Three TrueHD state-machine fixes from an adversarial audit:
- A corrupt access unit drops forward to the next major sync, but only
the individually-verified corruption now feeds the whole-track poison
verdict; the resync run is collateral. A couple of transient errors can
no longer poison and discard an otherwise-good multi-hour track. The
shared drop tally gains a verified/collateral split for this.
- The per-AU PTS rate is refined only from a CRC-validated major sync, so
a corrupt major sync whose rate nibble decodes to another rate family
can no longer shift the resumed audio — a drop stays a silence gap.
- The resync clears only on a CRC-validated major sync, never on a runt
too short to hold and validate its header.
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.
Post-read verify gate (new src/disc/verify.rs): UnitVerifier buffers/aligns the disc-absolute read stream into clip-file 6144-byte units, then makes one decryptability() decision per unit (CPI gate -> held keys -> key_fetch -> strict TS). POST_READ_VERIFY const kill-switch; fail-safe contract (only ever downgrades units it is confident are undecryptable; every doubt skips). Hooked into Disc::sweep (producer observes ciphertext -> WorkItem::MarkBad after the Good, FIFO-ordered) and Disc::patch (post-loop reverify_iso reads recovered units whole from the patched ISO). extract::clip_layouts enumerates AACS clips for the gate.
Standards-correct AACS verify: aacs::unit_is_clean_ts is a strict port of libaacs _verify_ts (all 32 TS syncs, not a majority vote); decrypt_unit accepts a key only on it; the majority verify_ts is removed. Deleted the Disc::verify_clips post-pass bolt-on (its primitive is absorbed by the read-path gate).
libaacs/DVD audit fixes: content-cert bus_encryption flag now read from bit 7 (was bit 0 - defeated the bus-key fail-loud gate); cc_id read from offset 14; title_cps_unit range-validated + 1->0 index-converted per libaacs. Corrected attack_crib ("functionally-equivalent" not "exact" port) and read_disc_key (READ DVD STRUCTURE 0xAD, not REPORT KEY) doc comments.
Also includes accumulated uncommitted work: key-fetch seam and TrueHD/DTS audio fix.
TrueHD: when the PES PTS lags the access-unit cadence, resync to the PTS
but never snap the running timestamp backward, so the emitted DTS stays
monotonic across the resync (next_pts_ns = max(next_pts_ns, pts)).
DTS-HD MA: size each EXSS extension substream exactly from its header
(exss_frame_size) and skip it as a unit, so a false 0x7FFE8001 core sync
inside the lossless extension payload can no longer split the access unit
and truncate the extension. Falls back to a bounded scan when the header
is unparseable.
Provenance: build.rs bakes the git short hash into GIT_SUFFIX; the muxing/
writing-application field and the FVI generator tag now record the exact
build (e.g. "freemkv 1.1.0-beta.1 (g835cc99)"), so any output file is
traceable to the revision that produced it.
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.
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.
A continuation PES (one that merely extends a TrueHD AU spanning PES
packets) carries its own later PTS, which the parser was adopting
mid-assembly, snapping the AU's timestamp and breaking the monotonic
per-AU cadence (A/V drift). Capture the PTS base only when the
reassembly buffer is empty, i.e. when a PES actually begins a new AU.
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.
Adds truehd_channels(format_info) + truehd_channels_from_stream(): the
real presentation channel count (8ch/7.1 when present, else 6ch/5.1)
from the TrueHD major sync, which the MPLS audio_format base field
understates (declares 5.1 even on a 7.1/Atmos track — the Dune case).
Per the MLP spec presentation channel-assignment masks. 3 unit tests.
This is the decoder; wiring it to correct AudioStream.channels requires
a mux-time probe of the DECRYPTED audio payload (the channel truth isn't
readable at scan — the m2ts is AACS-encrypted until the key is applied
at mux), to be added + validated on a real rip.
- 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.
- DTS: buffer with core sync detection + frame size from header
- TrueHD: buffer with unit length field parsing
- Same pattern as AC3 fix: incomplete frames held for next PES
- When PES boundaries align (normal case), buffering is a no-op
Matthew Jackson