It happens whenever the PARSER_FLAG_COMPLETE_FRAMES is set (it is for Matroska), because unesc_index is never reset in this case after having
#8515: vc1_parser erroneously flagged every packet as keyframe -------------------------------------+------------------------------------- Reporter: HolyWu | Owner: (none) Type: defect | Status: open Priority: important | Component: avcodec Version: git-master | Resolution: Keywords: vc1 | Blocked By: regression | Blocking: | Reproduced by developer: 0 Analyzed by developer: 0 | -------------------------------------+------------------------------------- Comment (by Balling): Replying to [comment:4 mkver]: parsed the first frame. Can you fix it? Or just revert 701e8b42e12ad625c64ceae2252acb1de390278c. -- Ticket URL: <https://trac.ffmpeg.org/ticket/8515#comment:5> FFmpeg <https://ffmpeg.org> FFmpeg issue tracker