I've found an easy way to play Multimedia files in many formats.
check out this:
https://help.ubuntu.com/community/Medibuntu
follow the steps to add Medibuntu's repository.
This command should be run in the Terminal (Applications → Accessories → Terminal):
sudo wget http://www.medibuntu.org/sources.list.d/$(lsb_release -cs).list \
--output-document=/etc/apt/sources.list.d/medibuntu.list &&
sudo apt-get -q update &&
sudo apt-get --yes -q --allow-unauthenticated install medibuntu-keyring &&
sudo apt-get -q update
enjoy it !!
