What do you do when sources are seriously out of sync?
Larger Analog Sync Problems and Solutions
Nonsynchronous Sources
TBCs are great for correcting the relatively minor errors found on tape, but some video sources are totally out of sync with the studio. For example, when the networks do a football game, do you think there's a cable going from the sync generator on the ground all the way up to the blimp that's getting those dramatic aerial shots? Of course not! Since there is no incoming sync for the blimp camera, it has to be on its own system, and it is totally out of sync with the cameras on the ground. We say that the blimp is a nonsynchronous or wild video source. Or what about the local TV station? Each station will have its own sync generator, but the video coming into the station from a network or a satellite feed will be on a different sync generator and thus be a nonsynchronous source. If the local station wants to dissolve from the network football game to a local commercial, it could lose sync and the picture will break up.
Frame Synchronizer
The solution to problems posed by nonsynchronous sources is the frame synchronizer. Although the frame synchronizer operates a little differently than a TBC, you can think of it as a TBC with a larger memory. It can hold more than a frame of video information in its memory. Like a TBC, a frame synchronizer converts lines of analog video signal into digital form and stabilizes them. However, the vertical sync rather than the horizontal sync acts as the frame synchronizer gate release signal. When it gets a vertical sync pulse from the house sync generator, the frame synchronizer feeds out a field of video information. As a result, any nonsynchronous video source can be locked up to and integrated with the system you're using. Frame store synchronizers are pretty expensive, but they're a tremendous resource since they will do anything a TBC will do, plus lock up a nonsynchronous source.
1. Since the blimp and the remote truck are operating on separate sync generators, they are nonsynchronous.
2. A TBC feeds out one line at a time, while a frame synchronizer feeds out a field at a time.