Slow motion and freeze frames are also possible.

Other Advantages of TBCs and Frame Synchronizers

Dynamic Tracking Heads

TBCs and frame synchronizers can give you a couple of other capabilities as well. If your VTR has a dynamic tracking head, a TBC will allow you to do broadcast-quality slow motion. A dynamic tracking head is a video head that adjusts itself to follow the video track when the tape changes speed. When you slow down the speed of videotape playback, the relationship between the video head and the angle of the video track changes. The dynamic tracking head automatically compensates for this change and always stays centered on the video track. A TBC or frame synchronizer simply maintains the proper sync with the rest of the system, even if, as in this case, the tape speed is slowed.

Freeze Frames

A frame store synchronizer will also let you freeze frames. When you push the freeze on a frame synchronizer, it will continuously feed out the same field of video information. Some units will also feed out a complete frame, but then you often get frame jitter. This is because the video picture is not static. In the camera, after the first field is scanned, the second interlaced field is scanned. But in the meantime, the subject of the picture may have moved just a little. So when the second field is interlaced with the first one, the subject may be offset a little, and this can cause a jitter of the subject between one field and the other.

TBCs, VTRs, and Production

TBCs are what have made helical VTRs practical for broadcast use. TBCs and frame synchronizers have become an integral part of TV production facilities everywhere. They are the devices that started the digital revolution in video production.

Digital technology provides another advantage beyond what might be apparent from this discussion of TBCs and frame synchronizers. Unlike analog, when the digital signal is run through several pieces of equipment, there is no increase in noise. Since digital information is a series of numbers, the D to A converter will ignore any surrounding noise when it converts that number to its corresponding voltage.

1.  Dynamic tracking heads.

2.  Integrating helical VTR video without time base correction.

3.  Integrating helical VTR video with time base correction.