How to copy a video tape (page 2)

A video signal has high frequency pulses that line up the signal with the VCR that's recording it and/or the monitor that's displaying it. Keeping your pulses (known as vertical sync pulses) pure will greatly reduce generation loss. That's the job of the TBC, or time base corrector.

Time-base correctors (TBCs) eliminate pulse error, which is created by most video gear. Imperfections in the machinery can cause pulses to time too soon or too late, throwing off the processing of the signal.

Duplicate this error a few generations and you'll have jagged edges, liquidy-wavy images and rolling bars in your video. Keeping your equipment fine-tuned helps, but a time-base corrector is the only way to eliminate the problem completely.

Cabling is to video what strings are to a guitar. The cheaper they are, the more noise you will suffer.

Never--and I mean never--use RF cables to copy your video signal. Sure, they're cheap, but they also cram the audio and video signal through a maze of circuits. Composite cables (usually with RCA or BNC connectors) are better, and S-video cables are best for most consumer-level gear.

Most of these cables come in short lengths. This is good, because long cable lengths can increase the noise in your signal (and therefore compound the effects of generation loss).

If you're using a digital camcorder, you might have access to that wonder of modern technology, the IEEE 1394 FireWire serial data cable. If you have a DV camcorder with an IEEE 1394 DV in/out jack, and you have another camcorder, VCR or DV capture board that also has an IEEE 1394 jack, you can make a purely digital connection using a FireWire cable. This means you can make dubs that are completely free of generation loss. That's right; go ahead and dub ten, fifteen, even twenty generations with FireWire; the copy will look exactly like the original.

It's a good idea to limit the number of video effects devices you use in your productions. Processors, mixers, and titlers all have their magic--and all require that the video signal travel that extra set of circuitry.

Try and cut down the number of devices you run your video signal through. If you need to add titles to a specific part of the tape, run the video through the titler only at that point instead of running the entire tape signal through until you reach that point.

Some videographers bemoan nonlinear digital video editing; others can't stop praising it. How about being able to go to that piece of captured and digitized tape in an instant? Or how about re-cutting a few select portions of a program without shuttling through all those tapes to re-edit?

Though it does have many advantages, nonlinear editing does not completely eliminate generation loss problems. When you pass your signals through the video capture card's circuitry, you'll get added noise, just as you would when using any other type of circuitry. Also, though it isn't technically correct to call it generation loss, digitized video suffers from its own special kind of loss that results from compressing the video data down to a usable size. In general, the more you compress the video, the worse the image looks.

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