[FFmpeg-trac] #10109(ffmpeg:new): Volume gradually increasing when adding several audios in video

[FFmpeg]

#10109: Volume gradually increasing when adding several audios in video
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             Reporter:  gregoryd       |                     Type:  defect
               Status:  new            |                 Priority:  normal
            Component:  ffmpeg         |                  Version:  4.4.3
             Keywords:  audio, volume  |               Blocked By:
             Blocking:                 |  Reproduced by developer:  0
Analyzed by developer:  0              |
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 This is a reproductible bug, this is an example command:

 ffmpeg -y -i silentvideo.mp4 -itsoffset 1 -i audio.mp3 -itsoffset 3 -i
 audio.mp3 -itsoffset 5 -i audio.mp3 -itsoffset 7 -i audio.mp3 -itsoffset 9
 -i audio.mp3 -itsoffset 11 -i audio.mp3 -itsoffset 13 -i audio.mp3
 -itsoffset 15 -i audio.mp3 -itsoffset 17 -i audio.mp3 -itsoffset 19 -i
 audio.mp3 -itsoffset 21 -i audio.mp3 -itsoffset 23 -i audio.mp3 -itsoffset
 25 -i audio.mp3 -filter_complex amix=inputs=13[a] -map 0:v -map [a] -c:v
 copy -async 1 -c:a aac output.mp4 2>&1

 use a 30 seconds long silent video for silentvideo.mp4 and a 1 second mp3
 for audio.mp3 and you'll hear the volume increasing again and again until
 the end.
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Ticket URL: <https://trac.ffmpeg.org/ticket/10109>
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