My wife's camera has the ability to take little movie files. It defaults to capturing in MJPEG format which is really huge, and thus I needed a quick way to convert to something smaller (xvid). I was able to convert a 9.9Mb MJPEG file into a 900Kb Xvid file. Here's the quick conversion:

mencoder input.mpg -o output.avi -ovc xvid -xvidencopts bitrate=600 -oac lavc -lavcopts acodec=mp3:abitrate=64 Or to get a little more complicated here's some code for a multipass Xvid file. export file=/tmp/input.mpg mencoder $file -o output.avi -ovc xvid -xvidencopts pass=1 -oac copy\ mencoder $file -o output.avi -ovc xvid -xvidencopts pass=2:bitrate=600 -oac lavc -lavcopts acodec=mp3:abitrate=64
Or you can use lame to encode

mencoder $file -o output.avi -ovc xvid -xvidencopts pass=1 -oac copy\ mencoder input.mpg -o output.avi -ovc xvid -xvidencopts pass=2:bitrate=600 -oac mp3lame -lameopts br=64
Or if you wanna get really crazy you can read the Gentoo Mencoder page which has a crazy amount of info.