[FFmpeg-trac] #4904(undetermined:new): Broken vp9 decoding after failed seek in webm file

[FFmpeg]

#4904: Broken vp9 decoding after failed seek in webm file
-------------------------------------+-------------------------------------
             Reporter:  cehoyos      |                    Owner:
                 Type:  defect       |                   Status:  new
             Priority:  normal       |                Component:
              Version:  git-master   |  undetermined
             Keywords:  mkv vp9      |               Resolution:
  seek                               |               Blocked By:
             Blocking:               |  Reproduced by developer:  0
Analyzed by developer:  0            |
-------------------------------------+-------------------------------------

Comment (by gjdfgh):

 Looking at this closer...
 - the file has only 1 index entry for video, pointing to the first packet
 - the video could indeed have only 1 keyframe (didn't check)
 - libavformat's demuxer "gives up" and does an *incorrect* seek (probably
 a fix for other broken files produced by lavf, I seem to remember a
 specific one)
 - the incorrect seek of course confuses the decoder, because the decoder
 only gets midstream packets
 - the correct behavior is seeking to the correct index entry, and decoding
 the video until the seek target is reached

 The latter is confirmed to work with lavfilters and mpv.

--
Ticket URL: <https://trac.ffmpeg.org/ticket/4904#comment:3>
FFmpeg <https://ffmpeg.org>
FFmpeg issue tracker