[FFmpeg-trac] #2658(avformat:new): Written mp4 with h264/AAC unplayable (discrepancy with libav)

[FFmpeg]

#2658: Written mp4 with h264/AAC unplayable (discrepancy with libav)
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             Reporter:  Lastique  |                    Owner:
                 Type:  defect    |                   Status:  new
             Priority:  normal    |                Component:  avformat
              Version:  1.2.1     |               Resolution:
             Keywords:  mov       |               Blocked By:
             Blocking:            |  Reproduced by developer:  0
Analyzed by developer:  0         |
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Comment (by Lastique):

 Replying to [comment:1 cehoyos]:
 > Please also test current git head.

 The latest snapshot behavior is the same.

 > Is the problem also reproducible with ffmpeg (the application) or only
 if you use library calls from your application?

 We only use the library API in our application, and I'm not sure how I can
 reproduce the same library setup from ffmpeg command line.


 Replying to [comment:2 heleppkes]:
 > Note that it is possible for avformat to change the stream timebase from
 the one you specified when it thinks that another one is more appropriate
 for the format, so you should always rescale your timestamps to the stream
 timebase, or your assumption may go wrong.

 Yes, this seems to be the problem. libav does not modify time_base we set
 in the context initialization, and ffmpeg sets video time_base to be equal
 to the audio time_base. If we use the time_base set by ffmpeg for
 rescaling then the written file is playable. Thanks for the suggestion.

 Frankly, this is an odd feature. Why would the library change settings
 requested by the caller?

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Ticket URL: <https://ffmpeg.org/trac/ffmpeg/ticket/2658#comment:3>
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