What program are you trying to use to play DVD's? Have you tried VLC,
Realplayer, Ogle, or mplayer??? What type of DVD formate are you trying to
play?
https://help.ubuntu.com/community/RestrictedFormats/PlayingDVDs

https://help.ubuntu.com/community/RestrictedFormats/RippingDVDs

https://help.ubuntu.com/community/RestrictedFormats/BluRayAndHDDVD