[FFmpeg-trac] #8338(avformat:new): can't copy GoPro metadata

[FFmpeg]

#8338: can't copy GoPro metadata
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             Reporter:  importon     |                    Owner:  (none)
                 Type:  enhancement  |                   Status:  new
             Priority:  wish         |                Component:  avformat
              Version:  git-master   |               Resolution:
             Keywords:  mov          |               Blocked By:
             Blocking:               |  Reproduced by developer:  0
Analyzed by developer:  0            |
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Comment (by Kamil Filipek):

 On v4.0.2, the error is thrown when no `track->par->codec_tag` is found.
 For both .mov & .mp4 format.
 The codec_tag is read in `mov_find_codec_tag(s, track)` function, with
 .mov going down to sub-function `mov_get_codec_tag(s, track)`, where the
 same `codec_tag` parameter is read in case of unidentifiable codec.

 In the branch where v4.2.1 has been released, a `validate_codec_tag`
 function has been introduced. It is not ran when **MODE** is set to MOV,
 but is executed for **MODE** of MP4 files.

 The `validate_codec_tag` only does a simple check if the codec_tag or id
 exists in the white tables.

 As I see the timecode track being a feature exclusive to Apple QuickTime &
 MOV container. I don't see any reason for it to receive preferential
 treatment.
 But, I also don't see a reason for it to not be allowed a copy, if it
 already exists in the container and user explicitly accepts the risks with
 the `copy_unknown` flag.

 So, I propose adoption of `copy_unknown` flag into the
 `validate_codec_tag`, where validation this validation is skipped and the
 stream is copied, just like in the case of MOV container. I'll attempt to
 make a valid commit for this change.
-- 
Ticket URL: <https://trac.ffmpeg.org/ticket/8338#comment:17>
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