Re: Image tearing/image artifacts during video playback
There are two issues when a compositing manager is enabled:
a) The compositing manager must sync its own rendering to VBlank. Most compositing managers render using OpenGL, so the OpenGL sync to VBlank setting will help here.
b) There's an issue in the damage events spec and interaction with GLX_EXT_texture_from_pixmap, such that it's not possible for the compositing manager to atomically pick up rendering to redirected windows. This could cause tearing too, and unfortunately it can't be worked around at present. This may/may-not affect you depending on all manner of system timing issues.