[FFmpeg-trac] #5078(ffmpeg:new): FFMPEG "loop=0" value results in warnings and extremely long runtime

[FFmpeg]

#5078: FFMPEG "loop=0" value results in warnings and extremely long runtime
--------------------------------+----------------------------------
             Reporter:  eric    |                     Type:  defect
               Status:  new     |                 Priority:  normal
            Component:  ffmpeg  |                  Version:  2.8.3
             Keywords:          |               Blocked By:
             Blocking:          |  Reproduced by developer:  0
Analyzed by developer:  0       |
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 Summary of the bug:
 When attempting to replace the audio stream of an MP4 video with looping
 MP3 audio, FFmpeg begins going very slowly and generating warnings like
 the one below at the point when the audio starts looping.
 {{{
 [mp4 @ 0x7fd80a00e200] Non-monotonous DTS in output stream 0:1; previous:
 678336, current: 832; changing to 678337. This may result in incorrect
 timestamps in the output file.
 }}}

 How to reproduce:
 {{{
 % ffmpeg -i video.mp4 -f lavfi -i "amovie=filename=audio.mp3:loop=0" -map
 0:v -map 1:a -shortest -c:v copy output.mp4
 }}}

 Running the above command takes ~5 minutes for a 30 second video.mp4 and a
 15 second audio.mp3.  The resulting video at face value appears to be
 correct (it plays correctly, the audio was replaced, and the audio loops
 as expected).

 If I remove the "loop=0" option, the resulting output.mp4 is only 15
 seconds (as expected since the audio doesn't loop), but it's generated in
 less than 0.5 seconds on my machine.

 Attached report file has the result of running the command with "-v 9
 -loglevel 99 -report" options also specified.  The resulting report was
 over 100 MB (due to all the warnings) so I replaced the majority of them
 with "..." to keep the file size down.

 Tested with FFMPEG 2.8.3 on Mac OS X 10.11.1.

 Possibly related to:
 https://trac.ffmpeg.org/ticket/1799
 https://trac.ffmpeg.org/ticket/1670
 https://trac.ffmpeg.org/ticket/3315

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Ticket URL: <https://trac.ffmpeg.org/ticket/5078>
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