Variable pixel depth and format for video windows

摘要

A computer video controller, particularly a VGA or SVGA video controller for use with graphical user interface (GUI) software such as WINDOWS TM or OS/2 TM is provided with two video data pipelines for simultaneously displaying full motion video within a window in a video display. A first data pipeline displays background video at a first pixel depth. A second data pipeline is provided to display a motion video window at a second, usually higher, pixel depth. The location of the motion video window is measured horizontally in number of memory fetch cycles needed to retrieve the horizontal scan line of pixel data abutting the motion video window. The width of the motion video window is measured in the number of memory fetches required to retrieve one scan line of the motion video window. By providing two parallel data pipelines having equal delays, the motion video window can be generated by selectively retrieving background pixel data or motion video window pixel data and transferring the data to the appropriate pipeline. In an alternative embodiment, data tags may be used to distinguished between background and motion video window pixel data. The controller may also support various compression formats for motion video.