Originally Posted by Jotti
My system is a Core2Quad Q9450 at 3.2GHz running Debian AMD64 (testing) with KDE4.2 with compositing enabled, powered by a GTX280. The following may sound a bit incoherent, but I will post my findings for the sake of completeness anyway.
Given you have a compositing manager running, this sounds like a slightly different problem; it could either be a VDPAU issue, PowerMizer issue (like other people), or in your case additionally some issue with the compositing manager path. do you see stutters if you leave the X composite extension turned on, but disable the X composite manager, so that VDPAU (and not the composite manager) is rendering directly to the screen?