Synchronization of Computer Controlled Video Sources to Video Disc or Tape in Consumer Products

Synchronization of a computer controlled video source such as a video game or personal computer to another video source e.g., video disc or tape player is frequently desirable. The present design clocks the computer controlled video source at some multiple of the horizontal synchronization frequency of the video disc or tape source so as to obtain frequency coherence; further detecting phase incoherence between the signals from the two sources and in response thereto causing the clock pulses to cease for a predetermined period, the computer or game is allowed to "slip" sync and obtain phase coherence also.