I have an IBM Thinkpad T42, with a Radeon Mobility 7500 graphics chipset. On all versions of Ubuntu that I have tried (Natty, Xubuntu 11.10), playing any video(e.g a DVD in vlc) causes tearing, whether full screen or not. Furthermore, playing videos under a composited desktop (e.g. Metacity or Xfwm compositing) results in very poor framerate.
I have found a way to improve the performance massively: I have made a custom setting for the radeon driver. This is my /etc/X11/xorg.conf.d/20-radeon.conf
Section "Device"
Identifier "Radeon"
Driver "radeon"
Option "SWcursor" "off" #software cursor might be necessary on some rare occasions, hence set off by default
Option "EnablePageFlip" "on" #supported on all R/RV/RS4xx and older hardware and set off by default
Option "AccelMethod" "EXA" #valid options are XAA and EXA. EXA is the newest acceleration method and its the default.
Option "RenderAccel" "on" #enabled by default on all radeon hardware
Option "ColorTiling" "off" #enabled by default on RV300 and later radeon cards.
Option "EXAVSync" "off" #default is off, otherwise on
Option "EXAPixmaps" "on" #when on icreases 2D performance, but may also cause artifacts on some old cards
Option "AccelDFS" "on" #default is off, read the radeon manpage for more information
EndSection
The key option that makes the difference is the EXAPixmaps, which increases the performance a lot.
