From the nvidia docs: --------- The Composite extension also causes problems with other driver components: o In X servers prior to X.Org 7.1, Xv cannot draw into pixmaps that have been redirected offscreen and will draw directly onto the screen instead. For some programs you can work around this issue by using an alternative video driver. For example, "mplayer -vo x11" will work correctly, as will "xine -V xshm". If you must use Xv with an older server, you can also disable the compositing manager and re-enable it when you are finished. On X.Org 7.1 and higher, the driver will properly redirect video into offscreen pixmaps. Note that the Xv adaptors will ignore the sync-to-vblank option when drawing into a redirected window. o Workstation overlays, stereo visuals, and the unified back buffer (UBB) are incompatible with Composite. These features will be automatically disabled when Composite is detected. o The Composite extension is currently incompatible with Xinerama, due to limitations in the X.Org X server. Composite will be automatically disabled when Xinerama is enabled. ------- The current stable branch version of xorg-x11 is 7.4 And i've been having some serious issues when composite is turned on. with moving objects tearing/flickering on-screen. turning composite off with my xorg.conf resloves the issues. This leads me to believe something somewhere in some package is outdated, unfortunately i'm rather new to all this so i only have a vague idea what it could be.. I'm using KDE. i have not tried another environment. And i believe this can be reproduced by installing gentoo on a computer with a recent nvidia graphics card (i'm using a GTX 670, so something similar), and install x11, kde and the nvidia closed source drivers. then for example watch a video, (I used mplayer2 personally, and tried the example options in that) you might also be able to see it just by scrolling through the desktop widgets that are installed with kde if you look close enough.
I found out an option that was wrong. By default compositing type (Settable in desktop effects - advanced from system settings) is set to XRender, changing that to opengl fixed the issue.
