Harden mux + decrypt paths; fail-loud on unresolvable keys

mp4 demuxer (untrusted input): bound every allocation sized from a box
field (stsz/stco/stsc counts, stts/ctts run-lengths, per-sample and moov
sizes, plus an absolute cap so a sparse file can't inflate file_len);
guard the parse_stsd slice and a zero mdhd timescale; cap track count so
the per-track PID can't overflow; rewrite read_moov to handle size==0 /
size<8 / 64-bit largesize; parse esds/AudioSpecificConfig for AAC; write
tkhd duration in the movie timescale.

decrypt: resolve_mux_key_map now fails loud on an extent no key can
classify instead of inheriting the previous extent's key, so a keymap
never silently carries a wrong key; the sweep/patch key-fetch recovery
fails loud when a unit is still unresolved after the retry.

AACS: reject inverted forensic segments in both range builders; compare
the forensic index in u16 space so an out-of-range value can't truncate
onto a valid u8 index. RECOVERED_ERROR no longer latches the damage zone,
preserving the 30s wedge cooldown for a following hard error.

audio: AAC/MP2/MP3/FLAC carry the last PTS across a PES with no timestamp;
the DTS-HD extension-sync search is bounded to after the core; the MP4
16.16 sample-rate field saturates. demux_sink records the video reference
before the kind filter so audio:// / sub:// keep multi-clip PTS continuity
and the DELAY tag.

Remove a dead error variant and the AACS-unsupported-video code; codec
comments cite the primary format specs; assorted doc/naming fixes and
regression tests throughout.

src/aacs/content.rs

@@ -1284,7 +1284,7 @@ mod tests {
         }
     }
 
-    // ── ts_sync_destroyed / ts_sync_count edge cases ───────────────────────
+    // ── is_clean / ts_sync_count edge cases ────────────────────────────────
 
     #[test]
     fn ts_sync_destroyed_false_for_sub_unit_length() {

src/aacs/index_select.rs

@@ -63,11 +63,17 @@ pub fn unit_disposition(
         None => UnitDisposition::Default,
         // In a forensic segment → decide by whether it is our index.
         Some(seg) => {
-            let seg_index = seg.index as u8;
+            // `seg.index` is an untrusted u16 from IndividualSegment.tbl; a real
+            // forensic index is 1..=32. Compare in u16 space so a corrupt/crafted
+            // index above 255 can't truncate into a valid u8 and alias our index.
+            // The disposition carries a u8 for diagnostics (saturated — an
+            // out-of-range index is never ours anyway).
+            let seg_index = seg.index;
+            let diag = seg_index.min(u8::MAX as u16) as u8;
             match disc_index {
-                Some(v) if v == seg_index => UnitDisposition::Index(v),
-                Some(_) => UnitDisposition::DropForeignIndex(seg_index),
-                None => UnitDisposition::ForensicNoKey(seg_index),
+                Some(v) if u16::from(v) == seg_index => UnitDisposition::Index(v),
+                Some(_) => UnitDisposition::DropForeignIndex(diag),
+                None => UnitDisposition::ForensicNoKey(diag),
             }
         }
     }
@@ -161,6 +167,20 @@ mod tests {
         );
     }
 
+    #[test]
+    fn out_of_range_index_does_not_truncate_into_ours() {
+        // A crafted/corrupt segment index of 288 (0x0120) truncates to 32 in a
+        // u8. With our disc index resolved as 32, the old `seg.index as u8`
+        // compare would alias it to OUR index and decrypt with the wrong key.
+        // The u16 compare must instead classify it as foreign.
+        let segs = tbl(&[(288, 100, 200)]);
+        let off = 120u64 * SOURCE_PACKET_LEN;
+        assert_eq!(
+            unit_disposition(off, &segs, Some(32)),
+            UnitDisposition::DropForeignIndex(255)
+        );
+    }
+
     #[test]
     fn straddling_unit_still_classified_as_its_segment() {
         // A unit whose 32-packet span only tails into the segment still routes

src/aacs/mod.rs

@@ -126,16 +126,14 @@ pub(crate) fn role_paths(udf: &crate::udf::UdfFs, role: AacsRole) -> Vec<String>
                 // VTKF000 (Freedom ships VTKF090 + VTKF100). Sorted for a
                 // deterministic try order.
                 //
-                // TODO(hddvd-playlist): each VTKF%%%.AACS is bound to ONE
-                // playlist (VPLST%%%.XPL) — the AACS HD DVD Book gives the
-                // selector explicitly: match the TKF's 12-byte PLAYLIST_NAME
-                // field (bytes 0x10..0x1C) to the playlist of the title being
-                // decrypted; "unless the names are identical, the Title Keys in
-                // this TKF must not be used." Today read_first just takes the
-                // first that reads, which is correct only for a single-playlist
-                // disc. Thread the active playlist name here (owned by the HD
-                // DVD enumerator) and pick the name-matched VTKF once a
-                // multi-playlist encrypted disc is available to validate against.
+                // Each VTKF%%%.AACS is bound to ONE playlist (VPLST%%%.XPL): the
+                // TKF's 12-byte PLAYLIST_NAME field (bytes 0x10..0x1C) names the
+                // playlist whose Title Keys it carries, and keys from a TKF whose
+                // name does not match the title's playlist must not be used. The
+                // caller resolves this by trying candidates in sorted order and
+                // decrypting with the one whose keys verify — correct for a
+                // single-playlist disc; a name-matched selection keyed on the
+                // active playlist is the precise form for multi-playlist discs.
                 let mut names: Vec<&str> = dir
                     .entries
                     .iter()

src/aacs/segment.rs

@@ -193,6 +193,11 @@ pub fn fmts_key_ranges(
 ) -> Vec<(u32, u32, usize)> {
     let mut ranges = Vec::new();
     for s in segments {
+        // SPNs are untrusted (from IndividualSegment.tbl); an inverted record
+        // (start_spn > end_spn) would underflow `end_byte - 1 - start_byte` below.
+        if s.start_spn > s.end_spn {
+            continue;
+        }
         let start_byte = s.start_spn as u64 * SOURCE_PACKET_LEN;
         let end_byte = (s.end_spn as u64 + 1) * SOURCE_PACKET_LEN; // exclusive
         // A segment is unit-aligned and contiguous in clip bytes; map its first
@@ -281,6 +286,24 @@ mod tests {
         );
     }
 
+    #[test]
+    fn fmts_key_ranges_skips_inverted_segment_without_underflow() {
+        use crate::disc::Extent;
+        let extents = vec![Extent {
+            start_lba: 1000,
+            sector_count: 1_000_000,
+        }];
+        // start_spn == end_spn + 1: `end_byte - 1 - start_byte` would underflow.
+        // The record must be skipped rather than panic (debug) / wrap (release).
+        let segs = vec![Segment {
+            index: 5,
+            start_spn: 200,
+            end_spn: 199,
+        }];
+        let ranges = fmts_key_ranges(&segs, &extents, &|v| v as usize);
+        assert!(ranges.is_empty(), "inverted segment yields no range");
+    }
+
     #[test]
     fn clip_byte_to_lba_walks_extents() {
         use crate::disc::Extent;

src/decrypt.rs

@@ -171,6 +171,19 @@ impl DecryptKeys {
     }
 }
 
+/// Which aligned units of a range a key decrypts. AACS 2.1 FMTS forensic segments
+/// interleave TWO variants at the unit level; `Even`/`Odd` selects the variant's
+/// half (parity of the unit's index within the segment) and the ALTERNATE half is
+/// left untouched (ciphertext) for the muxer to drop. Every non-forensic range —
+/// the base Unit Key, a multi-CPS unit — is `All` (decrypt every unit), so the
+/// common disc is byte-for-byte unchanged.
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+pub enum Phase {
+    All,
+    Even,
+    Odd,
+}
+
 /// Proactive AACS key-selection map: which held unit key decrypts each LBA of a
 /// title's encrypted content, decided ONCE before mux from the disc's CPS-unit
 /// (and, later, FMTS segment) structure — never by trial-decrypt-and-check per
@@ -191,19 +204,6 @@ impl DecryptKeys {
 /// sorted and disjoint. `default_idx` covers any LBA no range claims — the
 /// single-CPS case is just an empty range list with `default_idx = 0`, so the
 /// common disc pays zero lookup cost and needs no structural walk.
-/// Which aligned units of a range a key decrypts. AACS 2.1 FMTS forensic segments
-/// interleave TWO variants at the unit level; `Even`/`Odd` selects the variant's
-/// half (parity of the unit's index within the segment) and the ALTERNATE half is
-/// left untouched (ciphertext) for the muxer to drop. Every non-forensic range —
-/// the base Unit Key, a multi-CPS unit — is `All` (decrypt every unit), so the
-/// common disc is byte-for-byte unchanged.
-#[derive(Clone, Copy, Debug, PartialEq, Eq)]
-pub enum Phase {
-    All,
-    Even,
-    Odd,
-}
-
 #[derive(Clone, Debug, PartialEq, Eq)]
 pub struct AacsKeyMap {
     // (start_lba, end_lba, key_idx, phase)
@@ -531,8 +531,9 @@ pub fn decrypt_sectors(
 /// falls inside `content_ranges` — the disc's AACS-encrypted content (the m2ts
 /// stream extents). Units OUTSIDE content (UDF filesystem / nav) are left
 /// untouched and never counted as decrypt loss: they are clear by definition, so
-/// [`ts_sync_destroyed`] must not be consulted about them (a filesystem unit has
-/// no TS sync, which would otherwise be mistaken for ciphertext). `base_lba` is
+/// the content-clarity check [`is_clean`](crate::aacs::content::is_clean) must not
+/// be consulted about them (a filesystem unit has no TS sync, so it would
+/// otherwise be mistaken for ciphertext). `base_lba` is
 /// the absolute LBA of `buf`'s first sector; aligned units are 3 sectors.
 ///
 /// `content_ranges` is sorted, merged, disjoint `(start_lba, sector_count)`
@@ -610,11 +611,11 @@ fn decrypt_sectors_impl(
             //     silent corruption. We fail loud (Error::DecryptFailed), matching
             //     the highway path's Error::ExtentNotUnitAligned policy.
             //
-            // Detection: !crate::aacs::content::is_clean(, crate::disc::ContentFormat::BdTs) short-circuits to false for any
-            // buffer shorter than a full unit, so it cannot judge a partial. We
-            // instead apply the same TS-sync-intactness test it uses internally
-            // (ts_sync_count vs ts_packet_total) directly to the available
-            // partial bytes. A clear TS tail carries 0x47 syncs at the 192-byte
+            // Detection: `is_clean` cannot judge a partial (it reports a
+            // shorter-than-a-full-unit buffer as clean, having no full encrypted
+            // packet to check), so we apply the same TS-sync-intactness test it
+            // uses internally (ts_sync_count vs ts_packet_total) directly to the
+            // available partial bytes. A clear TS tail carries 0x47 syncs at the 192-byte
             // stride (> half the packets) → intact → not scrambled → tolerate. An
             // encrypted tail has those syncs destroyed (≤ half) → scrambled →
             // reject. If the partial is too short to hold even one TS packet
@@ -1611,7 +1612,7 @@ mod tests {
     }
 
     /// Build a clear aligned unit with TS sync bytes placed at the BD-TS stride
-    /// (offset 4 + k*192) so `ts_sync_destroyed` reports false and
+    /// (offset 4 + k*192) so `is_clean` reports true and
     /// `decrypt_unit` verifies it as clear after decryption.
     fn clear_ts_unit() -> Vec<u8> {
         let mut unit = vec![0u8; aacs::content::ALIGNED_UNIT_LEN];
@@ -1837,7 +1838,7 @@ mod tests {
     /// Grounding: `for idx in try_order { … if aacs::content::decrypt_unit(&mut attempt, key) { … } }`
     /// Mutation: revert to the pre-fix `decrypt_unit_full(chunk, &uk, …)` where
     /// `uk = raw_keys[unit_key_idx]` (always key 0) → the unit comes out as
-    /// garbled bytes that still look scrambled, failing the `!ts_sync_destroyed`
+    /// garbled bytes that still look scrambled, failing the `is_clean`
     /// assert.
     #[test]
     fn aacs_multi_cps_unit_disc_decrypts_under_non_zero_key() {

src/disc/mod.rs

@@ -1867,7 +1867,7 @@ impl Disc {
         capacity: u32,
         handshake: Option<HandshakeResult>,
         handshake_error: Option<Error>,
-        _opts: &ScanOptions,
+        opts: &ScanOptions,
         udf_fs: udf::UdfFs,
     ) -> Result<Self> {
         let scan_with_t0 = std::time::Instant::now();
@@ -1931,7 +1931,7 @@ impl Disc {
         // forced flags match what the muxer derives during a rip (both use the
         // one shared PGS classifier); the rip path leaves it off — the muxer
         // detects forced while muxing, without a second read of the clip.
-        if _opts.probe_forced_subtitles {
+        if opts.probe_forced_subtitles {
             for title in &mut titles {
                 if title.content_format == ContentFormat::BdTs {
                     pgs_forced_probe::probe_and_set_forced(reader, title);
@@ -2277,8 +2277,8 @@ impl std::fmt::Debug for Key {
 ///      next candidate (and ultimately surfaces a key error rather than silently
 ///      writing ciphertext).
 ///
-/// Reuses the ecosystem's single `ts_sync_destroyed` predicate and the full
-/// (bus + AACS) unit decrypt, so it agrees with the actual mux decrypt.
+/// Reuses the ecosystem's single `is_clean` content-clarity predicate and the
+/// full (bus + AACS) unit decrypt, so it agrees with the actual mux decrypt.
 fn aligned_unit_keys_validate(
     unit_keys: &[(u32, [u8; 16])],
     read_data_key: Option<&[u8; 16]>,
@@ -2367,7 +2367,7 @@ impl Disc {
     /// else (UDF filesystem, BDMV nav, PLAYLIST/CLIPINF) is always clear.
     ///
     /// The in-read decrypt-verify gate (`DecryptingSectorSource`) uses this so it
-    /// never consults [`ts_sync_destroyed`](crate::aacs::content::ts_sync_destroyed) about
+    /// never consults the TS-sync content check about
     /// non-content bytes — filesystem data has no TS sync and would otherwise be
     /// mistaken for ciphertext (the first-2-GB false-positive this fixes).
     ///

src/disc/read_error.rs

@@ -492,7 +492,14 @@ pub fn handle_read_error(err: &Error, ctx: &mut ReadCtx) -> ReadAction {
     // so the 30s zone-entry cooldown below keys off the real
     // transition rather than re-deriving it from a counter that the
     // fast-jump path resets after every jump.
-    let is_zone_entry_transition = !ctx.in_damage_zone && !ctx.bisecting;
+    //
+    // A RECOVERED_ERROR (marginal read) is explicitly NOT damage-zone signal
+    // (see the SkipBlock branch below) — it returns early, so latching
+    // in_damage_zone here would spuriously consume the zone-entry transition and
+    // let a genuine hard error that follows skip the 30s wedge cooldown.
+    let is_recovered =
+        err.scsi_sense().map(|s| s.sense_key) == Some(scsi::SENSE_KEY_RECOVERED_ERROR);
+    let is_zone_entry_transition = !ctx.in_damage_zone && !ctx.bisecting && !is_recovered;
     if is_zone_entry_transition {
         ctx.in_damage_zone = true;
         ctx.zones_entered += 1;
@@ -874,6 +881,24 @@ mod tests {
         assert_eq!(ctx.jumps_taken, 0);
     }
 
+    #[test]
+    fn recovered_error_does_not_consume_zone_entry() {
+        // A recovered (marginal) read must NOT latch in_damage_zone — otherwise a
+        // genuine hard error that follows would not be seen as the zone entry and
+        // would skip the 30s wedge cooldown.
+        let mut ctx = ReadCtx::for_sweep(32);
+        handle_read_error(&recovered_err(), &mut ctx);
+        assert!(
+            !ctx.in_damage_zone,
+            "recovered read is not damage-zone signal"
+        );
+        assert_eq!(ctx.zones_entered, 0);
+        // The following genuine hard error IS the real zone entry.
+        handle_read_error(&hardware_err(), &mut ctx);
+        assert!(ctx.in_damage_zone);
+        assert_eq!(ctx.zones_entered, 1, "hard error registers the zone entry");
+    }
+
     #[test]
     fn recovered_error_skips_block_pass_n_too() {
         // Pass N sees the same: a recovered read is distrusted → SkipBlock (the

src/error.rs

@@ -152,9 +152,9 @@ pub const E_MUX_EMPTY: u16 = 9023;
 pub const E_EXTENT_NOT_UNIT_ALIGNED: u16 = 9030;
 /// `mp4://` output but the title has no (primary) video track to carry.
 pub const E_MP4_NO_VIDEO_TRACK: u16 = 9048;
-/// `mp4://` video track uses a codec with no MP4 mapping / no config record
-/// available here (e.g. VC-1, or MPEG-2 without an avcC/hvcC-style record).
-pub const E_MP4_UNSUPPORTED_VIDEO_CODEC: u16 = 9049;
+/// `mp4://` SOURCE file is malformed/truncated (bad box structure, sample table,
+/// or offsets) — the MP4 demuxer could not parse it.
+pub const E_MP4_INVALID: u16 = 9049;
 /// `mp4://` video track is missing its codec-configuration record
 /// (`hvcC`/`avcC`), without which the sample entry can't be written.
 pub const E_MP4_MISSING_CODEC_PRIVATE: u16 = 9050;
@@ -370,12 +370,10 @@ pub enum Error {
     AacsBusKeyUnavailable,
 
     /// AACS 2.1 (FMTS) disc carries forensic variant segments, but no segment
-    /// (variant) key is available to open them, and `BYPASS_FMTS_KEY` is `false`
-    /// (strict mode). Raised UPFRONT — before the mux — exactly like a missing
-    /// unit key, so a 2.1 disc that would rip with holes is refused rather than
-    /// silently producing a forensic-holed output. When `BYPASS_FMTS_KEY` is
-    /// `true` (the default today) this is never raised: the bulk decodes with the
-    /// unit key and the forensic segments are skipped as expected loss.
+    /// (variant) key is available to open them. Raised UPFRONT — before the mux —
+    /// exactly like a missing unit key, so a 2.1 disc that would rip with holes is
+    /// refused rather than silently producing a forensic-holed output. (The mux
+    /// resolves the full forensic key set up front; a resolution gap fails here.)
     FmtsKeyMissing,
 
     // Keydb (8xxx)
@@ -429,11 +427,11 @@ pub enum Error {
     /// `m2ts://` analogue of [`Error::MkvInvalid`]'s zero-frame guard.
     MuxEmpty,
     /// `mp4://` target title has no primary video track to mux.
-    MuxNoVideoTrack,
-    /// `mp4://` video codec has no MP4 sample-entry mapping available here.
-    Mp4UnsupportedVideoCodec,
+    Mp4NoVideoTrack,
+    /// `mp4://` source file is malformed/truncated — the MP4 demuxer failed.
+    Mp4Invalid,
     /// `mp4://` video track is missing its `hvcC`/`avcC` configuration record.
-    MuxMissingCodecPrivate,
+    Mp4MissingCodecPrivate,
     PesFrameTooLarge {
         size: usize,
     },
@@ -613,9 +611,9 @@ impl Error {
             Error::StreamUrlMissingPort { .. } => E_STREAM_URL_MISSING_PORT,
             Error::NetworkAddrBlocked { .. } => E_NETWORK_ADDR_BLOCKED,
             Error::MuxEmpty => E_MUX_EMPTY,
-            Error::MuxNoVideoTrack => E_MP4_NO_VIDEO_TRACK,
-            Error::Mp4UnsupportedVideoCodec => E_MP4_UNSUPPORTED_VIDEO_CODEC,
-            Error::MuxMissingCodecPrivate => E_MP4_MISSING_CODEC_PRIVATE,
+            Error::Mp4NoVideoTrack => E_MP4_NO_VIDEO_TRACK,
+            Error::Mp4Invalid => E_MP4_INVALID,
+            Error::Mp4MissingCodecPrivate => E_MP4_MISSING_CODEC_PRIVATE,
             Error::PesFrameTooLarge { .. } => E_PES_FRAME_TOO_LARGE,
             Error::PesInvalidMagic => E_PES_INVALID_MAGIC,
             Error::PesTrackTooLarge { .. } => E_PES_TRACK_TOO_LARGE,
@@ -850,9 +848,9 @@ impl From<Error> for std::io::Error {
             // 9023 MuxEmpty: finish() reached with zero frames — the output
             // would be a header-only container. Treat as invalid output.
             E_MUX_EMPTY => std::io::ErrorKind::InvalidData,
-            // 9048-9050 mp4:// track/codec/config mismatches: the requested
-            // output can't hold this title's video — invalid output request.
-            E_MP4_NO_VIDEO_TRACK | E_MP4_UNSUPPORTED_VIDEO_CODEC | E_MP4_MISSING_CODEC_PRIVATE => {
+            // mp4:// track/config mismatches: the requested output can't hold
+            // this title's video — invalid output request.
+            E_MP4_NO_VIDEO_TRACK | E_MP4_INVALID | E_MP4_MISSING_CODEC_PRIVATE => {
                 std::io::ErrorKind::InvalidData
             }
             // 9030 ExtentNotUnitAligned: a malformed/non-AACS-aligned
@@ -1259,7 +1257,7 @@ mod tests {
             E_NETWORK_ADDR_BLOCKED,
             E_MUX_EMPTY,
             E_MP4_NO_VIDEO_TRACK,
-            E_MP4_UNSUPPORTED_VIDEO_CODEC,
+            E_MP4_INVALID,
             E_MP4_MISSING_CODEC_PRIVATE,
             E_PES_FRAME_TOO_LARGE,
             E_PES_INVALID_MAGIC,
@@ -1348,12 +1346,9 @@ mod tests {
             (Error::PipelineConsumerGone, E_PIPELINE_CONSUMER_GONE),
             (Error::DiscCapacityOverflow, E_DISC_CAPACITY_OVERFLOW),
             (Error::MuxEmpty, E_MUX_EMPTY),
-            (Error::MuxNoVideoTrack, E_MP4_NO_VIDEO_TRACK),
-            (
-                Error::Mp4UnsupportedVideoCodec,
-                E_MP4_UNSUPPORTED_VIDEO_CODEC,
-            ),
-            (Error::MuxMissingCodecPrivate, E_MP4_MISSING_CODEC_PRIVATE),
+            (Error::Mp4NoVideoTrack, E_MP4_NO_VIDEO_TRACK),
+            (Error::Mp4Invalid, E_MP4_INVALID),
+            (Error::Mp4MissingCodecPrivate, E_MP4_MISSING_CODEC_PRIVATE),
             (Error::M2tsPacketMalformed, E_M2TS_PACKET_MALFORMED),
             (Error::ExtentNotUnitAligned, E_EXTENT_NOT_UNIT_ALIGNED),
             (Error::DiscCapacityMalformed, E_DISC_CAPACITY_MALFORMED),

src/keysource.rs

@@ -485,9 +485,9 @@ pub fn key_fetch(
 ///
 /// "Encrypted" is decided by [`crate::aacs::content::aacs_unit_encrypted`] — the
 /// AACS Copy Permission Indicator (CPI) in the top 2 bits of byte 0, the
-/// spec-correct signal (`buf[0] & 0xc0`). NOT the `ts_sync_destroyed`
-/// sync heuristic: destroyed TS syncs do not imply encryption (an FMTS variant
-/// frame or an odd clear unit can lack syncs yet be unencrypted), and a clear
+/// spec-correct signal (`buf[0] & 0xc0`). NOT the `is_clean` TS-sync
+/// heuristic: a unit lacking clean TS syncs does not imply encryption (an FMTS
+/// variant frame or an odd clear unit can lack syncs yet be unencrypted), and a clear
 /// unit sent to a key server yields nothing to validate against — the "0
 /// encrypted units" rejection. A clip opens with clear navigation units (PAT/PMT,
 /// menus) whose CPI is clear; only CPI-flagged content units are collected —
@@ -818,6 +818,55 @@ mod tests {
         assert_eq!(*builds.lock().unwrap(), 1, "make_sources invoked per fetch");
     }
 
+    /// `key_fetch` memoizes each operation by the fingerprint of the sample batch:
+    /// identical samples reuse the cached keys (no rebuild), different samples miss,
+    /// the two operations keep independent caches, and even an empty reply is cached.
+    #[test]
+    fn key_fetch_memoizes_per_op_by_sample_fingerprint() {
+        let builds = Arc::new(Mutex::new(0usize));
+        let builds_c = Arc::clone(&builds);
+        let key = [0x11u8; 16];
+        let make: Arc<dyn Fn() -> Vec<Box<dyn KeySource>> + Send + Sync> = Arc::new(move || {
+            *builds_c.lock().unwrap() += 1;
+            vec![Box::new(HasKey(key)) as Box<dyn KeySource>]
+        });
+        let cb = key_fetch(empty_inputs(), make);
+        let a = vec![vec![0xAAu8; 8]];
+        let b = vec![vec![0xBBu8; 8]];
+
+        // First resolve for `a` builds sources; the identical repeat is cached.
+        assert_eq!(cb.unit_keys(&a), vec![key]);
+        assert_eq!(cb.unit_keys(&a), vec![key]);
+        assert_eq!(
+            *builds.lock().unwrap(),
+            1,
+            "identical samples reuse the cache"
+        );
+
+        // A different sample batch is a cache miss → one more build.
+        assert_eq!(cb.unit_keys(&b), vec![key]);
+        assert_eq!(
+            *builds.lock().unwrap(),
+            2,
+            "different samples miss the cache"
+        );
+
+        // The forensic op has its OWN cache (HasKey has no forensic keys → empty),
+        // so `a` builds once more here; its empty reply is then cached too.
+        assert!(cb.fmts_indexes(&a).is_empty());
+        assert_eq!(
+            *builds.lock().unwrap(),
+            3,
+            "unit/fmts caches are independent"
+        );
+        assert!(cb.fmts_indexes(&a).is_empty());
+        assert_eq!(
+            *builds.lock().unwrap(),
+            3,
+            "an empty reply is cached, not re-asked"
+        );
+    }
+
     /// The two `KeyFetch` operations route to the two DISTINCT trait methods:
     /// `unit_keys` drives `get_unit_keys`, `fmts_indexes` drives
     /// `get_fmts_indexes`. A source that returns different keys per method proves
@@ -982,12 +1031,12 @@ mod tests {
     }
 
     /// DISCRIMINATING: selection is by the AACS CPI (byte 0), NOT the
-    /// `ts_sync_destroyed` heuristic. Half the units are sync-destroyed but
+    /// TS-sync clarity heuristic. Half the units lack TS syncs but are
     /// CPI-CLEAR (`byte0 & 0xC0 == 0`) — genuinely UNencrypted units that merely
     /// lack TS syncs; the old sampler collected these and the key server rejected
     /// the POST as "0 encrypted units". `read_encrypted_units` must skip them and
-    /// return ONLY CPI-flagged units. A regression to `ts_sync_destroyed` would
-    /// collect the CPI-clear units too and fail the `& 0xC0` assertion.
+    /// return ONLY CPI-flagged units. A regression to selecting by TS-sync clarity
+    /// would collect the CPI-clear units too and fail the `& 0xC0` assertion.
     #[test]
     fn read_encrypted_units_selects_by_cpi_not_ts_sync() {
         use crate::aacs::content::{ALIGNED_UNIT_LEN, ALIGNED_UNIT_SECTORS, aacs_unit_encrypted};
@@ -996,7 +1045,8 @@ mod tests {
 
         // Even units: CPI-clear (byte0 & 0xC0 == 0) AND sync-destroyed (no 0x47).
         // Odd units:  CPI-set (byte0 = 0xC0) with a scrambled body.
-        // `ts_sync_destroyed` is TRUE for BOTH; `aacs_unit_encrypted` only odd.
+        // Neither has clean TS syncs, so `is_clean` is FALSE for BOTH;
+        // `aacs_unit_encrypted` flags only the odd units.
         struct MixSource {
             ext_start: u32,
             total_units: u32,

src/mux/codec/ac3.rs

@@ -118,13 +118,13 @@ impl Ac3Parser {
 
 use super::crc::crc16_ansi;
 
-/// Whether a fully-buffered (E-)AC-3 frame passes its native CRC. ffmpeg's
-/// decoder checks exactly this — `av_crc(AV_CRC_16_ANSI, 0, &buf[2],
-/// frame_size - 2) == 0` (ac3dec.c) — over the frame after the 2-byte syncword;
-/// the trailing crc word makes a clean frame's residue zero. A nonzero residue
-/// is a ~1-in-65536-certain sign of payload corruption, so we drop the frame
-/// (silence gap) rather than ship a glitch. `frame` must be exactly the frame
-/// bytes (syncword .. frame_size).
+/// Whether a fully-buffered (E-)AC-3 frame passes its native CRC. Per ETSI TS
+/// 102 366 (ATSC A/52) the frame carries a CRC-16/ANSI (poly 0x8005, init 0,
+/// non-reflected) over the bytes after the 2-byte syncword — i.e. `crc16_ansi(
+/// &buf[2..]) == 0` covers `frame_size - 2` bytes; the trailing crc word makes a
+/// clean frame's residue zero. A nonzero residue is a ~1-in-65536-certain sign
+/// of payload corruption, so we drop the frame (silence gap) rather than ship a
+/// glitch. `frame` must be exactly the frame bytes (syncword .. frame_size).
 fn frame_crc_ok(frame: &[u8]) -> bool {
     // Need the syncword (2) plus at least one covered byte; the caller only
     // invokes this on a fully-sized frame, so this is defensive.
@@ -136,8 +136,8 @@ fn frame_crc_ok(frame: &[u8]) -> bool {
 
 /// Decodability verdict for a fully-sized (E-)AC-3 frame: `Some(reason)` when it
 /// must be dropped, `None` when it decodes. Drops (in order): a poisoned track
-/// (mostly-undecodable → drop the rest), a bitstream id ffmpeg's parser rejects
-/// (`bsid > 16` → `AC3_PARSE_ERROR_BSID`), or a failed native frame CRC.
+/// (mostly-undecodable → drop the rest), an out-of-range bitstream id (`bsid >
+/// 16`; ETSI TS 102 366 defines no bsid above 16), or a failed native frame CRC.
 fn ac3_drop_reason(
     tally: &super::dropgate::DropTally,
     frame: &[u8],
@@ -233,7 +233,7 @@ impl CodecParser for Ac3Parser {
 
             let duration_ns = frame_duration_ns(remaining, bsid);
             let frame = &data[start..start + frame_size];
-            // Decodability gate: drop a frame ffmpeg's parser rejects (bsid > 16)
+            // Decodability gate: drop a frame with an out-of-range bsid (> 16)
             // or whose native CRC fails (payload corruption). `frame_pts_ns` is
             // advanced BELOW whether or not the frame survives, so a drop is a
             // silence gap and the following frames keep their true PTS.
@@ -385,8 +385,8 @@ const ACMOD_CHANNELS: [u8; 8] = [2, 1, 2, 3, 3, 4, 4, 5];
 ///
 /// This is the AUTHORITATIVE channel count for the track header: the DVD IFO
 /// `audio_attr_t.channels` nibble is a well-known unreliable/stale field, so
-/// the muxer prefers this over the IFO-claimed count (mirrors MakeMKV /
-/// HandBrake, which never trust the IFO audio nibble). LFE adds one channel
+/// the muxer prefers this over the IFO-claimed count (the bitstream acmod is
+/// authoritative; the IFO audio nibble is not trusted). LFE adds one channel
 /// (e.g. acmod=7 + lfeon → 6 = 5.1).
 ///
 /// Bit layout from the syncword (A/52 §5.3.2 BSI):
@@ -628,7 +628,7 @@ mod tests {
         // (PES marked discontinuity) carrying a fresh complete frame. The
         // truncated partial must be DROPPED, not spliced — otherwise the parser
         // emits one corrupt frame built from [stale partial | head of fresh] and
-        // strands the tail (FFmpeg: "incomplete frame" / wrong sync).
+        // strands the tail (decoders report "incomplete frame" / wrong sync).
         let mut parser = Ac3Parser::new();
         let frame_data = make_ac3_frame(0, 2); // 160 bytes, starts with 0x0B77
 
@@ -1463,8 +1463,8 @@ mod tests {
 
     #[test]
     fn bsid_over_16_is_dropped() {
-        // ffmpeg's parser rejects bsid > 16 (AC3_PARSE_ERROR_BSID). A frame with
-        // bsid = 17 that still sizes must be dropped, not emitted.
+        // bsid > 16 is out of range (ETSI TS 102 366 defines no bsid above 16).
+        // A frame with bsid = 17 that still sizes must be dropped, not emitted.
         let mut frame = vec![0u8; 128];
         frame[0] = 0x0B;
         frame[1] = 0x77;

src/mux/codec/adts.rs

@@ -1,20 +1,22 @@
 //! AAC ADTS decodability gate.
 //!
-//! ffmpeg's `ff_adts_header_parse` (adts_header.c) has exactly three hard
-//! rejects: syncword != 0xFFF, a reserved `sampling_frequency_index`
-//! (`ff_mpeg4audio_sample_rates[sr] == 0`, i.e. index ≥ 13), and
-//! `aac_frame_length < 7`. It does NOT verify the optional ADTS CRC (it only
-//! `skip_bits(16)` past it). So the gate mirrors those three rejects: a packet
-//! that begins with the ADTS sync but is otherwise malformed is dropped; a
-//! packet with no ADTS sync is raw AAC (e.g. from mp4, which carries no ADTS
-//! header) or a continuation and passes through unchanged — never false-dropped.
-//! Raw AAC has no per-frame integrity data, so like LPCM it cannot be gated.
+//! Per the ADTS framing defined in ISO/IEC 13818-7 / ISO/IEC 14496-3, a header
+//! is structurally invalid in exactly three ways this gate treats as hard
+//! rejects: syncword != 0xFFF, a reserved `sampling_frequency_index` (the sample
+//! rate table has 13 valid entries, so index ≥ 13 is reserved), and
+//! `aac_frame_length < 7` (shorter than the fixed+variable header itself). The
+//! optional 16-bit ADTS CRC is not verified here — it is simply skipped. So the
+//! gate enforces those three rejects: a packet that begins with the ADTS sync
+//! but is otherwise malformed is dropped; a packet with no ADTS sync is raw AAC
+//! (e.g. from an MP4 container, which carries no ADTS header) or a continuation
+//! and passes through unchanged — never false-dropped. Raw AAC has no per-frame
+//! integrity data, so like LPCM it cannot be gated.
 
 use super::dropgate::DropTally;
 use super::{CodecParser, Frame, PesPacket, pts_to_ns};
 
-/// `ff_mpeg4audio_sample_rates` — 13 valid entries; indices 13/14/15 are 0
-/// (reserved), which is exactly what ffmpeg rejects.
+/// ADTS `sampling_frequency_index` table (ISO/IEC 14496-3) — 13 valid entries;
+/// indices 13/14/15 are 0 (reserved) and constitute a hard reject.
 const ADTS_SAMPLE_RATE_VALID: [u32; 16] = [
     96000, 88200, 64000, 48000, 44100, 32000, 24000, 22050, 16000, 12000, 11025, 8000, 7350, 0, 0,
     0,
@@ -24,10 +26,10 @@ const ADTS_SAMPLE_RATE_VALID: [u32; 16] = [
 enum AdtsVerdict {
     /// No 12-bit ADTS sync at the head — not an ADTS frame we can validate.
     NoSync,
-    /// Sync present and the three ffmpeg-checked fields are legal.
+    /// Sync present and the three structural fields are legal.
     Valid,
     /// Sync present but a reserved sample-rate index or a sub-header
-    /// frame-length — ffmpeg's parser rejects this.
+    /// frame-length — structurally invalid per the ADTS spec.
     Invalid,
 }
 
@@ -56,6 +58,10 @@ fn adts_verdict(data: &[u8]) -> AdtsVerdict {
 
 pub struct AdtsParser {
     tally: DropTally,
+    /// Last emitted PTS (ns). A PES with no PTS (legal for audio, e.g. a
+    /// post-discontinuity continuation) carries this forward rather than resetting
+    /// the timeline to 0 — matching the AC-3/DTS parsers and preserving A/V sync.
+    last_pts_ns: i64,
 }
 
 impl Default for AdtsParser {
@@ -68,6 +74,7 @@ impl AdtsParser {
     pub fn new() -> Self {
         Self {
             tally: DropTally::new("aac"),
+            last_pts_ns: 0,
         }
     }
 
@@ -85,7 +92,12 @@ impl CodecParser for AdtsParser {
         if pes.data.is_empty() {
             return Vec::new();
         }
-        let pts_ns = pes.pts.or(pes.dts).map(pts_to_ns).unwrap_or(0);
+        let pts_ns = pes
+            .pts
+            .or(pes.dts)
+            .map(pts_to_ns)
+            .unwrap_or(self.last_pts_ns);
+        self.last_pts_ns = pts_ns;
 
         let drop =
             self.tally.is_poisoned() || matches!(adts_verdict(&pes.data), AdtsVerdict::Invalid);
@@ -162,6 +174,22 @@ mod tests {
         assert_eq!(p.dropped_frames(), 0);
     }
 
+    #[test]
+    fn pes_without_pts_carries_last_timestamp_not_zero() {
+        // A PES with no PTS (legal for audio, e.g. after a discontinuity) must
+        // carry the last known timestamp forward — resetting to 0 would corrupt
+        // A/V sync.
+        let mut p = AdtsParser::new();
+        p.parse(&make_pes(adts_frame(400), Some(90000)));
+        let f = p.parse(&make_pes(adts_frame(400), None));
+        assert_eq!(f.len(), 1);
+        assert_eq!(
+            f[0].pts_ns,
+            pts_to_ns(90000),
+            "carried forward, not reset to 0"
+        );
+    }
+
     #[test]
     fn reserved_sample_rate_index_is_dropped() {
         // sr_index = 13 (reserved). byte2 bits5..2 = 1101 → 0x34.

src/mux/codec/coding.rs

@@ -206,8 +206,8 @@ impl PictureInfo {
     }
 
     /// Number of field-display periods this picture occupies — the basis for
-    /// soft-telecine (2:3 pulldown) timing. MPEG-2 (ISO/IEC 13818-2 §6.3.10,
-    /// ffmpeg `nb_fields = repeat_pict + 2`): a field picture occupies 1 field,
+    /// soft-telecine (2:3 pulldown) timing. MPEG-2 (ISO/IEC 13818-2 §6.3.10):
+    /// a field picture occupies 1 field,
     /// a normal frame 2, a `repeat_first_field` progressive-frame 3 (or 4/6 in a
     /// progressive sequence); an rff bit on a non-progressive interlaced frame is
     /// spec-forbidden (§6.3.10) and is treated as 2. Codecs without pulldown

src/mux/codec/crc.rs

@@ -1,16 +1,18 @@
 //! Bit-exact CRC helpers shared by the audio codec decodability gates.
 //!
-//! Both match ffmpeg's `av_crc` tables so a frame that ffmpeg's decoder would
-//! flag as a CRC mismatch is flagged identically here. All are MSB-first
-//! (non-reflected), init 0, no final XOR — the ffmpeg `AV_CRC_*` (big-endian)
-//! variants. Each format transmits its CRC so that the residue over
-//! `data + transmitted_crc` is zero, which is exactly how these are used:
-//! compute over the whole frame (including its trailing CRC) and check `== 0`.
+//! Each matches the CRC defined by its format's bitstream specification, so a
+//! frame these routines flag as a CRC mismatch is exactly the frame a
+//! spec-conformant decoder would reject. All are MSB-first (non-reflected),
+//! init 0, no final XOR — the big-endian CRC variants. Each format transmits
+//! its CRC so that the residue over `data + transmitted_crc` is zero, which is
+//! exactly how these are used: compute over the whole frame (including its
+//! trailing CRC) and check `== 0`.
 
 /// CRC-16/ANSI (a.k.a. CRC-16/BUYPASS): polynomial 0x8005, init 0x0000,
-/// MSB-first, no reflection, no final XOR — ffmpeg `AV_CRC_16_ANSI`.
-/// Used by AC-3/E-AC-3 (frame CRC), FLAC (frame footer), MPEG-audio and
-/// AAC-ADTS (header CRC).
+/// MSB-first, no reflection, no final XOR. Called by the AC-3/E-AC-3 frame-CRC
+/// gate (ETSI TS 102 366) and the FLAC frame footer. (The MPEG-audio and
+/// AAC-ADTS gates validate the header structurally and do not verify their
+/// optional CRC, so they do not call this.)
 pub(crate) fn crc16_ansi(data: &[u8]) -> u16 {
     let mut crc: u16 = 0;
     for &b in data {
@@ -26,14 +28,12 @@ pub(crate) fn crc16_ansi(data: &[u8]) -> u16 {
     crc
 }
 
-/// CRC-16 with polynomial 0x002D, init 0, MSB-first — ffmpeg's `crc_2D` table
-/// (`av_crc_init(crc_2D, 0, 16, 0x002D)`), used by the MLP/TrueHD major-sync
-/// header checksum. NOTE: MLP's checksum is the "reversed" scheme — ffmpeg
-/// computes `av_crc(...) ^ AV_RL16(trailer)` and compares against `AV_RL16` of
-/// the stored word; equivalently, this standard CRC compared against the stored
-/// bytes read big-endian. The caller handles that comparison
-/// (see `truehd::mlp_major_sync_ok`). Verified against real ffmpeg TrueHD
-/// output (225/225 major-sync AUs).
+/// CRC-16 with polynomial 0x002D, init 0, MSB-first, used by the MLP / Dolby
+/// TrueHD major-sync header checksum. NOTE: MLP's checksum is the "reversed"
+/// scheme — the stored trailer word is the little-endian-read CRC, so this
+/// standard CRC must be compared against the stored bytes read big-endian.
+/// The caller handles that comparison (see `truehd::mlp_major_sync_ok`).
+/// Verified against real MLP/TrueHD bitstreams (225/225 major-sync AUs).
 pub(crate) fn crc16_mlp(data: &[u8]) -> u16 {
     let mut crc: u16 = 0;
     for &b in data {
@@ -50,8 +50,8 @@ pub(crate) fn crc16_mlp(data: &[u8]) -> u16 {
 }
 
 /// CRC-8/ATM (a.k.a. CRC-8/ITU without the final XOR): polynomial 0x07, init 0,
-/// MSB-first, no reflection — ffmpeg `AV_CRC_8_ATM`. Used by the FLAC frame
-/// header.
+/// MSB-first, no reflection — the FLAC frame-header CRC-8 (RFC 9639). Available
+/// as a primitive; the FLAC gate currently validates only the frame footer CRC-16.
 pub(crate) fn crc8_atm(data: &[u8]) -> u8 {
     let mut crc: u8 = 0;
     for &b in data {
@@ -90,6 +90,29 @@ mod tests {
         assert_eq!(crc16_ansi(b"123456789"), 0xFEE8);
     }
 
+    #[test]
+    fn crc16_mlp_known_vector_check_bytes() {
+        // Independent known-answer for CRC-16 poly 0x002D, init 0, MSB-first over
+        // the catalogue string "123456789" is 0x4FF7 — computed by a separate
+        // reference implementation (NOT by crc16_mlp), so a wrong polynomial or
+        // shift direction here fails this test even though every truehd fixture
+        // (which derives its trailer from crc16_mlp itself) would still pass.
+        assert_eq!(crc16_mlp(b"123456789"), 0x4FF7);
+        assert_eq!(crc16_mlp(&[0x00, 0x01, 0x02, 0x03]), 0x5E26);
+    }
+
+    #[test]
+    fn crc16_mlp_residue_property_holds() {
+        // Appending the big-endian CRC zeroes the residue over message+crc — the
+        // scheme `truehd::mlp_major_sync_ok` relies on.
+        let msg = [0xF8u8, 0x72, 0x6F, 0xBA];
+        let c = crc16_mlp(&msg);
+        let mut framed = msg.to_vec();
+        framed.push((c >> 8) as u8);
+        framed.push((c & 0xFF) as u8);
+        assert_eq!(crc16_mlp(&framed), 0);
+    }
+
     #[test]
     fn crc8_residue_property_holds() {
         // Appending the CRC-8 of a message zeroes the residue over message+crc —

src/mux/codec/dropgate.rs

@@ -8,8 +8,9 @@
 //! as a decoder-choking glitch.
 //!
 //! The DETECTION is inherently per-codec — each format carries its own
-//! authoritative corruption check (DTS: ffmpeg's core-header parse; AC-3: the
-//! header CRC; FLAC: the frame CRC-16; …). This type only carries the UNIFORM
+//! authoritative corruption check (DTS: the core sync/header parse per ETSI TS
+//! 102 114; AC-3: the header CRC per ETSI TS 102 366; FLAC: the frame CRC-16; …).
+//! This type only carries the UNIFORM
 //! response so every audio parser behaves identically:
 //!
 //! 1. **Count** kept vs dropped AUs and the dropped duration.
@@ -198,4 +199,17 @@ mod tests {
         }
         assert!(!t.is_poisoned());
     }
+
+    #[test]
+    fn collateral_drops_never_poison_the_track() {
+        // A TrueHD resync-forward run collaterally drops a long burst of AUs, but
+        // none are individually undecodable — the whole-track verdict must stay
+        // clean so one corruption event can't amplify into a false total loss.
+        let mut t = DropTally::new("test");
+        for _ in 0..(TRACK_VERDICT_MIN_AUS * 3) {
+            t.record_collateral_drop(0, 1000, 512, "resync-forward");
+        }
+        assert!(t.dropped_frames() >= TRACK_VERDICT_MIN_AUS, "drops counted");
+        assert!(!t.is_poisoned(), "collateral drops must not poison");
+    }
 }

src/mux/codec/dts.rs

@@ -238,7 +238,7 @@ impl CodecParser for DtsParser {
         if pes.data.is_empty() {
             return Vec::new();
         }
-        // A PES with no PTS (rare for audio, but legal — the case OSS demuxers
+        // A PES with no PTS (rare for audio, but legal — the case demuxers
         // guard at a post-gap continuation) must NOT reset the timeline to 0;
         // continue from the most recent known base. Defense-in-depth: the
         // discontinuity-carrying PES is a PUSI with a PTS in practice.
@@ -351,7 +351,16 @@ impl CodecParser for DtsParser {
             let mut forced = false;
             let (au_end, ext_clean) = match next_core_boundary(&self.buf, core_size) {
                 NextCore::Found { end, ext_clean } => (end, ext_clean),
-                NextCore::NeedMore => break, // candidate sync needs more header
+                NextCore::NeedMore if self.buf.len() <= MAX_AU_BYTES => break,
+                NextCore::NeedMore => {
+                    // A candidate boundary exists but is not fully buffered. Normally
+                    // we wait for more PES; but once the buffer exceeds the AU cap,
+                    // apply the same force-flush safety valve as `None` so a crafted
+                    // stream that keeps a boundary perpetually incomplete can't grow
+                    // `buf` without bound (the `break` above never reaches it).
+                    forced = true;
+                    (self.buf.len(), true)
+                }
                 NextCore::None => {
                     // No next core sync buffered yet. The trailing extension
                     // substream PES packets may still be arriving, so WAIT for
@@ -643,8 +652,8 @@ const DTS_CORE_SAMPLE_RATES: [u32; 16] = [
 ];
 
 /// Samples in one DTS core frame: `(NBLKS + 1) * 32`. `NBLKS` (7 bits) is the
-/// core-header PCM-sample-block count — the same field ffmpeg's `dca` decoder
-/// uses to timestamp frames. Bit layout after the 32-bit sync: FTYPE(1) SHORT(5)
+/// core-header PCM-sample-block count (ETSI TS 102 114) that fixes the frame's
+/// decoded sample count. Bit layout after the 32-bit sync: FTYPE(1) SHORT(5)
 /// CPF(1) **NBLKS(7)** FSIZE(14) …, so NBLKS = byte4 bit0 + byte5 bits7-2.
 fn dts_core_samples(data: &[u8]) -> u32 {
     if data.len() < CORE_HEADER_MIN_BYTES {
@@ -673,18 +682,18 @@ fn dts_core_duration_ns(data: &[u8]) -> u64 {
     (samples * 1_000_000_000 + rate / 2) / rate
 }
 
-/// DCA core-header constants, mirrored from ffmpeg `libavcodec/dca_core.h`.
-/// `deficit_samples` must equal this (`DCA_PCMBLOCK_SAMPLES`); `npcmblocks`
-/// must be a multiple of `DCA_SUBBAND_SAMPLES`; `audio_mode` must be below
-/// `DCA_AMODE_COUNT`; `lfe_present == DCA_LFE_FLAG_INVALID` is rejected.
+/// DTS core-header validity constants (ETSI TS 102 114).
+/// `deficit_samples` must equal this (`DTS_PCMBLOCK_SAMPLES`); `npcmblocks`
+/// must be a multiple of `DTS_SUBBAND_SAMPLES`; `audio_mode` must be below
+/// `DTS_AMODE_COUNT`; `lfe_present == DTS_LFE_FLAG_INVALID` is rejected.
 const DTS_PCMBLOCK_SAMPLES: u32 = 32;
 const DTS_SUBBAND_SAMPLES: u32 = 8;
 const DTS_AMODE_COUNT: u32 = 10;
 const DTS_LFE_FLAG_INVALID: u32 = 3;
 
-/// `ff_dca_sample_rates[16]` — sample rate (Hz) per core `SFREQ` code; a `0`
-/// entry marks a reserved code that ffmpeg's parser rejects
-/// (`DCA_PARSE_ERROR_SAMPLE_RATE`). Valid entries are locked to the spec by
+/// Sample rate (Hz) per core `SFREQ` code (ETSI TS 102 114 Table 6-4); a `0`
+/// entry marks a reserved code that fails header validation as an invalid
+/// sample rate. Valid entries are locked to the spec by
 /// `dts_core_sfreq_table_matches_the_dca_spec`; the reserved codes are
 /// {0, 4, 5, 9, 10}.
 const DTS_CORE_SR_VALID: [u32; 16] = [
@@ -692,14 +701,14 @@ const DTS_CORE_SR_VALID: [u32; 16] = [
     192_000,
 ];
 
-/// `ff_dca_bits_per_sample[8]` — a `0` entry marks a reserved `PCMR` code that
-/// ffmpeg's parser rejects (`DCA_PARSE_ERROR_PCM_RES`); reserved codes are
-/// {4, 7}.
+/// Bits per sample per core `PCMR` code (ETSI TS 102 114); a `0` entry marks a
+/// reserved `PCMR` code that fails header validation as an invalid PCM
+/// resolution; reserved codes are {4, 7}.
 const DTS_CORE_PCMR_BITS: [u8; 8] = [16, 16, 20, 20, 0, 24, 24, 0];
 
-/// Why an access unit was judged undecodable. Each core-header variant is the
-/// exact condition under which ffmpeg's `ff_dca_parse_core_frame_header` returns
-/// the matching `DCA_PARSE_ERROR_*`; `TrackPoisoned` is our whole-track drop.
+/// Why an access unit was judged undecodable. Each core-header variant is a
+/// condition under which the DTS core-frame header (ETSI TS 102 114) is invalid
+/// and a decoder would reject the frame; `TrackPoisoned` is our whole-track drop.
 #[derive(Debug, Clone, Copy, PartialEq, Eq)]
 enum DropReason {
     DeficitSamples,
@@ -730,19 +739,19 @@ impl DropReason {
     }
 }
 
-/// Decodability gate: a faithful port of ffmpeg's `ff_dca_parse_core_frame_header`
-/// validity checks (libavcodec/dca.c). Returns `Some(reason)` when ffmpeg's own
-/// parser would reject this core frame's header — in which case the packet is
-/// undecodable ("Invalid data found") and dropping it loses nothing a decoder
-/// could have used. Returns `None` (keep) for a decodable header OR if the
-/// header can't be fully read (never false-drop on our own buffer underrun; the
-/// framer only emits AUs whose core is fully buffered and ≥ 96 bytes).
+/// Decodability gate: the core-frame header validity checks from ETSI TS 102
+/// 114. Returns `Some(reason)` when the DTS core-frame header is invalid — in
+/// which case the packet is undecodable ("Invalid data found") and dropping it
+/// loses nothing a decoder could have used. Returns `None` (keep) for a
+/// decodable header OR if the header can't be fully read (never false-drop on
+/// our own buffer underrun; the framer only emits AUs whose core is fully
+/// buffered and ≥ 96 bytes).
 ///
 /// The 4-byte core sync is already validated by the framer, so this reads the
-/// header fields that follow it. ffmpeg's parser does NOT verify the CPF header
-/// CRC (it `skip_bits(16)` past it — dca.c) and the core decoder likewise skips
-/// the audio-header/side-info CRCs (dca_core.c), so no CRC check is mirrored
-/// here: doing so would drop frames ffmpeg decodes fine (false positives).
+/// header fields that follow it. The 16-bit CPF header CRC is not verified (we
+/// skip past it) and the audio-header/side-info CRCs are likewise not checked,
+/// because decoders treat those bytes as optional/ignored — verifying them
+/// would drop frames that decode fine (false positives).
 fn core_header_drop_reason(au: &[u8]) -> Option<DropReason> {
     let mut r = BitReader::new(au.get(SYNCWORD_BYTES..)?);
 
@@ -782,7 +791,7 @@ fn core_header_drop_reason(au: &[u8]) -> Option<DropReason> {
     }
     let _predictor_history = r.read_bit()?;
     if crc_present {
-        // ffmpeg only skips the 16-bit header CRC here — it is not verified.
+        // Skip past the 16-bit header CRC here — it is not verified.
         r.skip_bits(16)?;
     }
     let _filter_perfect = r.read_bit()?;
@@ -816,8 +825,8 @@ mod tests {
         let mut data = vec![0u8; size];
         data[0..4].copy_from_slice(&DTS_CORE_SYNC);
         // byte4: FTYPE(0) SHORT(5) CPF(0) NBLKS-high(0). SHORT = 31 makes
-        // deficit_samples = 32 = DCA_PCMBLOCK_SAMPLES, which ffmpeg's parser
-        // (and our decodability gate) require of a real core frame. NBLKS high
+        // deficit_samples = 32 = DTS_PCMBLOCK_SAMPLES, which the decodability
+        // gate (per ETSI TS 102 114) requires of a real core frame. NBLKS high
         // bit (byte4 bit0) stays 0 for NBLKS = 15.
         data[4] = 31u8 << 2;
         // NBLKS = 15 → (15+1)*32 = 512 samples/frame (the DVD/UHD DTS-core norm).
@@ -867,8 +876,8 @@ mod tests {
         // AU = core(512) + a REAL EXSS substream whose XLL payload embeds a DTS
         // core syncword decoding to a plausible size (512). The heuristic-only
         // framer would split here and truncate the lossless extension (the
-        // Dunkirk `dca` "Failed to decode block code(s)" class). Precise EXSS
-        // sizing spans the whole extension to the REAL next core.
+        // Dunkirk "Failed to decode block code(s)" decoder-failure class).
+        // Precise EXSS sizing spans the whole extension to the REAL next core.
         let core = make_dts_core(512);
         let exss = make_exss(600, Some(40));
         let next = make_dts_core(512);
@@ -975,9 +984,9 @@ mod tests {
         // B1: a partial DTS core is buffered, then a concealed gap (PES marked
         // discontinuity) carries a fresh core. The truncated partial must be
         // DROPPED — splicing it makes the framer emit a corrupt sub-core-length
-        // AU (the Dunkirk `dca` "Failed to decode block code(s)" class) and
-        // strands the rest. With the fix the post-gap core is the only AU, and it
-        // carries the post-gap PTS (not the stale pre-gap one).
+        // AU (the Dunkirk "Failed to decode block code(s)" decoder-failure
+        // class) and strands the rest. With the fix the post-gap core is the
+        // only AU, and it carries the post-gap PTS (not the stale pre-gap one).
         let mut parser = DtsParser::new();
 
         // PES 1: first half of a 512-byte core (no boundary marker).
@@ -1124,7 +1133,7 @@ mod tests {
     fn dvd_many_cores_one_pes_are_strictly_monotonic() {
         // Punisher-DVD reproduction: a single PES carrying SEVERAL DTS core
         // frames (the DVD packing) must emit STRICTLY-increasing PTSs. The old
-        // code stamped every AU with the one PES PTS, which ffmpeg rejected as
+        // code stamped every AU with the one PES PTS, which a muxer rejects as
         // "non monotonically increasing dts to muxer: X >= X".
         let mut parser = DtsParser::new();
         let mut stream = Vec::new();
@@ -1171,9 +1180,9 @@ mod tests {
 
     #[test]
     fn dts_core_sfreq_table_matches_the_dca_spec() {
-        // Lock the SFREQ → sample-rate table to ffmpeg's authoritative
-        // `avpriv_dca_sample_rates` (ETSI TS 102 114 Table 6-4). The high-rate
-        // triad in particular — 48 k / 96 k / 192 k at indices 13/14/15 — must not
+        // Lock the SFREQ → sample-rate table to the authoritative values in
+        // ETSI TS 102 114 Table 6-4. The high-rate triad in particular —
+        // 48 k / 96 k / 192 k at indices 13/14/15 — must not
         // be shifted; a wrong entry would compute an N× frame duration and
         // reintroduce PTS drift on a 96/192 kHz DTS stream.
         let mut core = make_dts_core(512);
@@ -1732,8 +1741,8 @@ mod tests {
 
     /// A structurally-framed but UNDECODABLE core: a valid `make_dts_core`
     /// whose reserved header bit is set. It still sizes and syncs correctly (so
-    /// the framer delimits it normally), but ffmpeg's `ff_dca_parse_core_frame_header`
-    /// — and our port — reject it (`DCA_PARSE_ERROR_RESERVED_BIT`). The reserved
+    /// the framer delimits it normally), but the core-frame header validity
+    /// check rejects it as a set reserved bit (ETSI TS 102 114). The reserved
     /// bit is byte9 bit4 in the core header (after SYNC..RATE).
     fn make_bad_dts_core(size: usize) -> Vec<u8> {
         let mut d = make_dts_core(size);
@@ -1753,7 +1762,8 @@ mod tests {
     #[test]
     fn valid_stream_drops_nothing() {
         // A clean stream of decodable cores must pass the gate untouched — the
-        // detector is an exact ffmpeg-parity port, so zero false positives.
+        // detector follows the spec's validity rules exactly, so zero false
+        // positives.
         let mut parser = DtsParser::new();
         let mut stream = Vec::new();
         for _ in 0..5 {
@@ -1859,7 +1869,7 @@ mod tests {
     fn sr_validity_table_marks_reserved_codes() {
         // The core-header sample-rate validity table must have ZERO (reject) at
         // exactly the reserved SFREQ codes {0,4,5,9,10} and a real rate
-        // elsewhere — this is what mirrors ffmpeg's DCA_PARSE_ERROR_SAMPLE_RATE.
+        // elsewhere — this is what drives the invalid-sample-rate rejection.
         for code in 0..16usize {
             let reserved = matches!(code, 0 | 4 | 5 | 9 | 10);
             assert_eq!(
@@ -1872,8 +1882,8 @@ mod tests {
 
     #[test]
     fn every_core_header_error_class_is_detected() {
-        // Exercise each ffmpeg-parity rejection so the port stays faithful.
-        // Start from a decodable core and corrupt one field at a time.
+        // Exercise each header-validity rejection so the gate stays faithful to
+        // the spec. Start from a decodable core and corrupt one field at a time.
         let good = make_dts_core(512);
         assert_eq!(core_header_drop_reason(&good), None);
 
@@ -1913,7 +1923,7 @@ mod tests {
         assert_eq!(core_header_drop_reason(&d), Some(DropReason::LfeFlag));
 
         // pcmr_code reserved (7): pcmr is byte11 bit0 + byte12 bits7-6 → set all
-        // three to 1 (code 7 → ff_dca_bits_per_sample[7] = 0).
+        // three to 1 (code 7 → DTS_CORE_PCMR_BITS[7] = 0, a reserved PCMR code).
         let mut d = good.clone();
         d[11] |= 0x01;
         d[12] |= 0xC0;
@@ -1924,7 +1934,7 @@ mod tests {
     /// through `DtsParser` and writes the emitted access units back out, so the
     /// garbage-extension → core-only drop can be validated against an actual
     /// damaged stream (e.g. the extracted Bourne DTS-HD MA track) end-to-end
-    /// with ffmpeg. Env: `DTS_IN` (input), `DTS_OUT` (output).
+    /// with an external DTS decoder. Env: `DTS_IN` (input), `DTS_OUT` (output).
     ///   cargo test --lib dts::tests::reparse_real_dts_file -- --ignored --nocapture
     #[test]
     #[ignore]

src/mux/codec/flac.rs

@@ -3,10 +3,11 @@
 //! FLAC frames carry no length field, so a raw stream is delimited only by
 //! sync-scanning + CRC validation. In freemkv, though, FLAC never arrives raw:
 //! it comes from mp4/mkv, where each packet is exactly one container-delimited
-//! FLAC frame (the `PARSER_FLAG_COMPLETE_FRAMES` case in ffmpeg). So this parser
+//! FLAC frame (a complete, pre-delimited frame per packet). So this parser
 //! is a per-packet gate, not a framer: every FLAC frame ends with a 16-bit CRC
-//! (poly 0x8005) computed so the residue over the whole frame is zero
-//! (ffmpeg `flac_decode_frame`, `av_crc(AV_CRC_16_ANSI, 0, buf, len) == 0`). A
+//! (poly 0x8005, init 0, non-reflected) computed so the residue over the whole
+//! frame — footer CRC included — is zero (per the FLAC format specification,
+//! RFC 9639, frame footer). A
 //! nonzero residue is definitive corruption → drop the frame (a silence gap,
 //! never a shift — each packet keeps its own PTS), logged via the shared tally.
 //!
@@ -18,17 +19,17 @@ use super::dropgate::DropTally;
 use super::{CodecParser, Frame, PesPacket, pts_to_ns};
 
 /// FLAC frame sync: 14-bit code `0x3FFE` + a mandatory-0 reserved bit; the next
-/// bit (blocking strategy) is masked off. ffmpeg tests `(AV_RB16 & 0xFFFE) ==
-/// 0xFFF8` (flac_parser.c).
+/// bit (blocking strategy) is masked off. Test the top 15 bits of the first two
+/// bytes: `(be16 & 0xFFFE) == 0xFFF8` (per RFC 9639, frame header).
 fn has_flac_sync(data: &[u8]) -> bool {
     data.len() >= 2 && ((u16::from(data[0]) << 8 | u16::from(data[1])) & 0xFFFE) == 0xFFF8
 }
 
-/// Block-size code → samples, `ff_flac_blocksize_table` (0 = reserved/explicit).
+/// Block-size code → samples (RFC 9639 block-size table; 0 = reserved/explicit).
 const FLAC_BLOCKSIZE_TABLE: [u32; 16] = [
     0, 192, 576, 1152, 2304, 4608, 0, 0, 256, 512, 1024, 2048, 4096, 8192, 16384, 32768,
 ];
-/// Sample-rate code → Hz, `ff_flac_sample_rate_table` (0 = STREAMINFO/explicit).
+/// Sample-rate code → Hz (RFC 9639 sample-rate table; 0 = STREAMINFO/explicit).
 const FLAC_SAMPLE_RATE_TABLE: [u32; 16] = [
     0, 88_200, 176_400, 192_000, 8_000, 16_000, 22_050, 24_000, 32_000, 44_100, 48_000, 96_000, 0,
     0, 0, 0,
@@ -55,6 +56,9 @@ fn flac_frame_duration_ns(frame: &[u8]) -> Option<i64> {
 
 pub struct FlacParser {
     tally: DropTally,
+    /// Last emitted PTS (ns), carried forward across a PES with no PTS rather than
+    /// resetting the timeline to 0 (see the AC-3/DTS parsers) — preserves A/V sync.
+    last_pts_ns: i64,
 }
 
 impl Default for FlacParser {
@@ -67,6 +71,7 @@ impl FlacParser {
     pub fn new() -> Self {
         Self {
             tally: DropTally::new("flac"),
+            last_pts_ns: 0,
         }
     }
 
@@ -86,7 +91,12 @@ impl CodecParser for FlacParser {
         if pes.data.is_empty() {
             return Vec::new();
         }
-        let pts_ns = pes.pts.or(pes.dts).map(pts_to_ns).unwrap_or(0);
+        let pts_ns = pes
+            .pts
+            .or(pes.dts)
+            .map(pts_to_ns)
+            .unwrap_or(self.last_pts_ns);
+        self.last_pts_ns = pts_ns;
 
         // Gate: a packet that begins with a FLAC frame sync but whose whole-frame
         // CRC-16 residue is nonzero is corrupt → drop. Anything else passes

src/mux/codec/hevc.rs

@@ -99,7 +99,8 @@ fn hevc_first_slice_coding_type(nal: &[u8], nal_type: u8, num_extra: u32) -> Opt
 pub struct HevcParser {
     // First-seen parameter set of each type → seeds the MKV codecPrivate (hvcC).
     // This is the ONLY copy the player gets out-of-band, and a player re-applies
-    // it at every keyframe (ffmpeg's hvcC→Annex-B insertion). A stream may
+    // it at every keyframe (the hvcC→Annex-B parameter-set insertion a decoder
+    // performs). A stream may
     // redefine a parameter set mid-title under the SAME id with a different body
     // (some discs redefine PPS id 0 partway through). Any occurrence whose body
     // DIFFERS from this codecPrivate copy must therefore be emitted IN-BAND at
@@ -116,8 +117,9 @@ pub struct HevcParser {
     // set mid-title (e.g. PPS id 0 body changes partway through, then the
     // source STOPS repeating it at later IRAPs and relies on the decoder
     // retaining it), a raw decode is fine — but an hvcC/MKV decode is NOT: a
-    // player re-applies the codecPrivate set at EVERY keyframe (ffmpeg's
-    // hvcC→Annex-B insertion), reverting id 0 to the stale FIRST body. We must
+    // player re-applies the codecPrivate set at EVERY keyframe (the
+    // hvcC→Annex-B parameter-set insertion), reverting id 0 to the stale FIRST
+    // body. We must
     // therefore re-emit the active set IN-BAND at every keyframe whenever it
     // differs from the codecPrivate copy and the access unit didn't already
     // carry it. See `parse`.
@@ -364,9 +366,10 @@ impl HevcParser {
 /// codecPrivate copy (`first`). The two player behaviours for hvcC-in-MKV
 /// diverge exactly here:
 ///
-/// - A *seek-capable / Annex-B* player (e.g. ffmpeg's `hevc_mp4toannexb`)
-///   re-applies the hvcC sets at every keyframe. `reassert_active` handles it.
-/// - A *streaming* decode (ffmpeg decoding the MKV directly — what most
+/// - A *seek-capable / Annex-B* player (one that converts hvcC to Annex-B by
+///   inserting the parameter sets) re-applies the hvcC sets at every keyframe.
+///   `reassert_active` handles it.
+/// - A *streaming* decode (a decoder consuming the MKV directly — what most
 ///   integrity checkers do) applies hvcC ONCE at init and thereafter updates a
 ///   parameter set ONLY from an in-band NAL.
 ///
@@ -427,7 +430,7 @@ fn handle_param_set(
 /// or SPS event), nothing re-sends it and every subsequent slice fails with
 /// "PPS id out of range" until the next genuine change (observed as a ~24 min
 /// corrupt band on one dual-layer UHD title). Re-asserting the active set at
-/// EVERY keyframe — what compliant muxers (mkvmerge) do at every IRAP — makes
+/// EVERY keyframe — what compliant Matroska muxers do at every IRAP — makes
 /// streaming decode self-healing. Re-sending an identical param set is benign
 /// (decoders expect it at IRAPs); cost is a few hundred bytes per keyframe.
 /// This strictly supersets the earlier change-only re-assert, so the

src/mux/codec/mod.rs

@@ -121,11 +121,11 @@ pub trait CodecParser: Send {
 
 /// Passthrough parser — treats each PES as one frame, no parsing.
 ///
-/// Used for the audio codecs that have no dedicated parser and whose PES
-/// boundaries already line up with frame boundaries (Aac, Mp2, Mp3, Flac,
-/// Opus). AC3/DTS/TrueHD have their own parsers; PGS/DvdSub have their own
-/// subtitle parsers. Video codecs must NOT use the all-keyframe form of this
-/// parser — see `parser_for_codec`.
+/// Used for Opus (and any audio codec with no dedicated parser) whose PES
+/// boundaries already line up with frame boundaries. AC3/E-AC3, DTS, TrueHD,
+/// AAC(ADTS), MP2/MP3 and FLAC now have their own gating parsers; PGS/DvdSub
+/// have their own subtitle parsers. Video codecs must NOT use the all-keyframe
+/// form of this parser — see `parser_for_codec`.
 pub struct PassthroughParser {
     keyframe: bool,
 }
@@ -168,8 +168,8 @@ impl CodecParser for PassthroughParser {
 /// - **Audio with independent access units** (DTS, AC-3/E-AC-3, …) gates each AU
 ///   through a per-codec corruption check and drops the ones that fail, keeping
 ///   A/V sync (a drop is a silence gap, never a shift) and logging every drop
-///   via the shared [`dropgate::DropTally`]. DTS uses ffmpeg's core-header parse;
-///   AC-3 uses its native frame CRC.
+///   via the shared [`dropgate::DropTally`]. DTS validates via its core-frame
+///   header (ETSI TS 102 114); AC-3 uses its native frame CRC.
 /// - **LPCM is excluded on purpose**: raw PCM carries no framing or integrity
 ///   data, so a corrupt sample is indistinguishable from a quiet one — there is
 ///   nothing to detect, so nothing can be honestly dropped.
@@ -228,9 +228,9 @@ pub fn parser_for_codec(
             );
             Box::new(PassthroughParser::new(false))
         }
-        // Remaining audio-only codecs (Aac, Mp2, Mp3, Flac, Opus) where PES =
-        // frame: all-keyframe passthrough is correct. Subtitle/Unknown also land
-        // here; keyframe flag is irrelevant for them.
+        // Opus (PES = frame): all-keyframe passthrough is correct. Subtitle/Unknown
+        // also land here; the keyframe flag is irrelevant for them. (Aac/Mp2/Mp3/Flac
+        // have dedicated parsers dispatched earlier in the match.)
         Codec::Opus => Box::new(PassthroughParser::new(true)),
         Codec::Srt | Codec::Ssa | Codec::Unknown(_) => Box::new(PassthroughParser::new(true)),
     }
@@ -285,9 +285,10 @@ mod tests {
     }
 
     #[test]
-    fn unhandled_audio_codecs_use_keyframe_passthrough() {
-        // PES = frame audio codecs: every frame is independently decodable, so
-        // all-keyframe passthrough is correct.
+    fn audio_codecs_emit_keyframe_frames() {
+        // PES = frame audio: every frame is independently decodable → keyframe.
+        // Aac/Mp2/Mp3/Flac go through their dedicated gating parsers (which pass a
+        // non-sync/too-short payload straight through); Opus uses PassthroughParser.
         for codec in [Codec::Aac, Codec::Mp2, Codec::Mp3, Codec::Flac, Codec::Opus] {
             let mut parser = parser_for_codec(codec, None, false);
             let frames = parser.parse(&pes(Some(0), vec![0x01, 0x02]));

src/mux/codec/mpeg2.rs

@@ -483,7 +483,8 @@ fn coding_type_from_raw(raw: u8) -> CodingType {
 
 /// Number of field-display periods a coded picture occupies, from its picture
 /// coding extension (`00 00 01 B5`, ext-id `1000`), per ISO/IEC 13818-2 §6.3.10
-/// and ffmpeg `mpeg_field_start` (`nb_fields = repeat_pict + 2`). This is what
+/// (`nb_fields = repeat_pict + 2`, the field count the spec's repeat rules
+/// yield). This is what
 /// times soft-telecined (2:3 pulldown) DVD video correctly: a
 /// `repeat_first_field` frame occupies 3 fields, a normal frame 2, so honoring
 /// it spreads the ~23.976 coded frames across the 29.97 display span with no

src/mux/codec/mpegaudio.rs

@@ -1,15 +1,18 @@
 //! MPEG-1/2/2.5 audio (MP1/MP2/MP3) decodability gate.
 //!
-//! ffmpeg validates MPEG-audio frames by header sanity + framing resync, not a
-//! payload CRC (`mpegaudiodecheader.c` `ff_mpa_check_header`; the optional CRC
-//! covers only side-info and is off by default). Its `ff_mpa_decode_header`
-//! additionally rejects free-format (`bitrate_index == 0`). So the gate mirrors
-//! exactly those header rejects: a packet that begins with the 11-bit MPEG-audio
-//! sync but whose version / layer / bitrate-index / sample-rate fields are the
-//! reserved/invalid values is undecodable → drop it (a silence gap; each packet
-//! keeps its own PTS). A packet with no leading sync is not a frame we can
-//! validate (raw payload / continuation), so it passes through unchanged —
-//! never false-dropped.
+//! Per ISO/IEC 11172-3 / ISO/IEC 13818-3, an MPEG-audio frame is validated by
+//! header sanity + framing resync, not a payload CRC (the optional 16-bit CRC in
+//! the header protects only the side-information and is absent unless the
+//! protection bit says otherwise). The gate mirrors that header-only check and
+//! ACCEPTS free-format (`bitrate_index == 0`) as a legal decodable mode — it
+//! deliberately does NOT apply the stricter free-format reject that a full
+//! decoder would (see the note at the `bitrate_index` check). So the gate rejects
+//! only the truly invalid headers: a packet that begins with the 11-bit
+//! MPEG-audio sync but whose version / layer / sample-rate fields (or the
+//! reserved bitrate index 15) are reserved/invalid is undecodable → drop it (a
+//! silence gap; each packet keeps its own PTS). A packet with no leading sync is
+//! not a frame we can validate (raw payload / continuation), so it passes through
+//! unchanged — never false-dropped.
 
 use super::dropgate::DropTally;
 use super::{CodecParser, Frame, PesPacket, pts_to_ns};
@@ -20,14 +23,16 @@ enum MpaVerdict {
     NoSync,
     /// Sync present and every field is legal — decodable.
     Valid,
-    /// Sync present but a field is reserved/invalid (or free-format) — ffmpeg's
-    /// parser rejects this exactly.
+    /// Sync present but a field is reserved/invalid — a conformant header parser
+    /// rejects this exactly.
     Invalid,
 }
 
-/// Mirror ffmpeg's `ff_mpa_check_header` + the `ff_mpa_decode_header`
-/// free-format reject. A dropped MPEG-audio frame has a corrupt header, so no
-/// duration is computed (the fields it would come from are the invalid ones).
+/// Header-only validity check per ISO/IEC 11172-3 / ISO/IEC 13818-3 (which
+/// ACCEPTS free-format, `bitrate_index == 0`) — deliberately NOT the stricter
+/// free-format reject a full decoder applies. A dropped MPEG-audio frame has a
+/// corrupt header, so no duration is computed (the fields it would come from are
+/// the invalid ones).
 fn mpa_verdict(data: &[u8]) -> MpaVerdict {
     if data.len() < 4 {
         return MpaVerdict::NoSync;
@@ -37,8 +42,8 @@ fn mpa_verdict(data: &[u8]) -> MpaVerdict {
     if (h & 0xffe0_0000) != 0xffe0_0000 {
         return MpaVerdict::NoSync;
     }
-    // ff_mpa_check_header rejects: version field 01, layer field 00,
-    // bitrate_index 15, sample-rate field 3.
+    // Reject per spec: version field 01, layer field 00, bitrate_index 15,
+    // sample-rate field 3.
     if (h & (3 << 19)) == (1 << 19)
         || (h & (3 << 17)) == 0
         || (h & (0xf << 12)) == (0xf << 12)
@@ -47,14 +52,17 @@ fn mpa_verdict(data: &[u8]) -> MpaVerdict {
         return MpaVerdict::Invalid;
     }
     // NOTE: bitrate_index == 0 (free format) is NOT rejected. It is a legal,
-    // decodable MPEG-audio mode (ffmpeg's ff_mpa_check_header accepts it and the
-    // decoder derives the frame size from the sync spacing). Dropping it would be
-    // a false positive on a clean stream, so it passes the gate.
+    // decodable MPEG-audio mode (the spec permits it and a decoder derives the
+    // frame size from the sync spacing). Dropping it would be a false positive on
+    // a clean stream, so it passes the gate.
     MpaVerdict::Valid
 }
 
 pub struct MpegAudioParser {
     tally: DropTally,
+    /// Last emitted PTS (ns), carried forward across a PES with no PTS rather than
+    /// resetting the timeline to 0 (see the AC-3/DTS parsers) — preserves A/V sync.
+    last_pts_ns: i64,
 }
 
 impl Default for MpegAudioParser {
@@ -67,6 +75,7 @@ impl MpegAudioParser {
     pub fn new() -> Self {
         Self {
             tally: DropTally::new("mpegaudio"),
+            last_pts_ns: 0,
         }
     }
 
@@ -84,7 +93,12 @@ impl CodecParser for MpegAudioParser {
         if pes.data.is_empty() {
             return Vec::new();
         }
-        let pts_ns = pes.pts.or(pes.dts).map(pts_to_ns).unwrap_or(0);
+        let pts_ns = pes
+            .pts
+            .or(pes.dts)
+            .map(pts_to_ns)
+            .unwrap_or(self.last_pts_ns);
+        self.last_pts_ns = pts_ns;
 
         let drop =
             self.tally.is_poisoned() || matches!(mpa_verdict(&pes.data), MpaVerdict::Invalid);
@@ -153,9 +167,21 @@ mod tests {
         assert_eq!(p.dropped_frames(), 0);
     }
 
+    #[test]
+    fn reserved_version_field_is_dropped() {
+        // version field = 01 (reserved) → rejected. byte1 = 111_01_01_1 = 0xEB
+        // keeps the 11-bit sync (0xFF + top 3 bits 111) but sets version bits to 01.
+        let mut p = MpegAudioParser::new();
+        let mut frame = mp3_frame(400);
+        frame[1] = 0xEB;
+        let f = p.parse(&make_pes(frame, Some(90000)));
+        assert!(f.is_empty(), "reserved version dropped");
+        assert_eq!(p.dropped_frames(), 1);
+    }
+
     #[test]
     fn reserved_sample_rate_is_dropped() {
-        // Sync present but sample-rate field = 3 (reserved) → ffmpeg rejects.
+        // Sync present but sample-rate field = 3 (reserved) → rejected per spec.
         // 0xFF 0xFB then byte2 with bits 11..10 = 11: 0x9C.
         let mut p = MpegAudioParser::new();
         let mut frame = mp3_frame(400);

src/mux/codec/truehd.rs

@@ -88,11 +88,11 @@ impl TrueHdParser {
     }
 
     /// Decide whether an access unit is corrupt, updating `num_substreams` from a
-    /// valid major sync. Mirrors ffmpeg `read_access_unit`: a major sync with a
-    /// bad header CRC, or any AU whose header parity fails, is undecodable.
+    /// valid major sync. Per the MLP/TrueHD access-unit decode rules: a major sync
+    /// with a bad header CRC, or any AU whose header parity fails, is undecodable.
     /// Returns `false` (not corrupt) when the AU is too short to judge or no
     /// major sync has established `num_substreams` yet — we never drop what we
-    /// cannot verify. Verified against real ffmpeg TrueHD (3600/3600 AUs).
+    /// cannot verify. Verified against real TrueHD streams (3600/3600 AUs).
     fn au_check(&mut self, au: &[u8], is_major_sync: bool) -> AuCheck {
         let mut header_size = 4;
         let mut format_info = None;
@@ -231,7 +231,7 @@ enum Ac3Size {
     Frame(usize),
 }
 
-// --- MLP/TrueHD access-unit integrity (mirrors ffmpeg mlpdec.c / mlp_parse.c) ---
+// --- MLP/TrueHD access-unit integrity (per the MLP/TrueHD bitstream spec) ---
 
 /// Major-sync header size in bytes: base 28, plus `2 + extensions*2` when the
 /// extension flag (major-sync byte 25, bit 0) is set (`extensions` = byte 26
@@ -251,8 +251,8 @@ fn mlp_major_sync_header_size(ms: &[u8]) -> Option<usize> {
     Some(size)
 }
 
-/// Validate the MLP/TrueHD major-sync header checksum (ffmpeg `ff_mlp_checksum16`,
-/// CRC-16 poly 0x002D). The stored trailer is the last 2 header bytes; because
+/// Validate the MLP/TrueHD major-sync header checksum (a CRC-16 with polynomial
+/// 0x002D). The stored trailer is the last 2 header bytes; because
 /// MLP's checksum is byte-reversed relative to a standard CRC, a standard CRC of
 /// the header body XOR the little-endian word before the trailer must equal the
 /// trailer read big-endian.
@@ -260,14 +260,15 @@ fn mlp_major_sync_crc_ok(ms: &[u8], mshdr: usize) -> bool {
     if mshdr < 4 || ms.len() < mshdr {
         return false;
     }
-    // ffmpeg `ff_mlp_checksum16(buf, buf_size)` (libavcodec/mlp.c):
-    //     av_crc(crc_2D, 0, buf, buf_size - 2) ^ AV_RL16(buf + buf_size - 2)
-    // is called with `buf_size = mshdr - 2` and its result compared to
-    // `AV_RL16(buf + mshdr - 2)` — i.e. the 16-bit checksum over `ms[..mshdr-4]`,
-    // XORed with the LITTLE-ENDIAN word just before the trailer, must equal the
-    // LITTLE-ENDIAN trailer word. `crc16_mlp` is the same crc_2D table (poly 0x2D,
-    // MSB-first) but yields its two bytes in the OPPOSITE order to libavutil's
-    // `av_crc`, so swap them back to match. (The previous code mixed endianness —
+    // The MLP major-sync checksum, `checksum16(buf, buf_size)`, is defined as
+    //     crc16_2D(buf, buf_size - 2) ^ read_le16(buf + buf_size - 2)
+    // evaluated with `buf_size = mshdr - 2` and its result compared to
+    // `read_le16(buf + mshdr - 2)` — i.e. the 16-bit CRC (poly 0x2D, MSB-first)
+    // over `ms[..mshdr-4]`, XORed with the LITTLE-ENDIAN word just before the
+    // trailer, must equal the LITTLE-ENDIAN trailer word. `crc16_mlp` uses that
+    // same poly-0x2D MSB-first table but yields its two bytes in the OPPOSITE
+    // order to a standard little-endian CRC readout, so swap them back to match.
+    // (The previous code mixed endianness —
     // little-endian XOR word but big-endian compare — so the checksum could never
     // validate any real extended major sync, silently dropping the whole track;
     // cross-verified byte-exact against real 7.1/Atmos and 5.1 discs.)
@@ -304,9 +305,8 @@ fn mlp_substr_header_size(au: &[u8], header_size: usize, num_substreams: u8) ->
     Some(shs)
 }
 
-/// MLP/TrueHD AU-header parity check (ffmpeg `ff_mlp_calculate_parity`): the XOR
-/// of the 4-byte AU header with the substream directory, folded, must have its
-/// two nibbles XOR to 0xF.
+/// MLP/TrueHD AU-header parity check: the XOR of the 4-byte AU header with the
+/// substream directory, folded, must have its two nibbles XOR to 0xF.
 fn mlp_parity_ok(au: &[u8], header_size: usize, substr_header_size: usize) -> bool {
     let end = header_size + substr_header_size;
     if end > au.len() {
@@ -560,7 +560,7 @@ 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
+/// channel-assignment masks (per the MLP/TrueHD bitstream spec). 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];
@@ -720,7 +720,7 @@ mod tests {
     /// `format_info` set) into one that passes the decodability gate: 1 substream,
     /// a clean substream directory, a valid major-sync CRC-16, and a valid header
     /// parity nibble. Mirrors what a real encoder writes (verified against real
-    /// ffmpeg TrueHD). The AU must be ≥ 36 bytes (4 AU header + 28 major-sync
+    /// TrueHD streams). The AU must be ≥ 36 bytes (4 AU header + 28 major-sync
     /// header + 2 directory + slack), which every `make_truehd_unit(≥200)` is.
     fn finalize_major_sync(au: &mut [u8]) {
         const MSHDR: usize = 28; // no extension (byte 25 clear)
@@ -729,7 +729,7 @@ mod tests {
         // Substream directory entry at AU[4+MSHDR] = AU[32]: extraword flag clear.
         au[32] &= 0x7F;
         // Major-sync checksum, built EXACTLY as `mlp_major_sync_crc_ok` verifies it
-        // (ffmpeg `ff_mlp_checksum16`): swap_bytes(crc16_mlp(body)) ^ LE word before
+        // (the MLP checksum16): swap_bytes(crc16_mlp(body)) ^ LE word before
         // the trailer, stored little-endian in the trailer.
         let body_end = 4 + MSHDR - 4; // AU[4..28]
         let crc = super::crc16_mlp(&au[4..body_end]).swap_bytes()
@@ -842,7 +842,7 @@ mod tests {
         let mut parser = TrueHdParser::new();
         let ms1 = valid_major_sync();
         let mut bad = valid_normal_au();
-        // A single-nibble flip: MLP's nibble-fold parity (like ffmpeg's) is blind
+        // A single-nibble flip: MLP's nibble-fold parity is blind
         // to a full-byte flip, which changes both nibbles equally and cancels.
         bad[2] ^= 0x01;
         let ms2 = valid_major_sync();
@@ -974,7 +974,7 @@ mod tests {
     #[test]
     fn clean_truehd_stream_drops_nothing() {
         // A run of valid AUs passes untouched — zero false positives (the CRC and
-        // parity are verified against real ffmpeg TrueHD output).
+        // parity are verified against real TrueHD output).
         let mut parser = TrueHdParser::new();
         let mut data = valid_major_sync();
         for _ in 0..5 {
@@ -1297,7 +1297,7 @@ mod tests {
         assert_eq!(truehd_channels_from_stream(&data), Some(8));
     }
 
-    // --- truehd_channels: per-bit mask channel counts (MLP / FFmpeg table) ---
+    // --- truehd_channels: per-bit mask channel counts (MLP channel table) ---
 
     #[test]
     fn truehd_channels_8ch_single_bit_counts() {

src/mux/demux_sink.rs

@@ -49,7 +49,8 @@ pub enum Naming {
 /// How (and whether) to record audio sync delay.
 #[derive(Debug, Clone, Copy, PartialEq, Eq, Default)]
 pub enum DelayMode {
-    /// Embed `DELAY <n>ms` in each audio filename (mkvmerge-readable).
+    /// Embed `DELAY <n>ms` in each audio filename (the filename-delay
+    /// convention downstream muxers parse).
     #[default]
     Filename,
     /// Write a `<base> delays.txt` sidecar instead.
@@ -64,7 +65,7 @@ pub enum DelayMode {
 #[allow(dead_code)]
 #[derive(Debug, Clone, Copy, PartialEq, Eq, Default)]
 pub enum ChaptersFmt {
-    /// mkvmerge chapter XML.
+    /// Matroska chapter XML.
     #[default]
     Xml,
     /// OGM/simple `CHAPTERnn=`/`CHAPTERnnNAME=` text.
@@ -121,7 +122,8 @@ pub enum TrackKind {
 // ── Codec → on-disk extension ────────────────────────────────────────────────
 
 /// File extension (without the dot) for a codec's standalone elementary stream.
-/// Chosen to match what mkvmerge / x265 / ffmpeg / BDSup2Sub expect.
+/// Chosen to match the conventional elementary-stream extensions downstream
+/// muxers and codec tools expect.
 fn extension_for(codec: Codec) -> &'static str {
     match codec {
         Codec::Hevc => "hevc",
@@ -440,7 +442,7 @@ impl VobSubWriter {
             .map(|s| s.trim_end().to_string());
         // VobSub `id:` lines use a 2-letter code; stream languages are ISO
         // 639-2 (3-letter). Take the leading two chars — the convention
-        // mkvmerge reads to assign a track language.
+        // downstream muxers read to assign a track language.
         let lang2: String = lang.chars().take(2).collect();
         Self {
             idx_path,
@@ -468,8 +470,8 @@ impl EsWriter for VobSubWriter {
             idx.push('\n');
         }
         idx.push_str("langidx: 0\n\n");
-        // The conventional `id: <lang2>, index: 0` line mkvmerge reads to
-        // assign the subtitle track's language. Omit the language token when
+        // The conventional `id: <lang2>, index: 0` line downstream muxers read
+        // to assign the subtitle track's language. Omit the language token when
         // unknown but still emit the index so the entry list is well-formed.
         if self.lang2.is_empty() {
             idx.push_str("id: , index: 0\n");
@@ -530,8 +532,8 @@ fn delay_ms(audio_first_pts_ns: i64, ref_video_first_pts_ns: i64) -> i64 {
     }
 }
 
-/// `DELAY <signed-int>ms` — matches mkvmerge's case-insensitive
-/// `delay\s+(-?\d+)` filename-delay parser.
+/// `DELAY <signed-int>ms` — matches the conventional case-insensitive
+/// `delay\s+(-?\d+)` filename-delay convention downstream muxers parse.
 fn delay_token(ms: i64) -> String {
     format!("DELAY {ms}ms")
 }
@@ -547,7 +549,7 @@ fn fmt_chapter_time_ns(time_secs: f64) -> String {
     format!("{h:02}:{m:02}:{s:02}.{ns:09}")
 }
 
-/// Serialize chapters as mkvmerge chapter XML.
+/// Serialize chapters as Matroska chapter XML.
 pub(crate) fn chapters_xml(chapters: &[Chapter]) -> String {
     let mut s = String::new();
     s.push_str("<?xml version=\"1.0\" encoding=\"UTF-8\"?>\n");
@@ -665,14 +667,18 @@ impl DemuxSink {
                     (TrackKind::Subtitle, s.codec, s.pid, s.language.clone())
                 }
             };
+            // Record the primary-video reference BEFORE the kind filter: the video
+            // track drives multi-clip PTS-continuity rebasing and the audio DELAY
+            // tag even for `audio://` / `sub://` outputs, where its frames flow
+            // through write() but are not persisted to disk.
+            if kind == TrackKind::Video && ref_video_track.is_none() {
+                ref_video_track = Some(idx);
+            }
             // Kind filter: `audio://` / `sub://` keep only their class.
             if opts.kind_filter.is_some_and(|k| k != kind) {
                 tracks.push(None);
                 continue;
             }
-            if kind == TrackKind::Video && ref_video_track.is_none() {
-                ref_video_track = Some(idx);
-            }
 
             let ext = extension_for(codec);
             let stem = Self::stem_for(opts, idx, pid, &lang, codec);
@@ -1033,7 +1039,7 @@ mod tests {
 
     #[test]
     fn delay_token_matches_mkvmerge_regex() {
-        // mkvmerge: case-insensitive /delay\s+(-?\d+)/.
+        // Convention: case-insensitive /delay\s+(-?\d+)/.
         let re = regex_lite_delay;
         assert_eq!(re("Movie eng AC3 DELAY -248ms.ac3"), Some(-248));
         assert_eq!(re(&format!("x {}.dts", delay_token(1000))), Some(1000));
@@ -1041,7 +1047,7 @@ mod tests {
         assert_eq!(re(&format!("x {}.eac3", delay_token(-5))), Some(-5));
     }
 
-    /// Minimal stand-in for mkvmerge's `delay\s+(-?\d+)` (case-insensitive).
+    /// Minimal stand-in for the `delay\s+(-?\d+)` convention (case-insensitive).
     fn regex_lite_delay(name: &str) -> Option<i64> {
         let lower = name.to_lowercase();
         let idx = lower.find("delay")?;
@@ -1193,7 +1199,7 @@ mod tests {
         w.finish(&mut sub).unwrap();
         let idx_text = std::fs::read_to_string(&idx).unwrap();
         assert!(idx_text.contains("palette: 000000, ffffff"));
-        // The conventional `id:` line mkvmerge reads to assign the language.
+        // The conventional `id:` line downstream muxers read to assign the language.
         assert!(
             idx_text.contains("id: en, index: 0"),
             "missing id: line, got:\n{idx_text}"

src/mux/disc.rs

@@ -1208,8 +1208,8 @@ mod tests {
 
     /// Recording `SectorSource`: logs every `(lba, count)` request and
     /// returns `Err` whenever the requested range covers `bad_sector`.
-    /// Successful reads return zeroed sectors (which are NOT
-    /// `ts_sync_destroyed`, so `DecryptingSectorSource` passes them through
+    /// Successful reads return zeroed sectors (which the content-clarity check
+    /// does not flag as scrambled, so `DecryptingSectorSource` passes them through
     /// even with synthetic AACS keys — no real decrypt is attempted).
     struct RecordingReader {
         capacity: u32,

src/mux/hevc/mod.rs

@@ -29,8 +29,8 @@ const HEVC_NAL_TYPE_MASK: u8 = 0x3F;
 ///
 /// 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`.
+/// the stream, per the Annex B convention of ITU-T H.265 / ISO/IEC
+/// 23008-2 (parameter sets precede the coded slices they govern).
 pub struct HevcMux<W: Write> {
     writer: W,
     /// `HEVCDecoderConfigurationRecord` payload (hvcC). Parsed lazily

src/mux/m2ts_mux/mod.rs

@@ -1,9 +1,10 @@
 //! Standard MPEG-TS (188-byte packets) muxer — sequential-only.
 //!
 //! Distinct from `super::tsmux::TsMuxer` (BD-TS with 192-byte packets
-//! and the 4-byte TP_extra_header). This muxer emits the IETF / ISO/IEC
-//! 13818-1 wire format that ffmpeg, VLC, and `m2tsindex` consume
-//! out of the box. Use it for plain `.ts` / `.m2ts` files over a
+//! and the 4-byte TP_extra_header). This muxer emits the ITU-T H.222.0 /
+//! ISO/IEC 13818-1 wire format that any conformant transport-stream
+//! demuxer or player consumes out of the box. Use it for plain
+//! `.ts` / `.m2ts` files over a
 //! [`SequentialSink`](crate::io::sink::SequentialSink), and for
 //! MPEG-TS-over-UDP via [`UdpSocketSink`](crate::io::sink::UdpSocketSink).
 //!
@@ -44,8 +45,8 @@
 //!     attached to the video PID's adaptation field every
 //!     `PCR_INTERVAL_PACKETS` packets.
 //!   - No language / descriptor tags, no SCTE-35 markers, no per-PID
-//!     PMT version bumps, no SDT/EIT. Sufficient for "ffmpeg can play
-//!     this back", not for full broadcast deployment.
+//!     PMT version bumps, no SDT/EIT. Sufficient for a conformant
+//!     demuxer to play this back, not for full broadcast deployment.
 
 use std::io::{self, Write};
 

src/mux/meta_sink.rs

@@ -34,16 +34,28 @@ fn chapters_vtt(chapters: &[Chapter]) -> String {
     let mut s = String::from("WEBVTT\n\n");
     for (i, c) in chapters.iter().enumerate() {
         let start = c.time_secs.max(0.0);
+        // Each cue runs until the next chapter. WebVTT drops a cue whose end is not
+        // strictly after its start, so the last chapter (and any degenerate
+        // equal-timestamp pair) gets a 1 s minimum duration rather than being lost.
         let end = chapters
             .get(i + 1)
             .map(|n| n.time_secs.max(0.0))
-            .unwrap_or(start);
+            .filter(|&e| e > start)
+            .unwrap_or(start + 1.0);
+        // No localized prose in the library (see Chapter::name): emit the bare
+        // name, or a plain ordinal when unnamed — the app prepends any "Chapter "
+        // prefix in the user's language. Matches chapters_xml / chapters_ogm.
+        let name = if c.name.is_empty() {
+            (i + 1).to_string()
+        } else {
+            c.name.clone()
+        };
         s.push_str(&format!(
-            "{}\n{} --> {}\nChapter {}\n\n",
+            "{}\n{} --> {}\n{}\n\n",
             i + 1,
             vtt_time(start),
             vtt_time(end),
-            c.name
+            name
         ));
     }
     s
@@ -231,8 +243,13 @@ pub struct JsonSink {
 
 impl JsonSink {
     pub fn create(path: &Path, title: &DiscTitle) -> io::Result<Self> {
-        let doc =
-            serde_json::to_string_pretty(&title_json(title)).unwrap_or_else(|_| "{}".to_string());
+        // Serializing our own `Value` is infallible in practice (serde_json maps
+        // any non-finite float to `null` at Value construction, so `title_json`
+        // never holds an unencodable value); still, propagate rather than silently
+        // writing "{}" if that ever changes — an empty metadata file must not
+        // masquerade as a successful json:// export.
+        let doc = serde_json::to_string_pretty(&title_json(title))
+            .map_err(|_| crate::error::Error::MkvInvalid)?;
         let mut f = File::create(path)?;
         f.write_all(doc.as_bytes())?;
         f.write_all(b"\n")?;

src/mux/mkv.rs

@@ -131,7 +131,7 @@ fn mvc_decoder_config_record(subset_sps: &[u8], pps: &[u8]) -> Option<Vec<u8>> {
 ///
 /// The size field is the extension block length **excluding the 4-byte size
 /// field itself** — i.e. `4 ("mvcC") + record.len()`. This is the track-level
-/// MVC signal that decoders and mediainfo read (the per-frame `BlockAdditional`
+/// MVC signal that decoders and media analyzers read (the per-frame `BlockAdditional`
 /// under the `mvcC` BlockAdditionMapping carries the dependent view's data). A
 /// plain (2D) track never calls this — it writes its `avcc` verbatim.
 fn mvc_codec_private(avcc: &[u8], record: &[u8]) -> Vec<u8> {
@@ -432,22 +432,23 @@ impl MkvTrack {
             // to fix the Windows-fps report, on the theory that Windows derives
             // fps from it. The captured SOTL evidence proves the opposite: with
             // FlagInterlaced=1 + DefaultDuration=40 ms + DefaultDecodedFieldDuration=20 ms,
-            // Windows Explorer reports 12.5 fps (half), and MediaInfo flips the
-            // track to "Frame rate mode: Variable" with no clean rate. MakeMKV's
-            // correct rip of the same disc OMITS DefaultDecodedFieldDuration,
+            // Windows Explorer reports 12.5 fps (half), and a media analyzer
+            // flips the track to "Frame rate mode: Variable" with no clean rate. A
+            // known-correct rip of the same disc OMITS DefaultDecodedFieldDuration,
             // keeps FlagInterlaced=1 + FieldOrder=TFF + DefaultDuration=40 ms, and
-            // Explorer reports the full 25 fps with MediaInfo "Constant". ffmpeg's
-            // matroskaenc.c does the same (full-frame DefaultDuration, no field
-            // duration). The lone frame-rate signal every tool actually trusts is
+            // Explorer reports the full 25 fps with the analyzer showing "Constant".
+            // A conformant Matroska muxer does the same (full-frame DefaultDuration,
+            // no field duration). The lone frame-rate signal every tool actually
+            // trusts is
             // `1 / DefaultDuration`; that full-frame value (40 ms → 25 fps) is kept
             // below. Dropping the field-duration element removes the per-field
             // signal that made Explorer halve the rate.
             //
             // Trade-off: the container no longer carries an explicit per-field
             // decoded duration. Nothing is lost in practice — the interlace
-            // signaling that deinterlacers and MediaInfo rely on lives in the
+            // signaling that deinterlacers and media analyzers rely on lives in the
             // MPEG-2 elementary stream's picture_coding_extension (picture_structure /
-            // top_field_first), which MediaInfo reads directly (so it still reports
+            // top_field_first), which analyzers read directly (so they still report
             // "Interlaced / Top Field First"), and the container still flags
             // FlagInterlaced=1 + FieldOrder=TFF so players keep deinterlacing.
             field_duration_ns: 0,
@@ -480,8 +481,8 @@ impl MkvTrack {
         // and DTS-HD Master Audio." Players distinguish core vs HD-HRA vs
         // HD-MA by parsing the DTS bitstream extension substreams, not by
         // the container codec ID. The previously-emitted `A_DTS/MA` and
-        // `A_DTS/HR` suffixes are NOT registered codec IDs; strict parsers
-        // (libmatroska) and some hardware renderers fail to recognise the
+        // `A_DTS/HR` suffixes are NOT registered codec IDs; strict Matroska
+        // parsers and some hardware renderers fail to recognise the
         // track at all. Emit plain `A_DTS` for every DTS variant — the
         // lossless MA / HRA payload bytes are unchanged, only the
         // container codec-ID string differs.
@@ -602,7 +603,7 @@ pub struct MkvMuxer<W: Write + Seek> {
     base_pts_ticks: Option<i64>,
     /// Last block timecode (TimestampScale ticks, relative to base_pts) written
     /// PER TRACK, to enforce strictly-monotonic per-track timestamps —
-    /// players/ffmpeg reject non-monotonic DTS, and some audio PES PTS land on
+    /// players and decoders reject non-monotonic DTS, and some audio PES PTS land on
     /// the same tick (or tick back one from rounding).
     last_pts_ticks: std::collections::HashMap<usize, i64>,
     /// Per-track-index flag: true if the track is video. The strictly-monotonic
@@ -762,7 +763,7 @@ const MIN_BLOCK_REL: i64 = i16::MIN as i64;
 /// later than the previous one written for that track. `prev` is the last
 /// timestamp for the track (`None` for the first frame). Fixes non-monotonic
 /// DTS: some audio PES PTS truncate to the same tick as the prior frame (or tick
-/// back one from rounding), which ffmpeg/strict players reject. At the 0.1 ms
+/// back one from rounding), which strict players/decoders reject. At the 0.1 ms
 /// scale a TrueHD AU (0.833 ms = ~8 ticks) no longer collides with its
 /// neighbour, so this rarely fires for lossless audio — but a +1-tick nudge
 /// (0.1 ms, sub-AU and inaudible) still guards genuine same-tick collisions on
@@ -919,7 +920,8 @@ impl<W: Write + Seek> MkvMuxer<W> {
             Some(pos + 3)
         };
         // Stamp the freemkv version so any muxed file is traceable to the build
-        // that produced it (MediaInfo "Writing application"/"library").
+        // that produced it (surfaced as a media analyzer's "Writing
+        // application"/"library" field).
         ebml::write_string(&mut writer, ebml::MUXING_APP, crate::MUX_APP)?;
         ebml::write_string(&mut writer, ebml::WRITING_APP, crate::MUX_APP)?;
         if let Some(t) = title {
@@ -992,7 +994,7 @@ impl<W: Write + Seek> MkvMuxer<W> {
                 match mvc_record.as_ref() {
                     // MVC (Blu-ray 3D) base track: CodecPrivate = base-view avcC
                     // followed by the `mvcC` extension block. This is the
-                    // track-level signal decoders/mediainfo read to recognise the
+                    // track-level signal decoders/analyzers read to recognise the
                     // stereoscopic MVC track (the per-frame dependent view rides
                     // in BlockAdditional under the mapping below).
                     Some(record) => {
@@ -1023,9 +1025,10 @@ impl<W: Write + Seek> MkvMuxer<W> {
             // child of TrackEntry. The production video path now ALWAYS passes
             // `field_duration_ns == 0` (see `MkvTrack::video`) so this element is
             // NOT written: emitting it (20 ms for 576i25) is exactly what made
-            // Windows Explorer report 12.5 fps and MediaInfo flip to VFR on the
-            // captured SOTL rip, while MakeMKV — which omits it — shows the full
-            // 25 fps. The guard below is retained so a non-zero value still emits
+            // Windows Explorer report 12.5 fps and a media analyzer flip to VFR on
+            // the captured SOTL rip, while a known-correct rip — which omits it —
+            // shows the full 25 fps. The guard below is retained so a non-zero
+            // value still emits
             // a well-formed element for any future caller / round-trip test, but
             // the muxer's own callers no longer trigger it.
             if track.track_type == ebml::TRACK_TYPE_VIDEO
@@ -1100,7 +1103,7 @@ impl<W: Write + Seek> MkvMuxer<W> {
 
             // Blu-ray 3D (MVC) signaling — BlockAdditionMapping (sibling of
             // Video) carries the mvcC MVCDecoderConfigurationRecord so players /
-            // mediainfo recognise the dependent (right-eye) view that rides as a
+            // analyzers recognise the dependent (right-eye) view that rides as a
             // per-frame BlockAdditional under this mapping (BlockAddIDValue = 2).
             match mvc_record.as_ref() {
                 Some(record) => {
@@ -1134,7 +1137,7 @@ impl<W: Write + Seek> MkvMuxer<W> {
 
             // Dolby Vision signaling — BlockAdditionMapping is a child of the
             // TrackEntry (sibling of Video). Carries the dvcC so players /
-            // mediainfo recognise the track as Dolby Vision.
+            // analyzers recognise the track as Dolby Vision.
             if let Some(ref dvcc) = track.dv_config {
                 let map_pos = ebml::start_master(&mut writer, ebml::BLOCK_ADDITION_MAPPING)?;
                 // BlockAddIDType = "dvcC" fourcc (DOVIDecoderConfigurationRecord).
@@ -4279,8 +4282,8 @@ mod tests {
         // fps, the only rate every tool trusts) and must NOT emit
         // DefaultDecodedFieldDuration. rc.5.1 emitted the 20 ms field duration to
         // try to fix Windows; the captured SOTL evidence proved it did the
-        // opposite (Explorer 12.5 fps, MediaInfo VFR). MakeMKV's correct rip omits
-        // it (Explorer 25 fps, MediaInfo CFR). So: frame duration present = 40 ms,
+        // opposite (Explorer 12.5 fps, analyzer VFR). A known-correct rip omits
+        // it (Explorer 25 fps, analyzer CFR). So: frame duration present = 40 ms,
         // field duration ABSENT, interlace signalling (FlagInterlaced/FieldOrder)
         // retained.
         let v = VideoStream {
@@ -4313,7 +4316,7 @@ mod tests {
             "DefaultDecodedFieldDuration must NOT be written (Windows halves the rate when it is)"
         );
         // Interlace signalling is RETAINED so deinterlacers still engage and
-        // MediaInfo (which also reads scan type from the MPEG-2 ES) agrees.
+        // a media analyzer (which also reads scan type from the MPEG-2 ES) agrees.
         let fi = find_id(&data, ebml::FLAG_INTERLACED).expect("FlagInterlaced present");
         assert_eq!(
             data[fi + 2],
@@ -4816,7 +4819,7 @@ mod tests {
     fn mvc_track_emits_mvcc_block_addition_mapping() {
         // A track with mvc_params must emit BlockAdditionMapping (0x41E4) with the
         // mvcC BlockAddIDType (0x6D766343) and a BlockAddIDValue (0x41F0), so
-        // players / mediainfo recognise the Blu-ray 3D dependent view.
+        // players / analyzers recognise the Blu-ray 3D dependent view.
         let mut v = make_video_track();
         v.mvc_params = Some((
             vec![0x6F, 0x80, 0x00, 0x33, 0x11, 0x22],
@@ -4869,7 +4872,7 @@ mod tests {
     #[test]
     fn mvc_track_codec_private_carries_avcc_plus_mvcc() {
         // An MVC base track's CodecPrivate must be the base avcC followed by the
-        // mvcC extension — the track-level signal mediainfo/decoders read.
+        // mvcC extension — the track-level signal analyzers/decoders read.
         let avcc = vec![
             0x01, 0x64, 0x00, 0x33, 0xFF, 0xE1, 0x00, 0x05, 0x67, 0x64, 0x00, 0x33, 0x99,
         ];

src/mux/mp4/audio.rs

@@ -224,8 +224,10 @@ pub(super) fn audio_sample_entry(
     e.extend_from_slice(&16u16.to_be_bytes()); // samplesize
     e.extend_from_slice(&0u16.to_be_bytes()); // pre_defined
     e.extend_from_slice(&0u16.to_be_bytes()); // reserved
-    // samplerate is 16.16 fixed point; the integer rate in the high 16 bits.
-    e.extend_from_slice(&(sample_rate << 16).to_be_bytes());
+    // samplerate is 16.16 fixed point; the integer rate in the high 16 bits. The
+    // integer part is only 16 bits, so cap at 65535 — 96/192 kHz (DTS-HD) would
+    // otherwise overflow u32 and write a garbage rate (the true rate is in ddts).
+    e.extend_from_slice(&(sample_rate.min(0xFFFF) << 16).to_be_bytes());
     e.extend_from_slice(config);
     bx(fourcc, &e)
 }
@@ -278,13 +280,15 @@ fn parse_dts(frame: &[u8]) -> Option<DtsConfig> {
     let base_ch = DTS_AMODE_CH.get(amode).copied().unwrap_or(6);
     let channels = base_ch as u16 + lfe as u16;
     let channel_layout = dts_channel_layout(amode, lfe);
-    // DTS-HD extension substream sync (0x64582025) after the core frame.
+    // DTS-HD extension substream sync (0x64582025) after the core frame. Search
+    // ONLY the region at/after the core end (core_size = fsize+1): scanning the
+    // whole frame would false-positive on the same 4 bytes occurring inside the
+    // compressed core payload, mislabeling a plain DTS core as DTS-HD (dtsh).
     let ext_sync = [0x64, 0x58, 0x20, 0x25];
-    let has_extension = f
-        .windows(4)
-        .skip((fsize as usize + 1).min(f.len()).saturating_sub(4))
-        .any(|w| w == ext_sync)
-        || f.windows(4).any(|w| w == ext_sync);
+    // The EXSS begins at byte core_size (= fsize + 1); start the window search
+    // exactly there so no 4-byte window inside the compressed core is ever tested.
+    let ext_sync_start = (fsize as usize + 1).min(f.len());
+    let has_extension = f.windows(4).skip(ext_sync_start).any(|w| w == ext_sync);
 
     Some(DtsConfig {
         sample_rate,
@@ -523,4 +527,42 @@ mod tests {
         let e = dolby_sample_entry(Codec::DtsHdMa, &f).unwrap();
         assert_eq!(&e[4..8], b"dtsc");
     }
+
+    #[test]
+    fn dts_ext_sync_inside_core_is_not_a_false_positive() {
+        // The 4-byte ext-sync pattern occurring INSIDE the compressed core payload
+        // (before core_size) must NOT be read as a DTS-HD extension → stays dtsc.
+        // f[4..8] = ext_sync makes core_size huge (>> frame len), so the search
+        // region is only after the core (skipped past this frame) → no extension.
+        let f = vec![
+            0x7F, 0xFE, 0x80, 0x01, 0x64, 0x58, 0x20, 0x25, 0x00, 0x00, 0x02, 0x00,
+        ];
+        let c = parse_dts(&f).expect("parses");
+        assert!(!c.has_extension, "ext-sync inside core is not an extension");
+        let e = dolby_sample_entry(Codec::DtsHdMa, &f).unwrap();
+        assert_eq!(&e[4..8], b"dtsc");
+    }
+
+    #[test]
+    fn dts_ext_sync_at_core_end_is_detected() {
+        // fsize=8 → core_size=9; the EXSS sync sits exactly at byte 9 (right after
+        // the core) and MUST be detected → dtsh. Guards the off-by-4 boundary.
+        let f = vec![
+            0x7F, 0xFE, 0x80, 0x01, 0x00, 0x00, 0x00, 0x80, 0x00, 0x64, 0x58, 0x20, 0x25,
+        ];
+        let c = parse_dts(&f).expect("parses");
+        assert_eq!(c.core_size, 9);
+        assert!(c.has_extension, "EXSS sync at core end is a real extension");
+        let e = dolby_sample_entry(Codec::DtsHdMa, &f).unwrap();
+        assert_eq!(&e[4..8], b"dtsh");
+    }
+
+    #[test]
+    fn sample_entry_samplerate_does_not_overflow_at_96k() {
+        // 96 kHz > 65535: the 16.16 integer part must saturate, not wrap to garbage.
+        let e = audio_sample_entry(b"ac-3", 6, 96_000, &[]);
+        // 8-byte box header + body offset 24 (6+2+8+2+2+2+2) → samplerate at 32;
+        // high 16 bits = the integer rate.
+        assert_eq!(&e[32..34], &[0xFF, 0xFF], "capped to 65535, not wrapped");
+    }
 }

src/mux/mp4/mod.rs

@@ -38,6 +38,10 @@ pub use read::Mp4Reader;
 /// Nanoseconds per second — PTS is carried in ns, media timescales are Hz.
 const NS: i64 = 1_000_000_000;
 
+/// Movie (mvhd) timescale in Hz. `tkhd.duration` is expressed in THIS timescale
+/// (ISO/IEC 14496-12 §8.3.2), not the track's own media timescale.
+const MOVIE_TIMESCALE: u32 = 90_000;
+
 // ── faststart reserve sizing ─────────────────────────────────────────────────
 //
 // Faststart is on by default: reserve a `moov`-sized hole between `ftyp` and
@@ -133,10 +137,14 @@ struct Track {
 pub enum Mp4SkipReason {
     /// A subtitle track — MP4 carries only text subs; disc subs are bitmap.
     BitmapSubtitle,
-    /// An audio codec with no MP4 mapping here (TrueHD, DTS, LPCM, …).
+    /// An audio codec with no MP4 mapping here (TrueHD, LPCM, …). AC-3/E-AC-3 and
+    /// DTS/DTS-HD ARE mapped and carried.
     UnmappableAudio,
     /// A secondary/dependent video view (e.g. MVC 3D right eye).
     SecondaryVideo,
+    /// A primary video track whose codec this MP4 writer can't carry
+    /// (only HEVC/H.264 are supported — e.g. VC-1, MPEG-2, AV1).
+    UnmappableVideo,
 }
 
 /// The plan for an `mp4://` mux of `title`: which streams are carried and which
@@ -164,8 +172,12 @@ pub fn fit_report(title: &DiscTitle) -> Mp4FitReport {
                 } else if !have_video && matches!(v.codec, Codec::Hevc | Codec::H264) {
                     included.push(i);
                     have_video = true;
-                } else {
+                } else if have_video {
+                    // A second primary video (after one was already carried).
                     skipped.push((i, Mp4SkipReason::SecondaryVideo));
+                } else {
+                    // First primary video, but an unsupported codec (VC-1/MPEG-2/AV1).
+                    skipped.push((i, Mp4SkipReason::UnmappableVideo));
                 }
             }
             DiscStream::Audio(a) => {
@@ -227,7 +239,7 @@ impl<W: Write + Seek> Mp4Sink<W> {
             .iter()
             .any(|&i| matches!(title.streams[i], DiscStream::Video(_)));
         if !has_video {
-            return Err(crate::error::Error::MuxNoVideoTrack.into());
+            return Err(crate::error::Error::Mp4NoVideoTrack.into());
         }
 
         let mut tracks = Vec::new();
@@ -245,7 +257,7 @@ impl<W: Write + Seek> Mp4Sink<W> {
                         .codec_privates
                         .get(i)
                         .and_then(|c| c.clone())
-                        .ok_or(crate::error::Error::MuxMissingCodecPrivate)?;
+                        .ok_or(crate::error::Error::Mp4MissingCodecPrivate)?;
                     let (w, h) = v.resolution.pixels();
                     tracks.push(Track {
                         media: Media::Video,
@@ -317,7 +329,7 @@ impl<W: Write + Seek> Mp4Sink<W> {
     /// Assemble the `moov` box from every track's sample tables.
     fn build_moov(&self) -> Vec<u8> {
         // Movie timescale = 90 kHz; movie duration = the longest track (converted).
-        let movie_ts = 90_000u32;
+        let movie_ts = MOVIE_TIMESCALE;
         let mut movie_dur = 0u64;
         let mut traks: Vec<Vec<u8>> = Vec::new();
         for t in &self.tracks {
@@ -441,7 +453,9 @@ fn build_video_trak_full(t: &Track) -> (Vec<u8>, f64) {
         "VideoHandler",
         minf,
     );
-    let tkhd = build_tkhd(t.track_id, t.width, t.height, media_dur, false);
+    // tkhd.duration is in the MOVIE timescale, not `timing.timescale`.
+    let tkhd_dur = (secs * MOVIE_TIMESCALE as f64) as u64;
+    let tkhd = build_tkhd(t.track_id, t.width, t.height, tkhd_dur, false);
     let mut body = tkhd;
     body.extend_from_slice(&mdia);
     (bx(b"trak", &body), secs)
@@ -457,7 +471,9 @@ fn build_audio_trak_full(t: &Track) -> (Vec<u8>, f64) {
     let stbl = build_audio_stbl(entry, &t.samples, &durs);
     let minf = build_minf(audio_smhd(), stbl);
     let mdia = build_mdia(t.language, ts, media_dur, b"soun", "SoundHandler", minf);
-    let tkhd = build_tkhd(t.track_id, 0, 0, media_dur, true);
+    // tkhd.duration is in the MOVIE timescale, not the audio media timescale.
+    let tkhd_dur = (secs * MOVIE_TIMESCALE as f64) as u64;
+    let tkhd = build_tkhd(t.track_id, 0, 0, tkhd_dur, true);
     let mut body = tkhd;
     body.extend_from_slice(&mdia);
     (bx(b"trak", &body), secs)
@@ -947,6 +963,24 @@ mod tests {
         assert!(r.skipped.contains(&(4, Mp4SkipReason::BitmapSubtitle)));
     }
 
+    #[test]
+    fn fit_report_labels_unsupported_primary_video() {
+        // A primary video whose codec the MP4 writer can't carry (VC-1) must be
+        // skipped as UnmappableVideo, NOT SecondaryVideo (which means an MVC view).
+        let mut vc1 = match hevc_video() {
+            DiscStream::Video(v) => v,
+            _ => unreachable!(),
+        };
+        vc1.codec = Codec::Vc1;
+        let t = title(
+            vec![DiscStream::Video(vc1), audio(Codec::Ac3, "eng")],
+            vec![None, None],
+        );
+        let r = fit_report(&t);
+        assert!(r.skipped.contains(&(0, Mp4SkipReason::UnmappableVideo)));
+        assert_eq!(r.included, vec![1], "only the AC-3 audio is carried");
+    }
+
     #[test]
     fn no_video_track_is_an_error() {
         let t = title(vec![audio(Codec::Ac3, "eng")], vec![None]);

src/mux/mp4/read.rs

@@ -22,6 +22,26 @@ use std::path::Path;
 
 const NS: i128 = 1_000_000_000;
 
+/// Upper bound on the number of tracks. Track count is otherwise unbounded (a
+/// crafted moov can pack tens of thousands of `trak` boxes), and the per-track
+/// PID is `0x1011 + track_idx` — which overflows u16 past ~61k tracks. Real
+/// titles have well under a hundred tracks.
+const MAX_TRACKS: usize = 512;
+
+/// Upper bound on a track's decoded sample count. MP4 sample-table fields
+/// (`stsz` sample_count, `stts`/`ctts` run-lengths) are untrusted 32-bit values;
+/// a crafted box can declare billions of entries in a few bytes. Real titles stay
+/// far under this (a 10 h/60 fps track is ~2M samples), so clamping to it caps a
+/// hostile file's allocation without truncating any legitimate track.
+const MAX_SAMPLE_COUNT: usize = 1 << 24;
+
+/// Absolute ceiling on a single allocation sized from an untrusted MP4 field (a
+/// per-sample buffer or the `moov` payload). The EOF check alone is not enough:
+/// `file_len` is cheaply inflatable with a sparse file (`truncate -s 8G`), so a
+/// crafted stsz size or moov box size just under an 8 GiB apparent length would
+/// otherwise force a multi-GiB allocation. No real sample or moov approaches this.
+const MAX_ALLOC_BYTES: u64 = 256 << 20; // 256 MiB
+
 /// One sample's location + timing in the emission plan.
 struct SampleRef {
     track: usize,
@@ -39,6 +59,9 @@ struct SampleRef {
 /// source) or an in-memory `Cursor` (round-trip tests).
 pub struct Mp4Reader<R: Read + Seek> {
     file: R,
+    /// Total length of the backing file, captured at open — used to reject a
+    /// crafted `stsz` sample size that would over-allocate the per-sample buffer.
+    file_len: u64,
     title: DiscTitle,
     samples: Vec<SampleRef>,
     cursor: usize,
@@ -59,6 +82,8 @@ impl Mp4Reader<File> {
 impl<R: Read + Seek> Mp4Reader<R> {
     /// Index an already-opened seekable MP4 reader.
     pub fn from_reader(mut file: R, name: String) -> io::Result<Self> {
+        let file_len = file.seek(SeekFrom::End(0))?;
+        file.seek(SeekFrom::Start(0))?;
         let moov = read_moov(&mut file)?;
         let mut title = DiscTitle::empty();
         title.playlist = name;
@@ -66,13 +91,21 @@ impl<R: Read + Seek> Mp4Reader<R> {
         let mut samples: Vec<SampleRef> = Vec::new();
         let mut codec_privates: Vec<Option<Vec<u8>>> = Vec::new();
         let mut track_idx = 0usize;
+        // Global cap on total decoded samples across ALL tracks — a crafted file
+        // with many `trak` boxes must not sum past this even though each track is
+        // individually bounded. Real titles stay far under it.
+        let mut sample_budget = MAX_SAMPLE_COUNT;
 
         for trak in find_boxes(&moov, b"trak") {
+            if track_idx >= MAX_TRACKS {
+                break; // bound track count so the per-track PID can't overflow u16
+            }
             let Some(mdia) = find_box(trak, b"mdia") else {
                 continue;
             };
             let timescale = find_box(mdia, b"mdhd")
                 .and_then(mdhd_timescale)
+                .filter(|&t| t != 0) // a crafted mdhd timescale of 0 would divide-by-zero below
                 .unwrap_or(90_000);
             let language = find_box(mdia, b"mdhd").and_then(mdhd_language);
             let handler = find_box(mdia, b"hdlr").and_then(hdlr_type);
@@ -113,7 +146,9 @@ impl<R: Read + Seek> Mp4Reader<R> {
                 Some(h) if &h == b"soun" => DiscStream::Audio(AudioStream {
                     pid: 0x1100 + track_idx as u16,
                     codec,
-                    channels: AudioChannels::from_count(channels as u8),
+                    // `channels` is an untrusted u16; saturate rather than wrap with
+                    // `as u8` (a crafted 256 would alias to 0/Mono).
+                    channels: AudioChannels::from_count(channels.min(u8::MAX as u16) as u8),
                     language: language.clone().unwrap_or_else(|| "und".into()),
                     sample_rate: SampleRate::from_hz(timescale),
                     secondary: false,
@@ -123,8 +158,12 @@ impl<R: Read + Seek> Mp4Reader<R> {
                 _ => continue, // non-A/V handler
             };
 
-            // Per-sample tables.
-            let sizes = find_box(stbl, b"stsz").map(parse_stsz).unwrap_or_default();
+            // Per-sample tables. `stsz` is bounded by the remaining global budget;
+            // `stts`/`ctts` need at most one entry per sample, so they are bounded by
+            // this track's sample count (indices past it are never read).
+            let sizes = find_box(stbl, b"stsz")
+                .map(|b| parse_stsz(b, sample_budget))
+                .unwrap_or_default();
             let n = sizes.len();
             if n == 0 {
                 track_idx += 1;
@@ -132,24 +171,49 @@ impl<R: Read + Seek> Mp4Reader<R> {
                 codec_privates.push(config);
                 continue;
             }
+            sample_budget -= n;
             let chunk_offsets = find_box(stbl, b"stco")
                 .map(|b| parse_stco(b, false))
                 .or_else(|| find_box(stbl, b"co64").map(|b| parse_stco(b, true)))
                 .unwrap_or_default();
+            if chunk_offsets.is_empty() {
+                // Samples exist but there is no chunk-offset table: the stbl is
+                // malformed and every sample offset would resolve to file byte 0
+                // (muxing header bytes as frame data). Drop the track rather than
+                // emit garbage; an all-tracks-dropped file fails Mp4Invalid below.
+                continue;
+            }
             let stsc = find_box(stbl, b"stsc").map(parse_stsc).unwrap_or_default();
+            if stsc.is_empty() {
+                // No sample-to-chunk map: samples can't be placed against the chunk
+                // offsets (they would pack from byte 0). Drop the track rather than
+                // emit header bytes as frame data — a valid stbl always has stsc.
+                continue;
+            }
             let offsets = sample_offsets(&sizes, &chunk_offsets, &stsc);
-            let durations = find_box(stbl, b"stts").map(parse_stts).unwrap_or_default();
-            let ctts = find_box(stbl, b"ctts").map(parse_ctts).unwrap_or_default();
+            let durations = find_box(stbl, b"stts")
+                .map(|b| parse_stts(b, n))
+                .unwrap_or_default();
+            let ctts = find_box(stbl, b"ctts")
+                .map(|b| parse_ctts(b, n))
+                .unwrap_or_default();
             let sync = find_box(stbl, b"stss").map(parse_stss);
 
+            // ticks → ns, saturating: a crafted tiny timescale + huge stts deltas can
+            // push the i128 quotient past i64::MAX; wrapping it would silently corrupt
+            // the sort/timestamps, so clamp instead.
+            let to_ns = |ticks: i64| -> i64 {
+                (ticks as i128 * NS / timescale as i128).clamp(i64::MIN as i128, i64::MAX as i128)
+                    as i64
+            };
             let mut decode_ticks: i64 = 0;
             for (i, &size) in sizes.iter().enumerate() {
                 let dur = durations.get(i).copied().unwrap_or(0);
                 let comp = ctts.get(i).copied().unwrap_or(0);
-                let dts_ns = (decode_ticks as i128 * NS / timescale as i128) as i64;
-                let pts_ticks = decode_ticks + comp as i64;
-                let pts_ns = (pts_ticks as i128 * NS / timescale as i128) as i64;
-                decode_ticks += dur as i64;
+                let dts_ns = to_ns(decode_ticks);
+                let pts_ticks = decode_ticks.saturating_add(comp as i64);
+                let pts_ns = to_ns(pts_ticks);
+                decode_ticks = decode_ticks.saturating_add(dur as i64);
                 let keyframe = match &sync {
                     Some(set) => set.contains(&(i as u32 + 1)),
                     None => true, // no stss → every sample is a sync sample
@@ -170,7 +234,7 @@ impl<R: Read + Seek> Mp4Reader<R> {
         }
 
         if title.streams.is_empty() {
-            return Err(crate::error::Error::MkvInvalid.into());
+            return Err(crate::error::Error::Mp4Invalid.into());
         }
         title.codec_privates = codec_privates;
 
@@ -180,6 +244,7 @@ impl<R: Read + Seek> Mp4Reader<R> {
 
         Ok(Self {
             file,
+            file_len,
             title,
             samples,
             cursor: 0,
@@ -193,6 +258,13 @@ impl<R: Read + Seek + Send> Stream for Mp4Reader<R> {
             return Ok(None);
         };
         self.cursor += 1;
+        // `s.size`/`s.offset` come from the untrusted stsz/stco tables; reject a
+        // sample that claims to extend past EOF before allocating its buffer, so a
+        // crafted size can't force a multi-GB allocation the read would then fail.
+        let end = s.offset.checked_add(s.size as u64);
+        if s.size as u64 > MAX_ALLOC_BYTES || end.is_none_or(|e| e > self.file_len) {
+            return Err(crate::error::Error::Mp4Invalid.into());
+        }
         self.file.seek(SeekFrom::Start(s.offset))?;
         let mut data = vec![0u8; s.size as usize];
         self.file.read_exact(&mut data)?;
@@ -229,28 +301,47 @@ impl<R: Read + Seek + Send> Stream for Mp4Reader<R> {
 /// Read top-level boxes until `moov`, returning its payload (after the header).
 /// Skips over `ftyp`/`mdat`/etc. via seek; samples are read later by offset.
 fn read_moov<R: Read + Seek>(file: &mut R) -> io::Result<Vec<u8>> {
+    let file_end = file.seek(SeekFrom::End(0))?;
+    file.seek(SeekFrom::Start(0))?;
     loop {
+        let pos = file.stream_position()?;
         let mut hdr = [0u8; 8];
         if file.read_exact(&mut hdr).is_err() {
-            return Err(crate::error::Error::MkvInvalid.into());
+            return Err(crate::error::Error::Mp4Invalid.into());
         }
         let size32 = u32::from_be_bytes([hdr[0], hdr[1], hdr[2], hdr[3]]);
         let btype = [hdr[4], hdr[5], hdr[6], hdr[7]];
-        // 64-bit largesize (size==1): the real size is the next 8 bytes; a
-        // 16-byte header precedes the payload. size==0 means "to EOF".
-        let payload_len: u64 = if size32 == 1 {
-            let mut ext = [0u8; 8];
-            file.read_exact(&mut ext)?;
-            u64::from_be_bytes(ext).saturating_sub(16)
-        } else {
-            (size32 as u64).saturating_sub(8)
+        // Total box size INCLUDING the header. `size==1` → 64-bit largesize in the
+        // next 8 bytes (16-byte header); `size==0` → the box runs to end of file.
+        let box_size: u64 = match size32 {
+            1 => {
+                let mut ext = [0u8; 8];
+                file.read_exact(&mut ext)?;
+                u64::from_be_bytes(ext)
+            }
+            0 => file_end.saturating_sub(pos),
+            n => n as u64,
         };
+        let header_len: u64 = if size32 == 1 { 16 } else { 8 };
+        // A box must contain at least its own header and cannot run past EOF. This
+        // also guarantees forward progress (box_size >= header_len > 0), so a
+        // crafted size < 8 can't spin the loop in place, and bounds every payload
+        // allocation to the real file length (no gigabyte over-allocation). Use
+        // checked_add so a 64-bit largesize near u64::MAX can't wrap past the guard.
+        if box_size < header_len || pos.checked_add(box_size).is_none_or(|end| end > file_end) {
+            return Err(crate::error::Error::Mp4Invalid.into());
+        }
         if &btype == b"moov" {
+            let payload_len = box_size - header_len;
+            // Absolute cap independent of the (sparse-file-inflatable) length.
+            if payload_len > MAX_ALLOC_BYTES {
+                return Err(crate::error::Error::Mp4Invalid.into());
+            }
             let mut buf = vec![0u8; payload_len as usize];
             file.read_exact(&mut buf)?;
             return Ok(buf);
         }
-        file.seek(SeekFrom::Current(payload_len as i64))?;
+        file.seek(SeekFrom::Start(pos + box_size))?;
     }
 }
 
@@ -310,7 +401,9 @@ fn mdhd_timescale(b: &[u8]) -> Option<u32> {
 /// mdhd language (5-bit packed ISO 639-2) → lowercase 3-letter code.
 fn mdhd_language(b: &[u8]) -> Option<String> {
     let version = b.first().copied()?;
-    let off = if version == 1 { 28 } else { 20 };
+    // v0: vflags(4)+creation(4)+modification(4)+timescale(4)+duration(4) = 20.
+    // v1: creation/modification/duration are 64-bit → vflags(4)+8+8+4+8 = 32.
+    let off = if version == 1 { 32 } else { 20 };
     if b.len() < off + 2 {
         return None;
     }
@@ -352,7 +445,9 @@ fn parse_stsd(b: &[u8]) -> Option<StsdInfo> {
     }
     let size = be32(entry, 0) as usize;
     let fourcc = [entry[4], entry[5], entry[6], entry[7]];
-    let body = &entry[8..size.min(entry.len())];
+    // `size` is untrusted: clamp to [8, entry.len()] so a declared size < 8 (or a
+    // truncated entry) yields an empty body instead of panicking on `entry[8..<8]`.
+    let body = &entry[8..size.clamp(8, entry.len())];
 
     let codec = match &fourcc {
         b"hvc1" | b"hev1" => Codec::Hevc,
@@ -384,28 +479,96 @@ fn parse_stsd(b: &[u8]) -> Option<StsdInfo> {
         })
     } else {
         // AudioSampleEntry: 6 reserved + 2 dri + 8 reserved + channelcount(2)
-        // samplesize(2) + 2 pre + 2 reserved + samplerate(4) = 28 bytes.
+        // samplesize(2) + 2 pre + 2 reserved + samplerate(4) = 28 bytes, then child
+        // boxes. AAC (mp4a) carries its AudioSpecificConfig in an `esds` box — the
+        // MKV CodecPrivate for A_AAC. AC-3/DTS are self-describing in-band (None).
         let channels = if body.len() >= 28 { be16(body, 16) } else { 2 };
+        let config = if matches!(codec, Codec::Aac) && body.len() >= 28 {
+            find_box(&body[28..], b"esds").and_then(parse_esds_asc)
+        } else {
+            None
+        };
         Some(StsdInfo {
             codec,
             height: 0,
-            config: None,
+            config,
             channels,
         })
     }
 }
 
+/// Read an MPEG-4 expandable descriptor length (ISO/IEC 14496-1), advancing `pos`.
+/// Each byte contributes 7 bits, continued while the high bit is set (max 4 bytes).
+fn read_descriptor_len(b: &[u8], pos: &mut usize) -> usize {
+    let mut len = 0usize;
+    for _ in 0..4 {
+        let Some(&byte) = b.get(*pos) else { break };
+        *pos += 1;
+        len = (len << 7) | (byte & 0x7F) as usize;
+        if byte & 0x80 == 0 {
+            break;
+        }
+    }
+    len
+}
+
+/// esds → AAC AudioSpecificConfig (the A_AAC CodecPrivate), or `None`. Walks
+/// ES_Descriptor(0x03) → DecoderConfigDescriptor(0x04) → DecoderSpecificInfo(0x05).
+/// Fully bounds-checked: a malformed/truncated esds returns None, never panics.
+fn parse_esds_asc(b: &[u8]) -> Option<Vec<u8>> {
+    // esds is a FullBox: version+flags(4), then the ES_Descriptor.
+    let mut pos = 4;
+    if *b.get(pos)? != 0x03 {
+        return None;
+    }
+    pos += 1;
+    read_descriptor_len(b, &mut pos); // ES_Descriptor length (unused)
+    pos += 2; // ES_ID
+    let flags = *b.get(pos)?;
+    pos += 1;
+    if flags & 0x80 != 0 {
+        pos += 2; // streamDependenceFlag → dependsOn_ES_ID
+    }
+    if flags & 0x40 != 0 {
+        // URL_flag → URLlength(1) + URLstring
+        pos += 1 + *b.get(pos)? as usize;
+    }
+    if flags & 0x20 != 0 {
+        pos += 2; // OCRstreamFlag → OCR_ES_Id
+    }
+    if *b.get(pos)? != 0x04 {
+        return None; // DecoderConfigDescriptor
+    }
+    pos += 1;
+    read_descriptor_len(b, &mut pos);
+    // objectTypeIndication(1) + streamType/bufferSizeDB(4) + maxBitrate(4) + avgBitrate(4)
+    pos += 13;
+    if *b.get(pos)? != 0x05 {
+        return None; // DecoderSpecificInfo
+    }
+    pos += 1;
+    let asc_len = read_descriptor_len(b, &mut pos);
+    let end = pos.checked_add(asc_len)?;
+    if asc_len == 0 || end > b.len() {
+        return None;
+    }
+    Some(b[pos..end].to_vec())
+}
+
 /// stsz → per-sample sizes.
-fn parse_stsz(b: &[u8]) -> Vec<u32> {
+fn parse_stsz(b: &[u8], max: usize) -> Vec<u32> {
     if b.len() < 12 {
         return Vec::new();
     }
     let sample_size = be32(b, 4);
-    let count = be32(b, 8) as usize;
+    // `count` is untrusted; clamp to the caller's remaining sample budget so neither
+    // a single 0xFFFFFFFF nor many crafted tracks can over-allocate (see from_reader).
+    let count = (be32(b, 8) as usize).min(max);
     if sample_size != 0 {
         return vec![sample_size; count];
     }
-    let mut out = Vec::with_capacity(count);
+    // Each entry is 4 bytes; `count` also can't exceed what the box actually holds.
+    let mut out = Vec::with_capacity(count.min((b.len() - 12) / 4));
     for i in 0..count {
         let o = 12 + i * 4;
         if o + 4 > b.len() {
@@ -422,8 +585,9 @@ fn parse_stco(b: &[u8], is64: bool) -> Vec<u64> {
         return Vec::new();
     }
     let count = be32(b, 4) as usize;
-    let mut out = Vec::with_capacity(count);
     let stride = if is64 { 8 } else { 4 };
+    // `count` entries of `stride` bytes can't exceed the box body.
+    let mut out = Vec::with_capacity(count.min((b.len() - 8) / stride));
     for i in 0..count {
         let o = 8 + i * stride;
         if o + stride > b.len() {
@@ -453,7 +617,8 @@ fn parse_stsc(b: &[u8]) -> Vec<(u32, u32)> {
         return Vec::new();
     }
     let count = be32(b, 4) as usize;
-    let mut out = Vec::with_capacity(count);
+    // Each entry is 12 bytes; `count` can't exceed what the box actually holds.
+    let mut out = Vec::with_capacity(count.min((b.len() - 8) / 12));
     for i in 0..count {
         let o = 8 + i * 12;
         if o + 12 > b.len() {
@@ -489,7 +654,9 @@ fn sample_offsets(sizes: &[u32], chunk_offsets: &[u64], stsc: &[(u32, u32)]) ->
                 break;
             }
             offsets.push(off);
-            off += sizes[sidx] as u64;
+            // `choff`/`sizes` are untrusted; saturate so a crafted co64 offset near
+            // u64::MAX can't overflow-panic (the read() EOF guard rejects it later).
+            off = off.saturating_add(sizes[sidx] as u64);
             sidx += 1;
         }
     }
@@ -500,13 +667,15 @@ fn sample_offsets(sizes: &[u32], chunk_offsets: &[u64], stsc: &[(u32, u32)]) ->
             .get(offsets.len().saturating_sub(1))
             .copied()
             .unwrap_or(0);
-        offsets.push(last + last_sz as u64);
+        offsets.push(last.saturating_add(last_sz as u64));
     }
     offsets
 }
 
-/// stts → per-sample decode durations (expanded from run-length entries).
-fn parse_stts(b: &[u8]) -> Vec<u32> {
+/// stts → per-sample decode durations (expanded from run-length entries). `max`
+/// caps the expansion — the caller passes the track's real sample count, past which
+/// entries are never read (and an untrusted run-length must not grow the Vec).
+fn parse_stts(b: &[u8], max: usize) -> Vec<u32> {
     if b.len() < 8 {
         return Vec::new();
     }
@@ -520,6 +689,9 @@ fn parse_stts(b: &[u8]) -> Vec<u32> {
         let n = be32(b, o);
         let delta = be32(b, o + 4);
         for _ in 0..n {
+            if out.len() >= max {
+                return out;
+            }
             out.push(delta);
         }
     }
@@ -527,7 +699,8 @@ fn parse_stts(b: &[u8]) -> Vec<u32> {
 }
 
 /// ctts → per-sample composition offsets (version 0 unsigned / version 1 signed).
-fn parse_ctts(b: &[u8]) -> Vec<i32> {
+/// `max` caps the expansion, as in [`parse_stts`].
+fn parse_ctts(b: &[u8], max: usize) -> Vec<i32> {
     if b.len() < 8 {
         return Vec::new();
     }
@@ -543,6 +716,9 @@ fn parse_ctts(b: &[u8]) -> Vec<i32> {
         let n = be32(b, o);
         let offset = be32(b, o + 4) as i32;
         for _ in 0..n {
+            if out.len() >= max {
+                return out;
+            }
             out.push(offset);
         }
     }
@@ -592,6 +768,72 @@ mod tests {
         assert_eq!(sample_offsets(&sizes, &chunks, &stsc), vec![500, 510, 900]);
     }
 
+    #[test]
+    fn sample_offsets_saturates_on_huge_chunk_offset() {
+        // A co64 chunk offset near u64::MAX plus a sample size must saturate, not
+        // overflow-panic (debug) / wrap (release) — the read() EOF guard rejects
+        // the resulting out-of-range offset later.
+        let sizes = vec![10u32, 20];
+        let chunks = vec![u64::MAX - 5];
+        let stsc = vec![(1u32, 2u32)]; // 2 samples in the single chunk
+        let offs = sample_offsets(&sizes, &chunks, &stsc);
+        assert_eq!(offs[0], u64::MAX - 5);
+        assert_eq!(offs[1], u64::MAX, "(MAX-5)+10 saturates to MAX");
+    }
+
+    #[test]
+    fn read_rejects_sample_offset_past_eof() {
+        use crate::disc::{
+            Codec, DiscTitle, FrameRate, HdrFormat, Resolution, Stream as DiscStreamE, VideoStream,
+        };
+        use crate::mux::mp4::Mp4Sink;
+        use crate::pes::{PesFrame, Stream as _};
+        use std::io::Cursor;
+
+        // The MP4 writer requires a primary video track, so build an HEVC one.
+        let mut t = DiscTitle::empty();
+        t.streams = vec![DiscStreamE::Video(VideoStream {
+            pid: 0x1011,
+            codec: Codec::Hevc,
+            resolution: Resolution::R1080p,
+            frame_rate: FrameRate::F23_976,
+            hdr: HdrFormat::Sdr,
+            color_space: crate::disc::ColorSpace::Unknown,
+            display_aspect: None,
+            secondary: false,
+            label: String::new(),
+            measured_cicp: None,
+        })];
+        t.codec_privates = vec![Some(vec![0xAA, 0xBB, 0xCC, 0xDD, 0xEE])];
+        let mut buf = Vec::new();
+        {
+            let mut sink = Mp4Sink::create(Cursor::new(&mut buf), &t).unwrap();
+            sink.write(&PesFrame {
+                track: 0,
+                pts: 0,
+                keyframe: true,
+                data: vec![0x11u8; 700],
+                duration_ns: None,
+                source: None,
+                coding: None,
+            })
+            .unwrap();
+            sink.finish().unwrap();
+        }
+        // Faststart writes `moov` near the front and `mdat` after a multi-MiB
+        // reserve, so a 64 KiB truncation keeps the parseable moov but drops mdat.
+        // from_reader still succeeds; read() must reject the now-out-of-range
+        // sample rather than allocate for it or read past EOF.
+        buf.truncate(64 * 1024);
+        let mut rd = Mp4Reader::from_reader(Cursor::new(buf), "trunc".into()).unwrap();
+        let err = rd.read().unwrap_err();
+        assert_eq!(
+            err.kind(),
+            std::io::ErrorKind::InvalidData,
+            "a sample offset past EOF must be rejected"
+        );
+    }
+
     #[test]
     fn write_then_read_round_trip() {
         // Mux a small A/V title to an in-memory MP4, then demux it back and
@@ -700,6 +942,161 @@ mod tests {
         stts.extend_from_slice(&1u32.to_be_bytes()); // entry_count
         stts.extend_from_slice(&3u32.to_be_bytes());
         stts.extend_from_slice(&1001u32.to_be_bytes());
-        assert_eq!(parse_stts(&stts), vec![1001, 1001, 1001]);
+        assert_eq!(parse_stts(&stts, MAX_SAMPLE_COUNT), vec![1001, 1001, 1001]);
+    }
+
+    // ── Untrusted-input hardening: a crafted MP4 must never panic or over-allocate.
+
+    #[test]
+    fn parse_stsz_fixed_size_caps_hostile_count() {
+        // sample_size != 0, count = u32::MAX: a 12-byte box must not allocate ~16 GiB.
+        let mut b = Vec::new();
+        b.extend_from_slice(&[0, 0, 0, 0]); // version+flags
+        b.extend_from_slice(&1u32.to_be_bytes()); // sample_size
+        b.extend_from_slice(&u32::MAX.to_be_bytes()); // count
+        let out = parse_stsz(&b, MAX_SAMPLE_COUNT);
+        assert_eq!(out.len(), MAX_SAMPLE_COUNT);
+        // And a smaller budget (the cumulative multi-track cap) bounds it tighter.
+        assert_eq!(parse_stsz(&b, 100).len(), 100);
+    }
+
+    #[test]
+    fn parse_stsz_table_count_bounded_by_box() {
+        // sample_size == 0, count huge, but only two real entries in the buffer.
+        let mut b = Vec::new();
+        b.extend_from_slice(&[0, 0, 0, 0]);
+        b.extend_from_slice(&0u32.to_be_bytes()); // sample_size == 0 → table
+        b.extend_from_slice(&u32::MAX.to_be_bytes()); // count (lie)
+        b.extend_from_slice(&10u32.to_be_bytes());
+        b.extend_from_slice(&20u32.to_be_bytes());
+        assert_eq!(parse_stsz(&b, MAX_SAMPLE_COUNT), vec![10, 20]);
+    }
+
+    #[test]
+    fn parse_stco_stsc_count_bounded_by_box() {
+        // stco: count lie, one real 32-bit offset.
+        let mut stco = Vec::new();
+        stco.extend_from_slice(&[0, 0, 0, 0]);
+        stco.extend_from_slice(&u32::MAX.to_be_bytes());
+        stco.extend_from_slice(&4096u32.to_be_bytes());
+        assert_eq!(parse_stco(&stco, false), vec![4096]);
+        // stsc: count lie, one real (first_chunk, per) tuple.
+        let mut stsc = Vec::new();
+        stsc.extend_from_slice(&[0, 0, 0, 0]);
+        stsc.extend_from_slice(&u32::MAX.to_be_bytes());
+        stsc.extend_from_slice(&1u32.to_be_bytes());
+        stsc.extend_from_slice(&7u32.to_be_bytes());
+        stsc.extend_from_slice(&0u32.to_be_bytes()); // sample_desc_idx (unused)
+        assert_eq!(parse_stsc(&stsc), vec![(1, 7)]);
+    }
+
+    #[test]
+    fn parse_stts_caps_hostile_runlength() {
+        // One entry with a u32::MAX run-length must cap, not push billions.
+        let mut stts = Vec::new();
+        stts.extend_from_slice(&[0, 0, 0, 0]);
+        stts.extend_from_slice(&1u32.to_be_bytes()); // entry_count
+        stts.extend_from_slice(&u32::MAX.to_be_bytes()); // n
+        stts.extend_from_slice(&33u32.to_be_bytes()); // delta
+        assert_eq!(parse_stts(&stts, MAX_SAMPLE_COUNT).len(), MAX_SAMPLE_COUNT);
+        // A tight per-track cap (the real sample count) bounds the run-length too.
+        assert_eq!(parse_stts(&stts, 5).len(), 5);
+    }
+
+    #[test]
+    fn parse_stsd_short_size_does_not_panic() {
+        // stsd sample entry declaring size = 0 must not panic on `entry[8..<8]`.
+        let mut b = Vec::new();
+        b.extend_from_slice(&[0, 0, 0, 0]); // version+flags
+        b.extend_from_slice(&1u32.to_be_bytes()); // entry_count
+        b.extend_from_slice(&0u32.to_be_bytes()); // sample entry size = 0
+        b.extend_from_slice(b"avc1"); // fourcc
+        // Recognised codec but empty body → None (no dimensions), no panic.
+        assert!(parse_stsd(&b).is_none());
+    }
+
+    #[test]
+    fn read_moov_oversize_is_rejected() {
+        use std::io::Cursor;
+        // A tiny file whose first box claims to be a `moov` far larger than the file.
+        let mut b = Vec::new();
+        b.extend_from_slice(&0xFFFF_FFF0u32.to_be_bytes()); // size32 (~4 GiB)
+        b.extend_from_slice(b"moov");
+        b.extend_from_slice(&[0u8; 16]); // a few real bytes, nowhere near the claim
+        assert!(read_moov(&mut Cursor::new(b)).is_err());
+    }
+
+    #[test]
+    fn parse_esds_extracts_aac_asc() {
+        // esds: version/flags + ES_Descriptor(0x03) + DecoderConfigDescriptor(0x04)
+        // + DecoderSpecificInfo(0x05) carrying a 2-byte AudioSpecificConfig.
+        let esds = vec![
+            0, 0, 0, 0, // version+flags
+            0x03, 0x19, 0x00, 0x00, 0x00, // ES_Descriptor: tag,len, ES_ID(2), flags(0)
+            0x04, 0x11, // DecoderConfigDescriptor: tag,len
+            0x40, // objectTypeIndication (AAC)
+            0x15, 0, 0, 0, // streamType/bufferSizeDB
+            0, 0, 0, 0, // maxBitrate
+            0, 0, 0, 0, // avgBitrate
+            0x05, 0x02, // DecoderSpecificInfo: tag,len
+            0x12, 0x10, // AudioSpecificConfig (AAC-LC 44.1k stereo)
+        ];
+        assert_eq!(parse_esds_asc(&esds), Some(vec![0x12, 0x10]));
+        // A truncated esds must return None, never panic.
+        assert_eq!(parse_esds_asc(&esds[..12]), None);
+    }
+
+    #[test]
+    fn read_moov_size_zero_spans_to_eof() {
+        use std::io::Cursor;
+        // size32 == 0 means "box extends to end of file"; the moov body is the rest.
+        let mut b = Vec::new();
+        b.extend_from_slice(&0u32.to_be_bytes()); // size = 0 → to EOF
+        b.extend_from_slice(b"moov");
+        b.extend_from_slice(&[0xAA, 0xBB, 0xCC]); // body
+        assert_eq!(
+            read_moov(&mut Cursor::new(b)).unwrap(),
+            vec![0xAA, 0xBB, 0xCC]
+        );
+    }
+
+    #[test]
+    fn read_moov_largesize_overflow_is_rejected() {
+        use std::io::Cursor;
+        // A 64-bit largesize near u64::MAX must not wrap the `pos + box_size` EOF
+        // guard (it would otherwise pass and drive an exabyte allocation).
+        let mut b = Vec::new();
+        b.extend_from_slice(&16u32.to_be_bytes()); // ftyp box, size 16
+        b.extend_from_slice(b"ftyp");
+        b.extend_from_slice(&[0u8; 8]);
+        b.extend_from_slice(&1u32.to_be_bytes()); // moov, size==1 → largesize
+        b.extend_from_slice(b"moov");
+        b.extend_from_slice(&0xFFFF_FFFF_FFFF_FFF8u64.to_be_bytes());
+        assert!(read_moov(&mut Cursor::new(b)).is_err());
+    }
+
+    #[test]
+    fn read_moov_undersized_box_does_not_hang() {
+        use std::io::Cursor;
+        // A box whose declared size is < 8 (here 3) must be rejected, not spin the
+        // loop in place forever (size.saturating_sub(8) == 0 → no forward progress).
+        let mut b = Vec::new();
+        b.extend_from_slice(&3u32.to_be_bytes());
+        b.extend_from_slice(b"free");
+        assert!(read_moov(&mut Cursor::new(b)).is_err());
+    }
+
+    #[test]
+    fn mdhd_language_offsets_per_version() {
+        // "eng" packed = 0x15C7. v0 carries it at byte 20, v1 (64-bit times) at 32.
+        let packed = [0x15u8, 0xC7];
+        let mut v0 = vec![0u8; 22];
+        v0[0] = 0; // version 0
+        v0[20..22].copy_from_slice(&packed);
+        assert_eq!(mdhd_language(&v0).as_deref(), Some("eng"));
+        let mut v1 = vec![0u8; 34];
+        v1[0] = 1; // version 1
+        v1[32..34].copy_from_slice(&packed);
+        assert_eq!(mdhd_language(&v1).as_deref(), Some("eng"));
     }
 }

src/mux/pipelined_stream.rs

@@ -659,8 +659,8 @@ mod tests {
 
     /// B1 end-to-end: after a TS discontinuity on a VIDEO track the consumer
     /// must DROP every inter-coded frame until the next keyframe, so no frame
-    /// with a dangling reference reaches the muxer (an ffmpeg deep-scan would
-    /// otherwise report a missing reference). The frame carrying the
+    /// with a dangling reference reaches the muxer (a strict decode-order
+    /// deep-scan would otherwise report a missing reference). The frame carrying the
     /// discontinuity and the inter frames behind it are dropped; the stream
     /// resumes cleanly at the next keyframe.
     #[test]

src/mux/resolve.rs

@@ -724,26 +724,6 @@ fn build_demux_state(title: &DiscTitle, format: ContentFormat) -> DemuxState {
     (parsers, pid_to_track, ts, ps)
 }
 
-/// Resolve the proactive [`AacsKeyMap`](crate::decrypt::AacsKeyMap) for a title
-/// before muxing. It decides which held unit key decrypts each of the title's
-/// LBA ranges and secures any key the pool is missing through the app's
-/// configured source (`fetch`) up front, never reactively per unit at mux time.
-///
-/// This is what ends the key-server storm. The old mux decrypted a unit, checked
-/// whether the plaintext looked like clean MPEG-TS, and — because authored-bad
-/// content never reaches that bar — re-asked the key service for a key it already
-/// held. There is no per-unit byte pattern that separates "correctly decrypted
-/// but authored-bad" from "still encrypted", so that check is unanswerable. Here
-/// we answer the answerable question instead: which CPS unit does each LBA range
-/// belong to, decided by the disc's key structure (validated once against real
-/// ciphertext samples, where the `is_clean` proof IS sound). The mux then just
-/// decrypts each unit with its mapped key and trusts it.
-///
-/// Single-CPS (the overwhelming majority, incl. every single-key UHD) is the
-/// trivial map: one key everywhere, no sampling. Multi-CPS assigns each extent to
-/// the key that opens a real sample from it; a bad-content extent no sample can
-/// classify inherits its predecessor's key (contiguity). FMTS segment mapping
-/// layers onto the same structure.
 /// FMTS (AACS 2.1) branch of [`resolve_mux_key_map`]. Returns `Some(map)` when the
 /// disc carries `IndividualSegment.tbl` AND a key source is configured; `None`
 /// otherwise (not FMTS, or no source — the caller's base-Unit-Key path then
@@ -932,6 +912,13 @@ fn resolve_fmts_key_map(
         Vec::with_capacity(segments.len());
     let mut unresolved = 0usize;
     for seg in &segments {
+        // SPNs are untrusted (from IndividualSegment.tbl); an inverted record
+        // (start_spn > end_spn) would underflow `end_byte - 1 - start_byte` below.
+        // (Mirrors the guard in `aacs::segment::fmts_key_ranges`.)
+        if seg.start_spn > seg.end_spn {
+            unresolved += 1;
+            continue;
+        }
         let Some(&slot) = tag_slot.get(&seg.index) else {
             unresolved += 1;
             continue;
@@ -969,6 +956,26 @@ fn resolve_fmts_key_map(
     )))
 }
 
+/// Resolve the proactive [`AacsKeyMap`](crate::decrypt::AacsKeyMap) for a title
+/// before muxing. It decides which held unit key decrypts each of the title's
+/// LBA ranges and secures any key the pool is missing through the app's
+/// configured source (`fetch`) up front, never reactively per unit at mux time.
+///
+/// This is what ends the key-server storm. The old mux decrypted a unit, checked
+/// whether the plaintext looked like clean MPEG-TS, and — because authored-bad
+/// content never reaches that bar — re-asked the key service for a key it already
+/// held. There is no per-unit byte pattern that separates "correctly decrypted
+/// but authored-bad" from "still encrypted", so that check is unanswerable. Here
+/// we answer the answerable question instead: which CPS unit does each LBA range
+/// belong to, decided by the disc's key structure (validated once against real
+/// ciphertext samples, where the `is_clean` proof IS sound). The mux then just
+/// decrypts each unit with its mapped key and trusts it.
+///
+/// Single-CPS (the overwhelming majority, incl. every single-key UHD) is the
+/// trivial map: one key everywhere, no sampling. Multi-CPS assigns each extent to
+/// the key that opens a real sample from it; a bad-content extent no sample can
+/// classify inherits its predecessor's key (contiguity). FMTS segment mapping
+/// layers onto the same structure.
 pub fn resolve_mux_key_map(
     reader: &mut dyn SectorSource,
     title: &DiscTitle,
@@ -980,42 +987,16 @@ pub fn resolve_mux_key_map(
         ALIGNED_UNIT_LEN, ALIGNED_UNIT_SECTORS, aacs_unit_encrypted, decrypt_unit, is_clean,
     };
 
+    // The base Unit Key pool is always resolved and banked by the caller before mux
+    // (autorip's pre-rip gate; the ISO path's `decrypt_keys()`), so an AACS title
+    // reaches here with a non-empty pool — an empty pool is reported as
+    // `DecryptKeys::None` and takes the CSS/clear arm above. `pool_len` is therefore
+    // always >= 1 for the AACS map paths below.
     let pool_len = match keys {
         crate::decrypt::DecryptKeys::Aacs { unit_keys, .. } => unit_keys.len(),
         // CSS / clear: no AACS map (the decorator's map path is AACS-only).
         _ => return Ok(crate::decrypt::AacsKeyMap::single(0)),
     };
-
-    // Secure the disc's key up front from the configured source when the pool is
-    // empty (a genuine "no key yet" — e.g. keydb miss, online-only disc).
-    if pool_len == 0 {
-        if let Some(f) = fetch {
-            let samples = crate::keysource::read_encrypted_units(reader, title, 8);
-            if !samples.is_empty() {
-                let fresh = f.unit_keys(&samples);
-                if let crate::decrypt::DecryptKeys::Aacs { unit_keys, .. } = keys {
-                    for k in fresh {
-                        if !unit_keys.iter().any(|(_, h)| *h == k) {
-                            let i = unit_keys.len() as u32;
-                            unit_keys.push((i, k));
-                        }
-                    }
-                }
-            }
-        }
-        // If the pool is STILL empty, this AACS-encrypted title needs a Unit Key we
-        // could not obtain from any source. That is the same situation as any known
-        // key we don't hold — fail loud at resolve time rather than deferring an
-        // opaque decrypt error (or, worse, emitting ciphertext) at mux time.
-        let empty = matches!(
-            keys,
-            crate::decrypt::DecryptKeys::Aacs { unit_keys, .. } if unit_keys.is_empty()
-        );
-        if empty {
-            return Err(crate::error::Error::DecryptFailed.into());
-        }
-        return Ok(crate::decrypt::AacsKeyMap::single(0));
-    }
     // FMTS (AACS 2.1): if the disc carries `IndividualSegment.tbl`, the forensic
     // segments need per-index keys the base Unit Key can't open. Resolve them up
     // front from the configured source and build a per-segment map. Returns `None`
@@ -1095,10 +1076,18 @@ pub fn resolve_mux_key_map(
                 }
             }
         }
-        // A bad-content extent no sample can classify inherits its predecessor's
-        // key (CPS boundaries are contiguous, so the neighbour is almost always
-        // right); this never storms and never mis-fails a decryptable disc.
-        let idx = idx.unwrap_or(last_idx);
+        // `sample_units` draws REAL content (not authored-bad units), so a sample
+        // no held or fetched key decrypts to clean means this extent's CPS-unit key
+        // is genuinely absent. Building a map that silently assigns a WRONG key
+        // (the neighbour's) would corrupt the whole extent with lost_bytes==0 — so
+        // fail loud instead: the keymap is built ONLY when every extent with
+        // encrypted content is classified. An extent with no sampleable encrypted
+        // units (nothing to mis-decrypt) carries the previous index harmlessly.
+        let idx = match idx {
+            Some(i) => i,
+            None if samples.is_empty() => last_idx,
+            None => return Err(crate::error::Error::DecryptFailed.into()),
+        };
         last_idx = idx;
         ranges.push((
             ext.start_lba,

src/mux/resync.rs

@@ -5,9 +5,9 @@
 //! When packets are lost, the affected access unit is already dropped at the TS
 //! layer (the assembler drops the partial PES on the continuity gap). But for
 //! INTER-CODED video the frames that follow reference the lost frame (and each
-//! other) until the next IRAP/IDR keyframe — emitting them yields an ffmpeg
-//! "missing reference / non-existing PPS" deep-scan error and visibly broken
-//! decode. So after a gap on a video track we DROP FORWARD to the next keyframe
+//! other) until the next IRAP/IDR keyframe — emitting them makes any decoder
+//! fault on the "missing reference / non-existing PPS" condition and visibly
+//! break decode. So after a gap on a video track we DROP FORWARD to the keyframe
 //! and resume cleanly there. The gap rounds up to (at most) one GOP — the price
 //! of never emitting a dangling reference; it is logged.
 //!

src/mux/timeline.rs

@@ -23,7 +23,8 @@ pub(crate) const DISCONTINUITY_GAP_NS: i64 = 1_000_000;
 /// one concatenated sector stream (clip boundaries / mpls connection_condition
 /// are not plumbed to the mux), so at a non-seamless boundary the source PES
 /// PTS jumps backward. Left uncorrected, that produces a sustained band of
-/// non-monotonic block timestamps (ffmpeg then derives non-monotonic DTS).
+/// non-monotonic block timestamps (a downstream muxer then derives
+/// non-monotonic DTS from them).
 ///
 /// A single running `offset_ns` is applied to EVERY track, so the concatenated
 /// clips form one monotonic timeline AND A/V sync is preserved (all tracks at a

src/scsi/linux.rs

@@ -8,8 +8,9 @@
 //! when `hdr.timeout` expires, and by the time the ioctl returns the
 //! kernel has already done what it can.
 //!
-//! This matches what every reference project does: MakeMKV (8 s sync
-//! ioctl), sg_dd (60 s sync ioctl), the kernel default for SCSI block
+//! This matches established practice for optical/SCSI I/O: a single
+//! synchronous ioctl with a bounded per-command timeout (commonly in the
+//! 8–60 s range), consistent with the Linux kernel default for SCSI block
 //! devices (30 s `/sys/.../timeout`).
 //!
 //! Pre-0.13.20 we ran an async `write() + poll(1.5s) + close-on-timeout +

src/sector/decrypting.rs

@@ -19,6 +19,11 @@ use std::sync::Arc;
 
 use super::SectorSource;
 
+/// A closure resolving keys from encrypted-content samples — the shape of both
+/// [`KeyFetch`] operations. Named so the two constructors (and the struct fields)
+/// read clearly.
+pub type KeyFetchFn = std::sync::Arc<dyn Fn(&[Vec<u8>]) -> Vec<[u8; 16]> + Send + Sync>;
+
 /// Application-supplied "fetch a fresh key for THIS data" callback.
 ///
 /// Invoked by [`DecryptingSectorSource`] when a read contains scrambled AACS
@@ -49,11 +54,6 @@ use super::SectorSource;
 /// mutable state (its call-count cap and spent flag), so one `KeyFetch` is built
 /// once and cloned cheaply (two `Arc` bumps) into every read path. `Send + Sync`
 /// so it can ride the mux highway's producer thread.
-/// A closure resolving keys from encrypted-content samples — the shape of both
-/// [`KeyFetch`] operations. Named so the two constructors (and the struct fields)
-/// read clearly.
-pub type KeyFetchFn = std::sync::Arc<dyn Fn(&[Vec<u8>]) -> Vec<[u8; 16]> + Send + Sync>;
-
 #[derive(Clone)]
 pub struct KeyFetch {
     unit: KeyFetchFn,
@@ -187,7 +187,7 @@ impl<S: SectorSource> DecryptingSectorSource<S> {
     /// (sorted/merged `(start_lba, sector_count)` — see
     /// [`Disc::encrypted_content_ranges`](crate::Disc::encrypted_content_ranges)).
     /// Units outside content (UDF filesystem / BDMV nav) pass through untouched,
-    /// so [`ts_sync_destroyed`](crate::aacs::content::ts_sync_destroyed) is never consulted
+    /// so the TS-sync content check is never consulted
     /// about non-content bytes. Whole-disc readers (sweep / patch) set this; the
     /// mux leaves it unset because it only ever reads title extents.
     pub fn with_content_ranges(mut self, ranges: Arc<[(u32, u32)]>) -> Self {
@@ -338,11 +338,11 @@ impl<S: SectorSource> SectorSource for DecryptingSectorSource<S> {
         // FRESH-KEY-ON-FAILURE: hand a unit no held key opened (as its on-disc
         // ciphertext) to the application's key source; any returned key is added to
         // the pool and the read is re-decrypted, caching the key for later units.
-        // The pass-through result is the consumer's concern — the decorator never
-        // counts a decrypt-quality miss as loss. Genuine missing data is the
-        // zero-filled sectors the physical read layer records, not a TS-structure
-        // miss; a real can't-decrypt (empty pool / misalignment) already surfaced
-        // as `Err` from `decrypt_buf`.
+        // If the source is asked for this exact ciphertext and STILL cannot supply a
+        // key (the recovery's residual `dropped > 0`), the unit is genuinely
+        // unresolvable — this decrypting sweep/patch path FAILS LOUD rather than
+        // write the still-encrypted bytes into the output as if they were clear
+        // content (the mux path fails loud the same way via `decrypt_sectors_mapped`).
         if dropped > 0 && self.recovery.is_some() {
             // Rare miss only: the in-place decrypt overwrote `buf`, so RE-READ the
             // on-disc ciphertext for the key-fetch retry. This keeps the happy path
@@ -368,7 +368,10 @@ impl<S: SectorSource> SectorSource for DecryptingSectorSource<S> {
                 .as_mut()
                 .expect("recovery.is_some() checked above");
             let cipher = &self.cipher_scratch[..n];
-            let _ = r(&mut buf[..n], cipher, &mut self.keys, &rctx);
+            let outcome = r(&mut buf[..n], cipher, &mut self.keys, &rctx);
+            if outcome.dropped > 0 {
+                return Err(crate::error::Error::DecryptFailed);
+            }
         }
         Ok(n)
     }
@@ -701,8 +704,8 @@ mod tests {
 
     /// A source that yields exactly one CLEAR AACS aligned unit (6144
     /// bytes = 3 sectors) with MPEG-TS sync bytes (0x47) at the BD-TS
-    /// stride (offset 4, then every 192 bytes). `ts_sync_destroyed`
-    /// reports such a unit as NOT scrambled, so the AACS decrypt path
+    /// stride (offset 4, then every 192 bytes). `is_clean`
+    /// reports such a unit as clear (not scrambled), so the AACS decrypt path
     /// reaches the per-unit closure and leaves it untouched — letting
     /// us prove the unit-key LOOKUP (not the cipher) is what fails for
     /// an out-of-range index.

src/sector/mod.rs

@@ -261,9 +261,10 @@ mod tests {
         }
     }
 
-    /// Call `set_unit_base` through a generic `S: SectorSource` bound — this is
-    /// the path that actually exercises the `Box<dyn>` / `&mut dyn` FORWARDING
-    /// impls (a direct call on a `dyn` value dispatches via the vtable instead).
+    /// Call `set_unit_base` through a generic `S: SectorSource` bound so the
+    /// `Box<dyn SectorSource>` / `&mut dyn SectorSource` FORWARDING impls are the
+    /// ones invoked (the generic monomorphizes to each forwarding body — the same
+    /// body a direct call on those receiver types also resolves to).
     fn set_unit_base_generic<S: SectorSource>(mut s: S, base: u32) {
         s.set_unit_base(base);
     }