libav has already been added to the ubuntu repositories:
What are the implications of the ffmpeg / libav fork for a ubuntu user?
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Please read this, interesting analysis of the situation in 2012: http://blog.pkh.me/p/13-the-ffmpeg-libav-situation.html
Both sides presented their point to Ubuntu Technical Board in an apparent attempt to sell own variant .
'libav' won, which is not surprising since Debian/Ubuntu package maintainer is one of them.
As of Dec 18, 2011 'ffmpeg' has at least one point where it works, and 'libav' doesn't .