Abstract: A bus snooping multimedia subsystem for implementing video multicast transactions. A multimedia data source such as a video input digitizer is coupled to an expansion bus of a computer system. A plurality of multimedia destination subsystems are further coupled to the expansion bus, such as a video accelerator card and a video compression device, among others. At least one of the destination subsystems is configured to implement a snooping mode of operation wherein transactions effectuated upon the expansion bus are monitored. The snooping destination subsystem may include a programmable storage unit to allow the device to be programmed with specified addresses (or address ranges). The programmed address information associated with the storage unit may correspond to addresses mapped to another destination subsystem in the computer system.

Abstract: A video adapter and computer/video system generate a video output signal having a first format useable by other video equipment. This signal is then looped back through the video adapter to generate a signal in a second format suitable for previewing on a monitor or display. The video adapter includes at least first and second data rate changers (preferably FIFOs), a controller unit, and circuitry for scaling and color-space converting the computer-processed video into the second format. Externally provided video input is multiplexed to a rate-increasing FIFO whose output is coupled to an IOSIMM unit in the computer/video system for video processing, through a master rate-decreasing FIFO whose output is output-controlled, format-processed and provided as the first format output signal. The output-controlled signal is coupled to a scaler, color-space converter and passed to a master rate-increasing FIFO.