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

FFmpeg trac at avcodec.org
Wed Mar 6 00:53:30 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 cehoyos):

 Replying to [comment:6 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

 Since it is a regression since that revision, you will have to test an
 earlier version;-)

 > > 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.

 How does it "line up"? (I don't understand how the numbers should relate
 to the sound. I am certainly not claiming there is no issue - I don't know
 - but since we know already of three - very different - applications that
 decode the sample differently from After Effects, I wonder how you can be
 sure that it is correct.)

 > > 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.

 You mean you get the same delay if you use FFmpeg but no delay with After
 Effects if you try with the aac file - or do I misunderstand?

Ticket URL: <https://ffmpeg.org/trac/ffmpeg/ticket/2325#comment:7>
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