Aspect ratio control for picture overlays

摘要

PCT No. PCT/US91/03816 Sec. 371 Date Oct. 26, 1992 Sec. 102(e) Date Oct. 26, 1992 PCT Filed May 30, 1991.A picture overlay system assures proper image aspect ratios for picture overlays. The system comprises a video memory and a control circuit for writing and reading information from a video signal into and out of the video memory, the information relating to video data. A reading circuit supplies information from the video memory synchronously with a display for another video signal. An interpolator selectively compresses and expands the information read from the reading circuit, independently of any other processing which might vertically compress or expand said video data. A multiplexer combines the video signals for simultaneous display. The reading circuit can comprise an asynchronous line memory for the information read from the video memory, having a write port operable synchronously with the reading of the video memory and a read port operable synchronously with the display for the other video signal.