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.
enricobuehler
0a359525a7