[FFmpeg-trac] #6366(undetermined:new): tracks lengths are not frame accurate for non-compressed codecs

FFmpeg trac at avcodec.org
Tue May 2 21:35:21 EEST 2017

#6366: tracks lengths are not frame accurate for non-compressed codecs
             Reporter:  rprowel       |                     Type:  defect
               Status:  new           |                 Priority:  normal
            Component:  undetermined  |                  Version:  3.1.7
             Keywords:  audio drift   |               Blocked By:
             Blocking:                |  Reproduced by developer:  0
Analyzed by developer:  0             |
 Summary of the bug:

 I do a lot of transcoding from AVCHD to QT wrapper containing MJPEG and
 pcm16le two channel audio.  This gives me a good I-frame format for
 nonlinear editing on a timeline based editor.  The resultant stream
 "usually" ends up with audio tracks that do not match the video in length
 to a frame specific boundry.  Concatenation of these clips with incorrect
 audio length causes the audio to skew.  I've verified ffmpeg output with
 over 100ms skew and of course the effect is cumulative when concatenating

 For uncompressed audio of 48khz there is adequate bandwidth to sample at
 greater than 30fps, even in stereo.

 ie. cinellera-cv

 Workarounds are shunned.  This is incorrect behaviour in the context I've
 outlined.  The cinelerra folks have acknowledged and are fixing this in
 their internal use of codecs from an API, but the problem remains when
 using ffmpeg from the command line.

 How to reproduce:


 cmd="ffmpeg -i $inname -y \
  -acodec pcm_s16be \
  -deinterlace \
  -vcodec mjpeg \
  -q:v 1 \
  -vf ${filters}scale=1280:720 \
  -aspect 1.78 -r 29.97 $outname"
 time $cmd

 verify track lengths using something like exiftool or in a nonlinear

 ffmpeg version ... 3.1.7 (fc24)

 built on ... 2017-02-12

Ticket URL: <https://trac.ffmpeg.org/ticket/6366>
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