[FFmpeg-user] audio is out of sync and "ALSA buffer xrun"

[YuGiOhJCJ Mailing-List]

Hello,

I am using ffmpeg version 1.2.

To record (audio/video) my desktop with ffmpeg, I use this command:
$ ffmpeg -f x11grab -r 15 -s 640x480 -i :0.0 -f alsa -i default out.mkv

Unfortunately, when I am playing this "out.mkv" file on VLC, I can remark that the audio is out of sync.

In the console, I can see some warnings: "ALSA buffer xrun".

Do you see why ?

Thank you.
Best regards.