Quelles sont les différences et les similitudes entre ffmpeg, libav et avconv?

Quand je cours ffmpegsur Ubuntu, cela montre: $ ffmpeg ffmpeg version v0.8, Copyright (c) 2000-2011 the Libav developers built on Feb 28 2012 13:27:36 with gcc 4.6.1 This program is not developed anymore and is only provided for compatibility. Use avconv instead (see Changelog for the list of...