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On the horizon are more radical improvements in TV image quality that will come from attacking the problem at its source: the broadcast signal. American television is transmitted as a succession of images, each containing 525 horizontal lines, that follow one another at 30 frames a second. Japan's public broadcasting system, NHK, has developed a new standard called high- definition television, which widens the screen and more than doubles the number of lines, to 1,125. The result is a picture of extraordinary clarity that compares favorably with 35-mm film.
The problem with HDTV is that its signal cannot be squeezed into the narrow space allocated each channel in the TV broadcast spectrum. For the U.S. to ; switch to the new system, every television station would have to replace its equipment, and the country's 140 million TV sets would have to be scrapped, an unlikely prospect at present.
Nonetheless, several U.S. production companies have bought Japanese-made HDTV equipment for shooting movies, commercials and music videos. Reason: videotape is easier and cheaper to edit than film. Crack in the Mirror, a new action movie starring Robby Benson, was shot entirely on HDTV videotape, and will be transferred to 35-mm film for theatrical release early next year. Rebo High-Definition Studio in New York City, which produced the feature, estimates that its costs were 30% lower than if it had shot and edited the movie on film.
Various schemes have been put forth to make HDTV more widely available. One proposal is for cable TV operators to provide the higher-quality images as an added service for their subscribers. Another is to distribute HDTV programming on high-capacity videodisks, much as videotapes are distributed today. A third approach involves splitting the HDTV signal into two parts and transmitting it over two separate broadcast channels. Old TV sets could utilize enough of the signal to provide a standard-quality picture, while an HDTV receiver could display the higher-resolution image.
As U.S. broadcasters ponder what to do, the Japanese are making HDTV available on an experimental basis. Next year they will begin special coverage of the Seoul Olympics, which can be viewed in Japan only on HDTV sets. In 1990 Japan will launch a communications satellite designed to carry HDTV signals, capable of transmitting them anywhere in the world. But experts predict that it could be five years or more before the slow-moving U.S. networks begin to offer HDTV broadcasts of their own.