[FFmpeg-user] Help: transform 'asyncts=first_pts=0' into new 'aresample' filter

Carl Eugen Hoyos cehoyos at ag.or.at
Sun Feb 3 01:21:55 CET 2013

Frank Häfemeier <ffmpeg <at> frank.haefemeier.eu> writes:

> > > 30s video sample:
> > > http://www.datafilehost.com/download-c12482c8.html
> > 
> > I tested the following command lines:
> > $ ffmpeg -async 1 -i video-sample.ts -qscale 2 out.avi
> > $ ffmpeg -async 1 -i video-sample.ts -qscale 2 -vcodec mpeg4 
> > -strict -2 out.mov
> > 
> > Both out.avi and out.mov play in-sync, both when encoded 
> > with current FFmpeg and an older version.
> What can I learn from your test?

ffmpeg -async 1 has been the recommended way 
of fixing the A/V desync problems you are seeing 
with your input sample for several years (long 
before there was a aresample or asyncts filter).
It still works fine and - afaict - there is nothing 
to "transform".

(Your sample makes me believe that theoretically 
there are samples that will not work with -async 1 
but without such samples to test, this problem is 
very, very difficult to fix as I hope everybody 
will understand.)

Carl Eugen

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