Comment 3 for bug 151674

So far I'm getting much better results by enabling Sync to To VBlank in CCSM. Changing settings in nvida-settings doesn't appear to help things any.

XVideo by default will sync to vblank, which is what you want if you're rendering directly to the display without the use of a composite manager. When a composite manager is in effect there's probably extra steps involved and you're no longer rendering directly to the display. Instead you're rendering the video to a texture in your video hardware and the composite manager takes care of rendering the display with the assistance GPU. If the composite manager isn't syncing the display you're going to have shabby results because the video playing and display painting is no longer in sync.

If you try this also verify CCSM shows the correct Refresh Rate for your display. If it's wrong, disable Detect Refresh Rate and set the Refresh Rate manually. TwinView users (like me) often have the wrong Refresh rate displayed due to the way the nVidia drivers abstract the displays in a TwinView configuration.