[FFmpeg-trac] #9337(undetermined:new): 'atempo' didn't work unless '-map 0' was added

FFmpeg trac at avcodec.org
Mon Jul 19 05:27:58 EEST 2021

#9337: 'atempo' didn't work unless '-map 0' was added
             Reporter:  markfilipak  |                     Type:  defect
               Status:  new          |                 Priority:  normal
            Component:               |                  Version:  git-
  undetermined                       |  master
             Keywords:  atempo       |               Blocked By:
             Blocking:               |  Reproduced by developer:  0
Analyzed by developer:  0            |
 1.cmd => ffmpeg -i source.vob -filter_complex
 "[0:v]settb=expr=1/24,setpts=expr=N[v]"                             -map
 "[v]" -map 0:1   -codec:v %AVcoder% -codec:a copy -r 24 1.mkv
 2.cmd => ffmpeg -i source.vob -filter_complex
 "[0:v]settb=expr=1/24,setpts=expr=N[v];[0:a]atempo=1.001[a]"        -map
 "[v]" -map "[a]" -codec:v %AVcoder% -codec:a ac3  -r 24 2.mkv
 3.cmd => ffmpeg -i source.vob -filter_complex
 "[0:v]settb=expr=1/24,setpts=expr=N[v];[0:a]atempo=1.001[a]" -map 0 -map
 "[v]" -map "[a]" -codec:v %AVcoder% -codec:a ac3  -r 24 3.mkv
 4.cmd => ffmpeg -i 3.mkv -map 0:0 -map 0:1 -codec:v copy -codec:a copy
 5.cmd => ffmpeg -i 3.mkv -map 0:2 -map 0:3 -codec:v copy -codec:a copy

 source.vob has a 9-&-1/2 second clip that's repeated 7 more times. The
 clip is soft telecined. And of course, the video and audio are
 1.mkv, 2.mkv, 3.mkv were made by converting the soft telecined source to
 4.mkv, 5.mkv, were made from 3.mkv.

 1.mkv was made just to show that the audio lags the video at the end of
 the 8th clip. Note the boy slamming the door. By the end of the 8th clip,
 it lags by about 1/2 second.
 2.mkv is what I expected would produce synchronized audio, but it fails.
 3.mkv appears to work when played with MPV, but there's an extra video
 track and an extra audio track.

 4.mkv is just the 1st video & audio pair of tracks from 3.mkv.
 5.mkv is just the 2nd video & audio pair.

 4.mkv is what I want, so output tracks 0:0 & 0:1 must be from the graph.
 5.mkv is not what I want, so output tracks 0:2 & 0:3 must be from '-map

 Issue #1: Why does 'atempo' need '-map 0' to work?
 Issue #2: Will what I want always be 0:0 & 0:1?

 source.vob is here:
 1.mkv, 2.mkv, 3.mkv, 4.mkv, 5.mkv are available on request.
 1.log, 2.log, 3.log, 4.log, 5.log are available on request.

 Regards, And Thank You for ffmpeg.
 Mark Filipak.
Ticket URL: <https://trac.ffmpeg.org/ticket/9337>
FFmpeg <https://ffmpeg.org>
FFmpeg issue tracker

More information about the FFmpeg-trac mailing list