Under X, how video is finally drawn depends largely on the X window manager in use. With properly installed drivers, and GPU hardware such as supported Intel, ATI, and nVidia chip sets, some window managers, called compositing window managers, 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.