Video time division multiplexer with plural dual port memories

Abstract

A video signal is time division multiplexed prior to recording using a time base compression device including a random access memory, instead of serial shift registers or the like. Large time base errors in the incoming video signal are accommodated without creating conflicts between memory read and write operations of successive video lines and without requiring a spare memory. Instead, the time compression random access memory has dual data ports, and successive video lines are loaded into and unloaded out of different locations in the random access memory simultaneously through different ports at different data rates to achieve the requisite time compression. As a result, the usual requirement to route incoming video signals to a spare memory in case of a time base error, for avoiding memory read and write conflicts, is eliminated by the invention.