The studio described in Chapter 8 employed video sources that were predictable in their timing. Videotape players are not: they are mechanical systems that have irregular timing variations, or time base errors.

All tape machines suffer the effect to some degree and various ways have been developed to correct the condition. All involve electronic correction.

In Figure 9.1 the composite VTR has a genlock input although this need not be complete black and burst as the machine cannot maintain line sync accuracy, and colour phase will be completely disregarded. The machine will maintain lock in frame only, that is 2 V; hence this is called simply ‘framing’. The time base corrector (TBC) shown in Figure 9.1 is very significant ...

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