Genlock

Genlock (generator locking) is a common technique where the video output of one source, or a specific reference signal from a signal generator, is used to synchronize other television picture sources together. The aim in video applications is to ensure the coincidence of signals in time at a combining or switching point. When video instruments are synchronized in this way, they are said to be generator locked, or genlocked.

Possible problems

Phase differences

Video signals generated and output by generator-locked instruments are said to be syntonized. Syntonized video signals will be precisely frequency locked but because of delays caused by the unequal transmission path lengths the synchronized signals will exhibit differing phases at various points in the television system. Modern video equipment such as production switchers that have multiple video inputs will often include a variable delay on each input to compensate for the phase differences and time all the input signals to precise phase coincidence.