[FFmpeg-user] Audio out of sync

[iburman at compuscience.com]

I have multiple mp4 files taken with a cellphone which I concatenate.

Playing the concatenated file in a chrome browser, at some point in the
middle of the file I start to see the audio starting to get out of sync, and
the problem increases as we move to the end of the file. It isn't a large
difference but noticeable.

Some facts

1 - I tested the file in chrome, both when placed in a web site (through the
internet) as well as from my local drive. Both show the async issue.

2 - If I use the player controls to stop the video in the middle, advance
the cursor a little bit, and restart playing, the audio is back in sync. In
other words, the async only happens when playing the file from start to end
without interruption.

3 - Playing the video in media player doesn't have this problem. 

 

What could be causing this and how can I fix it? t

 

I was hopping that the async command in ffmpeg could magically fix the
problem, but it didn't make a difference. I tried to use it in the two ways
below:

 

ffmpeg -i inputFile -async 1  outputFile

and

ffmpeg -async 1   -i inputFile outputFile

 

Although the problem only happens in chrome, I believe the issue is in the
file itself. Most of my files work perfectly fine in chrome and media
player, it is just this one that presents this problem.

 

Any ideas on how to find the cause and how to fix it? I think that the fact
described in (2) above, where the problem goes away when I stop the player
and restart playing from a new position, shows that the time stamps seem to
be fine, but maybe chrome doesn't use them the same way as media player, and
it just accumulates some small errors, considering that this is a
concatenation of multiple small files.

 

Thanks