Some threads from the list that might help contextualize this:

http://thread.gmane.org/gmane.comp.video.ffmpeg.devel/118594

http://thread.gmane.org/gmane.comp.video.ffmpeg.devel/119382

http://thread.gmane.org/gmane.comp.video.ffmpeg.devel/123727

http://thread.gmane.org/gmane.comp.video.ffmpeg.devel/118554