Antes é necessário saber se já tem os codecs instalados : w32codecs (ou w64codecs) + gstreamer.
Instalando ubuntu-restrictec-extras instala-se todos os gstreamer.
Para w32codecs (ou w64codecs) :
wget -c http://packages.medibuntu.org/pool/non-free/w/w32codecs/w32codecs_20071007-0medibuntu2_i386.deb
sudo dpkg -i w32codecs_20071007-0medibuntu2_i386.deb
ou
wget -c http://packages.medibuntu.org/pool/non-free/w/w64codecs/w64codecs_20071007-0medibuntu1_amd64.deb
sudo dpkg -i w64codecs_20071007-0medibuntu1_amd64.deb