This is a revised edition of my original post on compiling ffmpeg on Ubuntu.
update: seems to work in Hardy too.
The excellent Flashvideo module in Drupal uses ffmpeg to convert uploaded video to Adobe Flash Video format (.flv).
However, we’re using Ubuntu based servers and Ubuntu has a strict policy not to include non-free software. This means that the ffmpeg version in the repositories is not built with essential functionality, like mp3 support for audio conversion.
Solution: compile from source. Don’t run away screaming. It’s real easy.