[FFmpeg-trac] #4632(avformat:new): The mov demuxer doesn't support bad data offsets in tfhd/trun

[FFmpeg]

#4632: The mov demuxer doesn't support bad data offsets in tfhd/trun
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             Reporter:  RedDwarf  |                     Type:  enhancement
               Status:  new       |                 Priority:  wish
            Component:  avformat  |                  Version:  git-master
             Keywords:  mov       |               Blocked By:
             Blocking:            |  Reproduced by developer:  0
Analyzed by developer:  0         |
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 In this sample
 http://btskprobe.edgesuite.net/BigBuckBunny/Big%20buck%20bunny.ism/QualityLevels(2436000)/Fragments(video=0)

 Which
 "http://btskprobe.edgesuite.net/BigBuckBunny/Big%20buck%20bunny.ism/Manifest"
 says was created with "Expression Encoder version 2.1.1216.0". Neither the
 tfhd or trun boxes specify a data offset. No discussion, the file is
 broken. But apparently they are on the wild...

 VLC is able to play the stream correctly. From what I understand simply
 because it ignores data offsets. It just looks for sample sizes, looks for
 the mdat box and is happy with it.

 It would be nice if libavformat would better handle these files. I guess a
 check could be added to see if the sample->pos is inside the (first) mdat
 box. If it isn't, use as implicit offset the start of the mdat box instead
 of the one from the moof.

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Ticket URL: <https://trac.ffmpeg.org/ticket/4632>
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