A damaged audio access unit is now dropped rather than muxed as a
decoder-choking glitch. Sync is preserved — a drop becomes a silence
gap, never a shift — and every drop is logged. Detection is per-codec,
each mirroring the format's authoritative integrity check:
DTS core-header validity gates
AC-3/E-AC-3 native frame CRC-16 + bitstream-id range
FLAC whole-frame CRC-16 residue
MP2/MP3 header sanity + free-format reject
AAC-ADTS header sanity (raw AAC passes through untouched)
TrueHD/MLP major-sync CRC-16 + AU parity; corrupt AUs drop forward
to the next major sync, since decode state carries
across access units
LPCM and video are excluded by design (no in-frame integrity data;
inter-frame prediction). A shared DropTally handles counting, logging,
and a whole-track fallback for a mostly-undecodable track.
Two defensive hardenings from the post-fix audit (vs FFmpeg/GStreamer):
1. Move the `pes.discontinuity` partial-drop ABOVE the empty-data guard in
all three audio parsers (ac3/dts/truehd), so a discontinuity signal can
never be stranded by an empty post-gap PES. The demuxer only emits
non-empty PES today; this is defense-in-depth for any future caller.
2. A PES with no PTS must not reset the timeline to 0. ac3 now carries
`flush_pts_ns`, dts continues from the most recent known base; truehd
already kept its running cadence on a None PTS. Matches OSS behavior
(PTS rebases off the next PES that actually carries a PTS).
Adds an ac3 regression test (empty-payload discontinuity PES still drops
the stranded partial). Loss accounting was reviewed: TS-demux CC-gaps are
NOT counted toward lost_video_secs / abort (that is sector-based via
DiscStream::errors / mapfile bytes_unreadable), so a source splice never
inflates loss — no gating needed there.
The AC-3, DTS and TrueHD parsers buffer access units across PES
boundaries. At a concealed-loss gap the buffered unit is truncated:
splicing post-gap bytes onto it manufactures a corrupt frame on top of
the real loss (FFmpeg "Failed to decode block code(s)" / "Invalid data
found" at the gap) and, for TrueHD, strands the PTS cadence into the
non-monotonic audio-DTS band seen on multi-clip titles.
The video parsers already handle this via the ResyncGate, but the
discontinuity signal was only wired into video — audio parsers ignored
pes.discontinuity and spliced across the gap.
Now, when pes.discontinuity is set, each audio parser drops the partial
(clears buf, and for DTS its PTS marks / pending base) so the post-gap
PES re-bases a fresh unit. A lost gap degrades to a clean single-frame
drop instead of a corrupt spliced frame. No effect on perfect rips: the
branch only runs when concealment inserted a discontinuity marker.
Adds a per-parser test feeding a partial frame then a discontinuity PES,
asserting the truncated partial is dropped (not spliced) and the post-gap
PTS is adopted.
Closes the three residual holes where a concealed/lost gap could still let
a dangling-reference frame reach the muxer (degraded/undecryptable-disc
path only; clean rips are byte-identical and untouched). Root cause: the
discontinuity signal was reconstructed from the 4-bit continuity counter
and applied per-PES, both of which are lossy.
Three coordinated changes:
1. CC-INDEPENDENT marker. fill_null_ts_unit now tags its NULL packets with
an adaptation-field discontinuity_indicator; the demuxer recognises a
0x1FFF packet carrying it as a concealed gap and forces a discontinuity
on every tracked PID (the lost unit's PID is unknowable). This survives
a loss that is an exact multiple of 16 packets (CC aliases to in-sequence
— hole 3) and a loss at a PID's very start (no prior CC — hole 4); it
also drops any open, potentially-truncated partial PES.
2. PUSI ATTRIBUTION. A gap landing on a PES boundary now flags the PES
STARTING after it, not the one flushed at the boundary (hole 1) —
stamping the pre-gap frame could arm-then-disarm the gate on a keyframe
and admit the real post-gap inter frame.
3. PER-FRAME signal. codec::Frame gains `discontinuity`; each parser
propagates it onto the first post-gap frame. MPEG-2 buffers whole GOPs
asynchronously, so it associates the gap by ES OFFSET (like PTS/source),
landing it on the exact post-gap picture mid-GOP (hole 2) — a per-PES
flag stamped the previous picture. consume_ts (and the EOF flush drain)
gate on frame.discontinuity.
Tests: CC-independent marker with in-sequence CC + leading-loss; PUSI
attribution flags the post-gap PES; MPEG-2 offset-mark stamps the post-gap
picture through GOP reorder, not the previous one. Existing B1 gate + EOF
tests still green (2270 lib tests).
Pairs with A2 (read-path NULL-TS concealment). When the demux assembler
sees a TS continuity gap it now stamps `discontinuity` on the next
completed PES; the codec-parse stage carries that onto a per-track
ResyncGate. After a gap on an inter-coded video track the gate drops
forward to the next IRAP/IDR keyframe so no frame with a dangling
reference reaches the muxer (an ffmpeg deep scan would otherwise report
a missing-reference / non-existing-PPS error). Audio and subtitle tracks
have no cross-frame references, so the gate is a no-op there.
- ts.rs: PesPacket gains `discontinuity`; PesAssembler tracks a sticky
pending_discontinuity flag set on CC gap / discontinuity_indicator and
carried to the next completed/flushed PES.
- resync.rs (new): ResyncGate — per-track arm-on-gap, drop non-keyframes
until the next keyframe disarms and resumes. Logs the resync + drop
count once at the keyframe.
- pipelined_stream.rs: precompute per-track is_video, apply the gate in
consume_ts. Out-of-range track index emits as-is (defensive).
Tests: ResyncGate unit tests; ts.rs gap-stamps-discontinuity; end-to-end
B1 video-drops-to-keyframe and audio-never-drops through PipelinedPesStream.
Surgical fixes (each with a regression test that fails without the change):
mux/mkv.rs, mux/demux_sink.rs: drive the clip-boundary timeline epoch
off the resolved PRIMARY VIDEO track, not the literal stream index 0.
An M2TS/PMT title can list an audio ES before video, so streams[0] may
be audio; a non-video epoch driver ratchets the frontier and inflates
the timeline. mkv cluster-opening falls back to track 0 for audio-only
titles so they still open clusters.
mux/codec/ac3.rs: correct ACMOD_CHANNELS — acmod=5 (3/1) is 4 channels,
not 3 (was undercounting a 3/1 stream); fix the A/52 Table 5.8 doc.
disc/mod.rs: HDMV coding_type 0x91 (Interactive Graphics / menus) no
longer maps to PGS subtitle — it falls through to Unknown so the PMT/STN
walker drops it instead of surfacing a bogus subtitle track.
mux/videomap.rs + mux/mkv.rs: FVI colour now mirrors the MKV muxer's CICP
precedence (measured CICP authoritative; HDR-driven PQ/HLG transfer
override) via a shared cicp_for_video helper, so the two sinks can't
disagree (HDR10 BT.2020 no longer emits SDR transfer 14).
mux/mkvstream.rs: saturating_add on cluster_ts + rel_ts so an adversarial
CLUSTER_TIMESTAMP near i64::MAX can't overflow/panic before the existing
saturating_mul.
mux/timeline.rs: tighten the tail-straggler clamp so a normal new-epoch
non-video frame leading the sparse video frontier by >3s is not demoted
into the previous clip's epoch.
mux/m2ts_mux/mod.rs: re-stamp PCR per video TS packet (mid-PES), not only
at PES boundaries, so a large UHD I-frame can't open a multi-second PCR
gap; modular 33-bit PTS rebasing so a real 90 kHz clock wrap is not
collapsed to PTS 0 (pre-base frames still floor to 0).
io/byte_prefetcher.rs, sector/prefetched.rs: wrap the producer feed loop
in catch_unwind and emit a typed error sentinel on panic, so a mid-stream
producer panic is not read as a clean EOF at the demux boundary (which
would silently truncate the mux).
mux/codec/h264.rs: extend HIGH_PROFILES to the full ISO/IEC 14496-15 set
that mandates the avcC chroma/bit-depth extension (adds 244 et al.).
Doc/comment accuracy: css/mod.rs (50000 sectors, not scrambled-sectors),
aacs/decrypt.rs (decrypt_unit already-clear path), ifo.rs (TT_SRPT at
0xC4), css/lfsr.rs (LFSR0 24-bit; TAB1-then-XOR cipher; real scramble-flag
predicate), disc/read_error.rs (for_sweep does bounded transient retries).
Skipped: keydb.rs SSRF guard (low/latent, no live caller) — a hard
loopback block breaks an existing behavioral test that exercises the
header-EOF path over a loopback server; a clean fix needs a resolver test
seam beyond this surgical pass. The sibling keydb_fetch.rs comment fix is
out of scope (freemkv crate).
Carry per-picture truth and byte-exact source provenance THROUGH the stream so
the muxer (and the upcoming video index) read MEASURED facts instead of
assuming them. Honest data in, honest data out.
- codec/coding.rs: codec-agnostic PictureInfo (CodingType / FieldOrder + the
accessors field_order/coding_type/nb_fields/progressive/keyframe). Each codec
folds its raw signals in; consumers use only accessors, never branch on codec.
- mpeg2: builds PictureInfo from the picture coding extension and carries it +
SourcePos (source_marks, parallel to pts_marks) on every emitted frame.
- pes / codec::Frame: additive `coding` + `source`, forwarded through the
highway; None for audio/subtitle and the network/stdio deserialize hop.
- mkvstream: DEFER muxer construction until the first coded picture, set the
video track's FieldOrder from the MEASURED value, THEN write the header —
right the first time, no guess, no seek-back. An interlaced track that arrives
with no measured order is LOGGED loudly and left UNDETERMINED, never faked.
- mkv: MkvTrack::video no longer guesses TFF (a bitstream property the scan
cannot know is UNDETERMINED at build). Removed VideoStream::top_field_first
(the dead scan-time guess) crate-wide.
- Tests: parser population (every PictureInfo facet + per-PES source carry) and
mux-stream consumption (measured -> correct; missing -> UNDETERMINED, not
faked). Two obsolete tests updated only after confirming (their own comments)
they existed to enforce the deleted hardcoded-TFF.
Fixes the "Silence of the Lambs" R2 PAL wrong-substream rip: the feature's
IFO declares one 5.1 AC-3 stream, but the scan assigned it the on-wire
sub-stream id 0x80 purely by per-codec ordinal (ifo::assign_audio_sub_stream_ids).
On this disc the physical 0x80 carries the 2.0 down-mix and the 5.1 main mix
lives at a different 0x8x sub-stream, so the rip muxed 2.0 while labelling it
"Dolby Digital 5.1" (the acmod fixup in mkv.rs then corrected only the Channels
element, surfacing the mismatch as the "IFO claimed 6 but acmod says 2" warning
— too late to re-route).
New src/disc/dvd_audio_probe.rs probes each physical AC-3 sub-stream's real
channel count from the head of the feature (the acmod/lfeon of its first frame
after the 0x0B77 sync) and re-routes each IFO-declared AC-3 stream onto the
physical sub-stream whose actual channel count matches the declared count,
instead of trusting the ordinal. Wired into both mux demux paths
(DiscStream::new and resolve::build_iso_pipeline) over the decrypting reader,
so it works on CSS discs and the autorip ISO-remux path alike. Bounded
512-sector best-effort read; an empty/unreadable probe degrades to the original
ordinal mapping (no regression on normal discs).
The cell selection is left unchanged: the feature's cell 0 (cat=0x02, 302.4s)
is chapter 1 of the movie (matches MakeMKV's chapter map and 1h53 duration
exactly), so it must NOT be dropped — the perceived "wrong video at the start"
was the wrong 2.0 audio over the opening, the same root cause.
Diagnostics (--log-level 3): new tag=dvd.substream rows dump the ACTUAL acmod
channel count of each physical 0x8x sub-stream read from the VOB, and the
per-cell tag=dvd.cell verdict now spells out the keep/skip reason. With the
existing tag=dvd.aattr (IFO declared sub_id + channels) a bug log alone now
shows whether the ordinal 0x80 really carries the declared layout — no disc
needed to diagnose this class.
expose ac3::find_ac3_sync as pub(crate) for the probe.
- CSS: unlock scrambled-sector reads on enforcing drives via bus-auth
only; classify sense 6F/03 as CSS-locked; early-bail on a fully locked
scan; gate the AACS handshake off DVD discs.
- DVD first-play menu no longer prepended to the feature: read the title
VOBS base from vtstt_vobs (0xC4), not the menu VOBS vtsm_vobs (0xC0).
- Interlaced field-duration (DefaultDecodedFieldDuration) written as a
direct TrackEntry child rather than inside Video, so Windows reports
the correct frame rate.
- Audio channel count read from the AC-3 bitstream; FieldOrder set to
TFF; per-track BPS tags.
- Structured disc diagnostics at --log-level 3; reduced per-operation
log spam.
Test-hardening release, no runtime changes. Adds spec-grounded unit tests
across the silent-corruption surfaces — UDF/MPLS/CLPI/IFO parsing, BD/DVD
title + extent assembly, AACS/CSS key handling, TS/PS demux + codec parsers,
MKV/EBML container output, the mux pipeline, sector prefetch + decrypt
decorator, drive/SCSI sense decoding, label extraction, and core I/O. Each
test is grounded in the format spec or real on-disc behavior and verified to
fail under a targeted source mutation. No behavior changed.
Library-wide review-and-fix pass: tightened AACS keydb/handshake/variant
handling and trailing-partial-unit policy, corrected MPLS mark offset and
added UDF allocation bounds, hardened the mux/codec framing and M2TS paths,
guarded SCSI READ CAPACITY short transfers and unified error mapping, added
overflow guards on untrusted disc input, and made prefetch shutdown
deterministic. Release profile now builds with thin LTO + single codegen unit.
Two defects:
- Ac3Parser inherited the no-op default flush(), so a complete final
frame still buffered at end-of-stream was dropped (~32 ms of audio
lost). Add a flush() that drains a complete buffered frame, mirroring
dts.rs.
- Every frame in one parse() call was stamped with the single PES PTS,
collapsing their timecodes and drifting A/V. Compute a base PTS once
per call, then advance per frame by the frame's own duration (AC-3 =
1536 samples; E-AC-3 from numblkscod), converting samples->ns at the
stream sample rate (fscod). Each Frame now carries duration_ns.
Audit-driven fixes (rounds 1–3):
- hevc: correct hvcC profile/level SPS offsets (HEVC has a 2-byte NAL header)
- mkv: map all DTS variants to the registered A_DTS codec id; force a new
cluster before the i16 cluster-relative timestamp can overflow
- ebml/mkvstream: bound untrusted EBML sizes (no multi-GB allocs); reject
uint>8 (was an OOB panic) and non-{0,4,8} float widths (were a desync)
- ts: skip PES-header bytes that span a TS packet boundary; add the PMT
section_len/prog_info_len bounds the PAT parser already had
- ac3: preserve a 0x0B77 syncword split across a PES boundary; cap buffer
- dts: validate each next-core boundary by decoded core size (a 0x7FFE8001
pattern inside XLL payload no longer false-splits/drops the lossless
extension); reject sub-minimum core frames; fix forced-emit PTS base
- lpcm: DVD program-stream PCM no longer double-strips the BD LPCM header
- vc1/mpeg2: do not emit a parameter-set-only PES as a standalone frame
- pgs/truehd: cap the pending reassembly buffer (parity with ac3/dts)
- aacs: ts_syncs_intact uses the exact packet count
- prefetched: capacity-guard the recycled-buffer set_len
- Cargo.toml: exclude project docs from the published crate
Convergence: a third independent audit pass found no remaining material
(CRITICAL/HIGH/MEDIUM) issues. Full precommit (fmt + clippy -D + tests,
Rust 1.86) green.
- MkvTrack::audio emits A_DTS/MA, A_DTS/HR, A_DTS per the DTS family
instead of mislabelling everything as A_DTS. Plex transcoder and
strict hardware decoders reject DTS-HD MA payload under a plain
A_DTS track.
- PgsParser is now stateful: pairs display PCS with the following
empty PCS to compute a duration. Frame::duration_ns + PesFrame::duration_ns
carry it through; MkvMuxer::write_frame gains a final Option<u64>
parameter that emits BlockGroup + BlockDuration when set. Fixes
subtitle bitmaps lingering past their intended end-time.
- Add state to Ac3Parser (was stateless, split frames at PES boundaries)
- Buffer leftover bytes from incomplete frames for next PES packet
- Calculate exact AC3 frame size from fscod/frmsizecod table
- Calculate EAC3 frame size from frmsiz field
- Skip invalid frame sizes (0 or >8192)
- Eliminates all AC3 decode errors on BD and UHD output
Matthew Jackson