The matroska specification states the start time and duration of subtitle entries are encoded in the block TimeStamp and BlockDuration. Furthermore, for all subtitle formats except S_HDMV/PGS the BlockDuration must always be defined and have an absolute value even if it is simply 0. ffmpeg assumes that a duration of 0 means the duration is still unknown and tries to adjust based on the next packet pts. This is wrong for all formats except S_HDMV/PGS. Since changing the semantics of duration 0 is not an option (touches too many parts of the code) this change introduces AV_PKT_FLAG_FIXED_DURATION flag which decoders might use to flag the duration of a given packet should not be changed.
Signed-off-by: Miguel Borges de Freitas ene...@kodi.tv ---------------------------------------------------------------------------- This is my attempt at fixing https://trac.ffmpeg.org/ticket/10135 Initially reported to Kodi in https://github.com/xbmc/xbmc/issues/21625 Miguel Borges de Freitas (2): libavformat/matroskadec: set fixed duration for subtitles fate: update test reference data to include AV_PKT_FLAG_FIXED_DURATION libavcodec/packet.h | 5 ++ libavformat/demux.c | 3 +- libavformat/matroskadec.c | 4 + tests/ref/fate/matroska-dvbsub-remux | 84 ++++++++++---------- tests/ref/fate/matroska-zero-length-block | 4 +- tests/ref/fate/matroska-zlib-decompression | 2 +- tests/ref/fate/shortest-sub | 92 +++++++++++----------- 7 files changed, 102 insertions(+), 92 deletions(-) base-commit: 94aa70d757af6b0e0919250f9def2a819aa00358 Published-As: https://github.com/ffstaging/FFmpeg/releases/tag/pr-ffstaging-48%2Fenen92%2Fass_mkv_fixed_subs-v1 Fetch-It-Via: git fetch https://github.com/ffstaging/FFmpeg pr-ffstaging-48/enen92/ass_mkv_fixed_subs-v1 Pull-Request: https://github.com/ffstaging/FFmpeg/pull/48 -- ffmpeg-codebot _______________________________________________ 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".
