PROVENANCE deviations #6 and #7 carried 'report upstream' — done:
- chromeos/cros-codecs#99: h264 PictureData display_resolution
double-counts the left/top crop and underflow-panics on
parser-valid crop offsets (answers their open #81).
- chromeos/cros-codecs#100: h265 parse_slice_header index-OOB panic
when num_long_term_sps + num_long_term_pics > 16 — a hostile-input
panic on the LTR path (an instance of their #78).
Both reports offer the downstream patch for the AOSP tree.
H265Planner mirrors the H.264 layer's contract exactly: plan_au -> AuPlan
{ picture, slices with ref lists by stable PicId, DpbUpdate, warnings },
same concealment posture (warnings never abort, in-place reference
substitution preserving ref_idx positions, outputs survive failed AUs,
flush gates on AwaitingIdr, any IRAP resumes). Ported logic: RPS 8.3.2
(short-term AND long-term incl. PocLsbLt/MSB-cycle - the hosts' RFI
recovery rides long-term refs), ref lists 8.3.3/8.3.4, DPB C.5.2.2/C.5.2.3
via the vendored dpb; POC 8.3.1 from the vendored PictureData. Written
fresh: the plan surface, AU walk, envelope gates (multilayer, interlaced,
SCC self-reference, DPB>16, conf-window overflow - checked at EVERY
activation, not just parse), HEVC recovery-point SEI (prefix NALU 39,
se(v) recovery_poc_cnt), VUI colour with E.3.1 inference, and a test-only
HEVC bitstream synthesizer (upstream has none).
Upstream deviations worth naming (all in-code with spec anchors): the
empty-RPS inter slice cannot infinite-loop (upstream bug); RASL behind a
joined CRA refuses BEFORE any state change (PlanError::RaslSkipped - the
WP-2 wiring must map it to skip, not reanchor; module docs carry the
contract note); MaxPicOrderCntLsb reads from the ACTIVATING SPS (upstream
latches at parse - a latent multi-SPS bug); C.5.2.2's exemption is
picture 0 of the BITSTREAM (EobNut), never first-after-EOS.
Vendored parser gained PROVENANCE deviation 7 (report upstream): hostile
slice headers with num_long_term_sps+num_long_term_pics > 16 indexed out
of bounds of SliceHeader's [_;16] arrays - a production panic on exactly
the long-term-reference path, now a parse error.
Port review round 7: 10 findings (3 blocking: the vendor panic, an
EOS-boundary output interleave, an envelope bypass through PPS-only SPS
rebind reaching wrapping crop arithmetic) - 9 fixed with a regression
test each, 1 documented as the WP-2 contract note. Known follow-up: the
h264 AU-tail truncation detector shares h265's dead-arm shape (its arm
also cuts reserved NALU types, so the fix is not identical - deferred).
Tests: 29 h265 planner + 2 HEVC SEI + full test-25fps.h265/bear/bbb clip
walks with real invariants (every stored id output exactly once,
ascending POC per IRAP period). Gates: fmt clean; clippy -D warnings zero
(mac + pf-lxcheck2 incl. pf-client-core/pf-presenter); tests 45+69 mac,
69+121+53 container.
Adapted from cros-codecs decoder/stateless/h264.rs (POC 8.2.1, ref lists
8.2.4 incl. modification, sliding-window + MMCO/LTR marking 8.2.5,
frame_num-gap handling 8.2.5.2), minus the fd-coupled backend trait.
H264Planner::plan_au maps one wire AU to picture params, per-slice byte
ranges + ref lists keyed by stable PicIds, and a DPB update; recovery-
point SEI parsing is new code (upstream reads no SEI payloads).
Concealment posture, deliberately different from upstream's aborts:
frame_num gaps, failed RPLM/MMCO and mis-split AUs degrade to warnings
the session turns into recovery asks, gap placeholders substitute
in-place so ref_idx mapping never shifts, and DPB outputs queued during
a failed AU survive to the next plan.
An adversarial review round fixed 11 findings before this commit;
one was an upstream cros-codecs bug our conformance-window test exposed
(display_resolution double-subtracts the crop offset and underflow-
panics — PROVENANCE deviation #6, worth reporting upstream).
Gates: fmt clean, clippy -D warnings zero, 45+24 tests green on macOS
and the linux/amd64 container.
#![forbid(unsafe_code)] on both crates. Upstream's codec module was one
production unsafe away: build_ref_pic_lists turned DPB borrows into
indices via pointer offset_from — same pointer-identity mapping now
expressed as position(ptr::eq) over the <=16-entry DPB (PROVENANCE #5).
Three test-only mem::zeroed() asserts became Default::default(), an
identical value for the all-integer PredWeightTable.
Honest coverage note: build_ref_pic_lists has no callers inside the
vendored subset (its consumer was the non-vendored stateless layer), so
the rewrite is equivalence-by-construction until the DecodePlan layer
exercises it against goldens.
M1 of design/client-native-decode.md. The vendored snapshot (AOSP mirror
main @ 5ff6d693ffae, BSD-3, PROVENANCE.md) is the codec module only —
H.264/H.265/AV1/VP9 parsers, DPBs and their test vectors, which now run
as 45 conformance tests in our CI. pf-bitstream sits where upstream's
Linux-only decoder::stateless half would and starts with vendor-pinning
smoke tests: a re-sync that shifts parser behavior trips in-tree, not in
a decode session.
enricobuehler