[FFmpeg-trac] #10065(ffmpeg:new): Gap in video by -c copy in mkv opus

[FFmpeg]

#10065: Gap in video by -c copy in mkv opus
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             Reporter:  yumu        |                    Owner:  (none)
                 Type:  defect      |                   Status:  new
             Priority:  normal      |                Component:  ffmpeg
              Version:  git-master  |               Resolution:
             Keywords:  mkv opus    |               Blocked By:
             Blocking:              |  Reproduced by developer:  0
Analyzed by developer:  0           |
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Changes (by yumu):

 * keywords:   => mkv opus

Comment:

 Replying to [comment:1 mkver]:
 > Did you do all your tests with git-master? There have been changes since
 the last release in this area and with these changes there is no longer
 desynchronisation between audio and video and the shift only happens once
 (namely when creating a_opus_copy.mkv, not when remuxing it). This last
 shift can be avoided by using the -copyts option to create
 a_opus_copy.mkv.
 I did all my tests with the build on Nov 22nd at 12:00 UTC. So I don't
 think it is strictly git-master. However, I chose git-master because it
 was the closest option.

 When I copy using the -copyts option, the video does not shift anymore.
 Thank you!

 By the way, could you please explain what is happening? Without the
 -copyts option, what happens inside ffmpeg to cause the video to shift?
 I could see in the documentation that it is through demuxer and muxer, but
 I couldn't figure out what exactly demuxer and muxer are doing.
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Ticket URL: <https://trac.ffmpeg.org/ticket/10065#comment:2>
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