Originally Posted by Plagman
Using VDPAU under a composited environment is documented to not be guaranteed tear-free. See appendix H of the README, VdpPresentationQueue section.
The original reported also mentioned that the OpenGL output path was tearing. Do other OpenGL applications running under GNOME 3 also exhibit the same behavior, even when forcing VSync?
mplayer -vo gl also exhibits the static tear line, as does mplayer -vo xv. SO do totem and vlc with default output. With other openGL apps it might be hard to tell, since gnome 3.2 has heuristics detecting games and unredirecting fullscreen windows. And full screen is needed, since in my case the tear line is 1 cm below the top edge of the screen, so it is invisible otherwise.