System for synchronizing a video signal having a first frame rate to a

Abstract

A synchronizer receives from a tape playback arrangement television frames at a rate which is slightly higher or slightly lower than a standard frame-rate. The synchronizer includes four frames of storage, and reading and writing are continuous. In a mode in which the incoming frame rate is high, the read and write become separated in time as time passes due to the difference in frame rate. When reading and writing are separated by at least two frames, a motion detector is activated to continuously interrogate the memory in order to locate two identical frames. When two frames are identified as being identical, the read address is immediately switched by two fields, thereby bypassing or dropping two fields. This drop is not visible because the motion detector has identified the fields as being substantially identical. When the incoming signal is at a slower frame rate than normal, reading slowly lags writing until a two-frame difference or more occurs, whereupon during the next identical-frame condition, reading is switched closer to the writing point, thereby repeating two identical frames.