[FFmpeg-trac] #10879(avformat:new): Backporting "avformat/mov: Ignore duplicate ftyp" patch to 5.1.4

[FFmpeg]

#10879: Backporting "avformat/mov: Ignore duplicate ftyp" patch to 5.1.4
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             Reporter:  alard     |                     Type:  defect
               Status:  new       |                 Priority:  normal
            Component:  avformat  |                  Version:
             Keywords:            |               Blocked By:
             Blocking:            |  Reproduced by developer:  0
Analyzed by developer:  0         |
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 ffmpeg 6.1.0 introduced the following change in avformat/mov:
 https://patchwork.ffmpeg.org/project/ffmpeg/patch/20231108021244.8669-1-michael@niedermayer.cc/

 As indicated in the discussion there, this strict checking caused issues
 with concatenated fragmented MP4 files. For this reason, the following
 patch was introduced in 6.1.1 to ignore duplicate ftyp instances:
 https://patchwork.ffmpeg.org/project/ffmpeg/patch/20231201232603.31423-1-michael@niedermayer.cc/

 All good so far.

 The problem: the first patch was backported to 5.1.4, but the second was
 not. This means that the bug currently still occurs on systems running
 ffmpeg 5.1.x (which is, for example, the current version on Debian 12).

 Would it be possible to apply the second patch also to the 5.1 branch?


 Example file that currently fails on Debian 12, ffmpeg 5.1.4:
 https://storage.googleapis.com/chromiumos-test-assets-public/Shaka-
 Dash/switch_1080p_720p.mp4
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Ticket URL: <https://trac.ffmpeg.org/ticket/10879>
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