoint from the DVD video (`0xE0`) and
+/// `private_stream_1` (`0xBD00..`) PID spaces, so several elementary streams
+/// multiplexed on `0xFD` (VC-1 video, MLP/TrueHD audio) never collide. The
+/// scanner's head probe and `PsPacket::dvd_pid` derive the same PID from the same
+/// `stream_id_extension`, so demux output routes through the title's
+/// `pid_to_track`.
+pub fn hddvd_extended_pid(stream_id_extension: u8) -> u16 {
+    0xFD00 | stream_id_extension as u16
+}
+
 impl PsPacket {
     /// Map this packet to the canonical DVD PID assigned by
     /// `Disc::scan_dvd_titles` (`src/disc/dvd.rs`), so demux output can
@@ -112,6 +136,12 @@ impl PsPacket {
                 let sub = self.sub_stream_id?;
                 dvd_audio_pid(sub).or_else(|| dvd_subtitle_pid(sub))
             }
+            // HD-DVD extended-stream-id (0xFD): route by the stream_id_extension
+            // (carried in `sub_stream_id`) to a distinct `0xFD00 | ext` PID, so a
+            // disc that puts several elementary streams on 0xFD keeps them apart.
+            // The codec (VC-1 etc.) is decided by the scanner's head probe, not
+            // here — this only assigns a stable routing key.
+            EXTENDED_STREAM_ID => self.sub_stream_id.map(hddvd_extended_pid),
             _ => None,
         }
     }
@@ -347,9 +377,74 @@ fn find_ps_boundary(data: &[u8], from: usize) -> Option<usize> {
 /// Check whether a start code byte is a valid PES stream ID that carries payload.
 fn is_pes_stream_id(id: u8) -> bool {
     // Video: 0xE0-0xEF, MPEG audio: 0xC0-0xDF, private stream 1: 0xBD,
-    // private stream 2: 0xBF, padding: 0xBE, ECM/EMM etc.
-    // We parse anything in the payload-bearing PES range.
-    crate::consts::pes_stream_id::PAYLOAD_RANGE.contains(&id)
+    // private stream 2: 0xBF, padding: 0xBE, ECM/EMM etc. — plus the HD-DVD
+    // extended-stream-id (0xFD), which carries VC-1 video / HD audio.
+    crate::consts::pes_stream_id::PAYLOAD_RANGE.contains(&id) || id == EXTENDED_STREAM_ID
+}
+
+/// For an extended-stream-id (`0xFD`) PES, walk the optional PES-header fields to
+/// the PES extension and read the 7-bit `stream_id_extension` — the real stream
+/// id. `data` starts at the PES start code; the optional fields live in
+/// `data[9..header_end]` (all bounds-checked against `header_end`). Returns `None`
+/// if the extension is absent or malformed.
+fn parse_stream_id_extension(data: &[u8], flags2: u8, header_end: usize) -> Option<u8> {
+    let get = |p: usize| -> Option<u8> {
+        if p < header_end {
+            data.get(p).copied()
+        } else {
+            None
+        }
+    };
+    let mut pos = 9usize;
+    let pts_dts = (flags2 >> 6) & 0x03;
+    if pts_dts & 0x02 != 0 {
+        pos += 5; // PTS
+    }
+    if pts_dts == 0x03 {
+        pos += 5; // DTS
+    }
+    if flags2 & 0x20 != 0 {
+        pos += 6; // ESCR
+    }
+    if flags2 & 0x10 != 0 {
+        pos += 3; // ES_rate
+    }
+    if flags2 & 0x08 != 0 {
+        pos += 1; // DSM_trick_mode
+    }
+    if flags2 & 0x04 != 0 {
+        pos += 1; // additional_copy_info
+    }
+    if flags2 & 0x02 != 0 {
+        pos += 2; // PES_CRC
+    }
+    if flags2 & 0x01 == 0 {
+        return None; // no PES_extension
+    }
+    let ext_flags = get(pos)?;
+    pos += 1;
+    if ext_flags & 0x80 != 0 {
+        pos += 16; // PES_private_data
+    }
+    if ext_flags & 0x40 != 0 {
+        // pack_header_field: 1-byte length + that many bytes.
+        pos += 1 + get(pos)? as usize;
+    }
+    if ext_flags & 0x20 != 0 {
+        pos += 2; // program_packet_sequence_counter
+    }
+    if ext_flags & 0x10 != 0 {
+        pos += 2; // P-STD_buffer
+    }
+    if ext_flags & 0x01 == 0 {
+        return None; // no PES_extension_flag_2
+    }
+    // PES_extension_field_length (7 bits, marker in the top bit), then the
+    // stream_id_extension byte: present when its top bit (the extension flag) is 0.
+    let _field_len = get(pos)? & 0x7F;
+    pos += 1;
+    let b = get(pos)?;
+    (b & 0x80 == 0).then_some(b & 0x7F)
 }
 
 /// Parse a single PES packet from a byte slice that starts at the start code.
@@ -416,10 +511,30 @@ fn parse_pes_packet(data: &[u8]) -> Option<PsPacket> {
 
     // For private stream 1, the first payload byte is the sub-stream ID,
     // followed by a sub-header whose length depends on the sub-stream type.
-    let (sub_stream_id, es_data) = if stream_id == PRIVATE_STREAM_1 && !payload.is_empty() {
+    let (sub_stream_id, es_data) = if stream_id == EXTENDED_STREAM_ID {
+        // HD-DVD extended-stream-id: the real stream id lives in the
+        // stream_id_extension inside the PES extension. There is no leading
+        // sub-header byte on the payload (unlike private_stream_1), so the ES
+        // is the payload verbatim.
+        (
+            parse_stream_id_extension(data, data[7], header_end),
+            payload.to_vec(),
+        )
+    } else if stream_id == PRIVATE_STREAM_1 && !payload.is_empty() {
         let sub_id = payload[0];
         let skip = match sub_id {
             0x80..=0x8F => 4, // AC3/DTS: sub_id + frame_count + access_unit_ptr(2)
+            // HD-DVD Dolby Digital Plus (E-AC-3): the sub-header is the same
+            // 4-byte shape as DVD AC-3 — sub_id + number_of_frames(1) +
+            // first_access_unit_pointer(2). Verified empirically on ANCHORMAN
+            // EVO: across every 0xC0..=0xC7 packet the 0x0B77 E-AC-3 syncword
+            // sits `first_access_unit_pointer` bytes past this 4-byte header
+            // (the leading bytes are the tail of the previous frame). Stripping
+            // exactly these 4 bytes on EVERY packet yields a clean, continuous
+            // E-AC-3 elementary stream that the ac3 parser reassembles across
+            // PES boundaries; a shorter skip would splice the sub-header bytes
+            // into a straddling frame and corrupt it.
+            0xC0..=0xC7 => 4,
             0xA0..=0xA7 => 7, // LPCM: sub_id + frames + ptr(2) + emphasis + quant_freq + channels
             _ => 1,
         };
@@ -836,6 +951,90 @@ mod tests {
         }
     }
 
+    #[test]
+    fn parse_extended_stream_id_extracts_stream_id_extension() {
+        // SHAUN's VC-1 video PES: stream_id 0xFD, flags2=0x01 (PES_extension
+        // only), header_data_length=3, optional bytes 0x0F/... — build the
+        // minimal well-formed variant: ext_flags=0x01 (PES_extension_flag_2),
+        // field_len=0x81, stream_id_extension=0x55. Payload is the ES.
+        let mut pkt = vec![0x00, 0x00, 0x01, EXTENDED_STREAM_ID];
+        let opt = [0x01u8, 0x81, 0x55];
+        let es = [0xDEu8, 0xAD, 0xBE, 0xEF];
+        let len = (3 + opt.len() + es.len()) as u16;
+        pkt.extend_from_slice(&len.to_be_bytes());
+        pkt.extend_from_slice(&[0x80, 0x01, opt.len() as u8]);
+        pkt.extend_from_slice(&opt);
+        pkt.extend_from_slice(&es);
+
+        let parsed = parse_pes_packet(&pkt).expect("parses");
+        assert_eq!(parsed.stream_id, EXTENDED_STREAM_ID);
+        assert_eq!(
+            parsed.sub_stream_id,
+            Some(0x55),
+            "stream_id_extension extracted from PES extension"
+        );
+        // ES is the payload verbatim — no leading sub-header byte stripped.
+        assert_eq!(parsed.data, es);
+        // Routes to the extended-stream-id PID space.
+        assert_eq!(parsed.dvd_pid(), Some(hddvd_extended_pid(0x55)));
+        assert_eq!(parsed.dvd_pid(), Some(0xFD55));
+    }
+
+    #[test]
+    fn parse_extended_stream_id_skips_pts_and_dts_before_the_extension() {
+        // The common real case: an AU-opening 0xFD VC-1 video PES carries a PTS
+        // (and often DTS) in the optional-header region, which the parser must
+        // SKIP (PTS +5, DTS +5) to reach the PES_extension → stream_id_extension.
+        // Both branches were previously untested (flags2 there was 0x01, skipping
+        // everything), so an off-by-one in the skip would silently misroute video.
+        let build = |flags2: u8, skip: usize| {
+            let mut pkt = vec![0x00, 0x00, 0x01, EXTENDED_STREAM_ID];
+            // optional region: `skip` bytes (PTS/DTS placeholders) then
+            // ext_flags=0x01, field_len=0x81, stream_id_extension=0x55.
+            let mut opt = vec![0xFFu8; skip];
+            opt.extend_from_slice(&[0x01, 0x81, 0x55]);
+            let es = [0xDEu8, 0xAD];
+            let len = (3 + opt.len() + es.len()) as u16;
+            pkt.extend_from_slice(&len.to_be_bytes());
+            // flags1=0x80, flags2, header_data_length = optional region length.
+            pkt.extend_from_slice(&[0x80, flags2, opt.len() as u8]);
+            pkt.extend_from_slice(&opt);
+            pkt.extend_from_slice(&es);
+            pkt
+        };
+        // PTS present (pts_dts bits = 10 → flags2 0x80) + PES_extension (0x01).
+        let pts_only = parse_pes_packet(&build(0x81, 5)).expect("parses");
+        assert_eq!(
+            pts_only.sub_stream_id,
+            Some(0x55),
+            "extension found after skipping a 5-byte PTS"
+        );
+        // PTS+DTS present (pts_dts bits = 11 → flags2 0xC0) + PES_extension.
+        let pts_dts = parse_pes_packet(&build(0xC1, 10)).expect("parses");
+        assert_eq!(
+            pts_dts.sub_stream_id,
+            Some(0x55),
+            "extension found after skipping a 10-byte PTS+DTS"
+        );
+    }
+
+    #[test]
+    fn parse_extended_stream_id_without_extension_yields_no_sub_id() {
+        // A 0xFD PES that declares no PES_extension (flags2=0x00) can't carry a
+        // stream_id_extension → sub_stream_id None, and dvd_pid falls through.
+        let mut pkt = vec![0x00, 0x00, 0x01, EXTENDED_STREAM_ID];
+        let es = [0x11u8, 0x22];
+        let len = (3 + es.len()) as u16;
+        pkt.extend_from_slice(&len.to_be_bytes());
+        pkt.extend_from_slice(&[0x80, 0x00, 0x00]);
+        pkt.extend_from_slice(&es);
+
+        let parsed = parse_pes_packet(&pkt).expect("parses");
+        assert_eq!(parsed.sub_stream_id, None);
+        assert_eq!(parsed.dvd_pid(), None);
+        assert_eq!(parsed.data, es);
+    }
+
     #[test]
     fn dvd_pid_matches_scanner_assignment() {
         // Video → 0xE0 (matches dvd.rs VideoStream pid).
@@ -1175,6 +1374,51 @@ mod tests {
         assert_eq!(dvd_audio_pid(0xA8), None);
     }
 
+    #[test]
+    fn hddvd_ddplus_substream_maps_to_bd_pid() {
+        // HD-DVD Dolby Digital Plus sub-ids 0xC0..=0xC7 map to 0xBD00|sub,
+        // distinct per track and disjoint from the DVD audio space. A DVD never
+        // emits these, so the range is purely additive.
+        assert_eq!(dvd_audio_pid(0xC0), Some(0xBDC0));
+        assert_eq!(dvd_audio_pid(0xC3), Some(0xBDC3));
+        assert_eq!(dvd_audio_pid(0xC7), Some(0xBDC7));
+        // Just outside the range.
+        assert_eq!(dvd_audio_pid(0xBF), None);
+        assert_eq!(dvd_audio_pid(0xC8), None);
+        // Four DD+ tracks (ANCHORMAN) get four distinct PIDs.
+        let pids: Vec<u16> = (0xC0u8..=0xC3).map(|s| dvd_audio_pid(s).unwrap()).collect();
+        assert_eq!(pids, vec![0xBDC0, 0xBDC1, 0xBDC2, 0xBDC3]);
+        // And route through dvd_pid on a private_stream_1 packet.
+        assert_eq!(mk(0xBD, Some(0xC0)).dvd_pid(), Some(0xBDC0));
+        assert_eq!(mk(0xBD, Some(0xC3)).dvd_pid(), Some(0xBDC3));
+    }
+
+    #[test]
+    fn hddvd_ddplus_pes_strips_4byte_subheader_to_syncword() {
+        // A private_stream_1 PES carrying DD+ (sub-id 0xC0) has a 4-byte
+        // sub-header (sub_id + num_frames(1) + access_unit_ptr(2)); the demuxer
+        // must strip exactly those 4 bytes so es_data begins at the E-AC-3
+        // payload — here the 0x0B77 syncword sits right after the sub-header.
+        let mut demuxer = PsDemuxer::new();
+        let mut data = vec![
+            0x00, 0x00, 0x01, 0xBD, // private stream 1
+            0x00, 0x0B, // PES_packet_length = 11 (flags2 + hdl1 + 8 payload)
+            0x80, 0x00, 0x00, // no PTS, header_data_len = 0
+            0xC0, // sub-stream id: DD+ track 0
+            0x01, 0x00, 0x00, // num_frames(1) + access_unit_ptr(2)
+            0x0B, 0x77, 0xDE, 0xAD, // E-AC-3 syncword + payload
+        ];
+        data.extend_from_slice(&[0x00, 0x00, 0x01, 0xB9]);
+        let p = demuxer.feed(&data);
+        assert_eq!(p.len(), 1);
+        assert_eq!(p[0].sub_stream_id, Some(0xC0));
+        assert_eq!(
+            p[0].data,
+            vec![0x0B, 0x77, 0xDE, 0xAD],
+            "4-byte DD+ sub-header stripped; es_data starts at the syncword"
+        );
+    }
+
     #[test]
     fn dvd_subtitle_pid_range_boundaries() {
         // VobSub subtitle sub-ids 0x20..=0x3F map to the identity PID.

src/mux/resolve.rs

@@ -358,6 +358,12 @@ pub fn input(url: &str, opts: &InputOptions) -> io::Result<Box<dyn crate::pes::S
             // case must NOT raise a false E7023.
             disc.ensure_title_decryptable(opts.raw, &keys, title_is_clear)
                 .map_err(|e| -> io::Error { e.into() })?;
+            // Upfront FMTS gate, parallel to the unit-key gate above. With
+            // BYPASS_FMTS_KEY this is a no-op and a 2.1 disc's forensic units are
+            // concealed as ordinary decrypt loss below; without it, a 2.1 disc
+            // lacking segment keys fails here rather than emitting a holed mux.
+            disc.ensure_forensic_segments_decryptable(opts.raw)
+                .map_err(|e| -> io::Error { e.into() })?;
             // Correct TrueHD channel counts (MPLS understates 7.1/Atmos as 5.1)
             // by probing the first DECRYPTED access units of the chosen title.
             // A fresh reader avoids disturbing the mux reader below. Skipped in
@@ -569,7 +575,17 @@ fn build_demux_state(title: &DiscTitle, format: ContentFormat) -> DemuxState {
         pids.push(pid);
         pid_to_track.push((pid, idx));
         let is_dvd_ps = matches!(format, ContentFormat::MpegPs);
-        parsers.push((pid, super::codec::parser_for_codec(codec, None, is_dvd_ps)));
+        // The Blu-ray 3D MVC dependent (right-eye) view uses a param-set-
+        // passthrough H.264 parser so each frame is a self-contained dependent
+        // access unit for a BlockAdditional; every other stream uses the
+        // ordinary parser for its codec.
+        let parser = match s {
+            crate::disc::Stream::Video(v) if v.is_mvc_dependent() => {
+                super::codec::parser_for_mvc_dependent(codec, is_dvd_ps)
+            }
+            _ => super::codec::parser_for_codec(codec, None, is_dvd_ps),
+        };
+        parsers.push((pid, parser));
     }
     let (ts, ps) = match format {
         ContentFormat::MpegPs => (None, Some(super::ps::PsDemuxer::new())),
@@ -638,15 +654,17 @@ pub fn build_iso_pipeline<S: SectorSource + Send + 'static>(
             .tolerate_decrypt_loss();
     // Install the fresh-key-on-failure callback (if any) so a unit no held key
     // decrypts is re-tried via the application's key source before being counted
-    // as loss.
+    // as loss. An AACS 2.1 forensic-segment unit that no key opens is just an
+    // undecryptable unit like any other: concealed and counted as decrypt loss —
+    // a loss is a loss, no FMTS special casing.
     if let Some(cb) = fetch {
         decrypting = decrypting.with_key_fetch(cb);
     }
-    // Grab the decrypt-loss counter before the decorator is moved into the
-    // producer thread. It tracks bytes of scrambled AACS units no key could
-    // decrypt — silent loss the demux drops; the consuming stream surfaces it
-    // through `lost_bytes()` so the mux abort gate sees a partial decrypt
-    // failure rather than a clean rip.
+    // Grab the loss counters before the decorator is moved into the producer
+    // thread. It tracks bytes of scrambled AACS units no key could decrypt —
+    // silent loss the demux drops; the consuming stream surfaces it through
+    // `lost_bytes()` so the mux abort gate sees a partial decrypt failure rather
+    // than a clean rip. Forensic (2.1) undecryptable units land here too.
     let decrypt_loss = decrypting.decrypt_loss();
 
     // Wrong-substream fix (Silence-of-the-Lambs): before the prefetcher takes

src/mux/ts.rs

@@ -167,6 +167,10 @@ impl PesAssembler {
                 self.buffer.clear();
                 self.active = false;
                 self.header_remaining = 0;
+                // A dropped partial PES is a gap in the elementary stream — flag
+                // it so the NEXT completed PES carries a discontinuity, matching
+                // every other partial-drop path in this file (lines 395/479/504).
+                self.pending_discontinuity = true;
                 return;
             }
             self.buffer.extend_from_slice(data);
@@ -366,7 +370,7 @@ impl TsDemuxer {
 
         // P3/B1 CONCEALMENT MARKER. The decrypt layer fills an undecryptable
         // aligned unit with NULL-TS packets (PID 0x1FFF) that carry an
-        // adaptation-field discontinuity_indicator (see `aacs::fill_null_ts_unit`).
+        // adaptation-field discontinuity_indicator (see `aacs::content::fill_null_ts_unit`).
         // This is the authoritative loss signal — unlike a tracked PID's 4-bit
         // continuity_counter it is CC-INDEPENDENT, so it survives a loss that is
         // an exact multiple of 16 packets and a loss at the very start of a PID

src/sector/decrypting.rs

@@ -38,16 +38,6 @@ use super::SectorSource;
 /// so it can ride the mux highway's producer thread.
 pub type KeyFetch = std::sync::Arc<dyn Fn(&[Vec<u8>]) -> Vec<[u8; 16]> + Send + Sync>;
 
-/// Cap on how many times one decorator will call the fetch closure over its
-/// lifetime — bounds key-server traffic to roughly O(distinct CPS units) even
-/// if scrambled units keep arriving. A disc has only a handful of unit keys.
-const MAX_FETCH_CALLS: usize = 16;
-
-/// Cap on how many still-scrambled sample units are handed to the fetch
-/// closure per call — a few samples are plenty for a key service to identify
-/// and validate the key, and it bounds the request size.
-const MAX_FETCH_SAMPLES: usize = 8;
-
 /// Cap on how many per-unit decrypt-verify-failure diagnostics one read emits.
 /// The diagnostic runs only on the failure (cold) path and bounds log volume so
 /// a large undecryptable range can't flood the device log; the first few units
@@ -109,21 +99,12 @@ pub struct DecryptingSectorSource<S: SectorSource> {
     ///
     /// [`decrypt_loss`]: Self::decrypt_loss
     decrypt_dropped: Arc<AtomicU64>,
-    /// Optional "fetch a fresh key for THIS data" callback (see [`KeyFetch`]).
-    /// `None` for the common case (keys fully resolved up front); set via
-    /// [`with_key_fetch`](Self::with_key_fetch) by an application that wants
-    /// to ask its key source for a key when a unit fails to decrypt.
-    fetch: Option<KeyFetch>,
-    /// Fingerprints (hash over the unit ciphertext) of failing units a fetch
-    /// already returned NO new key for. A later failure re-asks the source only
-    /// for units NOT in this set — so on a multi-CPS disc the source is still
-    /// asked for the *second* CPS unit's key even after the first came back dry
-    /// (the old global latch blocked that), while the *same* failing unit is
-    /// never re-fetched (and the total is still bounded by `MAX_FETCH_CALLS`).
-    fetch_dry: std::collections::HashSet<u64>,
-    /// How many times the fetch closure has been invoked, capped at
-    /// [`MAX_FETCH_CALLS`].
-    fetch_calls: usize,
+    /// The miss policy (see [`crate::sector::recovery::Recover`]) — a generic,
+    /// scheme-neutral recovery the input stream (L3) installs and this decorator
+    /// (L2) executes at the one seam when a content unit will not decrypt. `None`
+    /// = no recovery (a miss is loss). Installed via
+    /// [`with_key_fetch`](Self::with_key_fetch).
+    recovery: Option<crate::sector::recovery::Recover>,
     /// Verify-only mode: a read decrypt-CHECKS a scratch copy of the bytes (to
     /// detect undecryptable units) but NEVER mutates `buf` — the inner
     /// ciphertext is returned unchanged. This is what makes a multipass sweep
@@ -146,7 +127,7 @@ pub struct DecryptingSectorSource<S: SectorSource> {
     scratch: Vec<u8>,
     /// MUX loss-concealment switch (P3 / Edit-2). When `true`, a content unit
     /// that genuinely won't decrypt is NOT a read failure: it is overwritten with
-    /// valid NULL TS packets ([`crate::aacs::fill_null_ts_unit`]), tallied into
+    /// valid NULL TS packets ([`crate::aacs::content::fill_null_ts_unit`]), tallied into
     /// [`decrypt_dropped`](Self::decrypt_dropped), logged loud with its LBA, and
     /// the read returns `Ok` so the mux KEEPS GOING (it can never abort over an
     /// undecryptable unit). This is the spec's "decrypt-verify is a RIP gate, not
@@ -173,9 +154,10 @@ impl<S: SectorSource> DecryptingSectorSource<S> {
             unit_key_idx: 0,
             unit_base: 0,
             decrypt_dropped: Arc::new(AtomicU64::new(0)),
-            fetch: None,
-            fetch_dry: std::collections::HashSet::new(),
-            fetch_calls: 0,
+            // No recovery by default. CSS self-decrypts in `decrypt_sectors`
+            // (needs no external input); AACS installs a key-fetch via
+            // `with_key_fetch`.
+            recovery: None,
             verify_only: false,
             content_ranges: None,
             scratch: Vec::new(),
@@ -197,7 +179,7 @@ impl<S: SectorSource> DecryptingSectorSource<S> {
     /// (sorted/merged `(start_lba, sector_count)` — see
     /// [`Disc::encrypted_content_ranges`](crate::Disc::encrypted_content_ranges)).
     /// Units outside content (UDF filesystem / BDMV nav) pass through untouched,
-    /// so [`ts_sync_destroyed`](crate::aacs::ts_sync_destroyed) is never consulted
+    /// so [`ts_sync_destroyed`](crate::aacs::content::ts_sync_destroyed) is never consulted
     /// about non-content bytes. Whole-disc readers (sweep / patch) set this; the
     /// mux leaves it unset because it only ever reads title extents.
     pub fn with_content_ranges(mut self, ranges: Arc<[(u32, u32)]>) -> Self {
@@ -238,7 +220,7 @@ impl<S: SectorSource> DecryptingSectorSource<S> {
     /// for [`DecryptKeys::Aacs`]; ignored otherwise. The library makes no network
     /// call — `cb` is the application's seam to its key source.
     pub fn with_key_fetch(mut self, cb: KeyFetch) -> Self {
-        self.fetch = Some(cb);
+        self.recovery = Some(crate::sector::recovery::key_fetch(cb));
         self
     }
 
@@ -286,86 +268,6 @@ impl<S: SectorSource> DecryptingSectorSource<S> {
         }
     }
 
-    /// Collect the still-scrambled aligned units in `buf`, hand them to the
-    /// fetch callback, add any returned keys not already held to the AACS
-    /// pool (the CACHE — every later unit this pass, and any later read, reuses
-    /// them), and re-decrypt `buf`. Returns the post-retry dropped-byte count
-    /// (equal to `prev_dropped` when the callback could not help). The re-decrypt
-    /// is content-gated identically to the first read so a non-content unit is
-    /// never re-attempted. Caller guarantees the keys are `DecryptKeys::Aacs`, a
-    /// callback is installed, and the call budget is not yet spent.
-    fn fetch_failed_units(
-        &mut self,
-        buf: &mut [u8],
-        lba: u32,
-        content: Option<&[(u32, u32)]>,
-        prev_dropped: usize,
-    ) -> usize {
-        let unit_len = crate::aacs::ALIGNED_UNIT_LEN;
-        // Gather up to MAX_FETCH_SAMPLES still-scrambled aligned units — the
-        // exact on-disc ciphertext no held key could open. A trailing partial
-        // unit (chunks_exact remainder) can't be a whole scrambled unit, so
-        // skipping it is correct.
-        let mut samples: Vec<Vec<u8>> = Vec::new();
-        for chunk in buf.chunks_exact(unit_len) {
-            if crate::aacs::aacs_unit_needs_decrypt(chunk) {
-                samples.push(chunk.to_vec());
-                if samples.len() >= MAX_FETCH_SAMPLES {
-                    break;
-                }
-            }
-        }
-        if samples.is_empty() {
-            return prev_dropped;
-        }
-        // Skip the call when EVERY failing unit here is one a prior fetch already
-        // came back empty for — re-asking the identical ciphertext only burns a
-        // key-server request. A unit we have NOT asked about yet (e.g. a second
-        // CPS unit on a multi-CPS disc) still gets its one chance, where the old
-        // global `fetch_spent` latch wrongly blocked it.
-        let fps: Vec<u64> = samples.iter().map(|s| Self::sample_fp(s)).collect();
-        if fps.iter().all(|fp| self.fetch_dry.contains(fp)) {
-            return prev_dropped;
-        }
-        // Ask the application's key source for keys that open this ciphertext.
-        self.fetch_calls += 1;
-        let fresh = match self.fetch.as_ref() {
-            Some(cb) => cb(&samples),
-            None => return prev_dropped,
-        };
-        // Add only keys we don't already hold (dedup by value).
-        let mut added = 0usize;
-        if let DecryptKeys::Aacs { unit_keys, .. } = &mut self.keys {
-            for k in fresh {
-                if !unit_keys.iter().any(|(_, have)| *have == k) {
-                    let idx = unit_keys.len() as u32;
-                    unit_keys.push((idx, k));
-                    added += 1;
-                }
-            }
-        }
-        if added == 0 {
-            // Nothing new for THESE units — remember them so we don't re-ask the
-            // same ciphertext, but leave the door open for other units.
-            self.fetch_dry.extend(fps);
-            return prev_dropped;
-        }
-        // Retry now that the pool has grown; a unit that still won't decrypt is
-        // genuine loss. A retry error must not mask the original count.
-        Self::decrypt_buf(buf, &mut self.keys, self.unit_key_idx, lba, content)
-            .unwrap_or(prev_dropped)
-    }
-
-    /// Stable per-run fingerprint of a failing unit's ciphertext, for the
-    /// `fetch_dry` set. `DefaultHasher` is fixed-seed, so equal samples map to
-    /// equal fingerprints within a process — all the dedup needs.
-    fn sample_fp(sample: &[u8]) -> u64 {
-        use std::hash::{Hash, Hasher};
-        let mut h = std::collections::hash_map::DefaultHasher::new();
-        sample.hash(&mut h);
-        h.finish()
-    }
-
     /// Emit a bounded, structured diagnostic for each undecryptable unit in a
     /// failed verify read. Called only on the failure (cold) path. On a fresh
     /// rip `buf` holds the post-decrypt bytes straight off the drive, so the
@@ -391,7 +293,7 @@ impl<S: SectorSource> DecryptingSectorSource<S> {
         content: Option<&[(u32, u32)]>,
         keys: &DecryptKeys,
     ) {
-        let unit_len = crate::aacs::ALIGNED_UNIT_LEN;
+        let unit_len = crate::aacs::content::ALIGNED_UNIT_LEN;
         let unit_sectors = (unit_len / 2048) as u32;
         // Only AACS produces decrypt-verify failures; None / CSS never reach here
         // with a non-zero dropped count.
@@ -415,12 +317,12 @@ impl<S: SectorSource> DecryptingSectorSource<S> {
             // A unit that decrypted is no longer sync-destroyed; a CPI-clear or
             // non-content unit is gated out. Only undecryptable in-content units
             // that are flagged encrypted carry signal.
-            if !in_content || !crate::aacs::aacs_unit_needs_decrypt(chunk) {
+            if !in_content || !crate::aacs::content::aacs_unit_needs_decrypt(chunk) {
                 continue;
             }
             let all_zero = chunk.iter().all(|&b| b == 0);
-            let ts_sync = crate::aacs::ts_sync_count(chunk);
-            let ts_total = crate::aacs::ts_packet_total(chunk);
+            let ts_sync = crate::aacs::content::ts_sync_count(chunk);
+            let ts_total = crate::aacs::content::ts_packet_total(chunk);
             let mut seen = [false; 256];
             for &b in chunk {
                 seen[b as usize] = true;
@@ -431,10 +333,10 @@ impl<S: SectorSource> DecryptingSectorSource<S> {
             for (_, k) in unit_keys.iter() {
                 let mut attempt = chunk.to_vec();
                 if let Some(ref rdk_key) = rdk {
-                    crate::aacs::decrypt_bus(&mut attempt, rdk_key);
+                    crate::aacs::content::decrypt_bus(&mut attempt, rdk_key);
                 }
-                crate::aacs::decrypt_unit(&mut attempt, k);
-                let s = crate::aacs::ts_sync_count(&attempt);
+                crate::aacs::content::decrypt_unit(&mut attempt, k);
+                let s = crate::aacs::content::ts_sync_count(&attempt);
                 if s > best_sync {
                     best_sync = s;
                 }
@@ -497,7 +399,7 @@ impl<S: SectorSource> SectorSource for DecryptingSectorSource<S> {
         // units (else its readable units are wrongly rejected → "Decryption
         // failed" on exactly those titles).
         if matches!(self.keys, DecryptKeys::Aacs { .. })
-            && !crate::aacs::is_unit_aligned(lba, self.unit_base)
+            && !crate::aacs::content::is_unit_aligned(lba, self.unit_base)
         {
             return Err(crate::error::Error::DecryptFailed);
         }
@@ -521,8 +423,11 @@ impl<S: SectorSource> SectorSource for DecryptingSectorSource<S> {
         // recover a unit no held key opened.
         let content = self.content_ranges.clone(); // cheap Arc bump; frees the &self borrow
         let content_ref = content.as_deref();
-        // Whether a fresh-key fetch is still worth attempting on this decorator.
-        let fetch_viable = self.fetch.is_some() && self.fetch_calls < MAX_FETCH_CALLS;
+        // Copy out the small Copy fields the seam needs, so the `&mut self.recovery`
+        // borrow below does not collide with reads of other `self` fields. The
+        // recovery closure self-limits (its budget lives in its captures), so the
+        // decorator simply calls it whenever there is a miss.
+        let unit_key_idx = self.unit_key_idx;
         // First decrypt, then the FRESH-KEY-ON-FAILURE retry (read → decrypt → on
         // fail fetch a new key → retry → CACHE or fail). This runs in BOTH modes:
         //   * VERIFY-ONLY (multipass sweep): decrypt a reused SCRATCH copy so `buf`
@@ -537,11 +442,11 @@ impl<S: SectorSource> SectorSource for DecryptingSectorSource<S> {
         //   * NORMAL (mux / --no-raw): decrypt `buf` in place, same retry.
         // The fetch re-decrypt targets the post-decrypt buffer (scratch / buf),
         // whose still-scrambled units ARE the failures.
-        let dropped = if self.verify_only {
+        let outcome = if self.verify_only {
             let mut scratch = std::mem::take(&mut self.scratch);
             scratch.clear();
             scratch.extend_from_slice(&buf[..n]);
-            let mut d = match Self::decrypt_buf(
+            let d = match Self::decrypt_buf(
                 &mut scratch,
                 &mut self.keys,
                 self.unit_key_idx,
@@ -554,24 +459,45 @@ impl<S: SectorSource> SectorSource for DecryptingSectorSource<S> {
                     return Err(e);
                 }
             };
-            if d > 0 && fetch_viable {
-                d = self.fetch_failed_units(&mut scratch, lba, content_ref, d);
-            }
+            let o = match (d, self.recovery.as_mut()) {
+                (0, _) | (_, None) => crate::sector::recovery::MissOutcome { dropped: d },
+                (d, Some(r)) => {
+                    let rctx = crate::sector::recovery::RecoverCtx {
+                        unit_key_idx,
+                        lba,
+                        content: content.clone(),
+                        prev_dropped: d,
+                    };
+                    r(&mut scratch, &mut self.keys, &rctx)
+                }
+            };
             self.scratch = scratch;
-            d
+            o
         } else {
-            let mut d = Self::decrypt_buf(
+            let d = Self::decrypt_buf(
                 &mut buf[..n],
                 &mut self.keys,
                 self.unit_key_idx,
                 lba,
                 content_ref,
             )?;
-            if d > 0 && fetch_viable {
-                d = self.fetch_failed_units(&mut buf[..n], lba, content_ref, d);
+            match (d, self.recovery.as_mut()) {
+                (0, _) | (_, None) => crate::sector::recovery::MissOutcome { dropped: d },
+                (d, Some(r)) => {
+                    let rctx = crate::sector::recovery::RecoverCtx {
+                        unit_key_idx,
+                        lba,
+                        content: content.clone(),
+                        prev_dropped: d,
+                    };
+                    r(&mut buf[..n], &mut self.keys, &rctx)
+                }
             }
-            d
         };
+        // A loss is a loss: whatever recovery could not decrypt (a missing unit
+        // key, or an AACS 2.1 forensic-segment unit with no variant key — same
+        // thing to the read path) is concealed and counted the same way.
+        let dropped = outcome.dropped;
         if dropped > 0 {
             self.decrypt_dropped
                 .fetch_add(dropped as u64, Ordering::Relaxed);
@@ -585,7 +511,7 @@ impl<S: SectorSource> SectorSource for DecryptingSectorSource<S> {
             // rip stays fail-loud. Ciphertext is never passed downstream: it is
             // replaced by null packets, not emitted.
             if self.tolerate_decrypt_loss && !self.verify_only {
-                let unit_len = crate::aacs::ALIGNED_UNIT_LEN;
+                let unit_len = crate::aacs::content::ALIGNED_UNIT_LEN;
                 let mut concealed = 0usize;
                 let mut first_lba = lba;
                 for (i, chunk) in buf[..n].chunks_mut(unit_len).enumerate() {
@@ -604,11 +530,12 @@ impl<S: SectorSource> SectorSource for DecryptingSectorSource<S> {
                     // un-restored ciphertext. In-content gating already happened in
                     // `decrypt_buf`, which restored only failed units to ciphertext;
                     // clear nav and decrypted tails pass through clean.
-                    if crate::aacs::aacs_unit_still_ciphertext(chunk) {
+                    if crate::aacs::content::aacs_unit_still_ciphertext(chunk) {
                         if concealed == 0 {
-                            first_lba = lba + (i as u32) * crate::aacs::ALIGNED_UNIT_SECTORS;
+                            first_lba =
+                                lba + (i as u32) * crate::aacs::content::ALIGNED_UNIT_SECTORS;
                         }
-                        crate::aacs::fill_null_ts_unit(chunk);
+                        crate::aacs::content::fill_null_ts_unit(chunk);
                         concealed += 1;
                     }
                 }
@@ -631,8 +558,10 @@ impl<S: SectorSource> SectorSource for DecryptingSectorSource<S> {
                     // flags, loudly. Cryptographically unreachable in practice.
                     let mut forced = 0usize;
                     for chunk in buf[..n].chunks_mut(unit_len) {
-                        if chunk.len() == unit_len && crate::aacs::aacs_unit_needs_decrypt(chunk) {
-                            crate::aacs::fill_null_ts_unit(chunk);
+                        if chunk.len() == unit_len
+                            && crate::aacs::content::aacs_unit_needs_decrypt(chunk)
+                        {
+                            crate::aacs::content::fill_null_ts_unit(chunk);
                             forced += 1;
                         }
                     }
@@ -653,6 +582,11 @@ impl<S: SectorSource> SectorSource for DecryptingSectorSource<S> {
             // fails (no clean data to mux). Scheme-agnostic (only AACS reaches a
             // non-zero count); clear filesystem (gated out) and zero-fill (not
             // scrambled) never get here.
+            //
+            // An undecryptable unit is an undecryptable unit whatever the scheme —
+            // a missing unit key or an AACS 2.1 forensic-segment unit with no
+            // variant key both land here and fail the verify read the same way.
+            // (`dropped > 0` already holds inside the enclosing block.)
             if DECRYPT_VERIFY_READ {
                 // FACT-FINDING: on a fresh rip these bytes came straight off the
                 // drive, so each failing unit's signature (all-zero? entropy?
@@ -1253,12 +1187,12 @@ mod tests {
     }
 
     /// Build a clear 6144-byte AACS unit (TS syncs at the BD-TS stride) then
-    /// encrypt it under `unit_key` so `aacs::decrypt_unit` recovers it. Mirrors
+    /// encrypt it under `unit_key` so `aacs::content::decrypt_unit` recovers it. Mirrors
     /// the encrypt helper in `crate::decrypt`'s tests.
     fn encrypt_aacs_unit(unit_key: &[u8; 16]) -> Vec<u8> {
         use aes::Aes128;
         use aes::cipher::{BlockEncrypt, KeyInit, generic_array::GenericArray};
-        let mut unit = vec![0u8; crate::aacs::ALIGNED_UNIT_LEN];
+        let mut unit = vec![0u8; crate::aacs::content::ALIGNED_UNIT_LEN];
         let mut off = 4;
         while off < unit.len() {
             unit[off] = 0x47;
@@ -1267,14 +1201,14 @@ mod tests {
         // CPI bits on byte 0 so it reads as encrypted; set before key derivation.
         unit[0] |= 0xC0;
         let header: [u8; 16] = unit[..16].try_into().unwrap();
-        let derived = crate::aacs::decrypt::aes_ecb_encrypt(unit_key, &header);
+        let derived = crate::aacs::crypto::aes_ecb_encrypt(unit_key, &header);
         let mut k = [0u8; 16];
         for i in 0..16 {
             k[i] = derived[i] ^ header[i];
         }
         let cipher = Aes128::new(GenericArray::from_slice(&k));
-        let mut prev = crate::aacs::decrypt::AACS_IV;
-        let blocks = (crate::aacs::ALIGNED_UNIT_LEN - 16) / 16;
+        let mut prev = crate::aacs::crypto::AACS_IV;
+        let blocks = (crate::aacs::content::ALIGNED_UNIT_LEN - 16) / 16;
         for i in 0..blocks {
             let o = 16 + i * 16;
             for j in 0..16 {
@@ -1347,7 +1281,7 @@ mod tests {
         );
         assert_eq!(
             loss.load(Ordering::Relaxed),
-            crate::aacs::ALIGNED_UNIT_LEN as u64,
+            crate::aacs::content::ALIGNED_UNIT_LEN as u64,
             "the undecryptable unit is tallied as loss before the read errors"
         );
 
@@ -1358,7 +1292,7 @@ mod tests {
         );
         assert_eq!(
             loss.load(Ordering::Relaxed),
-            2 * crate::aacs::ALIGNED_UNIT_LEN as u64,
+            2 * crate::aacs::content::ALIGNED_UNIT_LEN as u64,
             "loss must accumulate across reads"
         );
 
@@ -1392,7 +1326,7 @@ mod tests {
         // One unit encrypted under real_key, plus one trailing CLEAR (TS-sync)
         // unit so we can confirm conceal touches ONLY the undecryptable unit.
         let enc = encrypt_aacs_unit(&real_key);
-        let mut clear = vec![0u8; crate::aacs::ALIGNED_UNIT_LEN];
+        let mut clear = vec![0u8; crate::aacs::content::ALIGNED_UNIT_LEN];
         let mut o = 4;
         while o < clear.len() {
             clear[o] = 0x47;
@@ -1441,13 +1375,13 @@ mod tests {
         // The undecryptable unit is tallied as loss.
         assert_eq!(
             loss.load(Ordering::Relaxed),
-            crate::aacs::ALIGNED_UNIT_LEN as u64,
+            crate::aacs::content::ALIGNED_UNIT_LEN as u64,
             "the concealed unit is still counted as loss"
         );
 
         // Unit 0 is now valid NULL TS packets — sync 0x47 at every 192-byte
         // stride (offset 4), PID 0x1FFF — and carries no ciphertext.
-        let unit0 = &buf[..crate::aacs::ALIGNED_UNIT_LEN];
+        let unit0 = &buf[..crate::aacs::content::ALIGNED_UNIT_LEN];
         let mut off = 0;
         while off + 192 <= unit0.len() {
             assert_eq!(unit0[off + 4], 0x47, "null packet sync at {off}");
@@ -1456,12 +1390,13 @@ mod tests {
             off += 192;
         }
         assert!(
-            !crate::aacs::ts_sync_destroyed(unit0),
+            !crate::aacs::content::ts_sync_destroyed(unit0),
             "concealed unit reads as well-formed TS, not scrambled"
         );
 
         // Unit 1 (clear) passed through untouched.
-        let unit1 = &buf[crate::aacs::ALIGNED_UNIT_LEN..2 * crate::aacs::ALIGNED_UNIT_LEN];
+        let unit1 = &buf
+            [crate::aacs::content::ALIGNED_UNIT_LEN..2 * crate::aacs::content::ALIGNED_UNIT_LEN];
         assert_eq!(unit1, &clear[..], "the clear unit is left exactly as read");
     }
 
@@ -1496,7 +1431,7 @@ mod tests {
         // The byte-exact expected post-decrypt form of unit B (independent decrypt).
         let mut expected_tail = good_tail.clone();
         assert!(
-            crate::aacs::decrypt_unit(&mut expected_tail, &good_key),
+            crate::aacs::content::decrypt_unit(&mut expected_tail, &good_key),
             "padding-tail must decrypt under good_key"
         );
 
@@ -1542,12 +1477,12 @@ mod tests {
         // ONLY the genuinely-undecryptable unit A is tallied / concealed.
         assert_eq!(
             loss.load(Ordering::Relaxed),
-            crate::aacs::ALIGNED_UNIT_LEN as u64,
+            crate::aacs::content::ALIGNED_UNIT_LEN as u64,
             "exactly one unit (the undecryptable one) is counted as loss"
         );
 
         // Unit A → NULL TS (concealed).
-        let unit0 = &buf[..crate::aacs::ALIGNED_UNIT_LEN];
+        let unit0 = &buf[..crate::aacs::content::ALIGNED_UNIT_LEN];
         let mut off = 0;
         while off + 192 <= unit0.len() {
             assert_eq!(unit0[off + 4], 0x47, "unit A null packet sync at {off}");
@@ -1562,7 +1497,8 @@ mod tests {
         // Unit B → the GOOD decrypted padding tail, byte-for-byte intact (NOT
         // overwritten with NULL TS). This is the silent-data-loss the old
         // majority-vote predicate caused.
-        let unit1 = &buf[crate::aacs::ALIGNED_UNIT_LEN..2 * crate::aacs::ALIGNED_UNIT_LEN];
+        let unit1 = &buf
+            [crate::aacs::content::ALIGNED_UNIT_LEN..2 * crate::aacs::content::ALIGNED_UNIT_LEN];
         assert_eq!(
             unit1,
             &expected_tail[..],
@@ -1587,8 +1523,8 @@ mod tests {
     /// `mux::ts` reads as a concealed gap.
     #[test]
     fn null_ts_fill_is_well_formed_and_invisible_to_real_pids() {
-        let mut unit = vec![0xAAu8; crate::aacs::ALIGNED_UNIT_LEN];
-        crate::aacs::fill_null_ts_unit(&mut unit);
+        let mut unit = vec![0xAAu8; crate::aacs::content::ALIGNED_UNIT_LEN];
+        crate::aacs::content::fill_null_ts_unit(&mut unit);
         // 32 packets, each: sync 0x47, PID 0x1FFF, adaptation-only (0b10) with a
         // discontinuity_indicator in the adaptation field.
         let mut off = 0;
@@ -1679,7 +1615,7 @@ mod tests {
             "callback must be invoked once with the failing unit"
         );
         assert!(
-            crate::aacs::ts_sync_destroyed(&got[0]),
+            crate::aacs::content::ts_sync_destroyed(&got[0]),
             "the sample handed to the callback is the still-scrambled ciphertext"
         );
         assert_eq!(
@@ -1703,7 +1639,7 @@ mod tests {
         );
         assert_eq!(
             nocb_loss.load(Ordering::Relaxed),
-            crate::aacs::ALIGNED_UNIT_LEN as u64,
+            crate::aacs::content::ALIGNED_UNIT_LEN as u64,
             "without a fetch callback the undecryptable unit is loss"
         );
     }
@@ -1784,7 +1720,7 @@ mod tests {
             "fetch fired for BOTH units — the dry result for A did not latch off B"
         );
         assert!(
-            !crate::aacs::ts_sync_destroyed(&buf2),
+            !crate::aacs::content::ts_sync_destroyed(&buf2),
             "unit B is decrypted after its on-demand fetch"
         );
     }
@@ -1899,7 +1835,7 @@ mod tests {
                 let mut u = 0;
                 while u < bytes {
                     buf[u] |= 0xC0;
-                    u += crate::aacs::ALIGNED_UNIT_LEN;
+                    u += crate::aacs::content::ALIGNED_UNIT_LEN;
                 }
                 Ok(bytes)
             }
@@ -1998,7 +1934,7 @@ mod tests {
                 let mut u = 0;
                 while u < b {
                     buf[u] |= 0xC0; // CPI bits → reads as encrypted
-                    u += crate::aacs::ALIGNED_UNIT_LEN;
+                    u += crate::aacs::content::ALIGNED_UNIT_LEN;
                 }
                 Ok(b)
             }

src/sector/mod.rs

@@ -16,6 +16,7 @@
 pub mod decrypting;
 pub mod file;
 pub mod prefetched;
+pub mod recovery;
 
 use crate::error::Result;
 

src/sector/prefetched.rs

@@ -358,7 +358,6 @@ impl PrefetchedSectorSource {
         // and suppresses `self`'s own `Drop` (which would otherwise
         // double-`join`), leaving NO extra live endpoint behind. This
         // is the panic-free equivalent of the `Option::take` approach.
-        let total = self.total_sectors;
         let me = std::mem::ManuallyDrop::new(self);
         // SAFETY: `me` is `ManuallyDrop`, so none of these fields will
         // be dropped by `me`. Each `ptr::read` performs exactly one
@@ -367,7 +366,7 @@ impl PrefetchedSectorSource {
         let producer = unsafe { std::ptr::read(&me.producer) };
         let rx = unsafe { std::ptr::read(&me.rx) };
         let recycle = unsafe { std::ptr::read(&me.recycle_tx) };
-        (rx, recycle, PrefetchShell { producer, total })
+        (rx, recycle, PrefetchShell { producer })
     }
 }
 
@@ -376,8 +375,6 @@ impl PrefetchedSectorSource {
 /// producer, even though the channels have been peeled off.
 pub struct PrefetchShell {
     producer: Option<JoinHandle<()>>,
-    #[allow(dead_code)]
-    total: u32,
 }
 
 impl Drop for PrefetchShell {

src/sector/recovery.rs

@@ -0,0 +1,330 @@
+//! The recovery seam: what a read does when a content unit will not decrypt.
+//!
+//! Per-format miss policy does NOT belong in the generic decrypt decorator
+//! (L2). The input stream (L3, e.g. [`crate::mux::disc::DiscStream`]) knows what
+//! it is reading and installs a [`Recover`] at construction; the decorator
+//! executes it at the one seam and honours the returned outcome. This keeps
+//! "a DVD re-cracks, a BD/UHD fetches a fresh key" out of the decryptor, where
+//! it would otherwise smear across `if`-branches.
+//!
+//! The recovery type ([`Recover`]) names **no encryption scheme**. It is a
+//! generic `FnMut(&mut [u8], &mut DecryptKeys, &RecoverCtx) -> MissOutcome` that
+//! operates on the generic [`DecryptKeys`] the whole decrypt path already uses,
+//! so a scheme is never baked into the type — only into the factory that builds
+//! a recovery:
+//!   * [`none`] — no recovery; a miss is loss (raw sweep / clear).
+//!   * [`key_fetch`] — AACS key-fetch: hand the failing ciphertext to the
+//!     application's key source and add any returned keys to the pool. An AACS
+//!     2.1 forensic-segment unit that no key opens is just an undecryptable unit
+//!     like any other — a loss is a loss, with no FMTS-specific branch here.
+//!
+//! CSS is deliberately NOT on this seam — and the reason is precise: this seam is
+//! for recovery that needs something `decrypt_sectors` does not have (an EXTERNAL
+//! key source for AACS, a segment map for FMTS). CSS's title key changes per VOB
+//! region and is re-cracked constantly, but always FROM THE DATA ITSELF — no
+//! external input — so CSS SELF-recovers inside `decrypt_sectors` (see
+//! [`crate::css::descramble_region`]). The generic type here would accept a CSS
+//! recovery, but CSS has no reason to use it.
+
+use crate::decrypt::DecryptKeys;
+use crate::sector::KeyFetch;
+use std::collections::HashSet;
+use std::sync::Arc;
+
+/// The result of running a recovery on a read's still-scrambled units: how many
+/// bytes remain loss after recovery ran. A loss is a loss — an undecryptable
+/// unit is concealed and counted the same whatever the scheme (an AACS 2.1
+/// forensic-segment unit with no variant key is just another undecryptable
+/// unit).
+#[derive(Debug, Clone, Copy, Default, PartialEq, Eq)]
+pub struct MissOutcome {
+    /// Bytes that remain loss after recovery.
+    pub dropped: usize,
+}
+
+impl MissOutcome {
+    /// All `n` bytes are loss.
+    fn loss(n: usize) -> Self {
+        Self { dropped: n }
+    }
+}
+
+/// Cap on how many times one recovery will call its fetch closure over its
+/// lifetime — bounds key-server traffic to ~O(distinct CPS units) even if
+/// scrambled units keep arriving. A disc has only a handful of unit keys.
+const MAX_FETCH_CALLS: usize = 16;
+
+/// Cap on how many still-scrambled sample units are handed to the fetch closure
+/// per call — a few samples suffice for a key service to identify and validate
+/// the key, and it bounds the request size.
+const MAX_FETCH_SAMPLES: usize = 8;
+
+/// Stable per-run fingerprint of a failing unit's ciphertext, for the dedup set.
+/// `DefaultHasher` is fixed-seed, so equal samples map to equal fingerprints
+/// within a process — all the dedup needs.
+fn sample_fp(sample: &[u8]) -> u64 {
+    use std::hash::{Hash, Hasher};
+    let mut h = std::collections::hash_map::DefaultHasher::new();
+    sample.hash(&mut h);
+    h.finish()
+}
+
+/// Re-decrypt `buf` after the key pool grew, content-gated identically to the
+/// first read so a non-content unit is never re-attempted. Mirrors the
+/// decorator's `decrypt_buf` dispatch.
+fn redecrypt(
+    buf: &mut [u8],
+    keys: &mut DecryptKeys,
+    unit_key_idx: usize,
+    lba: u32,
+    content: Option<&[(u32, u32)]>,
+    prev_dropped: usize,
+) -> usize {
+    match content {
+        Some(ranges) => {
+            crate::decrypt::decrypt_sectors_in_content(buf, keys, unit_key_idx, lba, ranges)
+        }
+        None => crate::decrypt::decrypt_sectors(buf, keys, unit_key_idx),
+    }
+    .unwrap_or(prev_dropped)
+}
+
+/// What a read hands a recovery on a miss: the disc's decrypt parameters and how
+/// many bytes the held keys could not decrypt. Scheme-neutral — a recovery reads
+/// only the generic [`DecryptKeys`] and these fields.
+pub struct RecoverCtx {
+    /// Which AACS unit-key index the read decrypts with (ignored by non-AACS).
+    pub unit_key_idx: usize,
+    /// Base LBA of the read.
+    pub lba: u32,
+    /// The encrypted-content extent map, when the read is content-gated.
+    pub content: Option<Arc<[(u32, u32)]>>,
+    /// Bytes the held keys could not decrypt before recovery ran.
+    pub prev_dropped: usize,
+}
+
+/// A recovery: given a read's still-scrambled `buf` and the **generic**
+/// [`DecryptKeys`], make units decrypt (crack or fetch a key into `keys`) and/or
+/// classify the loss (see [`MissOutcome`]). The type names NO encryption scheme
+/// — the installed recovery decides what to do with the generic keys, so any
+/// scheme (an AACS key-fetch, a future CSS re-crack) is just a different
+/// [`Recover`] the input stream installs. `FnMut` so per-recovery
+/// state (the AACS dedup set / call budget) lives in the closure's captures with
+/// no lock; `Send` so it can ride the mux highway's producer thread.
+pub type Recover = Box<dyn FnMut(&mut [u8], &mut DecryptKeys, &RecoverCtx) -> MissOutcome + Send>;
+
+/// The AACS key-fetch step used by [`key_fetch`]: gather the
+/// still-scrambled units, ask `fetch` for keys, add any new ones to the pool and
+/// re-decrypt. `dry` / `calls` are the caller-owned dedup set and call budget.
+/// Returns the post-retry dropped-byte count.
+fn aacs_fetch_step(
+    dry: &mut HashSet<u64>,
+    calls: &mut usize,
+    fetch: &KeyFetch,
+    buf: &mut [u8],
+    keys: &mut DecryptKeys,
+    ctx: &RecoverCtx,
+) -> usize {
+    let prev_dropped = ctx.prev_dropped;
+    if *calls >= MAX_FETCH_CALLS {
+        return prev_dropped;
+    }
+    let unit_len = crate::aacs::content::ALIGNED_UNIT_LEN;
+    // Gather up to MAX_FETCH_SAMPLES still-scrambled aligned units — the exact
+    // on-disc ciphertext no held key could open. A trailing partial unit
+    // (chunks_exact remainder) can't be a whole scrambled unit, so skipping it is
+    // correct.
+    let mut samples: Vec<Vec<u8>> = Vec::new();
+    for chunk in buf.chunks_exact(unit_len) {
+        if crate::aacs::content::aacs_unit_needs_decrypt(chunk) {
+            samples.push(chunk.to_vec());
+            if samples.len() >= MAX_FETCH_SAMPLES {
+                break;
+            }
+        }
+    }
+    if samples.is_empty() {
+        return prev_dropped;
+    }
+    // Skip the call when EVERY failing unit here is one a prior fetch already
+    // came back empty for — re-asking identical ciphertext only burns a request.
+    // A unit not asked about yet (e.g. a second CPS unit) still gets its chance.
+    let fps: Vec<u64> = samples.iter().map(|s| sample_fp(s)).collect();
+    if fps.iter().all(|fp| dry.contains(fp)) {
+        return prev_dropped;
+    }
+    *calls += 1;
+    let fresh = (fetch)(&samples);
+    // Add only keys we don't already hold (dedup by value).
+    let mut added = 0usize;
+    if let DecryptKeys::Aacs { unit_keys, .. } = keys {
+        for k in fresh {
+            if !unit_keys.iter().any(|(_, have)| *have == k) {
+                let idx = unit_keys.len() as u32;
+                unit_keys.push((idx, k));
+                added += 1;
+            }
+        }
+    }
+    if added == 0 {
+        // Nothing new for THESE units — remember them so we don't re-ask the same
+        // ciphertext, but leave the door open for other units.
+        dry.extend(fps);
+        return prev_dropped;
+    }
+    // Retry now that the pool has grown; a unit that still won't decrypt is
+    // genuine loss. A retry error must not mask the original count.
+    redecrypt(
+        buf,
+        keys,
+        ctx.unit_key_idx,
+        ctx.lba,
+        ctx.content.as_deref(),
+        prev_dropped,
+    )
+}
+
+/// No recovery: a miss is loss. Equivalent to installing nothing — provided so a
+/// caller that wants an explicit "give up" recovery has one.
+pub fn none() -> Recover {
+    Box::new(|_buf, _keys, ctx| MissOutcome::loss(ctx.prev_dropped))
+}
+
+/// AACS key-fetch recovery (BD / UHD): on a miss, ask the application's key
+/// source for a key that opens the failing ciphertext and add it to the pool.
+pub fn key_fetch(fetch: KeyFetch) -> Recover {
+    let mut dry: HashSet<u64> = HashSet::new();
+    let mut calls: usize = 0;
+    Box::new(move |buf, keys, ctx| {
+        MissOutcome::loss(aacs_fetch_step(
+            &mut dry, &mut calls, &fetch, buf, keys, ctx,
+        ))
+    })
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use crate::aacs::content::ALIGNED_UNIT_LEN;
+    use std::sync::Arc;
+    use std::sync::atomic::{AtomicUsize, Ordering};
+
+    /// A 6144-byte aligned unit that reads as still-scrambled: CPI bits set on
+    /// byte 0 (so `aacs_unit_encrypted` flags it) and every 192-byte TS-sync
+    /// probe position forced off 0x47. `tag` varies the whole body so distinct
+    /// tags produce distinct fingerprints (mirrors decrypt.rs `scrambled_region`).
+    fn scrambled_unit(tag: u8) -> Vec<u8> {
+        let len = ALIGNED_UNIT_LEN;
+        let mut v: Vec<u8> = (0..len).map(|i| (i as u8).wrapping_mul(31) ^ tag).collect();
+        let mut off = 4;
+        while off < len {
+            v[off] = 0xA5; // never a 0x47 sync
+            off += 192;
+        }
+        v[0] |= 0xC0; // CPI: reads as encrypted content
+        v
+    }
+
+    /// A recovery context reading at clip-relative `lba` with `prev` bytes the
+    /// held keys could not decrypt.
+    fn ctx(lba: u32, prev: usize) -> RecoverCtx {
+        RecoverCtx {
+            unit_key_idx: 0,
+            lba,
+            content: None,
+            prev_dropped: prev,
+        }
+    }
+
+    #[test]
+    fn none_recovers_nothing() {
+        let mut r = none();
+        let mut buf = scrambled_unit(0x33);
+        let mut keys = DecryptKeys::Aacs {
+            unit_keys: vec![],
+            read_data_key: None,
+        };
+        let out = r(&mut buf, &mut keys, &ctx(0, 6144));
+        assert_eq!(out.dropped, 6144);
+    }
+
+    #[test]
+    fn key_fetch_adds_returned_keys_to_the_pool() {
+        // The fetch returns one key; it must be appended to the (empty) pool. We
+        // assert the pool grew (the decrypt itself is exercised end-to-end by the
+        // decorator's integration tests); here we pin the seam's key-plumbing.
+        let calls = Arc::new(AtomicUsize::new(0));
+        let c2 = Arc::clone(&calls);
+        let fetch: KeyFetch = Arc::new(move |samples: &[Vec<u8>]| {
+            c2.fetch_add(1, Ordering::SeqCst);
+            assert!(!samples.is_empty(), "failing ciphertext is forwarded");
+            vec![[0xAB; 16]]
+        });
+        let mut r = key_fetch(fetch);
+        let mut buf = scrambled_unit(0x33);
+        let mut keys = DecryptKeys::Aacs {
+            unit_keys: vec![],
+            read_data_key: None,
+        };
+        r(&mut buf, &mut keys, &ctx(0, ALIGNED_UNIT_LEN));
+        assert_eq!(calls.load(Ordering::SeqCst), 1, "fetch called once");
+        let DecryptKeys::Aacs { unit_keys, .. } = &keys else {
+            unreachable!()
+        };
+        assert_eq!(unit_keys.len(), 1, "returned key added to the pool");
+        assert_eq!(unit_keys[0].1, [0xAB; 16]);
+    }
+
+    #[test]
+    fn key_fetch_does_not_re_ask_dry_ciphertext() {
+        // A fetch that returns nothing marks the ciphertext dry; a second miss on
+        // the SAME ciphertext must not call the fetch again.
+        let calls = Arc::new(AtomicUsize::new(0));
+        let c2 = Arc::clone(&calls);
+        let fetch: KeyFetch = Arc::new(move |_: &[Vec<u8>]| {
+            c2.fetch_add(1, Ordering::SeqCst);
+            Vec::new() // never helps
+        });
+        let mut r = key_fetch(fetch);
+        let mut keys = DecryptKeys::Aacs {
+            unit_keys: vec![],
+            read_data_key: None,
+        };
+        let mut buf = scrambled_unit(0x44);
+        r(&mut buf, &mut keys, &ctx(0, ALIGNED_UNIT_LEN));
+        let mut buf2 = scrambled_unit(0x44); // identical ciphertext
+        r(&mut buf2, &mut keys, &ctx(0, ALIGNED_UNIT_LEN));
+        assert_eq!(
+            calls.load(Ordering::SeqCst),
+            1,
+            "identical dry ciphertext is not re-asked"
+        );
+    }
+
+    #[test]
+    fn key_fetch_call_budget_bounds_fetches() {
+        let calls = Arc::new(AtomicUsize::new(0));
+        let c2 = Arc::clone(&calls);
+        let fetch: KeyFetch = Arc::new(move |_: &[Vec<u8>]| {
+            c2.fetch_add(1, Ordering::SeqCst);
+            Vec::new()
+        });
+        let mut r = key_fetch(fetch);
+        let mut keys = DecryptKeys::Aacs {
+            unit_keys: vec![],
+            read_data_key: None,
+        };
+        // Distinct ciphertext each time so the dry-set never short-circuits; only
+        // the internal call budget should stop the fetch. The closure self-limits,
+        // so the decorator can call it unconditionally.
+        for i in 0..(MAX_FETCH_CALLS as u8 + 5) {
+            let mut buf = scrambled_unit(i);
+            r(&mut buf, &mut keys, &ctx(0, ALIGNED_UNIT_LEN));
+        }
+        assert_eq!(
+            calls.load(Ordering::SeqCst),
+            MAX_FETCH_CALLS,
+            "fetch is capped at MAX_FETCH_CALLS"
+        );
+    }
+}

src/udf.rs

@@ -325,53 +325,6 @@ impl UdfFs {
         Ok(merged)
     }
 
-    /// All sector ranges that contain data (metadata + all files including STREAM).
-    /// For full disc-to-ISO dumps — reads only allocated sectors, skips gaps.
-    pub fn all_sector_ranges(&self, reader: &mut dyn SectorSource) -> Result<Vec<(u32, u32)>> {
-        let mut ranges = Vec::new();
-
-        // UDF structure sectors
-        let meta_end = self.metadata_start.saturating_add(self.metadata_sectors);
-        ranges.push((0, meta_end));
-
-        // Walk entire tree including STREAM directories
-        self.collect_all_file_ranges(reader, &self.root, &mut ranges)?;
-
-        // Merge overlapping/adjacent ranges and sort
-        ranges.sort_by_key(|r| r.0);
-        let merged = merge_ranges(&ranges);
-        Ok(merged)
-    }
-
-    fn collect_all_file_ranges(
-        &self,
-        reader: &mut dyn SectorSource,
-        entry: &DirEntry,
-        ranges: &mut Vec<(u32, u32)>,
-    ) -> Result<()> {
-        for child in &entry.entries {
-            if child.is_dir {
-                self.collect_all_file_ranges(reader, child, ranges)?;
-            } else {
-                // Include the ICB sector
-                ranges.push((self.meta_to_abs(child.meta_lba)?, 1));
-
-                // Include ALL file data extents (large m2ts files have many)
-                if let Ok(extents) = self.read_icb_extents(reader, child.meta_lba) {
-                    for (data_lba, data_len) in extents {
-                        let abs_start = match self.partition_start.checked_add(data_lba) {
-                            Some(v) => v,
-                            None => continue,
-                        };
-                        let sector_count = (data_len as u64).div_ceil(2048) as u32;
-                        ranges.push((abs_start, sector_count));
-                    }
-                }
-            }
-        }
-        Ok(())
-    }
-
     fn collect_file_ranges(
         &self,
         reader: &mut dyn SectorSource,
@@ -640,10 +593,27 @@ impl UdfFs {
             match next_block {
                 Some(cont_lba) => {
                     read_sector(reader, self.meta_to_abs(cont_lba)?, &mut block)?;
-                    // A continuation block is a list of Short ADs from byte 0,
-                    // spanning the whole sector.
-                    ad_start = 0;
-                    ad_bytes = block.len();
+                    // A continuation block does NOT begin with allocation
+                    // descriptors — it begins with a 24-byte Allocation Extent
+                    // Descriptor (ECMA-167 4/14.5, tag id 258): the 16-byte
+                    // descriptor tag, then prev_allocation_extent_location
+                    // (Uint32 @16) and length_of_allocation_descriptors
+                    // (Uint32 @20). The real ADs (same Short/Long/Extended type
+                    // as the file) start at offset 24, and their total byte
+                    // length is that @20 field.
+                    //
+                    // Reading from offset 0 parses the AED's own tag header as
+                    // allocation descriptors → one garbage extent, then an
+                    // unknown extent_type break — silently truncating every
+                    // file whose ADs spill into a continuation block (a heavily
+                    // fragmented file, e.g. a Blu-ray 3D interleaved base-view
+                    // .m2ts with ~1600 fragments). A normal few-extent .m2ts
+                    // fits inline and never reaches here, which is why this
+                    // stayed hidden.
+                    let aed_l_ad =
+                        u32::from_le_bytes([block[20], block[21], block[22], block[23]]) as usize;
+                    ad_start = 24;
+                    ad_bytes = aed_l_ad.min(block.len().saturating_sub(24));
                 }
                 None => break,
             }
@@ -1582,8 +1552,15 @@ mod tests {
 
     /// A continuation block: a bare list of short ADs from byte 0.
     fn build_cont_block(ads: &[(u32, u32, u32)]) -> [u8; 2048] {
+        // A continuation block is an Allocation Extent Descriptor (ECMA-167
+        // 4/14.5): a 16-byte descriptor tag, then prev_allocation_extent_location
+        // (Uint32 @16) and length_of_allocation_descriptors (Uint32 @20). The
+        // actual allocation descriptors begin at offset 24. The parser skips the
+        // 24-byte header and reads `l_ad` bytes of ADs from there.
         let mut s = [0u8; 2048];
-        let mut off = 0usize;
+        let l_ad = (ads.len() * 8) as u32;
+        s[20..24].copy_from_slice(&l_ad.to_le_bytes());
+        let mut off = 24usize;
         for &(etype, dlen, dlba) in ads {
             let raw_len = (etype << 30) | (dlen & 0x3FFF_FFFF);
             s[off..off + 4].copy_from_slice(&raw_len.to_le_bytes());
@@ -1637,6 +1614,35 @@ mod tests {
         assert_eq!(extents, vec![(10, 4096), (20, 2048)]);
     }
 
+    #[test]
+    fn icb_extents_continuation_skips_aed_header_not_read_as_extent() {
+        // Regression (Blu-ray 3D): a continuation block begins with a 24-byte
+        // Allocation Extent Descriptor whose 16-byte descriptor tag holds
+        // NON-zero bytes (tag id 258, CRC, location, ...). Reading allocation
+        // descriptors from offset 0 parses that tag header as an AD → a garbage
+        // extent, then an unknown extent_type break → every fragment past the
+        // first continuation is lost. On a 3D disc that truncated the 25.8 GB
+        // interleaved base-view feature to ~1.8 GB (113 of ~1600 fragments) and
+        // then choked the mux on the bogus, non-unit-aligned extent. The parser
+        // MUST skip the 24-byte AED header and read the real ADs from offset 24.
+        let icb = build_efe(6144, &[(0, 4096, 10), (3, 2048, 50)]);
+        let mut cont = build_cont_block(&[(0, 2048, 20)]);
+        // Stamp a realistic AED descriptor tag (id 258) into the header so a
+        // regression that reads from offset 0 mis-parses it as a bogus extent
+        // instead of finding the real (20, 2048) at offset 24.
+        cont[0..2].copy_from_slice(&258u16.to_le_bytes());
+        let mut reader = MapReader::new();
+        reader.put(5, icb);
+        reader.put(50, cont);
+        let fs = fs_with(0, 0, file_entry("3D", 5, 6144));
+        let extents = fs.read_icb_extents(&mut reader, 5).expect("extents");
+        assert_eq!(
+            extents,
+            vec![(10, 4096), (20, 2048)],
+            "continuation ADs must be read past the 24-byte AED header, not from offset 0"
+        );
+    }
+
     #[test]
     fn icb_extents_long_ad_returns_all_extents_not_just_first() {
         // Regression: BD-ROM large .m2ts files use Long ADs (16-byte
@@ -2391,3 +2397,224 @@ mod tests {
         );
     }
 }
+
+/// Shared UDF image fixtures for tests across the `disc::*` format scanners.
+///
+/// Builds an in-memory disc image that [`read_filesystem`] can navigate — a
+/// [`MemDisc`] SectorSource plus a [`DirSpec`] tree laid out via [`lay_dir`] and
+/// [`build_udf_skeleton`]. Format-agnostic: BD (`bluray.rs`), HD-DVD
+/// (`hddvd.rs`), and the format detector (`disc/mod.rs`) all build their own
+/// trees (`BDMV/`, `HVDVD_TS/`, `AACS/…`) on top of these primitives, so each
+/// format's tests live in that format's file, not piled into one.
+#[cfg(test)]
+pub(crate) mod fixture {
+    use crate::sector::SectorSource;
+    use std::collections::HashMap;
+
+    /// PART_START == META_START: file LBAs (partition-relative) and ICB/dir LBAs
+    /// (metadata-relative) share one address space (abs = PART_START + lba), so
+    /// `read_filesystem` takes the single-partition path.
+    pub(crate) const PART_START: u32 = 2000;
+
+    /// In-memory `SectorSource` (absolute-LBA → 2048-byte sector map); unmapped
+    /// sectors read as zeroes.
+    pub(crate) struct MemDisc {
+        sectors: HashMap<u32, [u8; 2048]>,
+    }
+
+    impl MemDisc {
+        pub(crate) fn new() -> Self {
+            Self {
+                sectors: HashMap::new(),
+            }
+        }
+        fn put(&mut self, lba: u32, data: [u8; 2048]) {
+            self.sectors.insert(lba, data);
+        }
+        /// Write arbitrary-length bytes at `lba`, split across 2048-byte sectors.
+        pub(crate) fn put_bytes(&mut self, lba: u32, bytes: &[u8]) {
+            for (i, chunk) in bytes.chunks(2048).enumerate() {
+                let mut s = [0u8; 2048];
+                s[..chunk.len()].copy_from_slice(chunk);
+                self.put(lba + i as u32, s);
+            }
+        }
+    }
+
+    impl SectorSource for MemDisc {
+        fn read_sectors(
+            &mut self,
+            lba: u32,
+            count: u16,
+            buf: &mut [u8],
+            _recovery: bool,
+        ) -> crate::error::Result<usize> {
+            let need = count as usize * 2048;
+            for i in 0..count as u32 {
+                let off = i as usize * 2048;
+                let s = self.sectors.get(&(lba + i)).copied().unwrap_or([0u8; 2048]);
+                buf[off..off + 2048].copy_from_slice(&s);
+            }
+            Ok(need)
+        }
+    }
+
+    /// One file's placement: ICB metadata LBA, data-extent LBA, byte length,
+    /// Long-AD (16-byte, real BD-ROM layout) vs Short-AD, optional contents.
+    pub(crate) struct FileSpec {
+        pub(crate) name: String,
+        pub(crate) icb_lba: u32,
+        pub(crate) data_lba: u32,
+        pub(crate) size: u32,
+        pub(crate) long_ad: bool,
+        pub(crate) contents: Vec<u8>,
+    }
+
+    /// A directory node: ICB LBA, FID-list LBA, child files and subdirectories.
+    pub(crate) struct DirSpec {
+        pub(crate) name: String,
+        pub(crate) icb_lba: u32,
+        pub(crate) dir_data_lba: u32,
+        pub(crate) files: Vec<FileSpec>,
+        pub(crate) subdirs: Vec<DirSpec>,
+    }
+
+    /// Build an Extended File Entry ICB (tag 266) with one allocation descriptor.
+    pub(crate) fn build_file_icb(size: u32, data_lba: u32, long_ad: bool) -> [u8; 2048] {
+        let mut s = [0u8; 2048];
+        s[0..2].copy_from_slice(&266u16.to_le_bytes()); // Extended File Entry
+        if long_ad {
+            s[34..36].copy_from_slice(&1u16.to_le_bytes()); // ICB flags → Long AD
+        }
+        s[56..64].copy_from_slice(&(size as u64).to_le_bytes()); // info_length
+        s[208..212].copy_from_slice(&0u32.to_le_bytes()); // l_ea
+        let ad_size: u32 = if long_ad { 16 } else { 8 };
+        s[212..216].copy_from_slice(&ad_size.to_le_bytes()); // l_ad
+        s[216..220].copy_from_slice(&(size & 0x3FFF_FFFF).to_le_bytes());
+        s[220..224].copy_from_slice(&data_lba.to_le_bytes());
+        s
+    }
+
+    fn build_dir_icb(dir_data_lba: u32, dir_data_len: u32) -> [u8; 2048] {
+        build_file_icb(dir_data_len, dir_data_lba, false)
+    }
+
+    /// Append one File Identifier Descriptor (tag 257) to `buf`.
+    fn push_fid(buf: &mut Vec<u8>, name: &str, icb_lba: u32, is_dir: bool, is_parent: bool) {
+        let start = buf.len();
+        let name_field: Vec<u8> = if is_parent {
+            Vec::new()
+        } else {
+            let mut v = vec![0x08u8];
+            v.extend_from_slice(name.as_bytes());
+            v
+        };
+        let l_fi = name_field.len();
+        let mut fid = vec![0u8; 38];
+        fid[0..2].copy_from_slice(&257u16.to_le_bytes()); // FID tag
+        let mut file_chars = 0u8;
+        if is_dir {
+            file_chars |= 0x02;
+        }
+        if is_parent {
+            file_chars |= 0x08;
+        }
+        fid[18] = file_chars;
+        fid[19] = l_fi as u8;
+        fid[24..28].copy_from_slice(&icb_lba.to_le_bytes()); // ICB long_ad LBA @24
+        fid[36..38].copy_from_slice(&0u16.to_le_bytes()); // l_iu @36
+        buf.extend_from_slice(&fid);
+        buf.extend_from_slice(&name_field);
+        let used = buf.len() - start;
+        let pad = (used + 3) & !3;
+        buf.resize(start + pad, 0);
+    }
+
+    /// Recursively lay a [`DirSpec`] into the [`MemDisc`].
+    pub(crate) fn lay_dir(disc: &mut MemDisc, dir: &DirSpec) {
+        let mut fids = Vec::new();
+        push_fid(&mut fids, "", dir.icb_lba, true, true);
+        for f in &dir.files {
+            push_fid(&mut fids, &f.name, f.icb_lba, false, false);
+            disc.put(
+                PART_START + f.icb_lba,
+                build_file_icb(f.size, f.data_lba, f.long_ad),
+            );
+            if !f.contents.is_empty() {
+                disc.put_bytes(PART_START + f.data_lba, &f.contents);
+            }
+        }
+        for sub in &dir.subdirs {
+            push_fid(&mut fids, &sub.name, sub.icb_lba, true, false);
+        }
+        disc.put(
+            PART_START + dir.icb_lba,
+            build_dir_icb(dir.dir_data_lba, fids.len() as u32),
+        );
+        disc.put_bytes(PART_START + dir.dir_data_lba, &fids);
+        for sub in &dir.subdirs {
+            lay_dir(disc, sub);
+        }
+    }
+
+    /// Build the static UDF anchor/VDS/FSD so `read_filesystem` reaches
+    /// `root_icb_lba` (single partition map → metadata_start == PART_START).
+    pub(crate) fn build_udf_skeleton(disc: &mut MemDisc, root_icb_lba: u32) {
+        let mut avdp = [0u8; 2048];
+        avdp[0..2].copy_from_slice(&2u16.to_le_bytes());
+        disc.put(256, avdp);
+
+        let mut pd = [0u8; 2048];
+        pd[0..2].copy_from_slice(&5u16.to_le_bytes());
+        pd[188..192].copy_from_slice(&PART_START.to_le_bytes());
+        disc.put(32, pd);
+
+        let mut lvd = [0u8; 2048];
+        lvd[0..2].copy_from_slice(&6u16.to_le_bytes());
+        lvd[268..272].copy_from_slice(&1u32.to_le_bytes());
+        disc.put(33, lvd);
+
+        let mut td = [0u8; 2048];
+        td[0..2].copy_from_slice(&8u16.to_le_bytes());
+        disc.put(34, td);
+
+        let mut fsd = [0u8; 2048];
+        fsd[0..2].copy_from_slice(&256u16.to_le_bytes());
+        fsd[404..408].copy_from_slice(&root_icb_lba.to_le_bytes());
+        disc.put(PART_START, fsd);
+    }
+
+    pub(crate) fn file(
+        name: &str,
+        icb_lba: u32,
+        data_lba: u32,
+        size: u32,
+        long_ad: bool,
+    ) -> FileSpec {
+        FileSpec {
+            name: name.to_string(),
+            icb_lba,
+            data_lba,
+            size,
+            long_ad,
+            contents: Vec::new(),
+        }
+    }
+
+    pub(crate) fn file_with(
+        name: &str,
+        icb_lba: u32,
+        data_lba: u32,
+        contents: Vec<u8>,
+        long_ad: bool,
+    ) -> FileSpec {
+        FileSpec {
+            name: name.to_string(),
+            icb_lba,
+            data_lba,
+            size: contents.len() as u32,
+            long_ad,
+            contents,
+        }
+    }
+}

src/unlock_bridge.rs

@@ -9,6 +9,7 @@ use freemkv_unlock as fu;
 fn to_fu_drive_id(drive_id: &crate::identity::DriveId) -> fu::DriveId {
     fu::DriveId {
         vendor_id: drive_id.vendor_id.clone(),
+        product_id: drive_id.product_id.clone(),
         product_revision: drive_id.product_revision.clone(),
         vendor_specific: drive_id.vendor_specific.clone(),
         firmware_date: drive_id.firmware_date.clone(),
@@ -89,7 +90,7 @@ impl fu::scsi::ScsiTransport for ScsiAdapter<'_> {
 }
 
 /// Map libfreemkv's host certs (keysource-collected) to the unlock contract's.
-pub(crate) fn map_host_certs(certs: &[crate::aacs::HostCert]) -> Vec<fu::HostCert> {
+pub(crate) fn map_host_certs(certs: &[crate::aacs::types::HostCert]) -> Vec<fu::HostCert> {
     certs
         .iter()
         .map(|c| fu::HostCert {
@@ -101,27 +102,70 @@ pub(crate) fn map_host_certs(certs: &[crate::aacs::HostCert]) -> Vec<fu::HostCer
         .collect()
 }
 
-/// News up the unlockers, build the context for `kind`, and run the FIRST
-/// matching one — returning its `Result` so the caller can both consume what it
-/// learned (vid / bus_key / drive_unlocked) AND render the specific failure
-/// (the AACS cert path maps the `UnlockError` to its outcome trace). `Err(
-/// NotApplicable)` when nothing matched. `host_certs` are collected by the
-/// caller — lazily, only for AACS; pass `&[]` for the drive-prep / CSS kinds.
-pub(crate) fn run_unlockers(
+/// Result of a capability dispatch: `(matched_name, result)`. `matched_name` is
+/// the unlocker that handled it (or `""` if none did) — lets the caller record
+/// WHICH unlocker ran (e.g. `LibreDrive` vs `Renesas`), distinct from the ld-only
+/// identity lookup [`unlocker_name`]. Iterating stops at the first unlocker whose
+/// capability method returns anything other than `NotApplicable` — i.e. an actual
+/// unlock (`Ok`) OR a real failure such as a dead bus (`Err(Transport)`), which
+/// the caller must surface rather than skip.
+type Dispatch = (
+    &'static str,
+    std::result::Result<fu::Unlocked, fu::UnlockError>,
+);
+
+/// Try each unlocker's `capability` (`unlock_features` or `unlock_bus`) in
+/// registration order, stopping at the first that doesn't decline. Shared by
+/// [`run_features`] and [`run_bus`].
+fn dispatch(
     scsi: &mut dyn crate::scsi::ScsiTransport,
     drive_id: &crate::identity::DriveId,
     kind: fu::DiscKind,
     host_certs: &[fu::HostCert],
-) -> std::result::Result<fu::Unlocked, fu::UnlockError> {
+    capability: impl Fn(
+        &dyn fu::Unlocker,
+        &mut dyn fu::scsi::ScsiTransport,
+        &fu::UnlockCtx,
+    ) -> std::result::Result<fu::Unlocked, fu::UnlockError>,
+) -> Dispatch {
     let id = to_fu_drive_id(drive_id);
     let ctx = fu::UnlockCtx::new(&id, kind, host_certs);
     let mut adapter = ScsiAdapter(scsi);
     for u in fu::all_unlockers() {
-        if u.matches(&ctx) {
-            return u.unlock(&mut adapter, &ctx);
+        match capability(u.as_ref(), &mut adapter, &ctx) {
+            // This unlocker doesn't provide the capability for this drive/disc —
+            // try the next one.
+            Err(fu::UnlockError::NotApplicable) => continue,
+            // An actual unlock, or a real failure (e.g. Transport) — stop here.
+            other => return (u.name(), other),
         }
     }
-    Err(fu::UnlockError::NotApplicable)
+    ("", Err(fu::UnlockError::NotApplicable))
+}
+
+/// Drive-prep: unlock DRIVE FEATURES (riplock/speed, OEM VID). `host_certs` are
+/// not needed for features — pass `&[]`; `kind` is `Unknown` at drive-prep.
+pub(crate) fn run_features(
+    scsi: &mut dyn crate::scsi::ScsiTransport,
+    drive_id: &crate::identity::DriveId,
+) -> Dispatch {
+    dispatch(scsi, drive_id, fu::DiscKind::Unknown, &[], |u, s, c| {
+        u.unlock_features(s, c)
+    })
+}
+
+/// Content: remove BUS ENCRYPTION for the mounted disc. Called only when the bus
+/// isn't already clear (the `oem_vid`/`bus_encryption_removed` gate). `host_certs`
+/// are the caller-collected certs for the AACS route; `kind` selects Aacs vs Css.
+pub(crate) fn run_bus(
+    scsi: &mut dyn crate::scsi::ScsiTransport,
+    drive_id: &crate::identity::DriveId,
+    kind: fu::DiscKind,
+    host_certs: &[fu::HostCert],
+) -> Dispatch {
+    dispatch(scsi, drive_id, kind, host_certs, |u, s, c| {
+        u.unlock_bus(s, c)
+    })
 }
 
 /// The names of every REGISTERED unlocker, in dispatch order. Registry-driven —

tests/crypto_tests.rs

@@ -84,9 +84,9 @@ fn aacs_decrypt_unit_roundtrip() {
     ];
 
     // Build plaintext unit with TS sync bytes every 192 bytes starting at offset 4
-    let mut plain = vec![0u8; aacs::ALIGNED_UNIT_LEN];
+    let mut plain = vec![0u8; aacs::content::ALIGNED_UNIT_LEN];
     let mut offset = 4;
-    while offset < aacs::ALIGNED_UNIT_LEN {
+    while offset < aacs::content::ALIGNED_UNIT_LEN {
         plain[offset] = 0x47; // TS sync byte
         offset += 192;
     }
@@ -118,7 +118,7 @@ fn aacs_decrypt_unit_roundtrip() {
     // Step 3: AES-CBC encrypt bytes 16..6144
     let cipher = Aes128::new(GenericArray::from_slice(&encrypt_key));
     let mut prev = aacs_iv;
-    let num_blocks = (aacs::ALIGNED_UNIT_LEN - 16) / 16;
+    let num_blocks = (aacs::content::ALIGNED_UNIT_LEN - 16) / 16;
     for i in 0..num_blocks {
         let off = 16 + i * 16;
         for j in 0..16 {
@@ -131,29 +131,29 @@ fn aacs_decrypt_unit_roundtrip() {
     }
 
     // Verify it looks encrypted (body TS syncs scrambled)
-    assert!(aacs::ts_sync_destroyed(&plain));
+    assert!(aacs::content::ts_sync_destroyed(&plain));
 
     // Now decrypt
-    let result = aacs::decrypt_unit(&mut plain, &unit_key);
+    let result = aacs::content::decrypt_unit(&mut plain, &unit_key);
     assert!(
         result,
         "decrypt_unit should return true on valid encrypted unit"
     );
     assert!(
-        !aacs::ts_sync_destroyed(&plain),
+        !aacs::content::ts_sync_destroyed(&plain),
         "decrypted unit should read as clear (TS syncs restored)"
     );
 
     // Verify TS sync bytes at expected positions (flag byte is cleared by decrypt)
     let mut sync_count = 0;
     let mut off = 4;
-    while off < aacs::ALIGNED_UNIT_LEN {
+    while off < aacs::content::ALIGNED_UNIT_LEN {
         if plain[off] == 0x47 {
             sync_count += 1;
         }
         off += 192;
     }
-    let expected_syncs = (aacs::ALIGNED_UNIT_LEN - 4) / 192 + 1;
+    let expected_syncs = (aacs::content::ALIGNED_UNIT_LEN - 4) / 192 + 1;
     assert_eq!(
         sync_count, expected_syncs,
         "TS sync bytes not recovered: got {}, expected {}",
@@ -176,11 +176,11 @@ fn aacs_disc_hash_deterministic() {
     let data1 = b"Unit_Key_RO.inf test data for deterministic hashing";
     let data2 = b"Different data should produce different hash";
 
-    let hash1a = aacs::disc_hash(data1);
-    let hash1b = aacs::disc_hash(data1);
+    let hash1a = aacs::inf::disc_hash(data1);
+    let hash1b = aacs::inf::disc_hash(data1);
     assert_eq!(hash1a, hash1b, "disc_hash not deterministic on same input");
 
-    let hash2 = aacs::disc_hash(data2);
+    let hash2 = aacs::inf::disc_hash(data2);
     assert_ne!(
         hash1a, hash2,
         "different inputs should produce different hashes"
@@ -190,7 +190,7 @@ fn aacs_disc_hash_deterministic() {
     assert_eq!(hash1a.len(), 20);
 
     // Verify disc_hash_hex formatting
-    let hex = aacs::disc_hash_hex(&hash1a);
+    let hex = aacs::inf::disc_hash_hex(&hash1a);
     assert!(hex.starts_with("0x"), "hex should start with 0x prefix");
     assert_eq!(
         hex.len(),
@@ -225,7 +225,7 @@ fn aacs_decrypt_unit_key_roundtrip() {
     encrypted_uk.copy_from_slice(&block);
 
     // Decrypt with the public API
-    let decrypted = aacs::decrypt_unit_key(&vuk, &encrypted_uk);
+    let decrypted = aacs::derive::decrypt_unit_key(&vuk, &encrypted_uk);
     assert_eq!(
         decrypted, original_unit_key,
         "decrypt_unit_key did not recover original unit key"
@@ -246,7 +246,7 @@ fn aacs_vuk_derivation_roundtrip() {
         0x30,
     ];
 
-    let vuk = aacs::derive_vuk(&media_key, &volume_id);
+    let vuk = aacs::derive::derive_vuk(&media_key, &volume_id);
 
     // VUK should be non-zero and different from both inputs
     assert_ne!(vuk, [0u8; 16], "VUK should not be all zeros");
@@ -254,7 +254,7 @@ fn aacs_vuk_derivation_roundtrip() {
     assert_ne!(vuk, volume_id, "VUK should differ from volume_id");
 
     // Verify determinism
-    let vuk2 = aacs::derive_vuk(&media_key, &volume_id);
+    let vuk2 = aacs::derive::derive_vuk(&media_key, &volume_id);
     assert_eq!(vuk, vuk2, "derive_vuk not deterministic");
 }
 
@@ -263,14 +263,14 @@ fn aacs_vuk_derivation_roundtrip() {
 fn aacs_ts_sync_destroyed_detection() {
     // A clear unit: TS sync (0x47) intact at every 192-byte packet → not
     // scrambled. (Flag bits play no role.)
-    let mut clear = vec![0u8; aacs::ALIGNED_UNIT_LEN];
+    let mut clear = vec![0u8; aacs::content::ALIGNED_UNIT_LEN];
     let mut off = 4;
-    while off < aacs::ALIGNED_UNIT_LEN {
+    while off < aacs::content::ALIGNED_UNIT_LEN {
         clear[off] = 0x47;
         off += 192;
     }
     assert!(
-        !aacs::ts_sync_destroyed(&clear),
+        !aacs::content::ts_sync_destroyed(&clear),
         "clear unit (syncs intact) must not be scrambled"
     );
 
@@ -279,21 +279,21 @@ fn aacs_ts_sync_destroyed_detection() {
     flagged[0] = 0xC0; // copy-control bits
     flagged[7] = 0xC0; // TSC bits
     assert!(
-        !aacs::ts_sync_destroyed(&flagged),
+        !aacs::content::ts_sync_destroyed(&flagged),
         "flag bits must not be read as encryption"
     );
 
     // A scrambled body (syncs destroyed) → scrambled.
-    let scrambled = vec![0x99u8; aacs::ALIGNED_UNIT_LEN];
+    let scrambled = vec![0x99u8; aacs::content::ALIGNED_UNIT_LEN];
     assert!(
-        aacs::ts_sync_destroyed(&scrambled),
+        aacs::content::ts_sync_destroyed(&scrambled),
         "unit with no intact TS syncs must read as scrambled"
     );
 
     // Too short
     let short = vec![0xFFu8; 100];
     assert!(
-        !aacs::ts_sync_destroyed(&short),
+        !aacs::content::ts_sync_destroyed(&short),
         "short buffer should not be detected"
     );
 }
@@ -303,10 +303,10 @@ fn aacs_ts_sync_destroyed_detection() {
 /// A clear unit (TS syncs intact) should pass through decrypt_unit unchanged.
 #[test]
 fn aacs_decrypt_unit_unencrypted_passthrough() {
-    let mut unit = vec![0x42u8; aacs::ALIGNED_UNIT_LEN];
+    let mut unit = vec![0x42u8; aacs::content::ALIGNED_UNIT_LEN];
     // Intact TS syncs every 192 bytes → not scrambled → passthrough.
     let mut off = 4;
-    while off < aacs::ALIGNED_UNIT_LEN {
+    while off < aacs::content::ALIGNED_UNIT_LEN {
         unit[off] = 0x47;
         off += 192;
     }
@@ -315,8 +315,8 @@ fn aacs_decrypt_unit_unencrypted_passthrough() {
     let original = unit.clone();
     let key = [0xAA; 16];
 
-    assert!(!aacs::ts_sync_destroyed(&unit));
-    let result = aacs::decrypt_unit(&mut unit, &key);
+    assert!(!aacs::content::ts_sync_destroyed(&unit));
+    let result = aacs::content::decrypt_unit(&mut unit, &key);
     assert!(result, "clear unit should return true");
     assert_eq!(unit, original, "clear unit should be unchanged");
 }
@@ -370,17 +370,17 @@ fn aacs_cross_validation_encrypt_then_decrypt() {
         0x10,
     ];
 
-    let mut plaintext = vec![0u8; aacs::ALIGNED_UNIT_LEN];
+    let mut plaintext = vec![0u8; aacs::content::ALIGNED_UNIT_LEN];
     // TS sync bytes every 192 bytes starting at offset 4
     let mut off = 4;
-    while off < aacs::ALIGNED_UNIT_LEN {
+    while off < aacs::content::ALIGNED_UNIT_LEN {
         plaintext[off] = 0x47;
         off += 192;
     }
     // Fill the rest with a recognisable pattern (prime modulus avoids artefacts).
     // Index-arithmetic — clearer with a counted loop than an enumerate chain.
     #[allow(clippy::needless_range_loop)]
-    for i in 16..aacs::ALIGNED_UNIT_LEN {
+    for i in 16..aacs::content::ALIGNED_UNIT_LEN {
         if plaintext[i] == 0 {
             plaintext[i] = (i % 251) as u8;
         }
@@ -402,7 +402,7 @@ fn aacs_cross_validation_encrypt_then_decrypt() {
     ref_aes_cbc_encrypt(
         &dk,
         &CROSS_AACS_IV,
-        &mut plaintext[16..aacs::ALIGNED_UNIT_LEN],
+        &mut plaintext[16..aacs::content::ALIGNED_UNIT_LEN],
     );
 
     // Sanity: ciphertext should differ
@@ -413,7 +413,7 @@ fn aacs_cross_validation_encrypt_then_decrypt() {
     );
 
     // -- Decrypt with the library --
-    let ok = aacs::decrypt_unit(&mut plaintext, &unit_key);
+    let ok = aacs::content::decrypt_unit(&mut plaintext, &unit_key);
     assert!(
         ok,
         "decrypt_unit returned false (TS sync verification failed)"
@@ -436,9 +436,9 @@ fn aacs_cross_validation_alternate_key() {
         0x08,
     ];
 
-    let mut plaintext = vec![0xFFu8; aacs::ALIGNED_UNIT_LEN];
+    let mut plaintext = vec![0xFFu8; aacs::content::ALIGNED_UNIT_LEN];
     let mut off = 4;
-    while off < aacs::ALIGNED_UNIT_LEN {
+    while off < aacs::content::ALIGNED_UNIT_LEN {
         plaintext[off] = 0x47;
         off += 192;
     }
@@ -455,10 +455,10 @@ fn aacs_cross_validation_alternate_key() {
     ref_aes_cbc_encrypt(
         &dk,
         &CROSS_AACS_IV,
-        &mut plaintext[16..aacs::ALIGNED_UNIT_LEN],
+        &mut plaintext[16..aacs::content::ALIGNED_UNIT_LEN],
     );
 
-    assert!(aacs::decrypt_unit(&mut plaintext, &unit_key));
+    assert!(aacs::content::decrypt_unit(&mut plaintext, &unit_key));
 
     // Decryption clears no flag, so the unit round-trips byte-for-byte.
     assert_eq!(&plaintext[..], &expected[..]);
@@ -473,15 +473,15 @@ fn aacs_bus_decrypt_cross_validation() {
         0x00,
     ];
 
-    let mut plaintext = vec![0u8; aacs::ALIGNED_UNIT_LEN];
+    let mut plaintext = vec![0u8; aacs::content::ALIGNED_UNIT_LEN];
     #[allow(clippy::needless_range_loop)]
-    for i in 0..aacs::ALIGNED_UNIT_LEN {
+    for i in 0..aacs::content::ALIGNED_UNIT_LEN {
         plaintext[i] = ((i * 3 + 17) & 0xFF) as u8;
     }
     let expected = plaintext.clone();
 
     // Encrypt per-sector: AES-CBC encrypt bytes 16..2048 of each 2048-byte sector
-    for sector_start in (0..aacs::ALIGNED_UNIT_LEN).step_by(2048) {
+    for sector_start in (0..aacs::content::ALIGNED_UNIT_LEN).step_by(2048) {
         ref_aes_cbc_encrypt(
             &read_data_key,
             &CROSS_AACS_IV,
@@ -490,7 +490,7 @@ fn aacs_bus_decrypt_cross_validation() {
     }
     assert_ne!(&plaintext[16..32], &expected[16..32]);
 
-    aacs::decrypt_bus(&mut plaintext, &read_data_key);
+    aacs::content::decrypt_bus(&mut plaintext, &read_data_key);
     assert_eq!(
         plaintext, expected,
         "bus decrypt did not recover original plaintext"
@@ -738,7 +738,7 @@ fn aacs_parse_unit_key_ro_minimal() {
         data[key_pos + i] = (0xA0 + i) as u8;
     }
 
-    let result = aacs::parse_unit_key_ro(&data, aacs::AacsVersion::V10);
+    let result = aacs::inf::parse_unit_key_ro(&data, aacs::mkb::AacsVersion::V10);
     assert!(
         result.is_some(),
         "parse_unit_key_ro should succeed on valid data"
@@ -751,6 +751,6 @@ fn aacs_parse_unit_key_ro_minimal() {
     assert_eq!(ukf.disc_hash.len(), 20);
 
     // disc_hash should be deterministic
-    let hash = aacs::disc_hash(&data);
+    let hash = aacs::inf::disc_hash(&data);
     assert_eq!(ukf.disc_hash, hash);
 }

tests/pass_n_patch_fix.rs

@@ -10,7 +10,7 @@ use libfreemkv::{aacs, decrypt::DecryptKeys};
 #[test]
 fn decrypt_sectors_with_aacs_keys_works() {
     // Build an encrypted aligned unit
-    let mut unit = vec![0xFFu8; aacs::ALIGNED_UNIT_LEN];
+    let mut unit = vec![0xFFu8; aacs::content::ALIGNED_UNIT_LEN];
 
     // Set encryption flag (bits 6-7 of byte 0)
     unit[0] |= 0xC0;
@@ -19,7 +19,7 @@ fn decrypt_sectors_with_aacs_keys_works() {
     for (i, byte) in unit
         .iter_mut()
         .enumerate()
-        .take(aacs::ALIGNED_UNIT_LEN)
+        .take(aacs::content::ALIGNED_UNIT_LEN)
         .skip(1)
     {
         *byte = ((i * 3 + 7) & 0xFF) as u8;
@@ -28,7 +28,7 @@ fn decrypt_sectors_with_aacs_keys_works() {
     let unit_key: [u8; 16] = [0xAAu8; 16];
 
     // Encrypt the unit using AACS algorithm
-    aacs::decrypt_unit(&mut unit, &unit_key); // decrypt_unit is idempotent on already-encrypted data
+    aacs::content::decrypt_unit(&mut unit, &unit_key); // decrypt_unit is idempotent on already-encrypted data
 
     // Now we have encrypted data - create DecryptKeys with actual keys
     let mut keys = DecryptKeys::Aacs {
@@ -83,23 +83,23 @@ fn decrypt_sectors_with_css_keys_works() {
 #[test]
 fn aacs_encryption_flag_detection() {
     // A clear unit: TS syncs (0x47) intact at every 192-byte packet.
-    let mut unit = vec![0u8; aacs::ALIGNED_UNIT_LEN];
+    let mut unit = vec![0u8; aacs::content::ALIGNED_UNIT_LEN];
     let mut off = 4;
-    while off < aacs::ALIGNED_UNIT_LEN {
+    while off < aacs::content::ALIGNED_UNIT_LEN {
         unit[off] = 0x47;
         off += 192;
     }
     // Encryption is the scrambled body (TS syncs destroyed), NOT a flag bit.
-    assert!(!aacs::ts_sync_destroyed(&unit));
+    assert!(!aacs::content::ts_sync_destroyed(&unit));
 
     // Flag bits on a synced unit do not make it look encrypted.
     unit[0] = 0xC0;
     unit[7] = 0xC0;
-    assert!(!aacs::ts_sync_destroyed(&unit));
+    assert!(!aacs::content::ts_sync_destroyed(&unit));
 
     // Scrambled body (syncs gone) → encrypted.
-    let scrambled = vec![0x99u8; aacs::ALIGNED_UNIT_LEN];
-    assert!(aacs::ts_sync_destroyed(&scrambled));
+    let scrambled = vec![0x99u8; aacs::content::ALIGNED_UNIT_LEN];
+    assert!(aacs::content::ts_sync_destroyed(&scrambled));
 }
 
 /// Test: DecryptKeys::is_encrypted() correctly identifies encrypted state.