A TBC Tale (page 5)

A TBC in Your Future?

Though our hero's guardian angel has helped him decide on just the right TBC for his video setup, your own decision may take a little more thought on your part.

First, decide if you can get by with a TBC on a computer card. If your computer is available and you don't mind using a mouse to set colors, you can save a lot of money with a board-based TBC.

If you plan to perform A/B-roll editing, you'll need two TBCs or one of the dual TBCs we mentioned. If you have some equipment with Y/C connectors and some with composite video connectors, a transcoding TBC may be a good investment.

Then comes the hard part. You'll have to decide if the increase in quality warrants the extra cost of a comb filter. Will you really use the special effects available in some TBCs? Do you want to use your TBC to convert tapes to international standards?

These are all questions that you can answer by determining your needs and evaluating the products on the market. Unfortunately, only a few cities have industrial video dealers that will display various TBCs, but some mail order suppliers might let you try one model and trade it in for another.

TBCs are a good investment; consider getting a good one. Unlike VCRs and camcorders, TBCs have no moving parts to wear out. Even though they're digital devices, the technology doesn't change that much from year to year, so you don't have to worry about obsolescence.

One thing is certain: a TBC will certainly improve your image. And that's something every videomaker is interested in.

SIDEBAR: TBCs and Synchronizers in Digital Video Mixers

Videonics incorporates a dual-channel TBC in their MX-1 video mixer. While it doesn't have the sophistication of some of the TBCs discussed here, it does provide frame synchronization so you can mix the output of two VCRs to perform A/B-roll editing.

Other digital video mixers (such as Panasonic's WJ-AVE7, MX-30 and MX-50) have frame synchronizers that allow A/B-roll editing, but do not have a true TBC to correct time base error.

--S.S.

SIDEBAR: VCRs with TBCs

VCR manufacturers include TBCs in some of their editing VCRs so that videomakers can edit and copy their tapes as cleanly as possible. Some high-end S-VHS editing VCRs offer optional plug-in TBC cards. Betacam and other broadcast VCRs have included TBCs for some time. Now, manufacturers of consumer VCRs have started including TBCs with their machines. While these TBCs improve stability and remove jagged edges, they usually do not include a proc amp or a frame synchronizer. You'll need an external TBC if you want to sync two VCRs to work with a non-synchronized switcher, such as a Toaster. Panasonic's consumer-grade PV-S4480 ($1099) includes a simple TBC. Their AG-1970 ($1940) is a semi-pro editing S-VHS VCR with a similar TBC; even their AG-3 camcorder ($3570) comes with a basic TBC. On the Hi8 side, Sony makes the EVS-7000 Hi8 VCR ($1999) that includes a similar basic TBC.

--S.S.

SIDEBAR: The Jargon of TBCs

Comb Filter: An electronic device that reduces video noise by lowering contrast.

Component:
A technique of dividing the video signal into red, blue and green portions of the signal, each having their own input and output connector. Component processing exists on Betacam and MII VCRs.

Composite:
Standard video going in or out of RCA-style connectors is composite. This is slightly lower quality than Y/C or component processing.

Dropout Compensation (DOC):
When normal wear and tear scratches the oxide away from videotape, dropouts (brief, white horizontal streaks across the picture) occur. A DOC replaces that streak with a previous line of video.

Field/frame Freeze:
A field is one half of the video image, displayed in 1/60th of a second. A frame is the full image, displayed every 1/30th of a second. To freeze a picture in motion, you generally use field freeze. Frame freeze is higher quality, but may not be rock solid if there is movement in the image.

Genlock:
The ability of equipment to be synchronized by an external sync generator.

Noise Reduction:
Video noise shows up as grain or dots on the screen. Digital noise reduction (DNR) reduces this.

Proc Amp:
Pronounced "prock amp", this term is short for a processing amplifier that adjusts color and brightness on videotape. Many TBCs have them built in.

Rack Mount:
Some TBCs that are stand-alone units (those not on a card) have tabs on the front plate that allow them to be mounted permanently in a professional rack. Some do not.

Standards Conversion:
The ability to copy tapes between the American television standard (NTSC) and standards in other countries (either PAL or SECAM).

Synchronizer:
Some full-frame or infinite window TBCs have a built-in synchronizer to lock up two or more VCRs for A/B-roll editing.

Transcoding:
A feature in TBCs that allows translation between Y/C video and composite video. More advanced TBCs include component transcoding.

Y/C:
Used with S-VHS and Hi8 VCRs and similar to component processing, Y/C separates the luminance or gray scale portion (Y) of the signal from the chroma or color (C) portion, and uses a special 4-pin cable to keep them separate. Y/C video is also known as "S-video".

--S.S.