VLC Media Player is a handy program that can play numerous forms of video, and runs on just about any OS platform. It also runs on Ubuntu 12.04 Precise Pangolin, and installing it is quite simple.
First, open up a Terminal window and type this command:
sudo apt-get install vlc
Enter your password to authenticate, and apt will download and install VLC and its various dependencies for you. (You can also install it through Synaptic Package Manager and Ubuntu Software Center.) Afterwards you can launch VLC by going to your Applications menu, then to Sound & Video, and then selecting VLC Media Player.
Of course, most of the media you watch will probably be found on the Internet, which means you’ll want the VLC plugins for Firefox. Fortunately, the VLC Firefox plug is also easy to install. Return to the Terminal and type this command:
sudo apt-get install vlc vlc-plugin-* mozilla-plugin-vlc
Once you enter your password, apt-get will install the Firefox VLC plugin. You can check that the plugin is installed by going to Firefox, to the Tools menu, and selecting Add-ons. Once in the Add-ons dialog box, you can view all your plugins by hitting the Plugins button. You should see the VLC plugins listed there.
Of course, VLC needs codecs into order to display certain kinds of video. You may need to install the Ubuntu Restricted Extras package in order to get maximum use out of VLC.