Editing X video extension (section)

=== The role of window manager support and compositing ===

Under X, how video is finally drawn depends largely on the [[X window manager]] in use. With properly installed drivers, and [[graphics processing unit|GPU]] hardware such as supported [[Intel]], [[ATI (brand)|ATI]], and [[nVidia]] chip sets, some [[window managers]], called [[compositing window manager]]s, allow windows to be separately processed and then rendered (or composited). This involves all windows being rendered to separate output buffers in memory first, and later combined to form a complete graphical interface. While in (video) memory, individual windows can be transformed separately, and accelerated video may be added at this stage using a texture filter, before the window is composited and drawn. XVideo can also be used to accelerate video playback during the drawing of windows using an OpenGL [[Framebuffer Object]] or pbuffer.

[[Metacity]], an [[X window manager]] uses compositing in this way. The compositing can also make use of 3D pipelines accelerations such as GLX_EXT_texture_from_pixmap. Among other things, this process allows many video outputs to share the same screen without interfering with each other. Other [[compositing window manager]]s such as [[Compiz]] also use compositing.

However, on a system with limited OpenGL acceleration function, specifically the lack of an OpenGL [[Framebuffer Object]] or [[pbuffer]], the use of an OpenGL environment like [[Xgl]] makes xv hardware accelerations impossible.