sudo apt-get install ubuntu-restricted-extras
http://en.wikipedia.org/wiki/Ubuntu-restricted-extras
ubuntu-restricted-extras is a software package for the computer operating system Ubuntu that allows the user to install essential software which is not already included due to legal or copyright reasons.
It is a meta-package that installs:
- Support for MP3 and unencrypted DVD playback
- Microsoft TrueType core fonts
- Flash plugin
- codecs for common audio and video files