I analysed this problem further and found out that all videos are played using the Xvideo extension by default (on precise). This is different from lucid, where the Xvideo extension doesn't seem to be available (xvinfo reports that no driver was found). If I force the video player to use the x11 driver (e.g. mplayer -vo x11 ...) I get a better performance (on precise). BTW, the bug seems to exist in Debian as well, because this description is quite similar to what I am experiencing: http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=672972
What I do not understand so far: 1. Why does it help to boot with "nomodeset"? Somehow the kernel modesetting seems to be involved. 2. Should Xvideo be enabled? Because it wasn't on lucid, but it seems that it has been enabled earlier (see http://unix.stackexchange.com/questions/9305/xvideo-extension-not-active-with-the-radeon-driver). Which component is responsible for enabling it? It doesn't seem to be the Xorg radeon driver, because if I use an old version that is similar to the one used in lucid (I compiled 6.13.1 myself), Xvideo is still enabled on precise. I will continue investigating... ** Bug watch added: Debian Bug tracker #672972 http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=672972 -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1075296 Title: nomodeset needed for radeon 7000 To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1075296/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs