Editing Genlock (section)

== Scope ==

Generator locking can be used to synchronize as few as two isolated sources (e.g., a [[television camera]] and a [[videotape]] machine feeding a [[vision mixer]] (production switcher)), or in a wider facility where all the video sources are locked to a single synchronizing pulse generator (e.g., a fast-paced sporting event featuring multiple cameras and recording devices). Generator locking can also be used to ensure that multiple CRT monitors that appear in a movie are flicker-free. Generator locking is also used to synchronize two cameras for [[Stereoscopy|Stereoscopic 3D]] video recording.

In broadcast systems, an analog generator-lock signal usually consists of vertical and horizontal synchronizing pulses together with chrominance phase reference in the form of [[colorburst]]. No picture information is usually carried to avoid disturbing the timing signals, and the name ''reference'', ''[[black and burst]]'', ''color black'', or ''black burst'' is usually given to such a signal. A composite colour video signal inherently carries the same reference signals and can be used as a generator-locking signal, albeit at the risk of being disturbed by out-of-specification picture signals.

Although some high-definition broadcast systems may use a standard-definition reference signal as a generator-locking reference signal, the use of tri-level synchronising pulses directly related to the frame and line rate is increasing within HD systems. A [[tri-level sync]] pulse is a signal that initially goes from 0 volts DC to a negative voltage, then a positive voltage, before returning to zero volts DC again. The voltage excursions are typically 300&nbsp;mV either side of zero volts, and the duration each of the two excursions is the same as a particular number of digital picture samples.