Problem: Ubuntu 11.04 (Natty Narwhal) using a Nvidia ION GPU demonstrates stuttering and/or tearing during video playback.
Solution: The underlying cause is the X.org "Composite" extension. This problem may therefore appear on other Linux distributions. Disabling the extension solves the problem. This can be done on Ubuntu with the command:
sudo nvidia-xconfig --no-composite
Alternatively, add these lines to your /etc/X11/x.org.conf file:
Section "Extensions"
Option "Composite" "Disable"
EndSectionWith the composite extension disabled, you will need to log in using either the "Classic (no effects)" or the "Unity 2D" desktop option.