[Issue description edited to avoid accidentally spreading false information.]

Sadly, the ffmpeg project forked into avconv, and Ubuntu and Debian switched to avconv. (Here is a reasonably unbiased version of the history behind this.)

So, for a 1.0 release ly2video should probably support avconv in addition to ffmpeg. Perhaps the best way to do this would be for ly2video to look for avconv first and, if not found, look for ffmpeg.