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frame_mbs_only_flag == 0 only permits field coding. x264's fake-interlaced (needed for Blu-ray 1080p25/30) sets it while coding every picture as a progressive frame, and those streams were refused at the SPS. Now the SPS reads mb_adaptive_frame_field_flag and refuses only MBAFF; the height is counted in field map units (FrameHeightInMbs = 2 * PicHeightInMapUnits) and the vertical crop unit is 4. Slice headers read field_pic_flag and refuse only field pictures. Everything else about a frame picture decodes as before. Fixes Remade-With-Rust#16. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
A separate decoder, `hbd::HbdDecoder`, next to the optimized 8-bit one so the 8-bit byte-identity gates are untouched. It follows FFmpeg's h264 decoder (neighbour caches, motion vector prediction, direct modes, reference lists, POC) and is bit-exact with it. Scope: progressive 4:2:0, bit depths 8-14, CAVLC and CABAC, I/P/B, 8x8 transform, scaling matrices, explicit and implicit weighted prediction, spatial and temporal direct, long-term references and MMCO. Interlace, 4:2:2/4:4:4, lossless and SP/SI are refused; like the 8-bit decoder, it decodes the frame pictures of a stream that permits field coding and refuses field pictures. A broken internal invariant is `DecodeError::Internal`, not a panic. The SPS now keeps the bit depths and the POC type 1 cycle; the 8-bit Decoder refuses bit depths other than 8 at the slice instead of the SPS. The crop window is computed with checked u64 arithmetic (`Sps::crop_window`), since offsets near u32::MAX used to wrap past the bounds check with overflow checks off. Tests: three x264 High 10 streams (64x48, 8 frames, ffmpeg 8.1's decodes as the `yuv420p10le` references) covering CABAC B-pyramid with explicit and implicit weighted prediction, CAVLC with spatial and temporal direct and PPS scaling matrices, and two slices per picture; every picture is byte-identical. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
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This stacks on #22.
A separate decoder,
hbd::HbdDecoder, next to the optimized 8-bit one so the 8-bitbyte-identity gates are untouched. It follows FFmpeg's h264 decoder (neighbour caches,
motion vector prediction, direct modes, reference lists, POC) and is bit-exact with it.
Scope: progressive 4:2:0, bit depths 8-14, CAVLC and CABAC, I/P/B, 8x8 transform,
scaling matrices, explicit and implicit weighted prediction, spatial and temporal direct,
long-term references and MMCO. Interlace, 4:2:2/4:4:4, lossless and SP/SI are refused;
like the 8-bit decoder, it decodes the frame pictures of a stream that permits field
coding and refuses field pictures. A broken internal invariant is
DecodeError::Internal, not a panic.The SPS now keeps the bit depths and the POC type 1 cycle; the 8-bit Decoder refuses
bit depths other than 8 at the slice instead of the SPS. The crop window is computed
with checked u64 arithmetic (
Sps::crop_window), since offsets near u32::MAX used towrap past the bounds check with overflow checks off.
Tests: three x264 High 10 streams (64x48, 8 frames, ffmpeg 8.1's decodes as the
yuv420p10lereferences) covering CABAC B-pyramid with explicit and implicitweighted prediction, CAVLC with spatial and temporal direct and PPS scaling matrices,
and two slices per picture; every picture is byte-identical.