A parity and smoke harness for AV1, mirroring the H.264 and H.265 legs that
proved those rungs bit-identical to libavcodec on four drivers before either
ran on glass. This was the milestone's largest test gap: the adversarial
review found four blocking defects in the AV1 conversion — flags unset on
274 frames of 274, a units error in LoopRestorationSize, per-reference info
describing the wrong picture, film-grain fields left zero — and every one of
them would have shown on frame 1 of a parity run, while clippy and 164 green
unit tests said nothing at all.
The golden is 250 per-frame SHA-256s in DISPLAY order, not 274. The vector
carries 274 coded frames in 250 temporal units; the 24 extras are hidden
ALTREFs, decoded and referenced but never shown, and the rung delivers what
dpb.outputs names. The count is re-derived from the planner rather than
assumed.
Cross-checked between ffmpeg 8.1.1 on macOS arm64 and 8.0.1 on Linux x86_64,
whose raw outputs are byte-identical — and then against a third party neither
build knows about: the vendored vector ships upstream's own per-frame MD5s,
and re-running those reproduces all 250. The golden agrees with a decode
nobody in this program performed. I reproduced both independently before
committing.
8-bit NV12, traced from the sequence header rather than presumed
(seq_profile 0, high_bitdepth 0, mono_chrome 0), so the P010 scar does not
apply here — and the header says which check to make if a Main 10 golden is
ever added. film_grain_params_present is 0, which is load-bearing: grain
synthesis is part of the Vulkan decode profile, so this golden is only
comparable against a grain-less profile key.
Anti-vacuity is the point of the exercise, so it is structural. The golden
guard asserts the exact count, that every line is a bare digest, and that all
entries are DISTINCT — 250 copies of one digest would let a decoder frozen on
a single frame pass parity. The parity body asserts the golden set and the
access-unit count before it touches hardware, so an IVF reader returning
nothing cannot become "0 frames compared, pass". The agent verified the
guards fire by mutating the golden three ways.
assert_bit_identical now names the FIRST divergent frame, which is what
localises a defect; that improves all six legs, not just AV1.
AV1 has no four-byte-start-code twin, deliberately: OBUs are
length-delimited, so there is no prefix for a driver to mis-skip. Documented
where a reader would otherwise see an omission.
Nothing here has run on a GPU. The harness exists precisely so the four
review defects can be answered by measurement instead of argument.
enricobuehler
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