[FFmpeg-trac] #9641(avformat:new): Matroska duplicate tags are only output once instead of repeated

[FFmpeg]

#9641: Matroska duplicate tags are only output once instead of repeated
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             Reporter:  the-black-   |                    Owner:  (none)
  eagle                              |
                 Type:  defect       |                   Status:  new
             Priority:  normal       |                Component:  avformat
              Version:  unspecified  |               Resolution:
             Keywords:  matroska     |               Blocked By:
  metadata                           |
             Blocking:               |  Reproduced by developer:  0
Analyzed by developer:  0            |
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Comment (by Matthew):

 Observations:

 * In `read_tag` (`libavformat/ffmetadec.c`), the call to `av_dict_set`
 should probably just use the `` flag, period.

 * The invocation of `av_copy_dict` in `copy_metadata`
 (`fftools/ffmpeg_mux_init.c`) seems suspect. IIUC, the existing metadata
 of the ''output'' entity (stream, chapter, etc.) is preserved in favor of
 the input entity. This doesn't seem like the desired behavior? In any
 case, this needs to change somehow to support duplicate tags from the
 input.

 * The above changes are an improvement, but duplicate tags are still
 getting lost somewhere. It's not obvious to me at this point where.

 {{{
 Stream mapping:
   Stream #0:0 -> #0:0 (copy)
 Output #0, opus, to 'redacted.opus':
   Metadata:
     TITLE           : redacted
     TRACKNUMBER     : 09
     ALBUM           : redacted
     ARTIST          : redacted
     TRACKTOTAL      : 12
     METADATA_BLOCK_PICTURE: long base64 string
     METADATA_BLOCK_PICTURE: long base64 string
     encoder         : Lavf61.0.100
   Stream #0:0(eng): Audio: opus, 48000 Hz, stereo, fltp (default)
       Metadata:
         TITLE           : redacted
         TRACKNUMBER     : 09
         ALBUM           : redacted
         ARTIST          : redacted
         TRACKTOTAL      : 12
         METADATA_BLOCK_PICTURE: long base64 string
         encoder         : Lavf61.0.100
 }}}
-- 
Ticket URL: <https://trac.ffmpeg.org/ticket/9641#comment:3>
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