If you have just installed Ubuntu or some other Ubuntu flavors like Kubuntu, Lubuntu etc, you’ll notice that your system doesn’t play some audio or video file. For video files, you can install VLC on Ubuntu. VLC one of the best video players for Linux and can play almost any video file format. But you’ll still have troubles with audio media files and flash player.
The good thing is that Ubuntu provides a single package to install all the essential media codecs: ubuntu-restricted-extras.
[Source: It’s FOSS]