Yesterday I was trying to view a DVD on Ubuntu, but was getting an error stating that the DVD was encrypted, but there was no DVD decryption library available.
It turns out that its easy to add the relevant decryption libraries as this link describes.
From a terminal window, the steps to getting the relevant software installed to play a DVD are:
$ sudo apt-get install ubuntu-restricted-extras $ sudo /usr/share/doc/libdvdread4/install-css.sh
After executing those commands, you should be able to play DVDs correctly.