[FFmpeg-trac] #4313(undetermined:new): Duplication of time stamps when muxing files in a matroska container

[FFmpeg]

#4313: Duplication of time stamps when muxing files in a matroska container
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             Reporter:  lpaone       |                    Owner:
                 Type:  defect       |                   Status:  new
             Priority:  normal       |                Component:
              Version:  git-master   |  undetermined
             Keywords:  matroska,    |               Resolution:
  muxing, ffmpeg                     |               Blocked By:
             Blocking:               |  Reproduced by developer:  0
Analyzed by developer:  0            |
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Comment (by rbultje):

 This is because the vp9 parser (which should really be a bitstream filter)
 splits superframes into frames (to split the altref/invisible reference
 frame from the following/visible frame). But when muxing the file back to
 matroska, we don't merge altref frames together into superframes with
 their subsequent visible frame, which causes the discrepancy.

 The correct fix is to write a bitstream filter that undoes vp9_parser's
 superframe splitting and use that before muxing vp9 into any output file
 type, be that ivf, webm or something else.

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Ticket URL: <https://trac.ffmpeg.org/ticket/4313#comment:1>
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