Open Ubuntu software centre - search for codecs - it should find "ubuntu restricted extras" - Select - install you should be OK.
Read the synopsis bellow from Ubuntu software centre - Good Luck
This package depends on some commonly used packages in the Ubuntu multiverse repository.
Installing this package will pull in support for MP3 playback and decoding, support for various other audio formats (GStreamer plug-ins), Microsoft fonts, Java runtime environment, Flash plug-in, LAME (to create compressed audio files), and DVD playback.
Please note that this does not install libdvdcss2, and will not let you play encrypted DVDs. For more information, see https://help.ubuntu.com/community/RestrictedFormats/PlayingDVDs
Please also note that packages from multiverse are restricted by copyright or legal issues in some countries. See http://www.ubuntu.com/ubuntu/licensing for more information.