v0.30.0: DiscInputs carries the disc's volume label (title)

Add `DiscInputs.volume_label: Option<String>` — the disc's human title (UDF/ISO
volume identifier, else BDMV <di:name>), populated by Disc::inputs() from the
scan. Identity only, no secret, not used in any AACS derivation; lets a key
source forward the title so a key service can catalog disc_hash → title.

.github/workflows/ci.yml

@@ -14,6 +14,10 @@ jobs:
         with:
           components: clippy, rustfmt
       - run: cargo fmt --check
+      # libfreemkv is a library — Cargo.lock is gitignored. --locked
+      # would always fail on a fresh runner because there's no committed
+      # lockfile to lock against. The binary crates (freemkv, autorip,
+      # bdemu) track Cargo.lock and DO use --locked.
       - run: cargo clippy -- -D warnings
 
   test:

.github/workflows/release.yml

@@ -28,6 +28,8 @@ jobs:
     steps:
       - uses: actions/checkout@v5
       - uses: dtolnay/rust-toolchain@1.86.0
+      # libfreemkv is a library — Cargo.lock isn't tracked, so --locked
+      # would always fail (no lockfile to lock against on a fresh runner).
       - run: cargo test
 
   publish:

.gitignore

@@ -4,3 +4,7 @@ Cargo.lock
 *.swo
 .DS_Store
 .cargo/
+.claude/worktrees/
+
+# session scratch — never track (may contain RE breadcrumbs)
+scratch/

CHANGELOG.md

@@ -1,5 +1,854 @@
 # Changelog
 
+## 0.29.0 (2026-06-06)
+
+### Fixed
+
+- **Video frames now carry their presentation timestamp (PTS), not the decode
+  timestamp (DTS), as the MKV block timecode.** The HEVC, H.264, VC-1 and
+  MPEG-2 parsers stamped each frame with `dts.or(pts)`, so B-frame titles were
+  muxed with monotonic decode-order timecodes: players presented frames in
+  decode order (visible judder / apparent "corruption") and PTS-based seeking
+  landed on the wrong frame. The compressed video was always byte-correct —
+  this was purely a timestamp defect, and it affected every B-frame title. The
+  parsers now use `pts.or(dts)`. Verified against a reference muxer on a real
+  UHD title: the emitted frame sequence is now identical.
+- **DTS-HD MA tracks no longer downgrade to the lossy DTS core** — the access
+  unit is delimited by the next *validated* core sync, so a `0x7FFE8001` byte
+  pattern inside the XLL extension can no longer truncate the unit. (#10)
+- **A resolved AACS key is verified against the content before it is applied**,
+  so a stale or wrong VUK can no longer silently produce garbage output.
+- **`iso://` mux fails fast when no usable AACS key is available** instead of
+  writing a garbage MKV.
+
+### Changed
+
+- Codec / EBML / TS hardening: bounds-checked PMT and PES-header parsing, EBML
+  length validation, and bounded codec buffers (DTS, TrueHD, PGS).
+
+## 0.27.3 (2026-06-04)
+
+### Added
+
+- **The mapfile now persists resolved AACS unit keys, not just the Volume ID.**
+  A keyed disc writes its decrypted unit keys as `# freemkv-uk: <cps>:<hex>`
+  comment headers; an unresolved disc writes only the `# freemkv-vid:` marker.
+  The two are **mutually exclusive** (`Mapfile::set_unit_keys` clears the VID):
+  unit keys are the final answer, so a deferred-mux / resume decrypts directly
+  with no key-service round-trip, while the VID alone means "still unresolved —
+  retry the key service." `CopyOptions`/`SweepOptions` gain a `unit_keys` field
+  (written when non-empty, else the VID), and `Disc::inject_unit_keys` applies
+  mapfile-recovered keys to a scanned disc (marking the source `ExternalUk`).
+
+## 0.27.0 (2026-06-03)
+
+### Changed
+
+- **AACS unit-encryption detection now reads the raw MPEG-TS sync bytes
+  instead of header flag bits.** `is_unit_encrypted` is renamed
+  `is_aacs_scrambled`: a unit is encrypted iff its body TS packet sync bytes
+  (`0x47` at offset 4 and every 192 bytes) are not intact — the encrypted
+  body destroys them. The previous check read the TP_extra copy-control bits
+  (byte 0) or TS transport_scrambling_control bits (byte 7), which discs and
+  players do not set reliably. A single predicate now backs both the decrypt
+  gate and out-of-band key validation, so all callers agree on what
+  "encrypted" means. Decryption restores the syncs, so a decrypted unit reads
+  as clear and there is no encryption flag to clear.
+
+## 0.26.1 (2026-05-22)
+
+### Added
+
+- **AACS resolver path 5 — KEYDB unit-keys direct fallback.** When a
+  KEYDB entry for the disc has no VUK field but does have pre-decrypted
+  unit keys, the resolver now consumes those unit keys directly instead
+  of treating the entry as unusable. Covers ~4,572 entries in the
+  public keydb (≈2.5% of the database, heavily skewed toward MKBv76+
+  UHD discs that DVDFab/FindVUK can no longer extract VUKs for).
+  Surfaces as `KeySource::KeyDbUnitKeys`; `AacsState::vuk` and
+  `ResolvedKeys::vuk` are `None` on this path because no VUK exists to
+  return. Partial CPS-unit coverage is rejected so a disc is never
+  half-decrypted.
+
+### Changed
+
+- **AACS resolver path order reordered root-to-leaf.** Paths now run in
+  derivation-strength order: device-key (1) → processing-key (2) →
+  KEYDB-derived from MK+VID (3) → KEYDB VUK direct (4) → KEYDB unit
+  keys direct (5). Previous order was leaf-first (KEYDB hash lookup,
+  then derivation). Resolution runs once per disc, so the few extra
+  milliseconds of MKB walking when a KEYDB VUK would have answered are
+  invisible against the rip itself; the new order matches the AACS
+  derivation hierarchy. `KeySource` enum variants are reordered to
+  match.
+- **`AacsState::vuk` type is now `Option<[u8; 16]>`** (was `[u8; 16]`).
+  Required by path 5, which has no VUK. Public-API break.
+- **`ResolvedKeys::vuk` type is now `Option<[u8; 16]>`** (was
+  `[u8; 16]`). Same rationale.
+
+## 0.25.14 (2026-05-21)
+
+### Changed
+
+- `Drive::is_libredrive_active()` renamed to `Drive::is_raw_read_active()`.
+  Same semantics; old name removed. Mirrored on the internal
+  `PlatformDriver::is_libredrive_active()` trait method (now
+  `is_raw_read_active()`).
+- `Error::AacsLibredriveUnsupported` renamed to
+  `Error::AacsRawReadUnsupported`; the underlying numeric code (E7016)
+  is unchanged. The `E_AACS_LIBREDRIVE_UNSUPPORTED` constant is
+  renamed to `E_AACS_RAW_READ_UNSUPPORTED`.
+
+No behavioural change — purely a rename pass.
+
+## 0.25.13 (2026-05-21)
+
+### Added
+
+- **`DrmScheme` top-level dispatcher.** New `drm` module with a
+  `DrmScheme` enum (`Css`, `Aacs10`, `Aacs20`, `Aacs21`) and a
+  `detect` + `load` pair that uniformly handles all four content
+  protection schemes. Replaces the inlined dispatch in
+  `disc::encrypt::resolve_encryption` and the scattered CSS routing
+  in `disc::mod`. Both CSS call sites now route through the same
+  entry point.
+- **AACS 2.1 Media Key Variant framework.** New `aacs::variants`
+  module implementing the Media Key Variant derivation chain
+  (`Kp + C → Kmp → ⊕KCD → Kpnew → Km → VUK`), Variant-scheme MKB
+  record parsing (record types `0x82` / `0x83`), bit-0x02 SoftKCD
+  and bit-0x04 online-challenge detection with dedicated error
+  variants. Wired into `DrmScheme::Aacs21` but the dispatcher arm
+  is commented out pending validation against a Variant-scheme
+  disc. Per-manufacturer Key Correction Data must be supplied by
+  the integrator; `KEY_CORRECTION_DATA_PLACEHOLDER` is the empty
+  placeholder slot.
+- **`AacsVersion` enum.** Replaces the `aacs2: bool` field on
+  `ContentCertificate`, `UnitKeyFile`, and `ResolvedKeys`.
+  `parse_unit_key_ro` and `parse_content_cert` now take/emit the
+  enum. `resolve_keys` is split into `resolve_keys_v1`,
+  `resolve_keys_v2`, and `resolve_keys_v21` (the last not reachable
+  from the dispatcher today).
+
+### Fixed
+
+- **Libredrive raw-read VID shortcut deleted.** v0.25.11 introduced a
+  `do_handshake` branch that, on libredrive-active drives, skipped the
+  AACS cert handshake and issued `READ_DISC_STRUCTURE` format 0x80
+  with AGID=0 directly. The hypothesis was that unlocked
+  drives would serve VID without auth. Empirical test (BU40N
+  + UHD disc, 2026-05-21) showed the drive returns
+  `0x05 / 0x6F / 0x02` (`ILLEGAL_REQUEST / Copy protection key
+  exchange failure: KEY NOT ESTABLISHED`) to that CDB regardless of
+  drive-unlock state. The AACS spec requires a successful
+  `REPORT_KEY` / `SEND_KEY` exchange to establish an AGID before
+  format 0x80 returns VID; that requirement is enforced by the drive
+  itself and isn't bypassed by libredrive firmware. The shortcut
+  fired for every libredrive-active drive, so v0.25.11 / v0.25.12
+  MOVIE scans were stuck at E7017 instead of progressing to the
+  real wall (no DK walks MKB v77).
+- `Disc::do_handshake` now always routes through `do_handshake_cert`.
+  `Drive::is_libredrive_active()` and the Mt1959 MMkv+LbDr marker
+  detection are kept as informational signals (logged in the
+  `handshake_entry` warn line) but no longer steer the auth path.
+- `read_volume_id_libredrive` deleted (~50 LOC).
+
+The corollary: AACS resolution on HRL-burned drives + UHD discs now
+fails honestly. Either cert auth succeeds (drive unlock may or
+may not bypass the HRL — that's the new empirical question) and we
+hit the actual DK wall (E7018 "No DK that walks this MKB" for v77+
+UHD without a v77+ DK in keydb), or cert auth fails and we surface
+E7015. Both are real verdicts; E7017's previous spurious dispatch
+is gone.
+
+## 0.25.12 (2026-05-21)
+
+No libfreemkv source changes — unified sync bump for autorip's
+`aacs_failure_message` two-line wording rewrite. See the autorip
+v0.25.12 release for details.
+
+## 0.25.11 (2026-05-21)
+
+### Added
+
+- **Libredrive raw-read VID path.** When the Mt1959 unlock response
+  confirms both the active-mode (`MMkv`) and mode-ID (`LbDr`) markers,
+  `Drive::is_libredrive_active()` returns true and `do_handshake`
+  skips the AACS cert dance entirely — VID is retrieved via
+  `READ_DISC_STRUCTURE` format 0x80 with AGID=0, and bus encryption
+  is already off. This is what unblocks UHD ripping on drives whose
+  leaked host cert is on the AACS HRL.
+- New `Error` variants for finer-grained AACS failure reporting:
+  `AacsHostCertRejected` (E7015), `AacsLibredriveUnsupported`
+  (E7016), `AacsVidUnavailable` (E7017), `AacsMkUnavailable`
+  (E7018), `AacsVukNotInKeydb` (E7019). Lets CLIs/UIs render which
+  piece of the AACS chain failed instead of always saying "no keys."
+
+### Fixed
+
+- `validate_processing_key` now matches libaacs `_validate_pk`
+  exactly: XORs `uv` into `mk[12..16]` (was omitted), AES-decrypts
+  `mk_dv` and checks the `01 23 45 67 89 AB CD EF` magic (was
+  AES-encrypt + 12-zero check). Pre-fix, every non-zero-uv
+  processing key was rejected — i.e. essentially every real disc.
+- `mkb_find_cvalues` now prefers record type `0x07` (AACS 2.x) and
+  falls back to `0x05` (AACS 1.0), so the walker handles both
+  generations without an out-of-band version flag.
+- `resolve_keys` short-circuits paths 2/3/4 when VID is the zero
+  sentinel — saves cycles and emits an honest "VID unavailable" log
+  instead of the misleading "all paths failed."
+- AES-CMAC VID verification gains NIST SP 800-38B KAT + round-trip
+  + mutation + all-zero-rejection tests.
+
+### Removed
+
+- **Built-in AACS keys** (added in 0.25.9). `src/aacs/builtin_keys.rs`
+  deleted; `KeyDb::with_builtins`, `KeyDb::load_or_builtins`,
+  `KeyDb::merge_from`, and internal dedup helpers gone. The
+  compiled-in shortcut was a slim convenience that didn't move the
+  hard problem (no v77+ DKs) and added a maintenance surface.
+- **Operator plugin slot** at `~/.config/freemkv/local_keys.cfg`
+  (added in 0.25.9). `local_plugin_path` and `KeyDb::merge_local_plugin`
+  removed. Single source: the main `keydb.cfg`.
+- `KeyDb::load` reverts to the pre-0.25.9 form — read the file or
+  return I/O error; no layering, no fallback.
+- `Disc::scan` reverts to surfacing `KeydbLoad { path: "<no keydb
+  in search paths>" }` for an encrypted disc with no keydb — same
+  sentinel autorip's message switch already handles.
+
+CSS player keys in `src/css/auth.rs` remain compiled in; they're
+1999-era public inputs separate from the AACS pipeline and were
+never part of the 0.25.9 additions.
+
+## 0.25.9 (2026-05-20)
+
+### Fixed
+
+- **MKB record-type identification.** `mkb_find_mk_dv` and `mkb_version`
+  had their record-type constants swapped. The Verify Media Key record
+  is Type 0x81 (AACS 1.0) or Type 0x86 (AACS 2.0/2.1), not 0x10. The
+  Type-and-Version record is Type 0x10, not 0x81. PK and DK derivation
+  paths therefore failed silently on every disc, masking how often the
+  fallback paths could have succeeded. Fixed; mk_dv extracted at
+  offset 4 of the verify record, MKB version read at offset 8 of the
+  Type 0x10 record body. Tests added for both forms.
+
+### Added
+
+- **Built-in AACS keys.** Four device keys (covering MKB v01-v82+) and
+  three processing keys (covering v63-v68) are now compiled into
+  `libfreemkv` directly. DVDs and Blu-rays (AACS 1.0) decrypt with
+  zero external files. Combined with the existing 31 CSS player keys
+  in `css/auth.rs`, the library is self-sufficient for all DVD and
+  AACS 1.0 content.
+- **Operator plugin slot.** `~/.config/freemkv/local_keys.cfg` is
+  loaded automatically (same format as `keydb.cfg`) and layered
+  additively on top of the built-ins and the main keydb.cfg. For
+  operators who derive their own keys, this is the additive surface
+  to drop them into — main keydb.cfg from upstream auto-update stays
+  separate and overwritable.
+- `KeyDb::with_builtins()`, `KeyDb::load_or_builtins()`,
+  `KeyDb::empty()` constructors.
+
+### Changed
+
+- `Disc::scan` no longer errors when keydb.cfg is absent. With
+  built-ins covering DVD/BD, missing keydb is treated as "no UHD
+  keys available" — the AACS 2.0 / UHD code path surfaces a
+  specific error only when the disc actually needs keys that
+  aren't in built-ins, main keydb, or local plugin.
+
+## 0.25.8 (2026-05-20)
+
+### Changed
+
+- Synchronized to autorip 0.25.8. No libfreemkv code changes —
+  unified versioning bump only. autorip 0.25.7 image was DOA
+  (missing +x on the binary); see autorip changelog.
+
+## 0.25.7 (2026-05-20)
+
+### Fixed — BU40N firmware wedge on KEYDB-miss discs
+
+`disc::encrypt::do_handshake` used to fire up to 16 AACS authenticate
+attempts back-to-back with no pause between them. Each attempt is
+5-10 SCSI REPORT_KEY/SEND_KEY exchanges. On a disc whose host cert
+isn't in our KEYDB (or one the drive rejects), that's 80-160 SCSI
+commands hammered at the drive in a few hundred milliseconds — and
+the BU40N (plus most consumer optical drives) responds by entering
+a fast-fail firmware wedge state where every subsequent CDB returns
+`ILLEGAL_REQUEST/INVALID_FIELD_IN_CDB` (sense 0x05/0x24) until the
+drive is physically power-cycled.
+
+Live wedge event 2026-05-20 during a UHD disc scan
+(KEYDB miss) confirmed the diagnosis and motivated this fix.
+
+Defence-in-depth:
+- `MAX_CERT_ATTEMPTS` capped at 3 (was 16). If three different
+  host certs all fail, more won't help — the drive doesn't have a
+  match.
+- 1-second sleep between attempts. Gives the drive's firmware time
+  to recover internal state between auth challenges.
+- Bail immediately on any sense code with sense_key = 0x05
+  (`ILLEGAL_REQUEST`). The drive isn't merely rejecting our cert
+  — it's saying "I won't talk to you anymore" — so trying more
+  certs would deepen the wedge.
+
+## 0.25.6 (2026-05-20)
+
+### Changed
+
+- Synchronized to autorip 0.25.6 release. No behavioural changes.
+
+## 0.25.5 (2026-05-20)
+
+### Changed
+
+- Synchronized to autorip 0.25.5 release. No behavioural changes.
+
+## 0.25.4 (2026-05-20)
+
+### Changed
+
+- Synchronized to autorip 0.25.4 release. No behavioural changes
+  in the library — the v0.25.4 release ships the autorip-side
+  in-container NFS mount option.
+
+## 0.25.3 (2026-05-19)
+
+### Changed
+
+- Synchronized to autorip 0.25.3 release. No behavioural changes
+  in the library — the v0.25.3 release ships the autorip-side
+  parallel mux pipeline.
+
+## 0.25.2 (2026-05-19)
+
+### Fixed
+
+- **DTS-HD codec ID** — `MkvTrack::audio` now emits `A_DTS/MA` for
+  DTS-HD MA and `A_DTS/HR` for DTS-HD HR instead of mislabelling
+  both as plain `A_DTS`. Strict players (Plex transcoder, some
+  hardware decoders, AV receivers) reject lossless DTS-HD MA
+  payload when the track advertises `A_DTS` because the ID
+  implies the 1.5 Mbps core-only bitstream.
+- **PGS subtitle BlockDuration** — the PGS parser is now stateful:
+  it pairs each display PCS with the following empty/clear PCS to
+  compute a duration, and the MKV muxer emits a `BlockGroup` +
+  `BlockDuration` for subtitles that carry one. Without this the
+  last bitmap lingered on screen until the next display set
+  replaced it (or until end of file).
+
+### Changed
+
+- `codec::Frame` gains `duration_ns: Option<u64>` (set by parsers
+  that can compute one; currently only PGS).
+- `pes::PesFrame` gains `duration_ns: Option<u64>` (in-memory only;
+  not part of the on-wire serialization).
+- `MkvMuxer::write_frame` now takes a final `duration_ns: Option<u64>`
+  parameter. When `Some`, the frame is emitted as a `BlockGroup`
+  with `BlockDuration` instead of a `SimpleBlock`.
+
+## 0.25.1 (2026-05-19)
+
+### New — autorip event_fn plumbing
+
+- `PrefetchedSectorSource::new_with_events(reader, extents, batch,
+  halt, event_fn)` — same producer-thread pipeline as `new()`, plus
+  an optional callback fired from the producer with `BytesRead`
+  events after every successful batch. Lets the autorip multipass
+  + resume mux paths drive their progress UI from the highway
+  without polling the consumer side.
+- `build_iso_pipeline` gains an `event_fn` parameter so callers can
+  wire the same callback through one ctor.
+
+### Changed
+
+- `pes::Stream` trait: new default `errors() -> u64` method
+  (default returns 0). Lets `Box<dyn Stream>` callers query the
+  skip-on-error counter without downcasting. `DiscStream` overrides
+  to surface its existing `errors` field.
+
+### Removed (breaking)
+
+- `DiscStream::new_pipeline` and `DiscStream::read_pipeline`
+  deleted. All file-backed mux now uses `build_iso_pipeline` →
+  `PipelinedPesStream`. `DiscStream` is now the single-threaded
+  inline reader used by autorip's live-drive single-pass path only.
+- `DiscStream::demux_thread` and `demux_rx` fields removed.
+- `M2tsStream::open` deleted; `Mode::Read` variant removed.
+  `m2ts://` URLs go through the internal `build_m2ts_pipeline`
+  helper in `mux/resolve.rs` → `PipelinedPesStream`. `M2tsStream`
+  is a write-only sink now.
+
+## 0.25.0 (2026-05-19)
+
+### New — the freemkv mux throughput "highway"
+
+Three-stage pipelined PES read path. Read+decrypt runs on a
+producer thread, M2TS demux runs on a second thread, codec parse
+runs on the caller's thread. Communication between stages is via
+bounded `crossbeam_channel` with a recycled buffer pool — no
+allocations or memcpys in the steady-state hot loop.
+
+**Throughput on the test bed (a UHD disc, 62 GiB ISO →
+`null://`, single-thread caller):**
+
+|                                       |   MB/s |
+| ------------------------------------- | -----: |
+| 0.23.2 baseline                       |     60 |
+| + memchr SIMD HEVC start-code scan    |     69 |
+| + ts.feed no-copy boundary            |     72 |
+| + `PrefetchedSectorSource` (producer) |    124 |
+| + `DemuxThread` (3-stage pipeline)    |    135 |
+| + zero-copy recycled buffer pool      |    148 |
+| + 16 KiB initial PesAssembler buffer  |    162 |
+| + mimalloc allocator in freemkv CLI   |  200+  |
+| **+ warm cache**                      | **660** |
+
+The new public API:
+
+- `libfreemkv::PrefetchedSectorSource` — wraps any `SectorSource`,
+  spawns a producer thread, exposes recycled-buffer channels.
+- `libfreemkv::io::byte_prefetcher::BytePrefetcher` —
+  `std::io::Read` analogue for byte-stream sources (m2ts files,
+  sockets, stdin).
+- `libfreemkv::mux::demux_thread::DemuxThread` — the M2TS demux
+  worker; `spawn_zero_copy` takes either prefetcher's channels.
+- `libfreemkv::PipelinedPesStream` — the read-side `Stream` impl
+  that runs codec parse on the caller thread.
+- `libfreemkv::build_iso_pipeline(reader, title, keys, batch,
+  format, halt)` — the canonical ctor that wires all three stages
+  for an ISO file source.
+
+### Changed (breaking)
+
+- `IsoSectorReader` (the naive duplicate of `FileSectorSource`)
+  deleted. `FileSectorSource` is the sole file-backed sector
+  source; it carries the SEQUENTIAL fadvise hint, the periodic
+  DONTNEED page-cache eviction, and (new) the per-read
+  `readahead()` async-prefetch syscall.
+- `mux::input("iso://...", &opts)` now returns a
+  `PipelinedPesStream`. Function signature
+  `input(&str, &InputOptions) -> io::Result<Box<dyn Stream>>` is
+  unchanged; callers that treated the return value as
+  `Box<dyn Stream>` keep working.
+
+### Other
+
+- `FileSectorSource` exposes per-OS `prefetch()` hooks
+  (`readahead(2)` on Linux, `fcntl(F_RDADVISE)` on macOS, no-op on
+  Windows + other).
+- AACS decrypt thread-pool: env var renamed from
+  `FREEMKV_DECRYPT_THREADS` to `FREEMKV_THREADS`; default raised
+  to `cores.clamp(1, 64)`.
+- `PesAssembler` initial buffer capacity 256 KiB → 16 KiB (avoids
+  the 64-page first-touch fault tax on every PES boundary).
+- HEVC / H.264 `find_start_code` swapped onto
+  `memchr::memmem::find` (SIMD).
+
+## 0.18.4 (2026-05-09)
+
+### Build / CI hardening — no library code changes
+
+- All `cargo` invocations in `.github/workflows/*.yml` now use
+  `--locked`. Previously `cargo build` / `cargo test` could silently
+  re-resolve `Cargo.lock` if a lock-pinned version wasn't yet on
+  crates.io — masking dependency races between same-tag releases of
+  sibling crates. The 0.18.3 release hit this: autorip's docker image
+  built `libfreemkv v0.18.2` because libfreemkv 0.18.3 hadn't
+  published yet at the time autorip's CI ran, and cargo silently fell
+  back to the previous version. With `--locked`, that race now hard-
+  fails the build with a clear "package X is not in registry" error
+  and we retrigger after the upstream lands.
+
+- `cargo publish --locked` in the release workflow guards against
+  publishing a lockfile-mismatched release.
+
+## 0.18.3 (2026-05-09)
+
+### Behaviour change
+
+- **`Disc::titles[0]` is now the canonical main feature on branching
+  discs, not the longest playlist.** Previously titles were sorted
+  purely by `duration_secs` descending, which puts a "play-all"
+  virtual playlist (alternate angles / seamless branching) at index 0
+  on UHDs that ship one — its inflated duration overshoots the real
+  movie. Concrete example: *The Amateur (2025)* 4K UHD on a 58.5 GB
+  disc has Title 1 = `00020.mpls` 4h13m / 92.4 GB / 253 clips
+  (impossible — the size exceeds the disc capacity, proving it's a
+  virtual composite) and Title 2 = `00800.mpls` 2h02m / 57.2 GB /
+  1 clip (the actual film, matching TMDB).
+
+  New sort priority:
+  1. Real titles (`size_bytes <= capacity_bytes`) before virtual
+     composites.
+  2. Among real titles, fewer clips first (1-clip wins).
+  3. Tiebreak on longer duration first.
+
+  **Migration:** consumers calling `disc.titles.first()` /
+  `disc.titles[0]` automatically get the corrected title — no code
+  changes needed. CLI users invoking `freemkv -t 1 disc:// …` now hit
+  the actual main feature on branching discs (this was the user-
+  visible bug). On non-branching discs the order is unchanged.
+
+  The comparator is exposed as
+  [`Disc::canonical_title_order`](#) for callers that need to
+  re-sort a custom title set with the same logic.
+
+  Regression tests: `disc::tests::canonical_order_*` (three cases:
+  branching-UHD, normal disc, clip-count tiebreak).
+
+## 0.18.2 (2026-05-09)
+
+### Bug fixes
+
+- **Nav-file scramble during AACS rip** (`decrypt::decrypt_sectors`). 0.18's
+  `DecryptingSectorSource` decorator broadened the call surface of
+  `decrypt_sectors` to every sector flowing through sweep, including UDF
+  navigation files (MPLS playlists, CLPI clip-info). The byte-0 heuristic
+  in `aacs::is_unit_encrypted` correctly fires on m2ts source-packet copy
+  markers but false-positives on any binary file whose first byte happens
+  to have the top 2 bits set — most notably MPLS files (start with 'M' =
+  0x4D) and CLPI files (start with 'H' = 0x48). `decrypt_unit_full`
+  already self-checks the result via TS-sync verification and returns
+  `false` on a misfire, but the chunk had been mutated by then;
+  `decrypt_sectors` discarded the return value, leaving scrambled bytes
+  in the ISO. Fix: snapshot the chunk before decryption and restore on
+  verification failure (same pattern `decrypt_unit_try_keys` already used
+  for multi-key discs). Symptom: `freemkv info iso://UHD.iso` and
+  `iso:// → mkv://` returned E6009 NoStreams on freshly-ripped UHD ISOs;
+  affected only the iso-source path, not the disc-source path or the
+  m2ts video payload itself. Regression test:
+  `decrypt::tests::nav_file_unit_survives_decrypt_attempt`.
+
+- **Sweep progress display can regress to zero** (`Disc::sweep`). The
+  consumer-side `bytes_good` snapshot lags producer-side `bytes_done`
+  whenever the consumer is behind on draining the work channel. Until
+  the first snapshot arrived, the placeholder branch reported
+  `bytes_done` correctly; once a stale snapshot landed, the report
+  switched to `snap.bytes_good` and could regress below `bytes_done`.
+  Fix: `bytes_good_total = max(snap.bytes_good, bytes_done)`, so the
+  user-visible counter never moves backward.
+
+## 0.18.1 (2026-05-09)
+
+### I/O stack redesign — primitives over orchestration
+
+0.18 reshapes the read/write surface from "library does the multipass dance"
+to "library hands the caller flat verbs and a few composable primitives." All
+in-tree consumers (autorip, the `freemkv` CLI) drove their own multipass
+loops in 0.18 rounds 1-3; 0.18.1 lands the cleanup with the deprecated names
+still alive for one minor-version window.
+
+The 0.18 design notes are kept privately — this entry sticks to
+what changed at the public surface.
+
+#### Flat verbs
+
+`Disc::sweep` is the forward Pass 1. `Disc::patch` is one retry pass over the
+mapfile. Neither knows about pass index, retry budget, or accept-loss policy
+— the caller invokes them in whatever sequence its use case dictates. The
+old multipass-aware `Disc::copy` dispatcher is deprecated and slated for
+deletion in 0.18.2; no in-tree caller still uses it.
+
+#### Trait splits — direction-typed at compile time
+
+- `pes::Stream` (combined read+write) is split into `FrameSource` and
+  `FrameSink`. Calling `read()` on a write-only sink is now a compile error,
+  not the runtime `E9001` (`StreamWriteOnly`) it used to be.
+- `SectorReader` is split into `SectorSource` (read) and `SectorSink`
+  (write). `Drive` impls `SectorSource` only; `FileSectorSource` /
+  `FileSectorSink` replace `FileSectorReader` for ISO-backed I/O.
+- A blanket impl bridges legacy `SectorReader` callers onto the new
+  `SectorSource` so existing code keeps compiling through the deprecation
+  window.
+
+#### New primitives
+
+- `Halt` — one cancellation token (cloneable, `Arc<AtomicBool>` under the
+  hood) replaces the three near-duplicate halt flags scattered through the
+  workspace. Threaded through every long-running loop.
+- `Pipeline<I, R>` + `Sink<I>` — generic producer/consumer primitive in
+  `crate::io`. Replaces the bespoke `disc/sweep_pipeline.rs` and now also
+  drives `Disc::patch` and the autorip mux loop. `DEFAULT_PIPELINE_DEPTH`
+  for streaming reads (`4`); `WRITE_THROUGH_DEPTH` for write-through patch
+  semantics (`1`).
+- `WritebackFile` — was `crate::io::Writer`. The renamed type makes its job
+  explicit: a `File` wrapper that runs continuous `sync_file_range` +
+  `posix_fadvise(DONTNEED)` to keep the kernel dirty-page cache bounded on
+  long sequential writes.
+- `DecryptingSectorSource<S>` — a single decorator wrapping any
+  `SectorSource` to yield plaintext sectors. One audit surface for AACS /
+  CSS / passthrough; the previous two-site decrypt (sweep producer +
+  `DiscStream` demux) is gone.
+
+#### Throughput
+
+The round-2 producer/consumer split is now applied uniformly to sweep,
+patch, and mux. Mux on NFS-staged UHD measured ~16 MB/s sustained on the
+test bed (was ~12 MB/s pre-round-2).
+
+#### Module reorg
+
+- `sector/` and `io/` are now module directories.
+- `disc/sweep.rs`, `disc/patch.rs`, and `disc/mapfile.rs` split out of the
+  monolithic `disc/mod.rs`.
+
+#### Renames (no behavior change)
+
+- `crate::io::Writer` → `crate::io::WritebackFile`.
+- `Apply` → `Flow` (`Sink::apply` return value).
+- `DEFAULT_DEPTH` → `DEFAULT_PIPELINE_DEPTH`.
+- `PatchOpts` → `PatchOptions`.
+
+#### Deprecated (alive in 0.18.1, deletion target 0.18.2)
+
+`Disc::copy`, `pes::Stream`, `SectorReader`, `FileSectorReader`,
+`CopyOptions`, `CopyResult`, `DiscStream::set_halt`. Each compiles with a
+deprecation warning; all in-tree call sites have migrated.
+
+## 0.17.13 (2026-05-09)
+
+### Use `crate::io::Writer` uniformly for all binary file output
+
+0.17.10 introduced the bounded-cache writeback wrapper (`sync_file_range`
++ `posix_fadvise(DONTNEED)` per chunk) and 0.17.11 wired it into
+`Disc::sweep`. The other two big-write paths in the crate were still
+opening raw `std::fs::File` and would have hit the same dirty-page
+burst pathology against slow / network-attached staging.
+
+This release threads `crate::io::Writer` through the remaining sites:
+
+- **`Disc::patch`** (`disc/mod.rs:1981`): the ISO file reopened for
+  Pass-N recovery now wraps in `Writer` before any seek / write.
+  Recovery writes are sparse, but the wrapper costs nothing when
+  there's no chunk crossing — and on heavily-damaged discs it
+  matters as patch accumulates GB of recovered data.
+- **MKV mux output** (`mux/resolve.rs:243`): `BufWriter::with_capacity`
+  now wraps `Writer::new(file)` instead of a raw `File`. UHD MKVs
+  routinely exceed 70 GB of sequential writes; pre-0.17.13 those
+  bursts went straight to the kernel writeback queue.
+- **M2TS mux output** (`mux/resolve.rs:251`): same change for
+  parity with the MKV path — anyone using `m2ts://` URLs gets it
+  too.
+
+No new public surface. `Writer::sync_all()` is called from `Disc::patch`
+and `sweep_pipeline`'s consumer at end of pass; mux exits via Drop on
+the wrapping `BufWriter`, which propagates flush down to `Writer`'s
+final `note_progress` (kernel finishes the in-flight chunk on file
+close — there's no explicit `sync_all` for mux today, same behaviour
+as before).
+
+## 0.17.12 (2026-05-09)
+
+### Mapfile time-batched persistence — unblock NFS staging
+
+Pre-0.17.12 every `Mapfile::record()` wrote the entire mapfile to disk
+via tempfile-create + buffered-write + atomic-rename. On local LVM
+that's effectively free (page cache + microsecond-scale renames). On
+NFS (autorip's intended staging path for centralised media) each
+record() became three RPCs through the unraid user share's shfs-fuse
+layer — measured end-to-end at multiple ms each. With ~170 record()
+calls per second of sustained sweep, the mapfile path alone burned
+multiple seconds of wall time per real-world second of work, dragging
+the rip from ~11 MB/s on local to ~1.5 MB/s on NFS.
+
+Fix: time-batch the persistence inside `Mapfile`.
+
+- `record()` always updates in-memory state and stats (so callers'
+  `stats()` reads stay coherent in the same process).
+- The `write_to_disk()` rename only fires when ≥ `FLUSH_INTERVAL`
+  (1 s) has elapsed since the last persist.
+- New `flush()` method forces an out-of-band persist; called by
+  `sweep_pipeline`'s consumer at end-of-sweep and by `Disc::patch` at
+  end-of-patch, after the file's `sync_all()`.
+- `Drop` impl best-effort flushes so an early-return / unwind doesn't
+  silently lose pending state.
+
+Crash-safety changes from "lose at most one block" to "lose at most
+1 s of recorded progress" — the ISO file's payload bytes are
+unaffected; only the mapfile's authority over which sectors are
+already-good is at risk, and a resume re-reads anything Pass 1 had
+already covered. Acceptable for a 7× throughput recovery on the
+target deployment.
+
+The internal `round_trip_load` test now calls `flush()` before
+`Mapfile::load` to read back what the in-memory state asserts.
+External patch / copy tests are unaffected: `patch` and
+`sweep_pipeline` flush at completion before returning, so any
+`Mapfile::load` at the call-site sees fully persisted state.
+
+## 0.17.11 (2026-05-09)
+
+### Sweep producer/consumer split — overlap drive read with file write
+
+Pre-0.17.11 the sweep loop ran strictly serialised: SCSI read → decrypt
+→ seek + write → mapfile.record → next read. The drive idled for the
+post-read work; throughput capped at the **sum** of both costs. On a
+healthy disc that's ~7-12 ms read + ~5-15 ms write/record per 64 KB
+batch — limiting sustained throughput to ~10-12 MB/s on the test bed
+(BU40N + UHD inner zone), well below the drive's ceiling of ~14-16 MB/s.
+
+This release decouples them with a producer / consumer split:
+
+- **Producer** (caller's thread): owns the `SectorReader`, the entire
+  `read_error` state machine (Retry, Bisect, SkipBlock, JumpAhead,
+  AbortPass), `set_speed` damage-zone transitions, halt check, and
+  decrypt. Hands plaintext bytes to the consumer.
+- **Consumer** (one spawned thread): owns the `crate::io::Writer` and
+  the `Mapfile`. Receives `WorkItem` messages and applies the file
+  write + mapfile record per item.
+- **Channel**: bounded `mpsc::sync_channel(4)` — natural back-pressure
+  via blocking `send` when consumer falls behind.
+
+While the consumer is writing batch N to disk and updating the mapfile,
+the producer is already reading batch N+1 from the drive. Steady-state
+throughput is now bound by the slower of the two pipelines (the drive,
+on a healthy disc) instead of their sum.
+
+Side effects of the refactor:
+
+- **Bisect path now decrypts.** Pre-0.17.11 the bisect inner loop wrote
+  raw cyphertext when `decrypt=true` and a single sector was recovered
+  via single-sector retry — a quiet correctness bug exercised only by
+  the (rare) batch-fail-then-bisect-succeed path on encrypted discs.
+  The new producer-side decrypt covers both the main success path and
+  the bisect inner success path.
+- All `read_error::ReadCtx` state stays single-threaded on the producer
+  (damage window, jump multiplier, consecutive-good count, etc.). No
+  locking added.
+- Mapfile remains single-writer (consumer-only). No locking.
+- Halt-flag responsiveness unchanged: producer breaks the loop on
+  signal, sends `Finish`, consumer drains its ≤4 in-flight items and
+  exits within ~1 batch (~12 ms typical).
+- BU40N + Initio bridge wedge concern unchanged: still one SCSI command
+  in flight, error-path timing identical, no new retry logic.
+
+New module: `src/disc/sweep_pipeline.rs` (`WorkItem`, `ProgressSnapshot`,
+`ConsumerInputs`, `spawn_consumer`, `consumer_loop`, send/recv helpers).
+Public API surface unchanged — `Disc::copy` / `CopyOptions` /
+`CopyResult` look identical to callers.
+
+Patch (Pass N) is **not** affected by this release. Patch is bound by
+drive recovery time (60 s timeouts on bad sectors), not the read↔write
+serialisation; a similar split there would yield negligible benefit.
+
+## 0.17.10 (2026-05-09)
+
+### Bounded-cache writeback for big sequential writes
+
+Pass 1 sweep speed on a healthy disc previously dipped from ~15 MB/s
+to ~1 MB/s every ~30 s on a host with default Linux dirty-page
+settings. Cause: the kernel's `vm.dirty_ratio` (~20 % of RAM) lets
+hundreds of MB of dirty pages accumulate, then bursts a flush at
+99 % disk utilisation that blocks app writes for ~1 s. Confirmed
+empirically on the BU40N test bed: dirty pages grew 112 → 563 MB
+between bursts; lowering `vm.dirty_bytes` to 64 MB at the host
+sysctl level eliminated the dips.
+
+This release ships the equivalent inside libfreemkv so users don't
+need to tune the host kernel:
+
+- New `crate::io::Writer` — drop-in `File` wrapper implementing
+  `Write` + `Seek`. Wraps a per-platform `WritebackPipeline` that on
+  Linux schedules `sync_file_range(WRITE)` + lagging
+  `sync_file_range(WAIT_AFTER)` + `posix_fadvise(DONTNEED)` calls in
+  32 MB chunks, keeping dirty cache bounded at ~64 MB. macOS and
+  Windows ship a no-op stub — their default cache policies don't
+  exhibit the same pathology for our access pattern.
+- Disc::sweep wraps its output `File` in `Writer`. No changes to the
+  loop body — `Writer` forwards `seek`/`write_all` to `File` and
+  drives the pipeline transparently.
+- Module is purpose-built for any large sequential output (sweep,
+  patch, future mux) — they can adopt `crate::io::Writer` with a
+  one-line wrapper and inherit the same behaviour.
+
+## 0.17.7 (2026-05-08)
+
+### Sync release — no functional libfreemkv changes
+
+Version bump to keep the four freemkv crates at unified versioning.
+autorip shipped UI smoothness + audit fixes today (v0.17.6, v0.17.7);
+libfreemkv carries no code changes, but is bumped + republished to
+crates.io so downstream `libfreemkv = "0.17"` consumers stay aligned
+on the latest patch version. See autorip CHANGELOG for the
+user-visible work in this release window.
+
+## 0.17.5 (2026-05-08)
+
+### Pass N recovery — kernel block-device fallback + per-range fixes
+
+Live testing on direct-SATA BU40N + AACS-encrypted UHD disc revealed that
+the v0.17.3 single-shot SCSI READ path matched 0/22 of the small bad-sector
+LBAs that `dd if=/dev/sr0` recovers on the same drive. This release closes
+that gap and fixes several adjacent bugs that were silently capping
+recovery.
+
+- **`/dev/sr0` pread fallback in `Drive::read` (Linux)**: when a SCSI READ
+  via `/dev/sg*` returns Err, fall back to `posix_fadvise(POSIX_FADV_DONTNEED)
+  + pread()` against the corresponding block device. The kernel `sr_mod`
+  driver runs ~5 internal retries per command without the per-attempt
+  error-escalation overhead that userspace SG_IO retries pay, which is the
+  source of dd's recovery advantage. End-to-end byte-verification confirms
+  the fallback path returns real disc data (md5-equivalent to fresh dd from
+  the same drive session). The block fd is opened in `Drive::open` by
+  resolving `/sys/class/scsi_generic/sgN/device/block`; best-effort, with no
+  fallback if open fails.
+
+- **`Disc::patch` per-range watchdog fix**: when a range hit `MAX_RANGE_SECS`,
+  the old code did `wedged_exit = true; break 'outer;` — a single slow range
+  killed the entire patch. Now `break;` (skip this range, advance the outer
+  for loop). Pre-fix, patch was dying after 4 sectors of the first slow
+  range and never reaching the other 46.
+
+- **Per-sector range budget**: replaced flat `MAX_RANGE_SECS = 180` with
+  `range_budget_secs = (range_sectors × SECONDS_PER_SECTOR).min(RANGE_BUDGET_CAP_SECS)`.
+  Tiny ranges exit fast (1-sector range = 25 s); medium ranges get
+  proportional time (51-sector range ≈ 1275 s); large ranges still bounded
+  by the 1800 s cap so they cannot monopolise pass 1.
+
+- **`consecutive_failures` resets per range**: the wedge-exit detector
+  (`>= 50 consecutive failures`) is for "stuck on the same range"; pre-fix
+  the counter persisted across ranges, so 50 small post-bisection ranges
+  with one failure each falsely tripped the wedge mid-pass. Reset at every
+  range boundary.
+
+- **Reverted inline 5× retry in patch**: a brief experiment that was
+  measurably harmful — each "2 s" SCSI timeout paid ~1.5 s kernel SCSI
+  mid-layer error-escalation overhead, so 5× retry took ~17 s per LBA and
+  triggered the per-range watchdog in 4 sectors. Restored
+  `READ_RECOVERY_TIMEOUT_MS = 60_000` (the v0.17.3 baseline; the kernel-
+  auto-retry pattern is now provided by the `/dev/sr0` fallback above).
+
+### Empirical results (a UHD disc, BU40N direct SATA)
+
+- Pass 1: **94.6 MB recovered** (28% of formerly-bad data, 33 sr0 fallback
+  saves), **11 s of main-title content** restored. Patch completed all 47
+  retryable ranges naturally (was wedging at range 1 of 47 in v0.17.3).
+- Pass 2 cumulative: 95.2 MB (+0.6 MB; diminishing returns curve).
+- Remaining ~233 MB on the test disc appears physically unrecoverable on
+  this hardware (kernel auto-retry can't decode it either).
+
+### Behavioural notes
+
+- The `/dev/sr0` fallback is Linux only; macOS and Windows fall back to
+  the existing single-shot SCSI behaviour. The fallback is gated to
+  `recovery=true` reads (only fires from the patch path, not the sweep
+  path) to avoid page-cache pressure during multi-GB sequential ripping.
+
+## 0.17.0 (2026-05-04)
+
+### Code quality: unwrap safety, clippy compliance, test coverage
+
+- **Sweep() hot path**: Replaced `.err().unwrap()` in `disc/mod.rs:1553` with explicit pattern matching (`match read_result { Ok(_) => unreachable!(), Err(e) => e }`). The original unwrap was logically safe (in the else branch after `is_ok()` check) but pattern matching makes the invariant explicit and avoids panic risk if logic changes.
+- **cargo clippy --lib**: Clean build with `-D warnings` across all targets. No lint failures.
+- **cargo test --lib**: All 256 tests pass (0 failed, 1 ignored). Integration tests for sweep/patch/dev-null validate the multi-pass recovery pipeline end-to-end.
+
+### Patch pass algorithm fix
+
+- `patch_internal` excludes Unreadable sectors from work list (only retries NonTrimmed/NonScraped/Unscraped). Previously attempted to retry already-failed sectors, wasting time and masking real progress.
+- Exposes `bytes_bad_in_title` in patch results for accurate UI reporting of unrecoverable data vs. recovered data.
+
 ## 0.16.1 (2026-04-30)
 
 ### Unified progress display for sweep and patch
@@ -99,7 +948,7 @@ bridges (notably the Initio INIC-1618L) that crash on MEDIUM ERROR retries.
 - Patch instrumentation: counters for reads_ok/err, writes_ok/err, finished/unreadable.
 - `as_encoded_bytes()` replaces `as_bytes()` for portable OsStr handling.
 - Removed inline retry/reset from Drive::read — orchestration layer handles recovery.
-- Removed all `(internal)` references from public code.
+- Removed all internal references from public code.
 
 ## 0.13.26 (2026-04-27)
 
@@ -127,7 +976,7 @@ warnings` red on Linux CI that the Mac toolchain doesn't catch.
 
 ### Pre-commit gate uses CI's exact toolchain
 
-`(internal)/scripts/precommit.sh` (new) runs `cargo +1.86 fmt
+A new pre-commit script runs `cargo +1.86 fmt
 --check`, `cargo +1.86 clippy -- -D warnings`, and `cargo +1.86 test
 --tests` across all 5 freemkv crates. Mirrors each repo's
 `.github/workflows/ci.yml` step-for-step. Use it as a pre-commit hook
@@ -169,7 +1018,7 @@ Through the entire 0.13.x line, every CHECK CONDITION reply from the
 drive (the standard way SCSI reports a sector failure) was being
 collapsed into a synthetic `status=0xFF, sense_key=0` "transport
 wedge" sentinel and the real sense data was thrown away. Live tracing
-on the BU40N reading Dune 2 on 2026-04-27 confirmed it: the drive was
+on the BU40N reading a UHD disc on 2026-04-27 confirmed it: the drive was
 returning `host_status=0, driver_status=8, status=2, exec_elapsed_ms=1416`
 on every bad sector — a clean CHECK CONDITION carrying full sense
 data — and the library was misclassifying it as a wedge and bailing.
@@ -241,7 +1090,7 @@ recovered or marked Unreadable. Calibration data
 
 ### Replace bisect-on-fail with hysteresis state machine (Block ↔ Single)
 
-Live test on Dune 2 v0.13.21 showed bisect-on-fail recovered every
+Live test on a UHD disc v0.13.21 showed bisect-on-fail recovered every
 recoverable sector, but spent ~30 sec per damaged 60-block (paying a
 ~5 sec kernel timeout at every bisection level). Each level descended
 log₂(60) ≈ 6 times on the failing branch.
@@ -270,7 +1119,7 @@ Per-block cost on a 60-sector damaged block with 1 bad sector:
 
 Plus inside a damaged cluster spanning many 60-blocks, hysteresis
 pays the bpt=batch fail cost ONCE on entry; bisection paid it every
-60 sectors. For Dune 2's ~1248-sector boundary cluster that's ~21
+60 sectors. For the ~1248-sector boundary cluster that's ~21
 fewer 5-sec waits = ~100 sec saved.
 
 Telemetry: new `phase=mode_change` trace event with `from`, `to`,
@@ -288,8 +1137,7 @@ synthetic BU40N-pattern reader; same 100% recovery expectation.
 ### Fix: Disc::copy bisect-on-fail (replaces skip-forward)
 
 Empirical live-hardware testing on the LG BU40N (see
-`(internal)/docs/audits/2026-04-26-test-plan-audit.md` and the
-TEST_PLAN.md run log) revealed that the drive often **fails
+the internal test-plan audit and run log) revealed that the drive often **fails
 multi-sector READ commands** in damaged regions but **succeeds when
 asked one sector at a time**. The old skip-forward strategy responded
 to multi-sector failures by jumping up to 1 % of the disc forward,
@@ -301,7 +1149,7 @@ half, retry each half, recurse down to single-sector reads. Sectors
 the drive can read individually are recovered in Pass 1; only sectors
 that fail at bpt=1 are marked NonTrimmed for the patch passes.
 
-Empirical results on Dune 2 UHD on the BU40N:
+Empirical results on a UHD disc on the BU40N:
 - Old algorithm: 25 GB read in Pass 1, then ~6 GB skip-forwarded;
   retry passes failed to recover most of the skipped zone.
 - New algorithm: ~99 % of disc recovered in Pass 1; only the truly
@@ -343,7 +1191,7 @@ LUN/BUS/HOST reset. `READ_RECOVERY_TIMEOUT_MS` (60 s) unchanged.
 `ioctl(fd, SG_IO, &hdr)`. The old pattern abandoned slow-but-alive
 commands faster than the drive could drain its internal queue,
 deepening the BU40N wedge. Per the audit at
-`(internal)/docs/audits/2026-04-26-scsi-architecture-research.md`,
+internal SCSI-architecture research,
 no reference project (MakeMKV / sg_dd / ddrescue) does what we did —
 all use sync blocking SG_IO with 8-60 s timeouts and let the kernel's
 mid-layer (`scsi_eh.rst`) run ABORT TASK / LUN RESET / BUS RESET /
@@ -470,7 +1318,7 @@ clean reads (Finished sectors) and freezes during skip-forward bad zones,
 which made every previous version's UI look hung at the bad-zone boundary.
 This was the v0.13.9 stall-guard origin bug.
 
-Live trace from v0.13.14: Pass 1 hit a Dune 2 bad zone at 24 GB and
+Live trace from v0.13.14: Pass 1 hit a bad zone at 24 GB and
 appeared "stuck" for 14 minutes per autorip's UI (`bytes_good = 23.97 GB`
 unchanged). Disc trace events showed `pos` actually advanced from 25.8 GB
 to 70 GB during that window — Pass 1 was 83 % through the disc, marking
@@ -518,7 +1366,7 @@ trace events were silently dropped by the default `libfreemkv=warn` rule.
 
 ### Telemetry: instrument the rip pipeline for in-flight diagnosis
 
-v0.13.12 shipped Fix 1+2+4 + cross-platform parity but a live test on Dune 2
+v0.13.12 shipped Fix 1+2+4 + cross-platform parity but a live test
 showed Pass 1 sat for 14 minutes with `bytes_good=0` while the inner loop
 appeared to iterate (the throttled `on_progress` log fired every 78s). The
 async fd_recovery design at §7 said each `execute()` call should bound at
@@ -562,7 +1410,7 @@ The v0.13.9 stall guard at `disc/mod.rs` exited Pass 1 early when
 `bytes_good` was flat for `stall_secs` (default 120s). This violated the
 ddrescue model: Pass 1 must sweep end-to-end, marking failed reads
 NonTrimmed for Pass 2 retry. The guard caused Pass 1 to bail at 30% on
-Dune 2 with 56 GB still NonTried, leaving Pass 2 nothing useful to do.
+a UHD disc with 56 GB still NonTried, leaving Pass 2 nothing useful to do.
 
 - Deleted the stall-guard state vars and the `if cur_good != ...
   break 'outer;` block.
@@ -617,7 +1465,7 @@ same observable recovery contract as Linux:
 
 `PatchResult` now reports `blocks_attempted`, `blocks_read_ok`,
 `blocks_read_failed`. Pass 2's "100 minutes recovered 0 bytes" mystery
-(Dune 2) becomes diagnosable from these counters: distinguish "drive
+(a UHD disc) becomes diagnosable from these counters: distinguish "drive
 returned Ok but write/record dropped data" from "every read was Err for
 the entire range" without instrumenting from outside the lib.
 
@@ -646,7 +1494,7 @@ against the spawned close()). The intent was to escape the 60-s
 blocking reopen.
 
 The cost was too high: a single transient poll timeout permanently
-killed the transport. Live test on Dune 2 (post-replug):
+killed the transport. Live test on a UHD disc (post-replug):
 - Pass 1 ran for **45 ms** then returned with 0 GB good and 80 GB
   pending.
 - The first SCSI READ timed out, fd went to -1, every subsequent
@@ -679,7 +1527,7 @@ Sync bump for the autorip-side fix in 0.13.10 (Pass 1 batch reporting).
 ### Fix: Disc::copy silent stall + SgIoTransport reopen-after-timeout serialization
 
 Two correlated fixes for a hang observed live on the LG BU40N during a
-v0.13.8 rip of Dune: Part Two. At ~30 % progress through Pass 1
+v0.13.8 rip of a UHD disc. At ~30 % progress through Pass 1
 (disc → ISO), `bytes_good` froze for 10+ minutes with `errs=0`,
 no error surfaced, drive not wedged.
 
@@ -1566,10 +2414,9 @@ Rip recovery rewritten. The old binary-search-per-bad-sector model paid the full
 - **Kernel transfer limit detection**: auto-detect `max_hw_sectors_kb` via sysfs, resolve sg→block device. Previously hardcoded to 510 sectors (1MB) which exceeded the 120KB kernel limit, causing all reads to error and fall back to 6KB reads at 4.8 MB/s. Now auto-tunes to 48 sectors (96KB) or whatever the device supports.
 - **Result: 12.5 MB/s sustained, 23 MB/s peak** (was 4.8 MB/s)
 
-### LibreDrive — full init pipeline
+### Drive init pipeline
 
-- **All 10 ARM handlers translated**: unlock, firmware upload (A: WRITE_BUFFER, B: MODE SELECT), calibrate (256 zones), register reads, status, probe, set_read_speed, keepalive, timing
-- **Cold boot firmware upload**: WRITE_BUFFER 1888B (A variant) or MODE SELECT 2496B (B variant) proven on hardware
+- **Full drive init pipeline**: unlock, calibrate (256 zones), register reads, status, probe, set_read_speed, keepalive, timing
 - **Speed calibration**: 256+ disc surface probes, 64-entry speed table, triple SET_CD_SPEED
 - **Platform trait locked down**: `pub(crate)`, 3 methods only (init, set_read_speed, is_ready)
 - **Init guard**: prevents double-init, signature mismatch aborts early
@@ -1584,7 +2431,7 @@ Rip recovery rewritten. The old binary-search-per-bad-sector model paid the full
 ### Profiles
 
 - **206 profiles with full per-drive data**: ld_microcode (base64), all CDBs, speed tables, signatures
-- **Automated pipeline**: `sdf_unpack --profiles` → profiles.json (no manual merging)
+- **Automated pipeline**: profile import → profiles.json (no manual merging)
 
 ## 0.4.0 (2026-04-07)
 

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "libfreemkv"
-version = "0.16.2"
+version = "0.30.0"
 edition = "2024"
 rust-version = "1.86"
 license = "AGPL-3.0-only"
@@ -8,6 +8,8 @@ description = "Open source raw disc access library for optical drives"
 repository = "https://github.com/freemkv/libfreemkv"
 keywords = ["bluray", "uhd", "optical", "scsi", "disc"]
 categories = ["hardware-support", "multimedia"]
+# Keep internal AI-instruction / private notes out of the published crate.
+exclude = []
 
 [dependencies]
 serde = { version = "1", features = ["derive"] }
@@ -28,6 +30,22 @@ base64 = "0.22.1"
 # under project docs ("Acceptable strings: debug/trace logging"). Consumers (autorip)
 # wire a tracing subscriber and pipe events into the JSONL debug log.
 tracing = "0.1"
+# Bounded MPSC channel with kernel-wakeup send_timeout. Used by `io::pipeline`
+# so the halt-aware send/finish loops can BLOCK on consumer drain instead of
+# polling — the 50 ms poll cadence of the previous mpsc-based impl capped mux
+# throughput at ~1 MB/s (0.21.7).
+crossbeam-channel = "0.5"
+# Persistent work-stealing thread pool for parallel AACS unit
+# decryption. Per-call std::thread::scope spawned fresh OS threads
+# and that overhead dominated for typical batch sizes (60 units).
+# rayon's global pool initialises once on first use.
+rayon = "1"
+# SIMD-accelerated bytestring search. Drives the HEVC/H.264 start-code
+# scan in `mux::codec::h264::find_start_code` — naive byte-by-byte
+# walk is ~500 MB/s single-thread on x86_64; memchr's vectorised
+# `memmem::find` for the 3-byte `00 00 01` needle hits ~5 GB/s on
+# AVX2-capable hosts.
+memchr = "2"
 
 [target.'cfg(target_os = "linux")'.dependencies]
 libc = "0.2"

FEATURES.md

@@ -1,34 +0,0 @@
-# libfreemkv — Feature List
-
-## v0.10.10 (current)
-
-### Done
-- [x] Drive access: open, identify, unlock, firmware upload, speed calibration, eject
-- [x] 206 bundled drive profiles (MediaTek MT1959 A + B variants)
-- [x] SCSI transport: Linux SG_IO, macOS IOKit, Windows SPTI
-- [x] UDF 2.50 filesystem parser (metadata partitions, Blu-ray profile)
-- [x] MPLS playlist parser (play items, STN table, secondary streams)
-- [x] CLPI clip info parser (EP map, sector extents)
-- [x] AACS 1.0 decryption (4 VUK paths: KEYDB, media key, processing key, device key)
-- [x] AACS 2.0 SCSI handshake (P-256/SHA-256 ECDH, bus decryption, read data key)
-- [x] DVD IFO parser (VMG, VTS, PGC chains, cell addresses)
-- [x] DVD CSS decryption (bus auth, disc key via player keys, title key, sector descramble)
-- [x] CSS Stevenson plaintext attack for ISO key recovery
-- [x] MPEG-2 PS demuxer (DVD Program Stream with PES extraction)
-- [x] MPEG-2 video codec parser (sequence header, quantizer matrices, keyframe detection)
-- [x] KEYDB.cfg download, verify, save (raw TCP, zero HTTP deps)
-- [x] Content reading with adaptive batch sizing, error recovery, 12+ MB/s
-- [x] Stream labels: 5 BD-J format parsers (Paramount, Criterion, Pixelogic, CTRM, Deluxe)
-- [x] MKV muxer: 14 codec parsers (H.264, HEVC, MPEG-2, AC-3, DTS, TrueHD, PGS, DVD Sub, VC-1, LPCM, +4 more)
-- [x] SectorReader trait: decouples disc scanning from SCSI
-- [x] 7 stream types: Disc, ISO, MKV, M2TS, Network, Stdio, Null
-- [x] PES pipeline with unified Stream trait (any source → any dest)
-- [x] FMKV metadata header for M2TS and network streams
-- [x] Numeric error codes only (no English text in library)
-- [x] Event system for progress callbacks
-
-### Planned
-- [ ] Windows testing on real hardware
-- [ ] Pioneer Renesas platform support (48 drives, need GET_CONFIG 010C)
-- [ ] TranscodeStream (ffmpeg integration)
-- [ ] ISO write with BD-compliant UDF structure

Makefile

@@ -1,6 +1,5 @@
 # libfreemkv — local dev helper.
-# Mirrors the cross-crate scripts in (internal)/scripts/test-all.sh
-# but scoped to this single crate.
+# Mirrors the workspace-wide CI checks but scoped to this single crate.
 
 .PHONY: test build check ci clean
 

README.md

@@ -6,6 +6,8 @@
 
 Rust library for 4K UHD / Blu-ray / DVD optical drives. Drive access, disc scanning, stream labels, AACS decryption, CSS decryption, KEYDB updates, and content reading in one crate. Bundled drive profiles — no external files needed.
 
+Built-in keys cover DVDs and Blu-rays (AACS 1.0). For UHD (AACS 2.0 / 2.1) discs, an optional `keydb.cfg` supplies disc-specific volume unique keys.
+
 **12+ MB/s** sustained read speeds on BD. Full init: unlock, firmware upload, speed calibration — all from pure Rust.
 
 Multi-lingual by design — the library outputs structured data and numeric error codes, never English text. Build any UI or localization on top.
@@ -18,7 +20,7 @@ Part of the [freemkv](https://github.com/freemkv) project.
 
 ```toml
 [dependencies]
-libfreemkv = "0.13"
+libfreemkv = "0.25"
 ```
 
 ## Quick Start
@@ -53,27 +55,47 @@ output.finish()?;
 
 ### Multi-pass recovery rip
 
-For damaged discs, the library offers a two-stage rip model: fast sweep with zero-fill and a ddrescue-format mapfile, then targeted retry of bad ranges. See [`docs/rip-recovery.md`](docs/rip-recovery.md) for the full architecture.
+For damaged discs the library exposes two flat verbs — `Disc::sweep` for the
+forward Pass 1 and `Disc::patch` for retrying bad ranges. The library never
+loops; the multipass policy is the caller's job. See
+[`docs/rip-recovery.md`](docs/rip-recovery.md).
 
 ```rust
-use libfreemkv::disc::{CopyOptions, PatchOptions};
+use libfreemkv::{SweepOptions, PatchOptions};
+use libfreemkv::disc::{mapfile, mapfile_path_for};
+use std::path::Path;
 
-// Pass 1: disc → ISO. Fast 64 KB reads, skip-forward on failure,
-// zero-fill bad blocks, write a sidecar .mapfile.
-let mut result = disc.copy(
-    &mut drive,
-    Path::new("disc.iso"),
-    &CopyOptions { skip_on_error: true, skip_forward: true, ..Default::default() },
-)?;
+let iso = Path::new("disc.iso");
 
-// Pass 2..N: retry bad ranges with full drive recovery.
-// Idempotent — call as many times as you want.
-while result.bytes_unreadable + result.bytes_pending > 0 {
-    let pr = disc.patch(&mut drive, Path::new("disc.iso"), &PatchOptions::default())?;
-    if pr.bytes_recovered_this_pass == 0 { break; }
+// Pass 1: disc → ISO. Skip-on-error, zero-fill, write the sidecar mapfile.
+disc.sweep(&mut drive, iso, &SweepOptions {
+    decrypt: true,
+    resume: false,
+    batch_sectors: None,
+    skip_on_error: true,
+    progress: None,
+    halt: None,
+})?;
+
+// Pass 2..N: retry every non-finished range. Idempotent.
+loop {
+    let map = mapfile::Mapfile::load(&mapfile_path_for(iso))?;
+    let stats = map.stats();
+    if stats.bytes_pending + stats.bytes_unreadable == 0 { break; }
+
+    let outcome = disc.patch(&mut drive, iso, &PatchOptions {
+        decrypt: true,
+        block_sectors: None,
+        full_recovery: true,
+        reverse: true,
+        wedged_threshold: 50,
+        progress: None,
+        halt: None,
+    })?;
+    if outcome.bytes_recovered_this_pass == 0 { break; }
 }
 
-// Then mux from the ISO via the normal stream pipeline (no drive involvement).
+// Mux from the ISO via the normal stream pipeline (no drive involvement).
 ```
 
 ## What It Does
@@ -92,16 +114,20 @@ while result.bytes_unreadable + result.bytes_pending > 0 {
 | Stream | Input | Output | Transport |
 |--------|-------|--------|-----------|
 | DiscStream | Yes | -- | Optical drive via SCSI |
-| IsoStream | Yes | -- | Blu-ray ISO image file (read via stream pipeline; written via `Disc::copy()`) |
+| IsoStream | Yes | -- | Blu-ray ISO image file (read via stream pipeline; written via `Disc::sweep()`) |
 | MkvStream | Yes | Yes | Matroska container |
 | M2tsStream | Yes | Yes | BD transport stream with FMKV metadata header |
 | NetworkStream | Yes (listen) | Yes (connect) | TCP with FMKV metadata header |
 | StdioStream | Yes (stdin) | Yes (stdout) | Raw byte pipe |
 | NullStream | -- | Yes | Discard sink (byte counter for benchmarks) |
 
-Streams implement `pes::Stream` (frame-level). `input()` / `output()` resolve URL strings to PES stream instances. All URLs use the `scheme://path` format — bare paths are rejected.
+Streams implement `FrameSource` (read) and/or `FrameSink` (write); direction is type-checked. `input()` / `output()` resolve URL strings to PES stream instances. All URLs use the `scheme://path` format — bare paths are rejected.
 
-AACS decryption requires a KEYDB.cfg file. If available at `~/.config/aacs/KEYDB.cfg` or passed via `ScanOptions`, the library handles everything — handshake, key derivation, and per-sector decryption — without the application needing to know anything about encryption.
+### Keys
+
+DVDs (CSS) decrypt out of the box — the 1999-era public player keys are compiled into the library.
+
+Blu-rays and UHD (AACS) require a `keydb.cfg` at `~/.config/freemkv/keydb.cfg` (or passed via `ScanOptions`). The file holds all DKs, PKs, host certs, and per-disc VUKs. No AACS key material is compiled into the binary.
 
 ## Architecture
 
@@ -122,7 +148,8 @@ Disc                   — scan titles, streams, AACS/CSS state
   └── KEYDB            — download + verify + save
 
 Streams                — unified PES pipeline
-  ├── pes::Stream      — read()/write() PES frames
+  ├── FrameSource      — read() PES frames (direction-typed)
+  ├── FrameSink        — write() PES frames (direction-typed)
   ├── DiscStream       — sectors → decrypt → TS demux → PES
   ├── IsoStream        — ISO file → decrypt → TS demux → PES
   ├── MkvStream        — MKV mux/demux

docs/api-design.md

@@ -44,35 +44,30 @@ while let Ok(Some(frame)) = input.read() {
 output.finish()?;
 ```
 
-The `pes::Stream` trait:
+The `FrameSource` and `FrameSink` traits — direction is type-checked, so
+calling `read()` on a write-only sink (or `write()` on a read-only source)
+is a compile error rather than a runtime fault:
 
 ```rust
-pub trait Stream {
-    fn read(&mut self) -> io::Result<Option<PesFrame>>;
-    fn write(&mut self, frame: &PesFrame) -> io::Result<()>;
-    fn finish(&mut self) -> io::Result<()>;
+pub trait FrameSource: Send {
+    fn read(&mut self) -> Result<Option<PesFrame>, Error>;
     fn info(&self) -> &DiscTitle;
-    fn codec_private(&self, track: usize) -> Option<Vec<u8>>;
-    fn headers_ready(&self) -> bool;
+    fn codec_private(&self, track: usize) -> Option<Vec<u8>> { None }
+    fn headers_ready(&self) -> bool { true }
 }
-```
 
-## IOStream (byte-level API)
-
-For raw byte copies (disc→ISO, resume, benchmarks). Lower level than PES.
-
-```rust
-let opts = InputOptions::default();
-let mut input = open_input("iso://Disc.iso", &opts)?;
-let mut output = open_output("mkv://Movie.mkv", input.info())?;
-io::copy(&mut *input, &mut *output)?;
-output.finish()?;
+pub trait FrameSink: Send {
+    fn write(&mut self, frame: &PesFrame) -> Result<(), Error>;
+    fn finish(self: Box<Self>) -> Result<(), Error>;
+    fn info(&self) -> &DiscTitle;
+}
 ```
 
 ## Streams
 
-All streams implement `IOStream` (byte-level) and/or `pes::Stream` (frame-level).
-URL-based resolvers open any stream by string.
+All streams implement `FrameSource` (read) and/or `FrameSink` (write); the
+directional split prevents runtime "wrong-direction" errors. URL-based
+resolvers open any stream by string.
 
 | Stream | Input | Output | URL | Transport |
 |--------|-------|--------|-----|-----------|
@@ -87,21 +82,14 @@ URL-based resolvers open any stream by string.
 All URLs require a `scheme://path` format. Bare paths are rejected.
 
 ```rust
-// PES pipeline (frame-level)
+// PES pipeline (frame-level) — input() returns Box<dyn FrameSource>,
+// output() returns Box<dyn FrameSink>.
 let input = libfreemkv::input("disc:///dev/sg4", &opts)?;    // DiscStream
-let input = libfreemkv::input("iso://Dune.iso", &opts)?;     // IsoStream
-let output = libfreemkv::output("mkv://Dune.mkv", &title)?;  // MkvOutputStream
-let output = libfreemkv::output("m2ts://Dune.m2ts", &title)?; // M2tsOutputStream
-let output = libfreemkv::output("network://10.0.0.1:9000", &title)?; // NetworkOutputStream
+let input = libfreemkv::input("iso://Movie.iso", &opts)?;     // IsoStream
+let output = libfreemkv::output("mkv://Movie.mkv", &title)?;  // MkvOutputStream
+let output = libfreemkv::output("m2ts://Movie.m2ts", &title)?; // M2tsOutputStream
+let output = libfreemkv::output("network://192.0.2.10:9000", &title)?; // NetworkOutputStream
 let output = libfreemkv::output("null://", &title)?;          // NullOutputStream
-
-// IOStream (byte-level)
-let input = open_input("disc://", &opts)?;                    // DiscStream
-let input = open_input("iso://Dune.iso", &opts)?;             // IsoStream
-let output = open_output("iso://Copy.iso", &meta)?;           // IsoStream (write)
-let output = open_output("mkv://Dune.mkv", &meta)?;           // MkvStream
-let output = open_output("m2ts://Dune.m2ts", &meta)?;         // M2tsStream
-let output = open_output("null://", &meta)?;                  // NullStream
 ```
 
 ### FMKV Metadata Header
@@ -175,20 +163,34 @@ libfreemkv/src/
 ├── lib.rs              Public exports
 ├── error.rs            Error codes (no English)
 ├── event.rs            Event types for callbacks
+├── halt.rs             Halt cancellation token (Arc<AtomicBool> wrapper)
+├── io/                 Pipeline + WritebackFile primitives
+│   ├── mod.rs          Re-exports WritebackFile, Pipeline, Sink, Flow
+│   ├── pipeline.rs     Generic Pipeline<I, R> + Sink trait
+│   ├── writeback_file.rs  WritebackFile (was crate::io::Writer)
+│   └── writeback.rs    sync_file_range pipeline
 ├── drive/              Drive (open, init, single-shot read)
 │   ├── mod.rs          Drive struct, init, read (single-shot), reset, eject
 │   ├── capture.rs      Drive profile capture for contribution
 │   ├── linux.rs        Linux drive discovery
 │   ├── macos.rs        macOS drive discovery
 │   └── windows.rs      Windows drive discovery
-├── disc/               Disc (scan, titles, AACS setup)
+├── disc/               Disc (scan, titles, AACS setup, sweep, patch)
+│   ├── mod.rs          Disc struct, scan, titles, formats
+│   ├── sweep.rs        Disc::sweep (Pass 1 forward sweep)
+│   ├── patch.rs        Disc::patch (Pass N retry over mapfile)
+│   ├── mapfile.rs      ddrescue-format mapfile
+│   └── read_error.rs   ReadCtx / ReadAction state machine
 ├── scsi/               SCSI transport (Linux SG_IO, macOS IOKit, Windows SPTI)
 ├── platform/           Drive unlock (MT1959 A/B)
 ├── aacs/               AACS decryption (handshake, keys, keydb, decrypt)
 ├── css/                DVD CSS cipher
 ├── decrypt.rs          Unified decrypt dispatcher (AACS/CSS/None)
-├── pes.rs              PES frame types, Stream trait
-├── sector.rs           SectorReader trait
+├── pes.rs              PES frame types, FrameSource / FrameSink traits
+├── sector/             Sector I/O (was sector.rs in 0.17)
+│   ├── mod.rs          SectorSource, SectorSink traits
+│   ├── file.rs         FileSectorSource, FileSectorSink (ISO-backed)
+│   └── decrypting.rs   DecryptingSectorSource decorator
 ├── udf.rs              UDF 2.50 filesystem parser
 ├── mpls.rs             MPLS playlist parser
 ├── clpi.rs             CLPI clip info parser
@@ -199,15 +201,15 @@ libfreemkv/src/
 ├── profile.rs          Bundled drive profiles
 ├── speed.rs            DriveSpeed enum
 ├── mux/
-│   ├── mod.rs          IOStream trait, public exports
-│   ├── resolve.rs      URL parser + open_input/open_output + input/output
+│   ├── mod.rs          Public mux exports
+│   ├── resolve.rs      URL parser + input/output (Box<dyn FrameSource/Sink>)
 │   ├── meta.rs         FMKV header format
 │   ├── disc.rs         DiscStream (optical drive → PES)
-│   ├── iso.rs          IsoStream (ISO image read/write)
+│   ├── iso.rs          IsoStream (ISO image read)
 │   ├── isowriter.rs    ISO image writer (UDF, AVDP, multi-extent)
-│   ├── mkvstream.rs    MkvStream (bidirectional Matroska, IOStream)
+│   ├── mkvstream.rs    MkvStream (bidirectional Matroska)
 │   ├── mkvout.rs       MkvOutputStream (PES → MKV)
-│   ├── m2ts.rs         M2tsStream (BD-TS, IOStream)
+│   ├── m2ts.rs         M2tsStream (BD-TS)
 │   ├── pesout.rs       PES output streams (M2ts, Network, Stdio, Null)
 │   ├── network.rs      NetworkStream (TCP + FMKV header)
 │   ├── stdio.rs        StdioStream (stdin/stdout pipe)

docs/architecture.md

@@ -65,8 +65,12 @@ libfreemkv (lib.rs)
 │
 ├── Streaming
 │   ├── mux/          Stream implementations (Disc, ISO, MKV, M2TS, Network, Stdio, Null)
-│   ├── pes           PES frame types, Stream trait (read/write frames)
-│   └── sector        SectorReader trait — abstracts disc vs ISO vs file
+│   ├── pes           PES frame types; FrameSource / FrameSink direction-typed traits
+│   └── sector/       SectorSource / SectorSink traits, FileSector{Source,Sink}, DecryptingSectorSource
+│
+├── I/O Primitives
+│   ├── halt          Halt cancellation token (one Arc<AtomicBool>, cloneable)
+│   └── io/           Pipeline<I, R> + Sink trait + WritebackFile (bounded-cache writer)
 │
 ├── Support
 │   ├── keydb         KEYDB.cfg download, parse, verify, save

docs/disc-to-rip.md

@@ -97,7 +97,9 @@ drive.probe_disc()?;
 // Scan disc (UDF + playlists + AACS — all automatic)
 let disc = Disc::scan(&mut drive, &ScanOptions::default())?;
 
-// Stream pipeline — PES frames from any source to any output
+// Stream pipeline — PES frames from any source to any output.
+// 0.18: input() returns Box<dyn FrameSource>, output() returns Box<dyn FrameSink>;
+// direction is type-checked, so calling .write() on an input is a compile error.
 let opts = InputOptions::default();
 let mut input = libfreemkv::input("disc:///dev/sg4", &opts)?;
 let title = input.info().clone();
@@ -121,11 +123,13 @@ output.finish()?;
 | aacs/ | [aacs.md](aacs.md) | Key resolution + content decrypt + bus handshake |
 | css/ | -- | DVD CSS cipher |
 | decrypt.rs | -- | Unified decrypt dispatcher (AACS/CSS/None) |
-| disc/ | -- | High-level scan + read API |
+| disc/ | [rip-recovery.md](rip-recovery.md) | Disc::scan + Disc::sweep + Disc::patch + mapfile |
 | labels/ | -- | BD-J stream labels (5 format parsers) |
 | mux/ | -- | Stream implementations (7 stream types) |
-| pes.rs | -- | PES frame types + Stream trait |
-| sector.rs | -- | SectorReader trait |
+| pes.rs | -- | PES frame types + FrameSource / FrameSink traits |
+| sector/ | -- | SectorSource / SectorSink + DecryptingSectorSource decorator |
+| io/ | -- | Pipeline<I, R> + Sink trait + WritebackFile |
+| halt.rs | -- | Halt cancellation token |
 | keydb.rs | -- | KEYDB download, parse, save |
 | error.rs | -- | Error codes (E1xxx-E8xxx) |
 | event.rs | -- | Drive event system |

docs/drive-access.md

@@ -52,8 +52,8 @@ selects the per-CDB timeout:
 
 | `recovery` | Timeout  | Used by                                  |
 |------------|----------|------------------------------------------|
-| `false`    | 1.5 s    | `Disc::copy` fast skip-forward sweep, `DiscStream::fill_extents` |
-| `true`     | 30 s     | `Disc::patch` multi-pass over the mapfile |
+| `false`    | 1.5 s    | `Disc::sweep` fast skip-forward pass, `DiscStream::fill_extents` |
+| `true`     | 30 s     | `Disc::patch` retry pass over the mapfile |
 
 On any SCSI failure or timeout, `read` returns `Err(DiscRead)` immediately.
 There are no inline retries, no SCSI reset, no Phase 1/2/3 escalation.

docs/rip-recovery.md

@@ -12,21 +12,24 @@ reach into the others.
 
 | Layer | Where it lives | What it does |
 |-------|---------------|--------------|
-| 1 — Bad-range retry | `Disc::patch` (multi-pass over the mapfile) | Re-reads non-`+` ranges with the long timeout. Idempotent; call N times. |
+| 1 — Bad-range retry | `Disc::patch` (one pass over the mapfile per call) | Re-reads non-`+` ranges with the long timeout. Idempotent; caller invokes N times. |
 | 2 — Single-shot primitive | `Drive::read` in `src/drive/mod.rs` | One CDB, one timeout, one result. No inline retries, no SCSI reset. |
 | 3 — In-loop request adaptation | `DiscStream::fill_extents` adaptive batch sizer | Halves the batch on failure, retries at the same LBA, walks back up on a clean-read streak. |
 
-The caller orchestrates layer 1. Autorip's `rip_disc` loops `copy` then
-N × `patch` per the `MAX_RETRIES` config, then hands the ISO off to the
-existing mux pipeline. Layer 3 runs inside any consumer of `DiscStream`
-(direct PES pipeline, ISO playback, etc.) without caller involvement.
+The library exposes flat verbs; the caller drives the multipass loop. Autorip
+runs `Disc::sweep` once, then loops `Disc::patch` until either the mapfile is
+clean or the configured retry budget is exhausted, then hands the ISO off to
+the mux pipeline. The `freemkv` CLI does the same shape with a
+terminal-output progress sink. Layer 3 runs inside any consumer of
+`DiscStream` (direct PES pipeline, ISO playback, etc.) without caller
+involvement.
 
 Three primitives compose the disc-side flow:
 
 | Primitive                 | What it does                                                          |
 |---------------------------|-----------------------------------------------------------------------|
-| `Disc::copy`              | disc → ISO. Writes a sidecar `.mapfile`. Opt-in skip-forward on failure. |
-| `Disc::patch`             | Re-reads bad ranges from the drive. Idempotent; call N times.         |
+| `Disc::sweep`             | disc → ISO, one forward pass. Writes a sidecar `.mapfile`. Opt-in skip-on-error. |
+| `Disc::patch`             | Re-reads bad ranges from the drive. One pass per call; caller invokes N times. |
 | `DiscStream` (ISO source) | Reads sectors from the ISO, feeds decrypt → demux → codec → mux.      |
 
 ## Data model
@@ -60,28 +63,46 @@ Status characters match ddrescue:
 
 Position and size are hex byte offsets into the ISO.
 
-### `CopyOptions` and `PatchOptions`
+### `SweepOptions` and `PatchOptions`
 
-`Disc::copy()` auto-detects the pass from mapfile state:
+The library no longer dispatches between sweep and patch internally — the
+caller picks the verb explicitly per pass. The two option structs are flat
+and have no overlap:
 
 ```rust
-CopyOptions {
-    decrypt: true,     // decrypt AACS/CSS sectors
-    multipass: true,   // enable mapfile + skip-on-error + damage-jump
-    progress: Some(&reporter),  // progress callback
-    halt: Some(flag),  // halt flag for graceful stop
+SweepOptions {
+    decrypt: true,
+    resume: false,
+    batch_sectors: None,
+    skip_on_error: true,           // damage-jump + zero-fill on read failure
+    progress: Some(&reporter),
+    halt: Some(flag),
+}
+
+PatchOptions {
+    decrypt: true,
+    block_sectors: None,
+    full_recovery: true,
+    reverse: true,                 // walk bad ranges high → low LBA
+    wedged_threshold: 50,
+    progress: Some(&reporter),
+    halt: Some(flag),
 }
 ```
 
-Dispatch logic:
-- No mapfile → sweep (fresh Pass 1)
-- Mapfile with NonTried (`?`) → sweep with resume
-- Mapfile covering full disc, only NonTrimmed/NonScraped/Unreadable → patch
-- Mapfile clean → no-op
+Caller-orchestrated dispatch (the policy `Disc::copy` used to embed):
+
+- No mapfile → `sweep` (fresh Pass 1).
+- Mapfile with `?` ranges → `sweep` with `resume: true`.
+- Mapfile covers full disc, only `*` / `/` / `-` ranges → `patch`.
+- Mapfile clean → done; no further pass needed.
+
+Each consumer (autorip, `freemkv` CLI) implements the loop in roughly five
+lines of `Mapfile::stats()` checks.
 
 ## Algorithm
 
-### Pass 1 — fast sweep (`Disc::copy` → `sweep_internal`)
+### Pass 1 — fast sweep (`Disc::sweep`)
 
 1. Read one ECC block (32 sectors for UHD, 16 for BD/DVD) at the current LBA.
 2. On success: write data to ISO, mark `+`, advance.
@@ -95,7 +116,7 @@ Dispatch logic:
 
 Pass 1 completes when every byte has been visited (either `+` or `*`).
 
-### Pass 2+ — patch (`Disc::copy` → `patch_internal`)
+### Pass 2+ — patch (`Disc::patch`)
 
 `Disc::patch` reads the mapfile and iterates every non-`+` range. Default: **reverse** mode
 (walks ranges from highest LBA to lowest, within each range from end to start).
@@ -177,4 +198,4 @@ scrape vs. retry with direction reversal) if there's measured benefit.
 
 - [ddrescue manual, Algorithm chapter](https://www.gnu.org/software/ddrescue/manual/ddrescue_manual.html)
 - [ddrescue optical media notes](https://www.electric-spoon.com/doc/gddrescue/html/Optical-media.html)
-- Source: [`src/disc/mapfile.rs`](../src/disc/mapfile.rs), [`src/disc/mod.rs`](../src/disc/mod.rs) (`Disc::copy`, `Disc::patch`), [`src/drive/mod.rs`](../src/drive/mod.rs) (`Drive::read`), [`src/mux/disc.rs`](../src/mux/disc.rs) (`DiscStream::fill_extents`).
+- Source: [`src/disc/mapfile.rs`](../src/disc/mapfile.rs), [`src/disc/sweep.rs`](../src/disc/sweep.rs) (`Disc::sweep`), [`src/disc/patch.rs`](../src/disc/patch.rs) (`Disc::patch`), [`src/drive/mod.rs`](../src/drive/mod.rs) (`Drive::read`), [`src/mux/disc.rs`](../src/mux/disc.rs) (`DiscStream::fill_extents`).

docs/udf.md

@@ -126,7 +126,7 @@ USB optical drives have ~500ms round-trip latency per SCSI command. Since `read_
 
 `Disc::scan()` wraps the drive in a `BufferedSectorReader` before reading. On a single-sector read, the buffer prefetches a batch of sectors (sized from the kernel's `max_hw_sectors_kb` for the device) and caches them. Subsequent reads to nearby LBAs return from cache with zero SCSI overhead. After parsing the UDF directory structure, the entire metadata partition is pre-read into the cache, so all ICB lookups during title scanning and encryption resolution are instant.
 
-The buffer is transparent -- `read_filesystem()`, `read_file()`, and all downstream code still call `read_sectors(lba, 1, buf)` as before. The batching happens inside the `SectorReader` implementation.
+The buffer is transparent -- `read_filesystem()`, `read_file()`, and all downstream code still call `read_sectors(lba, 1, buf)` as before. The batching happens inside the `SectorSource` implementation.
 
 ### UDF Filename Encoding
 

src/aacs/decrypt.rs

@@ -69,16 +69,29 @@ pub(crate) fn aes_cbc_decrypt(key: &[u8; 16], data: &mut [u8]) {
 
 // ── Content decryption ──────────────────────────────────────────────────────
 
-/// Check if a 6144-byte aligned unit is encrypted (copy_permission_indicator bits).
-pub fn is_unit_encrypted(unit: &[u8]) -> bool {
-    unit.len() >= ALIGNED_UNIT_LEN && (unit[0] & 0xC0) != 0
+/// True if a 6144-byte aligned unit is AACS-scrambled on disc.
+///
+/// AACS encrypts the unit body, which destroys the MPEG-TS sync bytes (`0x47`)
+/// a clear unit carries at offsets 4, 196, 388, … (one per 192-byte source
+/// packet). So "scrambled" = "the TS syncs are NOT intact". This is
+/// flag-independent: it does NOT read the TP_extra copy-control bits (byte 0)
+/// or the TS scrambling-control bits (byte 7) — AACS sets neither reliably
+/// across discs/players.
+///
+/// This is the single shared definition of "encrypted" for the whole ecosystem
+/// — libfreemkv's decrypt gate, autorip's sample selection, and the online key
+/// service's validation gate all call THIS, so they always agree on what is
+/// encrypted. A correctly-decrypted (or natively-clear) unit reports `false`,
+/// so the decrypt path never double-decrypts and there is no flag to clear.
+pub fn is_aacs_scrambled(unit: &[u8]) -> bool {
+    unit.len() >= ALIGNED_UNIT_LEN && !ts_syncs_intact(unit)
 }
 
-/// Verify decrypted unit by checking TS sync bytes at expected offsets.
-fn verify_ts(unit: &[u8]) -> bool {
-    // In a 6144-byte unit, TS packets start at byte 0 with 4-byte TP_extra_header
-    // then 188-byte TS packet, repeating every 192 bytes.
-    // Sync byte 0x47 should appear at offset 4, 196, 388, ...
+/// Most TS packet positions in `unit` carry the `0x47` sync byte — i.e. the
+/// unit looks like clear MPEG-TS. Syncs sit at offset 4 and every 192 bytes
+/// after (4-byte TP_extra_header + 188-byte TS packet). An encrypted body
+/// scrambles all but the first (which lives in the clear 16-byte seed).
+fn ts_syncs_intact(unit: &[u8]) -> bool {
     let mut count = 0;
     let mut offset = 4;
     while offset < unit.len() {
@@ -87,11 +100,20 @@ fn verify_ts(unit: &[u8]) -> bool {
         }
         offset += TS_PACKET_LEN;
     }
-    // Expect at least most packets to have sync bytes
-    let total = (unit.len() - 4) / TS_PACKET_LEN + 1;
+    // One sync byte is checked per 192-byte BD-TS packet (at offset 4 of
+    // each). `total` is exactly that packet count; the old
+    // `(len - 4) / TS_PACKET_LEN + 1` over-counted by one for lengths of
+    // the form `4 + k·192` (harmless for the always-6144 aligned unit, but
+    // wrong in general and it biased the majority threshold).
+    let total = unit.len() / TS_PACKET_LEN;
     count > total / 2
 }
 
+/// Verify a decrypted unit looks like clear MPEG-TS (sync bytes intact).
+fn verify_ts(unit: &[u8]) -> bool {
+    ts_syncs_intact(unit)
+}
+
 /// Decrypt one AACS aligned unit (6144 bytes) in-place.
 /// Returns true if decryption succeeded (verified by TS sync bytes).
 ///
@@ -99,12 +121,14 @@ fn verify_ts(unit: &[u8]) -> bool {
 /// 1. AES-128-ECB encrypt first 16 bytes with unit_key → derived
 /// 2. XOR derived with original 16 bytes → unit_decrypt_key
 /// 3. AES-128-CBC decrypt bytes 16..6143 with unit_decrypt_key and AACS IV
-/// 4. Clear encryption flag bits
+///
+/// Decryption restores the TS sync bytes, so the unit reads as clear afterward;
+/// there is no flag to clear.
 pub fn decrypt_unit(unit: &mut [u8], unit_key: &[u8; 16]) -> bool {
     if unit.len() < ALIGNED_UNIT_LEN {
         return false;
     }
-    if !is_unit_encrypted(unit) {
+    if !is_aacs_scrambled(unit) {
         return true; // not encrypted
     }
 
@@ -124,16 +148,13 @@ pub fn decrypt_unit(unit: &mut [u8], unit_key: &[u8; 16]) -> bool {
     // Step 3: Decrypt bytes 16..6143 with AES-CBC
     aes_cbc_decrypt(&decrypt_key, &mut unit[16..ALIGNED_UNIT_LEN]);
 
-    // Step 4: Clear encryption flag
-    unit[0] &= !0xC0;
-
-    // Verify
+    // Decryption restored the TS syncs; verify the unit now looks like clear TS.
     verify_ts(unit)
 }
 
 /// Decrypt one aligned unit trying multiple unit keys. Returns the key index that worked.
 pub fn decrypt_unit_try_keys(unit: &mut [u8], unit_keys: &[[u8; 16]]) -> Option<usize> {
-    if !is_unit_encrypted(unit) {
+    if !is_aacs_scrambled(unit) {
         return Some(0);
     }
 
@@ -173,7 +194,7 @@ pub fn decrypt_unit_full(
     unit_key: &[u8; 16],
     read_data_key: Option<&[u8; 16]>,
 ) -> bool {
-    if !is_unit_encrypted(unit) {
+    if !is_aacs_scrambled(unit) {
         return true;
     }
     if let Some(rdk) = read_data_key {
@@ -200,10 +221,15 @@ mod tests {
 
     #[test]
     fn test_decrypt_unit_unencrypted() {
-        // Unit with 0xC0 bits clear should pass through unchanged
+        // A clear unit (TS syncs intact) is not scrambled → passes through.
         let mut unit = vec![0u8; ALIGNED_UNIT_LEN];
-        unit[0] = 0x00; // not encrypted
+        let mut off = 4;
+        while off < ALIGNED_UNIT_LEN {
+            unit[off] = TS_SYNC;
+            off += TS_PACKET_LEN;
+        }
         let key = [0u8; 16];
+        assert!(!is_aacs_scrambled(&unit));
         assert!(decrypt_unit(&mut unit, &key));
     }
 
@@ -253,8 +279,8 @@ mod tests {
             plain[offset] = TS_SYNC;
             offset += TS_PACKET_LEN;
         }
-        // Set encryption flag
-        plain[0] |= 0xC0;
+        // No flag set: CBC-encrypting the body below scrambles packets 1..31's
+        // TS syncs, which is exactly what `is_aacs_scrambled` (raw-sync) detects.
 
         // Now encrypt bytes 16..6143 using the AACS algorithm (reverse of decrypt)
         let header: [u8; 16] = plain[..16].try_into().unwrap();
@@ -281,9 +307,9 @@ mod tests {
 
         // Now plain contains encrypted data. Decrypt it.
         let mut unit = plain;
-        assert!(is_unit_encrypted(&unit));
+        assert!(is_aacs_scrambled(&unit));
         assert!(decrypt_unit(&mut unit, &unit_key));
-        assert!(!is_unit_encrypted(&unit)); // flag should be cleared
+        assert!(!is_aacs_scrambled(&unit)); // decrypted: TS syncs restored
 
         // Verify TS sync bytes
         let mut count = 0;

src/aacs/handshake.rs

@@ -1235,8 +1235,8 @@ mod tests {
     }
 
     #[test]
-    fn test_aes_cmac() {
-        // Basic CMAC test — at minimum verify it produces consistent output
+    fn test_aes_cmac_deterministic() {
+        // Same (data, key) must always produce the same MAC.
         let key = [
             0x2b, 0x7e, 0x15, 0x16, 0x28, 0xae, 0xd2, 0xa6, 0xab, 0xf7, 0x15, 0x88, 0x09, 0xcf,
             0x4f, 0x3c,
@@ -1248,6 +1248,93 @@ mod tests {
         assert_ne!(mac1, [0u8; 16]); // shouldn't be all zeros
     }
 
+    #[test]
+    fn test_aes_cmac_nist_kat_full_block() {
+        // NIST SP 800-38B Appendix D.1, Example 2 (Mlen = 128):
+        //   K = 2b7e1516 28aed2a6 abf71588 09cf4f3c
+        //   M = 6bc1bee2 2e409f96 e93d7e11 7393172a
+        //   T = 070a16b4 6b4d4144 f79bdd9d d04a287c
+        let key = [
+            0x2b, 0x7e, 0x15, 0x16, 0x28, 0xae, 0xd2, 0xa6, 0xab, 0xf7, 0x15, 0x88, 0x09, 0xcf,
+            0x4f, 0x3c,
+        ];
+        let data = [
+            0x6b, 0xc1, 0xbe, 0xe2, 0x2e, 0x40, 0x9f, 0x96, 0xe9, 0x3d, 0x7e, 0x11, 0x73, 0x93,
+            0x17, 0x2a,
+        ];
+        let expected = [
+            0x07, 0x0a, 0x16, 0xb4, 0x6b, 0x4d, 0x41, 0x44, 0xf7, 0x9b, 0xdd, 0x9d, 0xd0, 0x4a,
+            0x28, 0x7c,
+        ];
+        let mac = aes_cmac_16(&data, &key);
+        assert_eq!(mac, expected, "AES-CMAC-128 must match NIST SP 800-38B KAT");
+    }
+
+    #[test]
+    fn test_vid_mac_verify_roundtrip() {
+        // Simulate the drive-side: pick a (bus_key, vid), compute the MAC, and
+        // verify the host-side check accepts it. Then mutate VID and MAC each
+        // in turn and verify both mutations cause a mismatch (the path that
+        // would yield Error::AacsVidMac in read_volume_id).
+        let bus_key = [
+            0x01, 0x23, 0x45, 0x67, 0x89, 0xab, 0xcd, 0xef, 0xfe, 0xdc, 0xba, 0x98, 0x76, 0x54,
+            0x32, 0x10,
+        ];
+        let vid = [
+            0xde, 0xad, 0xbe, 0xef, 0xca, 0xfe, 0xba, 0xbe, 0x11, 0x22, 0x33, 0x44, 0x55, 0x66,
+            0x77, 0x88,
+        ];
+
+        // Drive returns vid + mac where mac == AES-CMAC-128(bus_key, vid).
+        let drive_mac = aes_cmac_16(&vid, &bus_key);
+        let calc_mac = aes_cmac_16(&vid, &bus_key);
+        assert_eq!(calc_mac, drive_mac, "honest drive: MACs must match");
+
+        // Mutate the MAC: a malicious drive that swapped VID but returned its
+        // original MAC would produce a mismatch here.
+        let mut bad_mac = drive_mac;
+        bad_mac[0] ^= 0x01;
+        assert_ne!(calc_mac, bad_mac, "mutated MAC must be rejected");
+
+        // Mutate the VID: even one bit of VID drift produces a wildly different
+        // CMAC (this is what catches a substituted VID with a stale MAC).
+        let mut bad_vid = vid;
+        bad_vid[15] ^= 0x01;
+        let calc_for_bad_vid = aes_cmac_16(&bad_vid, &bus_key);
+        assert_ne!(
+            calc_for_bad_vid, drive_mac,
+            "MAC over mutated VID must not match original MAC"
+        );
+
+        // Wrong bus key (e.g. handshake replayed against the wrong session)
+        // also produces a different MAC over the same VID.
+        let mut wrong_key = bus_key;
+        wrong_key[0] ^= 0xff;
+        let calc_with_wrong_key = aes_cmac_16(&vid, &wrong_key);
+        assert_ne!(
+            calc_with_wrong_key, drive_mac,
+            "MAC under wrong bus key must not match"
+        );
+    }
+
+    #[test]
+    fn test_vid_mac_all_zero_mac_rejected() {
+        // Defensive: a buggy or hostile drive that returns all-zero MAC must
+        // be rejected (the real MAC over any non-trivial VID is nearly never
+        // 0...0). This guards against a class of "drive returned garbage"
+        // failures masquerading as success.
+        let bus_key = [
+            0x2b, 0x7e, 0x15, 0x16, 0x28, 0xae, 0xd2, 0xa6, 0xab, 0xf7, 0x15, 0x88, 0x09, 0xcf,
+            0x4f, 0x3c,
+        ];
+        let vid = [
+            0x6b, 0xc1, 0xbe, 0xe2, 0x2e, 0x40, 0x9f, 0x96, 0xe9, 0x3d, 0x7e, 0x11, 0x73, 0x93,
+            0x17, 0x2a,
+        ];
+        let calc_mac = aes_cmac_16(&vid, &bus_key);
+        assert_ne!(calc_mac, [0u8; 16], "real CMAC must not be all zeros");
+    }
+
     #[test]
     fn test_verify_host_cert_from_keydb() {
         // Verify the host cert from our KEYDB

src/aacs/keydb.rs

@@ -89,6 +89,17 @@ pub(crate) fn parse_hex20(s: &str) -> Option<[u8; 20]> {
 }
 
 impl KeyDb {
+    /// Construct an empty KeyDb. Used by unit tests; production code
+    /// reaches a populated KeyDb via [`KeyDb::load`] or [`KeyDb::parse`].
+    pub fn empty() -> Self {
+        KeyDb {
+            device_keys: Vec::new(),
+            processing_keys: Vec::new(),
+            host_certs: Vec::new(),
+            disc_entries: HashMap::new(),
+        }
+    }
+
     /// Parse a KEYDB.cfg file from a string.
     pub fn parse(data: &str) -> Self {
         let mut db = KeyDb {
@@ -106,10 +117,19 @@ impl KeyDb {
                 continue;
             }
 
-            // Device Key
+            // Device Key.
+            // Two shapes are accepted:
+            //   1. Positioned DK: `| DK | DEVICE_KEY 0x... | DEVICE_NODE 0x... | KEY_UV 0x... | KEY_U_MASK_SHIFT 0x...`
+            //      → loaded into `device_keys` (deterministic tree walk via `calc_pk_from_dk`).
+            //   2. Orphan DK: `| DK | DEVICE_KEY 0x...` with no position fields.
+            //      → loaded into `processing_keys` (brute walker / terminal validation).
+            // Per AACS spec a "PK" IS a DK at terminal position, so both row types
+            // are DKs in the unified model; only the metadata differs.
             if line.starts_with("| DK") {
                 if let Some(dk) = Self::parse_device_key(line) {
                     db.device_keys.push(dk);
+                } else if let Some(key) = Self::parse_orphan_dk(line) {
+                    db.processing_keys.push(key);
                 }
                 continue;
             }
@@ -152,7 +172,7 @@ impl KeyDb {
         db
     }
 
-    /// Load KEYDB.cfg from a file path.
+    /// Load a KEYDB.cfg from disk.
     pub fn load(path: &std::path::Path) -> std::io::Result<Self> {
         let data = std::fs::read_to_string(path)?;
         Ok(Self::parse(&data))
@@ -184,8 +204,53 @@ impl KeyDb {
             .or_else(|| self.disc_entries.get(&hash))
     }
 
-    // ── Parsers ─────────────────────────────────────────────────────────────
+    /// Iterate every disc entry. Used by Path 3 (scan for matching VID).
+    pub fn iter_disc_entries(&self) -> impl Iterator<Item = &DiscEntry> {
+        self.disc_entries.values()
+    }
+}
 
+// ── KeyProvider impl ──────────────────────────────────────────────────────────
+//
+// Lets `KeyDb` plug into `resolve_keys` via the trait. Cloning happens in the
+// bulk methods because the trait returns owned `Vec`s (so HTTP-backed providers
+// don't need to retain state across calls).
+
+impl super::provider::KeyProvider for KeyDb {
+    fn device_keys(&self) -> Vec<DeviceKey> {
+        self.device_keys.clone()
+    }
+    fn processing_keys(&self) -> Vec<[u8; 16]> {
+        self.processing_keys.clone()
+    }
+    fn media_keys(&self) -> Vec<[u8; 16]> {
+        // Every per-disc Media Key in the db. The resolver dedups; MKs are
+        // MKB-scoped so the same value recurs across a pressing's discs.
+        self.iter_disc_entries()
+            .filter_map(|e| e.media_key)
+            .collect()
+    }
+    fn host_certs(&self) -> Vec<HostCert> {
+        self.host_certs.clone()
+    }
+    fn lookup_disc_by_hash(&self, disc_hash: &[u8; 20]) -> Option<DiscEntry> {
+        let mut hex = String::with_capacity(42);
+        hex.push_str("0x");
+        for b in disc_hash {
+            hex.push_str(&format!("{b:02X}"));
+        }
+        self.find_disc(&hex).cloned()
+    }
+    fn lookup_disc_by_vid(&self, volume_id: &[u8; 16]) -> Option<DiscEntry> {
+        self.iter_disc_entries()
+            .find(|e| matches!(e.disc_id, Some(id) if &id == volume_id))
+            .cloned()
+    }
+}
+
+// ── Private parsers (re-open the inherent impl) ─────────────────────────────
+
+impl KeyDb {
     fn parse_device_key(line: &str) -> Option<DeviceKey> {
         // | DK | DEVICE_KEY 0x... | DEVICE_NODE 0x... | KEY_UV 0x... | KEY_U_MASK_SHIFT 0x...
         let key_str = line.split("DEVICE_KEY").nth(1)?.split('|').next()?.trim();
@@ -218,6 +283,30 @@ impl KeyDb {
         None
     }
 
+    /// Parse an orphan DK row: a `| DK |` line carrying only the
+    /// `DEVICE_KEY` field (no position metadata). The key is then
+    /// treated like a terminal/unpositioned label by the resolver
+    /// (Path 2's brute walker). Returns `None` if the line carries
+    /// any position field — those are positioned DKs and parsed by
+    /// [`Self::parse_device_key`] instead.
+    fn parse_orphan_dk(line: &str) -> Option<[u8; 16]> {
+        if line.contains("DEVICE_NODE")
+            || line.contains("KEY_UV")
+            || line.contains("KEY_U_MASK_SHIFT")
+        {
+            return None;
+        }
+        let key_str = line
+            .split("DEVICE_KEY")
+            .nth(1)?
+            .split('|')
+            .next()?
+            .split(';')
+            .next()?
+            .trim();
+        parse_hex16(key_str)
+    }
+
     fn parse_host_cert(line: &str) -> Option<HostCert> {
         // | HC | HOST_PRIV_KEY 0x... | HOST_CERT 0x...
         let priv_str = line
@@ -366,28 +455,84 @@ mod tests {
 
     #[test]
     fn test_parse_disc_entry() {
-        let line = r#"***REMOVED*** = DUNE_PART_TWO (Dune: Part Two) | D | 2024-04-02 | M | ***REMOVED*** | I | ***REMOVED*** | V | ***REMOVED*** | U | 1-***REMOVED*** ; MKBv77"#;
-        let entry = KeyDb::parse_disc_entry(line).unwrap();
-        assert_eq!(entry.title, "Dune: Part Two");
+        // All-zero placeholders — synthetic; no real key material in code.
+        let z40 = "00".repeat(20);
+        let z32 = "00".repeat(16);
+        let line = format!(
+            "0x{z40} = SAMPLE_FILM (Sample Film) | D | 2024-01-01 | M | 0x{z32} | I | 0x{z32} | V | 0x{z32} | U | 1-0x{z32} ; MKBv77"
+        );
+        let entry = KeyDb::parse_disc_entry(&line).unwrap();
+        assert_eq!(entry.title, "Sample Film");
         assert!(entry.media_key.is_some());
         assert!(entry.vuk.is_some());
         assert_eq!(entry.unit_keys.len(), 1);
         assert_eq!(entry.unit_keys[0].0, 1);
     }
 
+    // NOTE: key fields below use obvious repeated-byte / zero placeholders
+    // (0x01.., 0x02.., 0x03.., 0x00..). NEVER put real — or real-looking — host,
+    // device, or processing key material in code; these tests exercise the
+    // parser's field-splitting only, not any genuine key.
+
     #[test]
     fn test_parse_device_key() {
-        let line = "| DK | DEVICE_KEY ***REMOVED*** | DEVICE_NODE 0x0800 | KEY_UV 0x00000400 | KEY_U_MASK_SHIFT 0x17 ; MKBv01-MKBv48";
+        let line = "| DK | DEVICE_KEY 0x00000000000000000000000000000000 | DEVICE_NODE 0x0800 | KEY_UV 0x00000400 | KEY_U_MASK_SHIFT 0x17 ; MKBv01-MKBv48";
         let dk = KeyDb::parse_device_key(line).unwrap();
         assert_eq!(dk.node, 0x0800);
         assert_eq!(dk.u_mask_shift, 0x17);
     }
 
+    #[test]
+    fn test_orphan_dk_row_loads_into_processing_keys() {
+        // `| DK |` row without position fields = an orphan DK. Per the
+        // unified model the resolver treats it like a terminal/PK
+        // candidate: it lands in `processing_keys` and the brute walker
+        // handles it.
+        let cfg = r#"
+| DK | DEVICE_KEY 0x01010101010101010101010101010101 ; orphan, no position fields
+| DK | DEVICE_KEY 0x02020202020202020202020202020202 | DEVICE_NODE 0x0800 | KEY_UV 0x00000400 | KEY_U_MASK_SHIFT 0x17 ; positioned MKBv01-MKBv48
+| PK | 0x03030303030303030303030303030303 ; legacy PK row still works
+"#;
+        let db = KeyDb::parse(cfg);
+        assert_eq!(
+            db.device_keys.len(),
+            1,
+            "positioned DK row should land in device_keys"
+        );
+        // Orphan DK + legacy PK row both end up in processing_keys.
+        assert_eq!(
+            db.processing_keys.len(),
+            2,
+            "orphan DK row + legacy PK row both belong in processing_keys"
+        );
+        assert_eq!(db.processing_keys[0][..4], [0x01, 0x01, 0x01, 0x01]);
+        assert_eq!(db.processing_keys[1][..4], [0x03, 0x03, 0x03, 0x03]);
+    }
+
+    #[test]
+    fn test_parse_orphan_dk_rejects_lines_with_position_fields() {
+        // The parser must NOT pick up a positioned DK row as an orphan
+        // (that would double-count). parse_orphan_dk explicitly checks.
+        let positioned = "| DK | DEVICE_KEY 0x02020202020202020202020202020202 | DEVICE_NODE 0x0800 | KEY_UV 0x00000400 | KEY_U_MASK_SHIFT 0x17";
+        assert!(
+            KeyDb::parse_orphan_dk(positioned).is_none(),
+            "positioned DK must not match orphan parser"
+        );
+        let orphan = "| DK | DEVICE_KEY 0x01010101010101010101010101010101";
+        let key = KeyDb::parse_orphan_dk(orphan).expect("orphan should parse");
+        assert_eq!(key[..4], [0x01, 0x01, 0x01, 0x01]);
+    }
+
     #[test]
     fn test_parse_host_cert() {
-        let line = "| HC | HOST_PRIV_KEY ***REMOVED*** | HOST_CERT ***REMOVED*** ; Revoked";
-        let hc = KeyDb::parse_host_cert(line).unwrap();
-        assert_eq!(hc.private_key[0], 0x90);
+        // 20-byte priv + 92-byte cert, all zeros — placeholders, not a key.
+        let line = format!(
+            "| HC | HOST_PRIV_KEY 0x{} | HOST_CERT 0x{} ; Revoked",
+            "00".repeat(20),
+            "00".repeat(92)
+        );
+        let hc = KeyDb::parse_host_cert(&line).unwrap();
+        assert_eq!(hc.private_key, [0u8; 20]);
         assert_eq!(hc.certificate.len(), 92);
     }
 
@@ -405,15 +550,15 @@ mod tests {
         assert!(!db.host_certs.is_empty());
         assert!(db.disc_entries.len() > 170000);
 
-        // Look up Dune: Part Two
-        let dune = db
+        // Look up any disc entry carrying a full key set.
+        let entry = db
             .disc_entries
             .values()
-            .find(|e| e.title.contains("Dune: Part Two") && e.vuk.is_some())
-            .expect("Dune: Part Two not found");
-        assert!(dune.media_key.is_some());
-        assert!(dune.vuk.is_some());
-        assert!(!dune.unit_keys.is_empty());
+            .find(|e| e.vuk.is_some() && e.media_key.is_some() && !e.unit_keys.is_empty())
+            .expect("no disc entry with a full key set");
+        assert!(entry.media_key.is_some());
+        assert!(entry.vuk.is_some());
+        assert!(!entry.unit_keys.is_empty());
 
         eprintln!(
             "Parsed {} disc entries, {} DK, {} PK",

src/aacs/mod.rs

@@ -17,16 +17,26 @@ pub mod decrypt;
 pub mod handshake;
 pub mod keydb;
 pub mod keys;
+pub mod provider;
+pub mod variants;
 
 // 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, decrypt_bus, decrypt_unit, decrypt_unit_full, decrypt_unit_try_keys,
-    is_unit_encrypted,
+    is_aacs_scrambled,
 };
 pub use keydb::{DeviceKey, DiscEntry, HostCert, KeyDb};
+pub use keys::probe;
 pub use keys::{
-    ContentCert, ResolvedKeys, UnitKeyFile, decrypt_unit_key, derive_media_key_from_dk,
-    derive_media_key_from_pk, derive_vuk, disc_hash, disc_hash_hex, mkb_version,
-    parse_content_cert, parse_unit_key_ro, read_mkb_from_drive, resolve_keys,
+    AacsVersion, ContentCert, ResolveContext, ResolvedKeys, UnitKeyFile, decrypt_unit_key,
+    derive_media_key_from_dk, derive_media_key_from_pk, derive_vuk, disc_hash, disc_hash_hex,
+    mkb_content_len, mkb_version, parse_content_cert, parse_unit_key_ro, read_mkb_from_drive,
+    resolve_keys_v1, resolve_keys_v2, resolve_keys_v21,
+};
+pub use provider::KeyProvider;
+pub use variants::{
+    KEY_CORRECTION_DATA_PLACEHOLDER, MediaKeyVariantError, MkbRecord, ProcessingKeyMatch,
+    derive_media_key_variant, is_variant_mkb, variant_data_record, variant_key_data, variant_nonce,
+    walk_mkb, walk_processing_key,
 };

src/aacs/provider.rs

@@ -0,0 +1,161 @@
+//! Key source abstraction for the AACS resolve chain.
+//!
+//! libfreemkv keeps all crypto (AES-G primitives, SD-tree walking,
+//! validation, MK/VUK/TK derivation) but accepts key material from
+//! arbitrary backends via [`KeyProvider`].
+//!
+//! Methods come in two flavors:
+//!
+//! - **Bulk material** ([`device_keys`], [`processing_keys`],
+//!   [`host_certs`]) — the resolver unions results across all
+//!   providers and tries each candidate.
+//! - **Disc-keyed lookup** ([`lookup_disc_by_hash`],
+//!   [`lookup_disc_by_vid`]) — the resolver short-circuits on the
+//!   first hit, so providers are queried in array order with
+//!   fastest/closest first.
+//!
+//! Default impls return empty / `None` so backends only override
+//! the methods they actually support — an external key service might
+//! implement only `lookup_disc_by_hash`, while a local file might
+//! implement all five.
+//!
+//! Calls may block (disk I/O, network round-trips). The resolver
+//! invokes each method at most a handful of times per scan; for
+//! per-disc memoization, implementations should cache internally.
+//!
+//! [`device_keys`]: KeyProvider::device_keys
+//! [`processing_keys`]: KeyProvider::processing_keys
+//! [`host_certs`]: KeyProvider::host_certs
+//! [`lookup_disc_by_hash`]: KeyProvider::lookup_disc_by_hash
+//! [`lookup_disc_by_vid`]: KeyProvider::lookup_disc_by_vid
+
+use super::keydb::{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,
+/// MK→VUK→TK derivation). See module docs for method semantics.
+pub trait KeyProvider: Send + Sync {
+    /// Device keys (top-of-tree, walked by the resolver).
+    fn device_keys(&self) -> Vec<DeviceKey> {
+        Vec::new()
+    }
+
+    /// Processing keys — terminal PKs or walk-input PKs. The
+    /// resolver tries each as a terminal first (cheap validate).
+    fn processing_keys(&self) -> Vec<[u8; 16]> {
+        Vec::new()
+    }
+
+    /// Every Media Key this provider holds, regardless of which disc it was
+    /// filed under. An MK is MKB-scoped (shared across a pressing/MKB-family),
+    /// so the resolver can verify each against the disc's MKB (`km_verifies`)
+    /// and resolve a disc whose own hash/VID isn't directly keyed.
+    fn media_keys(&self) -> Vec<[u8; 16]> {
+        Vec::new()
+    }
+
+    /// AACS host certificates (with their private keys) for drive
+    /// authentication. Multiple in case some are revoked.
+    fn host_certs(&self) -> Vec<HostCert> {
+        Vec::new()
+    }
+
+    /// Direct per-disc lookup by SHA-1 of `Unit_Key_RO.inf`. Returns
+    /// `Some(entry)` if this provider has pre-computed material for
+    /// the disc (paths 4 and 5). Short-circuits the resolver.
+    fn lookup_disc_by_hash(&self, _disc_hash: &[u8; 20]) -> Option<DiscEntry> {
+        None
+    }
+
+    /// Lookup by Volume ID (path 3 — pre-computed MK + matching
+    /// VID). Short-circuits the resolver on hit.
+    fn lookup_disc_by_vid(&self, _volume_id: &[u8; 16]) -> Option<DiscEntry> {
+        None
+    }
+}
+
+/// Resolver-side helpers that aggregate across a provider array.
+///
+/// The resolver consumes `&[&dyn KeyProvider]` directly; these
+/// helpers wrap the union-vs-short-circuit policy per method.
+pub(crate) struct Providers<'a>(pub &'a [&'a dyn KeyProvider]);
+
+impl Providers<'_> {
+    /// Union — gather DKs from every provider.
+    pub fn device_keys(&self) -> Vec<DeviceKey> {
+        self.0.iter().flat_map(|p| p.device_keys()).collect()
+    }
+
+    /// Union — gather PKs from every provider.
+    pub fn processing_keys(&self) -> Vec<[u8; 16]> {
+        self.0.iter().flat_map(|p| p.processing_keys()).collect()
+    }
+
+    /// Union of distinct Media Keys across every provider, for the MK-pool
+    /// brute (`km_verifies` against the disc's MKB).
+    pub fn media_keys(&self) -> Vec<[u8; 16]> {
+        let mut v: Vec<[u8; 16]> = self.0.iter().flat_map(|p| p.media_keys()).collect();
+        v.sort_unstable();
+        v.dedup();
+        v
+    }
+
+    /// Union — gather host certs from every provider. Not yet wired into
+    /// the SCSI handshake (which still reads `KeyDb.host_certs` directly);
+    /// kept here so a provider-aware handshake refactor is a drop-in.
+    #[allow(dead_code)]
+    pub fn host_certs(&self) -> Vec<HostCert> {
+        self.0.iter().flat_map(|p| p.host_certs()).collect()
+    }
+
+    /// Short-circuit — query providers in array order, first hit wins.
+    pub fn lookup_disc_by_hash(&self, disc_hash: &[u8; 20]) -> Option<DiscEntry> {
+        self.0.iter().find_map(|p| p.lookup_disc_by_hash(disc_hash))
+    }
+
+    /// Short-circuit — query providers in array order, first hit wins.
+    pub fn lookup_disc_by_vid(&self, volume_id: &[u8; 16]) -> Option<DiscEntry> {
+        self.0.iter().find_map(|p| p.lookup_disc_by_vid(volume_id))
+    }
+}
+
+/// A [`KeyProvider`] backed by a single caller-supplied key's raw material —
+/// the bridge for [`crate::disc::Disc::decrypt_with`].
+///
+/// The application's key source did the lookup and handed in material at one
+/// level (DK / PK / MK / VUK). This exposes exactly that material to the
+/// version-dispatched resolver, which owns ALL derivation — so a source never
+/// derives, and the lib remains the single home for the AACS chain across
+/// 1.0 / 2.0 / 2.1 / 2.x.
+///
+/// Each level fills only its own field; the rest stay empty, so the resolver
+/// naturally runs the matching path (DK→…, PK→…, MK-pool brute, or a
+/// disc-keyed VUK hit). `decrypt_with` already knows the disc, so the
+/// `lookup_disc_by_*` hash/VID arguments are irrelevant — a present
+/// `disc_entry` is returned for any query.
+pub(crate) struct SuppliedKey {
+    pub device_keys: Vec<DeviceKey>,
+    pub processing_keys: Vec<[u8; 16]>,
+    pub media_keys: Vec<[u8; 16]>,
+    pub disc_entry: Option<DiscEntry>,
+}
+
+impl KeyProvider for SuppliedKey {
+    fn device_keys(&self) -> Vec<DeviceKey> {
+        self.device_keys.clone()
+    }
+    fn processing_keys(&self) -> Vec<[u8; 16]> {
+        self.processing_keys.clone()
+    }
+    fn media_keys(&self) -> Vec<[u8; 16]> {
+        self.media_keys.clone()
+    }
+    fn lookup_disc_by_hash(&self, _disc_hash: &[u8; 20]) -> Option<DiscEntry> {
+        self.disc_entry.clone()
+    }
+    fn lookup_disc_by_vid(&self, _volume_id: &[u8; 16]) -> Option<DiscEntry> {
+        self.disc_entry.clone()
+    }
+}

src/aacs/variants.rs

@@ -0,0 +1,679 @@
+//! AACS Media Key Variant chain.
+//!
+//! 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.
+//!
+//! 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 new MKB record types `0x82` (Encrypted Media Key
+//! Variant Data + Variant Key Data) and `0x83` (Variant Number). When
+//! a disc carries neither, callers should fall back to the classical
+//! single-stage derivation in [`super::keys`].
+//!
+//! The chain follows the published spec:
+//!
+//! ```text
+//! Kmp     = AES-128D(Kp, C) XOR uv
+//! Kpnew   = Kmp XOR KCD
+//! Kvn     = AES-G(Kp, Nonce) & 0xFFFF   (low 16 bits, BE)
+//! VKD_idx = Kvn XOR VARIANTS[uv]
+//! VKD     = vkd_table[VKD_idx * 16 .. +16]
+//! 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.
+
+use super::decrypt::aes_ecb_decrypt;
+use super::keydb::DeviceKey;
+
+// ── Public constants ──────────────────────────────────────────────────────
+
+/// Placeholder Key Correction Data. Sixteen zero bytes.
+///
+/// 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];
+
+// ── 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> {
+    let mut out = Vec::new();
+    let mut pos = 0;
+    while pos + 4 <= mkb.len() {
+        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 {
+            break;
+        }
+        if rec_len < 4 || pos + rec_len > mkb.len() {
+            break;
+        }
+        let body = mkb[pos + 4..pos + rec_len].to_vec();
+        out.push(MkbRecord {
+            offset: pos,
+            rec_type,
+            rec_len,
+            body,
+        });
+        pos += rec_len;
+    }
+    out
+}
+
+/// True iff `records` contains at least one Media Key Variant record
+/// (type `0x82` or `0x83`).
+pub fn is_variant_mkb(records: &[MkbRecord]) -> bool {
+    records.iter().any(|r| matches!(r.rec_type, 0x82 | 0x83))
+}
+
+/// Body of the Encrypted Media Key Variant Data record (type `0x82`).
+pub fn variant_data_record(records: &[MkbRecord]) -> Option<&[u8]> {
+    records
+        .iter()
+        .find(|r| r.rec_type == 0x82)
+        .map(|r| r.body.as_slice())
+}
+
+/// 16-byte Nonce from the Variant Number record (type `0x83`). Returns
+/// the first 16 bytes of the body.
+pub fn variant_nonce(records: &[MkbRecord]) -> Option<[u8; 16]> {
+    let r = records.iter().find(|r| r.rec_type == 0x83)?;
+    if r.body.len() < 16 {
+        return None;
+    }
+    let mut out = [0u8; 16];
+    out.copy_from_slice(&r.body[..16]);
+    Some(out)
+}
+
+/// Body of the Variant Key Data record. Returns the first `0x82` body
+/// that is a non-empty multiple of 16 bytes.
+pub fn variant_key_data(records: &[MkbRecord]) -> Option<&[u8]> {
+    records
+        .iter()
+        .find(|r| r.rec_type == 0x82 && !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) ──────────────────────────
+
+/// AES-G3 seed register initial value.
+const AESG3_SEED: [u8; 16] = [
+    0x7B, 0x10, 0x3C, 0x5D, 0xCB, 0x08, 0xC4, 0xE5, 0x1A, 0x27, 0xB0, 0x17, 0x99, 0x05, 0x3B, 0xD9,
+];
+
+/// AES-G3 single step: AES-G against the seed register at offset `inc`.
+fn aesg3_step(key: &[u8; 16], inc: u8) -> [u8; 16] {
+    let mut seed = AESG3_SEED;
+    seed[15] = seed[15].wrapping_add(inc);
+    aes_g(key, &seed)
+}
+
+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
+}
+
+fn calc_pk_from_dk(dk: &[u8; 16], uv: u32, v_mask: u32, dev_key_v_mask: u32) -> [u8; 16] {
+    let mut left_child = aesg3_step(dk, 0);
+    let mut pk = aesg3_step(dk, 1);
+    let mut right_child = aesg3_step(dk, 2);
+    let mut current_v_mask = dev_key_v_mask;
+
+    while current_v_mask != 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 curr_key = if bit_pos < 0 || (uv & (1u32 << bit_pos as u32)) == 0 {
+            left_child
+        } else {
+            right_child
+        };
+
+        left_child = aesg3_step(&curr_key, 0);
+        pk = aesg3_step(&curr_key, 1);
+        right_child = aesg3_step(&curr_key, 2);
+
+        current_v_mask = ((current_v_mask as i32) >> 1) as u32;
+    }
+
+    pk
+}
+
+/// Outcome of a subset-difference walk against an MKB. Carries the
+/// processing key and the matching `uv` slot — both needed as inputs
+/// to the variant chain.
+#[derive(Debug, Clone, Copy)]
+pub struct ProcessingKeyMatch {
+    /// Processing Key.
+    pub kp: [u8; 16],
+    /// Subset-difference node number that matched.
+    pub uv: u32,
+    /// 16-byte cvalue that the matched uv selected.
+    pub cvalue: [u8; 16],
+    /// Index of the matching cvalue within the cvalues record.
+    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 mut out = [0u8; 16];
+    out.copy_from_slice(&r.body[..16]);
+    Some(out)
+}
+
+/// Walk an MKB and return the first `(Kp, uv, cvalue)` that
+/// `device_keys` covers. Returns `None` if no DK walks any uv.
+pub fn walk_processing_key(
+    records: &[MkbRecord],
+    device_keys: &[DeviceKey],
+) -> Option<ProcessingKeyMatch> {
+    let mk_dv = mkb_find_mk_dv(records)?;
+    let uvs = mkb_find_body(records, 0x04)?;
+    let cvalues = mkb_find_body(records, 0x07).or_else(|| mkb_find_body(records, 0x05))?;
+
+    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;
+
+        for uvs_idx in 0..num_uvs {
+            let p_uv = &uvs[1 + 5 * uvs_idx..];
+            let u_mask_shift = uvs[5 * uvs_idx];
+
+            if u_mask_shift & 0xC0 != 0 {
+                break;
+            }
+
+            let uv = u32::from_be_bytes([p_uv[0], p_uv[1], p_uv[2], p_uv[3]]);
+            if uv == 0 {
+                continue;
+            }
+
+            let u_mask: u32 = 0xFFFF_FFFFu32.wrapping_shl(u_mask_shift as u32);
+            let v_mask = calc_v_mask(uv);
+
+            if ((device_number & u_mask) == (uv & u_mask))
+                && ((device_number & v_mask) != (uv & v_mask))
+            {
+                let dev_key_v_mask = calc_v_mask(dk.uv);
+                let dev_key_u_mask: u32 = 0xFFFF_FFFFu32.wrapping_shl(dk.u_mask_shift as u32);
+
+                if u_mask == dev_key_u_mask && (uv & dev_key_v_mask) == (dk.uv & dev_key_v_mask) {
+                    let pk = calc_pk_from_dk(&dk.key, uv, v_mask, dev_key_v_mask);
+
+                    if uvs_idx >= cvalues.len() / 16 {
+                        continue;
+                    }
+                    let mut cv = [0u8; 16];
+                    cv.copy_from_slice(&cvalues[uvs_idx * 16..(uvs_idx + 1) * 16]);
+
+                    // Validate: AES-D(Kp, cv), XOR uv into low 4 bytes,
+                    // then AES-D(.., mk_dv) must reveal the verify magic.
+                    let mut km_candidate = aes_ecb_decrypt(&pk, &cv);
+                    let uv_bytes = uv.to_be_bytes();
+                    for i in 0..4 {
+                        km_candidate[12 + i] ^= uv_bytes[i];
+                    }
+                    let dec_vd = aes_ecb_decrypt(&km_candidate, &mk_dv);
+                    const VERIFY_MAGIC: [u8; 8] = [0x01, 0x23, 0x45, 0x67, 0x89, 0xAB, 0xCD, 0xEF];
+                    // On a classical (non-variant) MKB this magic must
+                    // match. On a variant MKB it won't — `km_candidate`
+                    // is really Kmp and the magic check is moot. We
+                    // still gate the walk on cvalue indexing being
+                    // sane; the chain itself enforces the variant
+                    // semantics downstream.
+                    let classical_ok = dec_vd[..8] == VERIFY_MAGIC;
+                    let variant_present = is_variant_mkb(records);
+                    if !(classical_ok || variant_present) {
+                        continue;
+                    }
+
+                    return Some(ProcessingKeyMatch {
+                        kp: pk,
+                        uv,
+                        cvalue: cv,
+                        cvalue_index: uvs_idx,
+                    });
+                }
+            }
+        }
+    }
+    None
+}
+
+// ── Error reporting ───────────────────────────────────────────────────────
+
+/// Outcome of [`derive_media_key_variant`] when the chain cannot
+/// produce a Media Key. Every variant is a classification only — no
+/// strings, no Display impl beyond the error code.
+#[derive(Debug, PartialEq, Eq, Clone, Copy)]
+pub enum MediaKeyVariantError {
+    /// MKB carries no Variant records. Caller should fall back to the
+    /// classical single-stage derivation.
+    NotVariantMkb,
+    /// MKB is missing a required record (mk_dv, subset-difference,
+    /// cvalues, variant data, or variant nonce).
+    MkbIncomplete,
+    /// `device_keys` did not cover any uv slot in this MKB.
+    ProcessingKeyUnavailable,
+    /// `Kmp[15]` carries bit `0x02`: the soft-correction path applies
+    /// for this Precursor. Out of scope for the hardcoded-KCD chain.
+    SoftCorrectionRequired,
+    /// `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.
+    VariantsTableUnavailable,
+    /// VKD index resolved out of the supplied `vkd_table`.
+    VkdIndexOutOfRange,
+}
+
+impl std::fmt::Display for MediaKeyVariantError {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        let code: u16 = match self {
+            MediaKeyVariantError::NotVariantMkb => 7100,
+            MediaKeyVariantError::MkbIncomplete => 7101,
+            MediaKeyVariantError::ProcessingKeyUnavailable => 7102,
+            MediaKeyVariantError::SoftCorrectionRequired => 7103,
+            MediaKeyVariantError::OnlineChallengeRequired => 7104,
+            MediaKeyVariantError::KcdNotProvided => 7105,
+            MediaKeyVariantError::VariantsTableUnavailable => 7106,
+            MediaKeyVariantError::VkdIndexOutOfRange => 7107,
+        };
+        write!(f, "E{code}")
+    }
+}
+
+impl std::error::Error for MediaKeyVariantError {}
+
+// ── Chain ─────────────────────────────────────────────────────────────────
+
+/// Look up `VARIANTS[uv]` for the matched uv. The byte layout of the
+/// per-uv slot in the Variant Number record is undocumented and is
+/// disc-specific; this helper returns `None` until a Variant disc is
+/// available to fix the layout against.
+fn variants_for_uv(_records: &[MkbRecord], _uv_index: usize) -> Option<u16> {
+    None
+}
+
+/// 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.
+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);
+    }
+
+    let pkm = walk_processing_key(mkb_records, device_keys)
+        .ok_or(MediaKeyVariantError::ProcessingKeyUnavailable)?;
+
+    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);
+    }
+    let mut c_block = [0u8; 16];
+    c_block.copy_from_slice(&c_value[..16]);
+
+    // 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();
+    for i in 0..4 {
+        kmp[12 + i] ^= uv_bytes[i];
+    }
+
+    // Condition bits on Kmp[15] route off the hardcoded-KCD path.
+    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];
+    }
+
+    // Step: Kvn = AES-G(Kp, Nonce) & 0xFFFF  (low 16 bits, BE).
+    let kvn_block = aes_g(&pkm.kp, &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)
+        .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() {
+        return Err(MediaKeyVariantError::VkdIndexOutOfRange);
+    }
+    let mut vkd = [0u8; 16];
+    vkd.copy_from_slice(&vkd_table[off..off + 16]);
+
+    // Step: Km = AES-128D(Kpnew, VKD) XOR uv.
+    let mut km = aes_ecb_decrypt(&kpnew, &vkd);
+    for i in 0..4 {
+        km[12 + i] ^= uv_bytes[i];
+    }
+
+    // Step: Kvu = AES-G(Km, VID).
+    let kvu = aes_g(&km, vid);
+
+    Ok((km, kvu))
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    // ── Helpers ──
+
+    fn synthetic_mkb_classical() -> Vec<u8> {
+        // Minimal MKB: type/version record + cvalues + mk_dv. No variant
+        // records.
+        let mut mkb = vec![
+            0x10, 0x00, 0x00, 0x0C, 0x48, 0x14, 0x10, 0x03, 0x00, 0x00, 0x00, 0x4D,
+        ];
+        mkb.extend_from_slice(&[0x07, 0x00, 0x00, 0x14]);
+        mkb.extend_from_slice(&[0xAB; 16]);
+        mkb.extend_from_slice(&[0x86, 0x00, 0x00, 0x14]);
+        mkb.extend_from_slice(&[0xCD; 16]);
+        mkb
+    }
+
+    fn synthetic_mkb_with_variant() -> Vec<u8> {
+        let mut mkb = synthetic_mkb_classical();
+        // 0x82 — 16-byte body (Variant data / VKD slot).
+        mkb.extend_from_slice(&[0x82, 0x00, 0x00, 0x14]);
+        mkb.extend_from_slice(&[0xEE; 16]);
+        // 0x83 — 16-byte body (Variant Nonce).
+        mkb.extend_from_slice(&[0x83, 0x00, 0x00, 0x14]);
+        mkb.extend_from_slice(&[0x55; 16]);
+        mkb
+    }
+
+    // ── Walker / record detection ──
+
+    #[test]
+    fn walker_parses_synthetic_mkb() {
+        let mkb = synthetic_mkb_classical();
+        let recs = walk_mkb(&mkb);
+        assert_eq!(recs.len(), 3);
+        assert_eq!(recs[0].rec_type, 0x10);
+        assert_eq!(recs[1].rec_type, 0x07);
+        assert_eq!(recs[2].rec_type, 0x86);
+    }
+
+    #[test]
+    fn variant_detection_negative_on_classical() {
+        let recs = walk_mkb(&synthetic_mkb_classical());
+        assert!(!is_variant_mkb(&recs));
+        assert!(variant_nonce(&recs).is_none());
+        assert!(variant_key_data(&recs).is_none());
+        assert!(variant_data_record(&recs).is_none());
+    }
+
+    #[test]
+    fn variant_detection_positive_on_variant() {
+        let recs = walk_mkb(&synthetic_mkb_with_variant());
+        assert!(is_variant_mkb(&recs));
+        assert_eq!(variant_nonce(&recs), Some([0x55; 16]));
+        assert_eq!(variant_key_data(&recs), Some(&[0xEE; 16][..]));
+        assert_eq!(variant_data_record(&recs), Some(&[0xEE; 16][..]));
+    }
+
+    // ── Chain entry-point classification ──
+
+    #[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])
+            .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])
+            .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])
+            .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);
+    }
+
+    #[test]
+    fn error_display_is_code_only() {
+        // No English in Display — every variant emits "E7xxx" and
+        // nothing else.
+        let cases = [
+            MediaKeyVariantError::NotVariantMkb,
+            MediaKeyVariantError::MkbIncomplete,
+            MediaKeyVariantError::ProcessingKeyUnavailable,
+            MediaKeyVariantError::SoftCorrectionRequired,
+            MediaKeyVariantError::OnlineChallengeRequired,
+            MediaKeyVariantError::KcdNotProvided,
+            MediaKeyVariantError::VariantsTableUnavailable,
+            MediaKeyVariantError::VkdIndexOutOfRange,
+        ];
+        for e in cases {
+            let s = e.to_string();
+            assert!(
+                s.starts_with('E') && s.len() == 5,
+                "error display must be E#### only, got {s:?}"
+            );
+            assert!(
+                s.chars().skip(1).all(|c| c.is_ascii_digit()),
+                "error display must be E + digits, got {s:?}"
+            );
+        }
+    }
+
+    // ── Fixture construction ──
+
+    /// Build a synthetic variant MKB plus a DK that walks the single
+    /// subset-difference slot it carries. `kmp15` is the value of the
+    /// low byte of `Kmp[15]` that the chain will land on — pick `0x02`
+    /// to exercise the SoftCorrection bit, `0x04` to exercise
+    /// OnlineChallenge, `0x00` otherwise.
+    ///
+    /// The fixture pins:
+    /// - MKB subset-difference: `u_mask_shift=3, uv=2`. With these
+    ///   masks the discriminator bit (u_mask=1, v_mask=0) is bit 2.
+    /// - one DK at `node=4, uv=2, u_mask_shift=3`. node 4 has bit 2 set
+    ///   (differs from uv=2 on bit 2 → disagrees on v_mask) while
+    ///   agreeing with uv on bits 3+ (the u_mask=1 region). dk.uv ==
+    ///   MKB.uv and dk.u_mask_shift == MKB.u_mask_shift make
+    ///   `dev_key_v_mask == v_mask`, so `calc_pk_from_dk` loops zero
+    ///   times — Kp = aesg3_step(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.
+    ///
+    /// 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;
+
+        // Build header.
+        let mut mkb = vec![
+            0x10, 0x00, 0x00, 0x0C, 0x48, 0x14, 0x10, 0x03, 0x00, 0x00, 0x00, 0x4D,
+        ];
+
+        // Subset-difference (0x04): u_mask_shift=3, uv=00 00 00 02.
+        mkb.extend_from_slice(&[0x04, 0x00, 0x00, 0x09]);
+        mkb.extend_from_slice(&[0x03, 0x00, 0x00, 0x00, 0x02]);
+
+        // Pick a known DK; with dk.uv == MKB.uv (==2) and
+        // dk.u_mask_shift == MKB.u_mask_shift (==1), dev_key_v_mask
+        // equals the MKB's v_mask and the calc_pk_from_dk loop is a
+        // no-op — Kp = aesg3_step(dk, 1).
+        let dk_bytes: [u8; 16] = [
+            0x11, 0x22, 0x33, 0x44, 0x55, 0x66, 0x77, 0x88, 0x99, 0xAA, 0xBB, 0xCC, 0xDD, 0xEE,
+            0xFF, 0x00,
+        ];
+        let kp = aesg3_step(&dk_bytes, 1);
+
+        // Plant Kmp with chosen byte-15, then compute C such that
+        // AES-D(Kp, C) ⊕ uv == Kmp. uv=2 → low-4 bytes XOR is 00 00 00 02.
+        let mut kmp = [0x42u8; 16];
+        kmp[15] = kmp15;
+        let mut aes_d_result = kmp;
+        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.
+        mkb.extend_from_slice(&[0x07, 0x00, 0x00, 0x14]);
+        mkb.extend_from_slice(&[0xAB; 16]);
+
+        // Verify Media Key (0x86): body content is don't-care.
+        mkb.extend_from_slice(&[0x86, 0x00, 0x00, 0x14]);
+        mkb.extend_from_slice(&[0xCD; 16]);
+
+        // 0x82 record: holds C (Encrypted Media Key Variant Data) AND
+        // doubles as the VKD table (single 16-byte entry → VKDidx must
+        // resolve to 0 for `chain_surfaces_variants_table_gap` test —
+        // but the test never reaches the VKD lookup since the
+        // VARIANTS[uv] helper is not yet wired).
+        mkb.extend_from_slice(&[0x82, 0x00, 0x00, 0x14]);
+        mkb.extend_from_slice(&c_block);
+
+        // 0x83 record: 16-byte Nonce.
+        mkb.extend_from_slice(&[0x83, 0x00, 0x00, 0x14]);
+        mkb.extend_from_slice(&[0x77; 16]);
+
+        let recs = walk_mkb(&mkb);
+
+        let dk = DeviceKey {
+            key: dk_bytes,
+            node: 4,
+            uv: 2,
+            u_mask_shift: 3,
+        };
+        (recs, dk, kp, kmp)
+    }
+}

src/clpi.rs

@@ -20,6 +20,35 @@ pub struct ClipInfo {
     pub ep_coarse: Vec<EpCoarse>,
     /// Fine EP entries for the primary video stream
     pub ep_fine: Vec<EpFine>,
+    /// Per-stream metadata from the ProgramInfo section (BD spec).
+    /// Cross-validates the MPLS STN view — see `labels/clpi.rs`.
+    /// Empty when program_info is missing or malformed.
+    pub streams: Vec<ClpiStream>,
+}
+
+/// One stream descriptor from the CLPI ProgramInfo / stream_coding_info
+/// table. Mirrors the same fields the MPLS STN table carries — see
+/// `mpls::StreamEntry` for the playlist-side equivalent.
+#[derive(Debug, Clone)]
+#[allow(dead_code)]
+pub struct ClpiStream {
+    /// PID of the stream in the MPEG-TS (matches MPLS).
+    pub pid: u16,
+    /// SCSI/BD coding type byte (0x80 LPCM, 0x83 TrueHD, 0x86 DTS-HD MA,
+    /// 0x90 PG, etc.). See `labels::mpls_universal::coding_type_to_codec_hint`.
+    pub coding_type: u8,
+    /// ISO 639-2 3-char language code. Empty for video streams.
+    pub language: String,
+    /// Audio format byte (1=mono, 3=stereo, 6=5.1, 12=7.1).
+    /// Zero for non-audio streams.
+    pub audio_format: u8,
+    /// Audio sample rate (1=48kHz, 4=96kHz, 5=192kHz). Zero for non-audio.
+    pub audio_rate: u8,
+    /// Video format byte (1=480i, 4=1080i, 5=720p, 6=1080p, 8=2160p).
+    /// Zero for non-video.
+    pub video_format: u8,
+    /// Video rate (1=23.976, 2=24, 3=25, 4=29.97, 6=50, 7=59.94).
+    pub video_rate: u8,
 }
 
 #[derive(Debug, Clone)]
@@ -128,7 +157,7 @@ pub fn parse(data: &[u8]) -> Result<ClipInfo> {
 
     // Header offsets
     let _seq_info_start = u32::from_be_bytes([data[8], data[9], data[10], data[11]]) as usize;
-    let _prog_info_start = u32::from_be_bytes([data[12], data[13], data[14], data[15]]) as usize;
+    let prog_info_start = u32::from_be_bytes([data[12], data[13], data[14], data[15]]) as usize;
     let cpi_start = u32::from_be_bytes([data[16], data[17], data[18], data[19]]) as usize;
 
     // ClipInfo section at offset 40
@@ -139,6 +168,16 @@ pub fn parse(data: &[u8]) -> Result<ClipInfo> {
         0
     };
 
+    // Parse ProgramInfo (per-stream language + codec). Best-effort:
+    // malformed program_info doesn't fail the parse, just gives an
+    // empty streams list. EP map is unaffected — sector-range lookups
+    // continue to work.
+    let streams = if prog_info_start > 0 && prog_info_start + 6 < data.len() {
+        parse_program_info(&data[prog_info_start..])
+    } else {
+        Vec::new()
+    };
+
     // Parse CPI / EP Map
     let (ep_coarse, ep_fine) = if cpi_start > 0 && cpi_start + 8 < data.len() {
         parse_cpi(&data[cpi_start..])?
@@ -151,9 +190,127 @@ pub fn parse(data: &[u8]) -> Result<ClipInfo> {
         source_packet_count,
         ep_coarse,
         ep_fine,
+        streams,
     })
 }
 
+/// Parse the ProgramInfo section: per-stream (pid, coding_type,
+/// language, codec sub-fields). Layout per BD spec / libbluray
+/// clpi_parse.c:
+///
+/// ```text
+/// ProgramInfo:
+///   length: 4 bytes
+///   reserved: 1 byte
+///   num_programs: 1 byte
+///   for each program:
+///     spn_program_sequence_start: 4 bytes
+///     program_map_pid: 2 bytes
+///     num_streams: 1 byte
+///     num_groups: 1 byte
+///     for each stream:
+///       pid: 2 bytes
+///       stream_coding_info_length: 1 byte
+///       stream_coding_info: (varies by coding_type)
+///         coding_type: 1 byte
+///         per-type bytes (see match arms below)
+/// ```
+///
+/// Returns `Vec::new()` on any structural mismatch — we don't propagate
+/// errors because the EP map is the primary CLPI output, and a corrupt
+/// program_info shouldn't break sector-range lookups.
+fn parse_program_info(data: &[u8]) -> Vec<ClpiStream> {
+    let mut out = Vec::new();
+    if data.len() < 6 {
+        return out;
+    }
+    // length: 4 bytes (skipped — we trust the section bounds in the
+    // caller's slice and read the bytes that follow). Reserved 1 byte
+    // at offset 4. num_programs at offset 5.
+    let num_programs = data[5] as usize;
+    let mut pos = 6usize;
+    for _ in 0..num_programs {
+        // Program header: 4 (spn) + 2 (pmt_pid) + 1 (num_streams) + 1 (num_groups) = 8 bytes
+        if pos + 8 > data.len() {
+            return out;
+        }
+        let num_streams = data[pos + 6] as usize;
+        pos += 8;
+
+        for _ in 0..num_streams {
+            // Stream header: 2 (pid) + 1 (sci_length) + sci bytes
+            if pos + 3 > data.len() {
+                return out;
+            }
+            let pid = u16::from_be_bytes([data[pos], data[pos + 1]]);
+            let sci_len = data[pos + 2] as usize;
+            let sci_end = pos + 3 + sci_len;
+            if sci_end > data.len() || sci_len < 1 {
+                return out;
+            }
+            let sci = &data[pos + 3..sci_end];
+            let coding_type = sci[0];
+
+            let mut audio_format = 0u8;
+            let mut audio_rate = 0u8;
+            let mut video_format = 0u8;
+            let mut video_rate = 0u8;
+            let mut language = String::new();
+
+            match coding_type {
+                // Video — MPEG-2 (0x02), H.264 (0x1B), HEVC (0x24)
+                0x02 | 0x1B | 0x24 => {
+                    if sci.len() >= 2 {
+                        video_format = (sci[1] >> 4) & 0x0F;
+                        video_rate = sci[1] & 0x0F;
+                    }
+                }
+                // Primary audio — LPCM(0x80), AC-3(0x81), DTS(0x82),
+                // TrueHD(0x83), AC-3+(0x84), DTS-HD(0x85), DTS-HD MA(0x86)
+                0x80..=0x86 => {
+                    if sci.len() >= 2 {
+                        audio_format = (sci[1] >> 4) & 0x0F;
+                        audio_rate = sci[1] & 0x0F;
+                    }
+                    if sci.len() >= 5 {
+                        language = String::from_utf8_lossy(&sci[2..5]).to_string();
+                    }
+                }
+                // Secondary audio (0xA1 AC-3+, 0xA2 DTS-HD)
+                0xA1 | 0xA2 => {
+                    if sci.len() >= 2 {
+                        audio_format = (sci[1] >> 4) & 0x0F;
+                        audio_rate = sci[1] & 0x0F;
+                    }
+                    if sci.len() >= 5 {
+                        language = String::from_utf8_lossy(&sci[2..5]).to_string();
+                    }
+                }
+                // PG (0x90), IG (0x91): coding_type + 3-byte language [+ char_code for PG]
+                0x90 | 0x91 => {
+                    if sci.len() >= 4 {
+                        language = String::from_utf8_lossy(&sci[1..4]).to_string();
+                    }
+                }
+                _ => {}
+            }
+
+            out.push(ClpiStream {
+                pid,
+                coding_type,
+                language,
+                audio_format,
+                audio_rate,
+                video_format,
+                video_rate,
+            });
+
+            pos = sci_end;
+        }
+    }
+    out
+}
+
 /// Parse the CPI section containing the EP map.
 fn parse_cpi(data: &[u8]) -> Result<(Vec<EpCoarse>, Vec<EpFine>)> {
     if data.len() < 8 {

src/css/auth.rs

@@ -4,13 +4,14 @@
 //!   1. Bus authentication (challenge-response) → bus key
 //!   2. Read disc key block (READ DVD STRUCTURE) → XOR with bus key → decrypt with player keys → disc key
 //!   3. Read title key (REPORT KEY format 0x04) → XOR with bus key → decrypt with disc key → title key
-//!
-//! Based on libdvdcss (VideoLAN) and Stevenson 1999 analysis.
 
 use crate::drive::Drive;
 use crate::error::{Error, Result};
 
-// ── Player keys (from libdvdcss, Stevenson's PlayerKey cracker) ───────────
+// ── Built-in public DVD CSS player keys ────────────────────────────────────
+//
+// These 31 5-byte player keys are long-public CSS inputs. With them
+// compiled in, DVD ripping works with no external key file required.
 
 const PLAYER_KEYS: [[u8; 5]; 31] = [
     [0x01, 0xaf, 0xe3, 0x12, 0x80],

src/css/mod.rs

@@ -16,7 +16,8 @@ pub mod lfsr;
 pub(crate) mod tables;
 
 use crate::disc::Extent;
-use crate::sector::SectorReader;
+use crate::drive::Drive;
+use crate::sector::SectorSource;
 
 /// CSS decryption state for a DVD title.
 #[derive(Debug, Clone)]
@@ -25,6 +26,50 @@ pub struct CssState {
     pub title_key: [u8; 5],
 }
 
+/// Inputs for CSS key acquisition.
+///
+/// The acquisition path depends on which inputs the caller supplies:
+///
+/// - With `drive` + `auth_lba` set, [`resolve`] runs the full SCSI bus
+///   auth + title-key path (live BU40N / DVD drive).
+/// - With `reader` + `extents` set, [`resolve`] falls back to the
+///   crack path (Stevenson known-plaintext attack on encrypted PES
+///   headers; works on disc images and on drives whose CSS auth path
+///   is unavailable).
+///
+/// `live_drive` always wins when both modes are populated.
+pub struct CssContext<'a> {
+    /// Live SCSI drive — when present, [`resolve`] tries the auth path.
+    pub drive: Option<&'a mut Drive>,
+    /// LBA of a known-scrambled sector for the auth path's title-key
+    /// query. Required when `drive` is set.
+    pub auth_lba: Option<u32>,
+    /// Sector source for the crack path.
+    pub reader: Option<&'a mut dyn SectorSource>,
+    /// Extents to scan for the crack path. Required when `reader` is
+    /// set.
+    pub extents: Option<&'a [Extent]>,
+}
+
+/// Acquire a CSS title key using whichever inputs the context provides.
+///
+/// Order of attempts:
+///   1. SCSI auth path (when `drive` and `auth_lba` are set).
+///   2. Crack path (when `reader` and `extents` are set).
+///
+/// Returns `None` if neither path is configured or both fail.
+pub fn resolve(ctx: &mut CssContext<'_>) -> Option<CssState> {
+    if let (Some(drive), Some(lba)) = (ctx.drive.as_deref_mut(), ctx.auth_lba) {
+        if let Ok(title_key) = auth::authenticate_and_read_title_key(drive, lba) {
+            return Some(CssState { title_key });
+        }
+    }
+    if let (Some(reader), Some(extents)) = (ctx.reader.as_deref_mut(), ctx.extents) {
+        return crack_key(reader, extents);
+    }
+    None
+}
+
 /// Crack the CSS title key by reading encrypted sectors and applying
 /// a known-plaintext attack on MPEG-2 headers.
 ///
@@ -34,7 +79,7 @@ pub struct CssState {
 /// 0x80 (start of the encrypted region). This only happens when a new PES
 /// packet begins at exactly sector offset 128. We scan up to 50000
 /// scrambled sectors sequentially across all extents.
-pub fn crack_key(reader: &mut dyn SectorReader, extents: &[Extent]) -> Option<CssState> {
+pub fn crack_key(reader: &mut dyn SectorSource, extents: &[Extent]) -> Option<CssState> {
     let mut tried = 0u32;
     let max_tries = 50_000;
 

src/decrypt.rs

@@ -3,9 +3,131 @@
 //! Decrypts sectors in-place using resolved keys from disc scanning.
 //! Handles AACS 1.0, AACS 2.0, and CSS transparently.
 //! The caller never sees encrypted data unless explicitly bypassed.
+//!
+//! ## Parallel AACS decrypt
+//!
+//! Each AACS aligned unit (6144 bytes) is decrypted INDEPENDENTLY of
+//! every other unit — per-unit key derivation from the unit_key plus
+//! the unit's own first-16-byte header. There is no cross-unit
+//! dependency, so a buffer of N units can be decrypted on N threads
+//! in parallel via a persistent rayon thread pool.
+//!
+//! Small buffers (< [`PARALLEL_MIN_UNITS`] units) fall through to the
+//! serial path to avoid pool dispatch overhead beating the per-unit
+//! AES work.
+//!
+//! ## Thread-count configuration — three layers
+//!
+//! Resolution order (highest wins):
+//! 1. The most recent [`set_decrypt_threads`] call with `n > 0`.
+//!    Calling this *replaces* the live thread pool — useful for a
+//!    settings-page slider in a long-running daemon.
+//! 2. `FREEMKV_THREADS` env var, if set and `> 0`. Single knob
+//!    covering decrypt today, intended to also drive any future
+//!    input-side / output-side worker pools.
+//! 3. Default: all available cores. Algorithm optimisation comes
+//!    first — we measure single-thread performance to find serial
+//!    bottlenecks before throwing parallelism at it — but once a
+//!    pool is engaged we use the whole box. Hard cap at
+//!    [`MAX_THREADS`] (rayon stack memory).
 
 use crate::aacs;
 use crate::css;
+use rayon::prelude::*;
+use std::sync::atomic::{AtomicUsize, Ordering};
+use std::sync::{Arc, RwLock};
+
+/// Minimum units in a buffer before we pay the pool-dispatch cost of
+/// fanning out. Below this, serial is faster.
+const PARALLEL_MIN_UNITS: usize = 8;
+
+/// Hard upper bound on configurable thread count. Anything larger is
+/// almost certainly a misconfiguration; rayon would happily allocate
+/// thousands of worker stacks otherwise.
+pub const MAX_THREADS: usize = 64;
+
+/// Process-wide decrypt thread count override. `0` means "use env
+/// var, else default" — see [`decrypt_threads`] for the resolution
+/// order.
+static DECRYPT_THREADS: AtomicUsize = AtomicUsize::new(0);
+
+/// Current rayon pool. `RwLock<Option<Arc<...>>>` so that
+/// [`set_decrypt_threads`] can swap the pool out without leaking the
+/// old one and without blocking ongoing decrypt work (in-flight calls
+/// hold an `Arc` clone via [`decrypt_pool`] and finish on the old
+/// pool; new calls pick up the new pool).
+static DECRYPT_POOL: RwLock<Option<Arc<rayon::ThreadPool>>> = RwLock::new(None);
+
+/// Configure how many threads to use for AACS unit decryption. A value
+/// of `0` resets to the env / default resolution. `1` forces serial.
+/// `N > 1` builds a new rayon pool of size N and atomically replaces
+/// the live pool.
+///
+/// Thread-safe. Live decrypt calls keep their previously-acquired
+/// pool reference for the rest of the call — no mid-call pool
+/// switch. Subsequent calls see the new pool.
+///
+/// Pool construction is ~ms-scale; safe to call from a settings POST
+/// handler.
+pub fn set_decrypt_threads(n: usize) {
+    let clamped = n.min(MAX_THREADS);
+    DECRYPT_THREADS.store(clamped, Ordering::Relaxed);
+    // Drop the existing pool. Next decrypt_pool() call rebuilds with
+    // the new resolved thread count.
+    if let Ok(mut guard) = DECRYPT_POOL.write() {
+        *guard = None;
+    }
+}
+
+/// Get (or lazily build) the active rayon thread pool. Returns an
+/// `Arc` so in-flight work survives a concurrent
+/// [`set_decrypt_threads`] swap.
+fn decrypt_pool() -> Arc<rayon::ThreadPool> {
+    // Fast path: pool already built.
+    if let Ok(guard) = DECRYPT_POOL.read() {
+        if let Some(pool) = guard.as_ref() {
+            return Arc::clone(pool);
+        }
+    }
+    // Slow path: build a new one under the write lock. Double-check
+    // after acquiring in case another caller built it first.
+    let mut guard = DECRYPT_POOL.write().expect("DECRYPT_POOL RwLock poisoned");
+    if let Some(pool) = guard.as_ref() {
+        return Arc::clone(pool);
+    }
+    let n = decrypt_threads();
+    let pool = Arc::new(
+        rayon::ThreadPoolBuilder::new()
+            .num_threads(n)
+            .thread_name(|i| format!("freemkv-decrypt-{i}"))
+            .build()
+            .expect("rayon decrypt pool build failed"),
+    );
+    *guard = Some(Arc::clone(&pool));
+    pool
+}
+
+/// Current effective decrypt thread count. Resolution order:
+/// 1. Most recent [`set_decrypt_threads`] value (if > 0)
+/// 2. `FREEMKV_THREADS` env var (if set and > 0)
+/// 3. Default: all available cores, capped at [`MAX_THREADS`].
+pub fn decrypt_threads() -> usize {
+    let explicit = DECRYPT_THREADS.load(Ordering::Relaxed);
+    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)
+}
 
 /// Resolved decryption state from disc scanning.
 /// Passed to `decrypt_sectors()` — the caller doesn't need to know
@@ -57,13 +179,45 @@ pub fn decrypt_sectors(
                     return Err(crate::error::Error::DecryptFailed);
                 }
             };
-            let rdk = read_data_key.as_ref();
+            let rdk: Option<[u8; 16]> = *read_data_key;
             let unit_len = aacs::ALIGNED_UNIT_LEN;
+            let nthreads = decrypt_threads();
+            let chunks: Vec<&mut [u8]> = buf.chunks_mut(unit_len).collect();
+            let nunits = chunks.len();
 
-            for chunk in buf.chunks_mut(unit_len) {
-                if chunk.len() == unit_len && aacs::is_unit_encrypted(chunk) {
-                    aacs::decrypt_unit_full(chunk, &uk, rdk);
+            // Per-unit decrypt closure. The is_aacs_scrambled check reads the
+            // raw TS syncs; a non-m2ts unit (e.g. MPLS/CLPI nav file) can look
+            // scrambled and trigger a decrypt attempt, so on a verify miss we
+            // snapshot+restore the original bytes so it survives. See test
+            // `nav_file_unit_survives_decrypt_attempt`.
+            let decrypt_one = |chunk: &mut [u8]| {
+                if chunk.len() == unit_len && aacs::is_aacs_scrambled(chunk) {
+                    let original: Vec<u8> = chunk.to_vec();
+                    if !aacs::decrypt_unit_full(chunk, &uk, rdk.as_ref()) {
+                        chunk.copy_from_slice(&original);
+                    }
                 }
+            };
+
+            if nthreads <= 1 || nunits < PARALLEL_MIN_UNITS {
+                // Serial path: avoids thread-pool overhead for tiny
+                // buffers; also the only path when caller pinned
+                // single-threaded via FREEMKV_THREADS=1.
+                for chunk in chunks {
+                    decrypt_one(chunk);
+                }
+            } else {
+                // Parallel path via rayon's persistent global pool.
+                // The pool is built once on first use (lazy_static-style)
+                // and reused across every decrypt_sectors call — no
+                // per-call OS thread spawn, no thread-creation latency
+                // amortised per batch. Each unit decrypts independently
+                // (own key derivation), so par_iter is sound.
+                decrypt_pool().install(|| {
+                    chunks.into_par_iter().for_each(|chunk| {
+                        decrypt_one(chunk);
+                    });
+                });
             }
         }
         DecryptKeys::Css { title_key } => {
@@ -74,3 +228,36 @@ pub fn decrypt_sectors(
     }
     Ok(())
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    /// Regression for the 0.18.1 nav-file scramble bug. A non-m2ts unit (here
+    /// an MPLS file: starts "MPLS", carries no TS syncs) reads as scrambled
+    /// under `is_aacs_scrambled`, gets AES-decrypted with the unit key, fails
+    /// the TS-sync verification, and must be restored to its original bytes —
+    /// not left scrambled.
+    #[test]
+    fn nav_file_unit_survives_decrypt_attempt() {
+        let mut unit = vec![0u8; aacs::ALIGNED_UNIT_LEN];
+        unit[0] = b'M';
+        unit[1] = b'P';
+        unit[2] = b'L';
+        unit[3] = b'S';
+        for (i, b) in unit.iter_mut().enumerate().skip(4) {
+            *b = (i as u8).wrapping_mul(31);
+        }
+        let snapshot = unit.clone();
+
+        let keys = DecryptKeys::Aacs {
+            unit_keys: vec![(0, [0xAB; 16])],
+            read_data_key: None,
+        };
+        decrypt_sectors(&mut unit, &keys, 0).unwrap();
+        assert_eq!(
+            unit, snapshot,
+            "non-m2ts unit must be restored after failed decrypt"
+        );
+    }
+}

src/disc/bluray.rs

@@ -3,13 +3,13 @@
 use super::*;
 use crate::clpi;
 use crate::mpls;
-use crate::sector::SectorReader;
+use crate::sector::SectorSource;
 use crate::udf;
 
 impl Disc {
     /// Scan Blu-ray titles from MPLS playlists.
     pub(super) fn scan_bluray_titles(
-        reader: &mut dyn SectorReader,
+        reader: &mut dyn SectorSource,
         udf_fs: &udf::UdfFs,
     ) -> Vec<DiscTitle> {
         let mut titles = Vec::new();
@@ -31,7 +31,7 @@ impl Disc {
     }
 
     pub(super) fn parse_playlist(
-        reader: &mut dyn SectorReader,
+        reader: &mut dyn SectorSource,
         udf_fs: &udf::UdfFs,
         filename: &str,
         data: &[u8],
@@ -199,7 +199,7 @@ impl Disc {
     /// Prefers English, falls back to first available language.
     /// Returns None if META directory is empty or XML has no usable title.
     pub(super) fn read_meta_title(
-        reader: &mut dyn SectorReader,
+        reader: &mut dyn SectorSource,
         udf_fs: &udf::UdfFs,
     ) -> Option<String> {
         let meta_dir = udf_fs.find_dir("/BDMV/META")?;

src/disc/dvd.rs

@@ -2,13 +2,13 @@
 
 use super::*;
 use crate::ifo;
-use crate::sector::SectorReader;
+use crate::sector::SectorSource;
 use crate::udf;
 
 impl Disc {
     /// Scan DVD titles from IFO files (VIDEO_TS.IFO + VTS_XX_0.IFO).
     pub(super) fn scan_dvd_titles(
-        reader: &mut dyn SectorReader,
+        reader: &mut dyn SectorSource,
         udf_fs: &udf::UdfFs,
     ) -> Vec<DiscTitle> {
         let dvd_info = match ifo::parse_vmg(reader, udf_fs) {

src/disc/encrypt.rs

@@ -2,7 +2,7 @@
 
 use super::*;
 use crate::error::{Error, Result};
-use crate::sector::SectorReader;
+use crate::sector::SectorSource;
 use crate::udf;
 
 /// Result of SCSI AACS handshake (ECDH authentication).
@@ -14,107 +14,359 @@ pub(super) struct HandshakeResult {
 }
 
 impl Disc {
-    /// SCSI handshake result — volume ID and bus keys from ECDH authentication.
-    /// Only available when scanning from a real drive (not ISO images).
+    /// Acquire the Volume ID. Tries the per-drive OEM CDB path first
+    /// when the drive reports `is_unlocked()` (extended-access state),
+    /// and falls back to the cert-based AACS mutual-auth handshake
+    /// otherwise.
+    ///
+    /// The OEM path is a single READ_BUFFER CDB built from the drive
+    /// profile's `read_vid_cdb` template. The response carries a 3-byte
+    /// header (validated against `00 22 00`) followed by the 16-byte
+    /// VID at bytes [4..20]. Crucially, no AGID setup is required —
+    /// the drive's runtime firmware serves the VID directly when in
+    /// extended-access state.
+    ///
+    /// The cert path is the standard AACS spec flow: ECDH key
+    /// agreement, bus-key derivation, then `REPORT_DISC_STRUCTURE`
+    /// format 0x80 to retrieve VID under bus-key MAC.
+    pub(super) fn read_vid(
+        session: &mut crate::drive::Drive,
+        opts: &ScanOptions,
+    ) -> Result<[u8; 16]> {
+        if session.is_unlocked() {
+            let profile = session
+                .drive_profile()
+                .ok_or(Error::DriveProfileMissing)?
+                .clone();
+            return Self::read_vid_oem(session, &profile);
+        }
+        Self::read_vid_cert(session, opts)
+    }
+
+    /// OEM VID retrieval — issues the per-drive READ_BUFFER CDB and
+    /// parses the response.
+    ///
+    /// Response layout (36 bytes):
+    ///   * [0..3]   3-byte response signature; expected `00 22 00`
+    ///   * [3]      reserved
+    ///   * [4..20]  16-byte Volume ID
+    ///   * [20..36] reserved / per-drive padding
+    fn read_vid_oem(
+        session: &mut crate::drive::Drive,
+        profile: &crate::profile::DriveProfile,
+    ) -> Result<[u8; 16]> {
+        const RESPONSE_LEN: usize = 36;
+        const EXPECTED_HEADER: [u8; 3] = [0x00, 0x22, 0x00];
+
+        let cdb = profile.read_vid_cdb.ok_or(Error::VidCdbUnavailable)?;
+        let mut buf = vec![0u8; RESPONSE_LEN];
+        let result = session.scsi_execute(
+            &cdb,
+            crate::scsi::DataDirection::FromDevice,
+            &mut buf,
+            5_000,
+        )?;
+        if result.bytes_transferred < RESPONSE_LEN {
+            tracing::warn!(
+                target: "freemkv::disc",
+                phase = "oem_vid_short_response",
+                bytes_transferred = result.bytes_transferred,
+                "OEM VID CDB returned short response"
+            );
+            return Err(Error::AacsVidRead);
+        }
+        if buf[0..3] != EXPECTED_HEADER {
+            tracing::warn!(
+                target: "freemkv::disc",
+                phase = "oem_vid_bad_header",
+                header_0 = buf[0],
+                header_1 = buf[1],
+                header_2 = buf[2],
+                "OEM VID response header mismatch"
+            );
+            return Err(Error::AacsVidRead);
+        }
+        let mut vid = [0u8; 16];
+        vid.copy_from_slice(&buf[4..20]);
+        tracing::warn!(
+            target: "freemkv::disc",
+            phase = "oem_vid_ok",
+            "OEM VID retrieved"
+        );
+        Ok(vid)
+    }
+
+    /// Cert-based VID retrieval — runs the full AACS mutual-auth
+    /// handshake and extracts VID from the bus-key-MAC'd
+    /// `REPORT_DISC_STRUCTURE` response.
+    fn read_vid_cert(session: &mut crate::drive::Drive, opts: &ScanOptions) -> Result<[u8; 16]> {
+        match Self::do_handshake_cert(session, opts) {
+            (Some(h), _) => Ok(h.volume_id),
+            (None, Some(e)) => Err(e),
+            (None, None) => Err(Error::AacsVidUnavailable),
+        }
+    }
+
+    /// SCSI handshake — drives the VID-acquisition flow and returns
+    /// a structured `HandshakeResult` for downstream key resolution.
+    /// Prefers the OEM path when `Drive::is_unlocked()` is true and
+    /// falls back to cert-based mutual auth otherwise.
+    ///
+    /// The OEM path produces only VID (no bus-key, so no
+    /// `read_data_key`); the cert path can produce both. AACS 2.0
+    /// content that needs read_data_key for bus decryption requires
+    /// the cert path.
+    ///
+    /// Returns `(handshake, error)`:
+    ///   * `(Some(_), None)`  — VID acquired
+    ///   * `(None, Some(_))`  — specific failure mode (see
+    ///     `AacsHostCertRejected` / `AacsRawReadUnsupported` /
+    ///     `AacsVidUnavailable` / `DriveProfileMissing` /
+    ///     `VidCdbUnavailable` variants in `error.rs`)
+    ///   * `(None, None)`     — handshake not attempted (no keydb;
+    ///     resolution will proceed with VID=zero and rely on path 1
+    ///     disc-hash → VUK lookup)
     pub(super) fn do_handshake(
         session: &mut crate::drive::Drive,
         opts: &ScanOptions,
-    ) -> Option<HandshakeResult> {
-        use crate::aacs::{self, KeyDb};
+    ) -> (Option<HandshakeResult>, Option<Error>) {
+        let unlocked = session.is_unlocked();
+        tracing::warn!(
+            target: "freemkv::disc",
+            phase = "handshake_entry",
+            unlocked,
+            "do_handshake entered"
+        );
 
-        let keydb_path = opts.resolve_keydb()?;
-        let keydb = KeyDb::load(&keydb_path).ok()?;
+        if unlocked {
+            // Try OEM VID retrieval first. If the drive's profile
+            // doesn't carry the CDB template, or the response is
+            // malformed, fall through to cert-based auth.
+            match Self::read_vid(session, opts) {
+                Ok(volume_id) => {
+                    return (
+                        Some(HandshakeResult {
+                            volume_id,
+                            read_data_key: None,
+                        }),
+                        None,
+                    );
+                }
+                Err(Error::DriveProfileMissing) | Err(Error::VidCdbUnavailable) => {
+                    tracing::warn!(
+                        target: "freemkv::disc",
+                        phase = "handshake_oem_unavailable",
+                        "OEM VID path unavailable for this drive; trying cert handshake"
+                    );
+                }
+                Err(e) => {
+                    tracing::warn!(
+                        target: "freemkv::disc",
+                        phase = "handshake_oem_failed",
+                        error_code = e.code(),
+                        "OEM VID retrieval failed; trying cert handshake"
+                    );
+                }
+            }
+        }
 
-        const MAX_CERT_ATTEMPTS: usize = 16;
-        for hc in keydb.host_certs.iter().take(MAX_CERT_ATTEMPTS) {
+        Self::do_handshake_cert(session, opts)
+    }
+
+    /// Cert-based AACS handshake. The legacy auth path; still used as
+    /// the fallback when the OEM VID path isn't available or fails.
+    fn do_handshake_cert(
+        session: &mut crate::drive::Drive,
+        opts: &ScanOptions,
+    ) -> (Option<HandshakeResult>, Option<Error>) {
+        use crate::aacs;
+
+        // Host certs come from the caller's DriveCredentials (e.g. the keydb's
+        // host_certs(), sourced app-side) — the library does not load a keydb.
+        // Absent ⇒ no cert auth: an unlocked / LibreDrive drive already returned
+        // a Volume ID via the OEM path before reaching here, so this is the
+        // locked-drive-without-credentials case.
+        let host_certs: &[aacs::HostCert] = match &opts.credentials {
+            Some(c) if !c.host_certs.is_empty() => &c.host_certs,
+            _ => {
+                tracing::warn!(
+                    target: "freemkv::disc",
+                    phase = "handshake_no_credentials",
+                    "no drive credentials supplied; cert handshake skipped"
+                );
+                return (None, None);
+            }
+        };
+
+        let host_cert_count = host_certs.len();
+        tracing::warn!(
+            target: "freemkv::disc",
+            phase = "handshake_start",
+            host_cert_count,
+            "handshake starting"
+        );
+
+        // v0.25.7 wedge fix. Pre-0.25.7 this loop fired up to 16 AACS
+        // authenticate attempts back-to-back with no pause. Each attempt
+        // is 5-10 SCSI REPORT_KEY/SEND_KEY exchanges. On a disc whose
+        // host cert isn't in our KEYDB (or one the drive rejects),
+        // that's 80-160 SCSI commands hammered at the drive in a
+        // few hundred milliseconds — and the BU40N (and most consumer
+        // optical drives) responds by entering a fast-fail firmware
+        // wedge state where every subsequent CDB returns
+        // ILLEGAL_REQUEST/INVALID_FIELD_IN_CDB (sense 05/24) until
+        // power-cycled. Hit live on rip1 2026-05-20 during a MOVIE
+        // UHD scan: KEYDB miss → 16 cert attempts in a tight loop →
+        // wedge → forced host reboot + drive disconnect to recover.
+        //
+        // Defense-in-depth: cap attempts, sleep between, and bail
+        // early on the drive's wedge sense so any later regression
+        // can't undo the protection silently.
+        const MAX_CERT_ATTEMPTS: usize = 3;
+        const PER_CERT_BACKOFF_MS: u64 = 1000;
+        let mut last_err_code: Option<u16> = None;
+        for (idx, hc) in host_certs.iter().take(MAX_CERT_ATTEMPTS).enumerate() {
+            if idx > 0 {
+                std::thread::sleep(std::time::Duration::from_millis(PER_CERT_BACKOFF_MS));
+            }
             match aacs::handshake::aacs_authenticate(session, &hc.private_key, &hc.certificate) {
                 Ok(mut auth) => {
                     let volume_id = match aacs::handshake::read_volume_id(session, &mut auth) {
                         Ok(vid) => vid,
-                        Err(_) => return None, // handshake succeeded but can't read VID
+                        Err(e) => {
+                            tracing::warn!(
+                                target: "freemkv::disc",
+                                phase = "handshake_vid_read_failed",
+                                cert_index = idx,
+                                error_code = e.code(),
+                                "auth ok but volume ID read failed"
+                            );
+                            return (None, Some(Error::AacsVidUnavailable));
+                        }
                     };
                     let read_data_key = aacs::handshake::read_data_keys(session, &mut auth)
                         .ok()
                         .map(|(rdk, _)| rdk);
-                    return Some(HandshakeResult {
-                        volume_id,
-                        read_data_key,
-                    });
+                    tracing::debug!(
+                        target: "freemkv::disc",
+                        phase = "handshake_ok",
+                        cert_index = idx,
+                        has_read_data_key = read_data_key.is_some(),
+                    );
+                    return (
+                        Some(HandshakeResult {
+                            volume_id,
+                            read_data_key,
+                        }),
+                        None,
+                    );
                 }
-                Err(_) => {
+                Err(e) => {
+                    let code = e.code();
+                    last_err_code = Some(code);
+                    // Drive wedge senses (any with high byte 0x05 =
+                    // ILLEGAL_REQUEST). The drive isn't merely
+                    // rejecting our cert — it's saying "I won't talk
+                    // to you anymore." Trying more certs makes the
+                    // wedge worse. Bail out immediately.
+                    let sense_key = ((code >> 8) & 0xFF) as u8;
+                    if sense_key == 0x05 {
+                        tracing::warn!(
+                            target: "freemkv::disc",
+                            phase = "handshake_wedge_detected",
+                            cert_index = idx,
+                            error_code = code,
+                            "drive returned ILLEGAL_REQUEST during auth; bailing out to avoid wedge"
+                        );
+                        return (None, Some(Error::AacsHostCertRejected));
+                    }
                     continue;
                 }
             }
         }
-        // All host certs failed — return None, not a fake success
-        None
+        tracing::warn!(
+            target: "freemkv::disc",
+            phase = "handshake_all_certs_failed",
+            host_cert_count,
+            tried = host_cert_count.min(MAX_CERT_ATTEMPTS),
+            last_error_code = last_err_code,
+            "all host certs in KEYDB rejected by drive (capped at {} attempts to prevent firmware wedge)",
+            MAX_CERT_ATTEMPTS
+        );
+        (None, Some(Error::AacsHostCertRejected))
     }
 
-    /// Resolve disc encryption — AACS 1.0, AACS 2.0, CSS, or none.
-    ///
-    /// Reads AACS files from UDF (via SectorReader), resolves keys through
-    /// whatever path works: KEYDB VUK lookup, media key derivation, processing
-    /// keys, device keys. Uses handshake result (volume ID, bus key) if available.
-    pub(super) fn resolve_encryption(
+    /// Build a keys-free AACS state that carries only the Volume ID (+ version
+    /// metadata), for callers that resolve Unit Keys out-of-band and have
+    /// disabled the local keydb. The VID is on-disc content read during the
+    /// handshake; preserving it here lets the out-of-band path use it. No keys
+    /// are present (`unit_keys` empty, `vuk` None), so the disc reports as
+    /// "encrypted, no keys" until the caller re-scans with a resolved Unit Key.
+    pub(super) fn resolve_vid_only(
         udf_fs: &udf::UdfFs,
-        reader: &mut dyn SectorReader,
-        keydb_path: &std::path::Path,
+        reader: &mut dyn SectorSource,
         handshake: Option<&HandshakeResult>,
     ) -> Result<AacsState> {
-        use crate::aacs::{self, KeyDb};
+        use crate::aacs;
 
-        let keydb = KeyDb::load(keydb_path).map_err(|_| Error::KeydbLoad {
-            path: keydb_path.display().to_string(),
-        })?;
-
-        // Read AACS files from disc/image via UDF
         let uk_ro_data = udf_fs
             .read_file(reader, "/AACS/Unit_Key_RO.inf")
             .or_else(|_| udf_fs.read_file(reader, "/AACS/DUPLICATE/Unit_Key_RO.inf"))
             .map_err(|_| Error::AacsNoKeys)?;
+        let dh = aacs::disc_hash(&uk_ro_data);
 
-        let cc_data = udf_fs
+        let cc = udf_fs
             .read_file(reader, "/AACS/Content000.cer")
             .or_else(|_| udf_fs.read_file(reader, "/AACS/Content001.cer"))
-            .ok();
+            .ok()
+            .as_deref()
+            .and_then(aacs::parse_content_cert);
+        let bus_encryption = cc.as_ref().map(|c| c.bus_encryption).unwrap_or(false);
+        let version = match cc.as_ref().map(|c| c.version) {
+            Some(aacs::AacsVersion::V10) => 1,
+            Some(_) => 2,
+            None if bus_encryption => 2,
+            None => 1,
+        };
+        // MKB_RO/RW are allocated to a fixed ~128 MiB and zero-padded; trim to
+        // the real record length (same as `read_aacs_inputs`). Without this the
+        // MKB stashed on `AacsState` — which `Disc::inputs()` and the device/
+        // processing-key `decrypt_with` derivation consume, and which a key
+        // source ships to an online service — is the full 128 MiB pad, not the
+        // ~few-MB record stream.
+        let mut mkb_bytes = udf_fs
+            .read_file(reader, "/AACS/MKB_RO.inf")
+            .or_else(|_| udf_fs.read_file(reader, "/AACS/MKB_RW.inf"))
+            .ok()
+            .unwrap_or_default();
+        let n = aacs::mkb_content_len(&mkb_bytes);
+        if n > 0 && n < mkb_bytes.len() {
+            mkb_bytes.truncate(n);
+        }
+        let mkb_ver = aacs::mkb_version(&mkb_bytes);
 
-        let mkb_data = udf_fs
-            .read_file(reader, "/AACS/MKB_RW.inf")
-            .or_else(|_| udf_fs.read_file(reader, "/AACS/MKB_RO.inf"))
-            .ok();
-        let mkb_ver = mkb_data.as_deref().and_then(aacs::mkb_version);
-
-        // Use handshake volume ID if available, otherwise zeros
-        // (KEYDB VUK lookup by disc hash works without volume ID)
-        let volume_id = handshake.map(|h| h.volume_id).unwrap_or([0u8; 16]);
-        let read_data_key = handshake.and_then(|h| h.read_data_key);
-
-        // Resolve: tries all available paths — KEYDB VUK, media key, processing key, device key
-        let resolved = aacs::resolve_keys(
-            &uk_ro_data,
-            cc_data.as_deref(),
-            &volume_id,
-            &keydb,
-            mkb_data.as_deref(),
-        )
-        .ok_or(Error::AacsNoKeys)?;
+        tracing::warn!(
+            target: "freemkv::disc",
+            phase = "scan_aacs_vid_only",
+            disc_hash = %aacs::disc_hash_hex(&dh),
+            version,
+            bus_encryption,
+            has_vid = handshake.is_some(),
+            "keydb disabled — carrying VID only, keys resolved out-of-band"
+        );
 
         Ok(AacsState {
-            version: if resolved.aacs2 { 2 } else { 1 },
-            bus_encryption: resolved.bus_encryption,
+            version,
+            bus_encryption,
             mkb_version: mkb_ver,
-            disc_hash: aacs::disc_hash_hex(&resolved.disc_hash),
-            key_source: match resolved.key_source {
-                1 => KeySource::KeyDb,
-                2 => KeySource::KeyDbDerived,
-                3 => KeySource::ProcessingKey,
-                4 => KeySource::DeviceKey,
-                _ => KeySource::KeyDb,
-            },
-            vuk: resolved.vuk,
-            unit_keys: resolved.unit_keys,
-            read_data_key,
-            volume_id,
+            disc_hash: aacs::disc_hash_hex(&dh),
+            key_source: KeyOrigin::ExternalUk,
+            vuk: None,
+            unit_keys: vec![],
+            read_data_key: handshake.and_then(|h| h.read_data_key),
+            volume_id: handshake.map(|h| h.volume_id).unwrap_or([0u8; 16]),
+            uk_ro: uk_ro_data,
+            mkb: mkb_bytes,
         })
     }
 }

src/disc/mapfile.rs

@@ -17,11 +17,22 @@
 //!
 //! Status chars: `?` non-tried · `*` non-trimmed · `/` non-scraped · `-` unreadable · `+` finished.
 //!
-//! The mapfile is flushed to disk on every `record()` call so a crashed
-//! rip loses at most one block of recorded state.
+//! The mapfile is flushed to disk at most once per `FLUSH_INTERVAL`
+//! during `record()` calls, plus on explicit `flush()` and on `Drop`.
+//! This bounds atomic-rename RPC rate on networked staging (e.g. NFS)
+//! where per-record persists otherwise serialize the rip pipeline.
 
 use std::io::{self, Write};
 use std::path::{Path, PathBuf};
+use std::time::{Duration, Instant};
+
+/// Minimum interval between mapfile persists. `record()` updates in-memory
+/// state every call but only writes to disk when this interval has elapsed
+/// since the last persist (or when `flush()` is called explicitly, or on
+/// `Drop`). Bounds RPC rate on NFS staging where atomic-rename per record
+/// otherwise dominates throughput. On crash the worst-case progress loss
+/// is one interval's worth of records.
+const FLUSH_INTERVAL: Duration = Duration::from_millis(1000);
 
 /// Status of a byte range in the mapfile. ddrescue-compatible.
 #[derive(Debug, Clone, Copy, PartialEq, Eq)]
@@ -91,15 +102,49 @@ pub struct MapStats {
     /// retry" UI bucket; `bytes_pending` over-counts because it folds
     /// in `bytes_nontried`.
     pub bytes_retryable: u64,
+    /// Number of unreadable ranges (for UI display). Computed from
+    /// `ranges_with(&[Unreadable])`.
+    pub num_bad_ranges: u32,
+    /// Largest gap among unreadable ranges in milliseconds. Computed as
+    /// largest range size / bytes_per_sec * 1000. Set by caller (autorip)
+    /// since bytes_per_sec is application-specific.
+    pub main_lost_ms: f64,
 }
 
-/// Write-through mapfile. Every `record()` persists to disk immediately
-/// so a crash during rip loses at most one block.
+/// Time-batched mapfile. `record()` keeps in-memory state up-to-date on
+/// every call; persists to disk at most once per `FLUSH_INTERVAL`.
+/// Explicit `flush()` and `Drop` guarantee state is on disk after a sweep
+/// or patch finishes. On hard crash the worst-case loss is one flush
+/// interval of records — the file's payload bytes are unaffected.
 pub struct Mapfile {
     path: PathBuf,
     entries: Vec<MapEntry>,
     total_size: u64,
     version: String,
+    /// Incrementally maintained stats — updated on every `record()` call
+    /// so `stats()` is O(1) instead of O(n).
+    stats: MapStats,
+    /// True when in-memory state has changed but `write_to_disk` has not
+    /// yet captured it.
+    dirty: bool,
+    /// Wall-clock timestamp of the last successful `write_to_disk` (or
+    /// the moment the mapfile was constructed, whichever is later).
+    last_flushed: Instant,
+    /// AACS Volume ID (16 bytes) for the disc, persisted as a
+    /// `# freemkv-vid:` comment header so it survives to deferred-mux /
+    /// resume without altering the ISO payload or breaking ddrescue
+    /// data-line parsing. `None` for unencrypted / non-AACS discs.
+    ///
+    /// MUTUALLY EXCLUSIVE with `unit_keys`: a disc whose keys were resolved
+    /// persists the keys (`unit_keys`) and NOT the VID — the keys are the final
+    /// answer, so deferred-mux/resume decrypts directly with no key service. A
+    /// disc that did NOT resolve persists only the VID, the retry-able "still
+    /// need a key" marker (a future mux can re-ask the key service with it).
+    vid: Option<[u8; 16]>,
+    /// Decrypted AACS unit keys `(CPS unit, key)`, persisted as `# freemkv-uk:`
+    /// comment headers when the disc was successfully keyed. Mutually exclusive
+    /// with `vid` (see above). Empty when unresolved.
+    unit_keys: Vec<(u32, [u8; 16])>,
 }
 
 impl Mapfile {
@@ -107,7 +152,7 @@ impl Mapfile {
     /// Writes to disk immediately so a resume can pick up even if the caller
     /// never records anything.
     pub fn create(path: &Path, total_size: u64, version: &str) -> io::Result<Self> {
-        let mf = Self {
+        let mut mf = Self {
             path: path.to_path_buf(),
             entries: vec![MapEntry {
                 pos: 0,
@@ -116,8 +161,21 @@ impl Mapfile {
             }],
             total_size,
             version: version.to_string(),
+            stats: MapStats {
+                bytes_total: total_size,
+                bytes_pending: total_size,
+                bytes_nontried: total_size,
+                ..Default::default()
+            },
+            dirty: false,
+            last_flushed: Instant::now(),
+            vid: None,
+            unit_keys: Vec::new(),
         };
+        // Eager initial persist so a resume can pick this up even if
+        // `record()` is never called.
         mf.write_to_disk()?;
+        mf.last_flushed = Instant::now();
         Ok(mf)
     }
 
@@ -127,6 +185,8 @@ impl Mapfile {
         let mut entries = Vec::new();
         let mut saw_current_line = false;
         let mut version = String::from("unknown");
+        let mut vid: Option<[u8; 16]> = None;
+        let mut unit_keys: Vec<(u32, [u8; 16])> = Vec::new();
         for line in text.lines() {
             let t = line.trim();
             if t.is_empty() {
@@ -137,6 +197,17 @@ impl Mapfile {
                 if let Some(v) = rest.strip_prefix("Rescue Logfile. Created by ") {
                     version = v.to_string();
                 }
+                if let Some(hex) = rest.strip_prefix("freemkv-vid:") {
+                    // Best-effort: a malformed or short VID comment is
+                    // ignored rather than failing the whole load.
+                    vid = parse_vid_hex(hex.trim());
+                }
+                if let Some(uk) = rest.strip_prefix("freemkv-uk:") {
+                    // `<cps>:<32hex>`. Best-effort: a malformed line is skipped.
+                    if let Some(entry) = parse_uk_line(uk.trim()) {
+                        unit_keys.push(entry);
+                    }
+                }
                 continue;
             }
             // First non-comment line is the "current" state line (pos status [pass] [pass_time]).
@@ -177,11 +248,17 @@ impl Mapfile {
         }
         entries.sort_by_key(|e| e.pos);
         let total_size = entries.last().map(|e| e.pos + e.size).unwrap_or(0);
+        let stats = Self::compute_stats(&entries, total_size);
         Ok(Self {
             path: path.to_path_buf(),
             entries,
             total_size,
             version,
+            stats,
+            dirty: false,
+            last_flushed: Instant::now(),
+            vid,
+            unit_keys,
         })
     }
 
@@ -244,11 +321,68 @@ impl Mapfile {
             merged.push(e);
         }
 
+        // Recompute stats from merged entries. record() is already O(n) due to
+        // drain-and-rebuild, so this is a constant-factor overhead. The critical
+        // win is that stats() is now O(1) — called millions of times in the hot
+        // path during sweep/patch, it just returns the cached value.
+        self.stats = Self::compute_stats(&merged, self.total_size);
         self.entries = merged;
-        self.write_to_disk()?;
+        self.dirty = true;
+        if self.last_flushed.elapsed() >= FLUSH_INTERVAL {
+            self.write_to_disk()?;
+            self.dirty = false;
+            self.last_flushed = Instant::now();
+        }
         Ok(())
     }
 
+    /// Persist any pending in-memory changes to disk. No-op if clean.
+    /// Callers (sweep/patch finalisation) invoke this after their last
+    /// `record()` to guarantee state is durable before returning.
+    pub fn flush(&mut self) -> io::Result<()> {
+        if self.dirty {
+            self.write_to_disk()?;
+            self.dirty = false;
+            self.last_flushed = Instant::now();
+        }
+        Ok(())
+    }
+
+    /// Record the disc's 16-byte AACS Volume ID so it persists in the
+    /// mapfile's comment header. Marks the mapfile dirty; the next
+    /// `flush()` / `Drop` writes the `# freemkv-vid:` line. Does not
+    /// touch the ISO payload or the ddrescue data lines.
+    pub fn set_vid(&mut self, vid: [u8; 16]) {
+        self.vid = Some(vid);
+        self.dirty = true;
+    }
+
+    /// The disc's AACS Volume ID, if one was set or parsed from a
+    /// `# freemkv-vid:` comment on load. `None` for unencrypted /
+    /// non-AACS discs.
+    pub fn vid(&self) -> Option<[u8; 16]> {
+        self.vid
+    }
+
+    /// Record the disc's decrypted AACS unit keys so they persist in the
+    /// mapfile header (`# freemkv-uk:` lines). The KEYED state: a deferred-mux /
+    /// resume decrypts directly from these with no key-service round-trip.
+    /// Setting keys clears any VID — the mapfile holds keys XOR VID, never both
+    /// (keys are the final answer; VID is only the "still unresolved" marker).
+    pub fn set_unit_keys(&mut self, keys: &[(u32, [u8; 16])]) {
+        self.unit_keys = keys.to_vec();
+        if !self.unit_keys.is_empty() {
+            self.vid = None;
+        }
+        self.dirty = true;
+    }
+
+    /// The disc's decrypted AACS unit keys, if the disc was keyed (parsed from
+    /// `# freemkv-uk:` comments on load). Empty = unresolved (check `vid()`).
+    pub fn unit_keys(&self) -> &[(u32, [u8; 16])] {
+        &self.unit_keys
+    }
+
     pub fn entries(&self) -> &[MapEntry] {
         &self.entries
     }
@@ -283,11 +417,15 @@ impl Mapfile {
     }
 
     pub fn stats(&self) -> MapStats {
+        self.stats
+    }
+
+    fn compute_stats(entries: &[MapEntry], total_size: u64) -> MapStats {
         let mut s = MapStats {
-            bytes_total: self.total_size,
+            bytes_total: total_size,
             ..Default::default()
         };
-        for e in &self.entries {
+        for e in entries {
             match e.status {
                 SectorStatus::Finished => s.bytes_good += e.size,
                 SectorStatus::Unreadable => s.bytes_unreadable += e.size,
@@ -317,6 +455,30 @@ impl Mapfile {
             let file = std::fs::File::create(&tmp)?;
             let mut w = std::io::BufWriter::new(file);
             writeln!(w, "# Rescue Logfile. Created by {}", self.version)?;
+            // VID comment lives in the header block. ddrescue treats any
+            // `#`-prefixed line as a comment, so this round-trips through
+            // our `load()` without affecting the `pos size status` data
+            // parser. 16 bytes → 32 lowercase hex chars.
+            // KEYS XOR VID: a keyed disc persists its unit keys (the final
+            // answer — deferred-mux decrypts directly); an unresolved disc
+            // persists only the VID (the retry marker, so a future mux can
+            // re-ask the key service). Never both.
+            use std::fmt::Write as _;
+            if !self.unit_keys.is_empty() {
+                for (cps, key) in &self.unit_keys {
+                    let mut hex = String::with_capacity(32);
+                    for b in key {
+                        let _ = write!(hex, "{b:02x}");
+                    }
+                    writeln!(w, "# freemkv-uk: {cps}:{hex}")?;
+                }
+            } else if let Some(vid) = self.vid {
+                let mut hex = String::with_capacity(32);
+                for b in vid {
+                    let _ = write!(hex, "{b:02x}");
+                }
+                writeln!(w, "# freemkv-vid: {hex}")?;
+            }
             writeln!(w, "# Current pos / status / pass / pass_time")?;
             writeln!(w, "0x000000000  ?  1  0")?;
             writeln!(w, "#      pos        size  status")?;
@@ -336,6 +498,41 @@ impl Mapfile {
     }
 }
 
+impl Drop for Mapfile {
+    /// Best-effort flush on drop so a sweep / patch that returns early
+    /// (or unwinds) doesn't lose its in-memory state. Errors here are
+    /// swallowed because Drop has no way to surface them; explicit
+    /// `flush()` on the success path gives callers proper error handling.
+    fn drop(&mut self) {
+        let _ = self.flush();
+    }
+}
+
+/// Parse a 32-char lowercase/uppercase hex string into a 16-byte VID.
+/// Returns `None` on any malformation (wrong length, non-hex) — the
+/// caller treats a bad VID comment as simply absent rather than an
+/// error, so a corrupt header never fails a mapfile load.
+fn parse_vid_hex(s: &str) -> Option<[u8; 16]> {
+    let s = s.strip_prefix("0x").unwrap_or(s);
+    if s.len() != 32 {
+        return None;
+    }
+    let mut out = [0u8; 16];
+    for (i, b) in out.iter_mut().enumerate() {
+        *b = u8::from_str_radix(&s[i * 2..i * 2 + 2], 16).ok()?;
+    }
+    Some(out)
+}
+
+/// Parse a `# freemkv-uk:` value `<cps>:<32hex>` into `(cps_unit, key)`. Returns
+/// `None` on any malformation so a corrupt line is ignored, never fatal.
+fn parse_uk_line(s: &str) -> Option<(u32, [u8; 16])> {
+    let (cps, hex) = s.split_once(':')?;
+    let cps: u32 = cps.trim().parse().ok()?;
+    let key = parse_vid_hex(hex.trim())?; // 32-hex → [u8; 16], shared parser
+    Some((cps, key))
+}
+
 fn parse_hex(s: &str) -> io::Result<u64> {
     let s = s.strip_prefix("0x").unwrap_or(s);
     u64::from_str_radix(s, 16).map_err(|_| {
@@ -436,6 +633,8 @@ mod tests {
         let mut mf = Mapfile::create(&p, 1000, "test").unwrap();
         mf.record(100, 200, SectorStatus::Finished).unwrap();
         mf.record(500, 100, SectorStatus::Unreadable).unwrap();
+        // record() batches; explicit flush before reading back from disk.
+        mf.flush().unwrap();
         let loaded = Mapfile::load(&p).unwrap();
         assert_eq!(loaded.entries(), mf.entries());
         let _ = std::fs::remove_file(&p);
@@ -467,4 +666,193 @@ mod tests {
         assert_eq!(bad, vec![(100, 50), (300, 50)]);
         let _ = std::fs::remove_file(&p);
     }
+
+    #[test]
+    fn stats_consistent_after_overlapping_records() {
+        let p = tmpfile("stats_consistent_after_overlapping");
+        let _ = std::fs::remove_file(&p);
+        let mut mf = Mapfile::create(&p, 1000, "test").unwrap();
+        // Record some finished, some unreadable, some nontrimmed
+        mf.record(0, 300, SectorStatus::Finished).unwrap();
+        mf.record(300, 200, SectorStatus::NonTrimmed).unwrap();
+        mf.record(500, 100, SectorStatus::Unreadable).unwrap();
+        mf.record(600, 400, SectorStatus::Finished).unwrap();
+
+        // Final entries: [0..300 Finished, 300..500 NonTrimmed, 500..600 Unreadable, 600..1000 Finished]
+        let s = mf.stats();
+        assert_eq!(s.bytes_good, 700); // 300 + 400
+        assert_eq!(s.bytes_unreadable, 100); // 100
+        assert_eq!(s.bytes_pending, 200); // NonTrimmed only (NonTried=0)
+        assert_eq!(s.bytes_nontried, 0);
+        assert_eq!(s.bytes_retryable, 200); // NonTrimmed
+        assert_eq!(s.bytes_total, 1000);
+
+        // Overwrite a NonTrimmed range with Finished
+        mf.record(300, 100, SectorStatus::Finished).unwrap();
+        // Entries: [0..400 Finished, 400..500 NonTrimmed, 500..600 Unreadable, 600..1000 Finished]
+        let s2 = mf.stats();
+        assert_eq!(s2.bytes_good, 800); // 400 + 400
+        assert_eq!(s2.bytes_unreadable, 100);
+        assert_eq!(s2.bytes_pending, 100); // NonTrimmed only
+        assert_eq!(s2.bytes_retryable, 100);
+
+        let _ = std::fs::remove_file(&p);
+    }
+
+    #[test]
+    fn unit_keys_round_trip_and_are_mutually_exclusive_with_vid() {
+        let p = tmpfile("uk_round_trips");
+        let _ = std::fs::remove_file(&p);
+        let mut mf = Mapfile::create(&p, 1000, "test").unwrap();
+        mf.record(0, 500, SectorStatus::Finished).unwrap();
+        // Set a VID first, then unit keys: keys must WIN and clear the VID.
+        mf.set_vid([0xAA; 16]);
+        let keys: Vec<(u32, [u8; 16])> = vec![
+            (
+                0,
+                [
+                    0x57, 0x60, 0xcc, 0x83, 0x3d, 0x86, 0x0e, 0x48, 0x92, 0x1f, 0x88, 0x16, 0xe1,
+                    0x35, 0x9b, 0xad,
+                ],
+            ),
+            (1, [0x11; 16]),
+        ];
+        mf.set_unit_keys(&keys);
+        assert_eq!(
+            mf.vid(),
+            None,
+            "set_unit_keys must clear vid (keys XOR vid)"
+        );
+        mf.flush().unwrap();
+
+        let text = std::fs::read_to_string(&p).unwrap();
+        assert!(
+            text.contains("# freemkv-uk: 0:5760cc833d860e48921f8816e1359bad"),
+            "uk comment format mismatch: {text}"
+        );
+        assert!(
+            text.contains("# freemkv-uk: 1:11111111111111111111111111111111"),
+            "second uk missing: {text}"
+        );
+        assert!(
+            !text.contains("# freemkv-vid:"),
+            "VID must NOT be written when keys are present: {text}"
+        );
+
+        // load() recovers the unit keys (and no VID).
+        let loaded = Mapfile::load(&p).unwrap();
+        assert_eq!(loaded.unit_keys(), keys.as_slice());
+        assert_eq!(loaded.vid(), None);
+        assert_eq!(loaded.entries(), mf.entries());
+
+        // VID-only path (no keys) still persists the VID as the retry marker.
+        let p2 = tmpfile("uk_vid_only");
+        let _ = std::fs::remove_file(&p2);
+        let mut mf2 = Mapfile::create(&p2, 1000, "test").unwrap();
+        mf2.set_vid([0xBB; 16]);
+        mf2.flush().unwrap();
+        let loaded2 = Mapfile::load(&p2).unwrap();
+        assert_eq!(loaded2.vid(), Some([0xBB; 16]));
+        assert!(loaded2.unit_keys().is_empty());
+        let _ = std::fs::remove_file(&p);
+        let _ = std::fs::remove_file(&p2);
+    }
+
+    #[test]
+    fn vid_round_trips_and_data_lines_unaffected() {
+        let p = tmpfile("vid_round_trips");
+        let _ = std::fs::remove_file(&p);
+
+        // Build a mapfile with some data ranges, set a VID, persist.
+        let mut mf = Mapfile::create(&p, 1000, "test").unwrap();
+        mf.record(100, 200, SectorStatus::Finished).unwrap();
+        mf.record(500, 100, SectorStatus::Unreadable).unwrap();
+        mf.record(700, 50, SectorStatus::NonTrimmed).unwrap();
+        let vid: [u8; 16] = [
+            0x00, 0x11, 0x22, 0x33, 0x44, 0x55, 0x66, 0x77, 0x88, 0x99, 0xaa, 0xbb, 0xcc, 0xdd,
+            0xee, 0xff,
+        ];
+        mf.set_vid(vid);
+        mf.flush().unwrap();
+
+        // The saved file must contain the VID comment in lowercase hex.
+        let text = std::fs::read_to_string(&p).unwrap();
+        assert!(
+            text.contains("# freemkv-vid:"),
+            "saved mapfile missing VID comment: {text}"
+        );
+        assert!(
+            text.contains("# freemkv-vid: 00112233445566778899aabbccddeeff"),
+            "VID comment format mismatch: {text}"
+        );
+
+        // load() recovers the VID and the identical data ranges.
+        let loaded = Mapfile::load(&p).unwrap();
+        assert_eq!(loaded.vid(), Some(vid));
+        assert_eq!(loaded.entries(), mf.entries());
+
+        // A mapfile WITHOUT the VID comment must parse the same +/-/?
+        // data ranges as the one WITH it (comment ignored by parser).
+        let p2 = tmpfile("vid_round_trips_novid");
+        let _ = std::fs::remove_file(&p2);
+        let mut mf2 = Mapfile::create(&p2, 1000, "test").unwrap();
+        mf2.record(100, 200, SectorStatus::Finished).unwrap();
+        mf2.record(500, 100, SectorStatus::Unreadable).unwrap();
+        mf2.record(700, 50, SectorStatus::NonTrimmed).unwrap();
+        mf2.flush().unwrap();
+        let loaded_novid = Mapfile::load(&p2).unwrap();
+        assert_eq!(loaded_novid.vid(), None);
+        assert_eq!(loaded_novid.entries(), loaded.entries());
+
+        // Malformed VID comments must not error the load (treated absent).
+        let mut bad = text.replace("00112233445566778899aabbccddeeff", "zzzz");
+        let pbad = tmpfile("vid_round_trips_bad");
+        let _ = std::fs::remove_file(&pbad);
+        std::fs::write(&pbad, &bad).unwrap();
+        let loaded_bad = Mapfile::load(&pbad).unwrap();
+        assert_eq!(loaded_bad.vid(), None);
+        assert_eq!(loaded_bad.entries(), loaded.entries());
+
+        // A load->save cycle preserves the VID (the patch-pass path).
+        bad.clear();
+        let resaved = tmpfile("vid_round_trips_resave");
+        let _ = std::fs::remove_file(&resaved);
+        let mut reloaded = Mapfile::load(&p).unwrap();
+        // Repoint at a fresh path and flush; mark dirty via a no-op record.
+        reloaded.path = resaved.clone();
+        reloaded.dirty = true;
+        reloaded.flush().unwrap();
+        let again = Mapfile::load(&resaved).unwrap();
+        assert_eq!(again.vid(), Some(vid));
+
+        let _ = std::fs::remove_file(&p);
+        let _ = std::fs::remove_file(&p2);
+        let _ = std::fs::remove_file(&pbad);
+        let _ = std::fs::remove_file(&resaved);
+    }
+
+    #[test]
+    fn stats_consistent_after_split_record() {
+        let p = tmpfile("stats_consistent_after_split");
+        let _ = std::fs::remove_file(&p);
+        let mut mf = Mapfile::create(&p, 1000, "test").unwrap();
+        // Mark middle as NonTrimmed
+        mf.record(200, 400, SectorStatus::NonTrimmed).unwrap();
+        // Entries: [0..200 NonTried, 200..600 NonTrimmed, 600..1000 NonTried]
+        let s = mf.stats();
+        assert_eq!(s.bytes_pending, 1000); // NonTried(600) + NonTrimmed(400)
+        assert_eq!(s.bytes_retryable, 400); // NonTrimmed only
+        assert_eq!(s.bytes_nontried, 600); // 200 + 400
+
+        // Overwrite the NonTrimmed with Finished (splitting the remaining NonTried)
+        mf.record(200, 400, SectorStatus::Finished).unwrap();
+        // Entries: [0..200 NonTried, 200..600 Finished, 600..1000 NonTried]
+        let s2 = mf.stats();
+        assert_eq!(s2.bytes_good, 400);
+        assert_eq!(s2.bytes_pending, 600); // NonTried(200 + 400)
+        assert_eq!(s2.bytes_nontried, 600);
+        assert_eq!(s2.bytes_retryable, 0);
+
+        let _ = std::fs::remove_file(&p);
+    }
 }

src/disc/sweep.rs

@@ -0,0 +1,239 @@
+//! `Disc::sweep`'s consumer-side `Sink<WorkItem>`.
+//!
+//! Background: the original sweep loop runs strictly serialised —
+//! SCSI read → decrypt → seek + write → mapfile.record → next iter.
+//! On a healthy disc the SCSI read costs ~5-12 ms per 64 KB batch and
+//! the post-read work (decrypt 1-3 ms + file write + mapfile fsync
+//! 5-15 ms) adds another batch's worth of latency. The drive idles
+//! during the post-read work; throughput tops out at the *sum* of
+//! both costs.
+//!
+//! 0.17.11 introduced a bespoke producer/consumer split (the now-
+//! removed `disc/sweep_pipeline.rs`) to overlap the two stages. 0.18
+//! collapses that split — together with the analogous splits patch
+//! and mux need — onto the generic [`crate::io::Pipeline`] +
+//! [`crate::io::Sink`] primitive. This module is the sweep-specific
+//! `Sink` impl; the producer-side state machine (read_error context,
+//! decrypt, set_speed, halt) stays in `Disc::sweep` in `disc/mod.rs`.
+//!
+//! Correctness invariants preserved (same as 0.17.11):
+//! - Mapfile is single-writer (consumer-only). No locking.
+//! - All `read_error::ReadCtx` state stays on the producer thread.
+//! - `set_speed` calls happen on the producer thread (same thread that
+//!   owns the `SectorSource`). No new SCSI concurrency.
+//! - Per-iteration ordering of file-write → mapfile-record is kept
+//!   intact in the consumer (write before record), so the on-disk
+//!   invariant "mapfile only marks Finished what the file has
+//!   received" survives a crash mid-pass.
+//! - The BU40N+Initio bridge wedge concern is unchanged: only one
+//!   SCSI command in flight at a time, error-path timing identical,
+//!   no new retry logic.
+
+use std::io::{Seek, SeekFrom, Write};
+use std::sync::mpsc::{Receiver, SyncSender, sync_channel};
+
+use crate::error::Error;
+use crate::io::{Flow, Sink};
+
+use super::mapfile::{MapStats, Mapfile, SectorStatus};
+
+/// Reusable zero buffer for SkipFill / GapFill / BisectBad. 64 KB
+/// matches the existing zero_gap chunk size used by the pre-split
+/// sweep loop.
+const ZERO_CHUNK: usize = 65 * 1024;
+
+/// Producer → Consumer messages. The consumer applies these in FIFO
+/// order; ordering of file writes and mapfile records across items is
+/// preserved.
+pub(super) enum WorkItem {
+    /// Successful batch read. Producer has already decrypted `buf` if
+    /// `opts.decrypt` was set. Consumer writes `buf` at `pos` and
+    /// records the range as `Finished`.
+    Good { pos: u64, buf: Vec<u8> },
+
+    /// Bisect inner-loop good single sector (already decrypted by the
+    /// producer). 2048 bytes.
+    BisectGood { pos: u64, buf: Box<[u8; 2048]> },
+
+    /// Bisect inner-loop bad single sector. Consumer writes 2048
+    /// zeros at `pos` and records the sector as `NonTrimmed`.
+    BisectBad { pos: u64 },
+
+    /// Whole-batch zero-fill (failed batch on `SkipBlock`, or the
+    /// failed batch portion of `JumpAhead`). Consumer streams zeros
+    /// across `[pos, pos+len)` and records the range as `NonTrimmed`.
+    SkipFill { pos: u64, len: u64 },
+
+    /// Gap fill following a `JumpAhead`. Same effect as `SkipFill`;
+    /// distinguished only so future logging / instrumentation can
+    /// tell them apart without parsing a flag.
+    GapFill { pos: u64, len: u64 },
+
+    /// Producer wants the latest mapfile stats for the progress
+    /// callback. Consumer responds on `prog_tx` with a fresh
+    /// [`ProgressSnapshot`]. Best-effort: if the producer hasn't
+    /// drained the previous snapshot, the new one is silently
+    /// dropped — the producer's local cache stays current enough.
+    StatsRequest,
+}
+
+/// Snapshot the consumer sends back to the producer for the progress
+/// callback.
+pub(super) struct ProgressSnapshot {
+    pub stats: MapStats,
+    pub bad_ranges: Vec<(u64, u64)>,
+}
+
+/// Final summary returned by the consumer thread on shutdown — what
+/// `SweepSink::close` produces, surfaced to the producer via
+/// `Pipeline::finish`.
+pub(super) struct ConsumerSummary {
+    pub stats: MapStats,
+}
+
+/// Drain any pending progress snapshots from the consumer. Returns
+/// the most recent one, if any. The producer caches it and uses it
+/// for subsequent progress callbacks until a fresh one arrives.
+pub(super) fn try_recv_progress(rx: &Receiver<ProgressSnapshot>) -> Option<ProgressSnapshot> {
+    let mut latest = None;
+    while let Ok(snap) = rx.try_recv() {
+        latest = Some(snap);
+    }
+    latest
+}
+
+/// `Sink<WorkItem>` for sweep. Owns the writeback file + mapfile +
+/// progress back-channel. `apply` carries the file-write +
+/// mapfile.record per item; `close` drains the writeback pipeline,
+/// fsyncs the ISO, and flushes the mapfile.
+pub(super) struct SweepSink {
+    file: crate::io::WritebackFile,
+    map: Mapfile,
+    /// `sync_all`-on-failure-is-an-error iff the output is a regular
+    /// file. `/dev/null` and pipes always fail `sync_all`; that's not
+    /// a real error.
+    is_regular: bool,
+    /// Back-channel for `StatsRequest` responses. The producer caches
+    /// the latest snapshot and uses it for the progress callback;
+    /// dropped sends on a full channel are by design.
+    prog_tx: SyncSender<ProgressSnapshot>,
+    /// Reusable zero buffer for SkipFill / GapFill / BisectBad. Held
+    /// in the sink so each apply call doesn't reallocate.
+    zero: Box<[u8; ZERO_CHUNK]>,
+}
+
+impl SweepSink {
+    /// Construct a new `SweepSink` plus the matching progress
+    /// receiver. Channel depth on the back-channel is `1` — the
+    /// producer's cache is the source of truth between snapshots.
+    pub(super) fn new(
+        file: crate::io::WritebackFile,
+        map: Mapfile,
+        is_regular: bool,
+    ) -> (Self, Receiver<ProgressSnapshot>) {
+        let (prog_tx, prog_rx) = sync_channel::<ProgressSnapshot>(1);
+        let sink = SweepSink {
+            file,
+            map,
+            is_regular,
+            prog_tx,
+            zero: Box::new([0u8; ZERO_CHUNK]),
+        };
+        (sink, prog_rx)
+    }
+}
+
+impl Sink<WorkItem> for SweepSink {
+    type Output = ConsumerSummary;
+
+    fn apply(&mut self, item: WorkItem) -> Result<Flow, Error> {
+        match item {
+            WorkItem::Good { pos, buf } => {
+                // Decrypt is on the producer; consumer assumes plaintext.
+                let len = buf.len() as u64;
+                self.file
+                    .seek(SeekFrom::Start(pos))
+                    .map_err(|e| Error::IoError { source: e })?;
+                self.file
+                    .write_all(&buf)
+                    .map_err(|e| Error::IoError { source: e })?;
+                self.map
+                    .record(pos, len, SectorStatus::Finished)
+                    .map_err(|e| Error::IoError { source: e })?;
+            }
+            WorkItem::BisectGood { pos, buf } => {
+                self.file
+                    .seek(SeekFrom::Start(pos))
+                    .map_err(|e| Error::IoError { source: e })?;
+                self.file
+                    .write_all(&buf[..])
+                    .map_err(|e| Error::IoError { source: e })?;
+                self.map
+                    .record(pos, 2048, SectorStatus::Finished)
+                    .map_err(|e| Error::IoError { source: e })?;
+            }
+            WorkItem::BisectBad { pos } => {
+                self.file
+                    .seek(SeekFrom::Start(pos))
+                    .map_err(|e| Error::IoError { source: e })?;
+                self.file
+                    .write_all(&self.zero[..2048])
+                    .map_err(|e| Error::IoError { source: e })?;
+                self.map
+                    .record(pos, 2048, SectorStatus::NonTrimmed)
+                    .map_err(|e| Error::IoError { source: e })?;
+            }
+            WorkItem::SkipFill { pos, len } | WorkItem::GapFill { pos, len } => {
+                self.file
+                    .seek(SeekFrom::Start(pos))
+                    .map_err(|e| Error::IoError { source: e })?;
+                // Subsequent writes are sequential; `WritebackFile`'s
+                // seek-elision keeps them on the writeback pipeline path.
+                let mut filled = 0u64;
+                while filled < len {
+                    let chunk = (len - filled).min(self.zero.len() as u64) as usize;
+                    self.file
+                        .write_all(&self.zero[..chunk])
+                        .map_err(|e| Error::IoError { source: e })?;
+                    filled += chunk as u64;
+                }
+                self.map
+                    .record(pos, len, SectorStatus::NonTrimmed)
+                    .map_err(|e| Error::IoError { source: e })?;
+            }
+            WorkItem::StatsRequest => {
+                let stats = self.map.stats();
+                let bad_ranges = self.map.ranges_with(&[
+                    SectorStatus::NonTrimmed,
+                    SectorStatus::Unreadable,
+                    SectorStatus::NonScraped,
+                    SectorStatus::NonTried,
+                ]);
+                // Best-effort: drop on backpressure; producer's cache
+                // stays current enough.
+                let _ = self
+                    .prog_tx
+                    .try_send(ProgressSnapshot { stats, bad_ranges });
+            }
+        }
+        Ok(Flow::Continue)
+    }
+
+    fn close(mut self) -> Result<Self::Output, Error> {
+        // Drain the writeback pipeline + fsync the ISO, then persist
+        // any pending mapfile state. Same finalisation order as the
+        // pre-Pipeline consumer loop.
+        if let Err(e) = self.file.sync_all() {
+            if self.is_regular {
+                return Err(Error::IoError { source: e });
+            }
+            // Non-regular outputs (/dev/null, pipes) always fail
+            // sync_all; that's not a real error.
+        }
+        self.map.flush().map_err(|e| Error::IoError { source: e })?;
+
+        Ok(ConsumerSummary {
+            stats: self.map.stats(),
+        })
+    }
+}

src/drive/mod.rs

@@ -29,7 +29,7 @@ use crate::platform::PlatformDriver;
 use crate::platform::mt1959::Mt1959;
 use crate::profile::{self, DriveProfile};
 use crate::scsi::ScsiTransport;
-use crate::sector::SectorReader;
+use crate::sector::SectorSource;
 use std::path::Path;
 use std::sync::Arc;
 use std::sync::atomic::{AtomicBool, Ordering};
@@ -69,6 +69,16 @@ pub struct Drive {
     halt: Arc<AtomicBool>,
     /// Event handler — fires for read errors and library-level state changes.
     event_fn: Option<Box<dyn Fn(Event) + Send>>,
+    /// Linux only: raw fd for the corresponding block device (`/dev/sr*`)
+    /// used as a recovery fallback when SCSI READ via `/dev/sg*` returns
+    /// an error. The kernel `sr_mod` driver auto-retries failed reads
+    /// (~5× per command) — historically the reason `dd if=/dev/sr0`
+    /// recovers ~50% of bad sectors that single-shot `SG_IO` READ
+    /// misses on the same drive. `None` when the block device couldn't
+    /// be resolved or opened (no fallback in that case; SCSI read
+    /// errors propagate as before).
+    #[cfg(target_os = "linux")]
+    block_dev_fd: Option<std::os::unix::io::RawFd>,
 }
 
 impl Drive {
@@ -87,6 +97,9 @@ impl Drive {
             None => (None, None, None),
         };
 
+        #[cfg(target_os = "linux")]
+        let block_dev_fd = open_block_device_for_sg(device);
+
         Ok(Drive {
             scsi: transport,
             driver,
@@ -96,6 +109,8 @@ impl Drive {
             device_path: device.to_string_lossy().to_string(),
             halt: Arc::new(AtomicBool::new(false)),
             event_fn: None,
+            #[cfg(target_os = "linux")]
+            block_dev_fd,
         })
     }
 
@@ -169,6 +184,13 @@ impl Drive {
         self.profile.is_some()
     }
 
+    /// Borrow the matched drive profile, if any. Used by callers that
+    /// need to issue per-drive OEM CDB templates (e.g. the OEM VID
+    /// retrieval path in `disc::encrypt`).
+    pub fn drive_profile(&self) -> Option<&DriveProfile> {
+        self.profile.as_ref()
+    }
+
     /// Access the SCSI transport for direct commands (used by CSS/AACS auth).
     pub fn scsi_mut(&mut self) -> &mut dyn ScsiTransport {
         self.scsi.as_mut()
@@ -417,6 +439,27 @@ impl Drive {
         }
     }
 
+    /// True if the drive is currently in the extended-access state.
+    ///
+    /// Detected by the platform driver during `init()` from the unlock
+    /// response's mode markers. When true:
+    ///   - SCSI READ_10 returns plaintext sectors (no AACS bus
+    ///     encryption applied)
+    ///   - VID retrieval works via the per-drive OEM CDB in
+    ///     [`DriveProfile`] without the cert-based AACS handshake
+    ///   - Disc-side Host Revocation List enforcement is effectively
+    ///     bypassed by the alternate data path
+    ///
+    /// AACS layer code branches on this: if true, issue the OEM
+    /// `read_vid_cdb` to retrieve VID directly; if false, fall back
+    /// to the cert-based mutual-auth handshake.
+    pub fn is_unlocked(&self) -> bool {
+        match self.driver {
+            Some(ref d) => d.is_unlocked(),
+            None => false,
+        }
+    }
+
     /// Read sectors from the disc. Single-shot — no inline retries, no
     /// SCSI reset.
     ///
@@ -483,6 +526,54 @@ impl Drive {
                     scsi_status = status,
                     "Drive::read checked_exec failed"
                 );
+
+                // /dev/sr0 pread fallback (Linux only). The kernel
+                // sr_mod driver auto-retries failed reads (~5× per
+                // command). Empirically (BU40N + a UHD disc,
+                // 2026-05-08) dd via /dev/sr0 recovers ~50% of bad
+                // sectors that a single-shot SG_IO READ misses.
+                #[cfg(target_os = "linux")]
+                if recovery {
+                    if let Some(fd) = self.block_dev_fd {
+                        let len = count as usize * 2048;
+                        if buf.len() >= len {
+                            let offset = lba as i64 * 2048;
+                            // Drop kernel cache for this region so we get
+                            // a fresh device read, not stale page-cache
+                            // data from a prior successful neighbour read.
+                            let _ = unsafe {
+                                libc::posix_fadvise(
+                                    fd,
+                                    offset,
+                                    len as i64,
+                                    libc::POSIX_FADV_DONTNEED,
+                                )
+                            };
+                            let n = unsafe {
+                                libc::pread(fd, buf.as_mut_ptr() as *mut libc::c_void, len, offset)
+                            };
+                            if n == len as isize {
+                                tracing::info!(
+                                    target: "freemkv::drive",
+                                    lba,
+                                    count,
+                                    bytes = len,
+                                    "Drive::read recovered via /dev/sr0 pread fallback"
+                                );
+                                return Ok(len);
+                            }
+                            tracing::debug!(
+                                target: "freemkv::drive",
+                                lba,
+                                count,
+                                pread_ret = n as i64,
+                                errno = std::io::Error::last_os_error().raw_os_error().unwrap_or(0),
+                                "/dev/sr0 pread fallback also failed"
+                            );
+                        }
+                    }
+                }
+
                 Err(Error::DiscRead {
                     sector: lba as u64,
                     status: Some(status),
@@ -586,10 +677,65 @@ impl Drop for Drive {
     fn drop(&mut self) {
         self.cleanup();
         // SgIoTransport::drop() runs next, calling libc::close(fd)
+        #[cfg(target_os = "linux")]
+        if let Some(fd) = self.block_dev_fd.take() {
+            unsafe { libc::close(fd) };
+        }
     }
 }
 
-impl SectorReader for Drive {
+/// Resolve a `/dev/sg*` path to the corresponding `/dev/sr*` block
+/// device by walking sysfs, then open it for read (no `O_DIRECT` —
+/// `posix_fadvise(POSIX_FADV_DONTNEED)` flushes the cache before each
+/// pread, which avoids buffer-alignment requirements while still
+/// forcing fresh device reads).
+///
+/// Returns `None` on any error (sysfs not present, no matching block
+/// device, open failed). Callers treat that as "no fallback available"
+/// and propagate the original SCSI READ error.
+#[cfg(target_os = "linux")]
+fn open_block_device_for_sg(sg_path: &Path) -> Option<std::os::unix::io::RawFd> {
+    let basename = sg_path.file_name()?.to_str()?;
+    if !basename.starts_with("sg") {
+        return None;
+    }
+    let sysfs_dir = format!("/sys/class/scsi_generic/{}/device/block", basename);
+    let entries = std::fs::read_dir(&sysfs_dir).ok()?;
+    let block_name = entries
+        .flatten()
+        .find_map(|e| e.file_name().into_string().ok())?;
+    let block_path = format!("/dev/{}", block_name);
+
+    let mut bytes = block_path.as_bytes().to_vec();
+    bytes.push(0);
+    let fd = unsafe {
+        libc::open(
+            bytes.as_ptr() as *const libc::c_char,
+            libc::O_RDONLY | libc::O_CLOEXEC,
+        )
+    };
+    if fd < 0 {
+        tracing::debug!(
+            target: "freemkv::drive",
+            sg = basename,
+            block_path,
+            errno = std::io::Error::last_os_error().raw_os_error().unwrap_or(0),
+            "Failed to open block device for fallback; sr0 fallback disabled"
+        );
+        None
+    } else {
+        tracing::info!(
+            target: "freemkv::drive",
+            sg = basename,
+            block_path,
+            fd,
+            "Opened /dev/sr* as recovery fallback for failed SCSI reads"
+        );
+        Some(fd)
+    }
+}
+
+impl SectorSource for Drive {
     fn read_sectors(
         &mut self,
         lba: u32,

src/drm/mod.rs

@@ -0,0 +1,289 @@
+//! Top-level DRM scheme dispatch.
+//!
+//! Four content-protection schemes ride through a single
+//! detect-then-load pipeline:
+//!
+//! | Scheme              | Discriminator                                  |
+//! |---------------------|------------------------------------------------|
+//! | [`DrmScheme::Css`]  | DVD probe sector flagged scrambled             |
+//! | [`DrmScheme::Aacs10`] | Content cert type byte `0x00`                |
+//! | [`DrmScheme::Aacs20`] | Content cert type byte `!= 0x00`, no Variant |
+//! | [`DrmScheme::Aacs21`] | Content cert + MKB records `0x82` / `0x83`   |
+//!
+//! Detection happens from a [`DrmProbe`] (raw inputs the caller has
+//! already extracted from the disc); resolution runs through a
+//! [`DrmContext`] (the full set of inputs the loaders need).
+//!
+//! The AACS 2.1 arm is wired but disabled. The dispatcher leaves
+//! [`crate::aacs::resolve_keys_v21`] reachable as a library entry point
+//! for fixture-driven validation, but production consumers go through
+//! [`DrmScheme::load`], which short-circuits V21 to `None` until the
+//! Variant chain has a real Variant-scheme disc to validate against.
+
+use crate::aacs;
+use crate::css;
+
+/// Which content-protection scheme governs a disc.
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub enum DrmScheme {
+    /// DVD Content Scramble System.
+    Css,
+    /// AACS 1.0 — original BD-ROM.
+    Aacs10,
+    /// AACS 2.0 — UHD-BD, classical Media Key chain.
+    Aacs20,
+    /// AACS 2.1 — UHD-BD with Media Key Variant chain.
+    Aacs21,
+}
+
+/// Inputs to [`DrmScheme::detect`]. All borrows — caller retains
+/// ownership.
+pub struct DrmProbe<'a> {
+    /// 2048-byte sample sector from inside a DVD title's extents. Used
+    /// only for CSS scramble-flag detection. `None` for non-DVD discs.
+    pub dvd_sample_sector: Option<&'a [u8]>,
+    /// Content Certificate file bytes (typically `/AACS/Content000.cer`).
+    /// `None` when the disc has no AACS directory.
+    pub content_cert: Option<&'a [u8]>,
+    /// MKB file bytes (typically `/AACS/MKB_RW.inf`). Required to
+    /// distinguish AACS 2.0 from AACS 2.1.
+    pub mkb: Option<&'a [u8]>,
+}
+
+/// Inputs to [`DrmScheme::load`]. Carries everything needed by either
+/// the AACS or CSS loader.
+pub struct DrmContext<'a> {
+    /// AACS resolver inputs — required when the scheme is any AACS
+    /// variant.
+    pub aacs: Option<aacs::ResolveContext<'a>>,
+    /// CSS resolver inputs — required when the scheme is [`DrmScheme::Css`].
+    pub css: Option<css::CssContext<'a>>,
+}
+
+/// Resolved key material, tagged by scheme.
+#[derive(Debug)]
+pub enum ResolvedScheme {
+    Css(css::CssState),
+    Aacs(aacs::ResolvedKeys),
+}
+
+impl DrmScheme {
+    /// Detect which DRM scheme protects the disc described by `probe`.
+    ///
+    /// Returns `None` for unencrypted media. The order is intentional:
+    /// CSS is checked first (DVD-format probe), then AACS (Blu-ray
+    /// format).
+    pub fn detect(probe: &DrmProbe<'_>) -> Option<DrmScheme> {
+        // CSS — DVD probe sector carries the scramble flag.
+        if let Some(sector) = probe.dvd_sample_sector {
+            if css::is_scrambled(sector) {
+                return Some(DrmScheme::Css);
+            }
+        }
+
+        // AACS — content cert type byte distinguishes V10 from V20+.
+        // V21 promotion requires MKB Variant records.
+        let cc = probe.content_cert.and_then(aacs::parse_content_cert)?;
+        match cc.version {
+            aacs::AacsVersion::V10 => Some(DrmScheme::Aacs10),
+            aacs::AacsVersion::V20 | aacs::AacsVersion::V21 => {
+                if let Some(mkb) = probe.mkb {
+                    let recs = aacs::variants::walk_mkb(mkb);
+                    if aacs::variants::is_variant_mkb(&recs) {
+                        return Some(DrmScheme::Aacs21);
+                    }
+                }
+                Some(DrmScheme::Aacs20)
+            }
+        }
+    }
+
+    /// Run key resolution for this scheme against `ctx`.
+    ///
+    /// Returns `None` when the scheme's resolver could not produce keys
+    /// (missing context, KEYDB miss, failed crypto walk, etc.) or when
+    /// the scheme itself is gated off (see the inline comment on the
+    /// `Aacs21` arm).
+    pub fn load(self, ctx: &mut DrmContext<'_>) -> Option<ResolvedScheme> {
+        match self {
+            DrmScheme::Css => ctx
+                .css
+                .as_mut()
+                .and_then(css::resolve)
+                .map(ResolvedScheme::Css),
+            DrmScheme::Aacs10 => ctx
+                .aacs
+                .as_ref()
+                .and_then(aacs::resolve_keys_v1)
+                .map(ResolvedScheme::Aacs),
+            DrmScheme::Aacs20 => ctx
+                .aacs
+                .as_ref()
+                .and_then(aacs::resolve_keys_v2)
+                .map(ResolvedScheme::Aacs),
+            // AACS 2.1 derivation is wired but disabled. KCD validation
+            // against a Variant-scheme disc is pending. To enable,
+            // uncomment the line below.
+            // DrmScheme::Aacs21 => ctx
+            //     .aacs
+            //     .as_ref()
+            //     .and_then(aacs::resolve_keys_v21)
+            //     .map(ResolvedScheme::Aacs),
+            DrmScheme::Aacs21 => None,
+        }
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    // Build a minimal cert: type byte + bus-encryption byte + 6 zero
+    // cc_id bytes.
+    fn cert(type_byte: u8) -> Vec<u8> {
+        let mut v = vec![0u8; 8];
+        v[0] = type_byte;
+        v
+    }
+
+    // Synthetic AACS 2.x MKB with no Variant records.
+    fn mkb_classical() -> Vec<u8> {
+        vec![
+            0x10, 0x00, 0x00, 0x0C, 0x48, 0x14, 0x10, 0x03, 0x00, 0x00, 0x00, 0x4D,
+        ]
+    }
+
+    // Synthetic AACS 2.x MKB with a 0x82 + 0x83 record pair.
+    fn mkb_with_variant() -> Vec<u8> {
+        let mut m = mkb_classical();
+        m.extend_from_slice(&[0x82, 0x00, 0x00, 0x14]);
+        m.extend_from_slice(&[0xEE; 16]);
+        m.extend_from_slice(&[0x83, 0x00, 0x00, 0x14]);
+        m.extend_from_slice(&[0x55; 16]);
+        m
+    }
+
+    // Synthetic scrambled DVD sector — byte 0x14 carries the CSS
+    // scramble flag in bits 4-5.
+    fn scrambled_dvd_sector() -> Vec<u8> {
+        let mut s = vec![0u8; 2048];
+        s[0x14] = 0x30;
+        s
+    }
+
+    #[test]
+    fn detect_returns_none_for_unencrypted() {
+        let probe = DrmProbe {
+            dvd_sample_sector: None,
+            content_cert: None,
+            mkb: None,
+        };
+        assert_eq!(DrmScheme::detect(&probe), None);
+    }
+
+    #[test]
+    fn detect_returns_css_for_scrambled_dvd() {
+        let sector = scrambled_dvd_sector();
+        let probe = DrmProbe {
+            dvd_sample_sector: Some(&sector),
+            content_cert: None,
+            mkb: None,
+        };
+        assert_eq!(DrmScheme::detect(&probe), Some(DrmScheme::Css));
+    }
+
+    #[test]
+    fn detect_returns_aacs10_for_type0_cert() {
+        let c = cert(0x00);
+        let probe = DrmProbe {
+            dvd_sample_sector: None,
+            content_cert: Some(&c),
+            mkb: None,
+        };
+        assert_eq!(DrmScheme::detect(&probe), Some(DrmScheme::Aacs10));
+    }
+
+    #[test]
+    fn detect_returns_aacs20_for_type1_cert_no_variant() {
+        let c = cert(0x01);
+        let mkb = mkb_classical();
+        let probe = DrmProbe {
+            dvd_sample_sector: None,
+            content_cert: Some(&c),
+            mkb: Some(&mkb),
+        };
+        assert_eq!(DrmScheme::detect(&probe), Some(DrmScheme::Aacs20));
+    }
+
+    #[test]
+    fn detect_returns_aacs21_for_type1_cert_with_variant() {
+        let c = cert(0x01);
+        let mkb = mkb_with_variant();
+        let probe = DrmProbe {
+            dvd_sample_sector: None,
+            content_cert: Some(&c),
+            mkb: Some(&mkb),
+        };
+        assert_eq!(DrmScheme::detect(&probe), Some(DrmScheme::Aacs21));
+    }
+
+    #[test]
+    fn detect_returns_aacs20_when_mkb_absent() {
+        // Type-1 cert but no MKB to upgrade with -> Aacs20.
+        let c = cert(0x01);
+        let probe = DrmProbe {
+            dvd_sample_sector: None,
+            content_cert: Some(&c),
+            mkb: None,
+        };
+        assert_eq!(DrmScheme::detect(&probe), Some(DrmScheme::Aacs20));
+    }
+
+    #[test]
+    fn load_aacs21_returns_none() {
+        // The Aacs21 dispatch arm is commented out; load() must
+        // return None until KCD validation lands.
+        let uk_ro = vec![0u8; 256];
+        let vid = [0u8; 16];
+        let keydb = aacs::KeyDb::empty();
+        let providers: &[&dyn aacs::KeyProvider] = &[&keydb];
+        let ctx_aacs = aacs::ResolveContext {
+            unit_key_ro: &uk_ro,
+            content_cert: None,
+            volume_id: &vid,
+            providers,
+            mkb: None,
+        };
+        let mut ctx = DrmContext {
+            aacs: Some(ctx_aacs),
+            css: None,
+        };
+        assert!(DrmScheme::Aacs21.load(&mut ctx).is_none());
+    }
+
+    /// Exercises the V21 helper directly. Gated `#[ignore]` because
+    /// the chain reaches `MediaKeyVariantError::VariantsTableUnavailable`
+    /// without a real Variant-scheme disc to fix the per-uv table
+    /// layout against — running it here would assert only the
+    /// not-yet-wired error code. Kept as a wiring smoke-test for
+    /// future enablement.
+    #[test]
+    #[ignore]
+    fn resolve_keys_v21_helper_exists() {
+        let uk_ro = vec![0u8; 256];
+        let vid = [0xAAu8; 16];
+        let keydb = aacs::KeyDb::empty();
+        let providers: &[&dyn aacs::KeyProvider] = &[&keydb];
+        let mkb = mkb_with_variant();
+        let ctx = aacs::ResolveContext {
+            unit_key_ro: &uk_ro,
+            content_cert: None,
+            volume_id: &vid,
+            providers,
+            mkb: Some(&mkb),
+        };
+        // Just confirm the symbol is callable; we don't assert on the
+        // result.
+        let _ = aacs::resolve_keys_v21(&ctx);
+    }
+}

src/error.rs

@@ -71,6 +71,14 @@ pub const E_AACS_VID_MAC: u16 = 7010;
 pub const E_AACS_DATA_KEY: u16 = 7011;
 pub const E_DECRYPT_FAILED: u16 = 7013;
 pub const E_CSS_AUTH_FAILED: u16 = 7014;
+pub const E_AACS_HOST_CERT_REJECTED: u16 = 7015;
+pub const E_AACS_RAW_READ_UNSUPPORTED: u16 = 7016;
+pub const E_AACS_VID_UNAVAILABLE: u16 = 7017;
+pub const E_AACS_MK_UNAVAILABLE: u16 = 7018;
+pub const E_AACS_VUK_NOT_IN_KEYDB: u16 = 7019;
+pub const E_DRIVE_PROFILE_MISSING: u16 = 7020;
+pub const E_VID_CDB_UNAVAILABLE: u16 = 7021;
+pub const E_NO_DISC_KEY: u16 = 7022;
 
 // Keydb (8xxx)
 pub const E_KEYDB_CONNECT: u16 = 8000;
@@ -222,6 +230,40 @@ pub enum Error {
     AacsDataKey,
     DecryptFailed,
     CssAuthFailed,
+    /// Host certificate rejected by the drive's revocation list (HRL hit).
+    /// All available host certs failed mutual auth on this drive.
+    AacsHostCertRejected,
+    /// Drive cannot be put into raw-read mode and standard AACS cert
+    /// auth failed. No path to decryption remains.
+    AacsRawReadUnsupported,
+    /// Volume ID could not be retrieved from the drive (neither via cert
+    /// auth nor via the alternate VID read path). Downstream of step 1
+    /// of the AACS chain.
+    AacsVidUnavailable,
+    /// No available path produced a Media Key (no MK+VID in keydb, no
+    /// PK match, no DK derivation).
+    AacsMkUnavailable,
+    /// Disc-hash lookup in the keydb missed and no other path is
+    /// available (typically because VID is missing).
+    AacsVukNotInKeydb,
+    /// Drive identity did not match any bundled profile; per-drive CDB
+    /// templates aren't available so the OEM VID retrieval path can't
+    /// run.
+    DriveProfileMissing,
+    /// Drive's profile is present but doesn't carry a VID-retrieval CDB
+    /// template (older profile blob, or a drive class without an OEM
+    /// VID path).
+    VidCdbUnavailable,
+    /// The disc is AACS-encrypted and decryption was requested, but key
+    /// resolution produced no usable key for it — so muxing would emit
+    /// undecryptable garbage. Distinct from [`Error::KeydbLoad`] (no keydb
+    /// file at all): a keydb may be present but lack an entry for this disc.
+    /// `disc_hash` is the 40-hex SHA1 of `Unit_Key_RO.inf` (no `0x` prefix)
+    /// so the application can name the disc; empty if the hash wasn't
+    /// captured at scan.
+    NoDiscKey {
+        disc_hash: String,
+    },
 
     // Keydb (8xxx)
     KeydbConnect {
@@ -307,6 +349,14 @@ impl Error {
             Error::AacsDataKey => E_AACS_DATA_KEY,
             Error::DecryptFailed => E_DECRYPT_FAILED,
             Error::CssAuthFailed => E_CSS_AUTH_FAILED,
+            Error::AacsHostCertRejected => E_AACS_HOST_CERT_REJECTED,
+            Error::AacsRawReadUnsupported => E_AACS_RAW_READ_UNSUPPORTED,
+            Error::AacsVidUnavailable => E_AACS_VID_UNAVAILABLE,
+            Error::AacsMkUnavailable => E_AACS_MK_UNAVAILABLE,
+            Error::AacsVukNotInKeydb => E_AACS_VUK_NOT_IN_KEYDB,
+            Error::DriveProfileMissing => E_DRIVE_PROFILE_MISSING,
+            Error::VidCdbUnavailable => E_VID_CDB_UNAVAILABLE,
+            Error::NoDiscKey { .. } => E_NO_DISC_KEY,
             Error::KeydbConnect { .. } => E_KEYDB_CONNECT,
             Error::KeydbHttp { .. } => E_KEYDB_HTTP,
             Error::KeydbInvalid => E_KEYDB_INVALID,
@@ -433,6 +483,7 @@ impl std::fmt::Display for Error {
             Error::StreamUrlMissingPort { addr } => write!(f, "E{}: {}", self.code(), addr),
             Error::PesFrameTooLarge { size } => write!(f, "E{}: {}", self.code(), size),
             Error::IsoTooLarge { path } => write!(f, "E{}: {}", self.code(), path),
+            Error::NoDiscKey { disc_hash } => write!(f, "E{}: {}", self.code(), disc_hash),
             _ => write!(f, "E{}", self.code()),
         }
     }

src/halt.rs

@@ -0,0 +1,180 @@
+//! One-bit cooperative cancellation flag.
+//!
+//! `Halt` is a clonable token wrapping `Arc<AtomicBool>`. Pass clones into
+//! every long-running loop; the loop polls `is_cancelled()` and bails out
+//! cleanly. Calling `cancel()` from any clone flips the shared flag, and
+//! every other clone observes it on its next poll.
+//!
+//! Why: `Ordering::Relaxed` is sufficient on both load and store because
+//! this flag is purely advisory — no other memory operations piggyback on
+//! it for happens-before ordering. Callers that need to publish data
+//! across threads do so via channels or other synchronization, not via
+//! this bit.
+
+use std::sync::Arc;
+use std::sync::atomic::{AtomicBool, Ordering};
+
+/// Clonable, infallible cooperative-cancellation token.
+///
+/// Clones share the same underlying flag. `cancel()` is one-way; there is
+/// no `reset()` by design — construct a fresh `Halt` for a fresh
+/// operation.
+///
+/// Construct with [`Halt::new`] (or [`Halt::default`]). The `Default`
+/// impl forwards to `new()` — both produce a fresh, uncancelled token.
+/// The pair exists because clippy's `new_without_default` lint requires
+/// `Default` whenever a public `new()` is present, even when the two
+/// would do exactly the same thing.
+#[derive(Clone, Debug)]
+pub struct Halt(Arc<AtomicBool>);
+
+impl Halt {
+    /// Construct a fresh, uncancelled token.
+    pub fn new() -> Self {
+        Self(Arc::new(AtomicBool::new(false)))
+    }
+
+    /// Wrap an existing `Arc<AtomicBool>` as a `Halt`. Useful as a
+    /// bridge during the 0.18 deprecation window: callers that already
+    /// hold an `Arc<AtomicBool>` (e.g. `Drive::halt_flag()`, the
+    /// deprecated `DiscStream::set_halt`) can adopt the new token API
+    /// without changing the underlying flag.
+    ///
+    /// Cancelling either side flips the same bit — the wrapping `Halt`
+    /// and the original `Arc` are two views over one shared flag.
+    pub fn from_arc(flag: Arc<AtomicBool>) -> Self {
+        Self(flag)
+    }
+
+    /// Borrow the underlying `Arc<AtomicBool>`. Used at boundaries with
+    /// pre-`Halt` APIs that still take an `Arc<AtomicBool>` directly
+    /// (`CopyOptions::halt`, the deprecated `DiscStream::set_halt`).
+    /// Round 3 deletes those boundaries and this accessor with them.
+    pub fn as_arc(&self) -> &Arc<AtomicBool> {
+        &self.0
+    }
+
+    /// Flip the shared flag to cancelled. Idempotent.
+    pub fn cancel(&self) {
+        self.0.store(true, Ordering::Relaxed);
+    }
+
+    /// Read the shared flag.
+    pub fn is_cancelled(&self) -> bool {
+        self.0.load(Ordering::Relaxed)
+    }
+}
+
+impl Default for Halt {
+    fn default() -> Self {
+        Self::new()
+    }
+}
+
+/// Shared poll interval for halt-aware loops.
+///
+/// `bounded_syscall` checks the cancellation flag and the deadline
+/// every [`POLL_INTERVAL`] while blocked on a worker; the same
+/// cadence governs `Pipeline::send_with_halt`'s `try_send` retry.
+/// 250 ms is the sweet spot between responsiveness (operator presses
+/// Stop, sees it take effect within ~quarter-second) and waste
+/// (atomic load + clock read is cheap but not free at thousands of
+/// hertz).
+///
+/// Centralised here so the half-dozen halt-polling loops across `io`
+/// can't drift apart silently.
+pub const POLL_INTERVAL: std::time::Duration = std::time::Duration::from_millis(250);
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn fresh_is_not_cancelled() {
+        let h = Halt::new();
+        assert!(!h.is_cancelled());
+    }
+
+    #[test]
+    fn cancel_flips_state() {
+        let h = Halt::new();
+        assert!(!h.is_cancelled());
+        h.cancel();
+        assert!(h.is_cancelled());
+    }
+
+    #[test]
+    fn cancel_is_idempotent() {
+        let h = Halt::new();
+        h.cancel();
+        h.cancel();
+        assert!(h.is_cancelled());
+    }
+
+    #[test]
+    fn clone_shares_state() {
+        let original = Halt::new();
+        let cloned = original.clone();
+        assert!(!original.is_cancelled());
+        assert!(!cloned.is_cancelled());
+
+        // Cancel via the clone; the original observes it.
+        cloned.cancel();
+        assert!(original.is_cancelled());
+        assert!(cloned.is_cancelled());
+    }
+
+    #[test]
+    fn clone_shares_state_reverse_direction() {
+        let original = Halt::new();
+        let cloned = original.clone();
+
+        // Cancel via the original; the clone observes it.
+        original.cancel();
+        assert!(cloned.is_cancelled());
+    }
+
+    #[test]
+    fn clone_shares_state_across_threads() {
+        let h = Halt::new();
+        let h2 = h.clone();
+        let handle = std::thread::spawn(move || {
+            h2.cancel();
+        });
+        handle.join().unwrap();
+        assert!(h.is_cancelled());
+    }
+
+    #[test]
+    fn from_arc_shares_state() {
+        // The 0.18 deprecation-window bridge: a Halt built from an
+        // existing Arc<AtomicBool> must be a *view* over the same bit,
+        // not a fresh copy. Cancelling either side flips both.
+        let arc = Arc::new(AtomicBool::new(false));
+        let halt = Halt::from_arc(arc.clone());
+        assert!(!halt.is_cancelled());
+        assert!(!arc.load(Ordering::Relaxed));
+
+        // Cancel via the wrapping Halt; the original Arc observes it.
+        halt.cancel();
+        assert!(arc.load(Ordering::Relaxed));
+
+        // Conversely: flip the Arc directly; the Halt view observes it.
+        let arc2 = Arc::new(AtomicBool::new(false));
+        let halt2 = Halt::from_arc(arc2.clone());
+        arc2.store(true, Ordering::Relaxed);
+        assert!(halt2.is_cancelled());
+    }
+
+    #[test]
+    fn as_arc_returns_backing_flag() {
+        // `as_arc()` must hand back the *same* Arc, not a clone of a
+        // different bit. Verified by writing through the borrowed Arc
+        // and observing through the Halt.
+        let halt = Halt::new();
+        let arc = halt.as_arc().clone();
+        assert!(!halt.is_cancelled());
+        arc.store(true, Ordering::Relaxed);
+        assert!(halt.is_cancelled());
+    }
+}

src/ifo.rs

@@ -9,7 +9,7 @@
 
 use crate::disc::{Codec, Resolution};
 use crate::error::{Error, Result};
-use crate::sector::SectorReader;
+use crate::sector::SectorSource;
 use crate::udf::UdfFs;
 
 // ── Public types ────────────────────────────────────────────────────────────
@@ -184,7 +184,7 @@ fn bcd_byte(b: u8) -> u32 {
 ///
 /// Reads the VMG (Video Manager) to discover title sets, then reads each
 /// VTS IFO to extract PGC chains, cell addresses, and stream attributes.
-pub fn parse_vmg(reader: &mut dyn SectorReader, udf: &UdfFs) -> Result<DvdInfo> {
+pub fn parse_vmg(reader: &mut dyn SectorSource, udf: &UdfFs) -> Result<DvdInfo> {
     let vmg_data = udf.read_file(reader, "/VIDEO_TS/VIDEO_TS.IFO")?;
 
     // Validate VMG magic
@@ -263,7 +263,7 @@ pub fn parse_vmg(reader: &mut dyn SectorReader, udf: &UdfFs) -> Result<DvdInfo>
 ///
 /// `titles_info` is a list of (chapter_count, vts_title_number) from TT_SRPT.
 fn parse_vts(
-    reader: &mut dyn SectorReader,
+    reader: &mut dyn SectorSource,
     udf: &UdfFs,
     vts_number: u8,
     titles_info: &[(u16, u8)],

src/io/bounded.rs

@@ -0,0 +1,238 @@
+//! Bounded-syscall primitive: run a (potentially-blocking) operation
+//! on a worker thread, with a hard wall-clock deadline and an optional
+//! cooperative [`Halt`] poll. The calling thread is never trapped
+//! inside a kernel call.
+//!
+//! ## Why this exists
+//!
+//! [`crate::halt::Halt`] is cooperative: callers poll
+//! `is_cancelled()`. It cannot reach inside a syscall the kernel
+//! currently owns the thread for — `libc::sync_file_range`,
+//! `libc::fsync`, `File::write` on NFS, and so on. `/api/stop` from
+//! autorip therefore can't unstick a thread sitting in such a syscall.
+//!
+//! [`bounded_syscall`] is the escape hatch: it runs `op` on a fresh
+//! worker thread, then `recv_timeout`s on a rendezvous channel for the
+//! result. The wait is broken into ~250 ms slices so the calling
+//! thread can poll the supplied [`Halt`] in between. If the deadline
+//! elapses or the halt fires, the worker is intentionally leaked — the
+//! syscall will unwind whenever the kernel decides, or at process
+//! exit, but the caller is free to fall back to a degraded code path
+//! (skip the sync, log loudly, etc.).
+//!
+//! ## Trade-offs
+//!
+//! - **Thread per call.** Cheap (`std::thread::spawn` is < 100 µs on
+//!   Linux/macOS), but not free. Use on coarse-grained finalisation
+//!   syscalls (`sync_all`, `sync_file_range(WAIT_AFTER)`), not on hot
+//!   inner-loop writes.
+//! - **Leak on timeout.** A wedged syscall keeps a kernel slot and a
+//!   user-space thread around for the rest of the process's life.
+//!   Bounded by the number of independent rip/mux sessions, which is
+//!   one per disc. The alternative — trapping the caller forever —
+//!   defeats the entire purpose of `/api/stop`.
+//! - **Halt granularity ~250 ms.** Halt observation is not instant;
+//!   it's the worst-case latency of the `recv_timeout` slice. Good
+//!   enough for human-driven stop requests; not suitable for hard
+//!   real-time deadlines.
+//!
+//! ## Single source of truth
+//!
+//! Do NOT inline this pattern. Every blocking-syscall wrapper in the
+//! rip + mux pipeline calls this helper, so changes (e.g. swapping the
+//! channel impl, adjusting the poll slice, adding metrics) land in one
+//! place.
+//!
+//! ## Platform
+//!
+//! Pure `std::thread` + `std::sync::mpsc`. No `cfg(target_os)` needed
+//! here — the helper itself is platform-agnostic. Callers that wrap
+//! Linux-only syscalls (`sync_file_range`) still need their own
+//! `#[cfg(target_os = "linux")]` gates; this helper does not.
+
+use std::sync::mpsc::{RecvTimeoutError, sync_channel};
+use std::thread;
+use std::time::{Duration, Instant};
+
+use crate::halt::{Halt, POLL_INTERVAL};
+
+/// Failure outcome from a bounded syscall wrapper.
+#[derive(Debug)]
+pub(crate) enum BoundedError {
+    /// The user-visible halt token fired during the wait. The worker
+    /// thread is intentionally leaked — the caller should fall back to
+    /// a degraded code path rather than waiting on the syscall to
+    /// return.
+    Halted,
+    /// The deadline elapsed before the syscall returned. Same leak
+    /// semantics as `Halted`.
+    Timeout,
+    /// The worker thread panicked, or its sender disconnected before
+    /// sending a result. Treat as a benign no-op (callers usually
+    /// log and continue) rather than a hard error — by definition no
+    /// syscall observably ran to completion in this case.
+    WorkerLost,
+}
+
+/// Run a (potentially-blocking) operation on a worker thread with a
+/// deadline and an optional cooperative halt-token poll. Returns the
+/// operation's result if it completes within `timeout`; otherwise one
+/// of [`BoundedError::Halted`] / [`BoundedError::Timeout`] /
+/// [`BoundedError::WorkerLost`].
+///
+/// On `Halted` / `Timeout` the worker thread is intentionally leaked:
+/// the syscall will unwind whenever the kernel decides, or when the
+/// process exits. The calling thread is never trapped inside a kernel
+/// call.
+///
+/// `halt` is polled at [`POLL_INTERVAL`] granularity. Pass `None` for
+/// callers that don't (yet) have a halt token plumbed through —
+/// behaviour degrades to deadline-only, matching the 0.20.5
+/// `wait_after_with_timeout` shape this helper generalises.
+///
+/// `op` returns `R: Send + 'static`. The closure must own everything
+/// it touches because it may outlive this call (timeout / halt cases).
+pub(crate) fn bounded_syscall<F, R>(
+    halt: Option<&Halt>,
+    timeout: Duration,
+    op: F,
+) -> Result<R, BoundedError>
+where
+    F: FnOnce() -> R + Send + 'static,
+    R: Send + 'static,
+{
+    // Rendezvous channel: the worker sends exactly one value (the
+    // op's return) and then exits. Capacity-0 means the send blocks
+    // until we receive — fine on the happy path; on the timeout /
+    // halt path the receiver is dropped and the worker's send
+    // returns Err, which the worker ignores.
+    let (tx, rx) = sync_channel::<R>(0);
+    let _ = thread::Builder::new()
+        .name("freemkv-bounded-syscall".into())
+        .spawn(move || {
+            // Ignore the send error: if we time out (or get halted)
+            // before the worker finishes, the receiver is dropped
+            // and `tx.send` returns Err. Either way, the worker has
+            // nothing more to do.
+            let _ = tx.send(op());
+        });
+
+    let deadline = Instant::now() + timeout;
+    loop {
+        let now = Instant::now();
+        let remaining = deadline.saturating_duration_since(now);
+        let slice = remaining.min(POLL_INTERVAL);
+        match rx.recv_timeout(slice) {
+            Ok(v) => return Ok(v),
+            Err(RecvTimeoutError::Timeout) => {
+                if let Some(h) = halt {
+                    if h.is_cancelled() {
+                        return Err(BoundedError::Halted);
+                    }
+                }
+                if Instant::now() >= deadline {
+                    return Err(BoundedError::Timeout);
+                }
+                // Otherwise: another slice.
+            }
+            Err(RecvTimeoutError::Disconnected) => {
+                // Worker thread spawn failed, or it panicked before
+                // sending. Caller treats this as "no syscall ran" —
+                // typically a no-op + log.
+                return Err(BoundedError::WorkerLost);
+            }
+        }
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use std::sync::Arc;
+    use std::sync::atomic::{AtomicBool, Ordering};
+
+    #[test]
+    fn op_completes_quickly() {
+        let r = bounded_syscall(None, Duration::from_secs(2), || 42u32);
+        assert!(matches!(r, Ok(42)));
+    }
+
+    #[test]
+    fn op_exceeds_timeout() {
+        // Op sleeps longer than the deadline → Timeout.
+        let r = bounded_syscall(None, Duration::from_millis(300), || {
+            thread::sleep(Duration::from_secs(2));
+            0u32
+        });
+        assert!(matches!(r, Err(BoundedError::Timeout)));
+    }
+
+    #[test]
+    fn halt_fires_during_wait() {
+        let halt = Halt::new();
+        let halt2 = halt.clone();
+        // Flip the halt from a side thread after ~300 ms — long
+        // enough that the receive loop has rolled at least one
+        // 250 ms slice and is sitting in `recv_timeout` again when
+        // the bit flips.
+        thread::spawn(move || {
+            thread::sleep(Duration::from_millis(300));
+            halt2.cancel();
+        });
+        let r = bounded_syscall(Some(&halt), Duration::from_secs(5), || {
+            thread::sleep(Duration::from_secs(5));
+            0u32
+        });
+        assert!(matches!(r, Err(BoundedError::Halted)));
+    }
+
+    #[test]
+    fn worker_panics() {
+        // Worker panics → sender drops without sending → recv sees
+        // Disconnected → WorkerLost. We use an explicit panic in the
+        // op closure rather than `panic!()` from inside the channel
+        // machinery; the spawned thread's panic is contained (no
+        // process abort) because we don't `.join()` it.
+        let r = bounded_syscall(None, Duration::from_secs(2), || -> u32 {
+            panic!("intentional test panic");
+        });
+        assert!(matches!(r, Err(BoundedError::WorkerLost)));
+    }
+
+    #[test]
+    fn halt_already_set_before_call_still_returns_halted() {
+        // Halt observed on the very first poll slice. The op blocks
+        // forever; we must not wait the full timeout to notice the
+        // halt is already set.
+        let halt = Halt::new();
+        halt.cancel();
+        let started = Instant::now();
+        let r = bounded_syscall(Some(&halt), Duration::from_secs(10), || {
+            thread::sleep(Duration::from_secs(10));
+            0u32
+        });
+        assert!(matches!(r, Err(BoundedError::Halted)));
+        // Should bail out within ~1 s; allow 2 s of slack for slow
+        // CI hosts.
+        assert!(
+            started.elapsed() < Duration::from_secs(2),
+            "halt-already-set took {:?}",
+            started.elapsed()
+        );
+    }
+
+    #[test]
+    fn ok_path_takes_no_halt_token() {
+        // Sanity: the `None` halt path is the documented zero-config
+        // form (matches the 0.20.5 `wait_after_with_timeout`
+        // behaviour). Op returns immediately; we must observe Ok.
+        let flag = Arc::new(AtomicBool::new(false));
+        let f2 = flag.clone();
+        let r = bounded_syscall(None, Duration::from_secs(2), move || {
+            f2.store(true, Ordering::Relaxed);
+            "ok"
+        });
+        assert!(matches!(r, Ok("ok")));
+        assert!(flag.load(Ordering::Relaxed));
+    }
+}

src/io/byte_channel.rs

@@ -0,0 +1,327 @@
+//! Byte-sized bounded producer/consumer channel.
+//!
+//! Wraps `std::sync::mpsc::sync_channel` with a byte-accounting
+//! `Mutex<usize> + Condvar` cap. Sender blocks (cooperatively) when
+//! `used_bytes + item.byte_size() > capacity_bytes`. Receiver
+//! decrements `used_bytes` when it takes the item.
+//!
+//! Why: the existing producer→consumer channel between `DiscStream`
+//! (PES producer) and `MuxSink` (PES consumer) is bounded by frame
+//! count. Frame sizes vary 100× between metadata and keyframes, so a
+//! count-based cap either starves on small frames or buffers far too
+//! much memory on big ones. Byte-sized accounting sizes the buffer for
+//! the worst-case input stall (NFS read p99 ≈ 1–2 s × ~15 MB/s peak
+//! compressed bitrate ≈ ~30 MB) directly.
+//!
+//! The underlying mpsc channel is created with a very large slot count
+//! so the byte cap (not the slot count) is the real backpressure. Slot
+//! count is only there to give the kernel a small chunk to wake on.
+
+use std::sync::mpsc::{Receiver as MpscReceiver, RecvError, SendError, SyncSender, sync_channel};
+use std::sync::{Arc, Condvar, Mutex};
+
+/// Default byte cap for the muxer's input channel. Sized to hide a
+/// worst-case ~2 s NFS read refill at UHD peak compressed bitrate
+/// (~15 MB/s); 64 MiB gives headroom. Tweakable; not magic.
+pub const BYTE_CHANNEL_DEFAULT_CAPACITY: usize = 64 * 1024 * 1024;
+
+/// Slot capacity of the inner `sync_channel`. Large so the byte cap is
+/// the real backpressure mechanism — the mpsc slot count only exists
+/// to give the kernel a chunk to wake on. PES frames are typically
+/// ~700 B each, so 64 MiB ≈ 90 k frames; 200 k is comfortable headroom.
+const INNER_SLOT_CAPACITY: usize = 200_000;
+
+/// Anything whose in-memory cost can be accounted by a single
+/// `usize`. Implement on the item type sent through [`Sender`].
+pub trait HasByteSize {
+    /// Bytes this item contributes to the channel's used budget.
+    /// Must be > 0 to make progress (a 0-byte item would never
+    /// block the sender no matter the cap; see send_blocks_at_capacity
+    /// test).
+    fn byte_size(&self) -> usize;
+}
+
+impl HasByteSize for crate::pes::PesFrame {
+    fn byte_size(&self) -> usize {
+        // Frame data + the fixed header overhead the serializer
+        // writes (track + pts + keyframe + len). The `Vec<u8>` heap
+        // allocation also has alloc-header overhead but that's
+        // <0.1 % at typical frame sizes — folding it in would just
+        // add noise to the budget.
+        self.data.len() + 14
+    }
+}
+
+/// Shared book-keeping between [`Sender`] and [`Receiver`]. Wrapped in
+/// an `Arc` because both halves hold it independently.
+struct Accounting {
+    used: Mutex<usize>,
+    cv: Condvar,
+    capacity: usize,
+}
+
+/// Send half of the byte-bounded channel.
+///
+/// `send` blocks (on a `Condvar`) when adding the item would push
+/// `used_bytes` past `capacity_bytes`. Unblocks when the receiver
+/// `recv`s items out and notifies. Returns `Err(item)` if the
+/// receiver has been dropped — mirrors `mpsc::SyncSender::send`.
+pub struct Sender<T: HasByteSize> {
+    tx: SyncSender<T>,
+    acct: Arc<Accounting>,
+}
+
+impl<T: HasByteSize> Clone for Sender<T> {
+    fn clone(&self) -> Self {
+        Sender {
+            tx: self.tx.clone(),
+            acct: self.acct.clone(),
+        }
+    }
+}
+
+impl<T: HasByteSize> Sender<T> {
+    /// Push one item. Blocks until adding it would not exceed the
+    /// capacity, then sends through the inner mpsc channel.
+    pub fn send(&self, item: T) -> Result<(), SendError<T>> {
+        let sz = item.byte_size();
+        // Reserve capacity first. The reservation is observable to
+        // other senders via `used`; only after we win the slot do we
+        // hand the item to the inner mpsc channel. That ordering means
+        // `used` is always a conservative upper bound on what's in the
+        // mpsc queue + about-to-be-sent.
+        {
+            let mut used = self.acct.used.lock().expect("byte_channel poisoned");
+            // An item bigger than the whole capacity will never fit; let
+            // it through anyway as a one-shot reservation, otherwise the
+            // sender deadlocks forever waiting for `used == 0` AND
+            // nothing in flight. The receiver will drain it on the
+            // other side. Same behaviour as `std::sync::mpsc` for
+            // arbitrarily large messages.
+            while *used + sz > self.acct.capacity && *used > 0 {
+                used = self.acct.cv.wait(used).expect("byte_channel cv poisoned");
+            }
+            *used += sz;
+        }
+        match self.tx.send(item) {
+            Ok(()) => Ok(()),
+            Err(SendError(returned)) => {
+                // Receiver dropped — refund the reservation so a later
+                // sender on a clone doesn't observe phantom used bytes
+                // (the receiver is gone so nobody will decrement).
+                let mut used = self.acct.used.lock().expect("byte_channel poisoned");
+                *used = used.saturating_sub(sz);
+                self.acct.cv.notify_all();
+                Err(SendError(returned))
+            }
+        }
+    }
+}
+
+/// Receive half of the byte-bounded channel.
+///
+/// `recv` blocks on the inner mpsc until an item is available, then
+/// decrements the byte-accounting and wakes any sender waiting on
+/// capacity.
+pub struct Receiver<T: HasByteSize> {
+    rx: MpscReceiver<T>,
+    acct: Arc<Accounting>,
+}
+
+impl<T: HasByteSize> Receiver<T> {
+    /// Take the next item. Returns `Err(RecvError)` when all senders
+    /// have been dropped and the channel is empty.
+    pub fn recv(&self) -> Result<T, RecvError> {
+        let item = self.rx.recv()?;
+        let sz = item.byte_size();
+        let mut used = self.acct.used.lock().expect("byte_channel poisoned");
+        *used = used.saturating_sub(sz);
+        // Notify all so multi-sender setups wake every blocked sender,
+        // not just one. Wasted wakeups are cheap; missed wakeups would
+        // be a deadlock.
+        self.acct.cv.notify_all();
+        Ok(item)
+    }
+}
+
+/// Create a byte-bounded channel with the given capacity in bytes.
+/// Returns a `(Sender, Receiver)` pair; clone the `Sender` for
+/// multi-producer setups.
+pub fn channel<T: HasByteSize>(capacity_bytes: usize) -> (Sender<T>, Receiver<T>) {
+    let (tx, rx) = sync_channel::<T>(INNER_SLOT_CAPACITY);
+    let acct = Arc::new(Accounting {
+        used: Mutex::new(0),
+        cv: Condvar::new(),
+        capacity: capacity_bytes,
+    });
+    (
+        Sender {
+            tx,
+            acct: acct.clone(),
+        },
+        Receiver { rx, acct },
+    )
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use std::sync::Arc;
+    use std::sync::atomic::{AtomicUsize, Ordering};
+    use std::thread;
+    use std::time::{Duration, Instant};
+
+    /// Test payload — its `byte_size` returns whatever we passed at
+    /// construction so capacity math is exact and predictable.
+    #[derive(Clone, Debug, PartialEq, Eq)]
+    struct Item {
+        sz: usize,
+        tag: u32,
+    }
+
+    impl HasByteSize for Item {
+        fn byte_size(&self) -> usize {
+            self.sz
+        }
+    }
+
+    #[test]
+    fn send_recv_round_trip() {
+        let (tx, rx) = channel::<Item>(1024);
+        for i in 0..5 {
+            tx.send(Item { sz: 100, tag: i }).unwrap();
+        }
+        for i in 0..5 {
+            let got = rx.recv().unwrap();
+            assert_eq!(got, Item { sz: 100, tag: i });
+        }
+    }
+
+    #[test]
+    fn byte_accounting_decrements_on_recv() {
+        // Internal book-keeping check via observable side-effect: after
+        // sending K items totalling N bytes and receiving them all, a
+        // subsequent send of an N-byte item must NOT block (no items
+        // in flight, all capacity refunded).
+        let (tx, rx) = channel::<Item>(1024);
+        for _ in 0..4 {
+            tx.send(Item { sz: 256, tag: 0 }).unwrap();
+        }
+        for _ in 0..4 {
+            rx.recv().unwrap();
+        }
+        // Cap is now fully available again. Send a 1024-byte item; the
+        // `used > 0` guard means it goes through alone (no wait).
+        let start = Instant::now();
+        tx.send(Item { sz: 1024, tag: 99 }).unwrap();
+        assert!(start.elapsed() < Duration::from_millis(100));
+        let got = rx.recv().unwrap();
+        assert_eq!(got.tag, 99);
+    }
+
+    #[test]
+    fn send_blocks_at_capacity_unblocks_on_recv() {
+        // Cap = 200 bytes, item = 100 bytes. First two sends fit
+        // exactly; the third must block until a recv frees capacity.
+        let (tx, rx) = channel::<Item>(200);
+        tx.send(Item { sz: 100, tag: 0 }).unwrap();
+        tx.send(Item { sz: 100, tag: 1 }).unwrap();
+
+        let tx2 = tx.clone();
+        let sent_at = Arc::new(Mutex::new(None::<Instant>));
+        let sent_at2 = sent_at.clone();
+        let h = thread::spawn(move || {
+            tx2.send(Item { sz: 100, tag: 2 }).unwrap();
+            *sent_at2.lock().unwrap() = Some(Instant::now());
+        });
+
+        // Give the sender thread a head start; it should be parked in
+        // `cv.wait` because used (200) + 100 > capacity (200).
+        thread::sleep(Duration::from_millis(100));
+        assert!(
+            sent_at.lock().unwrap().is_none(),
+            "third send should be blocked at capacity"
+        );
+
+        // Drain one. Sender wakes and completes.
+        let recv_at = Instant::now();
+        let got = rx.recv().unwrap();
+        assert_eq!(got.tag, 0);
+        h.join().unwrap();
+
+        let sent_when = sent_at.lock().unwrap().unwrap();
+        assert!(
+            sent_when >= recv_at,
+            "sender must complete AFTER receiver freed capacity"
+        );
+
+        // Drain the remaining two.
+        assert_eq!(rx.recv().unwrap().tag, 1);
+        assert_eq!(rx.recv().unwrap().tag, 2);
+    }
+
+    #[test]
+    fn item_larger_than_capacity_still_goes_through() {
+        // Pathological case: a single item bigger than the capacity.
+        // The guard `*used > 0` lets it through when the channel is
+        // empty (otherwise the sender deadlocks forever). Matches
+        // `mpsc::SyncSender` semantics for oversize messages.
+        let (tx, rx) = channel::<Item>(100);
+        tx.send(Item { sz: 1000, tag: 7 }).unwrap();
+        let got = rx.recv().unwrap();
+        assert_eq!(got, Item { sz: 1000, tag: 7 });
+    }
+
+    #[test]
+    fn concurrent_send_recv_stress() {
+        // 4 sender threads × 1k items each, 1 receiver. Verify byte
+        // accounting stays sane (channel never deadlocks, every item
+        // arrives exactly once) under contention.
+        const SENDERS: u32 = 4;
+        const PER_SENDER: u32 = 1000;
+        const TOTAL: u32 = SENDERS * PER_SENDER;
+
+        let (tx, rx) = channel::<Item>(8 * 1024);
+        let sent = Arc::new(AtomicUsize::new(0));
+        let mut handles = Vec::new();
+        for s in 0..SENDERS {
+            let tx = tx.clone();
+            let sent = sent.clone();
+            handles.push(thread::spawn(move || {
+                for i in 0..PER_SENDER {
+                    // Vary item size so accounting actually has to
+                    // multiplex differently-sized blockers. 1B → 256B.
+                    let sz = 1 + ((i as usize) % 256);
+                    tx.send(Item {
+                        sz,
+                        tag: s * PER_SENDER + i,
+                    })
+                    .unwrap();
+                    sent.fetch_add(1, Ordering::SeqCst);
+                }
+            }));
+        }
+        // Drop our local sender so the receiver can eventually see
+        // RecvError once all sender clones are done. Cloning the
+        // sender into each producer means each clone Drop'd separately.
+        drop(tx);
+
+        let mut received = 0u32;
+        while let Ok(_item) = rx.recv() {
+            received += 1;
+        }
+        for h in handles {
+            h.join().unwrap();
+        }
+        assert_eq!(received, TOTAL);
+        assert_eq!(sent.load(Ordering::SeqCst) as u32, TOTAL);
+    }
+
+    #[test]
+    fn send_after_recv_dropped_returns_err() {
+        let (tx, rx) = channel::<Item>(1024);
+        drop(rx);
+        let r = tx.send(Item { sz: 10, tag: 0 });
+        assert!(r.is_err());
+    }
+}

src/io/byte_prefetcher.rs

@@ -0,0 +1,146 @@
+//! `BytePrefetcher` — `std::io::Read` analogue of
+//! [`crate::sector::PrefetchedSectorSource`].
+//!
+//! Spawns a producer thread that fills a bounded pool of `Vec<u8>`
+//! chunks from the underlying reader and ships them through a
+//! channel; the consumer pulls filled chunks, uses them, and sends
+//! the empty `Vec<u8>` back through a recycle channel so the
+//! producer can re-fill in place. Result: zero allocations and zero
+//! cross-thread frees in the steady-state hot loop.
+//!
+//! This is the byte-stream half of the freemkv mux highway —
+//! `BytePrefetcher` feeds [`crate::mux::demux_thread::DemuxThread`]
+//! for `m2ts://`, `network://`, `stdio://`, and any other stream
+//! whose source is an `io::Read` rather than a `SectorSource`.
+
+use crate::halt::Halt;
+use crossbeam_channel::{Receiver, Sender, bounded};
+use std::io::Read;
+use std::thread::JoinHandle;
+
+/// Items flowing through the forward channel.
+pub type Batch = std::io::Result<Vec<u8>>;
+
+/// Forward channel depth — how many filled buffers the producer can
+/// stay ahead by. Two is enough to absorb a moderate consumer stall
+/// without piling up bytes.
+const FORWARD_DEPTH: usize = 2;
+
+/// Recycle channel depth = forward + 1 so the producer always has at
+/// least one buffer to fill while the consumer holds one.
+const RECYCLE_DEPTH: usize = FORWARD_DEPTH + 1;
+
+/// Default chunk size — 16 MiB matches the ISO-mux sector batch and
+/// is large enough that per-chunk overhead is amortised; small
+/// enough that the in-flight memory footprint stays bounded.
+pub const DEFAULT_CHUNK_BYTES: usize = 16 * 1024 * 1024;
+
+/// Returned from [`BytePrefetcher::into_channels`]. Owns the
+/// producer-thread join handle so dropping the shell joins the
+/// producer.
+pub struct PrefetchShell {
+    producer: Option<JoinHandle<()>>,
+}
+
+impl Drop for PrefetchShell {
+    fn drop(&mut self) {
+        if let Some(h) = self.producer.take() {
+            let _ = h.join();
+        }
+    }
+}
+
+/// Spawned byte prefetcher. Drop joins the producer thread.
+pub struct BytePrefetcher {
+    rx: Receiver<Batch>,
+    recycle_tx: Sender<Vec<u8>>,
+    producer: Option<JoinHandle<()>>,
+}
+
+impl BytePrefetcher {
+    /// Spawn the producer thread. `reader` must be `Send` because it
+    /// moves into the thread. `chunk_bytes` is the size of each
+    /// recycled buffer; pick the natural batch size of the
+    /// downstream demuxer (16 MiB for the BD-TS mux pipeline).
+    pub fn new<R: Read + Send + 'static>(
+        mut reader: R,
+        chunk_bytes: usize,
+        halt: Option<Halt>,
+    ) -> Self {
+        let (tx, rx) = bounded::<Batch>(FORWARD_DEPTH);
+        let (recycle_tx, recycle_rx) = bounded::<Vec<u8>>(RECYCLE_DEPTH);
+
+        // Seed the recycle pool. Without these the first
+        // `recycle_rx.recv()` would block forever (no consumer has
+        // returned a buffer yet).
+        for _ in 0..RECYCLE_DEPTH {
+            let _ = recycle_tx.send(vec![0u8; chunk_bytes]);
+        }
+
+        let producer = std::thread::Builder::new()
+            .name("freemkv-byte-prefetch".into())
+            .spawn(move || {
+                loop {
+                    if halt.as_ref().map(|h| h.is_cancelled()).unwrap_or(false) {
+                        return;
+                    }
+                    let mut buf = match recycle_rx.recv() {
+                        Ok(b) => b,
+                        Err(_) => return, // consumer dropped both channels
+                    };
+                    // Re-expose the full extent (previous iteration
+                    // may have truncated after a short read).
+                    if buf.len() < chunk_bytes {
+                        buf.resize(chunk_bytes, 0);
+                    } else {
+                        // SAFETY: capacity is at least chunk_bytes
+                        // after construction.
+                        unsafe { buf.set_len(chunk_bytes) };
+                    }
+                    // Read up to one full chunk. Short reads are
+                    // valid and common — pipe `truncate` so the
+                    // consumer sees only the bytes that arrived.
+                    let n = match reader.read(&mut buf[..]) {
+                        Ok(0) => return, // EOF — drop tx, consumer sees RecvError
+                        Ok(n) => n,
+                        Err(e) => {
+                            let _ = tx.send(Err(e));
+                            return;
+                        }
+                    };
+                    buf.truncate(n);
+                    if tx.send(Ok(buf)).is_err() {
+                        return; // consumer dropped
+                    }
+                }
+            })
+            .expect("freemkv-byte-prefetch thread spawn failed");
+
+        Self {
+            rx,
+            recycle_tx,
+            producer: Some(producer),
+        }
+    }
+
+    /// Peel off the channels for zero-copy pipeline consumption. The
+    /// caller (typically [`crate::mux::demux_thread::DemuxThread`])
+    /// drains `rx`, runs the demuxer in place on each filled buffer,
+    /// and recycles back through `recycle_tx`.
+    pub fn into_channels(self) -> (Receiver<Batch>, Sender<Vec<u8>>, PrefetchShell) {
+        let mut me = self;
+        let producer = me.producer.take();
+        let rx = me.rx.clone();
+        let recycle = me.recycle_tx.clone();
+        std::mem::forget(me);
+        (rx, recycle, PrefetchShell { producer })
+    }
+}
+
+impl Drop for BytePrefetcher {
+    fn drop(&mut self) {
+        if let Some(h) = self.producer.take() {
+            let _ = h.join();
+        }
+    }
+}

src/io/file_sector_source/linux.rs

@@ -0,0 +1,65 @@
+//! Linux read-side platform hooks: sequential-access hint at open +
+//! periodic page-cache eviction during streaming reads.
+//!
+//! ## Why both
+//!
+//! `POSIX_FADV_SEQUENTIAL` at open widens the kernel's readahead window
+//! so each pread aggregates into fewer NFS round-trips. `DONTNEED` on
+//! the consumed window (called periodically by the caller) drops the
+//! already-read pages from the page cache so an 85 GB streaming ISO
+//! read doesn't fill memory and starve concurrent writes (the MKV
+//! output during mux). Together they mirror the write-side
+//! WritebackPipeline's policy.
+//!
+//! ## History
+//!
+//! Pre-Phase-1 (0.20.7 baseline) had both. Phase 1's introduction of
+//! `FileSectorSource` silently dropped the read-side DONTNEED, and
+//! 0.21.2's revert of `SEQUENTIAL` (mistakenly attributing a regression
+//! to it) removed the hint. Net effect: 85 GB of ISO reads pinned in
+//! the page cache + no readahead widening → mux throughput collapse
+//! from 18 MB/s historical to 2.7-8 MB/s on 0.21.x. Restored in 0.21.6.
+
+use std::fs::File;
+use std::os::unix::io::AsRawFd;
+
+pub(super) fn hint_sequential(file: &File, _len_bytes: u64) {
+    // Best-effort: return value ignored. A fadvise failure has no
+    // user-observable consequence.
+    unsafe {
+        libc::posix_fadvise(file.as_raw_fd(), 0, 0, libc::POSIX_FADV_SEQUENTIAL);
+    }
+}
+
+/// Drop pages in the half-open byte range `[start, start+len)` from
+/// the page cache. Called periodically by `read_sectors` to bound the
+/// read-side page cache pressure.
+pub(super) fn drop_window(file: &File, start: u64, len: u64) {
+    unsafe {
+        libc::posix_fadvise(
+            file.as_raw_fd(),
+            start as i64,
+            len as i64,
+            libc::POSIX_FADV_DONTNEED,
+        );
+    }
+}
+
+/// Async-prefetch `len` bytes at `offset` into the page cache. The
+/// kernel `readahead(2)` syscall queues the I/O and returns
+/// immediately — it does NOT wait for completion. Called right after
+/// each consumed read so the next batch's I/O overlaps with the
+/// caller's processing of the current batch (decrypt + demux + mux).
+///
+/// Without this hint, with a synchronous demux consumer running at
+/// ~50 MB/s and a single-spindle disk capable of ~150 MB/s, the disk
+/// sits idle ~70% of each iteration because kernel readahead alone
+/// (capped at `/sys/block/<dev>/queue/read_ahead_kb`, default 128 KB)
+/// can only pre-stage a tiny slice of the next batch. An explicit
+/// `readahead()` of the same size as the current batch tells the
+/// kernel to queue the full next-batch read now.
+pub(super) fn prefetch(file: &File, offset: u64, len: u64) {
+    unsafe {
+        libc::readahead(file.as_raw_fd(), offset as i64, len as usize);
+    }
+}

src/io/file_sector_source/macos.rs

@@ -0,0 +1,62 @@
+//! macOS: hint the kernel to prefetch a generous chunk. macOS has no
+//! direct `POSIX_FADV_SEQUENTIAL` equivalent; the idiomatic hint is
+//! `fcntl(F_RDADVISE, &radvisory)` describing the byte range you
+//! intend to read soon. We point it at the whole file (clamped to a
+//! ceiling so a multi-TB ISO doesn't ask the kernel to prefetch
+//! everything at once).
+
+use std::fs::File;
+use std::os::unix::io::AsRawFd;
+
+/// `F_RDADVISE` opcode — not in libc's named constants on all SDKs.
+const F_RDADVISE: libc::c_int = 44;
+
+/// Cap on the byte length we pass to `F_RDADVISE`. Asking for a
+/// multi-GB readahead window is counterproductive — the OS doesn't
+/// have that much cache to throw at one fd. 64 MiB is generous for
+/// our use case (sweep, mux) and matches the byte-channel cap so the
+/// kernel's prefetch ≥ our app-level pipeline depth.
+const RDADVISE_MAX_BYTES: i64 = 64 * 1024 * 1024;
+
+/// `radvisory` per `<sys/fcntl.h>`. repr(C) layout is stable.
+#[repr(C)]
+struct RadAdvisory {
+    ra_offset: libc::off_t,
+    ra_count: libc::c_int,
+}
+
+pub(super) fn hint_sequential(file: &File, len_bytes: u64) {
+    let bytes = (len_bytes as i64).min(RDADVISE_MAX_BYTES);
+    let mut ra = RadAdvisory {
+        ra_offset: 0,
+        ra_count: bytes as libc::c_int,
+    };
+    // Best-effort.
+    unsafe {
+        libc::fcntl(file.as_raw_fd(), F_RDADVISE, &mut ra);
+    }
+}
+
+/// macOS has no direct `POSIX_FADV_DONTNEED` equivalent for a byte
+/// range. `fcntl(F_NOCACHE)` would disable caching globally on the fd
+/// (too coarse — we want the unread region to still benefit). Best
+/// approximation: no-op. macOS's unified buffer cache is generally
+/// less prone to the pin-everything pathology that triggers the
+/// regression on Linux NFS clients.
+pub(super) fn drop_window(_file: &File, _start: u64, _len: u64) {}
+
+/// Async-prefetch the byte range `[offset, offset+len)`. macOS uses
+/// the same `fcntl(F_RDADVISE, &radvisory)` primitive as the open-
+/// time sequential hint, just targeted at a moving window instead of
+/// the whole file. The kernel queues I/O for the requested range and
+/// returns immediately.
+pub(super) fn prefetch(file: &File, offset: u64, len: u64) {
+    let bytes = (len as i64).min(RDADVISE_MAX_BYTES);
+    let mut ra = RadAdvisory {
+        ra_offset: offset as libc::off_t,
+        ra_count: bytes as libc::c_int,
+    };
+    unsafe {
+        libc::fcntl(file.as_raw_fd(), F_RDADVISE, &mut ra);
+    }
+}

src/io/file_sector_source/mod.rs

@@ -0,0 +1,361 @@
+//! [`FileSectorSource`] — read 2048-byte sectors from an ISO file on
+//! disk via direct `seek + read_exact` (`pread`-equivalent) calls,
+//! letting the kernel's own readahead policy manage prefetch.
+//!
+//! ## Why no app-level buffer
+//!
+//! Pre-0.21.3 this source held a 32 MiB (later 4 MiB) read-ahead
+//! buffer to amortise per-sector NFS round-trips. Empirically that
+//! buffer hurt: 32 MiB refills bursted the NFS TCP connection hard
+//! enough to starve the concurrent writer, and even a 4 MiB window
+//! gave the kernel less freedom to pipeline reads with writes. Direct
+//! pread per call lets Linux's readahead widen as it detects the
+//! sequential pattern, and naturally interleaves with writeback.
+//!
+//! ## DONTNEED on the consumed window
+//!
+//! Without page-cache eviction an 85 GB streaming ISO read pins the
+//! entire file in memory, starves the concurrent writer, and collapses
+//! mux throughput (observed: 2.7 MB/s mux on 0.21.5 vs. 70 MB/s
+//! isolated NFS reads). Every [`READ_DROP_CHUNK_BYTES`] of consumed
+//! bytes we call `posix_fadvise(DONTNEED)` over that window, mirroring
+//! the write-side [`crate::io::writeback::WritebackPipeline`] policy.
+//!
+//! ## Platform open hint
+//!
+//! On `open()` each platform issues its "sequential access expected"
+//! hint so OS-level readahead widens. The hint and the DONTNEED call
+//! live in per-OS sibling modules ([`linux::hint_sequential`] et al.)
+//! — no inline `#[cfg]` in this file.
+//!
+//! ## Read-ahead prefetch
+//!
+//! After every consumed read we issue an OS-level prefetch hint for
+//! the next equivalent-sized window (`platform::prefetch`). The
+//! kernel queues that I/O asynchronously and returns immediately, so
+//! the next batch's read overlaps with the caller's processing of
+//! the current batch (decrypt + demux + mux). Without this the disk
+//! sits idle ~70% of each iteration because kernel SEQUENTIAL
+//! readahead alone (capped at `read_ahead_kb`, default 128 KB) is
+//! far smaller than our 16 MiB app-level batch.
+
+#[cfg(target_os = "linux")]
+mod linux;
+#[cfg(target_os = "macos")]
+mod macos;
+#[cfg(not(any(target_os = "linux", target_os = "macos", target_os = "windows")))]
+mod other;
+#[cfg(target_os = "windows")]
+mod windows;
+
+#[cfg(target_os = "linux")]
+use linux as platform;
+#[cfg(target_os = "macos")]
+use macos as platform;
+#[cfg(not(any(target_os = "linux", target_os = "macos", target_os = "windows")))]
+use other as platform;
+#[cfg(target_os = "windows")]
+use windows as platform;
+
+use std::fs::File;
+use std::io::{Read, Seek, SeekFrom};
+use std::path::Path;
+
+use crate::error::{Error, Result};
+use crate::sector::SectorSource;
+
+const SECTOR_SIZE: usize = 2048;
+
+/// Bytes-read threshold per `posix_fadvise(DONTNEED)` drop on the
+/// read side. Mirrors `WRITEBACK_CHUNK_BYTES` so the read-side page
+/// cache stays bounded the same way the write side does.
+///
+/// 32 MiB is the empirically tuned value on the rip1 test bed (single
+/// 7200rpm HDD via SATA): smaller windows (8 / 16 MiB) shorten the
+/// kernel-readahead overlap and slow the producer; larger windows
+/// (64 / 128 MiB) let the page cache pin enough of the ISO to
+/// pressure concurrent writes. Override via `FREEMKV_READ_DROP_CHUNK_MIB`.
+const READ_DROP_CHUNK_BYTES_DEFAULT: u64 = 32 * 1024 * 1024;
+
+fn read_drop_chunk_bytes() -> u64 {
+    std::env::var("FREEMKV_READ_DROP_CHUNK_MIB")
+        .ok()
+        .and_then(|v| v.parse::<u64>().ok())
+        .filter(|&n| n > 0)
+        .map(|n| n * 1024 * 1024)
+        .unwrap_or(READ_DROP_CHUNK_BYTES_DEFAULT)
+}
+
+/// SectorSource backed by a file (ISO image). Every `read_sectors`
+/// call is a direct `seek + read_exact` against the underlying file
+/// — kernel readahead handles prefetch, and every
+/// [`READ_DROP_CHUNK_BYTES_DEFAULT`] bytes of consumed data the
+/// platform's `DONTNEED` hook drops the consumed window from the
+/// page cache to bound memory pressure.
+pub struct FileSectorSource {
+    file: File,
+    /// Total file size in sectors. Constant after construction;
+    /// surfaced via [`SectorSource::capacity_sectors`].
+    capacity: u32,
+    /// Bytes read since the last DONTNEED drop. Drives the per-
+    /// [`read_drop_chunk_bytes`] page-cache eviction in read_sectors.
+    bytes_read_since_drop: u64,
+    /// File offset at which the current drop window starts. The next
+    /// DONTNEED drops from `drop_window_start` for
+    /// `bytes_read_since_drop` bytes.
+    drop_window_start: u64,
+    /// Cached drop chunk size (resolved from env once at open).
+    drop_chunk_bytes: u64,
+}
+
+impl FileSectorSource {
+    /// Open an existing ISO file for reading. Capacity is derived
+    /// from `metadata().len() / 2048`. Returns
+    /// [`Error::IsoTooLarge`] if the file would exceed the 32-bit
+    /// LBA address space (~8 TB).
+    ///
+    /// Issues the platform's "sequential access expected" hint on the
+    /// fd (Linux `posix_fadvise(SEQUENTIAL)`, macOS `fcntl(F_RDADVISE)`,
+    /// Windows TODO stub) so the kernel's readahead widens.
+    pub fn open(path: &Path) -> std::io::Result<Self> {
+        let file = File::open(path)?;
+        let len = file.metadata()?.len();
+        let sectors = len / SECTOR_SIZE as u64;
+        if sectors > u32::MAX as u64 {
+            return Err(Error::IsoTooLarge {
+                path: path.to_string_lossy().into_owned(),
+            }
+            .into());
+        }
+        let capacity = sectors as u32;
+
+        // Best-effort sequential hint. Ignored on platforms without
+        // an equivalent primitive (or where the API exists but the
+        // FS doesn't honour it).
+        platform::hint_sequential(&file, len);
+
+        Ok(Self {
+            file,
+            capacity,
+            bytes_read_since_drop: 0,
+            drop_window_start: 0,
+            drop_chunk_bytes: read_drop_chunk_bytes(),
+        })
+    }
+}
+
+impl SectorSource for FileSectorSource {
+    fn capacity_sectors(&self) -> u32 {
+        self.capacity
+    }
+
+    fn read_sectors(
+        &mut self,
+        lba: u32,
+        count: u16,
+        out: &mut [u8],
+        _recovery: bool,
+    ) -> Result<usize> {
+        let count = count as u32;
+        let bytes = count as usize * SECTOR_SIZE;
+        debug_assert!(
+            out.len() >= bytes,
+            "FileSectorSource::read_sectors: out len {} < requested {}",
+            out.len(),
+            bytes
+        );
+        if count == 0 {
+            return Ok(0);
+        }
+        let offset = lba as u64 * SECTOR_SIZE as u64;
+        self.file
+            .seek(SeekFrom::Start(offset))
+            .map_err(|e| Error::IoError { source: e })?;
+        self.file
+            .read_exact(&mut out[..bytes])
+            .map_err(|e| Error::IoError { source: e })?;
+
+        // Queue the next batch's read with the kernel before the
+        // caller starts processing what we just returned. readahead()
+        // is non-blocking — it queues I/O and returns, so the kernel
+        // pulls those pages into cache while the consumer (decrypt +
+        // demux + mux) runs. Next read_sectors call hits a warm cache.
+        platform::prefetch(&self.file, offset + bytes as u64, bytes as u64);
+
+        // Periodic page-cache eviction on the read side. Without
+        // this, an 85 GB streaming ISO read pins the entire file in
+        // the kernel page cache, which starves concurrent writes and
+        // collapses mux throughput. Mirrors the write-side
+        // WritebackPipeline's DONTNEED policy.
+        self.bytes_read_since_drop += bytes as u64;
+        if self.bytes_read_since_drop >= self.drop_chunk_bytes {
+            let drop_start = self.drop_window_start;
+            let drop_len = self.bytes_read_since_drop;
+            platform::drop_window(&self.file, drop_start, drop_len);
+            self.drop_window_start = drop_start + drop_len;
+            self.bytes_read_since_drop = 0;
+        }
+
+        Ok(bytes)
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use std::io::Write;
+    use tempfile::tempdir;
+
+    /// Build a deterministic ISO of `sectors` sectors where sector `n`
+    /// is filled with the byte pattern `((n & 0xff) as u8)`. Lets us
+    /// verify any sector by content alone.
+    fn make_iso(path: &std::path::Path, sectors: u32) {
+        let mut f = std::fs::File::create(path).unwrap();
+        let mut chunk = vec![0u8; SECTOR_SIZE];
+        for n in 0..sectors {
+            let b = (n & 0xff) as u8;
+            chunk.iter_mut().for_each(|c| *c = b);
+            f.write_all(&chunk).unwrap();
+        }
+        f.flush().unwrap();
+    }
+
+    /// Sectors used by spanning-boundary tests. Pick something that
+    /// exercises multi-megabyte reads without making test ISOs huge.
+    /// 8192 sectors = 16 MiB — large enough to cross any readahead
+    /// chunk size we set the kernel hint to.
+    const TEST_SPAN_SECTORS: u32 = 8192;
+
+    #[test]
+    fn sequential_reads_match_file() {
+        let total = TEST_SPAN_SECTORS * 2 + 17;
+        let dir = tempdir().unwrap();
+        let path = dir.path().join("seq.iso");
+        make_iso(&path, total);
+
+        let mut src = FileSectorSource::open(&path).unwrap();
+        assert_eq!(src.capacity_sectors(), total);
+
+        let mut got = vec![0u8; SECTOR_SIZE];
+        for lba in 0..total {
+            src.read_sectors(lba, 1, &mut got, false).unwrap();
+            let expected = (lba & 0xff) as u8;
+            assert!(
+                got.iter().all(|b| *b == expected),
+                "sector {lba} content mismatch: expected 0x{expected:02x}"
+            );
+        }
+    }
+
+    #[test]
+    fn multi_sector_read_across_chunk_boundary() {
+        let total = TEST_SPAN_SECTORS * 2;
+        let dir = tempdir().unwrap();
+        let path = dir.path().join("span.iso");
+        make_iso(&path, total);
+
+        let mut src = FileSectorSource::open(&path).unwrap();
+
+        let span_lba = TEST_SPAN_SECTORS - 2;
+        let mut buf4 = vec![0u8; SECTOR_SIZE * 4];
+        src.read_sectors(span_lba, 4, &mut buf4, false).unwrap();
+        for i in 0..4 {
+            let lba = span_lba + i as u32;
+            let expected = (lba & 0xff) as u8;
+            for b in &buf4[i * SECTOR_SIZE..(i + 1) * SECTOR_SIZE] {
+                assert_eq!(*b, expected, "byte mismatch at sub-sector {i}");
+            }
+        }
+    }
+
+    #[test]
+    fn backward_seek_reads_correct_bytes() {
+        // Read forward then jump back: the SectorSource contract is
+        // byte-correctness regardless of access pattern.
+        let total = TEST_SPAN_SECTORS * 2 + 5;
+        let dir = tempdir().unwrap();
+        let path = dir.path().join("back.iso");
+        make_iso(&path, total);
+
+        let mut src = FileSectorSource::open(&path).unwrap();
+        let mut got = vec![0u8; SECTOR_SIZE];
+
+        src.read_sectors(TEST_SPAN_SECTORS + 1, 1, &mut got, false)
+            .unwrap();
+        src.read_sectors(0, 1, &mut got, false).unwrap();
+        assert!(got.iter().all(|b| *b == 0));
+    }
+
+    #[test]
+    fn read_at_eof_returns_correct_bytes() {
+        // File smaller than the readahead chunk — reads near EOF must
+        // still return correct bytes.
+        let total: u32 = 100;
+        let dir = tempdir().unwrap();
+        let path = dir.path().join("small.iso");
+        make_iso(&path, total);
+
+        let mut src = FileSectorSource::open(&path).unwrap();
+        assert_eq!(src.capacity_sectors(), total);
+
+        let mut got = vec![0u8; SECTOR_SIZE];
+        src.read_sectors(0, 1, &mut got, false).unwrap();
+        src.read_sectors(total - 1, 1, &mut got, false).unwrap();
+        let expected = ((total - 1) & 0xff) as u8;
+        assert!(got.iter().all(|b| *b == expected));
+    }
+
+    #[test]
+    fn large_single_read() {
+        // A multi-MB single read must work — the implementation has
+        // no app-level chunking, so this just exercises the direct
+        // pread path on a larger request.
+        let total = TEST_SPAN_SECTORS + 100;
+        let dir = tempdir().unwrap();
+        let path = dir.path().join("big.iso");
+        make_iso(&path, total);
+
+        let mut src = FileSectorSource::open(&path).unwrap();
+        let req = (TEST_SPAN_SECTORS + 1) as u16;
+        let req_bytes = req as usize * SECTOR_SIZE;
+        let mut big = vec![0u8; req_bytes];
+        src.read_sectors(0, req, &mut big, false).unwrap();
+        assert!(big[..SECTOR_SIZE].iter().all(|b| *b == 0));
+        let last_lba = req as u32 - 1;
+        let exp = (last_lba & 0xff) as u8;
+        let last_off = (req as usize - 1) * SECTOR_SIZE;
+        assert!(
+            big[last_off..last_off + SECTOR_SIZE]
+                .iter()
+                .all(|b| *b == exp)
+        );
+    }
+
+    #[test]
+    fn drop_chunk_size_env_override() {
+        // Explicit 8 MiB via env var.
+        // SAFETY: tests in this crate are single-threaded per the
+        // default cargo test harness, but std::env::set_var is
+        // declared `unsafe` since Rust 2024 (it can race with other
+        // threads / TLS). For a test that runs in-process before any
+        // FileSectorSource construction this is safe in practice.
+        unsafe {
+            std::env::set_var("FREEMKV_READ_DROP_CHUNK_MIB", "8");
+        }
+        assert_eq!(read_drop_chunk_bytes(), 8 * 1024 * 1024);
+
+        unsafe {
+            std::env::remove_var("FREEMKV_READ_DROP_CHUNK_MIB");
+        }
+        assert_eq!(read_drop_chunk_bytes(), READ_DROP_CHUNK_BYTES_DEFAULT);
+
+        // Garbage env value falls back to default.
+        unsafe {
+            std::env::set_var("FREEMKV_READ_DROP_CHUNK_MIB", "not-a-number");
+        }
+        assert_eq!(read_drop_chunk_bytes(), READ_DROP_CHUNK_BYTES_DEFAULT);
+        unsafe {
+            std::env::remove_var("FREEMKV_READ_DROP_CHUNK_MIB");
+        }
+    }
+}

src/io/file_sector_source/other.rs

@@ -0,0 +1,11 @@
+//! Fallback for targets without a known sequential-readahead hint
+//! (BSDs, illumos, etc.). No-op — reads still work, they just don't
+//! get the OS-level prefetch widening.
+
+use std::fs::File;
+
+pub(super) fn hint_sequential(_file: &File, _len_bytes: u64) {}
+
+pub(super) fn drop_window(_file: &File, _start: u64, _len: u64) {}
+
+pub(super) fn prefetch(_file: &File, _offset: u64, _len: u64) {}

src/io/file_sector_source/windows.rs

@@ -0,0 +1,30 @@
+//! Windows: the canonical sequential-access hint is
+//! `FILE_FLAG_SEQUENTIAL_SCAN` passed to `CreateFile` at open time —
+//! it cannot be set after the fact via `SetFileInformationByHandle`.
+//! Routing the open call through this module would mean a custom
+//! `File::from_raw_handle` plumb for every `FileSectorSource::open`
+//! caller, which is more invasive than the Phase 1 scope.
+//!
+//! TODO: replumb `FileSectorSource::open` to take an
+//! `OpenOptions`-style builder so the Windows path can flip the flag
+//! at open time. For now this is a no-op stub.
+
+use std::fs::File;
+
+pub(super) fn hint_sequential(_file: &File, _len_bytes: u64) {
+    tracing::debug!(
+        target: "mux",
+        "FileSectorSource hint_sequential: windows stub (TODO: FILE_FLAG_SEQUENTIAL_SCAN at open)"
+    );
+}
+
+/// Windows page-cache eviction is not exposed via a posix_fadvise
+/// equivalent. The kernel does its own working-set management. No-op
+/// for now.
+pub(super) fn drop_window(_file: &File, _start: u64, _len: u64) {}
+
+/// Windows async-prefetch hint. With FILE_FLAG_SEQUENTIAL_SCAN at
+/// open the kernel already prefetches aggressively, so there's no
+/// per-range hint we'd add on top. No-op stub for parity with the
+/// posix platforms.
+pub(super) fn prefetch(_file: &File, _offset: u64, _len: u64) {}

src/io/mod.rs

@@ -0,0 +1,48 @@
+//! File I/O helpers that bound kernel cache pressure on big writes.
+//!
+//! `WritebackFile` is a drop-in wrapper around `std::fs::File` for any
+//! call site that performs large sequential writes (sweep, patch, mux,
+//! etc.). It implements `Write` and `Seek` so existing code paths can
+//! swap `File` for `WritebackFile` with no body changes. Internally it
+//! drives a `WritebackPipeline` that, on Linux, drains dirty pages
+//! continuously at 32 MB granularity to avoid the kernel's
+//! accumulate-then-burst flush behaviour. macOS and Windows use a
+//! no-op pipeline — their default cache policies have not been shown
+//! to exhibit the same pathology for this access pattern.
+//!
+//! `FileSectorSource` is the read-side dual — it implements
+//! [`crate::sector::SectorSource`] for an ISO file using direct
+//! `pread`-equivalent calls so the kernel's own readahead policy runs
+//! (which interleaves naturally with the concurrent writeback). It
+//! pairs that with periodic `posix_fadvise(DONTNEED)` drops on the
+//! consumed window so an 85 GB streaming ISO read doesn't fill the
+//! page cache and starve the concurrent MKV write.
+//!
+//! `Pipeline` + `Sink` (0.18) is the generic producer/consumer primitive
+//! used by sweep, patch, and mux to overlap reads with writes via a
+//! bounded channel + dedicated consumer thread.
+//!
+//! `byte_channel` is a byte-sized producer/consumer channel for the
+//! mux pipeline, sized to absorb worst-case input read stalls.
+
+pub(crate) mod bounded;
+pub mod byte_channel;
+pub mod byte_prefetcher;
+pub mod file_sector_source;
+pub mod sink;
+mod writeback;
+mod writeback_file;
+
+#[cfg(target_os = "macos")]
+pub(crate) mod platform_macos;
+
+pub mod pipeline;
+
+pub(crate) use writeback_file::WritebackFile;
+
+// Re-exports for the 0.18 redesign. Sweep, patch, and mux are all
+// wired up (disc/sweep.rs, disc/patch.rs, autorip's ripper/mux.rs).
+pub use pipeline::{
+    DEFAULT_PIPELINE_DEPTH, Flow, Pipeline, READ_PIPELINE_DEPTH, Sink, WRITE_PIPELINE_DEPTH,
+    WRITE_THROUGH_DEPTH,
+};

src/io/pipeline.rs

@@ -0,0 +1,913 @@
+//! Generic bounded producer/consumer pipeline.
+//!
+//! `Pipeline<I, R>` spawns a single consumer thread, hands it items
+//! through a bounded `mpsc::sync_channel`, and joins it on `finish()`.
+//! The consumer's behaviour is supplied by a [`Sink`] implementation:
+//! `apply` is called once per item, `close` is called once at the end.
+//!
+//! Three call sites in libfreemkv want a producer/consumer split —
+//! sweep (migrated to `disc/sweep.rs::SweepSink`), patch, and mux.
+//! 0.18 collapses all three onto this primitive; sweep is in,
+//! patch and mux migrate in later 0.18 slices.
+//!
+//! ## Cancellation and error semantics
+//!
+//! - Producer dropping the channel (via `Pipeline::finish` dropping
+//!   `tx`) signals end-of-stream; consumer flushes via `close()` and
+//!   returns its `Output`.
+//! - Consumer returning [`Flow::Stop`] also calls `close()` and
+//!   returns its `Output`. `send()` from the producer will then either
+//!   succeed (if the item already fit in the channel buffer) or fail
+//!   with `Err(item)` once the consumer has dropped its receiver.
+//! - Consumer returning `Err` from `apply` skips `close()` entirely;
+//!   the consumer keeps draining the channel so the producer never
+//!   blocks on a dead receiver, and the first error is propagated as
+//!   the `JoinHandle` result.
+//! - Consumer panic is converted into
+//!   `Error::IoError { source: io::Error::other(...) }`.
+//!
+//! ## Debug logging
+//!
+//! Set `FREEMKV_DEBUG=1` environment variable to enable verbose debug
+//! logging throughout the pipeline (channel sends/receives, backpressure,
+//! consumer lag detection). This is critical for diagnosing stalls.
+
+use std::io;
+use std::thread::{self, JoinHandle};
+use std::time::{Duration, Instant};
+
+use crossbeam_channel::{Sender, TrySendError, bounded};
+
+use crate::error::Error;
+use crate::halt::Halt;
+
+/// Deadline for [`Pipeline::finish_with_halt`]'s polling join. Chosen
+/// to be comfortably longer than the autorip hard watchdog
+/// (`HARD_WATCHDOG_STALL_SECS = 300s`) so the watchdog's `exit(1)`
+/// fires first when both are racing on the same wedged consumer.
+///
+/// 10 minutes is a backstop, not a normal timeout — the consumer is
+/// expected to drain in seconds. If we hit this, something is wedged
+/// inside a kernel call the consumer thread can't unwind from, and the
+/// caller has already lost the rip.
+pub const JOIN_TIMEOUT_SECS: u64 = 600;
+
+/// Halt-check cadence for the send loop. Producer blocks on
+/// [`crossbeam_channel::Sender::send_timeout`] for this slice — the
+/// kernel wakes it the instant the consumer drains a slot, so on the
+/// happy path there's no throughput cap from this primitive at all
+/// (the cap is whatever the underlying medium can sustain). When the
+/// consumer is genuinely wedged, the timeout fires every
+/// [`crate::halt::POLL_INTERVAL`] and the producer checks the halt
+/// token; that's the latency a stop request will observe.
+///
+/// Single source of truth lives in [`crate::halt::POLL_INTERVAL`]
+/// (also used by `bounded_syscall`). Aliased here for readability of
+/// the send/finish call sites below.
+///
+/// 0.21.7 replaced an old `std::sync::mpsc::sync_channel` + 50 ms
+/// `thread::sleep` polling loop that capped mux throughput at
+/// ~20 frames/sec ≈ 1 MB/s on saturated channels.
+use crate::halt::POLL_INTERVAL;
+const SEND_HALT_CHECK_INTERVAL: Duration = POLL_INTERVAL;
+
+/// Check if verbose debug logging is enabled via FREEMKV_DEBUG env var.
+pub fn debug_enabled() -> bool {
+    std::env::var("FREEMKV_DEBUG")
+        .ok()
+        .map(|v| v == "1" || v == "true" || v == "yes")
+        .unwrap_or(false)
+}
+
+/// Default channel depth for callers without a specific reason to
+/// pick another value. Kept conservative (4) — most callers should
+/// use READ_PIPELINE_DEPTH or WRITE_PIPELINE_DEPTH instead.
+pub const DEFAULT_PIPELINE_DEPTH: usize = 4;
+
+/// Read pipeline depth. Larger buffer compensates for drive variability
+/// and NFS sync_file_range stalls; keeps ISO reader thread fed even when
+/// consumer blocks on write.
+pub const READ_PIPELINE_DEPTH: usize = 32;
+
+/// Write pipeline depth. Smaller buffer reduces backpressure risk when
+/// sync_file_range blocks; prevents producer from accumulating too much
+/// work while consumer waits for NFS to drain.
+pub const WRITE_PIPELINE_DEPTH: usize = 16;
+
+/// Channel depth for write-through pipelines. Each `send` fully
+/// drains before the next can enqueue. Use this when the producer
+/// must observe consumer side-effects (e.g. mapfile state) before
+/// emitting the next item. Currently used by `disc::patch`.
+pub const WRITE_THROUGH_DEPTH: usize = 1;
+
+/// Outcome of [`Sink::apply`]: either keep feeding items
+/// ([`Flow::Continue`]), or stop the pipeline early and run `close()`
+/// ([`Flow::Stop`]).
+///
+/// `Stop` has no in-tree caller in this slice — sweep never returns
+/// it (it always processes the producer's full work-list before the
+/// channel is dropped). Patch and mux are the intended consumers and
+/// migrate in later 0.18 slices. The variant ships now so the contract
+/// is fixed; the targeted `#[allow]` is removed when patch lands.
+pub enum Flow {
+    Continue,
+    #[allow(dead_code)]
+    Stop,
+}
+
+/// Consumer-side of a [`Pipeline`]. The pipeline owns one of these on
+/// its consumer thread and calls `apply` once per received item, then
+/// `close` once at end-of-stream.
+pub trait Sink<I>: Send + 'static {
+    /// Type returned from `close()` and surfaced via
+    /// [`Pipeline::finish`].
+    type Output: Send + 'static;
+
+    /// Apply one item. Returning [`Flow::Continue`] keeps the
+    /// pipeline running; [`Flow::Stop`] ends it cleanly (still calls
+    /// `close()`). An error short-circuits: `close()` is *not* called
+    /// and the error is what `finish()` will return, but the consumer
+    /// keeps draining the channel so the producer never blocks on a
+    /// dead receiver.
+    fn apply(&mut self, item: I) -> Result<Flow, Error>;
+
+    /// Called once at end-of-stream — either because the producer
+    /// dropped `tx` or because `apply` returned [`Flow::Stop`]. Use
+    /// this to flush, fsync, finalise. Skipped if any prior `apply`
+    /// returned `Err`.
+    fn close(self) -> Result<Self::Output, Error>;
+}
+
+/// Bounded producer/consumer pipeline. Holds the producer-side
+/// channel and the consumer thread's join handle.
+pub struct Pipeline<I: Send + 'static, R: Send + 'static> {
+    tx: Sender<I>,
+    handle: JoinHandle<Result<R, Error>>,
+}
+
+impl<I: Send + 'static, R: Send + 'static> Pipeline<I, R> {
+    /// Spawn the consumer thread with the given channel depth and
+    /// [`Sink`].
+    ///
+    /// The thread is named `freemkv-pipeline-consumer` so it shows up
+    /// distinctly in stack traces and `top -H`. Callers that want a
+    /// more specific name (e.g. `freemkv-sweep-consumer`) should use
+    /// [`Pipeline::spawn_named`] instead. Returns an `Error::IoError`
+    /// if the OS refuses the thread spawn (resource exhaustion);
+    /// callers already operate in fallible context, so this is
+    /// propagated rather than panicked.
+    ///
+    /// Sweep uses [`Pipeline::spawn_named`] directly so the consumer
+    /// thread shows up as `freemkv-sweep-consumer`; mux uses
+    /// `freemkv-mux-consumer`. `Pipeline::spawn` (this function, with
+    /// the default name) is used by `disc::patch` and by the unit
+    /// tests in this module.
+    pub fn spawn<S: Sink<I, Output = R>>(depth: usize, sink: S) -> Result<Self, Error> {
+        Self::spawn_named("freemkv-pipeline-consumer", depth, sink)
+    }
+
+    /// Like [`Pipeline::spawn`] but lets the caller supply the
+    /// consumer thread's name. Useful when several pipelines run in
+    /// the same process and stack traces / `top -H` need to tell them
+    /// apart (e.g. `freemkv-sweep-consumer`, `freemkv-mux-consumer`).
+    pub fn spawn_named<S: Sink<I, Output = R>>(
+        name: &str,
+        depth: usize,
+        sink: S,
+    ) -> Result<Self, Error> {
+        let (tx, rx) = bounded::<I>(depth);
+        let handle = thread::Builder::new()
+            .name(name.into())
+            .spawn(move || -> Result<R, Error> {
+                let mut sink = sink;
+                let mut first_err: Option<Error> = None;
+                let mut stopped = false;
+
+                while let Ok(item) = rx.recv() {
+                    if debug_enabled() {
+                        tracing::debug!("Pipeline receive: item={}", std::any::type_name::<I>());
+                    }
+
+                    let apply_start = std::time::Instant::now();
+
+                    if first_err.is_some() || stopped {
+                        // Drain remaining items so the producer never
+                        // blocks on a dead receiver. `apply` is not
+                        // called once we've decided to stop.
+                        continue;
+                    }
+                    match sink.apply(item) {
+                        Ok(Flow::Continue) => {}
+                        Ok(Flow::Stop) => {
+                            stopped = true;
+                            if debug_enabled() {
+                                tracing::debug!("Pipeline: consumer returned Flow::Stop");
+                            }
+                        }
+                        Err(e) => {
+                            if debug_enabled() {
+                                tracing::debug!("Pipeline: apply error, stopping, err={:?}", e);
+                            }
+                            first_err = Some(e);
+                        }
+                    }
+
+                    let apply_elapsed = apply_start.elapsed();
+                    if debug_enabled() && apply_elapsed > std::time::Duration::from_millis(100) {
+                        tracing::debug!(
+                            "Pipeline apply: took {:.2}s, item={}",
+                            apply_elapsed.as_secs_f64(),
+                            std::any::type_name::<I>()
+                        );
+                    } else if debug_enabled() {
+                        tracing::debug!(
+                            "Pipeline apply: OK in {:.3}ms, item={}",
+                            apply_elapsed.as_micros(),
+                            std::any::type_name::<I>()
+                        );
+                    }
+                }
+
+                match first_err {
+                    Some(e) => Err(e),
+                    None => sink.close(),
+                }
+            })
+            .map_err(|e| Error::IoError { source: e })?;
+
+        Ok(Pipeline { tx, handle })
+    }
+
+    /// Push one item. Blocks if the channel is full — that's the
+    /// back-pressure the whole primitive exists to provide. Returns
+    /// the item back if the consumer thread is gone (panicked or
+    /// already returned).
+    ///
+    /// After the consumer returns [`Flow::Stop`], `send` will silently
+    /// buffer items into the channel until the channel fills, then
+    /// return `Err(item)` once the consumer has dropped its receiver.
+    /// Producers that need to stop pushing on `Stop` should track an
+    /// independent signal (e.g. `Halt`) — `send` alone is not the
+    /// notification edge.
+    pub fn send(&self, item: I) -> Result<(), I> {
+        let start = std::time::Instant::now();
+        match self.tx.send(item) {
+            Ok(()) => {
+                let elapsed = start.elapsed();
+                if debug_enabled() && elapsed > std::time::Duration::from_millis(10) {
+                    tracing::debug!(
+                        "Pipeline send: blocked {:.2}s, item={}",
+                        elapsed.as_secs_f64(),
+                        std::any::type_name::<I>()
+                    );
+                } else if debug_enabled() {
+                    tracing::debug!("Pipeline send: OK in {:.3}ms", elapsed.as_micros());
+                }
+                Ok(())
+            }
+            Err(e) => {
+                let elapsed = start.elapsed();
+                if debug_enabled() && elapsed > std::time::Duration::from_millis(10) {
+                    tracing::debug!(
+                        "Pipeline send: blocked {:.2}s before channel closed, item={}",
+                        elapsed.as_secs_f64(),
+                        std::any::type_name::<I>()
+                    );
+                } else if debug_enabled() {
+                    tracing::debug!("Pipeline send: failed after {:.3}ms", elapsed.as_micros());
+                }
+                Err(e.0)
+            }
+        }
+    }
+
+    /// Non-blocking variant of [`Pipeline::send`]. If the channel is
+    /// full or the consumer has hung up, the item is returned in
+    /// `Err`. Useful for best-effort signalling (e.g. sweep's
+    /// throttled `StatsRequest`) where dropping the message is
+    /// preferable to blocking the producer.
+    pub fn try_send(&self, item: I) -> Result<(), TrySendError<I>> {
+        self.tx.try_send(item)
+    }
+
+    /// Halt-aware bounded variant of [`Pipeline::send`].
+    ///
+    /// Uses [`crossbeam_channel::Sender::send_timeout`] so the producer
+    /// thread BLOCKS on consumer drain (kernel-wakeup) rather than
+    /// polling. The timeout slice is just the halt-observation cadence
+    /// ([`SEND_HALT_CHECK_INTERVAL`]) — on the happy path the producer
+    /// wakes the instant the consumer drains a slot, so there is no
+    /// throughput cap from this primitive at any medium speed.
+    ///
+    /// Returns:
+    ///
+    /// - `Ok(())` once the item lands in the channel.
+    /// - `Err(item)` if the consumer disconnected, the halt fired, or
+    ///   the deadline elapsed — the caller gets the item back so it
+    ///   can decide whether to drop it, route it elsewhere, or unwind.
+    ///
+    /// Use this in producer threads that have a `Halt` token threaded
+    /// through (mux, sweep, patch). Plain [`Pipeline::send`] is
+    /// preserved for callers that don't (yet) plumb halt through.
+    ///
+    /// Unlike [`Pipeline::send`], this never blocks the producer
+    /// thread inside an unkillable `mpsc::send` — if the consumer is
+    /// wedged inside an unkillable syscall, the producer can still
+    /// observe `/api/stop` and unwind within
+    /// [`SEND_HALT_CHECK_INTERVAL`].
+    pub fn send_with_halt(&self, item: I, halt: &Halt, deadline: Duration) -> Result<(), I> {
+        use crossbeam_channel::SendTimeoutError;
+        let end = Instant::now() + deadline;
+        let mut pending = item;
+        loop {
+            // Pre-check the cheap exit conditions before parking.
+            if halt.is_cancelled() {
+                if debug_enabled() {
+                    tracing::debug!(
+                        "Pipeline send_with_halt: halt observed, returning item={}",
+                        std::any::type_name::<I>()
+                    );
+                }
+                return Err(pending);
+            }
+            let now = Instant::now();
+            if now >= end {
+                if debug_enabled() {
+                    tracing::debug!(
+                        "Pipeline send_with_halt: deadline elapsed, returning item={}",
+                        std::any::type_name::<I>()
+                    );
+                }
+                return Err(pending);
+            }
+            // Wait for space-available or halt-check tick, whichever
+            // is sooner. Crossbeam's send_timeout is kernel-wakeup
+            // based: the consumer's recv on a saturated channel
+            // signals this thread the moment a slot opens up.
+            let slice = SEND_HALT_CHECK_INTERVAL.min(end.saturating_duration_since(now));
+            match self.tx.send_timeout(pending, slice) {
+                Ok(()) => return Ok(()),
+                Err(SendTimeoutError::Timeout(returned)) => {
+                    pending = returned;
+                    // loop: re-check halt + deadline, then park again
+                }
+                Err(SendTimeoutError::Disconnected(returned)) => {
+                    if debug_enabled() {
+                        tracing::debug!(
+                            "Pipeline send_with_halt: consumer disconnected, item={}",
+                            std::any::type_name::<I>()
+                        );
+                    }
+                    return Err(returned);
+                }
+            }
+        }
+    }
+
+    /// Drop the producer-side channel and wait for the consumer
+    /// thread to finish. Returns whatever the consumer's `close()`
+    /// produced, or the first `apply` error, or — on consumer panic —
+    /// an `Error::IoError` whose source is `io::Error::other(...)`
+    /// with a "pipeline consumer panicked: <payload>" message
+    /// (callers can match on the constant prefix).
+    pub fn finish(self) -> Result<R, Error> {
+        let Pipeline { tx, handle } = self;
+        // Explicit drop, although the destructure already drops `tx`
+        // at end-of-scope. Being explicit keeps the intent obvious.
+        drop(tx);
+        match handle.join() {
+            Ok(result) => result,
+            Err(payload) => {
+                // Preserve the original panic message when the
+                // consumer's panic payload was a `&str` or `String`
+                // (the two stdlib formats that `panic!` produces).
+                // Anything else falls back to "(no message)".
+                let msg = payload
+                    .downcast_ref::<&'static str>()
+                    .copied()
+                    .or_else(|| payload.downcast_ref::<String>().map(|s| s.as_str()))
+                    .unwrap_or("(no message)");
+                Err(Error::IoError {
+                    source: io::Error::other(format!("pipeline consumer panicked: {msg}")),
+                })
+            }
+        }
+    }
+
+    /// Halt-aware, deadline-bounded variant of [`Pipeline::finish`].
+    ///
+    /// Drops the producer-side channel (same as `finish`) and then
+    /// polls `JoinHandle::is_finished()` on a 250 ms cadence. Between
+    /// slices, checks (1) the optional [`Halt`] token and (2) the
+    /// [`JOIN_TIMEOUT_SECS`] deadline. Returns:
+    ///
+    /// - `Ok(R)` on a clean consumer exit.
+    /// - `Err(Error::IoError)` with one of three message prefixes for
+    ///   wedge cases:
+    ///   - `"pipeline join halted"` — halt fired while waiting.
+    ///   - `"pipeline join timed out"` — `JOIN_TIMEOUT_SECS` elapsed.
+    ///   - `"pipeline consumer panicked"` — same as `finish()`.
+    ///
+    /// In the `halted` and `timed out` branches the consumer thread is
+    /// intentionally leaked — exactly the same trade-off the
+    /// `bounded_syscall` primitive makes. The wedged kernel call
+    /// inside the consumer will unwind whenever it does, or at
+    /// process exit. The caller is free to fall back to a degraded
+    /// path (in autorip's case: `exit(1)` after the hard watchdog
+    /// escalation, letting Docker restart the container).
+    ///
+    /// Plain [`Pipeline::finish`] is preserved for callers without a
+    /// halt-token plumbed through; that path still blocks indefinitely
+    /// on `join()`, matching pre-0.20.8 behaviour.
+    pub fn finish_with_halt(self, halt: Option<&Halt>) -> Result<R, Error> {
+        let Pipeline { tx, handle } = self;
+        drop(tx);
+        let deadline = Instant::now() + Duration::from_secs(JOIN_TIMEOUT_SECS);
+        loop {
+            if handle.is_finished() {
+                return match handle.join() {
+                    Ok(result) => result,
+                    Err(payload) => {
+                        let msg = payload
+                            .downcast_ref::<&'static str>()
+                            .copied()
+                            .or_else(|| payload.downcast_ref::<String>().map(|s| s.as_str()))
+                            .unwrap_or("(no message)");
+                        Err(Error::IoError {
+                            source: io::Error::other(format!("pipeline consumer panicked: {msg}")),
+                        })
+                    }
+                };
+            }
+            if let Some(h) = halt {
+                if h.is_cancelled() {
+                    // Consumer thread is intentionally leaked.
+                    return Err(Error::IoError {
+                        source: io::Error::other("pipeline join halted"),
+                    });
+                }
+            }
+            if Instant::now() >= deadline {
+                // Consumer thread is intentionally leaked.
+                return Err(Error::IoError {
+                    source: io::Error::other("pipeline join timed out"),
+                });
+            }
+            thread::sleep(POLL_INTERVAL);
+        }
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use std::sync::Arc;
+    use std::sync::atomic::{AtomicUsize, Ordering};
+    use std::time::{Duration, Instant};
+
+    /// Sums u64s; returns the total from `close`.
+    struct SumSink {
+        total: u64,
+    }
+
+    impl Sink<u64> for SumSink {
+        type Output = u64;
+
+        fn apply(&mut self, item: u64) -> Result<Flow, Error> {
+            self.total += item;
+            Ok(Flow::Continue)
+        }
+
+        fn close(self) -> Result<u64, Error> {
+            Ok(self.total)
+        }
+    }
+
+    #[test]
+    fn happy_path_sums_items() {
+        let pipe = Pipeline::spawn(DEFAULT_PIPELINE_DEPTH, SumSink { total: 0 })
+            .expect("spawn should succeed");
+        let mut expected = 0u64;
+        for i in 0..100u64 {
+            expected += i;
+            pipe.send(i).expect("send should succeed");
+        }
+        let total = pipe.finish().expect("finish should succeed");
+        assert_eq!(total, expected);
+        assert_eq!(total, (0..100u64).sum::<u64>());
+    }
+
+    /// Sleeps `delay` per apply; counts how many it received.
+    struct SlowSink {
+        delay: Duration,
+        count: Arc<AtomicUsize>,
+    }
+
+    impl Sink<()> for SlowSink {
+        type Output = usize;
+
+        fn apply(&mut self, _item: ()) -> Result<Flow, Error> {
+            std::thread::sleep(self.delay);
+            self.count.fetch_add(1, Ordering::SeqCst);
+            Ok(Flow::Continue)
+        }
+
+        fn close(self) -> Result<usize, Error> {
+            Ok(self.count.load(Ordering::SeqCst))
+        }
+    }
+
+    #[test]
+    fn back_pressure_blocks_sender() {
+        // depth=2 + 5 sends + 50ms/apply: with the consumer pinned at
+        // 50 ms per item, the producer can buffer 2 (channel cap) +
+        // 1 (consumer in flight) = 3 items before sends 4 and 5 must
+        // block on consumer progress. Wall-clock floor across all 5
+        // sends is therefore ~2 * 50ms = 100ms (sends 4 and 5 each
+        // wait roughly one apply-cycle). Use 80 ms as the assertion
+        // floor to stay above the 50ms-per-item progress floor while
+        // tolerating CI jitter — it still proves blocking is real.
+        let count = Arc::new(AtomicUsize::new(0));
+        let sink = SlowSink {
+            delay: Duration::from_millis(50),
+            count: count.clone(),
+        };
+        let pipe = Pipeline::spawn(2, sink).expect("spawn should succeed");
+
+        let start = Instant::now();
+        for _ in 0..5 {
+            pipe.send(()).expect("send should succeed");
+        }
+        let elapsed_send = start.elapsed();
+
+        let total = pipe.finish().expect("finish should succeed");
+        assert_eq!(total, 5);
+        assert!(
+            elapsed_send >= Duration::from_millis(80),
+            "back-pressure not observed: 5 sends with depth=2 and 50ms/apply \
+             took {elapsed_send:?}, expected ≥ ~100ms (one or more sends \
+             should have blocked behind the consumer)"
+        );
+    }
+
+    /// Returns `Err` on the Nth apply (1-indexed). Tracks all calls.
+    struct FailOnNthSink {
+        n: usize,
+        seen: Arc<AtomicUsize>,
+        close_called: Arc<AtomicUsize>,
+    }
+
+    impl Sink<u64> for FailOnNthSink {
+        type Output = ();
+
+        fn apply(&mut self, _item: u64) -> Result<Flow, Error> {
+            let i = self.seen.fetch_add(1, Ordering::SeqCst) + 1;
+            if i == self.n {
+                Err(Error::DecryptFailed)
+            } else {
+                Ok(Flow::Continue)
+            }
+        }
+
+        fn close(self) -> Result<(), Error> {
+            self.close_called.fetch_add(1, Ordering::SeqCst);
+            Ok(())
+        }
+    }
+
+    #[test]
+    fn apply_error_drains_then_propagates() {
+        let seen = Arc::new(AtomicUsize::new(0));
+        let close_called = Arc::new(AtomicUsize::new(0));
+        let pipe = Pipeline::spawn(
+            DEFAULT_PIPELINE_DEPTH,
+            FailOnNthSink {
+                n: 3,
+                seen: seen.clone(),
+                close_called: close_called.clone(),
+            },
+        )
+        .expect("spawn should succeed");
+
+        // Send 10 items. Subsequent sends after the 3rd error must
+        // still succeed (the consumer is draining).
+        for i in 0..10u64 {
+            pipe.send(i).expect("send should succeed even after error");
+        }
+
+        let res = pipe.finish();
+        assert!(matches!(res, Err(Error::DecryptFailed)));
+        assert_eq!(
+            close_called.load(Ordering::SeqCst),
+            0,
+            "close() must not be called when apply returned Err"
+        );
+        // The consumer kept calling `recv` to drain after the error;
+        // it just stopped invoking `apply`. So `seen` is exactly 3
+        // (apply was called for items 1, 2, 3).
+        assert_eq!(seen.load(Ordering::SeqCst), 3);
+    }
+
+    /// Returns `Flow::Stop` on the Nth apply.
+    struct StopOnNthSink {
+        n: usize,
+        seen: Arc<AtomicUsize>,
+        close_called: Arc<AtomicUsize>,
+    }
+
+    impl Sink<u64> for StopOnNthSink {
+        type Output = usize;
+
+        fn apply(&mut self, _item: u64) -> Result<Flow, Error> {
+            let i = self.seen.fetch_add(1, Ordering::SeqCst) + 1;
+            if i >= self.n {
+                Ok(Flow::Stop)
+            } else {
+                Ok(Flow::Continue)
+            }
+        }
+
+        fn close(self) -> Result<usize, Error> {
+            self.close_called.fetch_add(1, Ordering::SeqCst);
+            Ok(self.seen.load(Ordering::SeqCst))
+        }
+    }
+
+    #[test]
+    fn apply_stop_calls_close_and_returns_output() {
+        let seen = Arc::new(AtomicUsize::new(0));
+        let close_called = Arc::new(AtomicUsize::new(0));
+        let pipe = Pipeline::spawn(
+            DEFAULT_PIPELINE_DEPTH,
+            StopOnNthSink {
+                n: 3,
+                seen: seen.clone(),
+                close_called: close_called.clone(),
+            },
+        )
+        .expect("spawn should succeed");
+
+        // Send 10 items. After Stop, subsequent sends may either
+        // succeed (already buffered) or fail with Err(I) (channel
+        // closed). Both are valid — we don't assert on the send
+        // results.
+        for i in 0..10u64 {
+            let _ = pipe.send(i);
+        }
+
+        let out = pipe.finish().expect("finish should succeed after Stop");
+        assert_eq!(close_called.load(Ordering::SeqCst), 1);
+        // At least 3 items processed (the one that returned Stop).
+        assert!(
+            out >= 3,
+            "expected ≥ 3 applies before Stop took effect, got {out}"
+        );
+    }
+
+    /// Panics on the first apply call.
+    struct PanickingSink;
+
+    impl Sink<u64> for PanickingSink {
+        type Output = ();
+
+        fn apply(&mut self, _item: u64) -> Result<Flow, Error> {
+            panic!("synthetic test panic");
+        }
+
+        fn close(self) -> Result<(), Error> {
+            Ok(())
+        }
+    }
+
+    #[test]
+    fn consumer_panic_becomes_io_error() {
+        // Silence the panic message that would otherwise pollute the
+        // test output — we expect this panic.
+        let prev = std::panic::take_hook();
+        std::panic::set_hook(Box::new(|_| {}));
+
+        let pipe =
+            Pipeline::spawn(DEFAULT_PIPELINE_DEPTH, PanickingSink).expect("spawn should succeed");
+        // First send may succeed (item buffered before panic) or fail
+        // (channel closed after panic) — either is fine.
+        let _ = pipe.send(1);
+        // Drain a few more sends; once the channel is closed they'll
+        // return Err(I), which we just discard.
+        for i in 0..5u64 {
+            let _ = pipe.send(i);
+        }
+        let res = pipe.finish();
+
+        std::panic::set_hook(prev);
+
+        match res {
+            Err(Error::IoError { source }) => {
+                let msg = source.to_string();
+                // Constant prefix lets callers match without parsing
+                // the variable payload tail.
+                assert!(
+                    msg.contains("pipeline consumer panicked"),
+                    "expected constant panic prefix, got: {msg}"
+                );
+                // The original `panic!` payload (a `&'static str`) must
+                // be preserved — without the downcast the message
+                // would just be the prefix.
+                assert!(
+                    msg.contains("synthetic test panic"),
+                    "expected original panic payload, got: {msg}"
+                );
+            }
+            other => panic!("expected Err(IoError), got {other:?}"),
+        }
+    }
+
+    /// Never-completing sink — `apply` blocks until cancelled. Signals
+    /// `started` once it has consumed its first item so the test
+    /// driver knows the consumer thread is wedged in `apply` (and
+    /// will no longer drain the channel). Used to drive the
+    /// halt/timeout paths of `send_with_halt` and `finish_with_halt`
+    /// without depending on real I/O.
+    struct NeverDrainsSink {
+        cancel: Arc<std::sync::atomic::AtomicBool>,
+        started: Arc<std::sync::atomic::AtomicBool>,
+    }
+
+    impl Sink<u64> for NeverDrainsSink {
+        type Output = ();
+
+        fn apply(&mut self, _item: u64) -> Result<Flow, Error> {
+            self.started.store(true, Ordering::SeqCst);
+            while !self.cancel.load(Ordering::SeqCst) {
+                std::thread::sleep(Duration::from_millis(20));
+            }
+            Ok(Flow::Continue)
+        }
+
+        fn close(self) -> Result<(), Error> {
+            Ok(())
+        }
+    }
+
+    /// Spin until `started` flips or `bail` elapses. Used by the
+    /// send_with_halt tests to synchronise with the consumer thread
+    /// before exercising the bounded-send timeout path.
+    fn wait_for_started(started: &Arc<std::sync::atomic::AtomicBool>, bail: Duration) {
+        let end = Instant::now() + bail;
+        while !started.load(Ordering::SeqCst) {
+            assert!(Instant::now() < end, "consumer never started apply()");
+            std::thread::sleep(Duration::from_millis(10));
+        }
+    }
+
+    #[test]
+    fn send_with_halt_returns_item_on_deadline() {
+        // depth=1 + consumer wedged in apply on the first item, AND
+        // the channel buffer already loaded with a second item, means
+        // any further `try_send` sees Full; with a 200 ms deadline and
+        // no halt fired, send_with_halt must return `Err(item)` within
+        // roughly the deadline. Synchronising on `started` ensures the
+        // consumer has actually started its wedged apply BEFORE we
+        // load the channel-buffer slot — without that, the consumer
+        // could still drain in a race window.
+        let cancel = Arc::new(std::sync::atomic::AtomicBool::new(false));
+        let started = Arc::new(std::sync::atomic::AtomicBool::new(false));
+        let pipe = Pipeline::spawn(
+            1,
+            NeverDrainsSink {
+                cancel: cancel.clone(),
+                started: started.clone(),
+            },
+        )
+        .expect("spawn should succeed");
+        // First send: consumer recv()s it and wedges in apply.
+        pipe.send(0u64).expect("first send hands off to consumer");
+        wait_for_started(&started, Duration::from_secs(2));
+        // Second send: lands in the depth=1 buffer slot, consumer
+        // can't pick it up because it's wedged in apply. Channel now
+        // full from the producer's perspective.
+        pipe.send(1u64).expect("second send fills the buffer");
+
+        let halt = crate::halt::Halt::new();
+        let start = Instant::now();
+        let res = pipe.send_with_halt(99u64, &halt, Duration::from_millis(200));
+        let elapsed = start.elapsed();
+
+        // Release the leaked consumer so the test process winds down.
+        cancel.store(true, Ordering::SeqCst);
+        let _ = pipe.finish();
+
+        assert!(matches!(res, Err(99)), "expected item returned on deadline");
+        assert!(
+            elapsed >= Duration::from_millis(150),
+            "deadline returned too early: {elapsed:?}"
+        );
+        assert!(
+            elapsed < Duration::from_secs(2),
+            "deadline blew past tolerance: {elapsed:?}"
+        );
+    }
+
+    #[test]
+    fn send_with_halt_returns_item_on_halt() {
+        // Same setup, but the halt fires before the deadline elapses.
+        // The send loop must observe the halt within ~50 ms (the
+        // SEND_POLL_INTERVAL) and return the item.
+        let cancel = Arc::new(std::sync::atomic::AtomicBool::new(false));
+        let started = Arc::new(std::sync::atomic::AtomicBool::new(false));
+        let pipe = Pipeline::spawn(
+            1,
+            NeverDrainsSink {
+                cancel: cancel.clone(),
+                started: started.clone(),
+            },
+        )
+        .expect("spawn should succeed");
+        pipe.send(0u64).expect("first send hands off to consumer");
+        wait_for_started(&started, Duration::from_secs(2));
+        pipe.send(1u64).expect("second send fills the buffer");
+
+        let halt = crate::halt::Halt::new();
+        let halt2 = halt.clone();
+        std::thread::spawn(move || {
+            std::thread::sleep(Duration::from_millis(100));
+            halt2.cancel();
+        });
+
+        let start = Instant::now();
+        let res = pipe.send_with_halt(7u64, &halt, Duration::from_secs(10));
+        let elapsed = start.elapsed();
+
+        cancel.store(true, Ordering::SeqCst);
+        let _ = pipe.finish();
+
+        assert!(matches!(res, Err(7)), "expected item returned on halt");
+        assert!(
+            elapsed < Duration::from_secs(2),
+            "halt observation took too long: {elapsed:?}"
+        );
+    }
+
+    #[test]
+    fn finish_with_halt_returns_halted_when_consumer_wedged() {
+        // Consumer wedges on the first apply; halt fires; finish
+        // returns the documented "pipeline join halted" error rather
+        // than blocking forever.
+        let cancel = Arc::new(std::sync::atomic::AtomicBool::new(false));
+        let started = Arc::new(std::sync::atomic::AtomicBool::new(false));
+        let pipe = Pipeline::spawn(
+            DEFAULT_PIPELINE_DEPTH,
+            NeverDrainsSink {
+                cancel: cancel.clone(),
+                started: started.clone(),
+            },
+        )
+        .expect("spawn should succeed");
+        pipe.send(0u64).expect("seed item the consumer wedges on");
+        wait_for_started(&started, Duration::from_secs(2));
+
+        let halt = crate::halt::Halt::new();
+        let halt2 = halt.clone();
+        std::thread::spawn(move || {
+            std::thread::sleep(Duration::from_millis(400));
+            halt2.cancel();
+        });
+
+        let start = Instant::now();
+        let res = pipe.finish_with_halt(Some(&halt));
+        let elapsed = start.elapsed();
+
+        // Release the leaked consumer so the test process exits cleanly.
+        cancel.store(true, Ordering::SeqCst);
+
+        match res {
+            Err(Error::IoError { source }) => {
+                assert!(
+                    source.to_string().contains("pipeline join halted"),
+                    "expected halt-prefix error, got: {source}"
+                );
+            }
+            other => panic!("expected Err(IoError) halted, got {other:?}"),
+        }
+        // Bailed out within ~1 second of the halt firing (worst case
+        // one POLL_INTERVAL = 250 ms of slack).
+        assert!(
+            elapsed < Duration::from_secs(2),
+            "halt observation took too long: {elapsed:?}"
+        );
+    }
+
+    #[test]
+    fn finish_with_halt_happy_path_returns_output() {
+        // No halt token, sink completes normally — finish_with_halt
+        // must return the same Output that `finish` would.
+        let pipe = Pipeline::spawn(DEFAULT_PIPELINE_DEPTH, SumSink { total: 0 })
+            .expect("spawn should succeed");
+        for i in 0..10u64 {
+            pipe.send(i).expect("send should succeed");
+        }
+        let total = pipe
+            .finish_with_halt(None)
+            .expect("happy-path finish_with_halt should succeed");
+        assert_eq!(total, (0..10u64).sum::<u64>());
+    }
+}

src/io/platform_macos.rs

@@ -0,0 +1,38 @@
+//! Shared macOS `fcntl(F_PREALLOCATE)` definitions.
+//!
+//! The `libc` crate doesn't expose these symbols across all macOS SDK
+//! versions, so we define them locally with values from
+//! `/usr/include/sys/fcntl.h`. Two call sites (
+//! [`crate::io::writeback_file`] and [`crate::io::sink::preallocate`])
+//! need the same constants and `fstore_t` layout — keeping a single
+//! source of truth here prevents the two copies from drifting.
+//!
+//! Module-level cfg gate lives in the parent (`io/mod.rs`); this file
+//! is only compiled on macOS, so no inner `#![cfg]` is needed.
+
+/// `fcntl(F_PREALLOCATE)` command number from `sys/fcntl.h`.
+pub(crate) const F_PREALLOCATE: libc::c_int = 42;
+
+/// Anchor preallocation at the current physical EOF.
+pub(crate) const F_PEOFPOSMODE: libc::c_int = 3;
+
+/// Prefer a contiguous allocation. Try this first; on `EINVAL` (no
+/// contiguous run of that size), fall back to `F_ALLOCATEALL`.
+pub(crate) const F_ALLOCATECONTIG: libc::c_uint = 0x0000_0002;
+
+/// Allow non-contiguous allocation. Stronger guarantee than just
+/// asking for `F_ALLOCATECONTIG` because the kernel will piece
+/// together fragments rather than failing.
+pub(crate) const F_ALLOCATEALL: libc::c_uint = 0x0000_0004;
+
+/// `fstore_t` from `sys/fcntl.h`. `repr(C)` because we hand it to
+/// `fcntl(F_PREALLOCATE)` which writes through the pointer.
+#[repr(C)]
+#[derive(Clone, Copy)]
+pub(crate) struct Fstore {
+    pub fst_flags: libc::c_uint,
+    pub fst_posmode: libc::c_int,
+    pub fst_offset: libc::off_t,
+    pub fst_length: libc::off_t,
+    pub fst_bytesalloc: libc::off_t,
+}

src/io/sink/local_file.rs

@@ -0,0 +1,162 @@
+//! `LocalFileSink` — `BufWriter<File>` for the common local-disk case.
+//!
+//! Buffering: 4 MiB internal `BufWriter`. Sized to coalesce the small
+//! per-PES writes that come out of the muxer into kernel-page-aligned
+//! flushes without making the buffer big enough to matter for memory
+//! pressure on a single concurrent rip.
+//!
+//! `Seek` flushes the underlying `BufWriter` first; otherwise a seek
+//! could leapfrog buffered data and silently corrupt the file. This is
+//! the same shape `BufWriter` itself uses when it impls `Seek` in
+//! stdlib, and is necessary for MKV's seek-back operations (cluster
+//! size patch, Cues index, segment header backpatch) to land on the
+//! right offset.
+//!
+//! `RandomAccessSink` is satisfied via the blanket impl in
+//! [`super::mod`]; no explicit impl needed here.
+
+use std::fs::{File, OpenOptions};
+use std::io::{self, BufWriter, Seek, SeekFrom, Write};
+use std::path::Path;
+
+use super::preallocate;
+
+const BUFFER_BYTES: usize = 4 * 1024 * 1024;
+
+/// Random-access write sink for local disks.
+///
+/// Wraps a `BufWriter<File>` with a 4 MiB internal buffer and forwards
+/// `Write`/`Seek` so any call site that previously held a `File` or
+/// `WritebackFile` can drop this in. `finish()` flushes the buffer and
+/// runs `sync_all` on the underlying file so the caller can drop it
+/// without losing data.
+///
+/// Construction always opens the file `create + truncate + read +
+/// write`. `read` is enabled so the same handle can be reused for a
+/// verification re-read after the mux (the existing
+/// `FileSectorSink::create` pattern). On Linux, [`with_size_hint`]
+/// additionally calls `fallocate(FALLOC_FL_KEEP_SIZE)` to pre-reserve
+/// extents.
+///
+/// [`with_size_hint`]: Self::with_size_hint
+pub struct LocalFileSink {
+    inner: BufWriter<File>,
+}
+
+impl LocalFileSink {
+    /// Open `path` for writing, truncating any existing contents.
+    pub fn create(path: &Path) -> io::Result<Self> {
+        let file = OpenOptions::new()
+            .read(true)
+            .write(true)
+            .create(true)
+            .truncate(true)
+            .open(path)?;
+        Ok(Self {
+            inner: BufWriter::with_capacity(BUFFER_BYTES, file),
+        })
+    }
+
+    /// Like [`Self::create`] but additionally calls the per-OS
+    /// preallocate path with `size_bytes`. On Linux this is
+    /// `fallocate(FALLOC_FL_KEEP_SIZE)` so the on-disk extents are
+    /// reserved up front (reducing fragmentation for big sequential
+    /// muxer output); on other OSes it is a no-op today. Failures
+    /// from the preallocate call are non-fatal — the file is still
+    /// returned, just without the size reservation.
+    pub fn with_size_hint(path: &Path, size_bytes: u64) -> io::Result<Self> {
+        let file = OpenOptions::new()
+            .read(true)
+            .write(true)
+            .create(true)
+            .truncate(true)
+            .open(path)?;
+        preallocate::preallocate(&file, size_bytes);
+        Ok(Self {
+            inner: BufWriter::with_capacity(BUFFER_BYTES, file),
+        })
+    }
+
+    /// Drain the internal buffer and `fsync` the underlying file.
+    /// Idempotent with `Drop` (the `BufWriter` also flushes on drop;
+    /// this call additionally surfaces fsync errors to the caller).
+    #[allow(dead_code)] // exposed for parity with WritebackFile::sync_all
+    pub fn sync_all(&mut self) -> io::Result<()> {
+        self.inner.flush()?;
+        self.inner.get_ref().sync_all()
+    }
+}
+
+impl Write for LocalFileSink {
+    fn write(&mut self, buf: &[u8]) -> io::Result<usize> {
+        self.inner.write(buf)
+    }
+
+    fn write_all(&mut self, buf: &[u8]) -> io::Result<()> {
+        self.inner.write_all(buf)
+    }
+
+    fn flush(&mut self) -> io::Result<()> {
+        self.inner.flush()
+    }
+}
+
+impl Seek for LocalFileSink {
+    fn seek(&mut self, from: SeekFrom) -> io::Result<u64> {
+        // Flush before seeking so buffered bytes land at the offset
+        // they were written for, not the new one.
+        self.inner.flush()?;
+        self.inner.get_mut().seek(from)
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use std::io::Read;
+
+    #[test]
+    fn write_seek_roundtrip() {
+        let dir = tempfile::tempdir().unwrap();
+        let p = dir.path().join("rt.bin");
+        let mut s = LocalFileSink::create(&p).unwrap();
+        s.write_all(b"AAAA").unwrap();
+        s.write_all(b"BBBB").unwrap();
+        // Seek back over the second word and overwrite.
+        s.seek(SeekFrom::Start(4)).unwrap();
+        s.write_all(b"CCCC").unwrap();
+        s.sync_all().unwrap();
+        drop(s);
+
+        let mut f = File::open(&p).unwrap();
+        let mut got = Vec::new();
+        f.read_to_end(&mut got).unwrap();
+        assert_eq!(&got[..], b"AAAACCCC");
+    }
+
+    #[test]
+    fn drop_flushes() {
+        let dir = tempfile::tempdir().unwrap();
+        let p = dir.path().join("drop.bin");
+        {
+            let mut s = LocalFileSink::create(&p).unwrap();
+            s.write_all(b"buffered").unwrap();
+            // No explicit flush / sync_all — BufWriter drop runs the
+            // flush and the file should land on disk.
+        }
+        let bytes = std::fs::read(&p).unwrap();
+        assert_eq!(&bytes[..], b"buffered");
+    }
+
+    #[test]
+    fn with_size_hint_creates_writable_file() {
+        let dir = tempfile::tempdir().unwrap();
+        let p = dir.path().join("sz.bin");
+        let mut s = LocalFileSink::with_size_hint(&p, 64 * 1024).unwrap();
+        s.write_all(b"hint-ok").unwrap();
+        s.sync_all().unwrap();
+        drop(s);
+        let bytes = std::fs::read(&p).unwrap();
+        assert_eq!(&bytes[..], b"hint-ok");
+    }
+}

src/io/sink/mod.rs

@@ -0,0 +1,158 @@
+//! Output-sink trait split for the buffering architecture.
+//!
+//! Two traits, one for each capability axis of an output destination:
+//!
+//! - [`SequentialSink`] — anything you can `Write` to in order. Sockets,
+//!   pipes, append-only stores, plain files. Containers that don't need
+//!   seek (M2TS, fMP4, HEVC elementary) target this.
+//! - [`RandomAccessSink`] — everything `SequentialSink` plus a working
+//!   `Seek`. Local files, NFS files, anything with random-write
+//!   semantics. Containers that need backpatch (MKV cluster sizes, Cues
+//!   index, MP4 moov-at-end) target this.
+//!
+//! `RandomAccessSink: SequentialSink` — every random-access sink is
+//! also a valid sequential sink. The muxer is generic over which it
+//! requires (`MkvMux<S: RandomAccessSink>`, `M2tsMux<S: SequentialSink>`)
+//! so an attempt to mux MKV to a network socket is a compile error.
+//!
+//! Buffering policy belongs to the concrete sink, not to a wrapper at
+//! the call site. `LocalFileSink` wraps a `BufWriter<File>` with a
+//! 4 MiB buffer for the common local-disk case; `WritebackFile`
+//! (separate module) wraps a `File` with the adaptive-chunk
+//! `sync_file_range` machinery for the Linux+NFS case.
+
+use std::io::{Seek, Write};
+
+mod local_file;
+mod preallocate;
+mod socket;
+
+pub use local_file::LocalFileSink;
+pub use socket::{SocketSink, UdpSocketSink};
+
+/// Sequential-only write destination. Sockets, pipes, append-only
+/// stores. No seek. Implementations own their write buffering — the
+/// trait does not impose or hide any buffering of its own.
+///
+/// `finish` drains any internal buffering and signals end-of-stream to
+/// the underlying transport (close-write on a socket, flush on a
+/// buffered writer, etc.). The default impl is a no-op; concrete
+/// implementations that need explicit shutdown can override it but the
+/// blanket impl below keeps it optional for adapter types like
+/// `&mut File`.
+pub trait SequentialSink: Write + Send {
+    fn finish(&mut self) -> std::io::Result<()> {
+        Ok(())
+    }
+}
+
+/// Random-access write destination. Local files, NFS files, anything
+/// with a working `Seek`. Inherits the `SequentialSink` contract — a
+/// random-access sink is always usable as a sequential sink.
+pub trait RandomAccessSink: SequentialSink + Seek {}
+
+// Blanket impls so any `Write + Send` type acts as a `SequentialSink`
+// (with default `finish`), and any sink that also impls `Seek` is
+// automatically a `RandomAccessSink`. Keeps call-site ergonomics simple
+// — `&mut File`, `LocalFileSink`, `WritebackFile`, `BufWriter<File>`,
+// and `Cursor<Vec<u8>>` all satisfy the right trait without per-type
+// boilerplate.
+impl<T: Write + Send + ?Sized> SequentialSink for T {}
+impl<T: SequentialSink + Seek + ?Sized> RandomAccessSink for T {}
+
+/// Pick the right `RandomAccessSink` impl for `dest` based on its
+/// filesystem type.
+///
+/// - Linux + NFS path → `WritebackFile` with its adaptive-chunk
+///   sync_file_range machinery and (when supported) `fallocate` size
+///   hint.
+/// - everything else → [`LocalFileSink`] over `BufWriter<File>`. On
+///   non-Linux there is no `WritebackFile` machinery to opt into, and
+///   on local Linux the kernel's default writeback policy is already
+///   fine.
+///
+/// `size_hint`, when present, is forwarded to the per-OS preallocate
+/// path (`fallocate(KEEP_SIZE)` on Linux, `F_PREALLOCATE` on macOS when
+/// implemented, no-op elsewhere).
+///
+/// Returns a boxed trait object so the call site (mux construction)
+/// stays agnostic of which concrete sink got picked.
+#[allow(dead_code)] // wiring to mux::resolve is a follow-up commit
+pub fn open_for_mkv(
+    dest: &std::path::Path,
+    size_hint: Option<u64>,
+) -> std::io::Result<Box<dyn RandomAccessSink>> {
+    #[cfg(not(target_os = "linux"))]
+    use crate::platform::fs_type::detect;
+    #[cfg(target_os = "linux")]
+    use crate::platform::fs_type::{FsType, detect};
+
+    #[cfg(target_os = "linux")]
+    {
+        if detect(dest) == FsType::Nfs {
+            let wf = match size_hint {
+                Some(n) => crate::io::WritebackFile::create_with_size_hint(dest, n)?,
+                None => crate::io::WritebackFile::create(dest)?,
+            };
+            return Ok(Box::new(wf));
+        }
+    }
+    // Silence the unused-binding warning on non-Linux where the only
+    // branch above is cfg-gated out.
+    #[cfg(not(target_os = "linux"))]
+    {
+        let _ = detect(dest);
+    }
+
+    let sink = match size_hint {
+        Some(n) => LocalFileSink::with_size_hint(dest, n)?,
+        None => LocalFileSink::create(dest)?,
+    };
+    Ok(Box::new(sink))
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use std::fs::File;
+
+    // Type-level assertion: the blanket impls cover the shapes we care
+    // about. These functions never run; they just have to type-check.
+    fn _assert_file_is_sequential(_: &mut dyn SequentialSink) {}
+    fn _assert_file_is_random_access(_: &mut dyn RandomAccessSink) {}
+
+    #[test]
+    fn blanket_impls_cover_file_and_localfilesink() {
+        // `File` directly via blanket impls.
+        let dir = tempfile::tempdir().unwrap();
+        let mut f = File::create(dir.path().join("a.bin")).unwrap();
+        _assert_file_is_sequential(&mut f);
+        _assert_file_is_random_access(&mut f);
+
+        // `LocalFileSink` ditto.
+        let mut s = LocalFileSink::create(&dir.path().join("b.bin")).unwrap();
+        _assert_file_is_sequential(&mut s);
+        _assert_file_is_random_access(&mut s);
+
+        // `WritebackFile` — confirms the Phase 1 type still satisfies
+        // the trait via the blanket impl without needing an explicit
+        // `impl RandomAccessSink for WritebackFile {}`.
+        let mut wf = crate::io::WritebackFile::create(&dir.path().join("c.bin")).unwrap();
+        _assert_file_is_sequential(&mut wf);
+        _assert_file_is_random_access(&mut wf);
+    }
+
+    #[test]
+    fn open_for_mkv_returns_a_random_access_sink() {
+        let dir = tempfile::tempdir().unwrap();
+        let p = dir.path().join("c.bin");
+        let mut sink = open_for_mkv(&p, Some(64 * 1024)).unwrap();
+        use std::io::{Seek, SeekFrom, Write};
+        sink.write_all(b"hello").unwrap();
+        sink.seek(SeekFrom::Start(0)).unwrap();
+        sink.finish().unwrap();
+        drop(sink);
+        let bytes = std::fs::read(&p).unwrap();
+        assert_eq!(&bytes[..5], b"hello");
+    }
+}

src/io/sink/preallocate/linux.rs

@@ -0,0 +1,20 @@
+//! Linux `fallocate(FALLOC_FL_KEEP_SIZE)` preallocation.
+//!
+//! `KEEP_SIZE` reserves extents without changing the apparent file
+//! length, which matches the muxer's expectation that writes still grow
+//! the file naturally.
+
+use std::fs::File;
+#[cfg(unix)]
+use std::os::unix::io::AsRawFd;
+
+pub(super) fn preallocate_impl(file: &File, size_bytes: u64) {
+    let fd = file.as_raw_fd();
+    // FALLOC_FL_KEEP_SIZE = 0x01.
+    let rc = unsafe { libc::fallocate(fd, libc::FALLOC_FL_KEEP_SIZE, 0, size_bytes as i64) };
+    tracing::debug!(
+        target: "mux",
+        "LocalFileSink fallocate size_hint={size_bytes} rc={rc} ok={}",
+        rc == 0
+    );
+}

src/io/sink/preallocate/macos.rs

@@ -0,0 +1,34 @@
+//! macOS `F_PREALLOCATE` extent reservation.
+//!
+//! `fcntl(F_PREALLOCATE)` with `F_ALLOCATECONTIG` first (try for a
+//! contiguous run) and fall back to `F_ALLOCATEALL` (non-contig OK).
+//! Reported file size is unchanged — the muxer's writes still grow it.
+
+use std::fs::File;
+use std::os::unix::io::AsRawFd;
+
+use crate::io::platform_macos::{
+    F_ALLOCATEALL, F_ALLOCATECONTIG, F_PEOFPOSMODE, F_PREALLOCATE, Fstore,
+};
+
+pub(super) fn preallocate_impl(file: &File, size_bytes: u64) {
+    let fd = file.as_raw_fd();
+    let mut store = Fstore {
+        fst_flags: F_ALLOCATECONTIG,
+        fst_posmode: F_PEOFPOSMODE,
+        fst_offset: 0,
+        fst_length: size_bytes as libc::off_t,
+        fst_bytesalloc: 0,
+    };
+    let mut rc = unsafe { libc::fcntl(fd, F_PREALLOCATE, &mut store as *mut Fstore) };
+    if rc == -1 {
+        // Fall back to non-contiguous.
+        store.fst_flags = F_ALLOCATEALL;
+        rc = unsafe { libc::fcntl(fd, F_PREALLOCATE, &mut store as *mut Fstore) };
+    }
+    tracing::debug!(
+        target: "mux",
+        "LocalFileSink F_PREALLOCATE size_hint={size_bytes} rc={rc} bytesalloc={}",
+        store.fst_bytesalloc
+    );
+}

src/io/sink/preallocate/mod.rs

@@ -0,0 +1,27 @@
+//! Per-OS extent preallocation. Best-effort; failures are logged at
+//! debug and otherwise swallowed because the file is still usable
+//! without the size reservation — only large-file fragmentation gets
+//! marginally worse.
+
+use std::fs::File;
+
+#[cfg(target_os = "linux")]
+mod linux;
+#[cfg(target_os = "macos")]
+mod macos;
+#[cfg(not(any(target_os = "linux", target_os = "macos")))]
+mod other;
+
+#[cfg(target_os = "linux")]
+use linux::preallocate_impl;
+#[cfg(target_os = "macos")]
+use macos::preallocate_impl;
+#[cfg(not(any(target_os = "linux", target_os = "macos")))]
+use other::preallocate_impl;
+
+/// Reserve `size_bytes` of disk space for `file`'s on-disk extents.
+/// Reported file size is unchanged — writes still grow the file
+/// naturally; only the allocator's extent map is primed.
+pub(super) fn preallocate(file: &File, size_bytes: u64) {
+    preallocate_impl(file, size_bytes);
+}

src/io/sink/preallocate/other.rs

@@ -0,0 +1,10 @@
+//! Fallback preallocate impl. No-op.
+
+use std::fs::File;
+
+pub(super) fn preallocate_impl(_file: &File, size_bytes: u64) {
+    tracing::debug!(
+        target: "mux",
+        "LocalFileSink preallocate size_hint={size_bytes} skipped (no platform impl)"
+    );
+}

src/io/sink/socket.rs

@@ -0,0 +1,278 @@
+//! TCP / UDP socket sinks (sequential-only).
+//!
+//! [`SocketSink`] wraps a `TcpStream` in a 1 MiB `BufWriter`. Constructor
+//! tunes `SO_SNDBUF` to a caller hint when provided. `finish()` flushes
+//! the buffer then `shutdown(Write)`s the socket so the peer sees clean
+//! end-of-stream.
+//!
+//! [`UdpSocketSink`] wraps a connected `UdpSocket`. Each `write` call
+//! emits exactly one datagram — the caller is responsible for packetizing
+//! to a reasonable MTU (188 × 7 = 1316 bytes for MPEG-TS-over-UDP is the
+//! conventional choice). `finish()` is a no-op; UDP has no end-of-stream
+//! marker.
+//!
+//! Both types satisfy [`SequentialSink`] via the blanket impl in
+//! `super::mod`. Neither implements `Seek`, so neither satisfies
+//! [`RandomAccessSink`] — using one with `MkvMux` is a compile error,
+//! which is the design intent.
+//!
+//! [`SequentialSink`]: super::SequentialSink
+//! [`RandomAccessSink`]: super::RandomAccessSink
+
+use std::io::{self, BufWriter, Write};
+use std::net::{Shutdown, TcpStream, ToSocketAddrs, UdpSocket};
+
+/// `BufWriter` capacity for [`SocketSink`]. 1 MiB matches the typical
+/// kernel send-buffer ceiling and keeps small-write amplification from
+/// containers (TS = 188-byte packets, fMP4 fragment headers = ~100 bytes)
+/// from translating into syscall storms.
+const TCP_BUF_CAPACITY: usize = 1024 * 1024;
+
+/// Sequential-only sink over a TCP connection.
+///
+/// Wraps a `BufWriter<TcpStream>`; the inner `TcpStream` is kept as a
+/// clone so [`finish`](Self::finish) can call `shutdown(Write)` after
+/// flushing the buffer (the buffered writer doesn't expose the socket
+/// directly).
+pub struct SocketSink {
+    /// Buffered write half. All payload bytes go through this.
+    buf: BufWriter<TcpStream>,
+    /// Shutdown handle — clone of the socket inside `buf`. Used only by
+    /// `finish()` for `shutdown(Write)`; never read or written through.
+    shutdown_handle: TcpStream,
+}
+
+impl SocketSink {
+    /// Open a TCP connection to `addr` and wrap it for sequential
+    /// writing. `sndbuf_bytes`, when present, is forwarded to
+    /// `setsockopt(SO_SNDBUF)` as a kernel hint — the OS may clamp it.
+    ///
+    /// `addr` accepts anything `ToSocketAddrs` does: `"192.0.2.1:1234"`,
+    /// `("host", 1234)`, a `SocketAddr`, etc.
+    pub fn connect<A: ToSocketAddrs>(addr: A, sndbuf_bytes: Option<usize>) -> io::Result<Self> {
+        let stream = TcpStream::connect(addr)?;
+        // `set_nodelay(true)` keeps small writes (TS packet trains, fMP4
+        // moof headers) from sitting in Nagle's algorithm until the buffer
+        // fills. The BufWriter already absorbs syscall overhead; Nagle
+        // would just add latency without coalescing more.
+        stream.set_nodelay(true)?;
+        if let Some(n) = sndbuf_bytes {
+            set_send_buffer(&stream, n)?;
+        }
+        let shutdown_handle = stream.try_clone()?;
+        Ok(Self {
+            buf: BufWriter::with_capacity(TCP_BUF_CAPACITY, stream),
+            shutdown_handle,
+        })
+    }
+}
+
+impl Write for SocketSink {
+    fn write(&mut self, buf: &[u8]) -> io::Result<usize> {
+        self.buf.write(buf)
+    }
+    fn flush(&mut self) -> io::Result<()> {
+        self.buf.flush()
+    }
+}
+
+impl SocketSink {
+    /// Drain the BufWriter and `shutdown(Write)` the underlying socket
+    /// so the peer sees a clean EOF.
+    ///
+    /// Note: [`SequentialSink::finish`](super::SequentialSink::finish)'s
+    /// blanket-impl default is a no-op. Trait-object call sites that
+    /// need socket shutdown should call this inherent method directly
+    /// before dropping the sink, or hold the concrete `SocketSink` type
+    /// (typical pattern: each muxer's `finish()` calls the appropriate
+    /// inherent close method on its captured concrete sink).
+    pub fn finish(&mut self) -> io::Result<()> {
+        self.buf.flush()?;
+        // `shutdown(Write)` signals clean EOF to the peer. Errors here
+        // are non-fatal — the connection may have already been torn down
+        // by the peer — but we surface them so callers can log.
+        self.shutdown_handle.shutdown(Shutdown::Write)
+    }
+}
+
+/// Sequential-only sink over a connected UDP socket.
+///
+/// Each [`write`](Write::write) call sends exactly one datagram. The
+/// caller is responsible for splitting payload at packet boundaries —
+/// for MPEG-TS this means 7 × 188 = 1316 bytes per datagram, the
+/// industry standard for MPEG-TS-over-UDP. No buffering happens here;
+/// adding it would silently merge datagrams.
+///
+/// `finish()` is a no-op: UDP has no end-of-stream marker. Closing the
+/// socket happens on drop.
+pub struct UdpSocketSink {
+    socket: UdpSocket,
+}
+
+impl UdpSocketSink {
+    /// Bind a local UDP socket to an ephemeral port and `connect` it to
+    /// `peer`. `connect` doesn't open a connection — it just fixes the
+    /// peer address so subsequent `send` calls don't need to repeat it,
+    /// and so receive-side filtering rejects packets from other sources.
+    ///
+    /// `sndbuf_bytes`, when present, is a hint to `SO_SNDBUF`.
+    pub fn connect<A: ToSocketAddrs>(peer: A, sndbuf_bytes: Option<usize>) -> io::Result<Self> {
+        // Bind to all-zeros / any port. The kernel picks an ephemeral
+        // source port and the source IP at first send.
+        let socket = UdpSocket::bind("0.0.0.0:0")?;
+        socket.connect(peer)?;
+        if let Some(n) = sndbuf_bytes {
+            set_udp_send_buffer(&socket, n)?;
+        }
+        Ok(Self { socket })
+    }
+}
+
+impl Write for UdpSocketSink {
+    fn write(&mut self, buf: &[u8]) -> io::Result<usize> {
+        // `send` writes the entire datagram or fails — no partial sends
+        // for UDP. Match `Write::write`'s contract by reporting bytes
+        // accepted.
+        self.socket.send(buf)
+    }
+    fn flush(&mut self) -> io::Result<()> {
+        Ok(())
+    }
+}
+
+impl UdpSocketSink {
+    /// No-op — UDP has no end-of-stream marker. Provided for parity
+    /// with [`SocketSink::finish`] so call sites can treat them uniformly.
+    pub fn finish(&mut self) -> io::Result<()> {
+        Ok(())
+    }
+}
+
+// ── Platform `SO_SNDBUF` tuning ────────────────────────────────────────────
+//
+// std's `TcpStream` / `UdpSocket` don't expose `SO_SNDBUF`. We drop to
+// libc on Linux + macOS (the libc-dep targets in Cargo.toml). On other
+// targets the hint is silently ignored — the socket still works, the
+// kernel just picks its own send-buffer size.
+
+#[cfg(any(target_os = "linux", target_os = "macos"))]
+fn set_send_buffer(stream: &TcpStream, bytes: usize) -> io::Result<()> {
+    use std::os::unix::io::AsRawFd;
+    setsockopt_sndbuf(stream.as_raw_fd(), bytes)
+}
+
+#[cfg(any(target_os = "linux", target_os = "macos"))]
+fn set_udp_send_buffer(socket: &UdpSocket, bytes: usize) -> io::Result<()> {
+    use std::os::unix::io::AsRawFd;
+    setsockopt_sndbuf(socket.as_raw_fd(), bytes)
+}
+
+#[cfg(not(any(target_os = "linux", target_os = "macos")))]
+fn set_send_buffer(_stream: &TcpStream, _bytes: usize) -> io::Result<()> {
+    // Non-Linux-non-macOS targets aren't in Cargo.toml's libc dep list;
+    // silently ignore the hint rather than failing the connect. Callers
+    // can detect via the lack of an explicit "sndbuf applied" signal
+    // (not provided, intentionally — this is a hint, not a guarantee).
+    Ok(())
+}
+
+#[cfg(not(any(target_os = "linux", target_os = "macos")))]
+fn set_udp_send_buffer(_socket: &UdpSocket, _bytes: usize) -> io::Result<()> {
+    Ok(())
+}
+
+#[cfg(any(target_os = "linux", target_os = "macos"))]
+fn setsockopt_sndbuf(fd: std::os::unix::io::RawFd, bytes: usize) -> io::Result<()> {
+    // Clamp into c_int range; SO_SNDBUF takes an `int` argument.
+    let want: libc::c_int = bytes.try_into().unwrap_or(libc::c_int::MAX);
+    let ret = unsafe {
+        libc::setsockopt(
+            fd,
+            libc::SOL_SOCKET,
+            libc::SO_SNDBUF,
+            &want as *const _ as *const libc::c_void,
+            std::mem::size_of::<libc::c_int>() as libc::socklen_t,
+        )
+    };
+    if ret != 0 {
+        return Err(io::Error::last_os_error());
+    }
+    Ok(())
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use std::io::Read;
+    use std::net::{TcpListener, UdpSocket};
+    use std::thread;
+
+    /// Bind a listener, accept on a thread, return (listener_addr,
+    /// accepted-bytes future via JoinHandle).
+    #[test]
+    fn socket_sink_round_trips_bytes() {
+        let listener = TcpListener::bind("127.0.0.1:0").unwrap();
+        let addr = listener.local_addr().unwrap();
+        let accept = thread::spawn(move || {
+            let (mut sock, _) = listener.accept().unwrap();
+            let mut buf = Vec::new();
+            sock.read_to_end(&mut buf).unwrap();
+            buf
+        });
+
+        let mut sink = SocketSink::connect(addr, Some(256 * 1024)).unwrap();
+        // Write enough to overflow the BufWriter at least once, then a
+        // tail that lives in the buffer until `finish` flushes.
+        let big: Vec<u8> = (0..(2 * TCP_BUF_CAPACITY))
+            .map(|i| (i & 0xff) as u8)
+            .collect();
+        sink.write_all(&big).unwrap();
+        sink.write_all(b"tail\n").unwrap();
+        sink.finish().unwrap();
+        drop(sink);
+
+        let received = accept.join().unwrap();
+        assert_eq!(received.len(), big.len() + 5);
+        assert_eq!(&received[..big.len()], &big[..]);
+        assert_eq!(&received[big.len()..], b"tail\n");
+    }
+
+    #[test]
+    fn socket_sink_is_sequential_only() {
+        // Compile-time assertion via dyn — if this ever started
+        // satisfying `RandomAccessSink`, the trait split would be broken.
+        fn _assert_seq(_: &mut dyn super::super::SequentialSink) {}
+        let listener = TcpListener::bind("127.0.0.1:0").unwrap();
+        let addr = listener.local_addr().unwrap();
+        let _accept = thread::spawn(move || {
+            let _ = listener.accept();
+        });
+        let mut sink = SocketSink::connect(addr, None).unwrap();
+        _assert_seq(&mut sink);
+        // The negative is harder to assert directly (no `is_not<T>`),
+        // but `SocketSink` does not impl `Seek`, so it can't unify with
+        // `RandomAccessSink`'s super-bound. The Phase 2 blanket impl
+        // `impl<T: SequentialSink + Seek> RandomAccessSink for T {}` thus
+        // excludes it by construction.
+    }
+
+    #[test]
+    fn udp_socket_sink_delivers_datagrams() {
+        let receiver = UdpSocket::bind("127.0.0.1:0").unwrap();
+        receiver
+            .set_read_timeout(Some(std::time::Duration::from_secs(2)))
+            .unwrap();
+        let addr = receiver.local_addr().unwrap();
+        let mut sink = UdpSocketSink::connect(addr, Some(128 * 1024)).unwrap();
+
+        sink.write_all(&[1, 2, 3, 4, 5]).unwrap();
+        sink.write_all(&[9, 9, 9]).unwrap();
+        sink.finish().unwrap();
+
+        let mut buf = [0u8; 64];
+        let n1 = receiver.recv(&mut buf).unwrap();
+        assert_eq!(&buf[..n1], &[1, 2, 3, 4, 5]);
+        let n2 = receiver.recv(&mut buf).unwrap();
+        assert_eq!(&buf[..n2], &[9, 9, 9]);
+    }
+}

src/io/writeback.rs

@@ -0,0 +1,17 @@
+//! Per-platform writeback pipeline. On Linux, drains dirty pages
+//! continuously at chunk granularity to keep the kernel's writeback
+//! queue bounded. On macOS and Windows, a no-op stub.
+//!
+//! The platform decision lives entirely in this file (the cfg-gated
+//! `pub use` below). Callers — and `DiskWriter` itself — are
+//! platform-independent.
+
+#[cfg(target_os = "linux")]
+mod linux;
+#[cfg(not(target_os = "linux"))]
+mod noop;
+
+#[cfg(target_os = "linux")]
+pub(super) use linux::WritebackPipeline;
+#[cfg(not(target_os = "linux"))]
+pub(super) use noop::WritebackPipeline;

src/io/writeback/linux.rs

@@ -0,0 +1,459 @@
+//! Linux writeback pipeline using `sync_file_range` + `posix_fadvise`.
+//!
+//! Pathology this fixes: the kernel's default `vm.dirty_ratio` (~20 %
+//! of RAM) lets dirty pages accumulate to hundreds of MB during a
+//! big sequential write, then bursts a flush at 99 % disk utilisation.
+//! While the burst runs, app writes block on the writeback queue —
+//! observed empirically as instantaneous speed dropping from ~15 MB/s
+//! to ~1 MB/s every ~30 s during a Pass 1 sweep.
+//!
+//! Strategy: every `chunk_bytes` of new sequential output, kick async
+//! writeback (`SYNC_FILE_RANGE_WRITE`) on the just-completed chunk and
+//! finalise the *previous* chunk via `WAIT_AFTER` + `posix_fadvise
+//! (DONTNEED)`. By the time we finalise, that previous chunk has had
+//! a full chunk's worth of work to flush — the wait is near-instant.
+//! Dirty cache stays bounded at ~2 × `chunk_bytes` and writes drain
+//! continuously instead of in bursts.
+//!
+//! The chunk size is adaptive: we measure the elapsed time of the
+//! `WAIT_AFTER` call over a rolling window of the last 16 chunks and
+//! resize the chunk based on the p95. Slow storage (NFS, network
+//! shares, HDD) sees larger chunks to amortise per-chunk overhead;
+//! fast storage (NVMe) sees smaller chunks to keep cache pressure
+//! tight. Bounds: [4 MiB, 256 MiB].
+//!
+//! ## NFS escape hatch
+//!
+//! `sync_file_range(WAIT_AFTER)` on an NFS-mounted file can block
+//! indefinitely waiting for the server's commit ack. If the server
+//! never acks (network partition, server-side hang, slow commit), the
+//! syscall never returns and the consumer thread is stuck inside the
+//! kernel — `/api/stop` can't reach it because halt is cooperative.
+//!
+//! When `fstatfs` reports the file lives on an NFS mount
+//! (`f_type == NFS_SUPER_MAGIC`), the pipeline skips the WAIT_AFTER +
+//! `posix_fadvise(DONTNEED)` dance entirely. NFS clients have their
+//! own buffering and commit semantics that handle dirty-page bounds
+//! without us forcing the issue. The async `SYNC_FILE_RANGE_WRITE`
+//! kickoff still runs (non-blocking by spec) so writeback still gets
+//! a nudge.
+//!
+//! ## Defence in depth: WAIT_AFTER timeout
+//!
+//! Even on local storage, a degraded disk or odd filesystem driver
+//! could in principle wedge inside WAIT_AFTER. Each WAIT_AFTER call
+//! runs on a worker thread with a 30s recv_timeout on its result
+//! channel. On timeout we log a loud error, set a `degraded` flag,
+//! and from then on skip WAIT_AFTER + DONTNEED for the rest of the
+//! pipeline's life (same shape as the NFS path). The worker thread
+//! is intentionally leaked — it unwinds whenever the syscall
+//! eventually returns or the process exits. The mux continues; the
+//! original dirty-burst pathology re-emerges but the rip can still
+//! finish instead of freezing.
+
+use std::collections::VecDeque;
+use std::fs::File;
+use std::os::unix::io::{AsRawFd, RawFd};
+use std::sync::Arc;
+use std::sync::atomic::{AtomicBool, Ordering};
+use std::time::{Duration, Instant};
+
+const ADAPTIVE_WINDOW: usize = 16;
+const CHUNK_BYTES_MIN: u64 = 4 * 1024 * 1024;
+const CHUNK_BYTES_MAX: u64 = 256 * 1024 * 1024;
+const ADAPTIVE_GROW_MS: u64 = 200;
+const ADAPTIVE_SHRINK_MS: u64 = 20;
+/// Every N chunks, emit a `debug!` snapshot of the current chunk
+/// size so operators tailing the log can see where the autoscaler
+/// settled.
+const SIZE_LOG_INTERVAL: u64 = 32;
+/// Hard upper bound on a single `sync_file_range(WAIT_AFTER)` call.
+/// Beyond this we declare the pipeline degraded and stop calling
+/// WAIT_AFTER for the rest of its life.
+const WAIT_AFTER_TIMEOUT: Duration = Duration::from_secs(30);
+
+pub(crate) struct WritebackPipeline {
+    /// Aliases the wrapping `WritebackFile::file`. Only valid for the
+    /// lifetime of that struct — moving the `File` independently
+    /// would silently UAF this fd. The pipeline is a private field of
+    /// `WritebackFile` and never exposed outside that wrapper, which
+    /// is what keeps the alias sound.
+    fd: RawFd,
+    chunk_bytes: u64,
+    last_flush_pos: u64,
+    pending: Option<(u64, u64)>,
+    /// Rolling window of recent `WAIT_AFTER` elapsed_ms measurements.
+    wait_after_window: VecDeque<u64>,
+    /// Count of chunks emitted (used to space out periodic
+    /// `debug!` size snapshots).
+    chunk_count: u64,
+    /// True when the underlying file is on an NFS mount. NFS makes
+    /// WAIT_AFTER unsafe (can block forever on missing server ack), so
+    /// we skip it entirely and let the NFS client handle commit on
+    /// close.
+    is_nfs: bool,
+    /// Set the first time WAIT_AFTER exceeds [`WAIT_AFTER_TIMEOUT`].
+    /// Once set, behaviour matches the NFS path for the rest of the
+    /// pipeline's life. Wrapped in `Arc` only because both this
+    /// struct and the spawned worker thread (which itself doesn't
+    /// touch the flag) share-via-fd patterns might one day need it;
+    /// today it's effectively a single-owner cell — the `Arc` shape
+    /// keeps the door open for moving the read side into a worker
+    /// without re-plumbing types.
+    degraded: Arc<AtomicBool>,
+}
+
+impl WritebackPipeline {
+    /// Construct a pipeline aliasing `file`'s file descriptor. The
+    /// returned `WritebackPipeline` MUST be dropped before `file`
+    /// itself, or kept inside the same struct that owns `file` — the
+    /// alias is unchecked.
+    pub(crate) fn new(file: &File, start_pos: u64, chunk_bytes: u64) -> Self {
+        let fd = file.as_raw_fd();
+        let is_nfs = detect_nfs(fd);
+        tracing::info!(
+            target: "mux",
+            "WritebackPipeline fd={fd} is_nfs={is_nfs} chunk_bytes={chunk_bytes} strategy={}",
+            if is_nfs { "nfs-skip-wait" } else { "wait+dontneed" }
+        );
+        Self {
+            fd,
+            chunk_bytes,
+            last_flush_pos: start_pos,
+            pending: None,
+            wait_after_window: VecDeque::with_capacity(ADAPTIVE_WINDOW),
+            chunk_count: 0,
+            is_nfs,
+            degraded: Arc::new(AtomicBool::new(false)),
+        }
+    }
+
+    /// True if we should bypass the WAIT_AFTER + DONTNEED finalisation
+    /// step. NFS always bypasses; local storage bypasses once the
+    /// pipeline has flipped to degraded after a WAIT_AFTER timeout.
+    #[inline]
+    fn skip_wait(&self) -> bool {
+        self.is_nfs || self.degraded.load(Ordering::Relaxed)
+    }
+
+    /// Caller advanced the file position to `pos`. If a chunk boundary
+    /// was crossed, kick async writeback for the just-completed chunk
+    /// and finalise the previous one.
+    pub(crate) fn note_progress(&mut self, pos: u64) {
+        if pos < self.last_flush_pos.saturating_add(self.chunk_bytes) {
+            return;
+        }
+        let chunk_off = self.last_flush_pos as i64;
+        let chunk_len = (pos - self.last_flush_pos) as i64;
+        let mut wait_ms: u64 = 0;
+        let mut fadvise_ms: u64 = 0;
+        // Async kickoff for the just-completed chunk runs on every
+        // path (NFS, degraded, normal) — it's nominally non-blocking
+        // by spec and gives the kernel an early hint that this range
+        // is ready to flush.
+        unsafe {
+            libc::sync_file_range(self.fd, chunk_off, chunk_len, libc::SYNC_FILE_RANGE_WRITE);
+        }
+        if let Some((prev_off, prev_len)) = self.pending.take() {
+            if self.skip_wait() {
+                // NFS branch (or degraded fallback after a prior
+                // timeout): the WAIT_AFTER + DONTNEED dance is what
+                // hangs on NFS — skip it. We still advance `pending`
+                // so the next call has a stable cycle.
+            } else {
+                // Normal local-storage branch with belt-and-braces
+                // timeout. If WAIT_AFTER hangs > WAIT_AFTER_TIMEOUT
+                // we mark the pipeline degraded, log a loud error,
+                // and fall through to the skip path on subsequent
+                // calls.
+                match wait_after_with_timeout(self.fd, prev_off, prev_len) {
+                    Some(ms) => {
+                        wait_ms = ms;
+                        let t_fadv = Instant::now();
+                        unsafe {
+                            libc::posix_fadvise(
+                                self.fd,
+                                prev_off as i64,
+                                prev_len as i64,
+                                libc::POSIX_FADV_DONTNEED,
+                            );
+                        }
+                        fadvise_ms = t_fadv.elapsed().as_millis() as u64;
+                        self.record_wait(wait_ms);
+                    }
+                    None => {
+                        // Timeout branch: switch to NFS-style skip
+                        // for the rest of the pipeline's life. Do
+                        // NOT call DONTNEED — if WAIT_AFTER hasn't
+                        // returned, the pages aren't safely flushed.
+                        self.degraded.store(true, Ordering::Relaxed);
+                        tracing::error!(
+                            target: "mux",
+                            "WritebackPipeline WAIT_AFTER timed out after {}s on chunk off={} len={}, marking writeback degraded (subsequent chunks will skip WAIT_AFTER + DONTNEED)",
+                            WAIT_AFTER_TIMEOUT.as_secs(),
+                            prev_off,
+                            prev_len
+                        );
+                    }
+                }
+            }
+        }
+        self.pending = Some((chunk_off as u64, chunk_len as u64));
+        self.last_flush_pos = pos;
+        self.chunk_count += 1;
+        tracing::trace!(
+            target: "mux",
+            "WritebackPipeline chunk off={} len={} sync_file_range_ms={wait_ms} fadvise_ms={fadvise_ms} chunk_bytes={} skip_wait={}",
+            chunk_off,
+            chunk_len,
+            self.chunk_bytes,
+            self.skip_wait(),
+        );
+        if self.chunk_count % SIZE_LOG_INTERVAL == 0 {
+            tracing::debug!(
+                target: "mux",
+                "WritebackPipeline chunk_bytes={} after {} chunks is_nfs={} degraded={}",
+                self.chunk_bytes,
+                self.chunk_count,
+                self.is_nfs,
+                self.degraded.load(Ordering::Relaxed),
+            );
+        }
+    }
+
+    /// Push a new `WAIT_AFTER` measurement into the rolling window
+    /// and, if the window is full, adapt `chunk_bytes` based on p95.
+    fn record_wait(&mut self, wait_ms: u64) {
+        if self.wait_after_window.len() == ADAPTIVE_WINDOW {
+            self.wait_after_window.pop_front();
+        }
+        self.wait_after_window.push_back(wait_ms);
+        if self.wait_after_window.len() < ADAPTIVE_WINDOW {
+            return;
+        }
+        // p95 of 16 samples ≈ sorted[14] (5 % of 16 = 0.8 ≈ 1 above).
+        let mut sorted: Vec<u64> = self.wait_after_window.iter().copied().collect();
+        sorted.sort_unstable();
+        let p95 = sorted[14];
+        let old = self.chunk_bytes;
+        let new = if p95 > ADAPTIVE_GROW_MS && self.chunk_bytes < CHUNK_BYTES_MAX {
+            (self.chunk_bytes * 2).min(CHUNK_BYTES_MAX)
+        } else if p95 < ADAPTIVE_SHRINK_MS && self.chunk_bytes > CHUNK_BYTES_MIN {
+            (self.chunk_bytes / 2).max(CHUNK_BYTES_MIN)
+        } else {
+            self.chunk_bytes
+        };
+        if new != old {
+            self.chunk_bytes = new;
+            tracing::info!(
+                target: "mux",
+                "WritebackPipeline adaptive chunk_bytes {} -> {} p95_ms={p95}",
+                old,
+                new
+            );
+        }
+    }
+
+    /// Caller is about to seek away from the current write region.
+    /// Drain any in-flight chunk and reset tracking.
+    pub(crate) fn handle_seek(&mut self, new_pos: u64) {
+        self.finalize();
+        self.last_flush_pos = new_pos;
+    }
+
+    /// Drain any in-flight chunk. Idempotent. Call before `sync_all()`
+    /// or when discarding the pipeline.
+    pub(crate) fn finalize(&mut self) {
+        if let Some((prev_off, prev_len)) = self.pending.take() {
+            tracing::debug!(
+                target: "mux",
+                "WritebackPipeline finalize chunk off={prev_off} len={prev_len} skip_wait={} is_nfs={} degraded={}",
+                self.skip_wait(),
+                self.is_nfs,
+                self.degraded.load(Ordering::Relaxed),
+            );
+            if self.skip_wait() {
+                // NFS / degraded: skip WAIT_AFTER + DONTNEED. close()
+                // / sync_all() handle commit through their normal
+                // paths.
+                return;
+            }
+            match wait_after_with_timeout(self.fd, prev_off, prev_len) {
+                Some(_ms) => unsafe {
+                    libc::posix_fadvise(
+                        self.fd,
+                        prev_off as i64,
+                        prev_len as i64,
+                        libc::POSIX_FADV_DONTNEED,
+                    );
+                },
+                None => {
+                    self.degraded.store(true, Ordering::Relaxed);
+                    tracing::error!(
+                        target: "mux",
+                        "WritebackPipeline finalize WAIT_AFTER timed out after {}s on chunk off={prev_off} len={prev_len}, marking writeback degraded",
+                        WAIT_AFTER_TIMEOUT.as_secs(),
+                    );
+                }
+            }
+        }
+    }
+}
+
+/// Probe whether `fd` lives on an NFS mount. Thin wrapper around
+/// [`crate::platform::fs_type::detect_fd`] so writeback policy and
+/// general-purpose fs-type classification stay in sync (same magic
+/// numbers, same musl-vs-glibc cast handling).
+///
+/// Fails open: any classification other than NFS counts as "not NFS"
+/// (including `Unknown` on `fstatfs` error) — better to run the
+/// normal local-storage path on a misdetected NFS mount and surface
+/// the freeze loudly via [`WAIT_AFTER_TIMEOUT`] than to needlessly
+/// disable writeback bounding on every local file because of a
+/// transient stat error.
+fn detect_nfs(fd: RawFd) -> bool {
+    matches!(
+        crate::platform::fs_type::detect_fd(fd),
+        crate::platform::fs_type::FsType::Nfs
+    )
+}
+
+/// Run `sync_file_range(WAIT_AFTER)` on a worker thread and wait up
+/// to [`WAIT_AFTER_TIMEOUT`] for it to return. `Some(elapsed_ms)` on
+/// success; `None` on timeout. On timeout the worker thread is
+/// 0.20.6 generalizes the worker-thread + recv_timeout pattern into
+/// [`crate::io::bounded::bounded_syscall`]; this helper now just adapts
+/// the generic primitive to the WAIT_AFTER call shape (returns elapsed_ms
+/// instead of the syscall's `()` return, treats `WorkerLost` as a benign
+/// no-op to match the original semantics).
+fn wait_after_with_timeout(fd: RawFd, off: u64, len: u64) -> Option<u64> {
+    let started = Instant::now();
+    match crate::io::bounded::bounded_syscall(None, WAIT_AFTER_TIMEOUT, move || unsafe {
+        libc::sync_file_range(fd, off as i64, len as i64, libc::SYNC_FILE_RANGE_WAIT_AFTER);
+    }) {
+        Ok(()) => Some(started.elapsed().as_millis() as u64),
+        Err(crate::io::bounded::BoundedError::Timeout)
+        | Err(crate::io::bounded::BoundedError::Halted) => None,
+        Err(crate::io::bounded::BoundedError::WorkerLost) => {
+            // Worker thread spawn failed or panicked before sending.
+            // Treat as a benign success (no syscall ran) rather than
+            // a degrade trigger — falling through with elapsed_ms=0
+            // matches the no-op behaviour.
+            Some(0)
+        }
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use tempfile::NamedTempFile;
+
+    /// Helper: build a `WritebackPipeline` over a local tempfile. On
+    /// every test rig (linux dev box, CI) the tempfile lives on a
+    /// local FS, so `is_nfs=false` and `skip_wait` returns false until
+    /// we explicitly mark the pipeline degraded.
+    fn local_pipeline(chunk_bytes: u64) -> (NamedTempFile, WritebackPipeline) {
+        let f = NamedTempFile::new().expect("tempfile create");
+        let pipeline = WritebackPipeline::new(f.as_file(), 0, chunk_bytes);
+        (f, pipeline)
+    }
+
+    #[test]
+    fn new_pipeline_starts_active() {
+        let (_f, p) = local_pipeline(32 * 1024 * 1024);
+        assert!(!p.is_nfs, "local tempfile must not classify as NFS");
+        assert!(!p.degraded.load(Ordering::Relaxed));
+        assert!(!p.skip_wait(), "fresh local pipeline must not skip wait");
+    }
+
+    #[test]
+    fn degraded_flag_short_circuits_wait() {
+        let (_f, p) = local_pipeline(32 * 1024 * 1024);
+        assert!(!p.skip_wait());
+        p.degraded.store(true, Ordering::Relaxed);
+        assert!(
+            p.skip_wait(),
+            "degraded flag must force the wait+dontneed bypass"
+        );
+    }
+
+    #[test]
+    fn record_wait_grows_chunk_on_high_p95() {
+        let (_f, mut p) = local_pipeline(16 * 1024 * 1024);
+        // Fill the window with samples above the grow threshold.
+        for _ in 0..ADAPTIVE_WINDOW {
+            p.record_wait(ADAPTIVE_GROW_MS + 50);
+        }
+        assert!(
+            p.chunk_bytes > 16 * 1024 * 1024,
+            "chunk should have grown; got {}",
+            p.chunk_bytes
+        );
+        assert!(p.chunk_bytes <= CHUNK_BYTES_MAX);
+    }
+
+    #[test]
+    fn record_wait_shrinks_chunk_on_low_p95() {
+        let (_f, mut p) = local_pipeline(64 * 1024 * 1024);
+        for _ in 0..ADAPTIVE_WINDOW {
+            p.record_wait(1); // well under ADAPTIVE_SHRINK_MS
+        }
+        assert!(
+            p.chunk_bytes < 64 * 1024 * 1024,
+            "chunk should have shrunk; got {}",
+            p.chunk_bytes
+        );
+        assert!(p.chunk_bytes >= CHUNK_BYTES_MIN);
+    }
+
+    #[test]
+    fn record_wait_no_op_below_window_fill() {
+        let (_f, mut p) = local_pipeline(16 * 1024 * 1024);
+        let initial = p.chunk_bytes;
+        // Only push a few samples; window not full → no adaptation.
+        for _ in 0..(ADAPTIVE_WINDOW - 1) {
+            p.record_wait(ADAPTIVE_GROW_MS + 100);
+        }
+        assert_eq!(
+            p.chunk_bytes, initial,
+            "chunk must not change before window is full"
+        );
+    }
+
+    #[test]
+    fn record_wait_clamps_to_chunk_bounds() {
+        // Grow past the max.
+        let (_f, mut p) = local_pipeline(CHUNK_BYTES_MAX);
+        for _ in 0..ADAPTIVE_WINDOW {
+            p.record_wait(ADAPTIVE_GROW_MS + 1000);
+        }
+        assert_eq!(p.chunk_bytes, CHUNK_BYTES_MAX, "must clamp to MAX");
+
+        // Shrink past the min.
+        let (_f, mut p) = local_pipeline(CHUNK_BYTES_MIN);
+        for _ in 0..ADAPTIVE_WINDOW {
+            p.record_wait(0);
+        }
+        assert_eq!(p.chunk_bytes, CHUNK_BYTES_MIN, "must clamp to MIN");
+    }
+
+    #[test]
+    fn detect_nfs_local_file_is_false() {
+        // Local tempfile must not classify as NFS. This locks in the
+        // consolidation through `crate::platform::fs_type::detect_fd`.
+        let f = NamedTempFile::new().expect("tempfile create");
+        use std::os::unix::io::AsRawFd;
+        assert!(!detect_nfs(f.as_file().as_raw_fd()));
+    }
+
+    #[test]
+    fn note_progress_below_chunk_is_noop() {
+        let (_f, mut p) = local_pipeline(32 * 1024 * 1024);
+        // No-op return before crossing the first chunk boundary.
+        let before = p.chunk_count;
+        p.note_progress(1024); // < 32 MiB
+        assert_eq!(p.chunk_count, before);
+        assert!(p.pending.is_none());
+    }
+}

src/io/writeback/noop.rs

@@ -0,0 +1,18 @@
+//! No-op writeback pipeline for non-Linux targets. macOS and Windows
+//! page cache policies have not been shown to exhibit the Linux
+//! accumulate-then-burst flush pathology for our access pattern.
+//! If that changes, replace this stub with a real implementation
+//! (e.g. `F_NOCACHE` on macOS, `FILE_FLAG_WRITE_THROUGH` on Windows).
+
+use std::fs::File;
+
+pub(crate) struct WritebackPipeline;
+
+impl WritebackPipeline {
+    pub(crate) fn new(_file: &File, _start_pos: u64, _chunk_bytes: u64) -> Self {
+        Self
+    }
+    pub(crate) fn note_progress(&mut self, _pos: u64) {}
+    pub(crate) fn handle_seek(&mut self, _new_pos: u64) {}
+    pub(crate) fn finalize(&mut self) {}
+}

src/io/writeback_file/linux.rs

@@ -0,0 +1,66 @@
+//! Linux platform impl for [`super::WritebackFile`].
+//!
+//! - `preallocate`: `fallocate(FALLOC_FL_KEEP_SIZE)` — reserve extents
+//!   without growing the reported file size. Reduces extent
+//!   fragmentation on large sequential writes (mux output on NFS in
+//!   particular).
+//! - `durable_sync`: `fsync` wrapped in
+//!   [`crate::io::bounded::bounded_syscall`] with a 60 s deadline so a
+//!   wedged NFS server can't trap the calling thread indefinitely.
+
+use std::fs::File;
+use std::io;
+use std::os::unix::io::AsRawFd;
+use std::time::Duration;
+
+/// Pre-reserve extents for `size_bytes` of upcoming sequential writes.
+/// Best-effort: a non-zero rc is logged but not propagated, since the
+/// caller would just continue with the unreserved file anyway.
+pub(super) fn preallocate(file: &File, size_bytes: u64) {
+    // FALLOC_FL_KEEP_SIZE = 0x01 — keep the reported file size at 0
+    // (writes grow it normally) while still pre-reserving the extents.
+    let rc = unsafe {
+        libc::fallocate(
+            file.as_raw_fd(),
+            libc::FALLOC_FL_KEEP_SIZE,
+            0,
+            size_bytes as i64,
+        )
+    };
+    tracing::debug!(
+        target: "mux",
+        "WritebackFile fallocate size_hint={size_bytes} rc={rc} ok={}",
+        rc == 0
+    );
+}
+
+/// Run `fsync` on `file` with a 60 s deadline. On timeout we log loudly
+/// and return `Ok(())` — the kernel will still flush on close, so the
+/// data is best-effort durable; the alternative (trap the thread for
+/// the rest of the rip) defeats `/api/stop`.
+pub(super) fn durable_sync(file: &File) -> io::Result<()> {
+    let fd = file.as_raw_fd();
+    match crate::io::bounded::bounded_syscall(
+        None,
+        Duration::from_secs(60),
+        move || -> io::Result<()> {
+            let rc = unsafe { libc::fsync(fd) };
+            if rc == 0 {
+                Ok(())
+            } else {
+                Err(io::Error::last_os_error())
+            }
+        },
+    ) {
+        Ok(inner) => inner,
+        Err(crate::io::bounded::BoundedError::Timeout) => {
+            tracing::error!(
+                target: "mux",
+                "WritebackFile::sync_all fsync timed out after 60s; kernel will flush on close (best-effort)"
+            );
+            Ok(())
+        }
+        Err(crate::io::bounded::BoundedError::Halted) => Ok(()),
+        Err(crate::io::bounded::BoundedError::WorkerLost) => Ok(()),
+    }
+}

src/io/writeback_file/macos.rs

@@ -0,0 +1,87 @@
+//! macOS platform impl for [`super::WritebackFile`].
+//!
+//! - `preallocate`: `fcntl(F_PREALLOCATE)` — macOS's fallocate-equiv.
+//!   Reserves a contiguous extent when possible, falling back to a
+//!   non-contiguous reservation if the FS can't satisfy it. Reported
+//!   file size is unchanged (`F_ALLOCATEALL` is not set, so allocation
+//!   is "best effort up to length"; growth happens via writes).
+//! - `durable_sync`: `fcntl(F_FULLFSYNC)` wrapped in
+//!   [`crate::io::bounded::bounded_syscall`] with a 60 s deadline.
+//!   F_FULLFSYNC is HFS+/APFS's true-fsync (flushes the disk's own
+//!   write cache) — what `fsync` should have been on macOS. Falls back
+//!   to plain `fsync` if F_FULLFSYNC returns ENOTSUP.
+
+use std::fs::File;
+use std::io;
+use std::os::unix::io::AsRawFd;
+use std::time::Duration;
+
+use crate::io::platform_macos::{
+    F_ALLOCATEALL, F_ALLOCATECONTIG, F_PEOFPOSMODE, F_PREALLOCATE, Fstore,
+};
+
+/// `fcntl(F_FULLFSYNC)` opcode. Documented in `man 2 fcntl` on macOS;
+/// not in the `libc` crate as a named constant.
+const F_FULLFSYNC: libc::c_int = 51;
+
+pub(super) fn preallocate(file: &File, size_bytes: u64) {
+    let mut fst = Fstore {
+        fst_flags: F_ALLOCATECONTIG | F_ALLOCATEALL,
+        fst_posmode: F_PEOFPOSMODE,
+        fst_offset: 0,
+        fst_length: size_bytes as libc::off_t,
+        fst_bytesalloc: 0,
+    };
+    // First attempt: contiguous.
+    let mut rc = unsafe { libc::fcntl(file.as_raw_fd(), F_PREALLOCATE, &mut fst) };
+    if rc == -1 {
+        // Fall back: drop the contiguous hint, allow scattered extents.
+        fst.fst_flags = F_ALLOCATEALL;
+        rc = unsafe { libc::fcntl(file.as_raw_fd(), F_PREALLOCATE, &mut fst) };
+    }
+    tracing::debug!(
+        target: "mux",
+        "WritebackFile F_PREALLOCATE size_hint={size_bytes} rc={rc} bytes_allocated={} ok={}",
+        fst.fst_bytesalloc,
+        rc != -1
+    );
+}
+
+pub(super) fn durable_sync(file: &File) -> io::Result<()> {
+    let fd = file.as_raw_fd();
+    match crate::io::bounded::bounded_syscall(
+        None,
+        Duration::from_secs(60),
+        move || -> io::Result<()> {
+            // Try F_FULLFSYNC first. If it isn't supported on this
+            // filesystem (older HFS, some network mounts) fall back to
+            // plain fsync — better than nothing.
+            let rc = unsafe { libc::fcntl(fd, F_FULLFSYNC, 0) };
+            if rc == 0 {
+                return Ok(());
+            }
+            let err = io::Error::last_os_error();
+            if err.raw_os_error() == Some(libc::ENOTSUP) {
+                let rc = unsafe { libc::fsync(fd) };
+                if rc == 0 {
+                    Ok(())
+                } else {
+                    Err(io::Error::last_os_error())
+                }
+            } else {
+                Err(err)
+            }
+        },
+    ) {
+        Ok(inner) => inner,
+        Err(crate::io::bounded::BoundedError::Timeout) => {
+            tracing::error!(
+                target: "mux",
+                "WritebackFile::sync_all F_FULLFSYNC timed out after 60s; kernel will flush on close (best-effort)"
+            );
+            Ok(())
+        }
+        Err(crate::io::bounded::BoundedError::Halted) => Ok(()),
+        Err(crate::io::bounded::BoundedError::WorkerLost) => Ok(()),
+    }
+}

src/io/writeback_file/mod.rs

@@ -0,0 +1,315 @@
+//! `WritebackFile` — a `File` wrapper whose reason for existing is the
+//! bounded-cache writeback pipeline.
+//!
+//! Why: large sequential writes (sweep, patch, mux on UHD-scale output)
+//! left to the kernel's default writeback policy accumulate hundreds of
+//! megabytes of dirty pages and then burst-flush, stalling subsequent
+//! writes for seconds at a time. `WritebackFile` drives a continuous
+//! [`super::writeback::WritebackPipeline`] that on Linux issues
+//! incremental `sync_file_range` + `posix_fadvise(DONTNEED)` calls at
+//! 32 MB granularity so dirty pages drain at the same rate they're
+//! produced. macOS and Windows fall through to a no-op pipeline — their
+//! default cache policies have not been shown to exhibit the same
+//! pathology for this access pattern.
+//!
+//! It implements `Write` and `Seek` so any call site that wrote to a
+//! plain `File` through those traits (sweep, patch, mux) can swap in
+//! `WritebackFile` without touching the body of the loop. The wrapper
+//! also tracks the current file position to feed the pipeline with
+//! progress + seek boundaries.
+//!
+//! See `super::writeback::linux` for the underlying pathology and the
+//! strategy.
+//!
+//! ## Platform split
+//!
+//! The platform-specific pieces of this wrapper — extent preallocation
+//! (Linux `fallocate(KEEP_SIZE)`, macOS `F_PREALLOCATE`, Windows
+//! `SetFileValidData`) and the durable-flush primitive (Linux/macOS
+//! `fsync`/`F_FULLFSYNC` wrapped in a bounded syscall, Windows
+//! `FlushFileBuffers`) — live in per-OS sibling modules. The dispatch
+//! happens once at the bottom of this file via cfg-gated `mod` decls.
+//! No inline `#[cfg(target_os = "...")]` in the business-logic above.
+//!
+//! ## Write path
+//!
+//! Writes are direct passthrough to the underlying `File` (no writer
+//! thread, no ring, no batching). Empirically the Phase-2.5
+//! writer-thread architecture introduced a ~60% mux throughput
+//! regression on NFS bidirectional workloads; reverting the write path
+//! to direct passthrough restores the 0.20.7 baseline. The writeback
+//! pipeline still runs (it's called inline from `write` / `write_all` /
+//! `seek`) so the bounded-cache invariant on Linux is preserved.
+//!
+//! ## Halt-safety
+//!
+//! `sync_all` runs the per-OS durable-flush primitive, which on
+//! Linux/macOS is wrapped in [`crate::io::bounded::bounded_syscall`]
+//! with a 60 s deadline. A wedged NFS server cannot trap the muxer
+//! indefinitely on the final fsync.
+
+#[cfg(target_os = "linux")]
+mod linux;
+#[cfg(target_os = "macos")]
+mod macos;
+#[cfg(not(any(target_os = "linux", target_os = "macos", target_os = "windows")))]
+mod other;
+#[cfg(target_os = "windows")]
+mod windows;
+
+#[cfg(target_os = "linux")]
+use linux as platform;
+#[cfg(target_os = "macos")]
+use macos as platform;
+#[cfg(not(any(target_os = "linux", target_os = "macos", target_os = "windows")))]
+use other as platform;
+#[cfg(target_os = "windows")]
+use windows as platform;
+
+use std::fs::{File, OpenOptions};
+use std::io::{self, Seek, SeekFrom, Write};
+use std::path::Path;
+
+use super::writeback::WritebackPipeline;
+
+/// Granularity at which the Linux writeback pipeline issues
+/// `sync_file_range` pairs. 32 MiB is the empirically best value on
+/// the rip1 test bed (NFS to unraid-1 over 1 GbE, single-disk SAS):
+/// 8 MiB / 64 MiB / 128 MiB all measured worse in the 0.21.x mux
+/// iteration runs. Override via `FREEMKV_WRITEBACK_CHUNK_MIB` —
+/// faster backends (NVMe, RAID) may tolerate larger windows.
+const WRITEBACK_CHUNK_BYTES_DEFAULT: u64 = 32 * 1024 * 1024;
+
+fn writeback_chunk_bytes() -> u64 {
+    std::env::var("FREEMKV_WRITEBACK_CHUNK_MIB")
+        .ok()
+        .and_then(|v| v.parse::<u64>().ok())
+        .filter(|&n| n > 0)
+        .map(|n| n * 1024 * 1024)
+        .unwrap_or(WRITEBACK_CHUNK_BYTES_DEFAULT)
+}
+
+pub(crate) struct WritebackFile {
+    file: File,
+    pipeline: WritebackPipeline,
+    pos: u64,
+}
+
+impl WritebackFile {
+    /// Wrap an open `File`. The current OS file position is queried
+    /// once so the pipeline starts tracking from wherever the file
+    /// already is (typically 0 for fresh files; non-zero for resumed
+    /// or appended files).
+    pub(crate) fn new(mut file: File) -> io::Result<Self> {
+        let pos = file.stream_position()?;
+        let pipeline = WritebackPipeline::new(&file, pos, writeback_chunk_bytes());
+        Ok(Self {
+            file,
+            pipeline,
+            pos,
+        })
+    }
+
+    /// Create a new file at `path` (truncating any existing contents)
+    /// and wrap it. Convenience for the common
+    /// `File::create(path)` + `WritebackFile::new(file)` pair so callers
+    /// don't have to assemble a `File` first.
+    ///
+    /// Callers that know the target output size should prefer
+    /// [`Self::create_with_size_hint`] so the kernel can pre-reserve
+    /// extents.
+    #[allow(dead_code)]
+    pub(crate) fn create(path: &Path) -> io::Result<Self> {
+        let file = File::create(path)?;
+        Self::new(file)
+    }
+
+    /// Like [`Self::create`] but pre-reserves `size_bytes` of disk
+    /// space via the platform's extent-preallocation primitive (Linux
+    /// `fallocate(KEEP_SIZE)`, macOS `F_PREALLOCATE`, Windows
+    /// `SetFileValidData` stub). The reported file size is unchanged
+    /// (writes still grow the file naturally) — only the on-disk extent
+    /// allocation is preallocated, which reduces extent fragmentation
+    /// on large sequential writes (mux output, especially on slow
+    /// storage / NFS).
+    ///
+    /// On platforms without an extent-preallocation primitive this is
+    /// equivalent to `create` — the size hint is dropped after a debug
+    /// log.
+    pub(crate) fn create_with_size_hint(path: &Path, size_bytes: u64) -> io::Result<Self> {
+        let file = File::create(path)?;
+        platform::preallocate(&file, size_bytes);
+        Self::new(file)
+    }
+
+    /// Open an existing file at `path` for writing (no truncation) and
+    /// wrap it. Mirrors `File::open` semantics for the writable case
+    /// — used by patch / resume paths that mutate an existing ISO in
+    /// place.
+    pub(crate) fn open(path: &Path) -> io::Result<Self> {
+        let file = OpenOptions::new().write(true).open(path)?;
+        Self::new(file)
+    }
+
+    /// Drain in-flight writeback then issue a full fsync. Use this in
+    /// place of `File::sync_all`.
+    ///
+    /// The final durable flush is wrapped in
+    /// [`crate::io::bounded::bounded_syscall`] (per the per-OS module)
+    /// with a 60 s deadline on Linux/macOS — a wedged NFS server cannot
+    /// trap the calling thread indefinitely. On timeout the page cache
+    /// is left to the kernel's normal flush-on-close path — best
+    /// effort, but bounded.
+    pub(crate) fn sync_all(&mut self) -> io::Result<()> {
+        self.pipeline.finalize();
+        platform::durable_sync(&self.file)
+    }
+}
+
+impl Write for WritebackFile {
+    fn write(&mut self, buf: &[u8]) -> io::Result<usize> {
+        let n = self.file.write(buf)?;
+        self.pos += n as u64;
+        self.pipeline.note_progress(self.pos);
+        Ok(n)
+    }
+
+    fn write_all(&mut self, buf: &[u8]) -> io::Result<()> {
+        self.file.write_all(buf)?;
+        self.pos += buf.len() as u64;
+        self.pipeline.note_progress(self.pos);
+        Ok(())
+    }
+
+    fn flush(&mut self) -> io::Result<()> {
+        self.file.flush()
+    }
+}
+
+impl Seek for WritebackFile {
+    fn seek(&mut self, from: SeekFrom) -> io::Result<u64> {
+        let p = self.file.seek(from)?;
+        // Only treat seeks that actually move the position as
+        // boundaries — sweep does a redundant `seek(Current(pos))`
+        // before every write, and we don't want that to drain the
+        // pipeline on every iteration.
+        if p != self.pos {
+            // Diagnostic for the NFS mux hang: the MKV format requires
+            // the muxer to seek back occasionally (cluster size
+            // patching, Cues index write, Segment header backpatch).
+            // Each such seek invalidates the writeback chunk tracking
+            // and forces a finalize → WAIT_AFTER on the in-flight
+            // chunk. Logging the seek delta lets us correlate hang
+            // offsets with specific muxer operations.
+            let from_pos = self.pos;
+            let to_pos = p;
+            let delta: i64 = (to_pos as i64).wrapping_sub(from_pos as i64);
+            tracing::debug!(
+                target: "mux",
+                "WritebackFile seek from={from_pos} to={to_pos} delta={delta}"
+            );
+            self.pipeline.handle_seek(p);
+            self.pos = p;
+        }
+        Ok(p)
+    }
+}
+
+impl Drop for WritebackFile {
+    fn drop(&mut self) {
+        // Run the pipeline's tail finalize so the last in-flight chunk
+        // gets its `WAIT_AFTER` + `posix_fadvise(DONTNEED)`. Without
+        // this, callers that drop a `WritebackFile` without calling
+        // `sync_all` (panic, early-return, idiomatic `let _ = w;`)
+        // leave the trailing chunk in cache; the kernel still flushes
+        // on close, but the bounded-cache invariant fails at the tail.
+        // We deliberately do *not* call `self.file.sync_all()` here —
+        // close already triggers a flush, and an `fsync` from `Drop`
+        // would silently swallow its `io::Error` anyway. `finalize` is
+        // idempotent so an explicit `sync_all` followed by drop is
+        // still safe.
+        self.pipeline.finalize();
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use std::io::Read;
+
+    fn read_back(path: &Path) -> Vec<u8> {
+        let mut f = File::open(path).unwrap();
+        let mut v = Vec::new();
+        f.read_to_end(&mut v).unwrap();
+        v
+    }
+
+    #[test]
+    fn write_then_drop_persists_bytes() {
+        let dir = tempfile::tempdir().unwrap();
+        let p = dir.path().join("a.bin");
+        {
+            let mut w = WritebackFile::create(&p).unwrap();
+            w.write_all(b"hello world").unwrap();
+            // Drop drains the pipeline tail.
+        }
+        assert_eq!(read_back(&p), b"hello world");
+    }
+
+    #[test]
+    fn sync_all_drains_and_flushes() {
+        let dir = tempfile::tempdir().unwrap();
+        let p = dir.path().join("b.bin");
+        let mut w = WritebackFile::create(&p).unwrap();
+        for _ in 0..32 {
+            w.write_all(&[0x5au8; 1024]).unwrap();
+        }
+        // After sync_all, the bytes MUST be visible to a separate
+        // reader. The pipeline has been finalised and durable-sync has
+        // run.
+        w.sync_all().unwrap();
+        let bytes = read_back(&p);
+        assert_eq!(bytes.len(), 32 * 1024);
+        assert!(bytes.iter().all(|&b| b == 0x5a));
+        drop(w);
+    }
+
+    #[test]
+    fn seek_then_patch_roundtrip() {
+        // Write A; seek back; patch with B; read back; the patch lands
+        // at the right offset.
+        let dir = tempfile::tempdir().unwrap();
+        let p = dir.path().join("c.bin");
+        let mut w = WritebackFile::create(&p).unwrap();
+        let big = vec![b'A'; 4096];
+        w.write_all(&big).unwrap();
+        // Seek back to offset 1000 and overwrite 8 bytes.
+        w.seek(SeekFrom::Start(1000)).unwrap();
+        w.write_all(b"PATCHED!").unwrap();
+        w.sync_all().unwrap();
+        drop(w);
+        let bytes = read_back(&p);
+        assert_eq!(bytes.len(), 4096);
+        assert_eq!(&bytes[1000..1008], b"PATCHED!");
+        // Bytes outside the patch are still 'A'.
+        assert_eq!(bytes[999], b'A');
+        assert_eq!(bytes[1008], b'A');
+    }
+
+    #[test]
+    fn flush_is_observed_in_order() {
+        // `Write::flush` should not panic or reorder; verify the bytes
+        // land in order through interleaved flushes.
+        let dir = tempfile::tempdir().unwrap();
+        let p = dir.path().join("f.bin");
+        let mut w = WritebackFile::create(&p).unwrap();
+        w.write_all(b"one").unwrap();
+        w.flush().unwrap();
+        w.write_all(b"two").unwrap();
+        w.flush().unwrap();
+        w.write_all(b"three").unwrap();
+        w.sync_all().unwrap();
+        drop(w);
+        assert_eq!(read_back(&p), b"onetwothree");
+    }
+}

src/io/writeback_file/other.rs

@@ -0,0 +1,23 @@
+//! Fallback platform impl for [`super::WritebackFile`] on targets
+//! without a dedicated implementation (BSDs, illumos, etc.).
+//!
+//! - `preallocate` is a logged no-op.
+//! - `durable_sync` calls `File::sync_all` directly (no bounded-syscall
+//!   wrapper — the wrapper depends on Linux/macOS unix idioms that
+//!   aren't universally portable). If a future BSD impl needs the
+//!   60-s deadline, it should land in its own per-OS file rather than
+//!   bloat this fallback.
+
+use std::fs::File;
+use std::io;
+
+pub(super) fn preallocate(_file: &File, size_bytes: u64) {
+    tracing::debug!(
+        target: "mux",
+        "WritebackFile preallocate size_hint={size_bytes} skipped (no impl on this target)"
+    );
+}
+
+pub(super) fn durable_sync(file: &File) -> io::Result<()> {
+    file.sync_all()
+}

src/io/writeback_file/windows.rs

@@ -0,0 +1,32 @@
+//! Windows platform impl for [`super::WritebackFile`].
+//!
+//! TODO: this stub matches the design's "validate without a Windows
+//! build env, leave a stub" carve-out. The real impl should use:
+//!
+//! - `SetEndOfFile` + `SetFileValidData` for extent preallocation
+//!   (caller needs `SE_MANAGE_VOLUME_NAME` privilege; if unavailable
+//!   fall back to a write-zero path or just skip).
+//! - `FlushFileBuffers` for fsync-equivalent durable flush.
+//!
+//! Until then: preallocate is a debug-logged no-op; durable_sync calls
+//! the std `File::sync_all` (which on Windows maps to
+//! `FlushFileBuffers` internally).
+
+use std::fs::File;
+use std::io;
+
+pub(super) fn preallocate(_file: &File, size_bytes: u64) {
+    tracing::debug!(
+        target: "mux",
+        "WritebackFile preallocate size_hint={size_bytes} skipped (windows stub; TODO: SetFileValidData)"
+    );
+}
+
+pub(super) fn durable_sync(file: &File) -> io::Result<()> {
+    // `File::sync_all` on Windows is `FlushFileBuffers`. Acceptable
+    // for now; the bounded-syscall wrapper is not used here because
+    // the stub also skips the worker-thread + leak machinery (the
+    // wrapper would need an `unsafe impl Send` for `RawHandle`, and
+    // designing that without a Windows test env is asking for it).
+    file.sync_all()
+}

src/keysource.rs

@@ -0,0 +1,89 @@
+//! Key sources — the lookup layer that hands libfreemkv a [`Key`].
+//!
+//! libfreemkv performs NO key lookup. An application resolves a key for a disc
+//! through one or more [`KeySource`]s, each a dumb adapter over a backing store
+//! (a keydb file, a key server, the mapfile cache): given the disc's
+//! [`DiscInputs`] it returns the raw [`Key`] at whatever level it holds. The
+//! library then derives down and decrypts via `Disc::decrypt_with`.
+//!
+//! Source implementations are published in the companion `freemkv-keysources`
+//! crate — keeping all key *policy* (which store, which order, online vs local)
+//! out of the library while all key *mechanism* (the AACS derivation chain)
+//! stays in it.
+
+use crate::disc::Key;
+
+/// The public AACS inputs a key source needs to look a disc up. Captured at
+/// scan; contains no secrets — only the disc identity and the on-disc AACS
+/// structures a source or key server may key on.
+#[derive(Debug, Clone)]
+pub struct DiscInputs {
+    /// SHA-1 of `Unit_Key_RO.inf`, `0x`-prefixed hex. The value a keydb keys
+    /// its per-disc entries by, and a key server identifies the disc with.
+    pub disc_hash: String,
+    /// Volume ID (16 bytes). `[0u8; 16]` when no authenticated handshake ran
+    /// (e.g. an ISO/mapfile flow), which disables VID-keyed lookups.
+    pub volume_id: [u8; 16],
+    /// Raw MKB bytes. Empty when not captured.
+    pub mkb: Vec<u8>,
+    /// Raw `Unit_Key_RO.inf` bytes. Empty when not captured.
+    pub unit_key_ro: Vec<u8>,
+    /// Encrypted on-disc content sample units (each a 6144-byte aligned unit),
+    /// for sources that validate a key server-side against real ciphertext
+    /// (e.g. an online key service). Empty for sources that don't need them
+    /// (a local keydb). Populated by the application — reading content requires
+    /// the disc reader, which the library's scan does not retain — so
+    /// [`crate::Disc::inputs`] leaves it empty for the caller to fill.
+    pub samples: Vec<Vec<u8>>,
+    /// The disc's human title — the UDF/ISO volume identifier (e.g.
+    /// `WICKED_FOR_GOOD`), falling back to the BDMV `<di:name>` when present.
+    /// `None` when not captured. Identity only, no secret; a key service may
+    /// record it (keyed by `disc_hash`) to build a hash→title catalog. Not used
+    /// in any AACS derivation.
+    pub volume_label: Option<String>,
+}
+
+/// A key source: a stateful provider that hands a disc's candidate [`Key`]s out
+/// **one at a time**, in whatever order it judges best for its backing store.
+///
+/// Dumb by contract — a source queries its store and yields the raw material it
+/// holds at whatever level it has (device / processing / media / volume / unit).
+/// It performs NO AACS derivation and NO validation: `Disc::decrypt_with`
+/// derives down AND validates against real ciphertext, returning `Err` for a key
+/// that does not decrypt this disc. That keeps every derivation step and the one
+/// validation gate in the library, across AACS 1.0 / 2.0 / 2.1 / 2.x.
+///
+/// The source is the one that knows how many candidates it has and in what order
+/// to try them — a keydb holds a per-disc UK *and* VUK *and* a device-key pool,
+/// so it hands them out cheapest/most-specific first (UK ▸ VK ▸ MK ▸ DK) and
+/// reports exhaustion when its list runs out; an online key service or a mapfile
+/// cache hold exactly one. The caller drives the loop: `next_key` →
+/// `Disc::decrypt_with` → on `Err`, ask again → until a key decrypts or the
+/// source returns `None` (a genuine "no key for this disc"). Compose several
+/// sources, in the caller's chosen order, with [`crate`]'s `MultiSource`.
+pub trait KeySource {
+    /// Hand the NEXT candidate key for this disc, or `None` once this source is
+    /// exhausted. Stateful: the source tracks what it already handed out this
+    /// session, so asking again after a rejected key yields the next candidate
+    /// (or `None`) — it never re-offers a key or re-hits a one-shot backend (an
+    /// online service is asked at most once). A source failure (I/O, network,
+    /// parse) surfaces as `None` — there is simply nothing more to try.
+    fn next_key(&mut self, inputs: &DiscInputs) -> Option<Key>;
+
+    /// Whether this source needs [`DiscInputs::samples`] populated (encrypted
+    /// content samples) — true for a source that validates against ciphertext
+    /// server-side, false for one that keys purely on disc identity. The caller
+    /// reads samples (an extra disc read) only when some source needs them.
+    fn needs_samples(&self) -> bool {
+        false
+    }
+
+    /// Whether this source FAILED (I/O, network, parse) rather than simply
+    /// having no key. Checked after exhaustion so the caller can tell a genuine
+    /// "no key for this disc" apart from "the key service was unreachable". A
+    /// store that treats absence as not-an-error (a missing keydb / mapfile)
+    /// leaves this `false`.
+    fn errored(&self) -> bool {
+        false
+    }
+}

src/labels/bdmt.rs

@@ -0,0 +1,402 @@
+//! BDMV disc-library metadata (`/BDMV/META/DL/bdmt_<lang>.xml`).
+//!
+//! Every commercial Blu-ray carries a disc-library metadata directory
+//! with one XML file per shipped language. The schema is the Blu-ray
+//! "disc library metadata" namespace (`urn:BDA:bdmv;disclibmeta`),
+//! conventionally prefixed `di:`. Fields commonly present:
+//!
+//! - `<di:title>` or `<di:name>` — the title string. Vendor practice
+//!   varies (Paramount discs tend to use `<di:name>`).
+//! - `<di:description>` — optional synopsis (often absent on retail
+//!   discs; common on box sets and special editions).
+//! - `<di:discNumber>` / `<di:numSets>` (or `<di:numberOfSets>`) —
+//!   set position for multi-disc releases.
+//!
+//! This module is intentionally separate from the BD-J `StreamLabel`
+//! parsers under `labels/*.rs`. The XML here is disc-level (title,
+//! description, set position), not per-stream — wiring into the main
+//! parser registry happens elsewhere.
+//!
+//! Real-world XML is irregular: missing description elements, multiple
+//! title elements (first one wins), and occasional malformed content.
+//! Extraction is best-effort — a malformed file is treated as "no
+//! metadata" (returns `None` from the helper), and the caller can
+//! still get metadata from sibling-language XML files.
+
+// The module wiring (registry hook + public re-export) is added
+// separately. Until then the parse/detect entry points have no
+use super::xml;
+use crate::sector::SectorSource;
+use crate::udf::UdfFs;
+use std::collections::BTreeMap;
+
+/// Disc-level metadata extracted from `/BDMV/META/DL/bdmt_*.xml`.
+///
+/// All maps are keyed by 3-char ISO 639-2 language code (e.g.
+/// `"eng"`, `"fra"`, `"jpn"`) — the same key segment used in the
+/// `bdmt_<lang>.xml` filename.
+#[derive(Debug, Clone, serde::Serialize, serde::Deserialize, Default)]
+pub struct DiscMetadata {
+    /// Localized titles, keyed by 3-char ISO 639-2 lang code
+    /// (e.g. "eng" → "Aurora Drift")
+    pub titles: BTreeMap<String, String>,
+    /// First-line / short description, per lang
+    pub descriptions: BTreeMap<String, String>,
+    /// Disc N of M for box sets (None if not a box set)
+    pub disc_number: Option<(u32, u32)>,
+}
+
+/// True if `/BDMV/META/DL/` exists and contains at least one
+/// `bdmt_*.xml` file.
+pub fn detect(udf: &UdfFs) -> bool {
+    let Some(dir) = udf.find_dir("/BDMV/META/DL") else {
+        return false;
+    };
+    dir.entries
+        .iter()
+        .any(|e| !e.is_dir && is_bdmt_filename(&e.name))
+}
+
+/// Read every `bdmt_<lang>.xml` under `/BDMV/META/DL/` and return the
+/// aggregated [`DiscMetadata`]. Returns `None` if no titles could be
+/// extracted from any file.
+pub fn parse(reader: &mut dyn SectorSource, udf: &UdfFs) -> Option<DiscMetadata> {
+    let dir = udf.find_dir("/BDMV/META/DL")?;
+    let mut out = DiscMetadata::default();
+
+    for entry in &dir.entries {
+        if entry.is_dir {
+            continue;
+        }
+        let Some(lang) = lang_code_from_filename(&entry.name) else {
+            continue;
+        };
+        let path = format!("/BDMV/META/DL/{}", entry.name);
+        let Ok(bytes) = udf.read_file(reader, &path) else {
+            continue;
+        };
+        let Ok(text) = std::str::from_utf8(&bytes) else {
+            continue;
+        };
+        let Some((title, description, disc_set)) = parse_bdmt_xml(&lang, text) else {
+            continue;
+        };
+        out.titles.insert(lang.clone(), title);
+        if let Some(desc) = description {
+            out.descriptions.insert(lang.clone(), desc);
+        }
+        // Disc-set position is disc-global; first one we successfully
+        // read wins. (All bdmt_*.xml on a given disc carry the same
+        // value in practice.)
+        if out.disc_number.is_none() {
+            if let Some(ds) = disc_set {
+                out.disc_number = Some(ds);
+            }
+        }
+    }
+
+    if out.titles.is_empty() {
+        None
+    } else {
+        Some(out)
+    }
+}
+
+/// True if `name` matches the `bdmt_<lang>.xml` convention with a
+/// 3-character ISO 639-2 lang code segment. Case-insensitive.
+fn is_bdmt_filename(name: &str) -> bool {
+    lang_code_from_filename(name).is_some()
+}
+
+/// Extract the 3-char language code from a `bdmt_<lang>.xml` filename.
+/// Returns `None` if the filename doesn't match. Lang code is
+/// lowercased so callers always see e.g. `"eng"` not `"ENG"`.
+fn lang_code_from_filename(name: &str) -> Option<String> {
+    let lower = name.to_ascii_lowercase();
+    let stem = lower.strip_suffix(".xml")?;
+    let lang = stem.strip_prefix("bdmt_")?;
+    // ISO 639-2 codes are exactly 3 ASCII letters. Be strict — keeps
+    // us from picking up unrelated `bdmt_foo.xml` siblings.
+    if lang.len() != 3 || !lang.chars().all(|c| c.is_ascii_alphabetic()) {
+        return None;
+    }
+    Some(lang.to_string())
+}
+
+/// Tuple returned by [`parse_bdmt_xml`]: `(title, description?, disc_set?)`.
+/// Aliased so the function signature isn't a clippy::type-complexity offender.
+pub(crate) type BdmtFields = (String, Option<String>, Option<(u32, u32)>);
+
+/// Parse one `bdmt_<lang>.xml` document and return
+/// `(title, description?, disc_set?)`. Returns `None` if no title
+/// could be located — the caller treats this as "skip this file".
+///
+/// Title-element preference: `<di:name>` → `<di:title>` →
+/// `<di:tableOfContents>/<di:titleName>` (first match wins, per the
+/// authoring-tool conventions documented at the module level).
+pub(crate) fn parse_bdmt_xml(_lang_code: &str, xml_text: &str) -> Option<BdmtFields> {
+    let title = extract_title(xml_text)?;
+    let description = xml::text(xml_text, "description")
+        .filter(|s| !s.is_empty())
+        .filter(|s| !looks_like_xml(s))
+        .map(|s| s.trim().to_string())
+        .filter(|s| !s.is_empty());
+    let disc_set = extract_disc_set(xml_text);
+    Some((title, description, disc_set))
+}
+
+/// Reject candidate description strings that are themselves XML
+/// fragments — observed on a captured disc, where
+/// `<di:description>` contained `<di:thumbnail href="…"/>` child
+/// elements and no actual prose. Surfacing that raw to the JSON
+/// output is worse than dropping the field entirely.
+fn looks_like_xml(s: &str) -> bool {
+    let t = s.trim_start();
+    t.starts_with('<')
+}
+
+/// Try title-bearing element variants in priority order. The `xml`
+/// helpers are case- and namespace-insensitive, so callers pass the
+/// bare local name (no `di:` prefix).
+fn extract_title(xml_text: &str) -> Option<String> {
+    // Order matches the module-level convention: <di:name> first
+    // (Paramount-style), then <di:title>, then the nested
+    // tableOfContents/titleName form.
+    for tag in ["name", "title"] {
+        if let Some(s) = xml::text(xml_text, tag) {
+            let trimmed = s.trim();
+            if !trimmed.is_empty() {
+                return Some(trimmed.to_string());
+            }
+        }
+    }
+    // tableOfContents/titleName: search inside the toc block so we
+    // don't accidentally pick a stray <titleName> from elsewhere.
+    if let Some((s, e)) = xml::find_element(xml_text, "tableOfContents", 0) {
+        let block = &xml_text[s..e];
+        if let Some(t) = xml::text(block, "titleName") {
+            let trimmed = t.trim();
+            if !trimmed.is_empty() {
+                return Some(trimmed.to_string());
+            }
+        }
+    }
+    None
+}
+
+/// Extract `(discNumber, numSets)` if both are present and parse as
+/// `u32`. Accepts either `<di:numSets>` or `<di:numberOfSets>` for
+/// the denominator (both forms appear in the wild).
+fn extract_disc_set(xml_text: &str) -> Option<(u32, u32)> {
+    let n = xml::text(xml_text, "discNumber")?
+        .trim()
+        .parse::<u32>()
+        .ok()?;
+    let total = xml::text(xml_text, "numSets")
+        .or_else(|| xml::text(xml_text, "numberOfSets"))?
+        .trim()
+        .parse::<u32>()
+        .ok()?;
+    Some((n, total))
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn extract_simple_title() {
+        // Minimal Paramount-style document: <di:name> as the title
+        // carrier inside a <discInfo> root.
+        let xml = r#"<?xml version="1.0" encoding="UTF-8"?>
+<discInfo xmlns:di="urn:BDA:bdmv;disclibmeta">
+  <di:name>Aurora Drift</di:name>
+</discInfo>"#;
+        let (title, desc, set) = parse_bdmt_xml("eng", xml).expect("title should parse");
+        assert_eq!(title, "Aurora Drift");
+        assert_eq!(desc, None);
+        assert_eq!(set, None);
+    }
+
+    #[test]
+    fn extract_title_element_variant() {
+        // <di:title> is the alternate carrier; should be picked up
+        // when <di:name> is absent.
+        let xml = r#"<discInfo xmlns:di="urn:BDA:bdmv;disclibmeta">
+  <di:title>Echo Chamber</di:title>
+  <di:description>A film about machines.</di:description>
+</discInfo>"#;
+        let (title, desc, _) = parse_bdmt_xml("eng", xml).unwrap();
+        assert_eq!(title, "Echo Chamber");
+        assert_eq!(desc.as_deref(), Some("A film about machines."));
+    }
+
+    #[test]
+    fn extract_title_from_table_of_contents_fallback() {
+        // Some authoring tools nest the title under tableOfContents.
+        // No <di:name> or <di:title> at top level → fall back to
+        // titleName inside tableOfContents.
+        let xml = r#"<discInfo xmlns:di="urn:BDA:bdmv;disclibmeta">
+  <di:tableOfContents>
+    <di:titleName>Feelings Two</di:titleName>
+  </di:tableOfContents>
+</discInfo>"#;
+        let (title, _, _) = parse_bdmt_xml("eng", xml).unwrap();
+        assert_eq!(title, "Feelings Two");
+    }
+
+    #[test]
+    fn extract_box_set_position() {
+        let xml = r#"<discInfo xmlns:di="urn:BDA:bdmv;disclibmeta">
+  <di:name>Box Set Disc 2</di:name>
+  <di:discNumber>2</di:discNumber>
+  <di:numSets>5</di:numSets>
+</discInfo>"#;
+        let (_, _, set) = parse_bdmt_xml("eng", xml).unwrap();
+        assert_eq!(set, Some((2, 5)));
+    }
+
+    #[test]
+    fn extract_box_set_position_alternate_total_tag() {
+        // <di:numberOfSets> is an alternate spelling we've seen.
+        let xml = r#"<discInfo xmlns:di="urn:BDA:bdmv;disclibmeta">
+  <di:name>X</di:name>
+  <di:discNumber>3</di:discNumber>
+  <di:numberOfSets>6</di:numberOfSets>
+</discInfo>"#;
+        let (_, _, set) = parse_bdmt_xml("eng", xml).unwrap();
+        assert_eq!(set, Some((3, 6)));
+    }
+
+    #[test]
+    fn extract_box_set_requires_both_fields() {
+        // discNumber alone (no total) yields None — we don't fabricate
+        // a denominator.
+        let xml = r#"<discInfo xmlns:di="urn:BDA:bdmv;disclibmeta">
+  <di:name>X</di:name>
+  <di:discNumber>1</di:discNumber>
+</discInfo>"#;
+        let (_, _, set) = parse_bdmt_xml("eng", xml).unwrap();
+        assert_eq!(set, None);
+    }
+
+    #[test]
+    fn multiple_languages_keyed_correctly() {
+        // Simulate driving parse_bdmt_xml from two synthetic XML
+        // blobs and aggregating into DiscMetadata the same way parse()
+        // would. This exercises the BTreeMap key handling without
+        // needing a UdfFs.
+        let eng_xml = r#"<discInfo xmlns:di="urn:BDA:bdmv;disclibmeta">
+  <di:name>Aurora Drift</di:name>
+</discInfo>"#;
+        let fra_xml = r#"<discInfo xmlns:di="urn:BDA:bdmv;disclibmeta">
+  <di:name>Aurora Drift (Partie Deux)</di:name>
+  <di:description>Suite du film fictif.</di:description>
+</discInfo>"#;
+
+        let mut meta = DiscMetadata::default();
+        for (lang, blob) in [("eng", eng_xml), ("fra", fra_xml)] {
+            let (title, desc, ds) = parse_bdmt_xml(lang, blob).unwrap();
+            meta.titles.insert(lang.to_string(), title);
+            if let Some(d) = desc {
+                meta.descriptions.insert(lang.to_string(), d);
+            }
+            if meta.disc_number.is_none() {
+                if let Some(d) = ds {
+                    meta.disc_number = Some(d);
+                }
+            }
+        }
+
+        assert_eq!(
+            meta.titles.get("eng").map(String::as_str),
+            Some("Aurora Drift")
+        );
+        assert_eq!(
+            meta.titles.get("fra").map(String::as_str),
+            Some("Aurora Drift (Partie Deux)")
+        );
+        assert!(meta.descriptions.get("eng").is_none());
+        assert_eq!(
+            meta.descriptions.get("fra").map(String::as_str),
+            Some("Suite du film fictif.")
+        );
+        assert_eq!(meta.disc_number, None);
+    }
+
+    #[test]
+    fn malformed_xml_returns_none() {
+        // Random gibberish has no recognizable title element. We
+        // document the contract: parse_bdmt_xml returns None, and
+        // parse() (the caller) skips the file. Aggregating across
+        // zero files leaves DiscMetadata::default() — which parse()
+        // surfaces as None to its caller. Either is documented as
+        // acceptable per the module spec.
+        let bad = "this is not xml &&& <<< nope";
+        assert!(parse_bdmt_xml("eng", bad).is_none());
+
+        // Half-open tag, no body, no close: also yields no title.
+        let truncated = "<discInfo><di:name>";
+        assert!(parse_bdmt_xml("eng", truncated).is_none());
+    }
+
+    #[test]
+    fn description_with_only_child_xml_is_dropped() {
+        // Real-world bug from a captured disc (2026-05-11
+        // capture): <di:description> contained only <di:thumbnail/>
+        // child elements with no actual prose. The previous parser
+        // surfaced the raw XML fragment as the description string.
+        // Now we reject candidates that begin with `<`.
+        let xml = r#"<discInfo>
+            <di:name>Skyline Run</di:name>
+            <di:description>
+              <di:thumbnail href="sample_meta_sm.jpg" />
+              <di:thumbnail href="sample_meta_lg.jpg" />
+            </di:description>
+        </discInfo>"#;
+        let (title, description, _) =
+            parse_bdmt_xml("eng", xml).expect("title is present so parse must succeed");
+        assert_eq!(title, "Skyline Run");
+        assert!(
+            description.is_none(),
+            "description containing only XML children must be dropped, got {description:?}"
+        );
+    }
+
+    #[test]
+    fn description_with_plain_text_passes_through() {
+        // The legitimate case still works: a description with actual
+        // prose survives the looks_like_xml filter.
+        let xml = r#"<discInfo>
+            <di:name>Some Movie</di:name>
+            <di:description>An epic tale of one man's quest for tea.</di:description>
+        </discInfo>"#;
+        let (_, description, _) = parse_bdmt_xml("eng", xml).expect("must parse");
+        assert_eq!(
+            description.as_deref(),
+            Some("An epic tale of one man's quest for tea.")
+        );
+    }
+
+    #[test]
+    fn whitespace_in_title_is_trimmed() {
+        let xml = r#"<discInfo><di:name>
+            Aurora Drift
+        </di:name></discInfo>"#;
+        let (title, _, _) = parse_bdmt_xml("eng", xml).unwrap();
+        assert_eq!(title, "Aurora Drift");
+    }
+
+    #[test]
+    fn lang_code_extraction() {
+        assert_eq!(lang_code_from_filename("bdmt_eng.xml"), Some("eng".into()));
+        assert_eq!(lang_code_from_filename("BDMT_FRA.XML"), Some("fra".into()));
+        assert_eq!(lang_code_from_filename("bdmt_jpn.xml"), Some("jpn".into()));
+        // Non-matching cases:
+        assert_eq!(lang_code_from_filename("bdmt_.xml"), None);
+        assert_eq!(lang_code_from_filename("bdmt_engl.xml"), None);
+        assert_eq!(lang_code_from_filename("bdmt_e1g.xml"), None);
+        assert_eq!(lang_code_from_filename("bdmt_eng.txt"), None);
+        assert_eq!(lang_code_from_filename("foo.xml"), None);
+    }
+}

src/labels/clpi_audit.rs

@@ -0,0 +1,291 @@
+//! CLPI vs MPLS cross-validation diagnostic.
+//!
+//! Empirical question (raised 2026-05-11): is CLPI's per-stream
+//! language and codec data truly redundant with MPLS's STN-table data
+//! on real-world Blu-rays?
+//!
+//! Build a quick audit that walks both sources, normalizes their stream
+//! lists by (PID, language, coding_type), and flags any disagreement.
+//!
+//! Three classes of mismatch we want to detect:
+//!
+//! 1. **CLPI has streams MPLS doesn't reference.** Orphan streams in
+//!    the .m2ts that no playlist's STN table includes. Means the user
+//!    can't reach them through the menu but they're physically on the
+//!    disc.
+//! 2. **MPLS has streams CLPI doesn't list.** Should never happen if
+//!    both parsers are correct — playlists reference clips which
+//!    reference streams. If it happens, one of our parsers has a bug.
+//! 3. **Same PID, different language / coding_type.** The playlist re-
+//!    tagged a stream's metadata. Rare but spec-permitted. Means CLPI
+//!    and MPLS disagree about the same physical stream's properties.
+//!
+//! If audits across the corpus show zero mismatches of any class, CLPI
+//! program_info extraction is **empirically redundant** for labels and
+//! we can leave it out of the registry. If even one mismatch surfaces,
+//! we add a CLPI label parser to the registry as belt-and-suspenders.
+//!
+//! This module exposes `audit(reader, udf)` returning a structured
+//! report. Surfaced via the labels-analyze tool — not part of the
+//! `analyze()` pipeline (no impact on the label output).
+
+use crate::sector::SectorSource;
+use crate::udf::UdfFs;
+use std::collections::BTreeMap;
+
+/// One row in the audit: a stream PID that's known to one source or
+/// both, with the fields each source reported.
+#[derive(Debug, Clone)]
+pub struct ClpiVsMplsRow {
+    pub pid: u16,
+    pub clpi_coding_type: Option<u8>,
+    pub clpi_language: Option<String>,
+    pub mpls_coding_type: Option<u8>,
+    pub mpls_language: Option<String>,
+}
+
+impl ClpiVsMplsRow {
+    /// Three rules for classification:
+    /// - both sources missing (impossible — caller wouldn't insert)
+    /// - one source missing → class A or B (orphan-on-disc / playlist-only)
+    /// - both present but fields differ → class C (metadata divergence)
+    /// - both present and identical → no mismatch
+    pub fn class(&self) -> ClpiVsMplsClass {
+        match (
+            self.clpi_coding_type.is_some(),
+            self.mpls_coding_type.is_some(),
+        ) {
+            (true, false) => ClpiVsMplsClass::ClpiOnly,
+            (false, true) => ClpiVsMplsClass::MplsOnly,
+            (true, true) => {
+                let coding_match = self.clpi_coding_type == self.mpls_coding_type;
+                let lang_match = self.clpi_language == self.mpls_language;
+                if coding_match && lang_match {
+                    ClpiVsMplsClass::Match
+                } else {
+                    ClpiVsMplsClass::Divergent
+                }
+            }
+            (false, false) => ClpiVsMplsClass::Match,
+        }
+    }
+}
+
+/// Classification of one (PID) row.
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub enum ClpiVsMplsClass {
+    /// PID seen in CLPI ProgramInfo but no MPLS STN table references
+    /// it. Orphan on disc.
+    ClpiOnly,
+    /// PID seen in MPLS STN table but no CLPI ProgramInfo includes it.
+    /// One of our parsers probably has a bug.
+    MplsOnly,
+    /// Both sources see this PID with the same coding_type + language.
+    Match,
+    /// Both sources see this PID but disagree on coding_type or language.
+    /// MPLS wins for label rendering (playlist-authoritative view); CLPI
+    /// is the per-clip ground truth.
+    Divergent,
+}
+
+/// Full audit report.
+#[derive(Debug, Clone, Default)]
+pub struct ClpiVsMplsAudit {
+    pub rows: Vec<ClpiVsMplsRow>,
+}
+
+impl ClpiVsMplsAudit {
+    pub fn class_counts(&self) -> (usize, usize, usize, usize) {
+        let mut clpi_only = 0;
+        let mut mpls_only = 0;
+        let mut matches = 0;
+        let mut divergent = 0;
+        for r in &self.rows {
+            match r.class() {
+                ClpiVsMplsClass::ClpiOnly => clpi_only += 1,
+                ClpiVsMplsClass::MplsOnly => mpls_only += 1,
+                ClpiVsMplsClass::Match => matches += 1,
+                ClpiVsMplsClass::Divergent => divergent += 1,
+            }
+        }
+        (clpi_only, mpls_only, matches, divergent)
+    }
+}
+
+/// Walk `/BDMV/CLIPINF/*.clpi` and `/BDMV/PLAYLIST/*.mpls`, build a
+/// dedup-by-PID table of (CLPI fields, MPLS fields), return the
+/// merged view. Missing files (read errors, parse failures) are
+/// silently skipped — this is diagnostic, not correctness-critical.
+pub fn audit(reader: &mut dyn SectorSource, udf: &UdfFs) -> ClpiVsMplsAudit {
+    // Aggregate by PID across all CLPI files. If a PID appears in
+    // multiple clips (typical — main movie clip + trailers reference
+    // the same audio stream PIDs), first encountered wins (they should
+    // all agree per BD spec).
+    let mut clpi_by_pid: BTreeMap<u16, (u8, String)> = BTreeMap::new();
+    if let Some(dir) = udf.find_dir("/BDMV/CLIPINF") {
+        let names: Vec<String> = dir
+            .entries
+            .iter()
+            .filter(|e| !e.is_dir && e.name.to_ascii_lowercase().ends_with(".clpi"))
+            .map(|e| e.name.clone())
+            .collect();
+        for name in names {
+            let path = format!("/BDMV/CLIPINF/{}", name);
+            let Ok(data) = udf.read_file(reader, &path) else {
+                continue;
+            };
+            let Ok(clip) = crate::clpi::parse(&data) else {
+                continue;
+            };
+            for s in clip.streams {
+                clpi_by_pid
+                    .entry(s.pid)
+                    .or_insert((s.coding_type, s.language));
+            }
+        }
+    }
+
+    // Same for MPLS streams.
+    let mut mpls_by_pid: BTreeMap<u16, (u8, String)> = BTreeMap::new();
+    if let Some(dir) = udf.find_dir("/BDMV/PLAYLIST") {
+        let names: Vec<String> = dir
+            .entries
+            .iter()
+            .filter(|e| !e.is_dir && e.name.to_ascii_lowercase().ends_with(".mpls"))
+            .map(|e| e.name.clone())
+            .collect();
+        for name in names {
+            let path = format!("/BDMV/PLAYLIST/{}", name);
+            let Ok(data) = udf.read_file(reader, &path) else {
+                continue;
+            };
+            let Ok(pl) = crate::mpls::parse(&data) else {
+                continue;
+            };
+            for s in pl.streams {
+                if s.pid == 0 {
+                    // PID 0 means "no PID in stream entry" — skip rather
+                    // than collide with other entries.
+                    continue;
+                }
+                mpls_by_pid
+                    .entry(s.pid)
+                    .or_insert((s.coding_type, s.language));
+            }
+        }
+    }
+
+    // Merge views: every PID seen anywhere gets a row.
+    let mut all_pids: std::collections::BTreeSet<u16> = std::collections::BTreeSet::new();
+    all_pids.extend(clpi_by_pid.keys().copied());
+    all_pids.extend(mpls_by_pid.keys().copied());
+
+    let mut rows = Vec::with_capacity(all_pids.len());
+    for pid in all_pids {
+        let clpi = clpi_by_pid.get(&pid);
+        let mpls = mpls_by_pid.get(&pid);
+        rows.push(ClpiVsMplsRow {
+            pid,
+            clpi_coding_type: clpi.map(|(c, _)| *c),
+            clpi_language: clpi.map(|(_, l)| l.clone()),
+            mpls_coding_type: mpls.map(|(c, _)| *c),
+            mpls_language: mpls.map(|(_, l)| l.clone()),
+        });
+    }
+
+    ClpiVsMplsAudit { rows }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn class_match_when_identical() {
+        let r = ClpiVsMplsRow {
+            pid: 0x1100,
+            clpi_coding_type: Some(0x83),
+            clpi_language: Some("eng".into()),
+            mpls_coding_type: Some(0x83),
+            mpls_language: Some("eng".into()),
+        };
+        assert_eq!(r.class(), ClpiVsMplsClass::Match);
+    }
+
+    #[test]
+    fn class_clpi_only_when_mpls_missing() {
+        let r = ClpiVsMplsRow {
+            pid: 0x1100,
+            clpi_coding_type: Some(0x83),
+            clpi_language: Some("eng".into()),
+            mpls_coding_type: None,
+            mpls_language: None,
+        };
+        assert_eq!(r.class(), ClpiVsMplsClass::ClpiOnly);
+    }
+
+    #[test]
+    fn class_mpls_only_when_clpi_missing() {
+        let r = ClpiVsMplsRow {
+            pid: 0x1100,
+            clpi_coding_type: None,
+            clpi_language: None,
+            mpls_coding_type: Some(0x90),
+            mpls_language: Some("fra".into()),
+        };
+        assert_eq!(r.class(), ClpiVsMplsClass::MplsOnly);
+    }
+
+    #[test]
+    fn class_divergent_on_lang_disagreement() {
+        let r = ClpiVsMplsRow {
+            pid: 0x1100,
+            clpi_coding_type: Some(0x83),
+            clpi_language: Some("eng".into()),
+            mpls_coding_type: Some(0x83),
+            mpls_language: Some("und".into()),
+        };
+        assert_eq!(r.class(), ClpiVsMplsClass::Divergent);
+    }
+
+    #[test]
+    fn class_counts_sum_rows() {
+        let audit = ClpiVsMplsAudit {
+            rows: vec![
+                ClpiVsMplsRow {
+                    pid: 0x1100,
+                    clpi_coding_type: Some(0x83),
+                    clpi_language: Some("eng".into()),
+                    mpls_coding_type: Some(0x83),
+                    mpls_language: Some("eng".into()),
+                }, // Match
+                ClpiVsMplsRow {
+                    pid: 0x1101,
+                    clpi_coding_type: Some(0x83),
+                    clpi_language: Some("fra".into()),
+                    mpls_coding_type: None,
+                    mpls_language: None,
+                }, // ClpiOnly
+                ClpiVsMplsRow {
+                    pid: 0x1102,
+                    clpi_coding_type: None,
+                    clpi_language: None,
+                    mpls_coding_type: Some(0x90),
+                    mpls_language: Some("eng".into()),
+                }, // MplsOnly
+                ClpiVsMplsRow {
+                    pid: 0x1103,
+                    clpi_coding_type: Some(0x86),
+                    clpi_language: Some("spa".into()),
+                    mpls_coding_type: Some(0x86),
+                    mpls_language: Some("ita".into()),
+                }, // Divergent
+            ],
+        };
+        let (co, mo, m, d) = audit.class_counts();
+        assert_eq!(co, 1);
+        assert_eq!(mo, 1);
+        assert_eq!(m, 1);
+        assert_eq!(d, 1);
+    }
+}

src/labels/criterion.rs

@@ -3,8 +3,8 @@
 //! Clean structured XML with Content/Qualifier per stream and
 //! stream number mapping via playbackconfig.
 
-use super::{LabelPurpose, LabelQualifier, StreamLabel, StreamLabelType};
-use crate::sector::SectorReader;
+use super::{LabelPurpose, LabelQualifier, ParseResult, StreamLabel, StreamLabelType, xml};
+use crate::sector::SectorSource;
 use crate::udf::UdfFs;
 use std::collections::HashMap;
 
@@ -12,7 +12,7 @@ pub fn detect(udf: &UdfFs) -> bool {
     super::jar_file_exists(udf, "streamproperties.xml")
 }
 
-pub fn parse(reader: &mut dyn SectorReader, udf: &UdfFs) -> Option<Vec<StreamLabel>> {
+pub fn parse(reader: &mut dyn SectorSource, udf: &UdfFs) -> Option<ParseResult> {
     let sp_data = super::read_jar_file(reader, udf, "streamproperties.xml")?;
     let sp_text = std::str::from_utf8(&sp_data).ok()?;
 
@@ -66,7 +66,8 @@ pub fn parse(reader: &mut dyn SectorReader, udf: &UdfFs) -> Option<Vec<StreamLab
     if labels.is_empty() {
         return None;
     }
-    Some(labels)
+    // High confidence: streamproperties.xml is fully structured.
+    Some(ParseResult::high(labels))
 }
 
 struct StreamInfo {
@@ -78,105 +79,68 @@ struct StreamInfo {
     qualifier: LabelQualifier,
 }
 
-fn parse_stream_infos(xml: &str) -> Vec<StreamInfo> {
+fn parse_stream_infos(text: &str) -> Vec<StreamInfo> {
     let mut infos = Vec::new();
-    let mut pos = 0;
 
-    while pos < xml.len() {
-        let (tag, stream_type) = if let Some(p) = xml[pos..].find("<AudioStreamInfos>") {
-            (p + pos, StreamLabelType::Audio)
-        } else if let Some(p) = xml[pos..].find("<SubtitleStreamInfos>") {
-            (p + pos, StreamLabelType::Subtitle)
-        } else {
-            break;
-        };
+    for (tag_name, stream_type) in [
+        ("AudioStreamInfos", StreamLabelType::Audio),
+        ("SubtitleStreamInfos", StreamLabelType::Subtitle),
+    ] {
+        let mut from = 0;
+        while let Some((start, end)) = xml::find_element(text, tag_name, from) {
+            let block = &text[start..end];
+            let id = xml::text(block, "ID").unwrap_or_default();
+            let lang_id = xml::text(block, "LangInfoID").unwrap_or_default();
+            let content = xml::text(block, "Content").unwrap_or_default();
+            let qualifier_str = xml::text(block, "Qualifier").unwrap_or_default();
 
-        let end_tag = match stream_type {
-            StreamLabelType::Audio => "</AudioStreamInfos>",
-            StreamLabelType::Subtitle => "</SubtitleStreamInfos>",
-        };
+            let (language, variant) = if lang_id.contains('_') {
+                let parts: Vec<&str> = lang_id.splitn(2, '_').collect();
+                (parts[0].to_lowercase(), parts[1].to_string())
+            } else {
+                (lang_id.to_lowercase(), String::new())
+            };
 
-        let block_end = match xml[tag..].find(end_tag) {
-            Some(p) => tag + p + end_tag.len(),
-            None => break,
-        };
+            let purpose = if content.eq_ignore_ascii_case("COMMENTARY") {
+                LabelPurpose::Commentary
+            } else {
+                LabelPurpose::Normal
+            };
 
-        let block = &xml[tag..block_end];
-        let id = extract_tag(block, "ID").unwrap_or_default();
-        let lang_id = extract_tag(block, "LangInfoID").unwrap_or_default();
-        let content = extract_tag(block, "Content").unwrap_or_default();
-        let qualifier_str = extract_tag(block, "Qualifier").unwrap_or_default();
+            let qualifier = match qualifier_str.to_ascii_uppercase().as_str() {
+                "SDH" => LabelQualifier::Sdh,
+                "DS" => LabelQualifier::DescriptiveService,
+                _ => LabelQualifier::None,
+            };
 
-        let (language, variant) = if lang_id.contains('_') {
-            let parts: Vec<&str> = lang_id.splitn(2, '_').collect();
-            (parts[0].to_lowercase(), parts[1].to_string())
-        } else {
-            (lang_id.to_lowercase(), String::new())
-        };
-
-        let purpose = match content.as_str() {
-            "COMMENTARY" => LabelPurpose::Commentary,
-            _ => LabelPurpose::Normal,
-        };
-
-        let qualifier = match qualifier_str.as_str() {
-            "SDH" => LabelQualifier::Sdh,
-            "DS" => LabelQualifier::DescriptiveService,
-            _ => LabelQualifier::None,
-        };
-
-        infos.push(StreamInfo {
-            id,
-            stream_type,
-            language,
-            variant,
-            purpose,
-            qualifier,
-        });
-        pos = block_end;
+            infos.push(StreamInfo {
+                id,
+                stream_type,
+                language,
+                variant,
+                purpose,
+                qualifier,
+            });
+            from = end;
+        }
     }
     infos
 }
 
-fn parse_playback_config(xml: &str, map: &mut HashMap<String, u16>) {
-    let mut pos = 0;
-    while pos < xml.len() {
-        let tag_start = if let Some(p) = xml[pos..].find("<AudioStreams>") {
-            Some(p + pos)
-        } else {
-            xml[pos..].find("<SubtitlesStreams>").map(|p| p + pos)
-        };
-
-        let tag_start = match tag_start {
-            Some(p) => p,
-            None => break,
-        };
-
-        let block_end = xml[tag_start..]
-            .find("</AudioStreams>")
-            .or_else(|| xml[tag_start..].find("</SubtitlesStreams>"))
-            .map(|p| tag_start + p + 20)
-            .unwrap_or(xml.len());
-
-        let block = &xml[tag_start..block_end];
-
-        if let (Some(stream_id_str), Some(info_id)) = (
-            extract_tag(block, "StreamID"),
-            extract_tag(block, "StreamInfo_ID"),
-        ) {
-            if let Ok(stream_num) = stream_id_str.parse::<u16>() {
-                map.insert(info_id, stream_num);
+fn parse_playback_config(text: &str, map: &mut HashMap<String, u16>) {
+    for tag_name in ["AudioStreams", "SubtitlesStreams"] {
+        let mut from = 0;
+        while let Some((start, end)) = xml::find_element(text, tag_name, from) {
+            let block = &text[start..end];
+            if let (Some(stream_id_str), Some(info_id)) = (
+                xml::text(block, "StreamID"),
+                xml::text(block, "StreamInfo_ID"),
+            ) {
+                if let Ok(stream_num) = stream_id_str.parse::<u16>() {
+                    map.insert(info_id, stream_num);
+                }
             }
+            from = end;
         }
-
-        pos = block_end;
     }
 }
-
-fn extract_tag(xml: &str, tag: &str) -> Option<String> {
-    let open = format!("<{tag}>");
-    let close = format!("</{tag}>");
-    let start = xml.find(&open)? + open.len();
-    let end = xml[start..].find(&close)? + start;
-    Some(xml[start..end].trim().to_string())
-}

src/labels/ctrm.rs

@@ -4,8 +4,8 @@
 //! When both exist, language_streams.txt provides structured types while
 //! menu_base.prop provides stream number → button name mapping.
 
-use super::{LabelPurpose, LabelQualifier, StreamLabel, StreamLabelType, vocab};
-use crate::sector::SectorReader;
+use super::{LabelPurpose, LabelQualifier, ParseResult, StreamLabel, StreamLabelType, vocab};
+use crate::sector::SectorSource;
 use crate::udf::UdfFs;
 use std::collections::HashMap;
 
@@ -14,7 +14,7 @@ pub fn detect(udf: &UdfFs) -> bool {
         || super::jar_file_exists(udf, "language_streams.txt")
 }
 
-pub fn parse(reader: &mut dyn SectorReader, udf: &UdfFs) -> Option<Vec<StreamLabel>> {
+pub fn parse(reader: &mut dyn SectorSource, udf: &UdfFs) -> Option<ParseResult> {
     // Try language_streams.txt first (richer structured data)
     let ls_labels = parse_language_streams(reader, udf);
 
@@ -22,12 +22,18 @@ pub fn parse(reader: &mut dyn SectorReader, udf: &UdfFs) -> Option<Vec<StreamLab
     let mb_labels = parse_menu_base(reader, udf);
 
     // If we have both, merge: language_streams for structure, menu_base for names
-    match (ls_labels, mb_labels) {
-        (Some(ls), Some(mb)) => Some(merge(ls, mb)),
-        (Some(ls), None) => Some(ls),
-        (None, Some(mb)) => Some(mb),
-        (None, None) => None,
+    let labels = match (ls_labels, mb_labels) {
+        (Some(ls), Some(mb)) => merge(ls, mb),
+        (Some(ls), None) => ls,
+        (None, Some(mb)) => mb,
+        (None, None) => return None,
+    };
+    if labels.is_empty() {
+        return None;
     }
+    // High confidence: both language_streams.txt and menu_base.prop
+    // are structured key-value formats with documented types.
+    Some(ParseResult::high(labels))
 }
 
 fn merge(ls: Vec<StreamLabel>, mb: Vec<StreamLabel>) -> Vec<StreamLabel> {
@@ -49,7 +55,7 @@ fn merge(ls: Vec<StreamLabel>, mb: Vec<StreamLabel>) -> Vec<StreamLabel> {
 
 // ── language_streams.txt parser ────────────────────────────────────────────
 
-fn parse_language_streams(reader: &mut dyn SectorReader, udf: &UdfFs) -> Option<Vec<StreamLabel>> {
+fn parse_language_streams(reader: &mut dyn SectorSource, udf: &UdfFs) -> Option<Vec<StreamLabel>> {
     let data = super::read_jar_file(reader, udf, "language_streams.txt")?;
     let text = std::str::from_utf8(&data).ok()?;
 
@@ -172,9 +178,167 @@ fn parse_language_streams(reader: &mut dyn SectorReader, udf: &UdfFs) -> Option<
     Some(labels)
 }
 
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    /// Build a minimal menu_base.prop text and run `parse_menu_base`'s
+    /// inner logic via a temporary closure. This isolates the prop
+    /// parsing without needing a SectorSource.
+    fn parse_props(text: &str) -> Vec<StreamLabel> {
+        // Mirror the inner loop of parse_menu_base exactly. Kept
+        // separate so the test doesn't need disc fixtures.
+        use std::collections::HashMap;
+        let mut entries: HashMap<String, HashMap<String, String>> = HashMap::new();
+        for line in text.lines() {
+            let line = line.trim();
+            if line.is_empty() || line.starts_with('#') {
+                continue;
+            }
+            let Some(eq_pos) = line.find('=') else {
+                continue;
+            };
+            let full_key = &line[..eq_pos];
+            let value = &line[eq_pos + 1..];
+            if let Some(dot_pos) = full_key.rfind('.') {
+                entries
+                    .entry(full_key[..dot_pos].to_string())
+                    .or_default()
+                    .insert(full_key[dot_pos + 1..].to_string(), value.to_string());
+            }
+        }
+        let mut labels = Vec::new();
+        for (prefix, props) in &entries {
+            let is_audio = props
+                .get("class")
+                .is_some_and(|c| c.contains("AudioButton"))
+                || prefix.starts_with("audio_");
+            let is_subtitle = props
+                .get("class")
+                .is_some_and(|c| c.contains("SubtitleButton"))
+                || prefix.starts_with("subtitle_");
+            let stream_num_str = props
+                .get("streamNumber")
+                .or_else(|| props.get("audioStream"))
+                .or_else(|| props.get("subtitleStream"));
+            let stream_num: u16 = match stream_num_str.and_then(|s| s.parse().ok()) {
+                Some(n) if n > 0 => n,
+                _ => continue,
+            };
+            if !is_audio && !is_subtitle {
+                continue;
+            }
+            let name = props.get("name").cloned().unwrap_or_default();
+            let purpose = match vocab::purpose(&name) {
+                LabelPurpose::Normal if prefix.contains("comm") => LabelPurpose::Commentary,
+                p => p,
+            };
+            let qualifier = if is_subtitle {
+                vocab::qualifier(&name)
+            } else {
+                LabelQualifier::None
+            };
+            let stream_type = if is_audio {
+                StreamLabelType::Audio
+            } else {
+                StreamLabelType::Subtitle
+            };
+            let language = props
+                .get("audioLanguage")
+                .or_else(|| props.get("subtitleLanguage"))
+                .cloned()
+                .unwrap_or_default();
+            labels.push(StreamLabel {
+                stream_number: stream_num,
+                stream_type,
+                language,
+                name,
+                purpose,
+                qualifier,
+                codec_hint: String::new(),
+                variant: String::new(),
+            });
+        }
+        labels.sort_by_key(|l| (l.stream_type as u8, l.stream_number));
+        labels
+    }
+
+    #[test]
+    fn commentary_via_name() {
+        let labels = parse_props(
+            "audio_1.class=AudioButton\n\
+             audio_1.streamNumber=2\n\
+             audio_1.name=Director's Commentary\n\
+             audio_1.audioLanguage=eng\n",
+        );
+        assert_eq!(labels.len(), 1);
+        assert_eq!(labels[0].purpose, LabelPurpose::Commentary);
+        assert_eq!(labels[0].language, "eng");
+    }
+
+    #[test]
+    fn commentary_via_prefix_when_name_silent() {
+        let labels = parse_props(
+            "audio_commentary_1.class=AudioButton\n\
+             audio_commentary_1.streamNumber=2\n\
+             audio_commentary_1.name=Track 2\n\
+             audio_commentary_1.audioLanguage=eng\n",
+        );
+        assert_eq!(labels[0].purpose, LabelPurpose::Commentary);
+    }
+
+    #[test]
+    fn commenter_does_not_false_match_commentary() {
+        // Regression for the pre-refactor `name.contains("comment")`
+        // bug: this would wrongly classify a "Commenter Pro" track as
+        // Commentary. vocab::purpose enforces a word boundary.
+        let labels = parse_props(
+            "audio_1.class=AudioButton\n\
+             audio_1.streamNumber=2\n\
+             audio_1.name=Commenter Pro Track\n\
+             audio_1.audioLanguage=eng\n",
+        );
+        assert_eq!(labels[0].purpose, LabelPurpose::Normal);
+    }
+
+    #[test]
+    fn descriptive_via_name() {
+        let labels = parse_props(
+            "audio_1.class=AudioButton\n\
+             audio_1.streamNumber=3\n\
+             audio_1.name=English Descriptive Audio\n",
+        );
+        assert_eq!(labels[0].purpose, LabelPurpose::Descriptive);
+    }
+
+    #[test]
+    fn sdh_only_on_subtitles() {
+        // SDH applied to a subtitle stream.
+        let labels = parse_props(
+            "subtitle_1.class=SubtitleButton\n\
+             subtitle_1.streamNumber=4\n\
+             subtitle_1.name=English SDH\n",
+        );
+        assert_eq!(labels[0].qualifier, LabelQualifier::Sdh);
+    }
+
+    #[test]
+    fn sdh_not_applied_to_audio_stream_even_if_name_contains_sdh() {
+        // Audio streams should not pick up SDH (it's a subtitle
+        // concept). Edge case: badly-authored name happens to include
+        // "SDH" — we don't propagate it to audio metadata.
+        let labels = parse_props(
+            "audio_1.class=AudioButton\n\
+             audio_1.streamNumber=5\n\
+             audio_1.name=English SDH (track?)\n",
+        );
+        assert_eq!(labels[0].qualifier, LabelQualifier::None);
+    }
+}
+
 // ── menu_base.prop parser ──────────────────────────────────────────────────
 
-fn parse_menu_base(reader: &mut dyn SectorReader, udf: &UdfFs) -> Option<Vec<StreamLabel>> {
+fn parse_menu_base(reader: &mut dyn SectorSource, udf: &UdfFs) -> Option<Vec<StreamLabel>> {
     let data = super::read_jar_file(reader, udf, "menu_base.prop")?;
     let text = std::str::from_utf8(&data).ok()?;
 
@@ -231,16 +395,20 @@ fn parse_menu_base(reader: &mut dyn SectorReader, udf: &UdfFs) -> Option<Vec<Str
         }
 
         let name = props.get("name").cloned().unwrap_or_default();
-        let name_lower = name.to_lowercase();
 
-        let purpose = if name_lower.contains("comment") || prefix.contains("comm") {
-            LabelPurpose::Commentary
-        } else {
-            LabelPurpose::Normal
+        // Purpose: ask vocab first (word-boundary matched — avoids the
+        // "Commenter" false positive the prior `name.contains("comment")`
+        // had). Then fall back to the structural prefix check
+        // (`audio_commentary.foo`-style keys group commentary streams
+        // regardless of display name).
+        let purpose = match vocab::purpose(&name) {
+            LabelPurpose::Normal if prefix.contains("comm") => LabelPurpose::Commentary,
+            p => p,
         };
 
-        let qualifier = if is_subtitle && name_lower.contains("sdh") {
-            LabelQualifier::Sdh
+        // Qualifier: only apply to subtitles (SDH is a subtitle concept).
+        let qualifier = if is_subtitle {
+            vocab::qualifier(&name)
         } else {
             LabelQualifier::None
         };

src/labels/dbp.rs

@@ -0,0 +1,260 @@
+//! "dbp" framework — Magnolia Pictures BD-J authoring shop (per
+//! `bd-live.magpictures.com` referenced in the disc's
+//! `com/dbp/bluray.MenuXlet.perm`). Detected on UHD discs whose
+//! `/BDMV/JAR/<x>.jar` (top-level, not in a subdir) contains
+//! `com/dbp/` package paths.
+//!
+//! Stream labels live as plain ASCII strings inside compiled `.class`
+//! files in the jar — a quirk of the menu-rendering layer encoding
+//! its TextField positions and content as constant strings the
+//! Java compiler retained in the class string pool. Observed format:
+//!
+//! ```text
+//! LTextField,Audio1,English Dolby Atmos,Fontstrip_Composite,...
+//! RTextField,Audio2,English Descriptive Audio,Fontstrip_Composite,...
+//! HTextField,Subtitle1,English SDH,Fontstrip_Composite,...
+//! ATextField,Subtitle0,None,Fontstrip_Composite,...
+//! ```
+//!
+//! The single uppercase letter before `TextField` is string-pool
+//! prefix noise — the parser anchors on `TextField,` regardless of
+//! what precedes it. `Subtitle0` is the disable-subtitles menu
+//! button and is skipped (not a real subtitle stream).
+//!
+//! ## Implementation
+//!
+//! v2 (2026-05-10): rewritten on top of [`super::class_reader`] —
+//! iterates `CpInfo::Utf8` constant-pool entries instead of raw byte
+//! scanning each class file. Equivalent label coverage (the literal
+//! `TextField,...` strings live in the CP as Utf8 entries), but
+//! structurally cleaner: no false-positive risk from method bytecode
+//! or attribute names happening to contain `TextField,`. Language /
+//! purpose / qualifier classification moved to [`super::vocab`] so all
+//! Java-parser families share one source of truth.
+
+use super::class_reader::CpInfo;
+use super::{ParseResult, StreamLabel, StreamLabelType, jar, vocab};
+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)
+}
+
+pub fn parse(reader: &mut dyn SectorSource, udf: &UdfFs) -> Option<ParseResult> {
+    jar::for_each_jar(reader, udf, |_entry_name, archive| {
+        if !jar::has_path_prefix(archive, "com/dbp/") {
+            return None;
+        }
+        let labels = scan_jar(archive);
+        if labels.is_empty() {
+            None
+        } else {
+            // High confidence: TextField,Audio1,... is a stable anchor
+            // pattern + vocab routes language/purpose/qualifier.
+            Some(ParseResult::high(labels))
+        }
+    })
+}
+
+fn scan_jar(archive: &mut jar::Jar) -> Vec<StreamLabel> {
+    // BTreeMap so we keep the highest-numbered (last-written) label
+    // for each stream slot deterministic across runs. The same
+    // TextField,Audio1,... string can appear in multiple classes
+    // (button-state variants, localization fallbacks). Last write
+    // wins — they should all agree, but the structure is defensive.
+    let mut audios: BTreeMap<u16, String> = BTreeMap::new();
+    let mut subs: BTreeMap<u16, String> = BTreeMap::new();
+
+    jar::for_each_class(archive, |_class_name, class| {
+        for (_idx, cp) in class.constant_pool.iter() {
+            if let CpInfo::Utf8(s) = cp {
+                collect_textfield(s, &mut audios, &mut subs);
+            }
+        }
+    });
+
+    let mut out = Vec::new();
+    for (num, label) in audios {
+        out.push(make_label(num, label, StreamLabelType::Audio));
+    }
+    for (num, label) in subs {
+        out.push(make_label(num, label, StreamLabelType::Subtitle));
+    }
+    out
+}
+
+fn collect_textfield(
+    s: &str,
+    audios: &mut BTreeMap<u16, String>,
+    subs: &mut BTreeMap<u16, String>,
+) {
+    // Anchor on "TextField," — the prefix character before it varies
+    // (string-pool ordering inside compiled Java) and is irrelevant.
+    let Some(idx) = s.find("TextField,") else {
+        return;
+    };
+    let after = &s[idx + "TextField,".len()..];
+    let mut parts = after.splitn(3, ',');
+    let kind_n = parts.next().unwrap_or("").trim();
+    let label = parts.next().unwrap_or("").trim();
+    if label.is_empty() {
+        return;
+    }
+    if let Some(rest) = kind_n.strip_prefix("Audio") {
+        if let Ok(n) = rest.parse::<u16>() {
+            audios.insert(n, label.to_string());
+        }
+    } else if let Some(rest) = kind_n.strip_prefix("Subtitle") {
+        if let Ok(n) = rest.parse::<u16>() {
+            // Subtitle0 is conventionally the "None / Off" disable
+            // button, not an actual subtitle stream.
+            if n > 0 {
+                subs.insert(n, label.to_string());
+            }
+        }
+    }
+}
+
+fn make_label(num: u16, label: String, stream_type: StreamLabelType) -> StreamLabel {
+    let lang_info = vocab::lang(&label);
+    let language = lang_info.map(|l| l.code).unwrap_or("").to_string();
+    let variant = lang_info.map(|l| l.variant).unwrap_or("").to_string();
+    let qualifier = vocab::qualifier(&label);
+    let purpose = vocab::purpose(&label);
+    StreamLabel {
+        stream_number: num,
+        stream_type,
+        language,
+        name: label,
+        purpose,
+        qualifier,
+        codec_hint: String::new(),
+        variant,
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::super::{LabelPurpose, LabelQualifier};
+    use super::*;
+
+    #[test]
+    fn collect_extracts_audio_and_subtitle_indices() {
+        let mut audios = BTreeMap::new();
+        let mut subs = BTreeMap::new();
+        let lines = [
+            "LTextField,Audio1,English Dolby Atmos,Fontstrip_Composite,296,763,275,25,left",
+            "RTextField,Audio2,English Descriptive Audio,Fontstrip_Composite,296,803,275,25,left",
+            "RTextField,Audio3,Spanish 5.1 Dolby Digital,Fontstrip_Composite,296,843,275,25,left",
+            "ATextField,Subtitle0,None,Fontstrip_Composite,1312,843,275,25,left",
+            "HTextField,Subtitle1,English SDH,Fontstrip_Composite,1312,763,275,25,left",
+            "DTextField,Subtitle2,Spanish,Fontstrip_Composite,1312,803,275,25,left",
+        ];
+        for s in &lines {
+            collect_textfield(s, &mut audios, &mut subs);
+        }
+        assert_eq!(audios.len(), 3);
+        assert_eq!(audios[&1], "English Dolby Atmos");
+        assert_eq!(audios[&2], "English Descriptive Audio");
+        assert_eq!(audios[&3], "Spanish 5.1 Dolby Digital");
+        // Subtitle0 ("None") is skipped — disable button, not a stream.
+        assert_eq!(subs.len(), 2);
+        assert_eq!(subs[&1], "English SDH");
+        assert_eq!(subs[&2], "Spanish");
+    }
+
+    #[test]
+    fn collect_ignores_non_textfield_strings() {
+        let mut audios = BTreeMap::new();
+        let mut subs = BTreeMap::new();
+        for s in [
+            "GraphicButton,SU_Audio",
+            "AudioMenu",
+            "CommentaryMenuAlternateScenes",
+            "PrimaryAudioControl",
+        ] {
+            collect_textfield(s, &mut audios, &mut subs);
+        }
+        assert!(audios.is_empty());
+        assert!(subs.is_empty());
+    }
+
+    #[test]
+    fn make_label_routes_via_vocab() {
+        let l = make_label(1, "English SDH".to_string(), StreamLabelType::Subtitle);
+        assert_eq!(l.language, "eng");
+        assert_eq!(l.qualifier, LabelQualifier::Sdh);
+        assert_eq!(l.purpose, LabelPurpose::Normal);
+    }
+
+    #[test]
+    fn make_label_descriptive_audio() {
+        let l = make_label(
+            2,
+            "English Descriptive Audio".to_string(),
+            StreamLabelType::Audio,
+        );
+        assert_eq!(l.language, "eng");
+        assert_eq!(l.purpose, LabelPurpose::Descriptive);
+    }
+
+    #[test]
+    fn make_label_commentary() {
+        let l = make_label(
+            3,
+            "English Director's Commentary".to_string(),
+            StreamLabelType::Audio,
+        );
+        assert_eq!(l.language, "eng");
+        assert_eq!(l.purpose, LabelPurpose::Commentary);
+    }
+
+    #[test]
+    fn make_label_compound_languages_populate_variant() {
+        let brazilian = make_label(1, "Brazilian Portuguese 5.1".into(), StreamLabelType::Audio);
+        assert_eq!(brazilian.language, "por");
+        assert_eq!(brazilian.variant, "Brazilian");
+
+        let castilian = make_label(1, "Castilian Spanish".into(), StreamLabelType::Audio);
+        assert_eq!(castilian.language, "spa");
+        assert_eq!(castilian.variant, "Castilian");
+
+        let canadian = make_label(
+            1,
+            "Canadian French Dolby Digital".into(),
+            StreamLabelType::Audio,
+        );
+        assert_eq!(canadian.language, "fra");
+        assert_eq!(canadian.variant, "Canadian");
+    }
+
+    #[test]
+    fn make_label_bare_language_has_empty_variant() {
+        let l = make_label(1, "English Dolby Atmos".into(), StreamLabelType::Audio);
+        assert_eq!(l.language, "eng");
+        assert_eq!(l.variant, "");
+    }
+
+    #[test]
+    fn make_label_unknown_language_is_empty() {
+        // vocab::lang returns None — make_label converts both fields to "".
+        let l = make_label(1, "Klingon Dolby Atmos".into(), StreamLabelType::Audio);
+        assert_eq!(l.language, "");
+        assert_eq!(l.variant, "");
+    }
+
+    #[test]
+    fn make_label_rnib_descriptive_service() {
+        let l = make_label(1, "English RNIB".into(), StreamLabelType::Subtitle);
+        assert_eq!(l.language, "eng");
+        assert_eq!(l.qualifier, LabelQualifier::DescriptiveService);
+    }
+}

src/labels/jar.rs

@@ -0,0 +1,151 @@
+//! BD-J jar utilities — common scaffolding for parsers that read
+//! `/BDMV/JAR/*.jar`.
+//!
+//! Composes with [`class_reader`](super::class_reader) for structured
+//! `.class` access. Used by `dbp` (string-pool scan via constant pool)
+//! and `deluxe` (bytecode pattern matching) — those parsers express
+//! "open every top-level jar, look at every .class inside" without
+//! repeating the zip-archive boilerplate.
+
+// `try_each_class` is staged for `labels::deluxe`, which needs the
+// early-return form to short-circuit class iteration on a match.
+// dead-code allow comes off when deluxe lands.
+#![allow(dead_code)]
+
+use super::class_reader::ClassFile;
+use crate::sector::SectorSource;
+use crate::udf::UdfFs;
+use std::io::Cursor;
+use zip::ZipArchive;
+
+/// In-memory zip archive: backed by a `Vec<u8>` read from UDF. Owns
+/// the buffer; callers pass it to [`has_path_prefix`], [`for_each_class`],
+/// 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.
+///
+/// "Top-level" means entries directly under `/BDMV/JAR/`, not nested
+/// under a subdir. (Pixelogic, Criterion, Paramount, etc. put their
+/// data files inside `/BDMV/JAR/<x>/`; dbp and Deluxe put their jar
+/// directly at `/BDMV/JAR/<name>.jar`.)
+///
+/// Entries that fail to read from UDF or that aren't valid zips are
+/// silently skipped — same defensive shape as the existing dbp parser.
+pub fn for_each_jar<R, F>(reader: &mut dyn SectorSource, udf: &UdfFs, mut f: F) -> Option<R>
+where
+    F: FnMut(&str, &mut Jar) -> Option<R>,
+{
+    let jar_dir = udf.find_dir("/BDMV/JAR")?;
+    for entry in &jar_dir.entries {
+        if entry.is_dir {
+            continue;
+        }
+        if !entry.name.to_lowercase().ends_with(".jar") {
+            continue;
+        }
+        let path = format!("/BDMV/JAR/{}", entry.name);
+        let Ok(bytes) = udf.read_file(reader, &path) else {
+            continue;
+        };
+        let Ok(mut archive) = ZipArchive::new(Cursor::new(bytes)) else {
+            continue;
+        };
+        if let Some(r) = f(&entry.name, &mut archive) {
+            return Some(r);
+        }
+    }
+    None
+}
+
+/// True if any entry in this jar's central directory starts with
+/// `prefix`. Fast — only reads filenames, never extracts bytes.
+///
+/// Used by parsers as a cheap "is this MY framework's jar?" check
+/// (e.g. `has_path_prefix(archive, "com/dbp/")` for dbp,
+/// `has_path_prefix(archive, "com/bydeluxe/")` for Deluxe).
+pub fn has_path_prefix(archive: &mut Jar, prefix: &str) -> bool {
+    for i in 0..archive.len() {
+        if let Ok(f) = archive.by_index(i) {
+            if f.name().starts_with(prefix) {
+                return true;
+            }
+        }
+    }
+    false
+}
+
+/// Iterate every `.class` entry in the jar, parse it with
+/// [`class_reader`], and call `f` with `(entry_name, &ClassFile)`.
+///
+/// Entries that fail to read or parse are silently skipped — this is
+/// label-extraction code, robustness matters more than completeness.
+/// Callers that need to know which classes failed should use the
+/// lower-level [`class_reader`] API directly.
+pub fn for_each_class<F>(archive: &mut Jar, mut f: F)
+where
+    F: FnMut(&str, &ClassFile),
+{
+    for i in 0..archive.len() {
+        let Ok(mut entry) = archive.by_index(i) else {
+            continue;
+        };
+        if !entry.name().ends_with(".class") {
+            continue;
+        }
+        let name = entry.name().to_string();
+        let mut bytes = Vec::with_capacity(entry.size() as usize);
+        if std::io::Read::read_to_end(&mut entry, &mut bytes).is_err() {
+            continue;
+        }
+        let Ok(class) = ClassFile::parse(&bytes) else {
+            continue;
+        };
+        f(&name, &class);
+    }
+}
+
+/// Like [`for_each_class`] but allows the callback to short-circuit
+/// iteration. Returns the first `Some(R)` the callback produces.
+pub fn try_each_class<R, F>(archive: &mut Jar, mut f: F) -> Option<R>
+where
+    F: FnMut(&str, &ClassFile) -> Option<R>,
+{
+    for i in 0..archive.len() {
+        let Ok(mut entry) = archive.by_index(i) else {
+            continue;
+        };
+        if !entry.name().ends_with(".class") {
+            continue;
+        }
+        let name = entry.name().to_string();
+        let mut bytes = Vec::with_capacity(entry.size() as usize);
+        if std::io::Read::read_to_end(&mut entry, &mut bytes).is_err() {
+            continue;
+        }
+        let Ok(class) = ClassFile::parse(&bytes) else {
+            continue;
+        };
+        if let Some(r) = f(&name, &class) {
+            return Some(r);
+        }
+    }
+    None
+}

src/labels/mpls_universal.rs

@@ -0,0 +1,597 @@
+//! Universal MPLS-based stream labels.
+//!
+//! Unlike the framework-specific parsers in this directory (dbp,
+//! pixelogic, ctrm, criterion, ...), this module is the *floor*:
+//! every Blu-ray ships with MPLS playlists under `/BDMV/PLAYLIST/`,
+//! and every MPLS file has an STN table with per-stream ISO 639-2
+//! language codes plus coding-type / channel-layout / sample-rate
+//! bytes from the BD spec.
+//!
+//! The framework parsers extract richer editorial labels ("English
+//! Dolby Atmos", "Director's Commentary") when the disc was authored
+//! with a recognized tool. When none of them match (e.g. a "no BD-J"
+//! disc, or an authoring framework we haven't catalogued), MPLS still
+//! gives us language + codec on every stream — enough to render
+//! something more useful than the bare PID.
+//!
+//! Output confidence is Low: MPLS carries language + codec but
+//! never purpose/qualifier info (no way to tell "Commentary" from
+//! "Normal" from the STN table alone). Higher-confidence framework
+//! parsers, when present, always win on the registry's max-by-confidence
+//! tiebreaker — MPLS is only chosen when nothing else matched.
+
+use super::{
+    LabelPurpose, LabelQualifier, ParseResult, StreamLabel, StreamLabelType,
+    vocab::{self, LangInfo},
+};
+use crate::sector::SectorSource;
+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 {
+    let Some(dir) = udf.find_dir("/BDMV/PLAYLIST") else {
+        return false;
+    };
+    dir.entries
+        .iter()
+        .any(|e| !e.is_dir && has_mpls_extension(&e.name))
+}
+
+/// Walk every `*.mpls` in `/BDMV/PLAYLIST/`, parse it, and convert
+/// each StreamEntry to a [`StreamLabel`]. Streams shared across
+/// playlists (same PID) are deduped.
+///
+/// Returns `None` if no labels could be produced (e.g. no .mpls files
+/// parsed successfully, or every parsed stream was a type we skip
+/// like IG / DV EL).
+pub fn parse(reader: &mut dyn SectorSource, udf: &UdfFs) -> Option<ParseResult> {
+    let playlist_dir = udf.find_dir("/BDMV/PLAYLIST")?;
+
+    // Collect mpls filenames first so we don't hold a borrow on udf
+    // while we call udf.read_file (which takes &self).
+    let mpls_names: Vec<String> = playlist_dir
+        .entries
+        .iter()
+        .filter(|e| !e.is_dir && has_mpls_extension(&e.name))
+        .map(|e| e.name.clone())
+        .collect();
+
+    if mpls_names.is_empty() {
+        return None;
+    }
+
+    let mut labels: Vec<StreamLabel> = Vec::new();
+    // (stream_type_tag, language, codec_hint, pid) — PID is the
+    // canonical "same physical stream" key; type+lang+codec round
+    // out the rare case where two distinct logical streams happen
+    // to share a PID across playlists with different metadata.
+    let mut seen: Vec<(u8, String, String, u16)> = Vec::new();
+
+    // Global 1-based counters keyed by StreamLabelType. Incremented
+    // only when an entry survives dedup, so stream_numbers are dense
+    // (1, 2, 3, ...) per type across the whole disc — not reset per
+    // playlist. A disc with 2 MPLS files that each list the same
+    // 8 audio streams ends up with audio_1..audio_8, not audio_1..
+    // audio_16 or audio_1..audio_8 with audio_1 duplicated.
+    let mut audio_idx: u16 = 0;
+    let mut sub_idx: u16 = 0;
+
+    for name in &mpls_names {
+        let path = format!("/BDMV/PLAYLIST/{}", name);
+        let Ok(data) = udf.read_file(reader, &path) else {
+            continue;
+        };
+        let Ok(playlist) = crate::mpls::parse(&data) else {
+            continue;
+        };
+
+        for entry in &playlist.streams {
+            let label_type = match entry.stream_type {
+                2 | 5 => StreamLabelType::Audio, // primary + secondary audio
+                3 => StreamLabelType::Subtitle,  // PG subtitle
+                // 1 = primary video, 6 = secondary video, 7 = DV EL
+                //     → no StreamLabelType variant for video, skip.
+                // 4 = IG (interactive graphics) — not a user-facing
+                //     stream, skip.
+                _ => continue,
+            };
+
+            let language = normalize_language(&entry.language);
+            let name = language_display_name(&language);
+            let codec_hint = build_codec_hint(label_type, entry);
+
+            let type_tag = type_tag(label_type);
+            let key = (type_tag, language.clone(), codec_hint.clone(), entry.pid);
+            if seen.contains(&key) {
+                continue;
+            }
+            seen.push(key);
+
+            let stream_number = match label_type {
+                StreamLabelType::Audio => {
+                    audio_idx += 1;
+                    audio_idx
+                }
+                StreamLabelType::Subtitle => {
+                    sub_idx += 1;
+                    sub_idx
+                }
+            };
+
+            labels.push(StreamLabel {
+                stream_number,
+                stream_type: label_type,
+                language,
+                name,
+                purpose: LabelPurpose::Normal,
+                qualifier: LabelQualifier::None,
+                codec_hint,
+                variant: String::new(),
+            });
+        }
+    }
+
+    if labels.is_empty() {
+        return None;
+    }
+
+    // MPLS gives language + codec but never editorial info (no
+    // commentary/SDH/director's cut). Low confidence means framework
+    // parsers (paramount, criterion, pixelogic, ctrm, dbp, deluxe) always
+    // win when they match. MPLS only gets chosen as the parser when
+    // nothing else fired — exactly the universal-fallback role we want.
+    Some(ParseResult::low(labels))
+}
+
+fn has_mpls_extension(name: &str) -> bool {
+    // Case-insensitive ".mpls" suffix. Some discs use uppercase,
+    // some lowercase; UDF filenames preserve case but we don't.
+    let n = name.len();
+    if n < 5 {
+        return false;
+    }
+    name[n - 5..].eq_ignore_ascii_case(".mpls")
+}
+
+/// Lowercase + trim the raw 3-char ISO 639-2 code. If the lowered
+/// string maps via [`vocab::lang`] (it won't for plain "eng" — that
+/// matcher is for English-name fragments, not codes) use its
+/// canonical code; otherwise return the trimmed lowercase string.
+fn normalize_language(raw: &str) -> String {
+    let trimmed = raw.trim().to_ascii_lowercase();
+    if trimmed.is_empty() {
+        return String::new();
+    }
+    // vocab::lang() matches free-form English names, not ISO 639-2
+    // codes — so for the typical MPLS payload ("eng", "fra", ...)
+    // it returns None and we keep the trimmed code.
+    if let Some(LangInfo { code, .. }) = vocab::lang(&trimmed) {
+        return code.to_string();
+    }
+    trimmed
+}
+
+/// Human-readable English name for an ISO 639-2 code, or empty if
+/// the code is unknown. Kept inline rather than in vocab because
+/// vocab is the *reverse* mapping (name → code).
+pub(crate) fn language_display_name(iso: &str) -> String {
+    match iso {
+        "eng" => "English",
+        "fra" | "fre" => "French",
+        "spa" => "Spanish",
+        "deu" | "ger" => "German",
+        "ita" => "Italian",
+        "jpn" => "Japanese",
+        "zho" | "chi" => "Chinese",
+        "kor" => "Korean",
+        "por" => "Portuguese",
+        "pol" => "Polish",
+        "ces" | "cze" => "Czech",
+        "hun" => "Hungarian",
+        "nld" | "dut" => "Dutch",
+        "ara" => "Arabic",
+        "hin" => "Hindi",
+        "tur" => "Turkish",
+        "tha" => "Thai",
+        "swe" => "Swedish",
+        "nor" => "Norwegian",
+        "dan" => "Danish",
+        "fin" => "Finnish",
+        "heb" => "Hebrew",
+        "rus" => "Russian",
+        "ell" | "gre" => "Greek",
+        "vie" => "Vietnamese",
+        "ind" => "Indonesian",
+        "msa" | "may" => "Malay",
+        "ukr" => "Ukrainian",
+        "ron" | "rum" => "Romanian",
+        "bul" => "Bulgarian",
+        "hrv" => "Croatian",
+        "srp" => "Serbian",
+        "slk" | "slo" => "Slovak",
+        "slv" => "Slovenian",
+        "est" => "Estonian",
+        "lav" => "Latvian",
+        "lit" => "Lithuanian",
+        "isl" | "ice" => "Icelandic",
+        "eus" | "baq" => "Basque",
+        "cat" => "Catalan",
+        "glg" => "Galician",
+        _ => "",
+    }
+    .to_string()
+}
+
+/// Map BD coding_type byte → codec name. Returns empty for unknown
+/// bytes (the table covers everything the spec defines, but unknown
+/// values are still possible on malformed discs).
+pub(crate) fn codec_name(coding_type: u8) -> &'static str {
+    match coding_type {
+        0x02 => "MPEG-2",
+        0x1B => "H.264",
+        0x24 => "HEVC",
+        0x80 => "LPCM",
+        0x81 => "AC-3",
+        0x82 => "DTS",
+        0x83 => "TrueHD",
+        0x84 => "AC-3+",
+        0x85 => "DTS-HD",
+        0x86 => "DTS-HD MA",
+        0x90 => "PG",
+        0x91 => "IG",
+        0xA1 => "AC-3+ Secondary",
+        0xA2 => "DTS-HD Secondary",
+        _ => "",
+    }
+}
+
+/// Build the final `codec_hint`. For audio streams, optionally
+/// append " <channels>" and/or " <rate>" suffixes. Sample rate is
+/// only spelled out for non-48k (the universal default).
+fn build_codec_hint(label_type: StreamLabelType, entry: &crate::mpls::StreamEntry) -> String {
+    let base = codec_name(entry.coding_type);
+    if base.is_empty() {
+        return String::new();
+    }
+
+    if label_type != StreamLabelType::Audio {
+        return base.to_string();
+    }
+
+    let mut out = base.to_string();
+
+    let channels = match entry.audio_format {
+        1 => Some("mono"),
+        3 => Some("2.0"),
+        6 => Some("5.1"),
+        12 => Some("7.1"),
+        _ => None,
+    };
+    if let Some(ch) = channels {
+        out.push(' ');
+        out.push_str(ch);
+    }
+
+    // 1 = 48 kHz (universal default, omit). Only call out higher rates.
+    let rate = match entry.audio_rate {
+        4 => Some("96kHz"),
+        5 => Some("192kHz"),
+        _ => None,
+    };
+    if let Some(r) = rate {
+        out.push(' ');
+        out.push_str(r);
+    }
+
+    out
+}
+
+/// Dedup-tag for the label type. `u8` instead of `StreamLabelType`
+/// itself because the enum does not derive `Hash` / `Eq`-by-discriminant
+/// in a way that we want to couple to (and `==` works fine for the
+/// linear `Vec::contains` lookup we do).
+fn type_tag(t: StreamLabelType) -> u8 {
+    match t {
+        StreamLabelType::Audio => 1,
+        StreamLabelType::Subtitle => 2,
+    }
+}
+
+// ── Tests ────────────────────────────────────────────────────────────
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use crate::mpls::{Playlist, StreamEntry};
+
+    fn audio_entry(pid: u16, coding: u8, fmt: u8, rate: u8, lang: &str) -> StreamEntry {
+        StreamEntry {
+            stream_type: 2,
+            pid,
+            coding_type: coding,
+            video_format: 0,
+            video_rate: 0,
+            audio_format: fmt,
+            audio_rate: rate,
+            language: lang.to_string(),
+            dynamic_range: 0,
+            color_space: 0,
+            secondary: false,
+        }
+    }
+
+    fn pg_entry(pid: u16, lang: &str) -> StreamEntry {
+        StreamEntry {
+            stream_type: 3,
+            pid,
+            coding_type: 0x90,
+            video_format: 0,
+            video_rate: 0,
+            audio_format: 0,
+            audio_rate: 0,
+            language: lang.to_string(),
+            dynamic_range: 0,
+            color_space: 0,
+            secondary: false,
+        }
+    }
+
+    fn playlist_with(streams: Vec<StreamEntry>) -> Playlist {
+        Playlist {
+            version: "0200".to_string(),
+            play_items: Vec::new(),
+            streams,
+            marks: Vec::new(),
+        }
+    }
+
+    /// Drive the same conversion logic that `parse()` runs on real
+    /// disc data, but starting from already-parsed Playlists so we
+    /// don't have to synthesize valid MPLS bytes.
+    fn labels_from_playlists(playlists: &[Playlist]) -> Vec<StreamLabel> {
+        let mut labels: Vec<StreamLabel> = Vec::new();
+        let mut seen: Vec<(u8, String, String, u16)> = Vec::new();
+
+        for playlist in playlists {
+            let mut audio_idx: u16 = 0;
+            let mut sub_idx: u16 = 0;
+
+            for entry in &playlist.streams {
+                let label_type = match entry.stream_type {
+                    2 | 5 => StreamLabelType::Audio,
+                    3 => StreamLabelType::Subtitle,
+                    _ => continue,
+                };
+                let stream_number = match label_type {
+                    StreamLabelType::Audio => {
+                        audio_idx += 1;
+                        audio_idx
+                    }
+                    StreamLabelType::Subtitle => {
+                        sub_idx += 1;
+                        sub_idx
+                    }
+                };
+                let language = normalize_language(&entry.language);
+                let name = language_display_name(&language);
+                let codec_hint = build_codec_hint(label_type, entry);
+                let key = (
+                    type_tag(label_type),
+                    language.clone(),
+                    codec_hint.clone(),
+                    entry.pid,
+                );
+                if seen.contains(&key) {
+                    continue;
+                }
+                seen.push(key);
+                labels.push(StreamLabel {
+                    stream_number,
+                    stream_type: label_type,
+                    language,
+                    name,
+                    purpose: LabelPurpose::Normal,
+                    qualifier: LabelQualifier::None,
+                    codec_hint,
+                    variant: String::new(),
+                });
+            }
+        }
+        labels
+    }
+
+    #[test]
+    fn mpls_audio_streams_become_labels() {
+        // Two audio streams: English TrueHD 7.1 48k, French AC-3 5.1 48k.
+        let pl = playlist_with(vec![
+            audio_entry(0x1100, 0x83, 12, 1, "eng"),
+            audio_entry(0x1101, 0x81, 6, 1, "fra"),
+        ]);
+        let labels = labels_from_playlists(&[pl]);
+        assert_eq!(labels.len(), 2);
+
+        // English TrueHD 7.1
+        let a = &labels[0];
+        assert_eq!(a.stream_type, StreamLabelType::Audio);
+        assert_eq!(a.stream_number, 1);
+        assert_eq!(a.language, "eng");
+        assert_eq!(a.name, "English");
+        assert_eq!(a.codec_hint, "TrueHD 7.1");
+        assert_eq!(a.purpose, LabelPurpose::Normal);
+        assert_eq!(a.qualifier, LabelQualifier::None);
+        assert_eq!(a.variant, "");
+
+        // French AC-3 5.1
+        let b = &labels[1];
+        assert_eq!(b.stream_type, StreamLabelType::Audio);
+        assert_eq!(b.stream_number, 2);
+        assert_eq!(b.language, "fra");
+        assert_eq!(b.name, "French");
+        assert_eq!(b.codec_hint, "AC-3 5.1");
+    }
+
+    #[test]
+    fn mpls_pg_streams_become_subtitle_labels() {
+        let pl = playlist_with(vec![
+            pg_entry(0x1200, "eng"),
+            pg_entry(0x1201, "spa"),
+            pg_entry(0x1202, "fra"),
+        ]);
+        let labels = labels_from_playlists(&[pl]);
+        assert_eq!(labels.len(), 3);
+        for label in &labels {
+            assert_eq!(label.stream_type, StreamLabelType::Subtitle);
+            assert_eq!(label.codec_hint, "PG");
+        }
+        assert_eq!(labels[0].stream_number, 1);
+        assert_eq!(labels[0].language, "eng");
+        assert_eq!(labels[0].name, "English");
+        assert_eq!(labels[1].stream_number, 2);
+        assert_eq!(labels[1].language, "spa");
+        assert_eq!(labels[1].name, "Spanish");
+        assert_eq!(labels[2].stream_number, 3);
+        assert_eq!(labels[2].language, "fra");
+    }
+
+    #[test]
+    fn dedup_streams_across_playlists() {
+        // Two playlists, same English TrueHD 7.1 PID 0x1100 in both.
+        // Expect one Audio label, not two.
+        let pl1 = playlist_with(vec![
+            audio_entry(0x1100, 0x83, 12, 1, "eng"),
+            audio_entry(0x1101, 0x81, 6, 1, "fra"),
+        ]);
+        let pl2 = playlist_with(vec![
+            audio_entry(0x1100, 0x83, 12, 1, "eng"), // duplicate
+            audio_entry(0x1102, 0x82, 6, 1, "deu"),  // new
+        ]);
+        let labels = labels_from_playlists(&[pl1, pl2]);
+        // Expected: eng@0x1100, fra@0x1101, deu@0x1102 — three uniques.
+        assert_eq!(labels.len(), 3);
+        // PID isn't stored on StreamLabel, so assert on the surviving
+        // language set instead.
+        let mut langs: Vec<String> = labels.iter().map(|l| l.language.clone()).collect();
+        langs.sort();
+        assert_eq!(langs, vec!["deu", "eng", "fra"]);
+    }
+
+    #[test]
+    fn coding_type_to_codec_hint_table() {
+        // Spot-check every entry in the spec table. Audio entries
+        // come back bare (no channels/rate set) so codec_hint is the
+        // codec name alone.
+        let cases: &[(u8, &str)] = &[
+            (0x02, "MPEG-2"),
+            (0x1B, "H.264"),
+            (0x24, "HEVC"),
+            (0x80, "LPCM"),
+            (0x81, "AC-3"),
+            (0x82, "DTS"),
+            (0x83, "TrueHD"),
+            (0x84, "AC-3+"),
+            (0x85, "DTS-HD"),
+            (0x86, "DTS-HD MA"),
+            (0x90, "PG"),
+            (0x91, "IG"),
+            (0xA1, "AC-3+ Secondary"),
+            (0xA2, "DTS-HD Secondary"),
+        ];
+        for (ct, expected) in cases {
+            assert_eq!(
+                codec_name(*ct),
+                *expected,
+                "coding_type 0x{:02X} should map to {}",
+                ct,
+                expected
+            );
+        }
+        // Unknown bytes return empty.
+        assert_eq!(codec_name(0x00), "");
+        assert_eq!(codec_name(0xFF), "");
+    }
+
+    #[test]
+    fn audio_format_appends_channel_layout() {
+        let mono = audio_entry(1, 0x83, 1, 1, "eng");
+        let stereo = audio_entry(2, 0x83, 3, 1, "eng");
+        let surround_51 = audio_entry(3, 0x83, 6, 1, "eng");
+        let surround_71 = audio_entry(4, 0x83, 12, 1, "eng");
+        let unknown = audio_entry(5, 0x83, 0, 1, "eng");
+        assert_eq!(
+            build_codec_hint(StreamLabelType::Audio, &mono),
+            "TrueHD mono"
+        );
+        assert_eq!(
+            build_codec_hint(StreamLabelType::Audio, &stereo),
+            "TrueHD 2.0"
+        );
+        assert_eq!(
+            build_codec_hint(StreamLabelType::Audio, &surround_51),
+            "TrueHD 5.1"
+        );
+        assert_eq!(
+            build_codec_hint(StreamLabelType::Audio, &surround_71),
+            "TrueHD 7.1"
+        );
+        assert_eq!(build_codec_hint(StreamLabelType::Audio, &unknown), "TrueHD");
+    }
+
+    #[test]
+    fn audio_rate_only_shows_above_48k() {
+        // 48 kHz (rate=1) is the universal default → not surfaced.
+        let r48 = audio_entry(1, 0x83, 6, 1, "eng");
+        // 96 kHz (rate=4) → surfaced.
+        let r96 = audio_entry(2, 0x83, 6, 4, "eng");
+        // 192 kHz (rate=5) → surfaced.
+        let r192 = audio_entry(3, 0x83, 6, 5, "eng");
+        assert_eq!(build_codec_hint(StreamLabelType::Audio, &r48), "TrueHD 5.1");
+        assert_eq!(
+            build_codec_hint(StreamLabelType::Audio, &r96),
+            "TrueHD 5.1 96kHz"
+        );
+        assert_eq!(
+            build_codec_hint(StreamLabelType::Audio, &r192),
+            "TrueHD 5.1 192kHz"
+        );
+    }
+
+    #[test]
+    fn unknown_iso_code_passes_through_without_display_name() {
+        // Made-up code: keep the raw lowercase code as `language`,
+        // but `name` is empty because we don't know it.
+        let pl = playlist_with(vec![audio_entry(0x1100, 0x83, 6, 1, "xyz")]);
+        let labels = labels_from_playlists(&[pl]);
+        assert_eq!(labels.len(), 1);
+        assert_eq!(labels[0].language, "xyz");
+        assert_eq!(labels[0].name, "");
+    }
+
+    #[test]
+    fn ig_and_dv_streams_are_skipped() {
+        // stream_type 4 = IG, 7 = DV EL — both must not surface.
+        let mut ig = pg_entry(0x1400, "eng");
+        ig.stream_type = 4;
+        let mut dv = audio_entry(0x1011, 0x24, 0, 0, "");
+        dv.stream_type = 7;
+        let pl = playlist_with(vec![ig, dv]);
+        let labels = labels_from_playlists(&[pl]);
+        assert!(labels.is_empty());
+    }
+
+    #[test]
+    fn secondary_audio_becomes_audio_label() {
+        // stream_type 5 = secondary audio. The conversion should
+        // still produce an Audio label (the registry's apply path
+        // can ignore secondary if it wants — this module just
+        // surfaces what's there).
+        let mut sec = audio_entry(0x1A00, 0x83, 3, 1, "eng");
+        sec.stream_type = 5;
+        sec.secondary = true;
+        let pl = playlist_with(vec![sec]);
+        let labels = labels_from_playlists(&[pl]);
+        assert_eq!(labels.len(), 1);
+        assert_eq!(labels[0].stream_type, StreamLabelType::Audio);
+        assert_eq!(labels[0].codec_hint, "TrueHD 2.0");
+    }
+}

src/labels/paramount.rs

@@ -12,15 +12,15 @@
 //!   sub_com1_idx="23,24,25" />
 //! ```
 
-use super::{LabelPurpose, LabelQualifier, StreamLabel, StreamLabelType};
-use crate::sector::SectorReader;
+use super::{LabelPurpose, LabelQualifier, ParseResult, StreamLabel, StreamLabelType, xml};
+use crate::sector::SectorSource;
 use crate::udf::UdfFs;
 
 pub fn detect(udf: &UdfFs) -> bool {
     super::jar_file_exists(udf, "playlists.xml")
 }
 
-pub fn parse(reader: &mut dyn SectorReader, udf: &UdfFs) -> Option<Vec<StreamLabel>> {
+pub fn parse(reader: &mut dyn SectorSource, udf: &UdfFs) -> Option<ParseResult> {
     let data = super::read_jar_file(reader, udf, "playlists.xml")?;
     let text = std::str::from_utf8(&data).ok()?;
 
@@ -30,8 +30,8 @@ pub fn parse(reader: &mut dyn SectorReader, udf: &UdfFs) -> Option<Vec<StreamLab
     let mut labels = Vec::new();
 
     // Parse audio streams
-    if let Some(aud) = extract_attr(&feature, "aud") {
-        let com_idx = extract_attr(&feature, "aud_com1_idx").and_then(|s| s.parse::<usize>().ok());
+    if let Some(aud) = xml::attr(&feature, "aud") {
+        let com_idx = xml::attr(&feature, "aud_com1_idx").and_then(|s| s.parse::<usize>().ok());
 
         for (i, lang) in aud.split(',').enumerate() {
             let lang = lang.trim();
@@ -57,12 +57,12 @@ pub fn parse(reader: &mut dyn SectorReader, udf: &UdfFs) -> Option<Vec<StreamLab
     }
 
     // Parse subtitle streams
-    if let Some(sub) = extract_attr(&feature, "sub") {
-        let forced: Vec<bool> = extract_attr(&feature, "forced_sub")
+    if let Some(sub) = xml::attr(&feature, "sub") {
+        let forced: Vec<bool> = xml::attr(&feature, "forced_sub")
             .map(|s| s.split(',').map(|f| f.trim() == "1").collect())
             .unwrap_or_default();
 
-        let com_indices: Vec<usize> = extract_attr(&feature, "sub_com1_idx")
+        let com_indices: Vec<usize> = xml::attr(&feature, "sub_com1_idx")
             .map(|s| s.split(',').filter_map(|i| i.trim().parse().ok()).collect())
             .unwrap_or_default();
 
@@ -100,32 +100,29 @@ pub fn parse(reader: &mut dyn SectorReader, udf: &UdfFs) -> Option<Vec<StreamLab
     if labels.is_empty() {
         return None;
     }
-    Some(labels)
+    // High confidence: paramount's playlists.xml is fully structured
+    // and we extract every documented field.
+    Some(ParseResult::high(labels))
 }
 
 /// Find the feature playlist element (the one with the most audio tracks).
-fn find_feature_playlist(xml: &str) -> Option<String> {
+fn find_feature_playlist(text: &str) -> Option<String> {
     let mut best: Option<String> = None;
     let mut best_aud_count = 0;
+    let mut from = 0;
 
-    let mut pos = 0;
-    while let Some(start) = xml[pos..].find("<playlist ") {
-        let abs_start = pos + start;
-        let end = match xml[abs_start..].find("/>") {
-            Some(p) => abs_start + p + 2,
-            None => break,
-        };
-        let element = &xml[abs_start..end];
+    while let Some((start, end)) = xml::find_element(text, "playlist", from) {
+        let element = &text[start..end];
 
-        // Prefer name="Feature" explicitly
-        if let Some(name) = extract_attr(element, "name") {
+        // Prefer name="Feature" explicitly.
+        if let Some(name) = xml::attr(element, "name") {
             if name.eq_ignore_ascii_case("Feature") {
                 return Some(element.to_string());
             }
         }
 
-        // Otherwise pick the one with the most audio streams
-        if let Some(aud) = extract_attr(element, "aud") {
+        // Otherwise pick the one with the most audio streams.
+        if let Some(aud) = xml::attr(element, "aud") {
             let count = aud.split(',').count();
             if count > best_aud_count {
                 best_aud_count = count;
@@ -133,15 +130,7 @@ fn find_feature_playlist(xml: &str) -> Option<String> {
             }
         }
 
-        pos = end;
+        from = end;
     }
     best
 }
-
-/// Extract an XML attribute value from an element string.
-fn extract_attr(element: &str, name: &str) -> Option<String> {
-    let needle = format!("{name}=\"");
-    let start = element.find(&needle)? + needle.len();
-    let end = element[start..].find('"')? + start;
-    Some(element[start..end].to_string())
-}

src/labels/pixelogic.rs

@@ -5,9 +5,13 @@
 //!
 //! Token format: `{lang}_{codec?}_{purpose?}_{region?}_`
 
-use super::{LabelPurpose, LabelQualifier, StreamLabel, StreamLabelType, vocab};
-use crate::sector::SectorReader;
+use super::{
+    Confidence, LabelPurpose, LabelQualifier, ParseResult, StreamLabel, StreamLabelType, text,
+    vocab,
+};
+use crate::sector::SectorSource;
 use crate::udf::UdfFs;
+use std::sync::atomic::{AtomicBool, Ordering};
 
 /// Known audio codec tokens
 const AUDIO_CODECS: &[&str] = &["MLP", "AC3", "DTS", "DDL", "WAV", "AC"];
@@ -20,18 +24,60 @@ pub fn detect(udf: &UdfFs) -> bool {
     super::jar_file_exists(udf, "bluray_project.bin")
 }
 
-pub fn parse(reader: &mut dyn SectorReader, udf: &UdfFs) -> Option<Vec<StreamLabel>> {
+pub fn parse(reader: &mut dyn SectorSource, udf: &UdfFs) -> Option<ParseResult> {
     let data = super::read_jar_file(reader, udf, "bluray_project.bin")?;
-    let strings = extract_strings(&data);
+    // min_len=4 matches the prior local extract_strings impl. The token
+    // grammar is `{lang3}_{codec?}_{purpose?}_{region?}_` so the
+    // shortest meaningful run is 4 chars (lang + underscore).
+    let strings = text::extract_ascii_strings(&data, 4);
+
+    // Tracked across all parse_token calls in this run: did any stream
+    // hit an unrecognized token component (skip-unknown path)? If yes
+    // we downgrade confidence to Medium — the labels are still valid
+    // but the corpus surfaced something we don't catalogue.
+    let saw_unknown = AtomicBool::new(false);
+
+    let labels = assign_labels(&strings, &saw_unknown);
+
+    if labels.is_empty() {
+        return None;
+    }
+    let confidence = if saw_unknown.load(Ordering::Relaxed) {
+        Confidence::Medium
+    } else {
+        Confidence::High
+    };
+    Some(ParseResult { labels, confidence })
+}
+
+/// Walk the extracted token strings of the feature section and emit a
+/// `StreamLabel` per editorial token, numbered in STN order. Split out
+/// from `parse` so the section/numbering logic is unit-testable without
+/// a `SectorSource`/`UdfFs`.
+fn assign_labels(strings: &[String], saw_unknown: &AtomicBool) -> Vec<StreamLabel> {
+    // The authoritative per-feature stream list lives in the `FPL_`
+    // (FeaturePLaylist) section, in STN order. `SEG_*` entries are menu
+    // segments (intros, logos, disclaimers, previews) that can also carry
+    // stray stream tokens — e.g. a `SEG_MainFeature` preview segment that
+    // lists only a commentary track. Anchoring on such a segment grabs the
+    // wrong streams and misnumbers them. So when the project ships any
+    // `FPL_` playlist, anchor exclusively on it; only fall back to
+    // `SEG_MainFeature` on discs that have no `FPL_` section at all.
+    let has_fpl = strings.iter().any(|s| s.starts_with("FPL_"));
 
     let mut labels = Vec::new();
     let mut in_feature = false;
     let mut audio_num: u16 = 0;
     let mut sub_num: u16 = 0;
 
-    for s in &strings {
+    for s in strings {
         // Detect feature section start
-        if s.starts_with("FPL_") || s.starts_with("SEG_MainFeature") {
+        let is_start = if has_fpl {
+            s.starts_with("FPL_")
+        } else {
+            s.starts_with("SEG_MainFeature")
+        };
+        if is_start {
             if in_feature {
                 break;
             }
@@ -50,7 +96,25 @@ pub fn parse(reader: &mut dyn SectorReader, udf: &UdfFs) -> Option<Vec<StreamLab
             continue;
         }
 
-        if let Some(label) = parse_token(s) {
+        // Generic audio-slot placeholder. Pixelogic lists each audio stream
+        // in the playlist as either an editorial `{lang}_{codec}_…` token OR
+        // a bare `Audio Stream N` placeholder when no editorial label was
+        // authored. The placeholder carries nothing to label, but it DOES
+        // occupy an STN slot — so it must advance `audio_num`. Otherwise a
+        // later editorial token (e.g. a lone `eng_ACOM_` commentary sitting
+        // at STN slot 4, behind three unlabelled main tracks) collapses onto
+        // slot 1 and its Commentary purpose lands on the main feature track.
+        //
+        // Only audio is corrected here: subtitle (`PG Stream N`) numbering is
+        // left exactly as-is — the corpus snapshots show forced/commentary
+        // subtitle tokens already align with STN without counting the
+        // placeholders, and counting them regresses several discs.
+        if s.starts_with("Audio Stream") {
+            audio_num += 1;
+            continue;
+        }
+
+        if let Some(label) = parse_token_inner(s, Some(saw_unknown)) {
             match label.stream_type {
                 StreamLabelType::Audio => {
                     audio_num += 1;
@@ -70,13 +134,10 @@ pub fn parse(reader: &mut dyn SectorReader, udf: &UdfFs) -> Option<Vec<StreamLab
         }
     }
 
-    if labels.is_empty() {
-        return None;
-    }
-    Some(labels)
+    labels
 }
 
-fn parse_token(s: &str) -> Option<StreamLabel> {
+fn parse_token_inner(s: &str, saw_unknown: Option<&AtomicBool>) -> Option<StreamLabel> {
     let clean = s.trim().trim_start_matches('\t').trim_end_matches('_');
     let parts: Vec<&str> = clean.split('_').collect();
     if parts.len() < 2 {
@@ -127,7 +188,18 @@ fn parse_token(s: &str) -> Option<StreamLabel> {
         } else if part.starts_with("PGStream") {
             is_subtitle = true;
         } else {
-            return None;
+            // Unknown token component — skip this single part rather
+            // than discarding the entire stream record. Pre-refactor
+            // behavior was `return None` here, which silently dropped
+            // any stream containing a single uncatalogued token (e.g.
+            // a new codec ID or framework variant). Better to surface
+            // what we know than discard a whole stream over one part,
+            // but flag the parse as Medium-confidence so callers know
+            // some data was elided.
+            tracing::debug!(part = %part, "pixelogic: unrecognized token component, skipping");
+            if let Some(flag) = saw_unknown {
+                flag.store(true, Ordering::Relaxed);
+            }
         }
     }
 
@@ -153,22 +225,143 @@ fn parse_token(s: &str) -> Option<StreamLabel> {
     })
 }
 
-fn extract_strings(data: &[u8]) -> Vec<String> {
-    let mut strings = Vec::new();
-    let mut current = String::new();
+// extract_strings removed — replaced by super::text::extract_ascii_strings(data, 4).
 
-    for &b in data {
-        if (0x20..0x7f).contains(&b) {
-            current.push(b as char);
-        } else {
-            if current.len() > 3 {
-                strings.push(current.clone());
-            }
-            current.clear();
-        }
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn parse_token_basic_audio() {
+        let l = parse_token_inner("eng_MLP_", None).unwrap();
+        assert_eq!(l.stream_type, StreamLabelType::Audio);
+        assert_eq!(l.language, "eng");
+        assert_eq!(l.codec_hint, "TrueHD");
+        assert_eq!(l.purpose, LabelPurpose::Normal);
     }
-    if current.len() > 3 {
-        strings.push(current);
+
+    #[test]
+    fn parse_token_basic_subtitle_sdh() {
+        let l = parse_token_inner("eng_SDH_", None).unwrap();
+        assert_eq!(l.stream_type, StreamLabelType::Subtitle);
+        assert_eq!(l.language, "eng");
+        assert_eq!(l.qualifier, LabelQualifier::Sdh);
+    }
+
+    #[test]
+    fn parse_token_commentary() {
+        let l = parse_token_inner("eng_MLP_ACOM_", None).unwrap();
+        assert_eq!(l.stream_type, StreamLabelType::Audio);
+        assert_eq!(l.purpose, LabelPurpose::Commentary);
+    }
+
+    #[test]
+    fn parse_token_descriptive() {
+        let l = parse_token_inner("eng_AC3_ADES_", None).unwrap();
+        assert_eq!(l.purpose, LabelPurpose::Descriptive);
+    }
+
+    #[test]
+    fn parse_token_with_region() {
+        let l = parse_token_inner("eng_MLP_US_", None).unwrap();
+        assert_eq!(l.language, "eng");
+        assert_eq!(l.variant, "US");
+    }
+
+    #[test]
+    fn parse_token_unknown_component_does_not_kill_stream() {
+        // Regression: pre-refactor, an unrecognized token part returned
+        // None for the whole stream, silently dropping it. New
+        // behavior: skip the unknown part, surface what we know.
+        let l = parse_token_inner("eng_MLP_FUTUREFLAG_FOR_", None).unwrap();
+        assert_eq!(l.stream_type, StreamLabelType::Audio);
+        assert_eq!(l.language, "eng");
+        assert_eq!(l.codec_hint, "TrueHD");
+        assert_eq!(l.qualifier, LabelQualifier::Forced);
+    }
+
+    #[test]
+    fn parse_token_no_audio_or_subtitle_signal_returns_none() {
+        // A token that has only a language and an unknown part with
+        // no audio/subtitle classifier should still return None —
+        // there's no way to file it as a stream.
+        assert!(parse_token_inner("eng_UNKNOWN_", None).is_none());
+    }
+
+    #[test]
+    fn parse_token_rejects_non_lang_prefix() {
+        assert!(parse_token_inner("XX_MLP_", None).is_none());
+        assert!(parse_token_inner("ENG_MLP_", None).is_none()); // uppercase not accepted as ISO 639-2
+    }
+
+    fn strs(v: &[&str]) -> Vec<String> {
+        v.iter().map(|s| s.to_string()).collect()
+    }
+
+    #[test]
+    fn assign_labels_numbers_commentary_behind_placeholders() {
+        // Observed case: the FPL_MainFeature playlist lists three unlabelled main
+        // audio tracks as `Audio Stream N` placeholders, then a lone
+        // `eng_ACOM_` commentary at STN slot 4. The commentary must land on
+        // audio #4, not collapse onto #1 (which would tag the main feature
+        // track as commentary).
+        let flag = AtomicBool::new(false);
+        let tokens = strs(&[
+            "FPL_MainFeature",
+            "Audio Stream 1",
+            "Audio Stream 2",
+            "Audio Stream 3",
+            "eng_ACOM_",
+        ]);
+        let labels = assign_labels(&tokens, &flag);
+        let audio: Vec<_> = labels
+            .iter()
+            .filter(|l| l.stream_type == StreamLabelType::Audio)
+            .collect();
+        assert_eq!(audio.len(), 1, "only the commentary carries a label");
+        assert_eq!(audio[0].stream_number, 4, "commentary is STN slot 4");
+        assert_eq!(audio[0].purpose, LabelPurpose::Commentary);
+        assert_eq!(audio[0].language, "eng");
+    }
+
+    #[test]
+    fn assign_labels_prefers_fpl_over_seg_mainfeature() {
+        // A `SEG_MainFeature` menu/preview segment carries a stray commentary
+        // token, but the real playlist is `FPL_MainFeature`. When an FPL_
+        // section exists, the SEG_ one must be ignored as an anchor — so we
+        // number from the FPL playlist, putting the commentary at slot 2.
+        let flag = AtomicBool::new(false);
+        let tokens = strs(&[
+            "SEG_MainFeature",
+            "eng_ACOM_", // stray token in the menu segment — must be ignored
+            "FPL_MainFeature",
+            "Audio Stream 1",
+            "eng_ACOM_",
+        ]);
+        let labels = assign_labels(&tokens, &flag);
+        let audio: Vec<_> = labels
+            .iter()
+            .filter(|l| l.stream_type == StreamLabelType::Audio)
+            .collect();
+        assert_eq!(audio.len(), 1);
+        assert_eq!(audio[0].stream_number, 2, "numbered from the FPL playlist");
+        assert_eq!(audio[0].purpose, LabelPurpose::Commentary);
+    }
+
+    #[test]
+    fn assign_labels_falls_back_to_seg_without_fpl() {
+        // Discs with no FPL_ playlist still anchor on SEG_MainFeature.
+        let flag = AtomicBool::new(false);
+        let tokens = strs(&["SEG_MainFeature", "eng_MLP_", "spa_AC3_"]);
+        let labels = assign_labels(&tokens, &flag);
+        let audio: Vec<_> = labels
+            .iter()
+            .filter(|l| l.stream_type == StreamLabelType::Audio)
+            .collect();
+        assert_eq!(audio.len(), 2);
+        assert_eq!(audio[0].stream_number, 1);
+        assert_eq!(audio[0].language, "eng");
+        assert_eq!(audio[1].stream_number, 2);
+        assert_eq!(audio[1].language, "spa");
     }
-    strings
 }

src/labels/text.rs

@@ -0,0 +1,89 @@
+//! Text-extraction helpers used by parsers that scan binary blobs for
+//! embedded label strings.
+//!
+//! Promoted from two near-duplicate implementations:
+//! - `pixelogic::extract_strings` (`bluray_project.bin`, min_len=4)
+//! - `dbp::extract_printable` (`.class` files in jars, min_len=5)
+//!
+//! Single implementation, threshold passed in. Callers that have a
+//! more structured parse path (e.g. `class_reader` for .class) should
+//! prefer that — this helper is for genuinely unstructured input.
+
+/// Walk `data`, emit every maximal run of printable-ASCII bytes
+/// (`0x20..=0x7E`) whose length is at least `min_len`.
+///
+/// Non-printable bytes (including `\t`, `\n`, NUL) terminate the
+/// current run. Output strings are guaranteed valid UTF-8 (they're
+/// pure 7-bit ASCII). Strings shorter than `min_len` are dropped.
+pub fn extract_ascii_strings(data: &[u8], min_len: usize) -> Vec<String> {
+    let mut out = Vec::new();
+    let mut current = String::new();
+    for &b in data {
+        if (0x20..=0x7E).contains(&b) {
+            current.push(b as char);
+        } else if current.len() >= min_len {
+            out.push(std::mem::take(&mut current));
+        } else {
+            current.clear();
+        }
+    }
+    if current.len() >= min_len {
+        out.push(current);
+    }
+    out
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn extracts_simple_runs() {
+        let got = extract_ascii_strings(b"hello\0world\0", 3);
+        assert_eq!(got, vec!["hello", "world"]);
+    }
+
+    #[test]
+    fn applies_minimum_length() {
+        let got = extract_ascii_strings(b"hi\0ok\0longer\0", 5);
+        assert_eq!(got, vec!["longer"]);
+    }
+
+    #[test]
+    fn treats_tab_and_newline_as_separators() {
+        // \t (0x09) and \n (0x0A) are below 0x20, so they break runs.
+        let got = extract_ascii_strings(b"alpha\tbeta\ngamma", 3);
+        assert_eq!(got, vec!["alpha", "beta", "gamma"]);
+    }
+
+    #[test]
+    fn handles_trailing_run_without_terminator() {
+        // Run at the very end of the buffer should still be emitted.
+        let got = extract_ascii_strings(b"prefix\0tail", 3);
+        assert_eq!(got, vec!["prefix", "tail"]);
+    }
+
+    #[test]
+    fn rejects_high_bit_bytes() {
+        // 0x80+ is non-printable per this helper's definition.
+        let mut buf = b"good".to_vec();
+        buf.push(0xC3);
+        buf.push(0xA9);
+        buf.extend_from_slice(b"more");
+        let got = extract_ascii_strings(&buf, 3);
+        assert_eq!(got, vec!["good", "more"]);
+    }
+
+    #[test]
+    fn empty_input_returns_empty() {
+        let got = extract_ascii_strings(&[], 1);
+        assert!(got.is_empty());
+    }
+
+    #[test]
+    fn min_len_zero_emits_singletons() {
+        // Pathological but well-defined.
+        let got = extract_ascii_strings(b"a\0b", 0);
+        assert_eq!(got, vec!["a", "b"]);
+    }
+}

src/labels/vocab.rs

@@ -1,19 +1,39 @@
-//! Shared label vocabulary — values we are 100% confident about.
+//! Shared label vocabulary — canonical mappings used by ≥1 label parser.
 //!
 //! Labels come from BD-J authoring tool files (bluray_project.bin,
-//! playlists.xml, menu_base.prop, etc.) — NOT from BD spec fields.
-//! This is NOT for MPLS/CLPI/STN data. Those follow the BD spec directly.
+//! playlists.xml, menu_base.prop, .class string pools, etc.) — NOT
+//! from BD spec fields. This module is the central, regression-tested
+//! source of truth for:
 //!
-//! Rules:
-//! - Only map values we are 100% certain about (published codec names).
-//! - Unknown codes (csp, eda, cf, etc.) pass through raw from disc.
-//! - The app/CLI handles display text, not the lib.
+//! - Codec brand name aliases (`MLP` → `TrueHD`).
+//! - English / multi-word language name → ISO 639-2 code.
+//! - English text → [`LabelPurpose`] (Commentary / Descriptive / etc.).
+//! - English text → [`LabelQualifier`] (SDH / Forced / Descriptive Service).
+//!
+//! Rules of engagement:
+//!
+//! 1. Only map values we are 100% certain about — published codec
+//!    names, well-known ISO 639-2 mappings, vendor-documented purpose
+//!    keywords.
+//! 2. Unknown codes / unrecognized phrases pass through raw or return
+//!    `None`. We never guess.
+//! 3. Matching is case-insensitive and word-boundary-aware where
+//!    relevant (so "Commenter" doesn't match "commentary"). Anchoring
+//!    on whole tokens is the responsibility of this module — callers
+//!    pass raw text, we handle it.
+//!
+//! This module is NOT for BD spec STN codec IDs; those decode in
+//! `mpls.rs` separately.
+
+use super::{LabelPurpose, LabelQualifier};
+
+// ── Codec aliases ────────────────────────────────────────────────────────────
 
 /// Map a codec identifier found in label data to its display name.
 ///
 /// These are well-known codec identifiers used across multiple BD-J
-/// authoring tools. NOT BD spec STN codec IDs — those are decoded
-/// separately in mpls.rs.
+/// authoring tools. Unknown codes pass through unchanged so callers
+/// can still surface vendor-specific tokens we haven't catalogued.
 pub fn codec(code: &str) -> &str {
     match code {
         "MLP" => "TrueHD",
@@ -25,3 +45,405 @@ pub fn codec(code: &str) -> &str {
         _ => code,
     }
 }
+
+// ── Language: English / multi-word names → ISO 639-2 ─────────────────────────
+
+/// Result of [`lang`] — ISO code + human-readable regional variant.
+///
+/// `code` is ISO 639-2 (always 3 lowercase letters).
+/// `variant` is the regional dialect as a human-readable English word
+/// (`"Brazilian"`, `"Castilian"`, `"Canadian"`, `"Simplified"`, ...)
+/// or `""` when the input names just a bare language without
+/// dialect ("Spanish" → variant=""). The variant matches the
+/// convention pixelogic / ctrm / criterion already use for their
+/// `StreamLabel::variant` field: a short display token the UI can
+/// surface verbatim.
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub struct LangInfo {
+    pub code: &'static str,
+    pub variant: &'static str,
+}
+
+/// Map a free-form language label fragment to an ISO 639-2 code AND
+/// (where applicable) its regional variant.
+///
+/// Handles both bare English names ("English", "Spanish") and the
+/// multi-word vendor variants we've seen in the corpus ("Brazilian
+/// Portuguese", "Castilian Spanish", "Canadian French"). Match is
+/// case-insensitive; longer compound phrases win over their bare
+/// counterparts (so "Brazilian Portuguese" returns
+/// `LangInfo { code: "por", variant: "Brazilian" }`, not consumed by
+/// the bare "Portuguese" entry).
+///
+/// Bare-name matches return `variant: ""`.
+///
+/// Returns `None` for unrecognized input — callers decide whether to
+/// fall back to MPLS spec codes, pass through raw, or drop the stream.
+/// Never guesses.
+///
+/// Why the variant: the prior `lang() -> Option<&str>` shape silently
+/// dropped regional dialect info. "Brazilian Portuguese 5.1" became
+/// `language="por", variant=""` — UI displayed plain "Portuguese"
+/// even though the disc had explicitly labeled this stream Brazilian.
+/// Capturing the variant here parallels how pixelogic and ctrm
+/// populate `StreamLabel::variant` from their own region tables.
+pub fn lang(text: &str) -> Option<LangInfo> {
+    let lower = text.to_lowercase();
+    // Multi-word compounds first — longest-match wins.
+    for (needle, code, variant) in COMPOUND_LANGS {
+        if lower.contains(needle) {
+            return Some(LangInfo { code, variant });
+        }
+    }
+    // Bare names: word-boundary match (avoid "english" inside "englishman"
+    // or any other accidental substring).
+    for (needle, code) in BARE_LANGS {
+        if has_word(&lower, needle) {
+            return Some(LangInfo { code, variant: "" });
+        }
+    }
+    None
+}
+
+const COMPOUND_LANGS: &[(&str, &str, &str)] = &[
+    ("brazilian portuguese", "por", "Brazilian"),
+    ("euro portuguese", "por", "European"),
+    ("european portuguese", "por", "European"),
+    ("castilian spanish", "spa", "Castilian"),
+    ("latin american spanish", "spa", "Latin American"),
+    ("latin spanish", "spa", "Latin American"),
+    ("canadian french", "fra", "Canadian"),
+    ("parisian french", "fra", "Parisian"),
+    ("australian english", "eng", "Australian"),
+    ("austrailian english", "eng", "Australian"), // disc-corpus typo, keep matching
+    ("british english", "eng", "British"),
+    ("simplified chinese", "zho", "Simplified"),
+    ("traditional chinese", "zho", "Traditional"),
+    ("mandarin chinese", "zho", "Mandarin"),
+    ("cantonese chinese", "zho", "Cantonese"),
+];
+
+const BARE_LANGS: &[(&str, &str)] = &[
+    ("english", "eng"),
+    ("spanish", "spa"),
+    ("french", "fra"),
+    ("german", "deu"),
+    ("italian", "ita"),
+    ("japanese", "jpn"),
+    ("chinese", "zho"),
+    ("mandarin", "zho"),
+    ("cantonese", "zho"),
+    ("portuguese", "por"),
+    ("polish", "pol"),
+    ("czech", "ces"),
+    ("hungarian", "hun"),
+    ("dutch", "nld"),
+    ("korean", "kor"),
+    ("arabic", "ara"),
+    ("hindi", "hin"),
+    ("turkish", "tur"),
+    ("thai", "tha"),
+    ("swedish", "swe"),
+    ("norwegian", "nor"),
+    ("danish", "dan"),
+    ("finnish", "fin"),
+    ("hebrew", "heb"),
+    ("russian", "rus"),
+    ("greek", "ell"),
+    ("vietnamese", "vie"),
+    ("indonesian", "ind"),
+    ("malay", "msa"),
+    ("ukrainian", "ukr"),
+    ("romanian", "ron"),
+    ("bulgarian", "bul"),
+    ("croatian", "hrv"),
+    ("serbian", "srp"),
+    ("slovak", "slk"),
+    ("slovenian", "slv"),
+    ("estonian", "est"),
+    ("latvian", "lav"),
+    ("lithuanian", "lit"),
+    ("icelandic", "isl"),
+    ("basque", "eus"),
+    ("catalan", "cat"),
+    ("galician", "glg"),
+];
+
+// ── Purpose ──────────────────────────────────────────────────────────────────
+
+/// Classify a free-form English label string into a [`LabelPurpose`].
+///
+/// Recognized keywords (case-insensitive, word-boundary matched):
+/// - "commentary", "director's commentary" → `Commentary`
+/// - "descriptive", "description", "audio description", "described" → `Descriptive`
+/// - "score", "music only" → `Score`
+/// - "ime" (alternate music for closing themes etc.) → `Ime`
+/// - anything else → `Normal`
+///
+/// Word-boundary matching means "Commentary track" matches but
+/// "Commenter Pro audio" does not.
+pub fn purpose(text: &str) -> LabelPurpose {
+    let lower = text.to_lowercase();
+    // Multi-word compounds first — they're more specific.
+    if lower.contains("audio description") || lower.contains("descriptive service") {
+        return LabelPurpose::Descriptive;
+    }
+    if lower.contains("music only") {
+        return LabelPurpose::Score;
+    }
+    if has_word(&lower, "commentary") {
+        return LabelPurpose::Commentary;
+    }
+    if has_word(&lower, "descriptive")
+        || has_word(&lower, "description")
+        || has_word(&lower, "described")
+    {
+        return LabelPurpose::Descriptive;
+    }
+    if has_word(&lower, "score") {
+        return LabelPurpose::Score;
+    }
+    if has_word(&lower, "ime") {
+        return LabelPurpose::Ime;
+    }
+    LabelPurpose::Normal
+}
+
+// ── Qualifier ────────────────────────────────────────────────────────────────
+
+/// Classify a free-form English label string into a [`LabelQualifier`].
+///
+/// Recognized keywords (case-insensitive, word-boundary matched):
+/// - "sdh", "captions" → `Sdh`
+/// - "forced", "forced narrative" → `Forced`
+/// - "rnib", "descriptive service" → `DescriptiveService`
+/// - anything else → `None`
+///
+/// SDH (Subtitles for the Deaf and Hard of hearing) wins over Forced
+/// when both keywords are present, because an SDH track is its own
+/// stream regardless of whether the player flags it as "forced".
+pub fn qualifier(text: &str) -> LabelQualifier {
+    let lower = text.to_lowercase();
+    if has_word(&lower, "sdh") || has_word(&lower, "captions") {
+        return LabelQualifier::Sdh;
+    }
+    if lower.contains("descriptive service") || has_word(&lower, "rnib") {
+        return LabelQualifier::DescriptiveService;
+    }
+    if has_word(&lower, "forced") {
+        return LabelQualifier::Forced;
+    }
+    LabelQualifier::None
+}
+
+// ── Internal: word-boundary matching ────────────────────────────────────────
+
+/// True if `needle` appears in `haystack` surrounded by non-alphanumeric
+/// boundaries (or string ends). `haystack` is assumed lowercase already.
+///
+/// This is the load-bearing primitive for `lang` / `purpose` /
+/// `qualifier`: bare-token matchers MUST use it, otherwise we match
+/// "english" inside "englishman" and "sdh" inside "lambdash". The
+/// existing parsers used `.contains()` and got lucky on the corpus;
+/// vocab guarantees the boundary.
+fn has_word(haystack: &str, needle: &str) -> bool {
+    if needle.is_empty() {
+        return false;
+    }
+    let bytes = haystack.as_bytes();
+    let nb = needle.as_bytes();
+    let mut i = 0;
+    while i + nb.len() <= bytes.len() {
+        if &bytes[i..i + nb.len()] == nb {
+            let before = if i == 0 { None } else { Some(bytes[i - 1]) };
+            let after = bytes.get(i + nb.len()).copied();
+            let bound = |c: Option<u8>| match c {
+                None => true,
+                Some(b) => !b.is_ascii_alphanumeric(),
+            };
+            if bound(before) && bound(after) {
+                return true;
+            }
+        }
+        i += 1;
+    }
+    false
+}
+
+// ── Tests ────────────────────────────────────────────────────────────────────
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn codec_known_aliases() {
+        assert_eq!(codec("MLP"), "TrueHD");
+        assert_eq!(codec("AC3"), "Dolby Digital");
+        assert_eq!(codec("AC"), "Dolby Digital");
+        assert_eq!(codec("DDL"), "Dolby Digital Plus");
+        assert_eq!(codec("atmos"), "Dolby Atmos");
+    }
+
+    #[test]
+    fn codec_unknown_passes_through() {
+        assert_eq!(codec("FX9"), "FX9");
+        assert_eq!(codec(""), "");
+    }
+
+    fn li(code: &'static str, variant: &'static str) -> LangInfo {
+        LangInfo { code, variant }
+    }
+
+    #[test]
+    fn lang_bare_names_have_empty_variant() {
+        assert_eq!(lang("English"), Some(li("eng", "")));
+        assert_eq!(lang("english"), Some(li("eng", "")));
+        assert_eq!(lang("Spanish 5.1 Dolby Digital"), Some(li("spa", "")));
+        assert_eq!(lang("japanese"), Some(li("jpn", "")));
+        assert_eq!(lang("Italian"), Some(li("ita", "")));
+    }
+
+    #[test]
+    fn lang_compounds_carry_variant() {
+        assert_eq!(
+            lang("Brazilian Portuguese 5.1"),
+            Some(li("por", "Brazilian"))
+        );
+        assert_eq!(lang("Castilian Spanish"), Some(li("spa", "Castilian")));
+        assert_eq!(
+            lang("Canadian French Dolby Digital"),
+            Some(li("fra", "Canadian"))
+        );
+        assert_eq!(
+            lang("Latin American Spanish"),
+            Some(li("spa", "Latin American"))
+        );
+        assert_eq!(lang("Simplified Chinese"), Some(li("zho", "Simplified")));
+        assert_eq!(lang("British English"), Some(li("eng", "British")));
+    }
+
+    #[test]
+    fn lang_compounds_win_over_bare() {
+        // Brazilian Portuguese must map to (por, Brazilian) via the
+        // compound rule, not be intercepted by bare "portuguese"
+        // (which would yield (por, "") and lose the variant).
+        assert_eq!(lang("Brazilian Portuguese").unwrap().variant, "Brazilian");
+        assert_eq!(lang("Canadian French").unwrap().variant, "Canadian");
+    }
+
+    #[test]
+    fn lang_unknown_returns_none() {
+        assert_eq!(lang("Klingon Dolby Atmos"), None);
+        assert_eq!(lang(""), None);
+        assert_eq!(lang("eng"), None); // 3-letter codes are not English names
+    }
+
+    #[test]
+    fn lang_word_boundary_avoids_substring_false_positive() {
+        // No false positive — "engineering" must NOT match "english".
+        assert_eq!(lang("Audio Engineering Demo"), None);
+    }
+
+    #[test]
+    fn purpose_recognizes_commentary() {
+        assert_eq!(purpose("English Commentary"), LabelPurpose::Commentary);
+        assert_eq!(purpose("Director's Commentary"), LabelPurpose::Commentary);
+    }
+
+    #[test]
+    fn purpose_recognizes_descriptive() {
+        assert_eq!(
+            purpose("English Descriptive Audio"),
+            LabelPurpose::Descriptive
+        );
+        assert_eq!(purpose("Audio Description"), LabelPurpose::Descriptive);
+        assert_eq!(purpose("Described Video"), LabelPurpose::Descriptive);
+    }
+
+    #[test]
+    fn purpose_descriptive_service_routes_to_descriptive() {
+        // "Descriptive Service" is qualifier territory but the purpose
+        // implication is Descriptive — vocab::purpose treats it as such.
+        assert_eq!(
+            purpose("English Descriptive Service"),
+            LabelPurpose::Descriptive
+        );
+    }
+
+    #[test]
+    fn purpose_word_boundary_avoids_commenter_false_positive() {
+        // "Commenter Pro audio" does NOT match "commentary" — the
+        // existing dbp/ctrm hand-rolls would have. Vocab is stricter.
+        assert_eq!(purpose("Commenter Pro audio track"), LabelPurpose::Normal);
+    }
+
+    #[test]
+    fn purpose_recognizes_score() {
+        assert_eq!(purpose("Music Only"), LabelPurpose::Score);
+        assert_eq!(purpose("Isolated Score"), LabelPurpose::Score);
+    }
+
+    #[test]
+    fn purpose_unknown_is_normal() {
+        assert_eq!(purpose("English Dolby Atmos"), LabelPurpose::Normal);
+        assert_eq!(purpose(""), LabelPurpose::Normal);
+    }
+
+    #[test]
+    fn qualifier_recognizes_sdh() {
+        assert_eq!(qualifier("English SDH"), LabelQualifier::Sdh);
+        assert_eq!(qualifier("English Captions"), LabelQualifier::Sdh);
+    }
+
+    #[test]
+    fn qualifier_recognizes_forced() {
+        assert_eq!(qualifier("English Forced"), LabelQualifier::Forced);
+        assert_eq!(qualifier("Forced Narrative"), LabelQualifier::Forced);
+    }
+
+    #[test]
+    fn qualifier_recognizes_descriptive_service() {
+        assert_eq!(
+            qualifier("English RNIB"),
+            LabelQualifier::DescriptiveService
+        );
+        assert_eq!(
+            qualifier("English Descriptive Service"),
+            LabelQualifier::DescriptiveService
+        );
+    }
+
+    #[test]
+    fn qualifier_sdh_wins_over_forced_when_both_present() {
+        // SDH track is its own stream regardless of forced flag.
+        assert_eq!(qualifier("English Forced SDH"), LabelQualifier::Sdh);
+    }
+
+    #[test]
+    fn qualifier_unknown_is_none() {
+        assert_eq!(qualifier("English"), LabelQualifier::None);
+        assert_eq!(qualifier(""), LabelQualifier::None);
+    }
+
+    #[test]
+    fn has_word_basic() {
+        assert!(has_word("english forced", "english"));
+        assert!(has_word("english forced", "forced"));
+        assert!(has_word("english", "english"));
+    }
+
+    #[test]
+    fn has_word_rejects_substring() {
+        assert!(!has_word("engineering", "english"));
+        assert!(!has_word("englishman", "english"));
+        assert!(!has_word("aenglish", "english"));
+    }
+
+    #[test]
+    fn has_word_punctuation_boundary() {
+        // "(SDH)" is a valid boundary — parentheses count as non-alphanum.
+        assert!(has_word("english (sdh)", "sdh"));
+        assert!(has_word("commentary,extra,info", "commentary"));
+    }
+}

src/labels/xml.rs

@@ -0,0 +1,452 @@
+//! Tolerant XML scraping helpers — promoted from two near-duplicate
+//! hand-rolls in `paramount.rs` (attribute extraction) and `criterion.rs`
+//! (tag-text extraction).
+//!
+//! These are NOT a full XML parser. They handle the subset of XML the
+//! BD-J authoring tools we've seen actually emit: ASCII tag/attr
+//! names, no entity references inside label strings, optional XML
+//! namespaces. Hardening goals over the prior `find("<tag>")` /
+//! `find(r#"name=""#)` matchers:
+//!
+//! 1. **Case-insensitive** tag and attribute names — vendors casing
+//!    is inconsistent across authoring-tool revisions.
+//! 2. **Namespace-aware** — strip an optional `ns:` prefix so
+//!    `<ns:playlist>` and `<playlist>` both match.
+//! 3. **Whitespace-tolerant** — multiple/tab/newline characters
+//!    around `=` between attribute name and value; whitespace inside
+//!    the opening tag.
+//! 4. **Quote-style tolerant** — both `"value"` and `'value'`.
+//! 5. **Self-closing tag handling** — `<tag />` and `<tag/>` both
+//!    work; [`text`] returns `Some("")` for empty content.
+//!
+//! Out of scope (intentionally simple): XML entity decoding
+//! (`&amp;`, `&lt;`, etc.), CDATA sections, comments, processing
+//! instructions, DTD declarations. None of the BD-J authored disc
+//! data we've observed exercises any of those — labels are plain
+//! ASCII/Latin-1 in attribute values.
+
+/// Extract the value of attribute `name` from one XML element
+/// fragment (e.g. `<playlist name="Feature" id="00222" />`).
+///
+/// Returns the raw attribute text (no entity decoding) or `None` if
+/// the attribute isn't present. Empty string for `name=""` is
+/// represented as `Some("")`.
+pub fn attr(element: &str, name: &str) -> Option<String> {
+    let bytes = element.as_bytes();
+    let name_lower = name.to_ascii_lowercase();
+    let name_bytes = name_lower.as_bytes();
+    let mut i = 0;
+    while i + name_bytes.len() < bytes.len() {
+        // Find the next position where `name=` could start. We need
+        // a word boundary before the name (whitespace or `<` or `:`).
+        if i > 0 && is_name_char(bytes[i - 1]) {
+            i += 1;
+            continue;
+        }
+        if !slice_eq_ignore_case(&bytes[i..i + name_bytes.len()], name_bytes) {
+            i += 1;
+            continue;
+        }
+        let after_name = i + name_bytes.len();
+        // The character immediately after the name must not be a
+        // name-continuation (otherwise we matched a prefix like
+        // `lang_id` when looking for `lang`).
+        if after_name < bytes.len() && is_name_char(bytes[after_name]) {
+            i = after_name;
+            continue;
+        }
+        // Walk past whitespace, then `=`, then more whitespace, then
+        // the opening quote.
+        let mut j = after_name;
+        while j < bytes.len() && is_ws(bytes[j]) {
+            j += 1;
+        }
+        if j >= bytes.len() || bytes[j] != b'=' {
+            i = j.max(i + 1);
+            continue;
+        }
+        j += 1; // past '='
+        while j < bytes.len() && is_ws(bytes[j]) {
+            j += 1;
+        }
+        if j >= bytes.len() {
+            return None;
+        }
+        let quote = bytes[j];
+        if quote != b'"' && quote != b'\'' {
+            // Unquoted attribute values aren't part of well-formed
+            // XML (HTML5 allows them, XML doesn't). Skip.
+            i = j;
+            continue;
+        }
+        let value_start = j + 1;
+        let close = bytes[value_start..].iter().position(|&b| b == quote)?;
+        let value = &element[value_start..value_start + close];
+        return Some(value.to_string());
+    }
+    None
+}
+
+/// Extract the trimmed text content of the first occurrence of
+/// `<tag>...</tag>` in `xml`. Returns `None` if the tag isn't found
+/// or its opening tag is malformed.
+///
+/// Whitespace around the inner text is stripped. Self-closing
+/// `<tag />` yields `Some("")`. Nested same-name tags are NOT
+/// handled — the first close encountered wins (this matches the
+/// prior behavior in criterion.rs).
+pub fn text(xml: &str, tag: &str) -> Option<String> {
+    let (open_end, body_start) = find_open_tag(xml, tag, 0)?;
+    // Self-closing — already consumed in find_open_tag if `/>`.
+    if open_end == body_start {
+        // Means find_open_tag returned the same offset twice for
+        // self-closing form. (Not currently the case in our impl,
+        // but defensive.)
+        return Some(String::new());
+    }
+    // For self-closing tags, body_start is past `/>` and we have no
+    // content. Detect by checking the char at body_start - 1 was `/`.
+    if body_start >= 2 && &xml[body_start - 2..body_start] == "/>" {
+        return Some(String::new());
+    }
+    // Find the matching close tag. Case-insensitive + namespace-aware.
+    let close_start = find_close_tag(xml, tag, body_start)?;
+    Some(xml[body_start..close_start].trim().to_string())
+}
+
+/// Locate the next `<tag>` opening AND its closing `</tag>` in
+/// `xml`, starting at byte offset `from`. Returns `(element_start,
+/// element_end)` — `element_start` is the `<` of the opening tag,
+/// `element_end` is one past the `>` of the closing tag. Useful for
+/// iterating over repeated elements like `<playlist>` blocks in
+/// `paramount`.
+///
+/// Self-closing elements return the same offset for body_end as the
+/// element_end (i.e. `element_end - element_start` includes only the
+/// `<tag .../>` text).
+pub fn find_element(xml: &str, tag: &str, from: usize) -> Option<(usize, usize)> {
+    let bytes = xml.as_bytes();
+    let mut i = from;
+    while i < bytes.len() {
+        if bytes[i] != b'<' {
+            i += 1;
+            continue;
+        }
+        // Try matching tag name at i+1 (after `<`).
+        let after_lt = i + 1;
+        if !matches_tag_name_at(bytes, after_lt, tag) {
+            i += 1;
+            continue;
+        }
+        // Found an open tag at offset i. Walk to find the closing `>`
+        // of the open tag itself.
+        let mut j = after_lt;
+        // Skip past the tag name (and optional namespace prefix).
+        while j < bytes.len() && (is_name_char(bytes[j]) || bytes[j] == b':') {
+            j += 1;
+        }
+        // Walk attributes — track quoting state.
+        let mut self_closing = false;
+        while j < bytes.len() {
+            match bytes[j] {
+                b'>' => {
+                    j += 1;
+                    break;
+                }
+                b'/' if j + 1 < bytes.len() && bytes[j + 1] == b'>' => {
+                    self_closing = true;
+                    j += 2;
+                    break;
+                }
+                b'"' | b'\'' => {
+                    let q = bytes[j];
+                    j += 1;
+                    while j < bytes.len() && bytes[j] != q {
+                        j += 1;
+                    }
+                    if j < bytes.len() {
+                        j += 1;
+                    }
+                }
+                _ => j += 1,
+            }
+        }
+        if self_closing {
+            return Some((i, j));
+        }
+        // Find matching close. Doesn't handle nested same-name; OK
+        // for our authoring-tool subset.
+        let close_start = find_close_tag(xml, tag, j)?;
+        let close_end = find_byte(bytes, b'>', close_start)? + 1;
+        return Some((i, close_end));
+    }
+    None
+}
+
+// ── Internal helpers ───────────────────────────────────────────────────────
+
+/// True if `bytes[start..]` opens a tag named `tag`, allowing an
+/// optional `ns:` namespace prefix. Comparison is case-insensitive.
+/// The character after the tag name must not be a name-continuation
+/// (so `<player>` doesn't match `<play>`).
+fn matches_tag_name_at(bytes: &[u8], start: usize, tag: &str) -> bool {
+    let tag_lower = tag.to_ascii_lowercase();
+    let tag_bytes = tag_lower.as_bytes();
+    // Skip optional `prefix:` (one or more name chars + `:`).
+    let mut name_start = start;
+    let mut scan = start;
+    while scan < bytes.len() && is_name_char(bytes[scan]) {
+        scan += 1;
+    }
+    if scan < bytes.len() && bytes[scan] == b':' {
+        name_start = scan + 1;
+    }
+    if name_start + tag_bytes.len() > bytes.len() {
+        return false;
+    }
+    if !slice_eq_ignore_case(&bytes[name_start..name_start + tag_bytes.len()], tag_bytes) {
+        return false;
+    }
+    // Boundary: char after the tag name must be `>`, `/`, whitespace.
+    let after = name_start + tag_bytes.len();
+    if after >= bytes.len() {
+        return false;
+    }
+    matches!(bytes[after], b'>' | b'/' | b' ' | b'\t' | b'\n' | b'\r')
+}
+
+/// Find the offset of the next `</tag>` (or `</ns:tag>`) in `xml`
+/// starting at `from`. Case-insensitive; returns the offset of the
+/// `<`. None if not found.
+fn find_close_tag(xml: &str, tag: &str, from: usize) -> Option<usize> {
+    let bytes = xml.as_bytes();
+    let mut i = from;
+    while i + 2 < bytes.len() {
+        if bytes[i] == b'<' && bytes[i + 1] == b'/' {
+            // Check tag name (with optional namespace).
+            if matches_tag_name_at(bytes, i + 2, tag) {
+                return Some(i);
+            }
+        }
+        i += 1;
+    }
+    None
+}
+
+/// Find the open tag of `<tag>` in `xml` starting at `from`. Returns
+/// `(after_open_lt, after_open_gt)` — the offsets are: just past
+/// the `<` of the open tag, and just past the `>` of the open tag.
+fn find_open_tag(xml: &str, tag: &str, from: usize) -> Option<(usize, usize)> {
+    let bytes = xml.as_bytes();
+    let (elem_start, _) = find_element(xml, tag, from)?;
+    let after_lt = elem_start + 1;
+    // Find the `>` that ends the open tag (handling quoted attrs).
+    let mut j = after_lt;
+    while j < bytes.len() {
+        match bytes[j] {
+            b'>' => return Some((after_lt, j + 1)),
+            b'/' if j + 1 < bytes.len() && bytes[j + 1] == b'>' => {
+                return Some((after_lt, j + 2));
+            }
+            b'"' | b'\'' => {
+                let q = bytes[j];
+                j += 1;
+                while j < bytes.len() && bytes[j] != q {
+                    j += 1;
+                }
+                if j < bytes.len() {
+                    j += 1;
+                }
+            }
+            _ => j += 1,
+        }
+    }
+    None
+}
+
+fn find_byte(bytes: &[u8], target: u8, from: usize) -> Option<usize> {
+    bytes[from..]
+        .iter()
+        .position(|&b| b == target)
+        .map(|p| p + from)
+}
+
+/// True if `c` can be part of an XML name token (rough). We accept
+/// alphanumerics, `_`, `-`, `.`.
+fn is_name_char(c: u8) -> bool {
+    c.is_ascii_alphanumeric() || c == b'_' || c == b'-' || c == b'.'
+}
+
+fn is_ws(c: u8) -> bool {
+    matches!(c, b' ' | b'\t' | b'\n' | b'\r')
+}
+
+fn slice_eq_ignore_case(a: &[u8], b_lower: &[u8]) -> bool {
+    if a.len() != b_lower.len() {
+        return false;
+    }
+    a.iter()
+        .zip(b_lower.iter())
+        .all(|(&x, &y)| x.to_ascii_lowercase() == y)
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn attr_basic() {
+        assert_eq!(
+            attr(r#"<playlist name="Feature" id="00222" />"#, "name"),
+            Some("Feature".into())
+        );
+        assert_eq!(
+            attr(r#"<playlist name="Feature" id="00222" />"#, "id"),
+            Some("00222".into())
+        );
+    }
+
+    #[test]
+    fn attr_case_insensitive_name() {
+        assert_eq!(
+            attr(r#"<playlist Name="Feature" />"#, "name"),
+            Some("Feature".into())
+        );
+        assert_eq!(
+            attr(r#"<playlist NAME="Feature" />"#, "Name"),
+            Some("Feature".into())
+        );
+    }
+
+    #[test]
+    fn attr_accepts_single_quotes() {
+        assert_eq!(
+            attr(r#"<playlist name='Feature' />"#, "name"),
+            Some("Feature".into())
+        );
+    }
+
+    #[test]
+    fn attr_whitespace_around_equals() {
+        assert_eq!(
+            attr(r#"<playlist name = "Feature" />"#, "name"),
+            Some("Feature".into())
+        );
+        assert_eq!(
+            attr("<playlist name\n=\n\"Feature\" />", "name"),
+            Some("Feature".into())
+        );
+    }
+
+    #[test]
+    fn attr_missing_returns_none() {
+        assert_eq!(attr(r#"<playlist name="X" />"#, "id"), None);
+        assert_eq!(attr("", "name"), None);
+    }
+
+    #[test]
+    fn attr_no_substring_false_positive() {
+        // Looking for "lang" should NOT match "lang_id" or
+        // "language" because of the name-char boundary check.
+        assert_eq!(attr(r#"<x lang_id="fra" language="eng" />"#, "lang"), None);
+    }
+
+    #[test]
+    fn attr_empty_value() {
+        assert_eq!(attr(r#"<x name="" id="1" />"#, "name"), Some("".into()));
+    }
+
+    #[test]
+    fn text_basic() {
+        assert_eq!(text("<x>hello</x>", "x"), Some("hello".into()));
+        assert_eq!(
+            text("<x>  hello world  </x>", "x"),
+            Some("hello world".into())
+        );
+    }
+
+    #[test]
+    fn text_case_insensitive_tag() {
+        assert_eq!(text("<X>foo</X>", "x"), Some("foo".into()));
+        assert_eq!(text("<Foo>bar</foo>", "foo"), Some("bar".into()));
+    }
+
+    #[test]
+    fn text_namespace_prefix() {
+        assert_eq!(text("<ns:tag>value</ns:tag>", "tag"), Some("value".into()));
+        assert_eq!(text("<foo:Bar>v</foo:Bar>", "bar"), Some("v".into()));
+    }
+
+    #[test]
+    fn text_self_closing() {
+        assert_eq!(text("<x/>", "x"), Some("".into()));
+        assert_eq!(text("<x />", "x"), Some("".into()));
+        assert_eq!(text("<x  attr=\"y\" />", "x"), Some("".into()));
+    }
+
+    #[test]
+    fn text_with_attrs() {
+        assert_eq!(
+            text(r#"<x id="1" name="y">hello</x>"#, "x"),
+            Some("hello".into())
+        );
+    }
+
+    #[test]
+    fn text_missing_close_returns_none() {
+        assert_eq!(text("<x>hello", "x"), None);
+    }
+
+    #[test]
+    fn text_skips_inner_tags_naively() {
+        // Limitation noted: nested same-name tags aren't handled.
+        // Different-name nesting works (we just return everything
+        // between the open and close).
+        assert_eq!(
+            text("<x><y>nested</y></x>", "x"),
+            Some("<y>nested</y>".into())
+        );
+    }
+
+    #[test]
+    fn find_element_basic() {
+        let xml = r#"<x />  <y attr="1">body</y>"#;
+        let (s, e) = find_element(xml, "y", 0).unwrap();
+        assert_eq!(&xml[s..e], r#"<y attr="1">body</y>"#);
+    }
+
+    #[test]
+    fn find_element_self_closing() {
+        let xml = r#"<x />"#;
+        let (s, e) = find_element(xml, "x", 0).unwrap();
+        assert_eq!(&xml[s..e], "<x />");
+    }
+
+    #[test]
+    fn find_element_handles_quoted_gt_in_attr() {
+        // A `>` inside a quoted attribute value should not terminate
+        // the open tag prematurely.
+        let xml = r#"<x attr="foo>bar">body</x>"#;
+        let (s, e) = find_element(xml, "x", 0).unwrap();
+        assert_eq!(&xml[s..e], r#"<x attr="foo>bar">body</x>"#);
+    }
+
+    #[test]
+    fn find_element_iteration() {
+        let xml = "<p>a</p><p>b</p><p>c</p>";
+        let mut positions = Vec::new();
+        let mut from = 0;
+        while let Some((s, e)) = find_element(xml, "p", from) {
+            positions.push(&xml[s..e]);
+            from = e;
+        }
+        assert_eq!(positions, vec!["<p>a</p>", "<p>b</p>", "<p>c</p>"]);
+    }
+
+    #[test]
+    fn find_element_with_namespace() {
+        let xml = r#"<root><ns:item id="1" /></root>"#;
+        let (s, e) = find_element(xml, "item", 0).unwrap();
+        assert_eq!(&xml[s..e], r#"<ns:item id="1" />"#);
+    }
+}

src/lib.rs

@@ -77,12 +77,16 @@ pub mod css;
 pub mod decrypt;
 pub mod disc;
 pub mod drive;
+pub mod drm;
 pub mod error;
 pub mod event;
+pub mod halt;
 pub(crate) mod identity;
 pub(crate) mod ifo;
+pub mod io;
 pub mod keydb;
-pub(crate) mod labels;
+pub mod keysource;
+pub mod labels;
 pub(crate) mod mpls;
 pub mod mux;
 pub mod pes;
@@ -95,6 +99,9 @@ pub(crate) mod speed;
 pub(crate) mod udf;
 pub mod verify;
 
+// Re-export verify types at the crate root for ergonomic imports.
+pub use verify::{SectorRange, SectorStatus, VerifyResult, verify_title};
+
 // ─── Drive lifecycle ────────────────────────────────────────────────────────
 //
 // `Drive::open(path)` → `wait_ready()` → `init()` → `Disc::scan()`. `Drive`
@@ -112,6 +119,31 @@ pub use drive::{Drive, DriveStatus, find_drive};
 // codes to localized messages. See `error.rs` for the full taxonomy.
 pub use error::{Error, Result};
 
+// ─── 0.18 primitives ────────────────────────────────────────────────────────
+//
+// One-bit cooperative cancellation token, shared by every long-running loop
+// in libfreemkv (sweep, patch, mux). Replaces the ad-hoc `Arc<AtomicBool>`
+// flags scattered across 0.17 (`DiscStream::set_halt`, autorip's
+// `HALT_FLAGS` registry). Clone it cheaply; pass it by value into each
+// component; poll `is_cancelled()` inside the loop body.
+pub use halt::Halt;
+
+// Generic bounded producer/consumer primitive used by sweep, patch, and
+// mux to overlap reads with writes via a dedicated consumer thread.
+// `Pipeline::spawn(name, depth, sink)` spawns a named consumer; `pipe.send(item)`
+// pushes one item with back-pressure; `pipe.finish()` joins the
+// consumer and surfaces its `close()` output. Callers implement `Sink`
+// to define per-item behaviour and end-of-stream finalisation.
+//
+// `DEFAULT_PIPELINE_DEPTH` (=4) is for callers without specific needs;
+// most should use READ_PIPELINE_DEPTH or WRITE_PIPELINE_DEPTH instead.
+// Patch uses `WRITE_THROUGH_DEPTH` (=1). Returning `Flow::Stop` from
+// `apply` ends the consumer cleanly (still calls `close()`).
+pub use io::pipeline::{
+    DEFAULT_PIPELINE_DEPTH, Flow, Pipeline, READ_PIPELINE_DEPTH, Sink, WRITE_PIPELINE_DEPTH,
+    WRITE_THROUGH_DEPTH,
+};
+
 // ─── Drive events (low-level callbacks) ─────────────────────────────────────
 pub use event::{Event, EventKind};
 pub use identity::DriveId;
@@ -124,7 +156,7 @@ pub use profile::DriveProfile;
 // don't touch `DecryptKeys` directly — `DiscStream::new(reader, title, keys, …)`
 // accepts whatever `Disc::decrypt_keys()` returned. `decrypt_sectors()` is
 // for callers that operate on raw sector buffers (e.g. ISO patching).
-pub use decrypt::{DecryptKeys, decrypt_sectors};
+pub use decrypt::{DecryptKeys, decrypt_sectors, decrypt_threads, set_decrypt_threads};
 
 // ─── Disc structure ─────────────────────────────────────────────────────────
 //
@@ -133,19 +165,24 @@ pub use decrypt::{DecryptKeys, decrypt_sectors};
 // for displaying disc name + format quickly while a full scan runs in the
 // background. The codec / channel / resolution enums are the canonical
 // structured representation; never compare against display strings.
+// Note: `disc::Stream` here is the codec enum (audio / video / sub kind)
+// — not the `pes::Stream` trait re-exported below as `PesStream`. Two
+// different concepts, the same short name; the trait gets the `Pes`
+// prefix at the crate root to keep both addressable.
 pub use disc::{
     AacsState, AudioChannels, AudioStream, Clip, Codec, ColorSpace, ContentFormat, DamageSeverity,
-    Disc, DiscFormat, DiscId, DiscTitle, Extent, FrameRate, HdrFormat, KeySource, LabelPurpose,
-    LabelQualifier, Resolution, SampleRate, ScanOptions, Stream, SubtitleStream, VideoStream,
-    classify_damage,
+    Disc, DiscFormat, DiscId, DiscTitle, DriveCredentials, Extent, FrameRate, HdrFormat, Key,
+    KeyOrigin, LabelPurpose, LabelQualifier, PatchOptions, PatchOutcome, Resolution, SampleRate,
+    ScanOptions, Stream, SubtitleStream, SweepOptions, VideoStream, classify_damage,
 };
+pub use keysource::{DiscInputs, KeySource};
 
 // ─── Streams ────────────────────────────────────────────────────────────────
 //
 // All stream types implement `pes::Stream` — read PES frames from a source,
 // write PES frames to a sink. Pick the right type at construction:
 //
-// - `DiscStream` — physical drive or ISO (any `SectorReader`). Always read.
+// - `DiscStream` — physical drive or ISO (any `SectorSource`). Read-only.
 // - `MkvStream`  — Matroska container. Read on `open()`, write on `create()`.
 // - `M2tsStream` — Blu-ray Transport Stream. Read on `open()`, write on `create()`.
 // - `NetworkStream` — TCP. Read on `listen()`, write on `connect()`.
@@ -155,6 +192,12 @@ pub use disc::{
 // Most consumers use the URL resolvers (`input()` / `output()`) which pick
 // the right type from a scheme:// URL. Direct construction is for callers
 // that need to wire custom readers (e.g. autorip's drive-session reuse).
+// The trait is re-exported as `PesStream` here to disambiguate from
+// `disc::Stream` (the codec-kind enum re-exported above), which would
+// otherwise collide at the crate root.
+pub use pes::PesFrame;
+pub use pes::Stream as PesStream;
+
 pub use mux::DiscStream;
 pub use mux::M2tsStream;
 pub use mux::MkvStream;
@@ -166,10 +209,16 @@ pub use mux::{InputOptions, StreamUrl, input, output, parse_url};
 // ─── Lower-level surfaces ───────────────────────────────────────────────────
 //
 // `ScsiTransport` is the platform-abstraction trait Drive uses; expose for
-// out-of-tree platform backends. `SectorReader` lets callers feed any byte
-// source (test harness, network image, SMB share) into the disc scan
-// pipeline; `FileSectorReader` is the standard ISO-on-disk implementation.
+// out-of-tree platform backends. `SectorSource` / `SectorSink` are the
+// direction-typed read/write traits; `FileSectorSource` and `FileSectorSink`
+// are the ISO-on-disk implementations. [`DecryptingSectorSource`] is the
+// single decrypt-on-read decorator (AACS / CSS / none) — wrap any
+// `SectorSource` to get plaintext sectors out.
+pub use mux::build_iso_pipeline;
 pub use scsi::{DriveInfo, ScsiSense, ScsiTransport, drive_has_disc, list_drives};
-pub use sector::{FileSectorReader, SectorReader};
+pub use sector::{
+    DecryptingSectorSource, FileSectorSink, FileSectorSource, PrefetchedSectorSource, SectorSink,
+    SectorSource,
+};
 pub use speed::DriveSpeed;
 pub use udf::{UdfFs, read_filesystem};

src/mpls.rs

@@ -301,9 +301,21 @@ fn parse_stream_entry(item: &[u8], pos: usize, stream_type: u8) -> Option<(Strea
         return None;
     }
 
-    // PID from stream entry (type 0x01 = PlayItem stream: PID at bytes 2-3)
-    let pid = if item[pos + 1] == 0x01 && pos + 4 <= item.len() {
-        u16::from_be_bytes([item[pos + 2], item[pos + 3]])
+    // PID location depends on the stream-entry type (BD spec stream_entry()):
+    //   type 1 (stream in the PlayItem's Clip):          PID at +2
+    //   type 2 (stream in a SubPath SubClip):            +subpath_id(1)+subclip_id(1) → PID at +4
+    //   type 3 / 4 (SubPath clip; type 4 = Dolby Vision  +subpath_id(1)              → PID at +3
+    //              enhancement layer, e.g. PID 0x1015):
+    // Previously only type 1 was handled, so the DV EL (type 4) and any
+    // sub-path stream fell through to PID 0 and were dropped by the mux.
+    let pid_off = match item[pos + 1] {
+        0x01 => 2,
+        0x02 => 4,
+        0x03 | 0x04 => 3,
+        _ => 0,
+    };
+    let pid = if pid_off != 0 && pos + pid_off + 2 <= item.len() {
+        u16::from_be_bytes([item[pos + pid_off], item[pos + pid_off + 1]])
     } else {
         0
     };

src/mux/codec/ac3.rs

@@ -6,6 +6,14 @@
 
 use super::{CodecParser, Frame, PesPacket, pts_to_ns};
 
+/// Hard cap on the carry-over buffer. An AC-3/E-AC-3 frame is at most 8192
+/// bytes (the `frame_size > 8192` reject below), so a single straddling frame
+/// plus a little slack never needs more than this. If the buffer grows past
+/// the cap without yielding a frame (pathological / never-syncing input) we
+/// drop it and resync rather than accumulate one PES worth of data per call
+/// for the whole title.
+const MAX_AC3_BUF: usize = 64 * 1024;
+
 pub struct Ac3Parser {
     /// Leftover bytes from previous PES (incomplete frame at end).
     buf: Vec<u8>,
@@ -76,23 +84,43 @@ impl CodecParser for Ac3Parser {
                 pts_ns,
                 keyframe: true,
                 data: data[start..start + frame_size].to_vec(),
+                duration_ns: None,
             });
             pos = start + frame_size;
         }
 
-        // Keep unconsumed data for next call
-        // `pos` points to the start of unconsumed data (either a partial sync or leftover)
+        // Keep unconsumed data for the next call. `pos` is the start of the
+        // unconsumed region: either a partial frame that straddles this PES
+        // boundary — which, by construction, begins at a syncword (every byte
+        // before `pos` was emitted as a frame or skipped as pre-sync junk) — or
+        // trailing bytes too short to size/complete a frame. Carry from `pos`,
+        // NOT from the next syncword: discarding bytes between `pos` and the
+        // next sync would drop the partial frame we are deliberately keeping
+        // across the boundary.
         let keep_from = if pos < data.len() {
-            // Find the last sync word position in the unconsumed region
-            find_ac3_sync(&data[pos..])
-                .map(|o| pos + o)
-                .unwrap_or(data.len())
+            // A syncword at/after `pos` marks the carry-over start (anything
+            // before it is junk with no sync). With no full sync, retain the
+            // whole tail — including a lone trailing 0x0B that may be the first
+            // half of a syncword split across the PES boundary.
+            match find_ac3_sync(&data[pos..]) {
+                Some(o) => pos + o,
+                None if data.last() == Some(&0x0B) => data.len() - 1,
+                None => data.len(),
+            }
         } else {
             data.len()
         };
 
         if keep_from < data.len() {
-            self.buf = data[keep_from..].to_vec();
+            let tail = &data[keep_from..];
+            if tail.len() > MAX_AC3_BUF {
+                // No frame could be parsed out of a buffer this large — this is
+                // not valid AC-3 here. Drop it and resync on the next PES rather
+                // than grow without bound on pathological input.
+                self.buf.clear();
+            } else {
+                self.buf = tail.to_vec();
+            }
         } else {
             self.buf.clear();
         }
@@ -275,6 +303,91 @@ mod tests {
         assert_eq!(frames[0].data.len(), 160);
     }
 
+    #[test]
+    fn sync_word_split_across_pes_is_preserved() {
+        // A frame whose 0x0B77 syncword straddles the PES boundary (0x0B at the
+        // tail of PES 1, 0x77 at the head of PES 2) must still be emitted whole.
+        // Previously the lone trailing 0x0B was dropped and the frame lost.
+        let mut parser = Ac3Parser::new();
+        let frame_data = make_ac3_frame(0, 2); // 160 bytes, starts with 0x0B 0x77
+
+        // PES 1: a complete frame, then a single 0x0B (first half of next sync).
+        let mut pes1_data = frame_data.clone();
+        pes1_data.push(0x0B);
+        let pes1 = PesPacket {
+            pid: 0,
+            pts: Some(90000),
+            dts: None,
+            data: pes1_data,
+        };
+        let frames1 = parser.parse(&pes1);
+        assert_eq!(frames1.len(), 1, "first complete frame emitted");
+
+        // PES 2: 0x77 (second half of sync) + rest of the second frame.
+        let mut pes2_data = vec![0x77];
+        pes2_data.extend_from_slice(&frame_data[2..]);
+        let pes2 = PesPacket {
+            pid: 0,
+            pts: Some(93000),
+            dts: None,
+            data: pes2_data,
+        };
+        let frames2 = parser.parse(&pes2);
+        assert_eq!(frames2.len(), 1, "split-sync frame must be recovered");
+        assert_eq!(frames2[0].data.len(), 160);
+    }
+
+    #[test]
+    fn buffer_stays_bounded_across_many_garbage_pes() {
+        // Finding 14: the carry-over buffer must never grow without bound. Feed
+        // many large PES packets that contain no usable frame and assert the
+        // retained buffer stays tiny — carry-from-`pos` drops all pre-sync junk,
+        // and a never-completing frame is bounded by the 8192-byte frame cap and
+        // the MAX_AC3_BUF resync guard.
+        let mut parser = Ac3Parser::new();
+        for i in 0..256 {
+            // Vary the trailing byte so we also exercise the lone-0x0B retain.
+            let mut data = vec![0x55u8; 8192];
+            if i % 3 == 0 {
+                *data.last_mut().unwrap() = 0x0B;
+            }
+            let pes = PesPacket {
+                pid: 0,
+                pts: None,
+                dts: None,
+                data,
+            };
+            let frames = parser.parse(&pes);
+            assert!(frames.is_empty());
+            assert!(
+                parser.buf.len() <= MAX_AC3_BUF,
+                "buffer grew to {} (cap {})",
+                parser.buf.len(),
+                MAX_AC3_BUF
+            );
+        }
+        // After all that garbage the retained tail is at most a single partial
+        // syncword byte — never an accumulation of whole PES packets.
+        assert!(parser.buf.len() <= 1, "retained {} bytes", parser.buf.len());
+    }
+
+    #[test]
+    fn split_sync_below_cap_is_still_retained() {
+        // The cap must not break the normal split-sync straddle: a short tail
+        // ending in 0x0B (well under the cap) is retained so the next PES can
+        // complete the syncword.
+        let mut parser = Ac3Parser::new();
+        let data = vec![0x00, 0x00, 0x0B];
+        let pes = PesPacket {
+            pid: 0,
+            pts: None,
+            dts: None,
+            data,
+        };
+        assert!(parser.parse(&pes).is_empty());
+        assert_eq!(parser.buf, vec![0x0B], "lone trailing 0x0B retained");
+    }
+
     #[test]
     fn ac3_frame_size_table() {
         // fscod=0 (48kHz), frmsizecod=0: 64 words = 128 bytes

src/mux/codec/dts.rs

@@ -8,10 +8,20 @@
 use super::{CodecParser, Frame, PesPacket, pts_to_ns};
 
 const DTS_CORE_SYNC: [u8; 4] = [0x7F, 0xFE, 0x80, 0x01];
+/// DTS-HD extension substream syncword. The parser delimits an access unit by
+/// the next CORE sync (so every extension between two cores is captured), and
+/// never needs to locate or size the extension itself — so this is referenced
+/// only by the tests that synthesize extension substreams.
+#[cfg(test)]
 const DTS_HD_EXT_SYNC: [u8; 4] = [0x64, 0x58, 0x20, 0x25];
 
 pub struct DtsParser {
     buf: Vec<u8>,
+    /// PTS of the access unit currently being assembled in `buf` (the unit
+    /// starting at the first buffered core sync). Captured when that core
+    /// frame's PES first arrived; the trailing extension-substream PES
+    /// packets carry their own (later) PTS which must NOT override it.
+    pending_pts: i64,
 }
 
 impl Default for DtsParser {
@@ -24,10 +34,29 @@ impl DtsParser {
     pub fn new() -> Self {
         Self {
             buf: Vec::with_capacity(32768),
+            pending_pts: 0,
         }
     }
 }
 
+/// Hard cap on a buffered access unit (core + all its extension substreams).
+/// A DTS-HD MA frame is at most a few tens of KB; if the buffer grows past
+/// this without a clean boundary we resync rather than stall or balloon.
+const MAX_AU_BYTES: usize = 65536;
+
+/// Minimum plausible DTS core frame size. The core header alone is ~10-14
+/// bytes; a decoded `core_size` below this means we matched a false/corrupt
+/// core sync (the 14-bit `fsize` field decoded to a tiny value) rather than a
+/// real frame, so we resync instead of emitting a junk access unit.
+const MIN_CORE_FRAME_BYTES: usize = 10;
+
+/// Sentinel for "no valid PTS base captured yet". Real PTS-in-ns values are
+/// non-negative (derived from the unsigned 90 kHz PES timestamp), so a negative
+/// value can never collide with a genuine timestamp. Used to mark the PTS base
+/// invalid after a forced flush so the next PES sets it regardless of buffer
+/// state.
+const PTS_UNSET: i64 = -1;
+
 impl CodecParser for DtsParser {
     fn parse(&mut self, pes: &PesPacket) -> Vec<Frame> {
         if pes.data.is_empty() {
@@ -35,79 +64,162 @@ impl CodecParser for DtsParser {
         }
         let pts_ns = pes.pts.map(pts_to_ns).unwrap_or(0);
 
+        // On Blu-ray, a DTS-HD MA/HRA access unit is a DTS core frame
+        // (sync 0x7FFE8001) followed by one or more DTS extension substreams
+        // (sync 0x64582025). The m2ts demuxer hands those out as SEPARATE PES
+        // packets on the same PID — the core in one PES, then the extension
+        // substreams in following PES packets (with their own, later PTS). The
+        // lossless audio lives entirely in the extension substreams, so an
+        // access unit is only complete once all of its trailing extensions
+        // have been buffered. We assemble across PES boundaries here: an access
+        // unit runs from its core sync up to (but not including) the NEXT core
+        // sync. Emitting on the core boundary keeps the core + every following
+        // extension substream together (the lossless data), instead of the
+        // old per-PES emit that dropped the extension PES packets and
+        // downgraded the track to lossy DTS core (the Dunkirk / Fight Club
+        // bug). The PTS is the core frame's PTS, captured when the unit began.
+        // Capture the access unit's PTS base on a fresh buffer, or whenever a
+        // prior forced (safety-valve) flush left it invalidated — in the
+        // forced case the bytes still in `buf` are not a real core frame, so
+        // the first PES to arrive after the flush carries the correct base.
+        if self.buf.is_empty() || self.pending_pts == PTS_UNSET {
+            self.pending_pts = pts_ns;
+        }
         self.buf.extend_from_slice(&pes.data);
 
-        let data = &self.buf;
         let mut frames = Vec::new();
-        let mut pos = 0;
 
-        while pos < data.len() {
-            // Find DTS core sync
-            let start = match find_sync(&data[pos..], &DTS_CORE_SYNC) {
-                Some(offset) => pos + offset,
-                None => break,
+        loop {
+            // Resync to the first core sync; drop any leading junk.
+            let Some(start) = find_sync(&self.buf, &DTS_CORE_SYNC) else {
+                // No core sync at all yet — keep at most a 3-byte tail so a
+                // sync split across PES packets can still be found next time.
+                if self.buf.len() > 3 {
+                    let tail = self.buf.len() - 3;
+                    self.buf.drain(..tail);
+                }
+                break;
             };
-
-            // Need at least 10 bytes for core header to get frame size
-            if start + 10 > data.len() {
-                break;
-            }
-
-            let core_size = dts_core_frame_size(&data[start..]);
-            if core_size == 0 || core_size > 32768 {
-                pos = start + 4;
-                continue;
-            }
-
-            if start + core_size > data.len() {
-                // Incomplete core frame
-                break;
-            }
-
-            // Check for DTS-HD extension after core
-            let mut total_size = core_size;
-            if start + core_size + 4 <= data.len() {
-                if let Some(0) = find_sync(
-                    &data[start + core_size..start + core_size + 4],
-                    &DTS_HD_EXT_SYNC,
-                ) {
-                    let ext = &data[start + core_size..];
-                    if ext.len() >= 9 {
-                        let ext_size = dts_hd_ext_frame_size(ext);
-                        if start + core_size + ext_size <= data.len() {
-                            total_size = core_size + ext_size;
-                        }
-                        // If ext incomplete, just emit core
-                    }
+            if start > 0 {
+                self.buf.drain(..start);
+                if find_sync(&self.buf, &DTS_CORE_SYNC) != Some(0) {
+                    // Shouldn't happen, but never loop forever.
+                    break;
                 }
             }
 
+            // Need the core header to size the core frame.
+            if self.buf.len() < 10 {
+                break;
+            }
+            let core_size = dts_core_frame_size(&self.buf);
+            // `dts_core_frame_size` returns a 14-bit `fsize + 1`, so it is
+            // always in [1, 16384]; the bare `== 0` / `> MAX_AU_BYTES` checks
+            // can never fire. A real DTS core header is at least ~10-14 bytes,
+            // so any decoded size below that came from a false/corrupt sync.
+            // Reject it (drain the 4 syncword bytes and resync) instead of
+            // letting a tiny bogus size close the current access unit at a junk
+            // boundary and drop the trailing extension substreams. The
+            // `> MAX_AU_BYTES` upper bound is kept as a harmless guard.
+            if !(MIN_CORE_FRAME_BYTES..=MAX_AU_BYTES).contains(&core_size) {
+                // Bogus core sync — skip past it and resync.
+                self.buf.drain(..4);
+                continue;
+            }
+            if self.buf.len() < core_size {
+                break; // core frame not fully buffered yet — wait
+            }
+
+            // The access unit ends at the next *valid* core sync. The search
+            // begins after this core's syncword so we don't re-match it.
+            // Anything between the core and that next sync is this unit's
+            // extension substream(s) — which can themselves contain byte
+            // sequences matching the core syncword, so a raw `find_sync` match
+            // is not enough: a candidate is only a real boundary if its decoded
+            // core size is plausible. `next_core_boundary` skips bogus matches.
+            //
+            // `forced` distinguishes a real next-core boundary from a forced
+            // safety-valve flush. On a forced flush the access unit was NOT
+            // closed by a new core sync, so the bytes following it are not a
+            // fresh core frame and the current PES's PTS (which on a forced
+            // flush is an extension-substream PES, carrying its own later
+            // timestamp) must NOT become the next unit's PTS base.
+            let mut forced = false;
+            let au_end = match next_core_boundary(&self.buf, core_size) {
+                NextCore::Found(end) => end,
+                NextCore::NeedMore => break, // candidate sync needs more header
+                NextCore::None => {
+                    // No next core sync buffered yet. The trailing extension
+                    // substream PES packets may still be arriving, so WAIT for
+                    // them rather than emit a core-only (lossy) frame — unless
+                    // the buffer has grown unreasonably large, in which case
+                    // emit what we have to guarantee forward progress.
+                    if self.buf.len() <= MAX_AU_BYTES {
+                        break;
+                    }
+                    forced = true;
+                    self.buf.len()
+                }
+            };
+
+            let au: Vec<u8> = self.buf[..au_end].to_vec();
             frames.push(Frame {
-                pts_ns,
+                pts_ns: self.pending_pts,
                 keyframe: true,
-                data: data[start..start + total_size].to_vec(),
+                data: au,
+                duration_ns: None,
             });
-            pos = start + total_size;
-        }
-
-        // Keep unconsumed data
-        let keep_from = if pos < data.len() {
-            find_sync(&data[pos..], &DTS_CORE_SYNC)
-                .map(|o| pos + o)
-                .unwrap_or(data.len())
-        } else {
-            data.len()
-        };
-
-        if keep_from < data.len() {
-            self.buf = data[keep_from..].to_vec();
-        } else {
-            self.buf.clear();
+            self.buf.drain(..au_end);
+            if forced {
+                // Safety-valve flush: the next access unit's real core PES has
+                // not arrived. Invalidate the PTS so the next PES sets it
+                // regardless of buffer state, rather than inheriting this
+                // (non-core) PES's timestamp.
+                self.pending_pts = PTS_UNSET;
+            } else {
+                // Real boundary: the next access unit (now at buf start) begins
+                // at a core sync that arrived inside this PES, so this PES's PTS
+                // is the correct base for it.
+                self.pending_pts = pts_ns;
+            }
         }
 
         frames
     }
 
+    fn flush(&mut self) -> Vec<Frame> {
+        // End of stream: emit the final access unit still buffered (the last
+        // core + its extension substreams, which had no following core sync to
+        // close it during streaming). Require a complete core frame; drop a
+        // bare partial sync tail.
+        if find_sync(&self.buf, &DTS_CORE_SYNC) != Some(0) || self.buf.len() < 10 {
+            self.buf.clear();
+            return Vec::new();
+        }
+        let core_size = dts_core_frame_size(&self.buf);
+        // `dts_core_frame_size` returns a 14-bit `fsize + 1` (never 0), so the
+        // old `== 0` check was dead; reject a sub-minimum core like `parse()`.
+        if core_size < MIN_CORE_FRAME_BYTES || self.buf.len() < core_size {
+            self.buf.clear();
+            return Vec::new();
+        }
+        let au = std::mem::take(&mut self.buf);
+        // A non-empty buffer here means a PES arrived after any prior forced
+        // flush (which fully drains `buf`), so `pending_pts` was reset to that
+        // PES's real PTS. Clamp the sentinel to 0 defensively all the same.
+        let pts_ns = if self.pending_pts == PTS_UNSET {
+            0
+        } else {
+            self.pending_pts
+        };
+        vec![Frame {
+            pts_ns,
+            keyframe: true,
+            data: au,
+            duration_ns: None,
+        }]
+    }
+
     fn codec_private(&self) -> Option<Vec<u8>> {
         None
     }
@@ -120,6 +232,40 @@ fn find_sync(data: &[u8], pattern: &[u8; 4]) -> Option<usize> {
     (0..=data.len() - 4).find(|&i| data[i..i + 4] == *pattern)
 }
 
+/// Result of scanning for the next valid core sync that closes an access unit.
+enum NextCore {
+    /// A valid next core sync was found; the access unit ends at this offset.
+    Found(usize),
+    /// A candidate core sync was found but its header isn't fully buffered yet,
+    /// so its validity can't be decided — wait for more data.
+    NeedMore,
+    /// No (further) core sync found in the buffer.
+    None,
+}
+
+/// Find the next *valid* core sync after the current core frame, to delimit the
+/// access unit. Extension-substream payload can contain byte sequences that
+/// match the core syncword, so each candidate is validated by decoding its
+/// core size: a match whose decoded size is implausible (< MIN_CORE_FRAME_BYTES
+/// or > MAX_AU_BYTES) is a false sync and is skipped, continuing the search.
+fn next_core_boundary(buf: &[u8], core_size: usize) -> NextCore {
+    let mut from = core_size;
+    while let Some(rel) = find_sync(&buf[from..], &DTS_CORE_SYNC) {
+        let pos = from + rel;
+        // Need the candidate's core header to judge it.
+        if buf.len() - pos < 10 {
+            return NextCore::NeedMore;
+        }
+        let sz = dts_core_frame_size(&buf[pos..]);
+        if (MIN_CORE_FRAME_BYTES..=MAX_AU_BYTES).contains(&sz) {
+            return NextCore::Found(pos);
+        }
+        // False sync inside extension payload — skip it and keep searching.
+        from = pos + 4;
+    }
+    NextCore::None
+}
+
 /// DTS core frame size from header bits.
 /// fsize is at bits 46-59 (14 bits) of the header: bytes 5-7.
 fn dts_core_frame_size(data: &[u8]) -> usize {
@@ -133,20 +279,6 @@ fn dts_core_frame_size(data: &[u8]) -> usize {
     fsize + 1
 }
 
-/// DTS-HD extension frame size from extension header.
-pub fn dts_hd_ext_frame_size(ext: &[u8]) -> usize {
-    if ext.len() < 9 {
-        return 0;
-    }
-    let raw =
-        ((ext[6] as usize & 0x1F) << 11) | ((ext[7] as usize) << 3) | ((ext[8] as usize) >> 5);
-    raw + 1
-}
-
-pub fn find_dts_hd_ext_sync(data: &[u8]) -> Option<usize> {
-    find_sync(data, &DTS_HD_EXT_SYNC)
-}
-
 #[cfg(test)]
 mod tests {
     use super::*;
@@ -180,12 +312,16 @@ mod tests {
 
     #[test]
     fn parse_single_frame() {
+        // A single core frame with no following core sync is the LAST access
+        // unit — held during streaming (can't know an extension won't follow),
+        // then drained on flush() at EOF.
         let mut parser = DtsParser::new();
         let frame = make_dts_core(512);
         let pes = make_pes(frame, Some(90000));
-        let frames = parser.parse(&pes);
-        assert_eq!(frames.len(), 1);
-        assert_eq!(frames[0].data.len(), 512);
+        assert!(parser.parse(&pes).is_empty());
+        let tail = parser.flush();
+        assert_eq!(tail.len(), 1);
+        assert_eq!(tail[0].data.len(), 512);
     }
 
     #[test]
@@ -198,9 +334,206 @@ mod tests {
         assert!(parser.parse(&pes1).is_empty());
 
         let pes2 = make_pes(frame[mid..].to_vec(), Some(93000));
-        let frames = parser.parse(&pes2);
-        assert_eq!(frames.len(), 1);
-        assert_eq!(frames[0].data.len(), 512);
+        assert!(parser.parse(&pes2).is_empty());
+        let tail = parser.flush();
+        assert_eq!(tail.len(), 1);
+        assert_eq!(tail[0].data.len(), 512);
+    }
+
+    #[test]
+    fn two_cores_back_to_back_emit_first_on_boundary() {
+        // The first complete unit is emitted as soon as the next core sync is
+        // seen; the second is held until flush.
+        let mut parser = DtsParser::new();
+        let mut stream = make_dts_core(512);
+        stream.extend_from_slice(&make_dts_core(640));
+        let f = parser.parse(&make_pes(stream, Some(90000)));
+        assert_eq!(f.len(), 1);
+        assert_eq!(f[0].data.len(), 512);
+        let tail = parser.flush();
+        assert_eq!(tail.len(), 1);
+        assert_eq!(tail[0].data.len(), 640);
+    }
+
+    /// Build a minimal DTS-HD extension substream of `size` bytes (just the
+    /// sync + zero-padding). The parser delimits extensions by the next CORE
+    /// sync, not by the extension's own size header, so a valid header isn't
+    /// required — only that the bytes carry no spurious core sync.
+    fn make_dts_ext(size: usize) -> Vec<u8> {
+        let mut e = vec![0u8; size];
+        e[0..4].copy_from_slice(&DTS_HD_EXT_SYNC);
+        e
+    }
+
+    #[test]
+    fn keeps_dts_hd_extension_in_separate_pes_packets() {
+        // The real Blu-ray layout (ground-truthed on Dunkirk): the DTS core
+        // arrives in one PES, then its DTS-HD MA extension substreams arrive
+        // in SEPARATE following PES packets on the same PID. The parser must
+        // stitch core + all trailing extensions into one access unit — not
+        // emit a core-only (lossy) frame and drop the extension PES packets
+        // (the Dunkirk / Fight Club lossy-core bug).
+        let mut parser = DtsParser::new();
+
+        // Frame 1: core (512) + two extension substreams (256 + 200).
+        assert!(
+            parser
+                .parse(&make_pes(make_dts_core(512), Some(90000)))
+                .is_empty(),
+            "core alone: must wait for any following extension"
+        );
+        assert!(
+            parser
+                .parse(&make_pes(make_dts_ext(256), Some(91000)))
+                .is_empty(),
+            "first extension PES: still waiting for the unit to close"
+        );
+        assert!(
+            parser
+                .parse(&make_pes(make_dts_ext(200), Some(91500)))
+                .is_empty(),
+            "second extension PES: unit still not closed (no next core yet)"
+        );
+
+        // Frame 2's core PES arrives — that closes frame 1. The emitted unit
+        // must be core + BOTH extensions (lossless preserved), and keep the
+        // core's PTS, not the extension PES timestamps.
+        let f = parser.parse(&make_pes(make_dts_core(512), Some(93000)));
+        assert_eq!(f.len(), 1);
+        assert_eq!(
+            f[0].data.len(),
+            512 + 256 + 200,
+            "frame must include core + every extension substream"
+        );
+
+        // EOF drains frame 2.
+        let tail = parser.flush();
+        assert_eq!(tail.len(), 1);
+        assert_eq!(tail[0].data.len(), 512);
+    }
+
+    #[test]
+    fn extension_split_across_pes_is_preserved() {
+        // An extension substream straddling a PES boundary must still be fully
+        // attached to its core.
+        let mut parser = DtsParser::new();
+        let ext = make_dts_ext(300);
+        assert!(
+            parser
+                .parse(&make_pes(make_dts_core(512), Some(90000)))
+                .is_empty()
+        );
+        assert!(
+            parser
+                .parse(&make_pes(ext[..150].to_vec(), Some(91000)))
+                .is_empty()
+        );
+        assert!(
+            parser
+                .parse(&make_pes(ext[150..].to_vec(), Some(91000)))
+                .is_empty()
+        );
+        let tail = parser.flush();
+        assert_eq!(tail.len(), 1);
+        assert_eq!(tail[0].data.len(), 512 + 300);
+    }
+
+    /// Build 4 bytes that look like a DTS core sync but whose `fsize` field
+    /// decodes to a tiny `core_size` (< MIN_CORE_FRAME_BYTES). With the
+    /// dead-code guards this passed validation and could close an access unit
+    /// at a junk boundary; with the fix it must be drained and resynced past.
+    fn bogus_tiny_core_sync() -> Vec<u8> {
+        // Core sync + zero header bytes. fsize = 0 → core_size = 1 (< 10).
+        let mut v = vec![0u8; 10];
+        v[0..4].copy_from_slice(&DTS_CORE_SYNC);
+        // bytes 5,6,7 left zero → fsize = 0 → dts_core_frame_size = 1.
+        assert_eq!(dts_core_frame_size(&v), 1);
+        v
+    }
+
+    #[test]
+    fn bogus_tiny_core_sync_does_not_split_or_drop_real_au() {
+        // A real core frame followed by an extension substream that happens to
+        // contain a false core sync whose fsize decodes tiny. The bogus sync
+        // must NOT close the real access unit early (dropping the rest of the
+        // extension) nor emit a junk few-byte frame — it must be skipped, and
+        // the whole core + extension preserved as one access unit.
+        let mut parser = DtsParser::new();
+
+        // Frame 1: core(512) + an extension whose body embeds a bogus tiny
+        // core sync midway through.
+        let mut ext = make_dts_ext(256);
+        // Embed the bogus core sync inside the extension body (offset 64).
+        let bogus = bogus_tiny_core_sync();
+        ext[64..64 + bogus.len()].copy_from_slice(&bogus);
+
+        let mut frame1 = make_dts_core(512);
+        frame1.extend_from_slice(&ext);
+
+        // No next REAL core yet → frame 1 held.
+        assert!(
+            parser.parse(&make_pes(frame1, Some(90000))).is_empty(),
+            "bogus tiny core sync must not close the AU; wait for a real core"
+        );
+
+        // Frame 2's real core arrives — closes frame 1.
+        let f = parser.parse(&make_pes(make_dts_core(640), Some(93000)));
+        assert_eq!(f.len(), 1, "exactly one real access unit emitted");
+        assert_eq!(
+            f[0].data.len(),
+            512 + 256,
+            "AU must be the full core + extension, not split at the bogus sync"
+        );
+        assert_eq!(f[0].pts_ns, pts_to_ns(90000), "AU keeps the core's PTS");
+
+        let tail = parser.flush();
+        assert_eq!(tail.len(), 1);
+        assert_eq!(tail[0].data.len(), 640);
+    }
+
+    #[test]
+    fn forced_emit_does_not_corrupt_next_au_pts() {
+        // When the buffer exceeds MAX_AU_BYTES with no next core sync, the
+        // parser force-emits for forward progress. The current PES at that
+        // point is an extension-substream PES (later PTS). The forced path must
+        // NOT make that extension PTS the base of the NEXT access unit.
+        let mut parser = DtsParser::new();
+
+        // Core PES at the real PTS, then a giant extension (no next core) that
+        // pushes the buffer past MAX_AU_BYTES, forcing an emit.
+        let core_pts = 90000i64;
+        assert!(
+            parser
+                .parse(&make_pes(make_dts_core(512), Some(core_pts)))
+                .is_empty()
+        );
+        let ext_pts = 120000i64; // later extension-PES timestamp
+        let big_ext = make_dts_ext(MAX_AU_BYTES + 1024);
+        let f = parser.parse(&make_pes(big_ext, Some(ext_pts)));
+        assert_eq!(f.len(), 1, "oversized buffer force-emits one AU");
+        assert_eq!(
+            f[0].pts_ns,
+            pts_to_ns(core_pts),
+            "forced AU keeps the core PTS"
+        );
+
+        // The next REAL core PES arrives with its own PTS. Its AU must inherit
+        // THIS core's PTS, not the prior extension PES timestamp.
+        let next_core_pts = 150000i64;
+        assert!(
+            parser
+                .parse(&make_pes(make_dts_core(512), Some(next_core_pts)))
+                .is_empty()
+        );
+        let next_next_pts = 180000i64;
+        let f2 = parser.parse(&make_pes(make_dts_core(512), Some(next_next_pts)));
+        assert_eq!(f2.len(), 1);
+        assert_eq!(
+            f2[0].pts_ns,
+            pts_to_ns(next_core_pts),
+            "AU after a forced emit must use the next core's PTS, not the \
+             stale extension PTS"
+        );
     }
 
     #[test]

src/mux/codec/dvdsub.rs

@@ -30,6 +30,7 @@ impl CodecParser for DvdSubParser {
             pts_ns,
             keyframe: true,
             data: pes.data.clone(),
+            duration_ns: None,
         }]
     }
 

src/mux/codec/h264.rs

@@ -38,8 +38,11 @@ impl CodecParser for H264Parser {
             return Vec::new();
         }
 
-        // Use DTS when available (monotonic for B-frame content), fall back to PTS
-        let pts_ns = pes.dts.or(pes.pts).map(pts_to_ns).unwrap_or(0);
+        // MKV block timecodes are PRESENTATION timestamps; frames are stored in
+        // 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);
 
         // Scan NAL units for SPS, PPS, and IDR detection
         let mut keyframe = false;
@@ -85,6 +88,7 @@ impl CodecParser for H264Parser {
             pts_ns,
             keyframe,
             data: frame_data,
+            duration_ns: None,
         }]
     }
 
@@ -176,14 +180,16 @@ impl<'a> Iterator for NalIterator<'a> {
 }
 
 /// Find the position of the next start code (00 00 01) at or after `from`.
+///
+/// Backed by `memchr::memmem::find` for SIMD-accelerated bytestring
+/// search. On AVX2-capable x86_64 this runs ~5–10× the byte-by-byte
+/// scan that preceded it; on a 200 KB UHD HEVC frame the saving is
+/// in the hundreds of microseconds per call.
 pub fn find_start_code(data: &[u8], from: usize) -> Option<usize> {
     if data.len() < from + 3 {
         return None;
     }
-    // Range excludes last 2 bytes since we read 3 bytes at each position.
-    // data.len()-2 as exclusive upper bound means last checked index is data.len()-3,
-    // which accesses data[len-3], data[len-2], data[len-1] — all valid.
-    (from..data.len() - 2).find(|&i| data[i] == 0x00 && data[i + 1] == 0x00 && data[i + 2] == 0x01)
+    memchr::memmem::find(&data[from..], b"\x00\x00\x01").map(|rel| from + rel)
 }
 
 /// Skip past the start code at position `pos`, returning the first byte after it.
@@ -448,10 +454,10 @@ mod tests {
         assert!(frames.is_empty());
     }
 
-    // --- DTS preferred over PTS when present ---
+    // --- PTS (presentation) used for the MKV block timecode, not DTS ---
 
     #[test]
-    fn dts_preferred_over_pts() {
+    fn pts_preferred_over_dts() {
         let mut parser = H264Parser::new();
 
         let mut data = Vec::new();
@@ -461,13 +467,13 @@ mod tests {
 
         let pes = PesPacket {
             pid: 0x1011,
-            pts: Some(180000), // 2 seconds
-            dts: Some(90000),  // 1 second
+            pts: Some(180000), // 2 seconds (presentation)
+            dts: Some(90000),  // 1 second (decode)
             data,
         };
         let frames = parser.parse(&pes);
         assert_eq!(frames.len(), 1);
-        // DTS should be used, not PTS
-        assert_eq!(frames[0].pts_ns, 1_000_000_000);
+        // PTS must be used — MKV block timecodes are presentation timestamps.
+        assert_eq!(frames[0].pts_ns, 2_000_000_000);
     }
 }

src/mux/codec/hevc.rs

@@ -48,17 +48,30 @@ impl CodecParser for HevcParser {
             return Vec::new();
         }
 
-        // Use DTS when available (monotonic for B-frame content), fall back to PTS
-        let pts_ns = pes.dts.or(pes.pts).map(pts_to_ns).unwrap_or(0);
+        // MKV block timecodes are PRESENTATION timestamps; frames are stored
+        // in decode order (the order they arrive here) and the player reorders
+        // for display by timecode. So use PTS, not DTS — using DTS makes the
+        // 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 data = &pes.data;
         let mut keyframe = false;
-        let mut frame_data = Vec::new();
+        // Pre-size: output is ~input bytes with a few 4-byte length
+        // prefixes added. UHD frames are 150-300 KB; the unsized Vec
+        // growth chain otherwise reallocs 5-7× per frame.
+        let mut frame_data = Vec::with_capacity(data.len() + 64);
 
         // Single-pass NAL scan: extract params, detect keyframes, build length-prefixed output
         let mut pos = 0;
         while let Some(sc_pos) = find_start_code(data, pos) {
             if let Some(nal_start) = skip_start_code(data, sc_pos) {
                 let next = find_start_code(data, nal_start).unwrap_or(data.len());
+                // Strip the leading zeros of the following start code. For a
+                // conforming bitstream this is lossless: rbsp_trailing_bits()
+                // sets a stop-one bit, so the final byte of any RBSP is never
+                // 0x00 — the only trailing zeros here belong to the next
+                // 00 00 (00) 01 prefix.
                 let mut end = next;
                 while end > nal_start && data[end - 1] == 0x00 {
                     end -= 1;
@@ -107,6 +120,7 @@ impl CodecParser for HevcParser {
             pts_ns,
             keyframe,
             data: frame_data,
+            duration_ns: None,
         }]
     }
 
@@ -120,34 +134,41 @@ impl CodecParser for HevcParser {
         // Full HEVCDecoderConfigurationRecord is complex — for now, concatenate
         let mut record = Vec::new();
 
-        // Minimal HEVCDecoderConfigurationRecord header
+        // Minimal HEVCDecoderConfigurationRecord header.
+        //
+        // The stored SPS NAL is [2-byte HEVC NAL header][SPS RBSP...].
+        // The RBSP begins at sps[2]; profile_tier_level() begins one byte
+        // later, after sps_video_parameter_set_id u(4) +
+        // sps_max_sub_layers_minus1 u(3) + sps_temporal_id_nesting_flag u(1)
+        // (= sps[2], a full byte). So the profile_tier_level fields are:
+        //   sps[3]      general_profile_space u(2)+tier u(1)+profile_idc u(5)
+        //   sps[4..8]   general_profile_compatibility_flags u(32)
+        //   sps[8..14]  general_constraint_indicator_flags 48 bits
+        //   sps[14]     general_level_idc u(8)
+        // (Byte-aligned read; emulation-prevention bytes within the first
+        // 15 SPS bytes are not handled — extremely rare and matches the
+        // pre-existing simplification.)
         record.push(1); // configurationVersion
-        // General profile space, tier flag, profile IDC from SPS
-        if sps.len() > 3 {
-            record.push(sps[1]); // general_profile_space + general_tier_flag + general_profile_idc
+        // general_profile_space + general_tier_flag + general_profile_idc
+        record.push(if sps.len() > 3 { sps[3] } else { 0 });
+        // general_profile_compatibility_flags (4 bytes) — SPS bytes 4..8
+        if sps.len() > 7 {
+            record.extend_from_slice(&sps[4..8]);
         } else {
-            record.push(0);
+            let avail = sps.len().saturating_sub(4).min(4);
+            record.extend_from_slice(&sps[sps.len().min(4)..sps.len().min(8)]);
+            record.extend_from_slice(&vec![0u8; 4 - avail]);
         }
-        // general_profile_compatibility_flags (4 bytes) — from SPS bytes 2..6
-        if sps.len() > 5 {
-            record.extend_from_slice(&sps[2..6]);
+        // general_constraint_indicator_flags (6 bytes) — SPS bytes 8..14
+        if sps.len() > 13 {
+            record.extend_from_slice(&sps[8..14]);
         } else {
-            record.extend_from_slice(&[0, 0, 0, 0]);
+            let avail = sps.len().saturating_sub(8).min(6);
+            record.extend_from_slice(&sps[sps.len().min(8)..sps.len().min(14)]);
+            record.extend_from_slice(&vec![0u8; 6 - avail]);
         }
-        // general_constraint_indicator_flags (6 bytes) — from SPS bytes 6..12
-        if sps.len() > 11 {
-            record.extend_from_slice(&sps[6..12]);
-        } else {
-            let avail = sps.len().saturating_sub(6).min(6);
-            if avail > 0 {
-                record.extend_from_slice(&sps[6..6 + avail]);
-                record.extend_from_slice(&vec![0u8; 6 - avail]);
-            } else {
-                record.extend_from_slice(&[0, 0, 0, 0, 0, 0]);
-            }
-        }
-        // general_level_idc
-        record.push(if sps.len() > 12 { sps[12] } else { 0 });
+        // general_level_idc — SPS byte 14
+        record.push(if sps.len() > 14 { sps[14] } else { 0 });
         // min_spatial_segmentation_idc (4 + 12 bits)
         record.extend_from_slice(&[0xF0, 0x00]);
         // parallelismType (6 + 2 bits)
@@ -264,6 +285,103 @@ mod tests {
         );
     }
 
+    #[test]
+    fn hvcc_profile_tier_level_offsets() {
+        // The hvcC fixed header must read profile_tier_level from the SPS
+        // RBSP, not from the NAL header. Stored SPS = [2-byte NAL header][RBSP].
+        // RBSP layout (byte-aligned):
+        //   sps[2]      sps_vps_id/max_sub_layers/temporal_nesting
+        //   sps[3]      general_profile_space+tier+profile_idc
+        //   sps[4..8]   general_profile_compatibility_flags
+        //   sps[8..14]  general_constraint_indicator_flags
+        //   sps[14]     general_level_idc
+        let mut parser = HevcParser::new();
+
+        // Distinct, recognizable values for each field.
+        let sps_rbsp: [u8; 13] = [
+            0xAB, // sps[2]  (vps_id etc.) — must NOT leak into profile fields
+            0x21, // sps[3]  profile byte: space=0, tier=0, profile_idc=1
+            0x60, 0x00, 0x00, 0x00, // sps[4..8] compat flags
+            0x90, 0x00, 0x00, 0x00, 0x00, 0x00, // sps[8..14] constraint flags
+            0x7B, // sps[14] level_idc = 123
+        ];
+
+        let mut data = Vec::new();
+        // VPS
+        data.extend_from_slice(&[0x00, 0x00, 0x01]);
+        data.extend_from_slice(&hevc_nal_header(32));
+        data.extend_from_slice(&[0xAA, 0xBB, 0xCC]);
+        // SPS — 2-byte header + the structured RBSP above
+        data.extend_from_slice(&[0x00, 0x00, 0x01]);
+        data.extend_from_slice(&hevc_nal_header(33));
+        data.extend_from_slice(&sps_rbsp);
+        // PPS
+        data.extend_from_slice(&[0x00, 0x00, 0x01]);
+        data.extend_from_slice(&hevc_nal_header(34));
+        data.extend_from_slice(&[0xDD, 0xEE]);
+
+        let pes = make_pes(data, Some(0));
+        parser.parse(&pes);
+
+        let cp = parser
+            .codec_private()
+            .expect("codec_private should be Some");
+
+        // record[0] = configurationVersion
+        assert_eq!(cp[0], 1, "configurationVersion");
+        // record[1] = general_profile_space+tier+profile_idc  <- sps[3]
+        assert_eq!(
+            cp[1], 0x21,
+            "profile byte must come from SPS RBSP, not NAL hdr"
+        );
+        // record[2..6] = general_profile_compatibility_flags  <- sps[4..8]
+        assert_eq!(&cp[2..6], &[0x60, 0x00, 0x00, 0x00], "compatibility flags");
+        // record[6..12] = general_constraint_indicator_flags  <- sps[8..14]
+        assert_eq!(
+            &cp[6..12],
+            &[0x90, 0x00, 0x00, 0x00, 0x00, 0x00],
+            "constraint flags"
+        );
+        // record[12] = general_level_idc  <- sps[14]
+        assert_eq!(cp[12], 0x7B, "level_idc must come from sps[14]");
+    }
+
+    #[test]
+    fn hvcc_short_sps_does_not_panic() {
+        // A truncated SPS must still produce a fixed header without panicking
+        // and zero-pad the missing profile/level bytes.
+        let mut parser = HevcParser::new();
+
+        let mut data = Vec::new();
+        data.extend_from_slice(&[0x00, 0x00, 0x01]);
+        data.extend_from_slice(&hevc_nal_header(32));
+        data.extend_from_slice(&[0xAA]);
+        // SPS with only 3 RBSP bytes (stored len = 5): forces every guard path
+        data.extend_from_slice(&[0x00, 0x00, 0x01]);
+        data.extend_from_slice(&hevc_nal_header(33));
+        data.extend_from_slice(&[0x11, 0x22, 0x33]);
+        data.extend_from_slice(&[0x00, 0x00, 0x01]);
+        data.extend_from_slice(&hevc_nal_header(34));
+        data.extend_from_slice(&[0xDD]);
+
+        let pes = make_pes(data, Some(0));
+        parser.parse(&pes);
+
+        let cp = parser
+            .codec_private()
+            .expect("codec_private should be Some");
+        // sps stored = [hdr0, hdr1, 0x11, 0x22, 0x33], len 5.
+        // profile byte = sps[3] = 0x22; everything past sps[4]=0x33 is absent.
+        assert_eq!(cp[0], 1);
+        assert_eq!(cp[1], 0x22, "profile byte = sps[3]");
+        // compat flags: only sps[4]=0x33 present, rest zero-padded.
+        assert_eq!(&cp[2..6], &[0x33, 0x00, 0x00, 0x00]);
+        // constraint flags: none present, all zero.
+        assert_eq!(&cp[6..12], &[0x00, 0x00, 0x00, 0x00, 0x00, 0x00]);
+        // level_idc: absent, zero.
+        assert_eq!(cp[12], 0x00);
+    }
+
     #[test]
     fn codec_private_none_before_params() {
         let parser = HevcParser::new();
@@ -470,6 +588,33 @@ mod tests {
         assert_eq!(frames[0].pts_ns, 1_000_000_000);
     }
 
+    // --- PTS (presentation), not DTS, drives the MKV block timecode ---
+    // Regression for B-frame presentation: writing DTS as the block timecode
+    // presents frames in decode order (visible judder) and breaks seeking.
+
+    #[test]
+    fn pts_preferred_over_dts() {
+        let mut parser = HevcParser::new();
+
+        let mut data = Vec::new();
+        data.extend_from_slice(&[0x00, 0x00, 0x01]);
+        data.extend_from_slice(&hevc_nal_header(1)); // TRAIL_R slice
+        data.extend_from_slice(&[0x10, 0x20]);
+
+        let pes = PesPacket {
+            pid: 0x1011,
+            pts: Some(180000), // 2 s (presentation)
+            dts: Some(90000),  // 1 s (decode)
+            data,
+        };
+        let frames = parser.parse(&pes);
+        assert_eq!(frames.len(), 1);
+        assert_eq!(
+            frames[0].pts_ns, 2_000_000_000,
+            "block timecode must be PTS"
+        );
+    }
+
     // --- Dolby Vision enhancement layer ---
 
     #[test]

src/mux/codec/lpcm.rs

@@ -1,24 +1,39 @@
 //! BD/DVD LPCM (Linear PCM) audio parser.
 //!
-//! BD LPCM PES packets have a 4-byte header:
+//! BD LPCM PES packets (TS stream type 0x80) carry a 4-byte header on the
+//! elementary-stream payload:
 //!   Bytes 0-1: audio frame number
 //!   Byte 2:    reserved
 //!   Byte 3:    quantization (bits 7-6), sample rate (bits 5-4), channel assignment (bits 3-0)
+//! This header is part of the ES payload, so the BD parser must strip it.
 //!
-//! DVD LPCM (private stream 1, sub-stream 0xA0-0xA7) has a 3-byte header.
+//! DVD LPCM lives in private stream 1 (sub-stream 0xA0-0xA7). Its 7-byte
+//! private sub-header (sub_id + frames + first-access-unit-ptr(2) + emphasis +
+//! quant/freq + channels) is stripped by `PsDemuxer` while demuxing the
+//! Program Stream. By the time a DVD LPCM `PesPacket` reaches this parser its
+//! `data` is already raw PCM, so the parser must NOT strip any further bytes —
+//! doing so drops one sample pair per PES and drifts the audio.
 //!
-//! The raw PCM data follows the header. No framing is needed — each PES
-//! payload minus its header is one complete audio frame.
+//! The two origins are distinguished by the `strip_header` flag: BD = strip,
+//! DVD = leave intact. The raw PCM data is otherwise one complete audio frame
+//! per PES; no framing is needed.
 //!
 //! For MKV: codec ID "A_PCM/INT/BIG" (BD) or "A_PCM/INT/LIT" (DVD).
 //! All frames are keyframes (uncompressed audio).
 
 use super::{CodecParser, Frame, PesPacket, pts_to_ns};
 
-/// BD LPCM header size in bytes.
+/// BD LPCM header size in bytes (present on BD-TS LPCM, absent on DVD-PS LPCM
+/// because `PsDemuxer` already stripped the private sub-header).
 const BD_LPCM_HEADER_SIZE: usize = 4;
 
-pub struct LpcmParser;
+pub struct LpcmParser {
+    /// Whether to strip the 4-byte BD LPCM header from each PES payload.
+    ///
+    /// `true` for BD-TS LPCM (header still present), `false` for DVD-PS LPCM
+    /// (header already removed by `PsDemuxer`).
+    strip_header: bool,
+}
 
 impl Default for LpcmParser {
     fn default() -> Self {
@@ -27,23 +42,37 @@ impl Default for LpcmParser {
 }
 
 impl LpcmParser {
+    /// BD-TS LPCM parser: strips the 4-byte BD LPCM header from each PES.
     pub fn new() -> Self {
-        Self
+        Self { strip_header: true }
+    }
+
+    /// DVD-PS LPCM parser: `PsDemuxer` already stripped the private sub-header,
+    /// so the payload is raw PCM and no further bytes are removed.
+    pub fn new_dvd() -> Self {
+        Self {
+            strip_header: false,
+        }
     }
 }
 
 impl CodecParser for LpcmParser {
     fn parse(&mut self, pes: &PesPacket) -> Vec<Frame> {
-        // Skip the BD LPCM header (4 bytes).
+        let offset = if self.strip_header {
+            BD_LPCM_HEADER_SIZE
+        } else {
+            0
+        };
         // If the PES is too short to contain header + data, return nothing.
-        if pes.data.len() <= BD_LPCM_HEADER_SIZE {
+        if pes.data.len() <= offset {
             return Vec::new();
         }
         let pts_ns = pes.pts.map(pts_to_ns).unwrap_or(0);
         vec![Frame {
             pts_ns,
             keyframe: true,
-            data: pes.data[BD_LPCM_HEADER_SIZE..].to_vec(),
+            data: pes.data[offset..].to_vec(),
+            duration_ns: None,
         }]
     }
 
@@ -83,6 +112,56 @@ mod tests {
         assert_eq!(frames[0].pts_ns, 1_000_000_000); // 90000 ticks = 1 second
     }
 
+    #[test]
+    fn bd_lpcm_strips_4_byte_header() {
+        // BD-TS LPCM: the 4-byte BD header is part of the ES payload and must
+        // be stripped, leaving exactly the PCM bytes.
+        let mut parser = LpcmParser::new();
+        let header = vec![0x00, 0x01, 0x00, 0b1001_0001];
+        let pcm = vec![0x11, 0x22, 0x33, 0x44, 0x55, 0x66, 0x77, 0x88];
+        let mut data = header;
+        data.extend_from_slice(&pcm);
+
+        let frames = parser.parse(&make_pes(data, Some(0)));
+        assert_eq!(frames.len(), 1);
+        assert_eq!(frames[0].data, pcm, "BD must strip exactly 4 header bytes");
+    }
+
+    #[test]
+    fn dvd_lpcm_preserves_all_pcm_bytes() {
+        // DVD-PS LPCM: PsDemuxer already removed the 7-byte private sub-header,
+        // so the payload handed to this parser is raw PCM. The DVD parser must
+        // NOT strip any further bytes (the round-2 audit Finding 3 bug: the BD
+        // 4-byte strip dropped one sample pair per PES, drifting the audio).
+        let mut parser = LpcmParser::new_dvd();
+        let pcm = vec![0xDE, 0xAD, 0xBE, 0xEF, 0xCA, 0xFE, 0x01, 0x02];
+        let frames = parser.parse(&make_pes(pcm.clone(), Some(90000)));
+
+        assert_eq!(frames.len(), 1);
+        assert_eq!(
+            frames[0].data, pcm,
+            "DVD must preserve every PCM byte — no second strip"
+        );
+        assert_eq!(frames[0].pts_ns, 1_000_000_000);
+    }
+
+    #[test]
+    fn dvd_lpcm_emits_short_payload_bd_would_drop() {
+        // A 4-byte raw-PCM DVD payload (1 sample pair at 16-bit stereo). The BD
+        // parser drops <= 4 bytes as "header only"; the DVD parser must emit it.
+        let mut bd = LpcmParser::new();
+        let mut dvd = LpcmParser::new_dvd();
+        let pcm = vec![0xAA, 0xBB, 0xCC, 0xDD];
+
+        assert!(
+            bd.parse(&make_pes(pcm.clone(), Some(0))).is_empty(),
+            "BD treats 4 bytes as header-only"
+        );
+        let frames = dvd.parse(&make_pes(pcm.clone(), Some(0)));
+        assert_eq!(frames.len(), 1);
+        assert_eq!(frames[0].data, pcm);
+    }
+
     #[test]
     fn always_keyframe() {
         let mut parser = LpcmParser::new();

src/mux/codec/mod.rs

@@ -29,6 +29,13 @@ pub struct Frame {
     pub keyframe: bool,
     /// Frame data (elementary stream bytes).
     pub data: Vec<u8>,
+    /// Optional duration in nanoseconds — only set by parsers that
+    /// can compute one (currently PGS, which pairs a display PCS
+    /// with the following empty PCS). When `Some`, the MKV muxer
+    /// emits a `BlockGroup` with `BlockDuration` instead of a
+    /// `SimpleBlock`; without it players guess the display interval
+    /// (subtitles linger past their end-time).
+    pub duration_ns: Option<u64>,
 }
 
 /// Convert 90kHz PTS to nanoseconds (round to nearest).
@@ -45,6 +52,18 @@ pub trait CodecParser: Send {
     /// Some (TrueHD): multiple access units per PES.
     fn parse(&mut self, pes: &PesPacket) -> Vec<Frame>;
 
+    /// Drain any access unit still buffered after the last PES.
+    ///
+    /// Parsers that buffer across PES boundaries to assemble a complete
+    /// access unit (e.g. DTS-HD, whose extension substreams arrive in
+    /// separate PES packets) hold the final unit until they can prove it's
+    /// complete. At end-of-stream there is no following packet to prove it,
+    /// so the demuxer calls `flush()` once after the last PES to emit it.
+    /// Default: nothing buffered, no tail.
+    fn flush(&mut self) -> Vec<Frame> {
+        Vec::new()
+    }
+
     /// Get codec initialization data (e.g., SPS+PPS for H.264).
     /// Returns None until enough data has been seen.
     fn codec_private(&self) -> Option<Vec<u8>>;
@@ -71,6 +90,7 @@ impl CodecParser for PassthroughParser {
             pts_ns,
             keyframe: self.keyframe,
             data: pes.data.clone(),
+            duration_ns: None,
         }]
     }
 
@@ -82,7 +102,16 @@ impl CodecParser for PassthroughParser {
 /// Create the appropriate parser for a codec, with optional codec private data.
 ///
 /// For DvdSub, `codec_data` should be the pre-formatted VobSub .idx palette header.
-pub fn parser_for_codec(codec: Codec, codec_data: Option<Vec<u8>>) -> Box<dyn CodecParser> {
+///
+/// `is_dvd_ps` selects the DVD program-stream variant where it matters: DVD
+/// LPCM arrives with its private sub-header already stripped by the
+/// `PsDemuxer`, so the LPCM parser must NOT strip the 4-byte BD LPCM header
+/// again (that would drop one PCM sample pair per PES → progressive drift).
+pub fn parser_for_codec(
+    codec: Codec,
+    codec_data: Option<Vec<u8>>,
+    is_dvd_ps: bool,
+) -> Box<dyn CodecParser> {
     match codec {
         Codec::H264 => Box::new(h264::H264Parser::new()),
         Codec::Hevc => Box::new(hevc::HevcParser::new()),
@@ -92,6 +121,7 @@ pub fn parser_for_codec(codec: Codec, codec_data: Option<Vec<u8>>) -> Box<dyn Co
         Codec::DtsHdMa | Codec::DtsHdHr | Codec::Dts => Box::new(dts::DtsParser::new()),
         Codec::TrueHd => Box::new(truehd::TrueHdParser::new()),
         Codec::Pgs => Box::new(pgs::PgsParser::new()),
+        Codec::Lpcm if is_dvd_ps => Box::new(lpcm::LpcmParser::new_dvd()),
         Codec::Lpcm => Box::new(lpcm::LpcmParser::new()),
         Codec::DvdSub => Box::new(dvdsub::DvdSubParser::new(codec_data)),
         _ => Box::new(PassthroughParser::new(true)),

src/mux/codec/mpeg2.rs

@@ -96,9 +96,14 @@ impl CodecParser for Mpeg2Parser {
             return Vec::new();
         }
 
-        let pts_ns = pes.dts.or(pes.pts).map(pts_to_ns).unwrap_or(0);
+        // MKV block timecodes are PRESENTATION timestamps; frames are stored in
+        // 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 data = &pes.data;
         let mut keyframe = false;
+        let mut has_picture = false;
 
         // Scan for start codes in the elementary stream data.
         let mut pos = 0;
@@ -176,6 +181,7 @@ impl CodecParser for Mpeg2Parser {
                 PICTURE_CODE => {
                     // Picture header: bytes after start code contain temporal_reference
                     // (10 bits) + picture_coding_type (3 bits).
+                    has_picture = true;
                     if sc + 5 < data.len() {
                         let picture_coding_type = (data[sc + 5] >> 3) & 0x07;
                         if picture_coding_type == PICTURE_TYPE_I {
@@ -190,10 +196,28 @@ impl CodecParser for Mpeg2Parser {
             }
         }
 
+        // A PES that carried a sequence header but no picture start code is a
+        // parameter-set-only access unit: it has no coded picture to emit.
+        // Emitting it as a standalone keyframe would put bare sequence-header
+        // bytes into frame data with no picture. The sequence header is
+        // captured into codec_private above and is re-emitted in-band on the
+        // next real picture's PES, so dropping the empty access unit loses
+        // nothing. Mirrors how the H.264/HEVC parsers skip parameter-set-only
+        // access units.
+        //
+        // Conservative: only drop when this PES actually contained a sequence
+        // header and no picture. A PES with neither (e.g. a slice
+        // continuation) still passes through unchanged, preserving real
+        // keyframe detection.
+        if !has_picture && contains_seq_header(data) {
+            return Vec::new();
+        }
+
         vec![Frame {
             pts_ns,
             keyframe,
             data: pes.data.clone(),
+            duration_ns: None,
         }]
     }
 
@@ -240,6 +264,21 @@ fn parse_aspect_ratio(hdr: &[u8]) -> Option<(u8, u8)> {
     Some(ASPECT_RATIOS[ar_code])
 }
 
+/// Returns true if `data` contains a sequence-header start code (00 00 01 B3).
+fn contains_seq_header(data: &[u8]) -> bool {
+    let mut pos = 0;
+    while let Some(sc) = find_start_code(data, pos) {
+        if sc + 3 >= data.len() {
+            break;
+        }
+        if data[sc + 3] == SEQ_HEADER_CODE {
+            return true;
+        }
+        pos = sc + 4;
+    }
+    false
+}
+
 /// Find the position of the next start code (00 00 01) at or after `from`.
 fn find_start_code(data: &[u8], from: usize) -> Option<usize> {
     if data.len() < from + 3 {
@@ -428,15 +467,15 @@ mod tests {
         assert!(has_ext, "codec_private should include sequence extension");
     }
 
-    // --- I-frame with sequence header = keyframe ---
+    // --- sequence header + picture = keyframe ---
 
     #[test]
-    fn sequence_header_implies_keyframe() {
+    fn sequence_header_with_picture_is_keyframe() {
         let mut parser = Mpeg2Parser::new();
 
         let mut data = Vec::new();
         data.extend_from_slice(&make_seq_header(720, 480, 3, 4));
-        // Even without an explicit picture header, a sequence header implies I-frame.
+        data.extend_from_slice(&make_picture_header(PICTURE_TYPE_I));
         data.extend_from_slice(&[0xFF; 16]);
 
         let pes = make_pes(data, Some(0));
@@ -444,6 +483,43 @@ mod tests {
 
         assert_eq!(frames.len(), 1);
         assert!(frames[0].keyframe);
+        // codecPrivate is still captured.
+        assert!(parser.codec_private().is_some());
+    }
+
+    // --- parameter-set-only PES (seq header, no picture) emits no frame ---
+
+    #[test]
+    fn sequence_header_only_pes_emits_no_frame() {
+        let mut parser = Mpeg2Parser::new();
+
+        // A PES carrying only a sequence header (+ extension), no picture.
+        let mut data = Vec::new();
+        data.extend_from_slice(&make_seq_header(1920, 1080, 3, 4));
+        data.extend_from_slice(&[0x00, 0x00, 0x01, SEQ_EXT_CODE]);
+        data.extend_from_slice(&[0x14, 0x8A, 0x00, 0x01, 0x00, 0x00]);
+
+        let pes = make_pes(data, Some(0));
+        let frames = parser.parse(&pes);
+
+        // No coded picture → no frame emitted, but the sequence header is
+        // still captured for codecPrivate.
+        assert!(
+            frames.is_empty(),
+            "parameter-set-only PES should not emit a frame"
+        );
+        assert!(
+            parser.codec_private().is_some(),
+            "sequence header should still be captured into codec_private"
+        );
+
+        // A following picture-bearing PES emits the real keyframe.
+        let mut data2 = Vec::new();
+        data2.extend_from_slice(&make_picture_header(PICTURE_TYPE_I));
+        data2.extend_from_slice(&[0xFF; 16]);
+        let frames2 = parser.parse(&make_pes(data2, Some(3600)));
+        assert_eq!(frames2.len(), 1);
+        assert!(frames2[0].keyframe);
     }
 
     // --- PTS conversion ---

src/mux/codec/pgs.rs

@@ -1,12 +1,39 @@
 //! HDMV PGS (Presentation Graphics Stream) subtitle parser.
 //!
-//! PGS segments: PCS, WDS, PDS, ODS, END.
-//! Each PES packet contains one or more segments.
-//! All segments are keyframes (no inter-segment dependencies).
+//! PGS segments: PCS, WDS, PDS, ODS, END. Each PES packet starts with
+//! one of those (segment_type byte at offset 0).
+//!
+//! Subtitle display lifecycle (BD spec):
+//! - A "display" PCS (number_of_composition_objects > 0) starts a
+//!   visible subtitle. Its WDS/PDS/ODS follow.
+//! - A later "empty" PCS (number_of_composition_objects == 0) clears
+//!   the screen.
+//!
+//! For Matroska output we collapse that pair into one block with
+//! `BlockDuration` set to (clear_pts - display_pts). Without a
+//! duration, hardware players linger on the last bitmap until the
+//! next subtitle replaces it — which can be many seconds, and on a
+//! disc where the final subtitle has no follower, until end of file.
 
 use super::{CodecParser, Frame, PesPacket, pts_to_ns};
 
-pub struct PgsParser;
+const SEGMENT_PCS: u8 = 0x16;
+// Upper bound on a pending display set's accumulated bytes. Real PGS
+// display sets are small (a 1080p RLE bitmap plus palette is well under
+// 1 MB); a stream that keeps appending non-PCS segments without ever
+// emitting a PCS is malformed. Cap accumulation to bound memory and
+// drop further appends until the next PCS resyncs the parser. Mirrors
+// the MAX_*_BYTES / MAX_*_BUF caps in the DTS and AC-3 parsers.
+const MAX_PGS_PENDING_BYTES: usize = 4 * 1024 * 1024;
+// Offset within the PES payload at which number_of_composition_objects
+// lives in a PCS: 3-byte segment header + 10 bytes of PCS fields
+// (video_w/h, frame_rate, comp_num, comp_state, palette_update,
+// palette_id_ref) = 13.
+const PCS_NUM_OBJECTS_OFFSET: usize = 13;
+
+pub struct PgsParser {
+    pending: Option<(i64, Vec<u8>)>,
+}
 
 impl Default for PgsParser {
     fn default() -> Self {
@@ -16,7 +43,7 @@ impl Default for PgsParser {
 
 impl PgsParser {
     pub fn new() -> Self {
-        Self
+        Self { pending: None }
     }
 }
 
@@ -26,11 +53,68 @@ impl CodecParser for PgsParser {
             return Vec::new();
         }
         let pts_ns = pes.pts.map(pts_to_ns).unwrap_or(0);
-        vec![Frame {
-            pts_ns,
-            keyframe: true,
-            data: pes.data.clone(),
-        }]
+
+        let is_pcs = pes.data[0] == SEGMENT_PCS;
+        let pcs_num_objects = if is_pcs && pes.data.len() > PCS_NUM_OBJECTS_OFFSET {
+            Some(pes.data[PCS_NUM_OBJECTS_OFFSET])
+        } else {
+            None
+        };
+
+        let mut out = Vec::new();
+        match pcs_num_objects {
+            // Clear/empty PCS — closes any pending display. Drop the
+            // clear segment itself; BlockDuration covers the screen
+            // wipe.
+            Some(0) => {
+                if let Some((start_pts, data)) = self.pending.take() {
+                    let duration = pts_ns.saturating_sub(start_pts).max(0) as u64;
+                    out.push(Frame {
+                        pts_ns: start_pts,
+                        keyframe: true,
+                        data,
+                        duration_ns: Some(duration),
+                    });
+                }
+            }
+            // Display PCS — start a new pending. If a prior display
+            // was never explicitly cleared (replace-without-clear),
+            // emit it with the new PCS's PTS as its end.
+            Some(_) => {
+                if let Some((start_pts, data)) = self.pending.take() {
+                    let duration = pts_ns.saturating_sub(start_pts).max(0) as u64;
+                    out.push(Frame {
+                        pts_ns: start_pts,
+                        keyframe: true,
+                        data,
+                        duration_ns: Some(duration),
+                    });
+                }
+                self.pending = Some((pts_ns, pes.data.clone()));
+            }
+            // Non-PCS first segment — either a continuation of the
+            // current display set, or non-standard layout. If we have
+            // a pending display, append; otherwise emit as-is.
+            None => {
+                if let Some((_, ref mut buf)) = self.pending {
+                    // Bound accumulation: a well-formed display set is small.
+                    // Past the cap, drop further appends (malformed stream);
+                    // the next PCS will take/replace `pending` and resync.
+                    if buf.len() + pes.data.len() <= MAX_PGS_PENDING_BYTES {
+                        buf.extend_from_slice(&pes.data);
+                    }
+                } else {
+                    out.push(Frame {
+                        pts_ns,
+                        keyframe: true,
+                        data: pes.data.clone(),
+                        duration_ns: None,
+                    });
+                }
+            }
+        }
+
+        out
     }
 
     fn codec_private(&self) -> Option<Vec<u8>> {
@@ -52,29 +136,86 @@ mod tests {
         }
     }
 
-    #[test]
-    fn parse_basic_segment() {
-        let mut parser = PgsParser::new();
-        // PGS segment data (PCS = presentation composition segment)
-        let data = vec![0x16, 0x00, 0x00, 0x11, 0x01, 0x02, 0x03];
-        let pes = make_pes(data.clone(), Some(90000));
-        let frames = parser.parse(&pes);
-
-        assert_eq!(frames.len(), 1);
-        assert_eq!(frames[0].data, data);
-        assert_eq!(frames[0].pts_ns, 1_000_000_000);
+    // Minimum-viable PCS bytes: type 0x16, segment_length (2 bytes),
+    // then 11 bytes of PCS fields ending in number_of_composition_objects.
+    fn pcs_bytes(num_objects: u8) -> Vec<u8> {
+        let mut v = vec![SEGMENT_PCS, 0x00, 0x0B];
+        v.extend_from_slice(&[0x07, 0x80, 0x04, 0x38]); // 1920x1080
+        v.push(0x10); // frame_rate
+        v.extend_from_slice(&[0x00, 0x01]); // composition_number
+        v.push(0x80); // composition_state = EpochStart
+        v.push(0x00); // palette_update + reserved
+        v.push(0x00); // palette_id_ref
+        v.push(num_objects);
+        v
     }
 
     #[test]
-    fn all_keyframes() {
+    fn display_then_clear_yields_duration() {
         let mut parser = PgsParser::new();
-        for i in 0..3 {
-            let data = vec![0x16, 0x00, i];
-            let pes = make_pes(data, Some(90000 * i as i64));
-            let frames = parser.parse(&pes);
-            assert_eq!(frames.len(), 1);
-            assert!(frames[0].keyframe, "PGS segment should always be keyframe");
+
+        // Display PCS at PTS 90000 (= 1s)
+        let display = pcs_bytes(1);
+        let frames = parser.parse(&make_pes(display.clone(), Some(90000)));
+        assert!(frames.is_empty(), "display PCS should be pending");
+
+        // Empty PCS at PTS 270000 (= 3s)
+        let clear = pcs_bytes(0);
+        let frames = parser.parse(&make_pes(clear, Some(270000)));
+        assert_eq!(frames.len(), 1);
+        assert_eq!(frames[0].pts_ns, 1_000_000_000);
+        assert_eq!(frames[0].duration_ns, Some(2_000_000_000));
+        assert_eq!(frames[0].data, display);
+    }
+
+    #[test]
+    fn replace_without_clear_still_emits_prior_with_duration() {
+        let mut parser = PgsParser::new();
+        let _ = parser.parse(&make_pes(pcs_bytes(1), Some(90000)));
+        let frames = parser.parse(&make_pes(pcs_bytes(1), Some(180000)));
+        assert_eq!(frames.len(), 1);
+        assert_eq!(frames[0].pts_ns, 1_000_000_000);
+        assert_eq!(frames[0].duration_ns, Some(1_000_000_000));
+    }
+
+    #[test]
+    fn non_pcs_segment_appends_to_pending() {
+        let mut parser = PgsParser::new();
+        let _ = parser.parse(&make_pes(pcs_bytes(1), Some(90000)));
+        // ODS-like segment (type 0x15)
+        let frames = parser.parse(&make_pes(vec![0x15, 0x00, 0x02, 0xAA, 0xBB], Some(90000)));
+        assert!(frames.is_empty());
+        // Clear closes the set; data should include the appended bytes.
+        let frames = parser.parse(&make_pes(pcs_bytes(0), Some(180000)));
+        assert_eq!(frames.len(), 1);
+        let data = &frames[0].data;
+        assert!(data.windows(5).any(|w| w == [0x15, 0x00, 0x02, 0xAA, 0xBB]));
+    }
+
+    #[test]
+    fn pending_buffer_is_capped() {
+        let mut parser = PgsParser::new();
+        // Open a display set.
+        let _ = parser.parse(&make_pes(pcs_bytes(1), Some(90000)));
+
+        // Flood with non-PCS segments far exceeding the cap.
+        let chunk = vec![0x15u8; 256 * 1024]; // 256 KB ODS-like segment
+        let floods = (MAX_PGS_PENDING_BYTES / chunk.len()) + 32;
+        for _ in 0..floods {
+            let frames = parser.parse(&make_pes(chunk.clone(), Some(90000)));
+            assert!(frames.is_empty(), "non-PCS appends should not emit");
         }
+
+        // The pending buffer must not have grown without bound.
+        let pending_len = parser.pending.as_ref().map(|(_, b)| b.len()).unwrap_or(0);
+        assert!(
+            pending_len <= MAX_PGS_PENDING_BYTES,
+            "pending buffer {pending_len} exceeded cap {MAX_PGS_PENDING_BYTES}"
+        );
+
+        // A following PCS still resyncs and emits the (capped) pending set.
+        let frames = parser.parse(&make_pes(pcs_bytes(0), Some(180000)));
+        assert_eq!(frames.len(), 1);
     }
 
     #[test]

src/mux/codec/truehd.rs

@@ -16,6 +16,12 @@ use super::{CodecParser, Frame, PesPacket, pts_to_ns};
 /// Duration of one TrueHD access unit in nanoseconds (1/1200 second).
 const AU_DURATION_NS: i64 = 833_333;
 
+/// Hard cap on the reassembly buffer. A valid TrueHD/MAT access unit is
+/// well under 32 KiB; if the buffer grows far past that without yielding a
+/// frame the stream is malformed, so we drop it and resync rather than grow
+/// without bound. Parity with the AC-3 / DTS / PGS caps.
+const MAX_TRUEHD_BUF: usize = 256 * 1024;
+
 pub struct TrueHdParser {
     buf: Vec<u8>,
     next_pts_ns: i64,
@@ -139,11 +145,18 @@ impl CodecParser for TrueHdParser {
                 pts_ns: self.next_pts_ns,
                 keyframe: is_major_sync,
                 data: self.buf[..unit_bytes].to_vec(),
+                duration_ns: None,
             });
             self.buf.drain(..unit_bytes);
             self.next_pts_ns += AU_DURATION_NS;
         }
 
+        // Bound memory on malformed input: a stream that never yields a
+        // complete frame must not grow the buffer without limit.
+        if self.buf.len() > MAX_TRUEHD_BUF {
+            self.buf.clear();
+        }
+
         frames
     }
 
@@ -152,6 +165,52 @@ impl CodecParser for TrueHdParser {
     }
 }
 
+/// Per-bit channel counts for the TrueHD 8-channel and 6-channel presentation
+/// channel-assignment masks (per the MLP spec / FFmpeg `thd_channels`). Some
+/// bits denote a stereo pair (2), others a single channel (1).
+const THD_8CH: [u8; 13] = [2, 1, 1, 2, 2, 2, 2, 1, 1, 2, 2, 1, 1];
+const THD_6CH: [u8; 5] = [2, 1, 1, 2, 1];
+
+/// Decode the true channel count from a TrueHD major-sync `format_info` word
+/// (the 32 bits immediately after the 0xF8726FBA sync). Returns the richest
+/// presentation's channel count — the 8-channel (e.g. 7.1) presentation when
+/// present, else the 6-channel (5.1) one. This is the real layout that the MPLS
+/// `audio_format` base field (often 5.1 even on a 7.1/Atmos track) understates.
+pub fn truehd_channels(format_info: u32) -> Option<u8> {
+    let ch8 = (format_info & 0x1FFF) as u16; // 8ch_presentation_channel_assignment (13 bits)
+    let ch6 = ((format_info >> 15) & 0x1F) as u16; // 6ch_presentation_channel_assignment (5 bits)
+    let count = |mask: u16, tbl: &[u8]| -> u8 {
+        tbl.iter()
+            .enumerate()
+            .filter(|(i, _)| mask & (1 << i) != 0)
+            .map(|(_, &c)| c)
+            .sum()
+    };
+    if ch8 != 0 {
+        Some(count(ch8, &THD_8CH))
+    } else if ch6 != 0 {
+        Some(count(ch6, &THD_6CH))
+    } else {
+        None
+    }
+}
+
+/// Scan a demuxed TrueHD elementary-stream chunk for the first major sync and
+/// decode its true channel count. The stream may interleave AC-3; we scan for
+/// the major-sync word anywhere and read the following `format_info`.
+pub fn truehd_channels_from_stream(data: &[u8]) -> Option<u8> {
+    let mut p = 0;
+    while p + 8 <= data.len() {
+        let w = u32::from_be_bytes([data[p], data[p + 1], data[p + 2], data[p + 3]]);
+        if (w & 0xFFFF_FFFE) == 0xF872_6FBA {
+            let fi = u32::from_be_bytes([data[p + 4], data[p + 5], data[p + 6], data[p + 7]]);
+            return truehd_channels(fi);
+        }
+        p += 1;
+    }
+    None
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;
@@ -246,4 +305,27 @@ mod tests {
         let parser = TrueHdParser::new();
         assert!(parser.codec_private().is_none());
     }
+
+    #[test]
+    fn truehd_channels_71_from_8ch_presentation() {
+        // 8ch presentation assignment bits 0-4 (LR,C,LFE,LsRs,back-LR) = 2+1+1+2+2 = 8.
+        let format_info = 0x1F; // low 13 bits = 0x1F
+        assert_eq!(truehd_channels(format_info), Some(8));
+    }
+
+    #[test]
+    fn truehd_channels_51_from_6ch_presentation() {
+        // No 8ch presentation; 6ch bits 0-3 (LR,C,LFE,LsRs) = 2+1+1+2 = 6.
+        let format_info = 0xF << 15; // 6ch field = 0xF, 8ch field = 0
+        assert_eq!(truehd_channels(format_info), Some(6));
+    }
+
+    #[test]
+    fn truehd_channels_scan_finds_major_sync() {
+        // [junk][major sync 0xF8726FBA][format_info: 8ch=0x1F -> 7.1]
+        let mut data = vec![0xAA, 0xBB];
+        data.extend_from_slice(&0xF872_6FBAu32.to_be_bytes());
+        data.extend_from_slice(&0x0000_001Fu32.to_be_bytes());
+        assert_eq!(truehd_channels_from_stream(&data), Some(8));
+    }
 }

src/mux/codec/vc1.rs

@@ -41,9 +41,13 @@ impl CodecParser for Vc1Parser {
             return Vec::new();
         }
 
-        // Use DTS when available (monotonic for B-frame content), fall back to PTS
-        let ts_ns = pes.dts.or(pes.pts).map(pts_to_ns).unwrap_or(0);
+        // MKV block timecodes are PRESENTATION timestamps; frames are stored in
+        // 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 mut has_seq_header = false;
+        let mut has_entry_point = false;
         let mut frame_start: Option<usize> = None;
 
         // Scan for start codes (00 00 01 XX)
@@ -67,6 +71,7 @@ impl CodecParser for Vc1Parser {
                     SC_ENTRY_POINT => {
                         let end = find_next_sc(data, i + 4).unwrap_or(data.len());
                         self.entry_point = Some(data[i..end].to_vec());
+                        has_entry_point = true;
                     }
                     SC_FRAME => {
                         // Frame data starts at this start code
@@ -85,17 +90,30 @@ impl CodecParser for Vc1Parser {
         // Keyframe = this PES contains a sequence header (I-frame indicator in BD)
         let keyframe = has_seq_header;
 
-        // Strip sequence header + entry point from frame data — those are in codecPrivate.
-        // Only include data from the frame start code onwards.
+        // Strip sequence header + entry point from frame data — those are in
+        // codecPrivate, not coded-picture data. Only include data from the
+        // frame start code onwards.
         let frame_data = match frame_start {
             Some(start) => &data[start..],
-            None => data, // no frame start code found, pass through entire PES
+            None => {
+                // No frame start code. If this PES carried only parameter sets
+                // (sequence header / entry point, captured above into
+                // codecPrivate), there is no coded picture to emit — drop it
+                // rather than passing parameter bytes through as a bogus
+                // keyframe. Mirrors how the H.264/HEVC parsers skip
+                // parameter-set-only access units.
+                if has_seq_header || has_entry_point {
+                    return Vec::new();
+                }
+                data // genuine picture payload with no leading 0x0D — pass through
+            }
         };
 
         vec![Frame {
             pts_ns: ts_ns,
             keyframe,
             data: frame_data.to_vec(),
+            duration_ns: None,
         }]
     }
 
@@ -342,6 +360,42 @@ mod tests {
         assert_eq!(&frames[0].data[0..4], &[0x00, 0x00, 0x01, SC_FRAME]);
     }
 
+    // --- parameter-set-only PES (seq header + entry point, no frame SC) ---
+
+    #[test]
+    fn param_set_only_pes_emits_no_frame() {
+        let mut parser = Vc1Parser::new();
+
+        // Sequence header + entry point, but NO frame start code (0x0D).
+        let mut data = Vec::new();
+        data.extend_from_slice(&[0x00, 0x00, 0x01, SC_SEQUENCE_HEADER]);
+        data.extend_from_slice(&[0xAA, 0xBB, 0xCC, 0xDD, 0xEE, 0xFF]);
+        data.extend_from_slice(&[0x00, 0x00, 0x01, SC_ENTRY_POINT]);
+        data.extend_from_slice(&[0x11, 0x22, 0x33, 0x44]);
+
+        let pes = make_pes(data, Some(90000));
+        let frames = parser.parse(&pes);
+
+        // No coded picture → no frame emitted (parameter bytes must not be
+        // passed through as a bogus keyframe).
+        assert!(
+            frames.is_empty(),
+            "parameter-set-only PES should not emit a frame"
+        );
+        // But codecPrivate is still captured.
+        assert!(parser.seq_header.is_some());
+        assert!(parser.entry_point.is_some());
+        assert!(parser.codec_private().is_some());
+
+        // A following frame-bearing PES still emits its picture.
+        let mut data2 = Vec::new();
+        data2.extend_from_slice(&[0x00, 0x00, 0x01, SC_FRAME]);
+        data2.extend_from_slice(&[0x55, 0x66, 0x77]);
+        let frames2 = parser.parse(&make_pes(data2, Some(180000)));
+        assert_eq!(frames2.len(), 1);
+        assert_eq!(&frames2[0].data[0..4], &[0x00, 0x00, 0x01, SC_FRAME]);
+    }
+
     // --- empty PES ---
 
     #[test]
@@ -368,10 +422,10 @@ mod tests {
         assert_eq!(frames[0].pts_ns, 1_000_000_000);
     }
 
-    // --- DTS preferred over PTS ---
+    // --- PTS (presentation) used for the MKV block timecode, not DTS ---
 
     #[test]
-    fn dts_preferred_over_pts() {
+    fn pts_preferred_over_dts() {
         let mut parser = Vc1Parser::new();
 
         let mut data = Vec::new();
@@ -380,13 +434,14 @@ mod tests {
 
         let pes = PesPacket {
             pid: 0x1011,
-            pts: Some(180000),
-            dts: Some(90000),
+            pts: Some(180000), // presentation
+            dts: Some(90000),  // decode
             data,
         };
         let frames = parser.parse(&pes);
         assert_eq!(frames.len(), 1);
-        assert_eq!(frames[0].pts_ns, 1_000_000_000);
+        // PTS must be used — MKV block timecodes are presentation timestamps.
+        assert_eq!(frames[0].pts_ns, 2_000_000_000);
     }
 
     // --- find_next_sc utility ---

src/mux/demux_thread.rs

@@ -0,0 +1,350 @@
+//! `DemuxThread` — runs the read+decrypt+demux pipeline on a
+//! dedicated thread, feeding completed `PesPacket` batches to the
+//! caller via a bounded channel.
+//!
+//! ## Why a second worker thread
+//!
+//! With [`crate::sector::PrefetchedSectorSource`] alone, read+decrypt
+//! already runs on a producer thread; the *consumer* (main) thread
+//! still serialises `ts_demuxer.feed` (M2TS parsing) with the codec
+//! parsers. Profiling on the rip1 testbed showed feed at ~37 % and
+//! codec parse at ~44 % of consumer wall time — i.e. feed is heavy
+//! enough that pipelining it with parse pays for itself.
+//!
+//! Splitting them: feed runs in [`DemuxThread`]; the consumer thread
+//! receives `Vec<PesPacket>` batches and runs codec parse + frame
+//! emission only. Total throughput becomes `1/max(feed, parse)`
+//! instead of `1/(feed + parse)`.
+//!
+//! ## Lifecycle
+//!
+//! [`DemuxThread::spawn`] takes ownership of the inner reader and the
+//! demuxer state, returns a handle plus a `Receiver<DemuxBatch>`.
+//! Dropping the handle closes the channel which signals the thread
+//! to exit; the join in `Drop::drop` is bounded.
+
+use crate::halt::Halt;
+use crate::sector::SectorSource;
+use crossbeam_channel::{Receiver, Sender, bounded};
+use std::thread::JoinHandle;
+
+/// Output channel depth. Two batches in flight keeps the consumer
+/// (codec parser) busy without piling up demuxed bytes if it stalls.
+const DEMUX_CHANNEL_DEPTH: usize = 2;
+
+/// One demuxed batch flowing from the demux thread to the consumer.
+pub enum DemuxBatch {
+    /// Successfully demuxed PesPackets — non-empty.
+    Ts(Vec<super::ts::PesPacket>),
+    Ps(Vec<super::ps::PsPacket>),
+    /// Underlying reader returned an error. Terminal.
+    Err(std::io::Error),
+}
+
+/// Spawned demux thread. Drop joins.
+///
+/// In zero-copy mode the thread also owns an opaque
+/// `producer_shell: Option<Box<dyn Send>>` — the join handle of the
+/// upstream producer (sector or byte prefetcher). Dropping the
+/// `DemuxThread` runs the shell's `Drop`, which joins the producer.
+/// `Box<dyn Send>` rather than a concrete type so the same demux
+/// worker can be wired behind either prefetcher kind.
+pub struct DemuxThread {
+    handle: Option<JoinHandle<()>>,
+    #[allow(dead_code)]
+    producer_shell: Option<Box<dyn Send>>,
+}
+
+impl DemuxThread {
+    /// Spawn the demux thread. Returns the thread handle and a
+    /// receiver for [`DemuxBatch`] items.
+    ///
+    /// `reader` is the fully-composed read+decrypt stack (e.g.
+    /// [`PrefetchedSectorSource`](crate::sector::PrefetchedSectorSource)
+    /// wrapping
+    /// [`DecryptingSectorSource`](crate::sector::DecryptingSectorSource)).
+    /// `extents` is what the thread walks; it issues one
+    /// `read_sectors` per batch of `batch_sectors` sectors (aligned
+    /// to 3-sector AACS units when possible).
+    pub fn spawn<S: SectorSource + Send + 'static>(
+        mut reader: S,
+        extents: Vec<crate::disc::Extent>,
+        batch_sectors: u16,
+        halt: Option<Halt>,
+        ts: Option<super::ts::TsDemuxer>,
+        ps: Option<super::ps::PsDemuxer>,
+    ) -> (Self, Receiver<DemuxBatch>) {
+        let (tx, rx) = bounded::<DemuxBatch>(DEMUX_CHANNEL_DEPTH);
+        let mut ts = ts;
+        let mut ps = ps;
+
+        let handle = std::thread::Builder::new()
+            .name("freemkv-demux".into())
+            .spawn(move || {
+                let mut buf = vec![0u8; batch_sectors as usize * 2048];
+                let mut ext_idx = 0usize;
+                let mut offset: u32 = 0;
+                let prof = std::env::var_os("FREEMKV_PROFILE").is_some();
+                let mut prof_started = std::time::Instant::now();
+                let mut prof_last_dump = prof_started;
+                let mut prof_read_ns: u128 = 0;
+                let mut prof_feed_ns: u128 = 0;
+                let mut prof_send_ns: u128 = 0;
+                let mut prof_bytes: u64 = 0;
+                while ext_idx < extents.len() {
+                    if halt.as_ref().map(|h| h.is_cancelled()).unwrap_or(false) {
+                        return;
+                    }
+                    let ext = &extents[ext_idx];
+                    let remaining = ext.sector_count.saturating_sub(offset);
+                    if remaining == 0 {
+                        ext_idx += 1;
+                        offset = 0;
+                        continue;
+                    }
+                    let mut sectors = remaining.min(batch_sectors as u32) as u16;
+                    if sectors >= 3 {
+                        sectors -= sectors % 3;
+                    }
+                    let bytes = sectors as usize * 2048;
+                    if buf.len() < bytes {
+                        buf.resize(bytes, 0);
+                    }
+                    let lba = ext.start_lba + offset;
+                    let t0 = if prof {
+                        Some(std::time::Instant::now())
+                    } else {
+                        None
+                    };
+                    let n = match reader.read_sectors(lba, sectors, &mut buf[..bytes], false) {
+                        Ok(n) => n,
+                        Err(e) => {
+                            let _ = tx.send(DemuxBatch::Err(e.into()));
+                            return;
+                        }
+                    };
+                    let t1 = if prof {
+                        Some(std::time::Instant::now())
+                    } else {
+                        None
+                    };
+                    offset += sectors as u32;
+
+                    // Demux this batch immediately so the channel
+                    // carries already-parsed PesPackets, not raw
+                    // sector bytes.
+                    if let Some(ref mut d) = ts {
+                        let pkts = d.feed(&buf[..n]);
+                        let t2 = if prof {
+                            Some(std::time::Instant::now())
+                        } else {
+                            None
+                        };
+                        if !pkts.is_empty() && tx.send(DemuxBatch::Ts(pkts)).is_err() {
+                            return; // consumer dropped
+                        }
+                        let t3 = if prof {
+                            Some(std::time::Instant::now())
+                        } else {
+                            None
+                        };
+                        if prof {
+                            prof_read_ns += t1.unwrap().duration_since(t0.unwrap()).as_nanos();
+                            prof_feed_ns += t2.unwrap().duration_since(t1.unwrap()).as_nanos();
+                            prof_send_ns += t3.unwrap().duration_since(t2.unwrap()).as_nanos();
+                            prof_bytes += n as u64;
+                            let now = t3.unwrap();
+                            if now.duration_since(prof_last_dump)
+                                >= std::time::Duration::from_secs(5)
+                            {
+                                let el = now.duration_since(prof_started).as_millis().max(1);
+                                let mbps = prof_bytes as u128 * 1000 / 1_000_000 / el;
+                                eprintln!(
+                                    "[demux] elapsed={}ms in={}MB/s read={}% feed={}% send={}%",
+                                    el,
+                                    mbps,
+                                    prof_read_ns / 10_000 / el,
+                                    prof_feed_ns / 10_000 / el,
+                                    prof_send_ns / 10_000 / el,
+                                );
+                                prof_last_dump = now;
+                                prof_started = now;
+                                prof_read_ns = 0;
+                                prof_feed_ns = 0;
+                                prof_send_ns = 0;
+                                prof_bytes = 0;
+                            }
+                        }
+                    } else if let Some(ref mut d) = ps {
+                        let pkts = d.feed(&buf[..n]);
+                        if !pkts.is_empty() && tx.send(DemuxBatch::Ps(pkts)).is_err() {
+                            return;
+                        }
+                    }
+                }
+                // EOF — emit any flushed packets too.
+                if let Some(ref mut d) = ts {
+                    let tail = d.flush();
+                    if !tail.is_empty() {
+                        let _ = tx.send(DemuxBatch::Ts(tail));
+                    }
+                } else if let Some(ref mut d) = ps {
+                    let tail = d.flush();
+                    if !tail.is_empty() {
+                        let _ = tx.send(DemuxBatch::Ps(tail));
+                    }
+                }
+                // Sender drops here -> consumer sees RecvError → EOF.
+            })
+            .expect("freemkv-demux thread spawn failed");
+
+        (
+            Self {
+                handle: Some(handle),
+                producer_shell: None,
+            },
+            rx,
+        )
+    }
+
+    /// Zero-copy variant. Instead of taking a `SectorSource` and
+    /// memcpy-ing through its `read_sectors` API, this constructor
+    /// consumes the prefetch channels directly: filled buffers come
+    /// in via `prefetch_rx`, the demux thread feeds them, then
+    /// returns them to `recycle_tx` for the producer to re-fill.
+    /// Eliminates the 16 MiB memcpy per batch that the SectorSource
+    /// adapter incurred (and, with the producer-side recycling pool,
+    /// also eliminates the per-batch heap alloc / cross-thread free
+    /// that was costing 40 %+ of demux-thread time before).
+    ///
+    /// `producer_shell` is an opaque handle whose only purpose is to
+    /// outlive the demux thread and join the upstream producer when
+    /// dropped. Both
+    /// [`crate::sector::PrefetchedSectorSource::into_channels`] and
+    /// [`crate::io::byte_prefetcher::BytePrefetcher::into_channels`]
+    /// hand back a shell that fits — pass either.
+    pub fn spawn_zero_copy<S: Send + 'static>(
+        prefetch_rx: Receiver<std::io::Result<Vec<u8>>>,
+        recycle_tx: Sender<Vec<u8>>,
+        producer_shell: S,
+        halt: Option<Halt>,
+        ts: Option<super::ts::TsDemuxer>,
+        ps: Option<super::ps::PsDemuxer>,
+    ) -> (Self, Receiver<DemuxBatch>) {
+        let (tx, rx) = bounded::<DemuxBatch>(DEMUX_CHANNEL_DEPTH);
+        let mut ts = ts;
+        let mut ps = ps;
+
+        let handle = std::thread::Builder::new()
+            .name("freemkv-demux".into())
+            .spawn(move || {
+                let prof = std::env::var_os("FREEMKV_PROFILE").is_some();
+                let mut prof_started = std::time::Instant::now();
+                let mut prof_last_dump = prof_started;
+                let mut prof_read_ns: u128 = 0;
+                let mut prof_feed_ns: u128 = 0;
+                let mut prof_bytes: u64 = 0;
+                loop {
+                    if halt.as_ref().map(|h| h.is_cancelled()).unwrap_or(false) {
+                        return;
+                    }
+                    let t0 = if prof {
+                        Some(std::time::Instant::now())
+                    } else {
+                        None
+                    };
+                    let buf = match prefetch_rx.recv() {
+                        Ok(Ok(b)) => b,
+                        Ok(Err(e)) => {
+                            let _ = tx.send(DemuxBatch::Err(e));
+                            return;
+                        }
+                        Err(_) => break, // producer done → EOF
+                    };
+                    let t1 = if prof {
+                        Some(std::time::Instant::now())
+                    } else {
+                        None
+                    };
+                    let n = buf.len();
+                    if let Some(ref mut d) = ts {
+                        let pkts = d.feed(&buf);
+                        let t2 = if prof {
+                            Some(std::time::Instant::now())
+                        } else {
+                            None
+                        };
+                        // Recycle the buffer back to the producer
+                        // before pushing the demuxed packets. If the
+                        // recycle channel is closed the producer has
+                        // exited; we drop the buffer and continue.
+                        let _ = recycle_tx.send(buf);
+                        if !pkts.is_empty() && tx.send(DemuxBatch::Ts(pkts)).is_err() {
+                            return;
+                        }
+                        if prof {
+                            prof_read_ns += t1.unwrap().duration_since(t0.unwrap()).as_nanos();
+                            prof_feed_ns += t2.unwrap().duration_since(t1.unwrap()).as_nanos();
+                            prof_bytes += n as u64;
+                            let now = std::time::Instant::now();
+                            if now.duration_since(prof_last_dump)
+                                >= std::time::Duration::from_secs(5)
+                            {
+                                let el = now.duration_since(prof_started).as_millis().max(1);
+                                let mbps = prof_bytes as u128 * 1000 / 1_000_000 / el;
+                                eprintln!(
+                                    "[demux] elapsed={}ms in={}MB/s read={}% feed={}%",
+                                    el,
+                                    mbps,
+                                    prof_read_ns / 10_000 / el,
+                                    prof_feed_ns / 10_000 / el,
+                                );
+                                prof_last_dump = now;
+                                prof_started = now;
+                                prof_read_ns = 0;
+                                prof_feed_ns = 0;
+                                prof_bytes = 0;
+                            }
+                        }
+                    } else if let Some(ref mut d) = ps {
+                        let pkts = d.feed(&buf);
+                        let _ = recycle_tx.send(buf);
+                        if !pkts.is_empty() && tx.send(DemuxBatch::Ps(pkts)).is_err() {
+                            return;
+                        }
+                    } else {
+                        let _ = recycle_tx.send(buf);
+                    }
+                }
+                // Flush tail packets at EOF.
+                if let Some(ref mut d) = ts {
+                    let tail = d.flush();
+                    if !tail.is_empty() {
+                        let _ = tx.send(DemuxBatch::Ts(tail));
+                    }
+                } else if let Some(ref mut d) = ps {
+                    let tail = d.flush();
+                    if !tail.is_empty() {
+                        let _ = tx.send(DemuxBatch::Ps(tail));
+                    }
+                }
+            })
+            .expect("freemkv-demux thread spawn failed");
+
+        (
+            Self {
+                handle: Some(handle),
+                producer_shell: Some(Box::new(producer_shell)),
+            },
+            rx,
+        )
+    }
+}
+
+impl Drop for DemuxThread {
+    fn drop(&mut self) {
+        if let Some(h) = self.handle.take() {
+            let _ = h.join();
+        }
+    }
+}

src/mux/disc.rs

@@ -1,17 +1,18 @@
 //! DiscStream — read any disc (physical drive or ISO file) → PES frames.
 //!
-//! One stream type for all disc sources. The source is a SectorReader —
-//! Drive (hardware) or IsoSectorReader (file). DiscStream doesn't care.
+//! One stream type for all disc sources. The source is a SectorSource —
+//! Drive (hardware) or FileSectorSource (file). DiscStream doesn't care.
 //!
 //! Read-only. For disc→ISO (raw sector copy), use `Disc::copy()`.
 
 use crate::disc::{Disc, DiscTitle, Extent};
 use crate::drive::extract_scsi_context;
 use crate::event::{BatchSizeReason, Event, EventKind};
-use crate::sector::SectorReader;
+use crate::halt::Halt;
+use crate::sector::{DecryptingSectorSource, SectorSource};
 use std::io;
 use std::sync::Arc;
-use std::sync::atomic::{AtomicBool, Ordering};
+use std::sync::atomic::AtomicBool;
 
 /// Ramp back up to the preferred batch size after this many sectors
 /// of clean reading at the current (reduced) size. 100 MiB = 51,200 sectors.
@@ -96,12 +97,22 @@ impl AdaptiveBatch {
 
 /// Disc stream. Reads sectors from any source → PES frames.
 ///
-/// Sources: physical drive, ISO file, or any SectorReader.
+/// Sources: physical drive, ISO file, or any SectorSource.
 /// Decrypt, demux, and codec parsing happen internally.
 pub struct DiscStream {
-    reader: Box<dyn SectorReader>,
+    /// Underlying sector source wrapped in the 0.18
+    /// [`DecryptingSectorSource`] decorator. Every `read_sectors`
+    /// call yields plaintext, so `fill_extents` no longer needs an
+    /// inline `decrypt::decrypt_sectors` step. `DecryptKeys::None`
+    /// (raw / unencrypted disc) makes the decorator a pass-through.
+    reader: DecryptingSectorSource<Box<dyn SectorSource>>,
     title: DiscTitle,
     disc: Option<Disc>,
+    /// Mirror of the keys handed in at construction. The decorator
+    /// owns the cryptographic state; this field is kept for
+    /// metadata-side callers (`info()` and friends) that want to
+    /// know whether the disc was encrypted, without reaching through
+    /// the wrapper.
     decrypt_keys: crate::decrypt::DecryptKeys,
 
     // Extents to read
@@ -120,11 +131,13 @@ pub struct DiscStream {
     adaptive: AdaptiveBatch,
     pub errors: u64,
     pub skip_errors: bool,
-    /// When set and the flag is raised, fill_extents returns Err(Halted) at the
-    /// next retry boundary. Unlike skip_errors, this propagates the error up so
-    /// the rip terminates cleanly. Share the Arc with Drive::halt_flag() to get
-    /// unified Stop behavior across drive reads and sector processing.
-    halt: Option<Arc<AtomicBool>>,
+    /// When set and the token is cancelled, fill_extents returns Err(Halted)
+    /// at the next retry boundary. Unlike skip_errors, this propagates the
+    /// error up so the rip terminates cleanly. Construct with
+    /// [`DiscStream::with_halt`] (preferred) or set post-hoc via the
+    /// deprecated [`DiscStream::set_halt`] bridge — both populate this same
+    /// field and either entry point yields one source of truth.
+    halt: Option<Halt>,
     event_fn: Option<Box<dyn Fn(Event) + Send>>,
     eof: bool,
 
@@ -136,7 +149,11 @@ pub struct DiscStream {
     // a percent without a separate API call.
     bytes_total_extents: u64,
 
-    // PES output
+    // PES output — single-threaded inline demux + codec parse. The
+    // pipeline-mode mux (3-stage threaded) lives in
+    // [`super::pipelined_stream::PipelinedPesStream`]; this type is
+    // the legacy in-thread path for live-disc reads where adaptive
+    // batch retry on bad sectors lives in `fill_extents`.
     ts_demuxer: Option<super::ts::TsDemuxer>,
     ps_demuxer: Option<super::ps::PsDemuxer>,
     parsers: Vec<(u16, Box<dyn super::codec::CodecParser>)>,
@@ -147,11 +164,11 @@ pub struct DiscStream {
 impl DiscStream {
     /// Create a disc stream from any sector reader.
     ///
-    /// Works with physical drives and ISO files — both implement SectorReader.
+    /// Works with physical drives and ISO files — both implement SectorSource.
     /// The caller opens the source, scans for titles/keys, and passes them in.
     /// The stream handles demuxing, decryption, and codec parsing internally.
     pub fn new(
-        reader: Box<dyn SectorReader>,
+        reader: Box<dyn SectorSource>,
         title: DiscTitle,
         decrypt_keys: crate::decrypt::DecryptKeys,
         batch_sectors: u16,
@@ -160,6 +177,13 @@ impl DiscStream {
         let extents = title.extents.clone();
         let bytes_total_extents: u64 = extents.iter().map(|e| e.sector_count as u64 * 2048).sum();
 
+        // Debug log reader type at construction — critical for diagnosing mux reading from drive instead of ISO
+        tracing::debug!(
+            target: "mux",
+            "DiscStream constructed with reader type: {}",
+            std::any::type_name::<dyn SectorSource>()
+        );
+
         let mut pids = Vec::new();
         let mut parsers = Vec::new();
         let mut pid_to_track = Vec::new();
@@ -171,7 +195,8 @@ impl DiscStream {
             };
             pids.push(pid);
             pid_to_track.push((pid, idx));
-            parsers.push((pid, super::codec::parser_for_codec(codec, None)));
+            let is_dvd_ps = matches!(content_format, crate::disc::ContentFormat::MpegPs);
+            parsers.push((pid, super::codec::parser_for_codec(codec, None, is_dvd_ps)));
         }
 
         let mut ts_demuxer = None;
@@ -189,7 +214,11 @@ impl DiscStream {
         }
 
         Self {
-            reader,
+            // Wrap the input reader in DecryptingSectorSource so the
+            // internal fill_extents path sees plaintext bytes. For
+            // DecryptKeys::None (unencrypted / raw / test fixtures)
+            // the decorator is a pass-through.
+            reader: DecryptingSectorSource::new(reader, decrypt_keys.clone()),
             title,
             disc: None,
             decrypt_keys,
@@ -219,19 +248,39 @@ impl DiscStream {
         self.event_fn = Some(Box::new(f));
     }
 
-    /// Share a halt flag — typically from `Drive::halt_flag()`. When raised,
-    /// the next read-retry boundary inside fill_extents returns Err(Halted)
-    /// instead of continuing. Required for Stop to work during dense bad-sector
-    /// regions (where read() loops internally waiting for enough clean data to
-    /// emit a frame and would otherwise never check an external stop signal).
+    /// Constructor-time builder: attach a [`Halt`] token so that when
+    /// any clone is cancelled, the next read-retry boundary inside
+    /// `fill_extents` returns `Err(Halted)`. Required for Stop to work
+    /// during dense bad-sector regions (where the outer PES read() loop
+    /// can spend minutes inside fill_extents before emitting a frame).
+    ///
+    /// Preferred over the post-hoc [`DiscStream::set_halt`] bridge —
+    /// pass the same `Halt` clone you hand to sweep / patch / mux so
+    /// every phase observes a single Stop signal.
+    pub fn with_halt(mut self, halt: Halt) -> Self {
+        self.halt = Some(halt);
+        self
+    }
+
+    /// Bridge for callers that haven't migrated to the
+    /// [`DiscStream::with_halt`] constructor-time path yet. Wraps the
+    /// supplied `Arc<AtomicBool>` as a [`Halt`] (`Halt::from_arc`) and
+    /// stores it in the same internal slot, so a halt installed via
+    /// either entry point goes through one halt-check inside
+    /// `fill_extents`. Calling `set_halt` after `with_halt` (or vice
+    /// versa) replaces the previous token with the new one.
+    #[deprecated(
+        since = "0.18.0",
+        note = "use `DiscStream::with_halt(Halt)` at construction instead"
+    )]
     pub fn set_halt(&mut self, flag: Arc<AtomicBool>) {
-        self.halt = Some(flag);
+        self.halt = Some(Halt::from_arc(flag));
     }
 
     fn is_halted(&self) -> bool {
         self.halt
             .as_ref()
-            .map(|h| h.load(Ordering::Relaxed))
+            .map(|h| h.is_cancelled())
             .unwrap_or(false)
     }
 
@@ -241,9 +290,12 @@ impl DiscStream {
         }
     }
 
-    /// Skip decryption — return raw encrypted bytes.
+    /// Skip decryption — return raw encrypted bytes. Updates both
+    /// the metadata-side key field and the wrapped reader's keys so
+    /// subsequent `read_sectors` calls become a pass-through.
     pub fn set_raw(&mut self) {
         self.decrypt_keys = crate::decrypt::DecryptKeys::None;
+        self.reader.set_keys(crate::decrypt::DecryptKeys::None);
     }
 
     /// Get the scanned Disc (for listing all titles).
@@ -275,10 +327,19 @@ impl DiscStream {
         // this loop can spend minutes shrinking and skipping sectors; without
         // the check, Stop wouldn't take effect until the outer PES read() loop
         // finally emits a frame, which may never happen.
+
+        let start_time = std::time::Instant::now();
+
         loop {
             if self.is_halted() {
                 return Err(crate::error::Error::Halted.into());
             }
+
+            // Debug: log slow reads during mux — helps diagnose stalls
+            if cfg!(debug_assertions) && start_time.elapsed().as_secs() > 5 {
+                tracing::debug!(target: "mux", "fill_extents waiting at LBA {} ({}s elapsed, sectors={})", lba, start_time.elapsed().as_secs(), remaining);
+            }
+
             let mut sectors = remaining.min(self.adaptive.current() as u32) as u16;
             // Align to 3-sector AACS units when possible. Partial units at
             // extent boundaries are safely handled by decrypt_sectors().
@@ -347,6 +408,71 @@ impl DiscStream {
     }
 }
 
+/// Per-stage profiling state — populated only when `FREEMKV_PROFILE`
+/// is set. Dumps a percentage breakdown to stderr every
+/// [`PROFILE_INTERVAL`]. Zero overhead in normal runs (Option check
+/// is the only added cost).
+struct StageProf {
+    started: std::time::Instant,
+    last_dump: std::time::Instant,
+    fill_ns: u128,
+    feed_ns: u128,
+    consume_ns: u128,
+    bytes_in: u64,
+}
+
+const PROFILE_INTERVAL: std::time::Duration = std::time::Duration::from_secs(5);
+
+thread_local! {
+    static STAGE_PROF: std::cell::RefCell<Option<StageProf>> = const { std::cell::RefCell::new(None) };
+}
+
+fn prof_active() -> bool {
+    std::env::var_os("FREEMKV_PROFILE").is_some()
+}
+
+fn prof_tick(stage: &str, ns: u128, bytes: u64) {
+    STAGE_PROF.with(|cell| {
+        let mut slot = cell.borrow_mut();
+        if slot.is_none() {
+            if !prof_active() {
+                return;
+            }
+            let now = std::time::Instant::now();
+            *slot = Some(StageProf {
+                started: now,
+                last_dump: now,
+                fill_ns: 0,
+                feed_ns: 0,
+                consume_ns: 0,
+                bytes_in: 0,
+            });
+        }
+        let p = slot.as_mut().unwrap();
+        match stage {
+            "fill" => p.fill_ns += ns,
+            "feed" => p.feed_ns += ns,
+            "consume" => p.consume_ns += ns,
+            _ => {}
+        }
+        p.bytes_in += bytes;
+        let now = std::time::Instant::now();
+        if now.duration_since(p.last_dump) < PROFILE_INTERVAL {
+            return;
+        }
+        let elapsed_ms = now.duration_since(p.started).as_millis().max(1);
+        let fill_pct = p.fill_ns / 10_000 / elapsed_ms;
+        let feed_pct = p.feed_ns / 10_000 / elapsed_ms;
+        let consume_pct = p.consume_ns / 10_000 / elapsed_ms;
+        let mbps = p.bytes_in as u128 * 1000 / 1_000_000 / elapsed_ms;
+        eprintln!(
+            "[profile] elapsed={}ms in={}MB/s fill={}% feed={}% consume={}%",
+            elapsed_ms, mbps, fill_pct, feed_pct, consume_pct,
+        );
+        p.last_dump = now;
+    });
+}
+
 impl crate::pes::Stream for DiscStream {
     fn read(&mut self) -> io::Result<Option<crate::pes::PesFrame>> {
         if let Some(frame) = self.pending_frames.pop_front() {
@@ -358,6 +484,7 @@ impl crate::pes::Stream for DiscStream {
         }
 
         loop {
+            let t0 = std::time::Instant::now();
             if !self.fill_extents()? {
                 self.eof = true;
                 // Flush demuxer — last PES packet may still be in the assembler
@@ -415,33 +542,68 @@ impl crate::pes::Stream for DiscStream {
                         }
                     }
                 }
+                // Drain any access unit a codec parser buffered past the last
+                // PES (DTS-HD's final core+extension unit, assembled across
+                // PES boundaries).
+                let pid_to_track = &self.pid_to_track;
+                let pending = &mut self.pending_frames;
+                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() {
+                        pending.push_back(crate::pes::PesFrame::from_codec_frame(track, frame));
+                    }
+                }
                 return Ok(self.pending_frames.pop_front());
             }
 
             let bytes = self.buf_valid;
-            if let Err(e) =
-                crate::decrypt::decrypt_sectors(&mut self.read_buf[..bytes], &self.decrypt_keys, 0)
-            {
-                return Err(e.into());
-            }
+            let t1 = std::time::Instant::now();
+            prof_tick("fill", t1.duration_since(t0).as_nanos(), bytes as u64);
+            // Plaintext: the wrapped reader (DecryptingSectorSource)
+            // applied AACS / CSS in-place during fill_extents'
+            // read_sectors call. The pre-0.18 inline decrypt step
+            // lived here.
 
             if let Some(ref mut demuxer) = self.ts_demuxer {
                 let packets = demuxer.feed(&self.read_buf[..bytes]);
-                for pes in &packets {
-                    if let Some((_, track)) =
-                        self.pid_to_track.iter().find(|(pid, _)| *pid == pes.pid)
+                let t2 = std::time::Instant::now();
+                prof_tick("feed", t2.duration_since(t1).as_nanos(), 0);
+                let skip_parse = std::env::var_os("FREEMKV_SKIP_PARSE").is_some();
+                for pes in packets {
+                    if let Some((_, track)) = self
+                        .pid_to_track
+                        .iter()
+                        .find(|(pid, _)| *pid == pes.pid)
+                        .copied()
                     {
-                        if let Some((_, parser)) =
+                        if skip_parse {
+                            // Profiling escape hatch — bypass the codec
+                            // parser and pass the raw PES bytes straight
+                            // through as a single PesFrame. Lets us
+                            // attribute consumer-thread time to
+                            // "demux + framing" vs "codec parse".
+                            self.pending_frames.push_back(crate::pes::PesFrame {
+                                track,
+                                pts: pes.pts.map(super::codec::pts_to_ns).unwrap_or(0),
+                                keyframe: false,
+                                data: pes.data,
+                                duration_ns: None,
+                            });
+                        } else if let Some((_, parser)) =
                             self.parsers.iter_mut().find(|(pid, _)| *pid == pes.pid)
                         {
-                            for frame in parser.parse(pes) {
+                            for frame in parser.parse(&pes) {
                                 self.pending_frames.push_back(
-                                    crate::pes::PesFrame::from_codec_frame(*track, frame),
+                                    crate::pes::PesFrame::from_codec_frame(track, frame),
                                 );
                             }
                         }
                     }
                 }
+                let t3 = std::time::Instant::now();
+                prof_tick("consume", t3.duration_since(t2).as_nanos(), 0);
             } else if let Some(ref mut demuxer) = self.ps_demuxer {
                 let packets = demuxer.feed(&self.read_buf[..bytes]);
                 for ps in &packets {
@@ -515,6 +677,13 @@ impl crate::pes::Stream for DiscStream {
     }
 
     fn headers_ready(&self) -> bool {
+        // FREEMKV_SKIP_PARSE bypasses codec parsers entirely for
+        // bottleneck profiling, so codec_private is never populated.
+        // Pretend headers are ready immediately in that mode so the
+        // CLI loop doesn't hang waiting for them.
+        if std::env::var_os("FREEMKV_SKIP_PARSE").is_some() {
+            return true;
+        }
         for (idx, s) in self.title.streams.iter().enumerate() {
             if let crate::disc::Stream::Video(v) = s {
                 if !v.secondary && self.codec_private(idx).is_none() {
@@ -524,4 +693,145 @@ impl crate::pes::Stream for DiscStream {
         }
         true
     }
+
+    fn errors(&self) -> u64 {
+        self.errors
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    //! `DiscStream` is the only read-only `Stream` impl in tree (every
+    //! other concrete impl in `mux/*` is bidirectional or write-only).
+    //! These tests lock down a static `Send` assertion plus a
+    //! `Box<dyn Stream>` round trip exercising every method through the
+    //! trait object, so future Send-breaking edits to `DiscStream`'s
+    //! interior types fail at compile time.
+    use super::*;
+    use crate::disc::{ContentFormat, DiscTitle};
+    use crate::pes::Stream;
+
+    /// Static-assert `DiscStream: Send`. The `Stream` trait has `Send` as a
+    /// supertrait — if a future field on `DiscStream` is non-`Send` (e.g.
+    /// a `Box<dyn Read>` instead of `Box<dyn SectorSource>`), this fails
+    /// at compile time, before the runtime trait-object test below.
+    fn _assert_disc_stream_is_send() {
+        fn requires_send<T: Send>() {}
+        requires_send::<DiscStream>();
+    }
+
+    /// Trivial `SectorSource` that yields zeroed sectors. Empty title means
+    /// the demuxer produces no PES frames, so `read()` walks the extents to
+    /// EOF and returns `Ok(None)`. That's enough to exercise the trait-object
+    /// dispatch — the goal here is the bridge, not the demuxer.
+    struct ZeroReader {
+        capacity: u32,
+    }
+
+    impl crate::sector::SectorSource for ZeroReader {
+        fn read_sectors(
+            &mut self,
+            _lba: u32,
+            count: u16,
+            buf: &mut [u8],
+            _recovery: bool,
+        ) -> crate::error::Result<usize> {
+            let bytes = count as usize * 2048;
+            buf[..bytes].fill(0);
+            Ok(bytes)
+        }
+
+        fn capacity_sectors(&self) -> u32 {
+            self.capacity
+        }
+    }
+
+    fn synthetic_title(sector_count: u32) -> DiscTitle {
+        DiscTitle {
+            extents: vec![crate::disc::Extent {
+                start_lba: 0,
+                sector_count,
+            }],
+            ..DiscTitle::empty()
+        }
+    }
+
+    /// Smallest credible witness that `DiscStream` flows through `dyn Stream`:
+    /// build a `Box<dyn Stream>`, drive `read()` to EOF, exercise `info()` /
+    /// `headers_ready()` / `codec_private()` through the trait object.
+    #[test]
+    fn stream_via_dyn_object() {
+        let reader = ZeroReader { capacity: 8 };
+        let title = synthetic_title(8);
+        let stream = DiscStream::new(
+            Box::new(reader),
+            title,
+            crate::decrypt::DecryptKeys::None,
+            8,
+            ContentFormat::BdTs,
+        );
+
+        let mut src: Box<dyn Stream> = Box::new(stream);
+
+        // Empty-title fixture has no streams configured, so headers are
+        // trivially ready and codec_private() yields nothing on track 0.
+        assert!(src.headers_ready());
+        assert!(src.codec_private(0).is_none());
+        let _ = src.info();
+
+        // Drive read() to EOF through the trait object — empty-title fixture
+        // produces no frames, but the call still routes through the blanket
+        // dispatch into Stream::read.
+        let mut frames = 0usize;
+        while src.read().expect("read").is_some() {
+            frames += 1;
+            if frames > 1024 {
+                panic!("unexpected unbounded frame stream from empty title");
+            }
+        }
+        assert_eq!(frames, 0);
+    }
+
+    /// `is_halted()` must observe a cancellation signal regardless of
+    /// which entry point installed the token. The deprecated
+    /// `set_halt(Arc<AtomicBool>)` and the new `with_halt(Halt)` are
+    /// two views over one slot — flipping either bit must cause the
+    /// next `fill_extents` retry boundary to bail.
+    #[test]
+    fn halt_via_with_halt_observed_by_is_halted() {
+        let halt = Halt::new();
+        let stream = DiscStream::new(
+            Box::new(ZeroReader { capacity: 8 }),
+            synthetic_title(8),
+            crate::decrypt::DecryptKeys::None,
+            8,
+            crate::disc::ContentFormat::BdTs,
+        )
+        .with_halt(halt.clone());
+        assert!(!stream.is_halted());
+        halt.cancel();
+        assert!(
+            stream.is_halted(),
+            "with_halt token cancellation must be observed by is_halted()"
+        );
+    }
+
+    #[test]
+    fn halt_via_set_halt_bridge_observed_by_is_halted() {
+        let arc = Arc::new(AtomicBool::new(false));
+        let mut stream = DiscStream::new(
+            Box::new(ZeroReader { capacity: 8 }),
+            synthetic_title(8),
+            crate::decrypt::DecryptKeys::None,
+            8,
+            crate::disc::ContentFormat::BdTs,
+        );
+        stream.set_halt(arc.clone());
+        assert!(!stream.is_halted());
+        arc.store(true, std::sync::atomic::Ordering::Relaxed);
+        assert!(
+            stream.is_halted(),
+            "set_halt(Arc<AtomicBool>) bridge must observe Arc-side flips"
+        );
+    }
 }

src/mux/ebml.rs

@@ -264,6 +264,13 @@ pub fn read_element_header(r: &mut impl Read) -> io::Result<(u32, u64, usize)> {
 
 /// Read an unsigned integer value of `len` bytes.
 pub fn read_uint_val(r: &mut impl Read, len: usize) -> io::Result<u64> {
+    // An EBML unsigned integer is at most 8 bytes. A malformed element
+    // claiming `len > 8` would index past this stack buffer and panic
+    // (DoS on untrusted input) — reject it at the source so every caller
+    // is safe, not just the ones that pre-check.
+    if len > 8 {
+        return Err(crate::error::Error::MkvInvalid.into());
+    }
     let mut buf = [0u8; 8];
     r.read_exact(&mut buf[..len])?;
     let mut val = 0u64;
@@ -273,23 +280,33 @@ pub fn read_uint_val(r: &mut impl Read, len: usize) -> io::Result<u64> {
     Ok(val)
 }
 
-/// Read a float value (4 or 8 bytes).
+/// Read a float value. EBML floats are exactly 0, 4, or 8 bytes.
+///
+/// The previous `else` branch read a fixed 8 bytes for ANY non-4 length,
+/// so a malformed element with `len > 8` left `len - 8` unconsumed bytes
+/// (mis-read as the next EBML header → desync of the rest of the parent
+/// element) and `len < 4` over-read. Consume exactly `len` bytes and
+/// reject anything that isn't a valid float width.
 pub fn read_float_val(r: &mut impl Read, len: usize) -> io::Result<f64> {
-    if len == 4 {
-        let mut buf = [0u8; 4];
-        r.read_exact(&mut buf)?;
-        Ok(f32::from_be_bytes(buf) as f64)
-    } else {
-        let mut buf = [0u8; 8];
-        r.read_exact(&mut buf)?;
-        Ok(f64::from_be_bytes(buf))
+    match len {
+        0 => Ok(0.0),
+        4 => {
+            let mut buf = [0u8; 4];
+            r.read_exact(&mut buf)?;
+            Ok(f32::from_be_bytes(buf) as f64)
+        }
+        8 => {
+            let mut buf = [0u8; 8];
+            r.read_exact(&mut buf)?;
+            Ok(f64::from_be_bytes(buf))
+        }
+        _ => Err(crate::error::Error::MkvInvalid.into()),
     }
 }
 
 /// Read a UTF-8 string value of `len` bytes.
 pub fn read_string_val(r: &mut impl Read, len: usize) -> io::Result<String> {
-    let mut buf = vec![0u8; len];
-    r.read_exact(&mut buf)?;
+    let mut buf = read_exact_bounded(r, len)?;
     // Strip trailing nulls
     while buf.last() == Some(&0) {
         buf.pop();
@@ -299,8 +316,22 @@ pub fn read_string_val(r: &mut impl Read, len: usize) -> io::Result<String> {
 
 /// Read binary data of `len` bytes.
 pub fn read_binary_val(r: &mut impl Read, len: usize) -> io::Result<Vec<u8>> {
-    let mut buf = vec![0u8; len];
-    r.read_exact(&mut buf)?;
+    read_exact_bounded(r, len)
+}
+
+/// Read exactly `len` bytes WITHOUT trusting `len` to size the allocation.
+///
+/// `vec![0u8; len]` on an attacker-controlled EBML size would allocate
+/// gigabytes before the read fails. Instead we cap the reader to `len`
+/// and grow the buffer as bytes actually arrive: a malformed element that
+/// claims a huge length but supplies few bytes allocates only what it
+/// delivers, then errors on the short read.
+fn read_exact_bounded(r: &mut impl Read, len: usize) -> io::Result<Vec<u8>> {
+    let mut buf = Vec::new();
+    let got = r.take(len as u64).read_to_end(&mut buf)?;
+    if got != len {
+        return Err(io::ErrorKind::UnexpectedEof.into());
+    }
     Ok(buf)
 }
 
@@ -321,6 +352,12 @@ pub const EBML_DOC_TYPE_READ_VERSION: u32 = 0x4285;
 // Segment
 pub const SEGMENT: u32 = 0x1853_8067;
 
+// SeekHead
+pub const SEEK_HEAD: u32 = 0x114D_9B74;
+pub const SEEK: u32 = 0x4DBB;
+pub const SEEK_ID: u32 = 0x53AB;
+pub const SEEK_POSITION: u32 = 0x53AC;
+
 // Segment Info
 pub const INFO: u32 = 0x1549_A966;
 pub const TIMESTAMP_SCALE: u32 = 0x2A_D7B1;
@@ -356,6 +393,12 @@ pub const MATRIX_COEFFICIENTS: u32 = 0x55B1;
 pub const PRIMARIES: u32 = 0x55BB;
 pub const RANGE: u32 = 0x55B9;
 
+// Dolby Vision — BlockAdditionMapping carries the DOVIDecoderConfigurationRecord
+// (dvcC) so players / mediainfo recognise the track as Dolby Vision.
+pub const BLOCK_ADDITION_MAPPING: u32 = 0x41E4;
+pub const BLOCK_ADD_ID_TYPE: u32 = 0x41E7;
+pub const BLOCK_ADD_ID_EXTRA_DATA: u32 = 0x41ED;
+
 // Audio
 pub const AUDIO: u32 = 0xE1;
 pub const SAMPLING_FREQUENCY: u32 = 0xB5;
@@ -366,6 +409,9 @@ pub const BIT_DEPTH: u32 = 0x6264;
 pub const CLUSTER: u32 = 0x1F43_B675;
 pub const CLUSTER_TIMESTAMP: u32 = 0xE7;
 pub const SIMPLE_BLOCK: u32 = 0xA3;
+pub const BLOCK_GROUP: u32 = 0xA0;
+pub const BLOCK: u32 = 0xA1;
+pub const BLOCK_DURATION: u32 = 0x9B;
 
 // Cues
 pub const CUES: u32 = 0x1C53_BB6B;

src/mux/fmp4/mod.rs

@@ -0,0 +1,404 @@
+//! Fragmented MP4 muxer — **stub** for Phase 3.
+//!
+//! Goal: ISO/IEC 14496-12 fragmented MP4 (`ftyp` + `moov` init segment,
+//! then a sequence of `moof+mdat` media fragments) targeting a
+//! [`SequentialSink`](crate::io::sink::SequentialSink). DASH-friendly,
+//! no Cues backpatch.
+//!
+//! Status (v0.21.0 Phase 3): **STUB**. We ship the init segment
+//! (`ftyp` + a minimal HEVC `moov` skeleton with one video track) so
+//! the muxer's shape and call site are validated, but media fragments
+//! are NOT yet emitted — calls to [`Fmp4Mux::write_video`] currently
+//! accumulate frames into an internal buffer and discard them on
+//! [`Fmp4Mux::finish`].
+//!
+//! ## What's TODO (tracked in Phase 4 / v0.22.0 scope)
+//!
+//! - `moof` box: `mfhd` (sequence_number) + `traf` (`tfhd` + `tfdt`
+//!   + `trun` with sample sizes, durations, flags, composition offsets).
+//! - `mdat` box: concatenated sample data.
+//! - Fragment cadence: one fragment per GOP or every N seconds,
+//!   whichever comes first.
+//! - HEVC `hvcC` box inside `moov.trak.mdia.minf.stbl.stsd` so the
+//!   init segment is self-describing.
+//! - Sample-flags computation (sync vs. delta, depends_on, etc.).
+//! - Edit lists / fragment_duration for accurate seeking.
+//!
+//! Reference: ISO/IEC 14496-12 §8 (Movie Fragments).
+
+use std::io::{self, Write};
+
+// Box type literals — four-character codes per ISO/IEC 14496-12 §4.2.
+
+const FTYP: [u8; 4] = *b"ftyp";
+const MOOV: [u8; 4] = *b"moov";
+const MVHD: [u8; 4] = *b"mvhd";
+const TRAK: [u8; 4] = *b"trak";
+const TKHD: [u8; 4] = *b"tkhd";
+const MDIA: [u8; 4] = *b"mdia";
+const MDHD: [u8; 4] = *b"mdhd";
+const HDLR: [u8; 4] = *b"hdlr";
+const MINF: [u8; 4] = *b"minf";
+const VMHD: [u8; 4] = *b"vmhd";
+const DINF: [u8; 4] = *b"dinf";
+const DREF: [u8; 4] = *b"dref";
+const URL_: [u8; 4] = *b"url ";
+const STBL: [u8; 4] = *b"stbl";
+const STSD: [u8; 4] = *b"stsd";
+const STTS: [u8; 4] = *b"stts";
+const STSC: [u8; 4] = *b"stsc";
+const STSZ: [u8; 4] = *b"stsz";
+const STCO: [u8; 4] = *b"stco";
+const MVEX: [u8; 4] = *b"mvex";
+const TREX: [u8; 4] = *b"trex";
+
+/// Default movie timescale — 90 kHz lines up with MPEG-TS PTS and the
+/// HEVC SPS `vui_time_scale` for film content, simplifying the math
+/// when fragment emission lands.
+const MOVIE_TIMESCALE: u32 = 90_000;
+/// Video track ID. fMP4 init segments conventionally use track_ID=1
+/// for the primary video track; a single-track DASH representation has
+/// no reason to deviate.
+const VIDEO_TRACK_ID: u32 = 1;
+
+/// Fragmented MP4 muxer — stub.
+///
+/// See the module-level doc comment for what is and isn't shipped in
+/// this stub.
+pub struct Fmp4Mux<W: Write> {
+    writer: W,
+    header_written: bool,
+    /// Pending frames — held for the future fragment-emit path. The
+    /// stub drops these on `finish` but keeping them around lets the
+    /// post-stub work re-attach without changing the public API.
+    pending: Vec<PendingSample>,
+    /// hvcC bytes, if provided. Embedded in the `moov.…stsd.hvc1.hvcC`
+    /// box once that path lands.
+    #[allow(dead_code)]
+    codec_private: Option<Vec<u8>>,
+}
+
+struct PendingSample {
+    #[allow(dead_code)]
+    pts_ns: i64,
+    #[allow(dead_code)]
+    keyframe: bool,
+    #[allow(dead_code)]
+    data: Vec<u8>,
+}
+
+impl<W: Write> Fmp4Mux<W> {
+    pub fn new(writer: W) -> Self {
+        Self {
+            writer,
+            header_written: false,
+            pending: Vec::new(),
+            codec_private: None,
+        }
+    }
+
+    /// Provide the `HEVCDecoderConfigurationRecord` for the video track.
+    /// The stub stores it but doesn't yet embed it in `moov` — that's
+    /// part of the post-stub work.
+    pub fn set_video_codec_private(&mut self, hvcc: Vec<u8>) {
+        self.codec_private = Some(hvcc);
+    }
+
+    /// Write one video PES frame.
+    ///
+    /// **Stub behaviour:** the first call emits the init segment
+    /// (`ftyp` + `moov`) so any consumer that just wants the shape can
+    /// receive it. Subsequent calls accumulate frames in memory for
+    /// the future fragmenting path; **no media bytes are written yet**.
+    pub fn write_video(&mut self, pts_ns: i64, keyframe: bool, data: &[u8]) -> io::Result<()> {
+        if !self.header_written {
+            self.write_init_segment()?;
+            self.header_written = true;
+        }
+        // TODO(0.22.0): emit one `moof+mdat` per GOP. For now stash the
+        // frame so the future patch can hot-wire emission without API
+        // churn.
+        self.pending.push(PendingSample {
+            pts_ns,
+            keyframe,
+            data: data.to_vec(),
+        });
+        Ok(())
+    }
+
+    /// Flush. The stub additionally drops accumulated `pending` frames.
+    pub fn finish(&mut self) -> io::Result<()> {
+        // TODO(0.22.0): emit final fragment from pending; today the
+        // stub just clears the buffer to release memory.
+        self.pending.clear();
+        self.writer.flush()
+    }
+
+    fn write_init_segment(&mut self) -> io::Result<()> {
+        let ftyp = build_ftyp();
+        let moov = build_moov();
+        self.writer.write_all(&ftyp)?;
+        self.writer.write_all(&moov)?;
+        Ok(())
+    }
+}
+
+/// Build the `ftyp` box. `major_brand = "iso6"`, `minor_version = 1`,
+/// compatible brands `iso6 dash msdh hvc1` — the same conservative set
+/// shaka-packager uses for HEVC-in-fMP4 outputs.
+fn build_ftyp() -> Vec<u8> {
+    let mut body = Vec::new();
+    body.extend_from_slice(b"iso6");
+    body.extend_from_slice(&1u32.to_be_bytes());
+    body.extend_from_slice(b"iso6");
+    body.extend_from_slice(b"dash");
+    body.extend_from_slice(b"msdh");
+    body.extend_from_slice(b"hvc1");
+    wrap_box(&FTYP, &body)
+}
+
+/// Build the `moov` box — minimal skeleton. Single video trak, no
+/// hvcC inside stsd yet (TODO: full hvc1 sample entry).
+fn build_moov() -> Vec<u8> {
+    let mvhd = build_mvhd();
+    let trak = build_video_trak();
+    let mvex = build_mvex();
+    let mut body = Vec::new();
+    body.extend_from_slice(&mvhd);
+    body.extend_from_slice(&trak);
+    body.extend_from_slice(&mvex);
+    wrap_box(&MOOV, &body)
+}
+
+fn build_mvhd() -> Vec<u8> {
+    // Version 0, 100 bytes total body. Fields per ISO/IEC 14496-12 §8.2.2.
+    let mut body = Vec::new();
+    body.extend_from_slice(&[0, 0, 0, 0]); // version + flags
+    body.extend_from_slice(&0u32.to_be_bytes()); // creation_time
+    body.extend_from_slice(&0u32.to_be_bytes()); // modification_time
+    body.extend_from_slice(&MOVIE_TIMESCALE.to_be_bytes());
+    body.extend_from_slice(&0u32.to_be_bytes()); // duration = 0 (fragmented)
+    body.extend_from_slice(&0x0001_0000u32.to_be_bytes()); // rate 1.0
+    body.extend_from_slice(&0x0100u16.to_be_bytes()); // volume 1.0
+    body.extend_from_slice(&[0u8; 2]); // reserved
+    body.extend_from_slice(&[0u8; 8]); // reserved
+    // 3x3 identity transformation matrix in 16.16 fixed point.
+    for v in [0x1_0000u32, 0, 0, 0, 0x1_0000, 0, 0, 0, 0x4000_0000] {
+        body.extend_from_slice(&v.to_be_bytes());
+    }
+    body.extend_from_slice(&[0u8; 24]); // pre_defined[6]
+    body.extend_from_slice(&2u32.to_be_bytes()); // next_track_ID (1 reserved for video)
+    wrap_box(&MVHD, &body)
+}
+
+fn build_video_trak() -> Vec<u8> {
+    let tkhd = build_tkhd();
+    let mdia = build_mdia();
+    let mut body = Vec::new();
+    body.extend_from_slice(&tkhd);
+    body.extend_from_slice(&mdia);
+    wrap_box(&TRAK, &body)
+}
+
+fn build_tkhd() -> Vec<u8> {
+    let mut body = Vec::new();
+    // version=0 | flags=0x000007 (track_enabled | in_movie | in_preview)
+    body.extend_from_slice(&[0, 0, 0, 7]);
+    body.extend_from_slice(&0u32.to_be_bytes()); // creation_time
+    body.extend_from_slice(&0u32.to_be_bytes()); // modification_time
+    body.extend_from_slice(&VIDEO_TRACK_ID.to_be_bytes());
+    body.extend_from_slice(&[0u8; 4]); // reserved
+    body.extend_from_slice(&0u32.to_be_bytes()); // duration
+    body.extend_from_slice(&[0u8; 8]); // reserved
+    body.extend_from_slice(&0u16.to_be_bytes()); // layer
+    body.extend_from_slice(&0u16.to_be_bytes()); // alternate_group
+    body.extend_from_slice(&0u16.to_be_bytes()); // volume (video=0)
+    body.extend_from_slice(&[0u8; 2]); // reserved
+    // 3x3 identity matrix.
+    for v in [0x1_0000u32, 0, 0, 0, 0x1_0000, 0, 0, 0, 0x4000_0000] {
+        body.extend_from_slice(&v.to_be_bytes());
+    }
+    // width / height in 16.16 fixed point — placeholder 1920x1080.
+    body.extend_from_slice(&(1920u32 << 16).to_be_bytes());
+    body.extend_from_slice(&(1080u32 << 16).to_be_bytes());
+    wrap_box(&TKHD, &body)
+}
+
+fn build_mdia() -> Vec<u8> {
+    let mdhd = build_mdhd();
+    let hdlr = build_hdlr_vide();
+    let minf = build_minf();
+    let mut body = Vec::new();
+    body.extend_from_slice(&mdhd);
+    body.extend_from_slice(&hdlr);
+    body.extend_from_slice(&minf);
+    wrap_box(&MDIA, &body)
+}
+
+fn build_mdhd() -> Vec<u8> {
+    let mut body = Vec::new();
+    body.extend_from_slice(&[0, 0, 0, 0]); // version + flags
+    body.extend_from_slice(&0u32.to_be_bytes()); // creation_time
+    body.extend_from_slice(&0u32.to_be_bytes()); // modification_time
+    body.extend_from_slice(&MOVIE_TIMESCALE.to_be_bytes());
+    body.extend_from_slice(&0u32.to_be_bytes()); // duration
+    // language: 'und' in 5-bit-per-char ISO 639-2 packed (bit 15 = 0).
+    body.extend_from_slice(&[0x55, 0xC4]);
+    body.extend_from_slice(&0u16.to_be_bytes()); // pre_defined
+    wrap_box(&MDHD, &body)
+}
+
+fn build_hdlr_vide() -> Vec<u8> {
+    let mut body = Vec::new();
+    body.extend_from_slice(&[0, 0, 0, 0]); // version + flags
+    body.extend_from_slice(&0u32.to_be_bytes()); // pre_defined
+    body.extend_from_slice(b"vide");
+    body.extend_from_slice(&[0u8; 12]); // reserved
+    body.extend_from_slice(b"VideoHandler\0");
+    wrap_box(&HDLR, &body)
+}
+
+fn build_minf() -> Vec<u8> {
+    let vmhd = build_vmhd();
+    let dinf = build_dinf();
+    let stbl = build_stbl();
+    let mut body = Vec::new();
+    body.extend_from_slice(&vmhd);
+    body.extend_from_slice(&dinf);
+    body.extend_from_slice(&stbl);
+    wrap_box(&MINF, &body)
+}
+
+fn build_vmhd() -> Vec<u8> {
+    let mut body = Vec::new();
+    body.extend_from_slice(&[0, 0, 0, 1]); // version + flags=1
+    body.extend_from_slice(&0u16.to_be_bytes()); // graphicsmode
+    body.extend_from_slice(&[0u8; 6]); // opcolor
+    wrap_box(&VMHD, &body)
+}
+
+fn build_dinf() -> Vec<u8> {
+    let mut dref_body = Vec::new();
+    dref_body.extend_from_slice(&[0, 0, 0, 0]);
+    dref_body.extend_from_slice(&1u32.to_be_bytes()); // entry_count
+    // url with flags=1 (self-contained) and zero name.
+    let url_body = [0u8, 0, 0, 1];
+    dref_body.extend_from_slice(&wrap_box(&URL_, &url_body));
+    let dref = wrap_box(&DREF, &dref_body);
+    wrap_box(&DINF, &dref)
+}
+
+fn build_stbl() -> Vec<u8> {
+    // Stub stsd: empty sample description (zero entries). Replace with
+    // hvc1+hvcC once the fragmenting path lands so the init segment is
+    // actually decodable.
+    let mut stsd_body = Vec::new();
+    stsd_body.extend_from_slice(&[0, 0, 0, 0]);
+    stsd_body.extend_from_slice(&0u32.to_be_bytes()); // entry_count
+    let stsd = wrap_box(&STSD, &stsd_body);
+
+    // Empty stts/stsc/stsz/stco — fragmented init has no samples here.
+    let stts = wrap_box(&STTS, &[0, 0, 0, 0, 0, 0, 0, 0]); // version+flags, count=0
+    let stsc = wrap_box(&STSC, &[0, 0, 0, 0, 0, 0, 0, 0]);
+    let stsz = wrap_box(
+        &STSZ,
+        &[0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0], // version+flags, sample_size=0, count=0
+    );
+    let stco = wrap_box(&STCO, &[0, 0, 0, 0, 0, 0, 0, 0]);
+
+    let mut body = Vec::new();
+    body.extend_from_slice(&stsd);
+    body.extend_from_slice(&stts);
+    body.extend_from_slice(&stsc);
+    body.extend_from_slice(&stsz);
+    body.extend_from_slice(&stco);
+    wrap_box(&STBL, &body)
+}
+
+fn build_mvex() -> Vec<u8> {
+    // trex: track_ID=1, default_sample_description_index=1, others=0.
+    let mut trex_body = Vec::new();
+    trex_body.extend_from_slice(&[0, 0, 0, 0]); // version + flags
+    trex_body.extend_from_slice(&VIDEO_TRACK_ID.to_be_bytes());
+    trex_body.extend_from_slice(&1u32.to_be_bytes()); // default_sample_description_index
+    trex_body.extend_from_slice(&0u32.to_be_bytes()); // default_sample_duration
+    trex_body.extend_from_slice(&0u32.to_be_bytes()); // default_sample_size
+    trex_body.extend_from_slice(&0u32.to_be_bytes()); // default_sample_flags
+    let trex = wrap_box(&TREX, &trex_body);
+    wrap_box(&MVEX, &trex)
+}
+
+/// Wrap a box body in `[size:u32-BE][type:4]`. Suitable for any body
+/// that fits in u32; oversized boxes (size > 4 GiB) need the 64-bit
+/// large-size extension which we don't generate in the stub.
+fn wrap_box(box_type: &[u8; 4], body: &[u8]) -> Vec<u8> {
+    let size = (body.len() + 8) as u32;
+    let mut out = Vec::with_capacity(body.len() + 8);
+    out.extend_from_slice(&size.to_be_bytes());
+    out.extend_from_slice(box_type);
+    out.extend_from_slice(body);
+    out
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    /// Decode the first box's size + type from `buf`.
+    fn read_box_header(buf: &[u8]) -> (u32, [u8; 4]) {
+        let size = u32::from_be_bytes([buf[0], buf[1], buf[2], buf[3]]);
+        let bt = [buf[4], buf[5], buf[6], buf[7]];
+        (size, bt)
+    }
+
+    #[test]
+    fn init_segment_starts_with_ftyp_then_moov() {
+        let mut sink: Vec<u8> = Vec::new();
+        let mut mux = Fmp4Mux::new(&mut sink);
+        // Trigger init emission via a single (stubbed) write.
+        mux.write_video(0, true, &[0x00, 0x00, 0x00, 0x01, 0x40])
+            .unwrap();
+        mux.finish().unwrap();
+        drop(mux);
+
+        let (ftyp_size, ftyp_type) = read_box_header(&sink);
+        assert_eq!(&ftyp_type, b"ftyp");
+        assert!(ftyp_size >= 24, "ftyp too small: {ftyp_size}");
+
+        let (moov_size, moov_type) = read_box_header(&sink[ftyp_size as usize..]);
+        assert_eq!(&moov_type, b"moov");
+        assert!(moov_size > 100, "moov skeleton too small: {moov_size}");
+
+        // Stub guarantee: no media bytes after the init segment.
+        let total = ftyp_size as usize + moov_size as usize;
+        assert_eq!(sink.len(), total, "stub leaked media bytes past moov");
+    }
+
+    #[test]
+    fn moov_contains_trak_mvex() {
+        let mut sink: Vec<u8> = Vec::new();
+        let mut mux = Fmp4Mux::new(&mut sink);
+        mux.write_video(0, true, &[]).unwrap();
+        mux.finish().unwrap();
+        drop(sink);
+
+        // Re-emit into a fresh buffer for parsing.
+        let mut buf: Vec<u8> = Vec::new();
+        let mut mux2 = Fmp4Mux::new(&mut buf);
+        mux2.write_video(0, true, &[]).unwrap();
+        mux2.finish().unwrap();
+        drop(mux2);
+
+        // Find moov payload start.
+        let (ftyp_size, _) = read_box_header(&buf);
+        let moov_start = ftyp_size as usize;
+        let (moov_size, _) = read_box_header(&buf[moov_start..]);
+        let moov_payload = &buf[moov_start + 8..moov_start + moov_size as usize];
+
+        // Scan for the trak and mvex four-CC anywhere in the moov payload.
+        let has_trak = moov_payload.windows(4).any(|w| w == b"trak");
+        let has_mvex = moov_payload.windows(4).any(|w| w == b"mvex");
+        assert!(has_trak, "moov missing trak");
+        assert!(has_mvex, "moov missing mvex");
+    }
+}

src/mux/hevc/mod.rs

@@ -0,0 +1,279 @@
+//! HEVC (H.265) elementary stream muxer — Annex B byte stream.
+//!
+//! Consumes [`PesFrame`](crate::pes::PesFrame)s for a single video track
+//! and writes them as a raw `.hevc` / `.h265` Annex B byte stream:
+//! `00 00 00 01 | NAL_unit | 00 00 00 01 | NAL_unit | …` with no
+//! container framing.
+//!
+//! On the first frame the muxer emits the codec_private's VPS, SPS, PPS
+//! (parsed from a `HEVCDecoderConfigurationRecord` in
+//! `length-prefixed-in-hvcC` form), then converts each PES frame's
+//! length-prefixed NAL units to Annex B and writes them.
+//!
+//! Sequential-only — no Cues, no backpatch. Target sink is any
+//! [`SequentialSink`](crate::io::sink::SequentialSink): file, socket,
+//! pipe, anything `Write + Send`.
+
+use std::io::{self, Write};
+
+/// Annex B 4-byte start code.
+pub(crate) const START_CODE: [u8; 4] = [0x00, 0x00, 0x00, 0x01];
+
+/// HEVC NAL unit type bits live in `(byte0 >> 1) & 0x3F` in Annex B.
+/// We don't filter NAL types here — the muxer is format-only — but we
+/// keep the constant as documentation of the field layout.
+#[allow(dead_code)]
+const HEVC_NAL_TYPE_MASK: u8 = 0x3F;
+
+/// Streaming HEVC Annex B muxer.
+///
+/// One instance per output stream. Tracks whether parameter sets have
+/// already been emitted so they're written exactly once at the head of
+/// the stream, mirroring the convention used by `ffmpeg -c:v copy -f
+/// hevc`.
+pub struct HevcMux<W: Write> {
+    writer: W,
+    /// `HEVCDecoderConfigurationRecord` payload (hvcC). Parsed lazily
+    /// on the first `write_frame` so callers can set it after
+    /// construction but before the first frame.
+    codec_private: Option<Vec<u8>>,
+    /// Set once VPS/SPS/PPS have been written to the stream. Subsequent
+    /// frames write only their own NAL units.
+    params_written: bool,
+}
+
+impl<W: Write> HevcMux<W> {
+    /// Construct over `writer`. The muxer does not impose any extra
+    /// buffering of its own — the sink owns its write buffering policy
+    /// (see [`LocalFileSink`](crate::io::sink::LocalFileSink) and
+    /// [`SocketSink`](crate::io::sink::SocketSink)).
+    pub fn new(writer: W) -> Self {
+        Self {
+            writer,
+            codec_private: None,
+            params_written: false,
+        }
+    }
+
+    /// Provide the `HEVCDecoderConfigurationRecord` (hvcC) so the muxer
+    /// can prepend VPS/SPS/PPS Annex B NALs at stream start. Optional —
+    /// if the PES frames already carry inline parameter sets (some
+    /// upstream demuxers do this), skipping this call is fine.
+    pub fn set_codec_private(&mut self, data: Vec<u8>) {
+        self.codec_private = Some(data);
+    }
+
+    /// Write one PES frame (= one access unit) as Annex B NAL units.
+    ///
+    /// Input may be either:
+    ///   - Length-prefixed: `[u32-BE len][NAL bytes]` repeated. This is
+    ///     the form emitted by libfreemkv's HEVC parser (the MKV-native
+    ///     layout). Converted to Annex B.
+    ///   - Already Annex B: bytes containing `00 00 00 01` start codes
+    ///     anywhere in the buffer. Passed through unchanged.
+    ///
+    /// `_pts_ns` is accepted for symmetry with other muxers but ignored
+    /// — Annex B has no timing layer.
+    pub fn write_frame(&mut self, _pts_ns: i64, data: &[u8]) -> io::Result<()> {
+        if !self.params_written {
+            if let Some(cp) = &self.codec_private {
+                if let Some(params) = hvcc_to_annex_b(cp) {
+                    self.writer.write_all(&params)?;
+                }
+            }
+            self.params_written = true;
+        }
+        let annex_b = length_prefixed_to_annex_b(data);
+        self.writer.write_all(&annex_b)
+    }
+
+    /// Flush the underlying writer. No trailer NAL is needed — an Annex
+    /// B stream ends whenever the file/socket ends.
+    pub fn finish(&mut self) -> io::Result<()> {
+        self.writer.flush()
+    }
+}
+
+/// Convert a `HEVCDecoderConfigurationRecord` (hvcC) into Annex B NAL
+/// units. Returns `Some(bytes)` if at least one NAL was extracted, else
+/// `None`.
+///
+/// Layout (per ISO/IEC 14496-15 §8.3.3.1.2):
+///   - 22-byte fixed header
+///   - byte 22 = `numOfArrays`
+///   - each array: `array_completeness:1 | reserved:1 | NAL_unit_type:6`,
+///     `numNalus:u16-BE`, then `numNalus` × `(nalUnitLength:u16-BE +
+///     NAL bytes)`.
+///
+/// We don't filter on NAL type — VPS (32), SPS (33), PPS (34), and any
+/// SEI arrays included in hvcC all get the same Annex B treatment.
+fn hvcc_to_annex_b(hvcc: &[u8]) -> Option<Vec<u8>> {
+    if hvcc.len() < 23 {
+        return None;
+    }
+    let num_arrays = hvcc[22] as usize;
+    let mut out = Vec::new();
+    let mut offset = 23;
+    for _ in 0..num_arrays {
+        if offset + 3 > hvcc.len() {
+            break;
+        }
+        offset += 1; // array_completeness + nal_type byte
+        let num_nalus = u16::from_be_bytes([hvcc[offset], hvcc[offset + 1]]) as usize;
+        offset += 2;
+        for _ in 0..num_nalus {
+            if offset + 2 > hvcc.len() {
+                break;
+            }
+            let nal_len = u16::from_be_bytes([hvcc[offset], hvcc[offset + 1]]) as usize;
+            offset += 2;
+            if offset + nal_len > hvcc.len() {
+                break;
+            }
+            out.extend_from_slice(&START_CODE);
+            out.extend_from_slice(&hvcc[offset..offset + nal_len]);
+            offset += nal_len;
+        }
+    }
+    if out.is_empty() { None } else { Some(out) }
+}
+
+/// Convert length-prefixed NAL units (`[u32-BE len][NAL]` repeated) to
+/// Annex B (`00 00 00 01 [NAL]` repeated).
+///
+/// If the input doesn't parse as length-prefixed (no valid lengths
+/// extracted), it's returned unchanged on the assumption that it's
+/// already Annex B — some upstream paths (raw HEVC ES from disc) pass
+/// Annex B straight through the PES layer.
+pub(crate) fn length_prefixed_to_annex_b(data: &[u8]) -> Vec<u8> {
+    let mut out = Vec::with_capacity(data.len() + (data.len() / 32));
+    let mut offset = 0;
+    while offset + 4 <= data.len() {
+        let len = u32::from_be_bytes([
+            data[offset],
+            data[offset + 1],
+            data[offset + 2],
+            data[offset + 3],
+        ]) as usize;
+        offset += 4;
+        if offset + len > data.len() {
+            // Mid-NAL truncation — fall through to the pass-through path
+            // rather than emitting a half-NAL.
+            return data.to_vec();
+        }
+        out.extend_from_slice(&START_CODE);
+        out.extend_from_slice(&data[offset..offset + len]);
+        offset += len;
+    }
+    if out.is_empty() && !data.is_empty() {
+        // No length prefixes found — input is likely already Annex B.
+        return data.to_vec();
+    }
+    out
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn length_prefixed_converts_to_annex_b() {
+        // Two NALs: [3-byte payload AA BB CC] and [2-byte payload DD EE].
+        let mut buf = Vec::new();
+        buf.extend_from_slice(&3u32.to_be_bytes());
+        buf.extend_from_slice(&[0xAA, 0xBB, 0xCC]);
+        buf.extend_from_slice(&2u32.to_be_bytes());
+        buf.extend_from_slice(&[0xDD, 0xEE]);
+
+        let got = length_prefixed_to_annex_b(&buf);
+        let want = [
+            0x00, 0x00, 0x00, 0x01, 0xAA, 0xBB, 0xCC, // first NAL
+            0x00, 0x00, 0x00, 0x01, 0xDD, 0xEE, // second NAL
+        ];
+        assert_eq!(&got[..], &want[..]);
+    }
+
+    #[test]
+    fn already_annex_b_passes_through_when_no_lengths_match() {
+        // A buffer < 4 bytes can't parse a length prefix at all →
+        // pass-through path triggers.
+        let raw = [0xAA, 0xBB, 0xCC];
+        let got = length_prefixed_to_annex_b(&raw);
+        assert_eq!(&got[..], &raw[..]);
+    }
+
+    #[test]
+    fn mid_nal_truncation_returns_original() {
+        // `[u32-BE 100][only 3 bytes]` — length prefix claims 100 bytes
+        // but the input only has 3 after the prefix. We treat that as
+        // malformed and pass the original buffer through so receivers
+        // can attempt their own recovery.
+        let mut raw = Vec::new();
+        raw.extend_from_slice(&100u32.to_be_bytes());
+        raw.extend_from_slice(&[0xAA, 0xBB, 0xCC]);
+        let got = length_prefixed_to_annex_b(&raw);
+        assert_eq!(&got[..], &raw[..]);
+    }
+
+    #[test]
+    fn hvcc_extracts_vps_sps_pps() {
+        // Build a minimal-but-valid hvcC: 22-byte header, then 3 arrays
+        // (VPS / SPS / PPS), each with 1 NAL of a 4-byte payload that
+        // we can spot in the output.
+        let mut hvcc = vec![0u8; 22];
+        hvcc.push(3); // numOfArrays
+        for (nal_type, payload) in [
+            (32u8, [0x40, 0x01, 0x0C, 0x01]),
+            (33, [0x42, 0x01, 0x01, 0x01]),
+            (34, [0x44, 0x01, 0xC1, 0x72]),
+        ] {
+            hvcc.push(nal_type & 0x3F);
+            hvcc.extend_from_slice(&1u16.to_be_bytes()); // numNalus
+            hvcc.extend_from_slice(&(payload.len() as u16).to_be_bytes());
+            hvcc.extend_from_slice(&payload);
+        }
+
+        let annex_b = hvcc_to_annex_b(&hvcc).expect("at least one NAL");
+        // Three NALs × (4-byte start + 4-byte payload) = 24 bytes.
+        assert_eq!(annex_b.len(), 24);
+        assert_eq!(&annex_b[..4], &START_CODE);
+        assert_eq!(&annex_b[8..12], &START_CODE);
+        assert_eq!(&annex_b[16..20], &START_CODE);
+        assert_eq!(annex_b[4], 0x40); // VPS first byte
+        assert_eq!(annex_b[12], 0x42); // SPS first byte
+        assert_eq!(annex_b[20], 0x44); // PPS first byte
+    }
+
+    #[test]
+    fn mux_writes_params_then_frames() {
+        // Build hvcC with one SPS to verify params-once semantics.
+        let mut hvcc = vec![0u8; 22];
+        hvcc.push(1);
+        hvcc.push(33);
+        hvcc.extend_from_slice(&1u16.to_be_bytes());
+        hvcc.extend_from_slice(&3u16.to_be_bytes());
+        hvcc.extend_from_slice(&[0x42, 0x01, 0x01]);
+
+        let mut frame_data = Vec::new();
+        frame_data.extend_from_slice(&2u32.to_be_bytes());
+        frame_data.extend_from_slice(&[0xAA, 0xBB]);
+
+        let mut sink: Vec<u8> = Vec::new();
+        let mut mux = HevcMux::new(&mut sink);
+        mux.set_codec_private(hvcc);
+        mux.write_frame(0, &frame_data).unwrap();
+        // Second frame — no SPS re-emission.
+        mux.write_frame(40_000_000, &frame_data).unwrap();
+        mux.finish().unwrap();
+
+        // SPS NAL (7 bytes) + 2× frame NAL (6 bytes) = 19 bytes.
+        assert_eq!(sink.len(), 7 + 6 + 6);
+        // Start codes at offsets 0 (SPS), 7 (frame1), 13 (frame2).
+        assert_eq!(&sink[0..4], &START_CODE);
+        assert_eq!(&sink[7..11], &START_CODE);
+        assert_eq!(&sink[13..17], &START_CODE);
+        assert_eq!(sink[4], 0x42);
+        assert_eq!(sink[11], 0xAA);
+        assert_eq!(sink[17], 0xAA);
+    }
+}

src/mux/iso.rs

@@ -1,101 +0,0 @@
-//! ISO sector reader — file-backed SectorReader for Blu-ray ISO images.
-//!
-//! An ISO is a flat image of 2048-byte sectors. Sector N starts at byte offset N * 2048.
-//! Used by DiscStream::open_iso() and Disc::scan_image().
-
-use crate::error::{Error, Result};
-use crate::sector::SectorReader;
-use std::fs::File;
-use std::io::{Read, Seek, SeekFrom};
-use std::path::Path;
-
-const SECTOR_SIZE: u64 = 2048;
-
-/// File-backed sector reader for ISO images.
-pub struct IsoSectorReader {
-    file: File,
-    capacity: u32,
-}
-
-impl IsoSectorReader {
-    pub fn open(path: &str) -> std::io::Result<Self> {
-        let file = File::open(Path::new(path))?;
-        let size = file.metadata()?.len();
-        let sectors = size / SECTOR_SIZE;
-        if sectors > u32::MAX as u64 {
-            return Err(crate::error::Error::IsoTooLarge {
-                path: path.to_string(),
-            }
-            .into());
-        }
-        let capacity = sectors as u32;
-        Ok(Self { file, capacity })
-    }
-
-    pub fn capacity(&self) -> u32 {
-        self.capacity
-    }
-}
-
-impl SectorReader for IsoSectorReader {
-    fn read_sectors(
-        &mut self,
-        lba: u32,
-        count: u16,
-        buf: &mut [u8],
-        _recovery: bool,
-    ) -> Result<usize> {
-        let bytes = count as usize * SECTOR_SIZE as usize;
-        self.file
-            .seek(SeekFrom::Start(lba as u64 * SECTOR_SIZE))
-            .map_err(|e| Error::IoError { source: e })?;
-        self.file
-            .read_exact(&mut buf[..bytes])
-            .map_err(|e| Error::IoError { source: e })?;
-        Ok(bytes)
-    }
-}
-
-#[cfg(test)]
-mod tests {
-    use super::*;
-
-    #[test]
-    fn iso_reader_read_sectors() {
-        let mut data = vec![0u8; 4 * SECTOR_SIZE as usize];
-        for i in 0..4u8 {
-            let offset = i as usize * SECTOR_SIZE as usize;
-            data[offset] = i + 1;
-            data[offset + 2047] = i + 100;
-        }
-
-        let dir = std::env::temp_dir().join("freemkv_test_iso_read");
-        std::fs::write(&dir, &data).unwrap();
-
-        let mut reader = IsoSectorReader::open(dir.to_str().unwrap()).unwrap();
-        assert_eq!(reader.capacity(), 4);
-
-        let mut buf = [0u8; 2048];
-        reader.read_sectors(0, 1, &mut buf, true).unwrap();
-        assert_eq!(buf[0], 1);
-        assert_eq!(buf[2047], 100);
-
-        reader.read_sectors(2, 1, &mut buf, true).unwrap();
-        assert_eq!(buf[0], 3);
-        assert_eq!(buf[2047], 102);
-
-        std::fs::remove_file(&dir).ok();
-    }
-
-    #[test]
-    fn iso_reader_capacity() {
-        let data = vec![0u8; 10 * SECTOR_SIZE as usize];
-        let dir = std::env::temp_dir().join("freemkv_test_iso_cap");
-        std::fs::write(&dir, &data).unwrap();
-
-        let reader = IsoSectorReader::open(dir.to_str().unwrap()).unwrap();
-        assert_eq!(reader.capacity(), 10);
-
-        std::fs::remove_file(&dir).ok();
-    }
-}