03/24/97 WEBTV'S BEHIND-THE-SCREEN BREAKTHROUGH

Return to main story

WEBTV'S BEHIND-THE-SCREEN BREAKTHROUGH

In the 1980s, Steve Perlman spent months at Apple Computer Inc. grappling with one vexing problem: how to build low-cost Macintosh monitors that wouldn't flicker. It was a grind, but there were some amusing moments. When research showed that young women were especially sensitive to flicker, the twentysomething Perlman had to recruit quite a few to work with him as test subjects in a darkened lab. ''I got a lot of 'Yeah, I've heard that one before,''' he says.
But the long hours paid off. Macs came to set the standard for affordable, high-quality display technology. And Perlman's experience paved the way for WebTV. Indeed, most of the company's pending patents describe ways to make Web pages look good on TV screens.
That's not as simple as it may sound. The fact is, TVs were never meant to display crisp pictures with sharp edges, let alone text. Unlike pricey computer monitors, which were developed for close-up viewing, TVs were designed to be watched from across a room.
''T'' FOR TROUBLE. The key components in TVs and monitors are identical. Both rely on electron ''guns'' in the picture tube that draw images by scanning streams of electrons in horizontal lines across a glass plate. The beam causes tiny dots on the glass to fluoresce in different colors. But there the similarity ends. TVs ''refresh'' the screen image at a leisurely 30 frames per second. Viewed up close, that's not fast enough, so the picture appears fuzzy. Computer monitors redraw the picture at least twice as fast.
Another big problem with TVs is color distortion. When color TVs were developed in the 1950s, they had to be compatible with old black-and-white sets. So engineers figured out a low-cost way to cram color signals into the same black-and-white signals. But there was a trade-off: Coded instructions that determine color and brightness (which computer monitors handle separately) sometimes interfere with each other, causing ''crosstalk''--a sudden, jarring rainbow of colors on the screen.
Perlman's solution is a software filter called TVLens that dissects each visual element on a Web page and subtly alters any component that can cause flicker or crosstalk. The thin horizontal line on the letter ''T,'' for example, is a real trouble-maker. Because TVs alternately scan odd and even horizontal lines in rapid succession, the top of the ''T'' often flickers in and out of view. TVLens displays the ''T'' slightly differently on alternating lines, so that it remains visible.
Similarly, the letters ''M'' and ''W'' cause the TV to send brightness and color signals simultaneously, resulting in the dreaded rainbow. To avoid such color crosstalk, TVLens redraws these letters to soften the sharp edges.
Improving overall resolution is more difficult, since the number of horizontal scanning lines is fixed by national standards. Perlman solved the problem by applying noise-cancellation tricks similar to what NASA uses when it cleans up satellite images of earth. Without actually adding new picture elements, or ''pixels,'' it increases the contrast in the image.
WebTV isn't the only company beaming Web pages onto TV sets. Apple's Pippin game machine and Sega Enterprises Ltd.'s NetLink, for example, offer low-cost Web-browsing on a TV. ''Everyone uses similar tricks to clean up the screen,'' says Kevin Deierling, program manager for 8X8 Inc. in Santa Clara, Calif. His company sells a settop box that turns a TV into a videophone. Soon, it will add a Web browser that promises WebTV-style image enhancement.
The difference is, WebTV arrived ahead of the competition and won glowing reviews on the quality of its images. That's an important first step. In the case of Internet TV, a crisp picture could be worth a lot more than a thousand words.
By Neil Gross in New York

Return to main story