Tearing occurs when your video player (mplayer-gnome or VLC) doesn't output video correctly. For example, in a moving image, the upper part of the image will appear cut away from the lower part. For example this image.
Fix for gnome-mplayer: (tested in 11.10 and later releases)
- Open Gnome Mplayer
- Open Preferences from Mplayer's menu
- On the Player tab, adjust Video Output to 'GL' (use drop-down menu)
Fix for VLC: (tested in 12.10)
- Open preferences from the 'Tools' menu
- On the video tab, uncheck "Accelerated video output (Overlay)"
- Set Output to "Default"
- Restart VLC