[FFmpeg-trac] #11451(undetermined:new): Duplicate frames dropped when copying Theora streams

[FFmpeg]

#11451: Duplicate frames dropped when copying Theora streams
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             Reporter:  Bernat       |                     Type:  defect
               Status:  new          |                 Priority:  normal
            Component:               |                  Version:
  undetermined                       |  unspecified
             Keywords:               |               Blocked By:
             Blocking:               |  Reproduced by developer:  0
Analyzed by developer:  0            |
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 Hi. I'm working on Theora decoding support for Godot. Almost everything is
 working fine except for some kind of video streams.

 Theora encodes duplicate frames (frames identical to the previous one) as
 empty packets. Those empty packets seem to be discarded by FFmpeg when
 doing an operation that involves copying a Theora stream.

 Example: ffmpeg -i input.ogv -c:v copy -a:n copy output.ogv

 I've tried to find the issue in the source code, and although I'm not
 familiar with FFmpeg, I think the issue is here:
 https://git.ffmpeg.org/gitweb/ffmpeg.git/blob/HEAD:/libavformat/oggenc.c#l693

 I've read on some commit that empty packets are dropped to fix some issue
 with FLAC streams but they shouldn't be discarded for Theora streams as
 they encode duplicate frames.

 I hope this can be easily fixed. Thanks in advance. Cheers.
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Ticket URL: <https://trac.ffmpeg.org/ticket/11451>
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