On Tue, Jun 25, 2013 at 19:56:23 +0200, jacky wrote: > 1. demux video , demux audio > 2. run lame to find out the sound level Have you seen ffmpeg's volumedetect filter? http://www.ffmpeg.org/ffmpeg-filters.html#volumedetect The example says it all. Like Bouke writes though, you need to do two-pass, but all within ffmpeg. Moritz