Eyevinn / hi264 / 37927748890

88%

main: 88%

Build Type

Pull #36

github

Committed by tobbee

Commit Message

feat: decode IDR pictures carried by several slices

The decoder took the first IDR NAL unit for the whole picture: DecodeNALUs returned after it, and the slice data loops decoded mbWidth*mbHeight macroblocks from that one slice. A picture split into slices lost every slice but the first. Under CABAC it decoded with no error and wrong pixels; under CAVLC it failed at the second slice's first macroblock.

Each slice is now decoded from its first_mb_in_slice into a SliceContext shared by the picture, until end_of_slice_flag (CABAC) or more_rbsp_data() (CAVLC), with the QP and the CABAC engine and contexts reset per slice. The picture is reconstructed and deblocked once its slices cover every macroblock, so neither an access unit delimiter nor a look-ahead to the next picture is needed. A missing slice, a macroblock decoded twice, or a new picture (clause 7.4.1.2.4) starting before the current one is complete returns an error instead of a frame with gaps. Redundant slices are skipped, and slice groups (FMO) are rejected, since their macroblocks are not in raster order.

A macroblock in another slice is not available (clause 6.4.8). MBAvailA/B, and the new MBAvailC/D, compare slice numbers, which covers every CABAC and CAVLC context, and reconstruction takes intra sample availability from them instead of from the position in the picture. The Intra_8x8 reference filter now follows clause 8.3.2.2.1 directly: substituting unavailable samples and then filtering gave a wrong p'[0,-1] when p[-1,-1] is not available but p[-1,0] is, which only happens at a slice boundary. Deblocking uses the disable_deblocking_filter_idc and filter offsets of each macroblock's own slice, and leaves slice edges unfiltered for idc 2.

Group 13 of gen_and_verify.sh adds nine golden streams, all bit-exact with FFmpeg: x264 slices starting at row starts and mid-row, one macroblock per slice and limited by bytes, in CABAC and CAVLC, and two streams where tools/mix_slice_deblock gives e... (continued)

Pull Request Pull Request #36: feat: decode IDR pictures carried by several slices

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