[FFmpeg-trac] #8791(undetermined:new): Metadata will not copied over going from opus to mp4

[FFmpeg]

#8791: Metadata will not copied over going from opus to mp4
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             Reporter:  Tupsi        |                     Type:  defect
               Status:  new          |                 Priority:  normal
            Component:               |                  Version:  git-
  undetermined                       |  master
             Keywords:  opus, mp4,   |               Blocked By:
  metadata                           |
             Blocking:               |  Reproduced by developer:  0
Analyzed by developer:  0            |
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 Summary of the bug:
 I noticed that when I change containers and codecs for an audio file that
 for some combination the metadata gets lost in transit.
 For instance reencoding an audio file from aac (inside an mp4 container)
 to opus works fine, copying over all relevant meta data like album,
 artist, genre, date, title, comment, etc.
 e.g.
 ffmpeg -i input.m4b -c:a libopus -b:a 32k output.opus
 works, all meta is copied.
 ffmpeg -i input.m4b -c:a libopus -b:a 32k output.mp4
 works as well, all meta is copied.

 Now if you copy the mentioned .opus above back into an mp4 container, the
 information is lost.

 ffmpeg -i output.opus -c:a copy newoutput.mp4

 file runs fine (audio wise), but all meta is lost.

 No idea, which component is doing this, so I will leave that to you guys
 to change, sorry for that.

 How to reproduce:(you need the opus to have a few metadata like album,
 comment)
 {{{
 % ffmpeg -i input.opus -c:a copy output.mp4
 ffmpeg version git-2020-07-15-a54b367
 built on with gcc 9.3.1 (GCC) 20200621
 }}}
 Patches should be submitted to the ffmpeg-devel mailing list and not this
 bug tracker.

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Ticket URL: <https://trac.ffmpeg.org/ticket/8791>
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