[FFmpeg-trac] #2325(undetermined:new): MP4 AAC Audio is delayed by 2ms when converted to PCM

FFmpeg trac at avcodec.org
Wed Mar 6 00:16:59 CET 2013

#2325: MP4 AAC Audio is delayed by 2ms when converted to PCM
             Reporter:  brchapman    |                    Owner:
                 Type:  defect       |                   Status:  new
             Priority:  important    |                Component:
              Version:  git-master   |  undetermined
             Keywords:  aac mov      |               Resolution:
  regression                         |               Blocked By:
             Blocking:               |  Reproduced by developer:  0
Analyzed by developer:  0            |

Comment (by brchapman):

 Replying to [comment:4 cehoyos]:
 > If there is an issue, it is a regression since 1edea05
 Just tried pulling that revision, and building. I still get the same

 > Could you explain how you know that the delay is a bug?
 When converting through After Effects, I don't get this delay. Everything
 lines up exactly in the output wave file.

 > What is the other application you are testing?
 Adobe After Effects

 > Do you see the same problem if you extract the audio stream from the mov
 file with "ffmpeg -i test100.mp4 -acodec copy out.aac" ? Ie, is the
 problem in any way related to the container or only to aac?
 No, I don't get the delay. It lines up perfectly.

 I see the same delay when decoding the extracted aac file with FFmpeg, but
 does your reference application also decode the extracted aac file without
 this delay?
 After Effects decodes it without the delay.
 However, I just noticed that when exporting a wave file from the mp4 using
 Quicktime 7 Pro, it's audio delay was reversed.  The Quicktime's audio is
 2ms ahead of the source, whereas ffmpeg's audio is 2ms behind the source.

 If there is an alternate solution using command line flags, I'd be up for
 that as well.  Just trying to figure out how to make sure the source and
 output audio lines up exactly.

Ticket URL: <https://ffmpeg.org/trac/ffmpeg/ticket/2325#comment:6>
FFmpeg <http://ffmpeg.org>
FFmpeg issue tracker

More information about the FFmpeg-trac mailing list