[FFmpeg-user] video stream out of sync

Adrian Dusa dusa.adrian at gmail.com
Tue Apr 19 15:29:32 CEST 2011

On Tue, Apr 19, 2011 at 14:49, Anthony Brown <av at bsbc.nb.ca> wrote:
> On 11-04-19 08:43 AM, Adrian Dusa wrote:
>> Oh, I just edited the mp3 file with Audacity, saved it as constant
>> bit-rate and got the very same output from ffmpeg -i.
>> So the short answer is yes, the file is constant bit-rate. Would this
>> explain the video desync?
> Maybe you need to experiment with the -async and/or -vsync settings? I've
> find conversions get totally out of whack without async.

Oh, that might be one solution, only from the man of ffmpeg I am
unable to figure out what values of the async stretch or squeeze.

Alternatively, I could try to grab both audio and video in the mkv
file. I tried:
ffmpeg -f alsa -ac 2 -i pulse

This records the input from the microphone, and I need to grab what's
being presented on the screen (along with the video file). I do have
the original audio (a .flv file), but since I bump into these syncing
problems I might try to grab them both.

So basically now I have two questions:
- what are the values for the async for stretching/squeezing of the
audio stream?
- how to grab the "desktop" sound instead of the "mic" sound?

Thanks again,

More information about the ffmpeg-user mailing list