A video data processing apparatus converts one of NTSC type and VGA type video signals to the other or overlays the two types of video signals and outputs them as either an NTSC type overlaid video signal or a VGA type overlaid video signal. The processing apparatus has two video memories for storing...http://www.google.co.uk/patents/US5327156?utm_source=gb-gplus-sharePatent US5327156 - Apparatus for processing signals representative of a computer graphics image and a real image including storing processed signals back into internal memory
