Comment 121 for bug 177492

I think it can be safely said that any further slowdowns of video playback while compiz (or perhaps another compositive manager which uses indirect glx) is running, are because of the fact that the video frames are being transferred over aiglx as textures. Unless the kernel supports something like TTM to accelerate this, video playback will continue to stutter. When using a non-compositing window manager (metacity with compositing off), video playback is perfectly fine.

So perhaps this bug depends on support of ttm in the kernel.