Video an mp3 are not working

     I know the problem with mp3 music files comes down to codecs. The can be downloaded for Ubuntu 9.04 and mp3 will work fine. I suggest going through the menu bar "System->Administration->Synaptic Package Manager" and putting "mp3" into the "Quick search" box. You'll need "lame" and can select anything else you want to use to work with mp3 files. Do the same for other formats and see if they come up; some might not, but I can't be sure.
    After the upgrades, you should be fine. Check back with us and let us know if this solves the problem or if you need more help.

Or search in Add/Remove or in Synaptic for ubuntu-restricted-extras. Install that and you should be fine.

Install the Medibuntu packages. Go to https://help.ubuntu.com/community/Medibuntu and follow the instructions there. (Due to legal restrictions in some countries the multimedia codecs are not included by default.) After this you should be able to sudo apt-get install the required codecs, but the responsibility of installing restricted codecs is up to you.

To install multimedia codecs on Ubuntu you need to enable Restricted Formats open the Terminal and submit the following command

sudo apt-get install ubuntu-restricted-extras

Here is the Official Ubuntu Restricted Formats Documentation
https://help.ubuntu.com/community/RestrictedFormats/

LUg.