Installing Codecs (Medibuntu: Restricted and not-default)
[all variants] Comprehensive Multimedia & Video How-to

64-Bit Ubuntu Users:

sudo apt-get install gstreamer0.10-plugins-bad
sudo apt-get install gstreamer0.10-plugins-bad-multiverse
sudo apt-get install gstreamer0.10-plugins-ugly
sudo apt-get install gstreamer0.10-plugins-ugly-multiverse
sudo apt-get install gstreamer0.10-ffmpeg
sudo apt-get install ia32-libs
sudo apt-get install icedtea6-plugin
sudo apt-get install libavcodec-unstripped-51
sudo apt-get install libmp3lame0

sudo apt-get install alsa-oss
sudo apt-get install faac
sudo apt-get install faad
sudo apt-get install non-free-codecs

Only for audio/video converting

sudo apt-get install mjpegtools
sudo apt-get install sox

sudo apt-get install ffmpeg
sudo apt-get install flac
sudo apt-get install lame
sudo apt-get install vorbis-tools