Quoting James Almer (2020-03-18 17:05:38) > On 3/13/2020 7:28 AM, Anton Khirnov wrote: > > It represents the relationship between them more naturally and will be > > useful in the following commits. > > > > Allows significantly more frames in fate-h264-attachment-631 to be > > decoded. > > That sample is odd. It has an SPS/PPS pair in extradata that's wrong for > the Buffering Period and Picture Timing SEI messages in-band, but > seemingly correct to actually decode all these frames revealed by this > patch. > The SPS that makes the aforementioned SEI messages parseable, but the > frames seemingly undecodeable, is in-band in the second RAP (Which fwiw > reports a different bitstream level). So this patch prevents the > extradata PPS from using the in-band SPS after it replaced the extradata > one in sps_list. There's no PPS in-band. > > Is this really intended? Is the active PPS' sps_id meant to reference > the SPS with that id that's currently "valid" and in sps_list, or the > whichever one was valid at the time the PPS was first parsed?. If the > latter, then why replace the SPS in-band but never the PPS? > The in-band SPS is virtually unused after this change.
My guess would be that someone (or some/thing/, dun dun dun) did some botched/misunderstood processing on that sample, so trying to figure out what was intended is futile. According to the spec, SPS contents must not change within a sequence (they can change on sequence boundaries), so this sample is invalid. From a more practical viewpoint, since a PPS is parsed for a given SPS I'd say it is clearer, cleaner and safer to tie them together like I'm doing in this patch. > > > --- > > libavcodec/h264_ps.c | 29 +++++- > > libavcodec/h264_ps.h | 3 + > > libavcodec/h264_slice.c | 14 +-- > > Missing changes to h264_parser.c, and one "h->ps.sps == (const > SPS*)h->ps.sps_list[h->ps.pps->sps_id]->data" check in h264dec.c Good catch, fixed locally. -- Anton Khirnov _______________________________________________ ffmpeg-devel mailing list ffmpeg-devel@ffmpeg.org https://ffmpeg.org/mailman/listinfo/ffmpeg-devel To unsubscribe, visit link above, or email ffmpeg-devel-requ...@ffmpeg.org with subject "unsubscribe".
