ST Composite Video!
by Andrew Reese
This was going to be the column in which I explained camera cuts in Cyber Control, but a new product arrived in the START offices that threw that plan in a cocked hat: VideoKey from Practical Solutions. For the first time, all ST and Mega owners can have high-quality composite video output for recording animations--or just playing Starglider II on that 31" TV in the corner.
Practical Solutions has a history of producing excellent, thoughtful products for ST users, products we usually didn't know we needed until Practical Solutions provided them. Monitor Master was their first product and was a godsend to those of us with both color and monochrome monitors. Then came Mouse Master for game players and Drive Master for pc-ditto users. All answered a need, made computer life more convenient and saved plugging and unplugging peripherals. VideoKey, however, is not just a product that makes life more convenient. It is a product we've needed since the first 520 ST was shipped three years ago.
|VideoKey is the latest solution from the folks at Practical Solu-
tions. It's invisible to your ST and provides a high-quality com-
posite video output--just the thing for animators.
I Want My Composite Video!
If you've created any animations on your 520 STFM, 1040 ST or Mega, you've probably complained about Atari's lack of foresight in not building composite video output into their computers. There's been only one solution until now: find someone with an older 520 ST with built-in modulated RF output and enough memory to hold your animation. The only problem was that the 520 ST's modulated RF output was less than high quality. It was designed before there was any animation software for the ST and it was built to a price; its original purpose was to allow 520 ST's to be used with televisions instead of monitors. But it was better than nothing.
VideoKey is the solution for all ST and Mega owners, including 520 ST owners. It's a small, Atari-gray box, four inches by five-and-one-quarter inches by one-and-one-half inches in height with five jacks, one cable, an LED indicator, a slide-switch, a screwdriver adjustment and an external power supply. With VideoKey, you can have your cake and eat it, too--your ST's RGB or monochrome monitor is still available for use with no switching or unplugging. VideoKey is invisible to your system.
Setting up VideoKey is easy. With all the power to your system off, you unplug the monitor cable (or monitor switch cable if you have one) from your computer and plug it into the VideoKey monitor jack. Next you plug the VideoKey's monitor cable into your computer, plug the power cable from VideoKey's external power supply into it and then plug the power supply into an AC outlet. Finally, you connect VideoKey's audio and video signals to your VCR. Use a standard video cable between VideoKey's composite video jack and your VCR's Video In jack and a standard audio cable between VideoKey's Audio jack and your VCR's Audio In jack. You're all connected!
There are only two adjustments on VideoKey: coIor signal synchronization and channel selection for the TV output. Color signal synchronization is done with a small screwdriver adjustment--called Colorloc--on the bottom of the VideoKey. With a color monitor plugged (or switched) into VideoKey, you adjust this control until the LED indicator glows the brightest. When this occurs, VideoKey is synchronized to your system. It's a onetime adjustment and it seemed to work properly on mine.
The channel selection slide switch switches the TV output between channels two and three; if your television or VCR accepts composite video, you won't need this output at all. In addition, the extra circuitry necessary to translate a video signal into a TV channel degrades the quality noticeably.
There's no power switch on the VideoKey. It's constantly supplied with power from its own external power supply, but it doesn't switch itself on unless there's a color monitor plugged (or switched) into it and in use. Then the LED glows and it's operational--truly well-designed.
VideoKey also provides an audio output, rated at the usual one-volt peak-to-peak at an impedance of 1K ohms. I would have to rate the audio output as no more than acceptable; it seemed a bit muted and muddy to me.
It Works, But You Can Help. . .
But does VideoKey work? In one word, yes! Practical Solutions boasts a signal bandwidth of approximately 4 mHz for VideoKey and the output is far above that from my old 520 ST. It's not perfect, mind you; there's still some bleeding and shimmering on reds and intense blues. Practical Solutions discusses this problem in the VideoKey instruction manual and gives tips on minimizing these effects. Their suggestions are reproduced here in their entirety:
"Some colors are more stable than others. Shades of gray are very stable and greens are very good as well. Use blues and reds with care as they tend to bleed when saturated. Reds are especially notorious in any video work. Try not to put opposite colors side-by-side on the same screen--they tend to bleed into each other. The background color can also make a big difference in how your artwork looks on video."
Another problem that arises when piping ST output to video is the difference between the ST's horizontal synch rate and the industry standard. Although the difference between the ST's 15.769 kHz and the standard 15.734 kHz is only approximately 35 Hz, the result is some artifacting and edge distortion, particularly on sharp, vertical edges. (Artifacting is the name for the false colors that sometimes appear along edges.) Practical Solutions offers--what else?-a (fairly) practical solution. They suggest changing the ST's master clock frequency crystal. By slowing down the ST's clock just slightly (less than .2%), the ST's horizontal synch rate will be almost dead on standard. Nothing else will be affected and your ST still won't run as slowly as a Mac. Contact Practical Solutions if you want to make this change to your ST; it requires some technical expertise.
VideoKey won't work well enough with the 19-inch TV in your living room for you to think of using it for 80-column text display, desktop publishing or any difficult medium-resolution task. It's designed for use in low resolution--for games or animation. And if the game has an intensely blue display, like Typhoon Thompson from Broderbund, the TV display is just a bit too muddy to use. And unfortunately, VideoKey day adds one more cable and one more peripheral to the octopus that lurks behind my ST. But if you keep its limitations in mind, VideoKey performs very well and at $119.95, it's a bargain.
Thanks, Practical Solutions.
VideoKey, $119.95. Practical Solutions, 1930 East Grant Road, Tucson, AZ 85179, (602) 884-9612.