[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
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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 |
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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
delay.
> 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.
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Ticket URL: <https://ffmpeg.org/trac/ffmpeg/ticket/2325#comment:6>
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