[Jerome Boiteau]

Genlock is an external clock. You need it to stabilize the speed of any VTR (a beta SP or Beta digital for example). The servo for the motor will be clocked to the genlock, ensuring a perfect speed from start to finish. Genlock is also used in live situation to ensure that video switcher are switching on the same video edge as the camera, but that’s another (more complicated) issue.

With non-linear video, genlock is used to stabilize the speed of playback, ensuring you are always playing at the perfect speed. also, when transfering from the Decklink to the Beta, you need to sync the frame edges from the card, with the frame edges the Beta is expecting. this is why you need a genlock. there is a way of telling the Beta to sync to the incoming video signal (that’s the way consumer equipment works), but it is less stable.

It is more complicated that those few lines, but to make a long story short, having each piece of equipement locked to a central clock ensures that those equipement will “talk” at the same speed. there are other ways of doing it, but this one has been proven reliable for a long time.