I’ve been struggling with flash quite a bit. I like to watch flash videos online because the time I’m able to get to them are usually at odd times of the day. The issue with flash (I’m using the 64bit alpha but think this effects other versions too) is that higher definition flash can often become choppy, and tear – particularly in fullscreen. I read that this has to do with how flash uses Xvideo. I’ve tried numerous hacks I’ve seen around but none that have worked. Flash 64bit alpha has been around coming on 10 months now so hopefully we’ll see an update soon, but until then I did find something that might improve your flash performance a bit. This I found while going through the Ubuntu forums – (thanks to Labello who figured it out). This is just a simple xorg server edit that may on some systems be already enabled. Flash appears to require a couple options that some xorg.confs may not provide. To give an idea on performance, 1080 flash video before was unwatchable sometimes giving me as low as 1 frame every five seconds and 720 video would tear at times. With the edit, low motion 1080 video (yeah I know) like Law and Order is mostly tolerable and 720 is playing without a problem. To get these benefits (will vary from system to system) be sure that these settings are in your xorg.conf and then restart the xorg server.
Section "Extensions" Option "Composite" "Enable" # for 3D, alpha desktop effects EndSection Section "DRI" Mode 0666 # helps flash performance EndSection
There's also an edit on the link about overriding gpu checks. I think that this may help a bit, but it could just be my imagination :), not sure.
Update: For KDE 4 users as of 08-10-2009 QT's glib support can cause some hang on videos. Either put in your ~/.bashrc or run this before you start you browser should be able to help flash performance: