Not sure if this will help in your case, but it did help for me... I noticed the graphics improved after I upgrade the BIOS. There is no more tearing when I watch the video from a browser.
What version is your BIOS? I was using version 25 and it worked pretty well. Just saw that there is a newer version (27), not sure what are the changes as there is no change log. But you should give it a try.
Even though I am not a Linux expert, I think you should try updating the video player. Another good step is to test another video player such as VLC or banshee for instance.
My best recommendation is to post your question also in the Ubuntu Community for further information: