Cable television companies and their equipment suppliers are on the verge of installing new technology that will pack many more channels into cable networks, creating a potential programming revolution with implications for broadcasters, telephone companies and the consumer electronics industry.
Some cable programmers are getting ready to take advantage of the technique, known as digital compression.
Home Box Office began market tests last year in which it is offering three programs at once. Currently, this requires transmission on three separate channels, but with compression, all three programs could be transmitted in the future over a single channel.
MTV, the music video channel, has also announced that it will offer three separate programs, specializing in different types of music, starting next year.
Digital compression, which will be introduced gradually over the next three years, uses computer techniques to squeeze three to 10 programs into a single channel. Tele-Communications Inc. of Denver, the nation's largest operator of cable systems, said it planned to start using the technique next year or the year after, and other cable systems are expected to start at about the same time.
A cable system fully using digital compression technology would be able to offer well over 100 channels, compared with about 35 for the average cable television system now. Combined with increased use of optical fibers, it might be possible to offer as many as 300 channels.
"This is a whole new landscape being opened up in the video entertainment industry," said Harold Krisbergh, president of /^ Jerrold Communications, a division of General Instrument Corp., and a leading supplier of cable equipment.
Industry executives say the increase in the number of available channels could allow more specialized programming, such as in foreign languages. The change will also enable cable systems to give consumers the ability to order specific movies, letting cable services compete with the local video store.
And adding more channels might also enable cable television to erode the broadcasters' share of the audience even further, though broadcast executives say they see few competitive implications in the trend toward additional cable niches.
The move toward digital compression does raise a question: How many choices do viewers really need? Some experts think there could be a shortage of good programming to fill all the channels and that cable systems will just offer more movies.
And the multiplicity of channels could pose problems for cable networks and programming services, which are already being hurt by the splintering of audiences.
"Technology is making channel capacity ubiquitous and low cost," said Craig Tanner, vice president for advanced television projects at Cable Television Laboratories, an industry research consortium in Boulder, Colo.
"It is good for the consumer, but it is a challenge for the industry," he said.
As important as the increase in channels, experts say, is that the new transmission will be digital, meaning the channels will use a computer-like code of 1s and 0s rather than analog electromagnetic waves.
Digital transmission promises to provide pictures free of static and distortions, much as digital compact disks reproduce music without hisses and pops.
Digital technology will also make it easier for programmers to encrypt programs, making it more difficult for viewers to see premium services without paying. Moreover, digital transmission will allow cables to be used for sending computer data and software, opening up new business opportunities as computers and television merge.
Schoolchildren might use a computerized video encyclopedia in which an article about symphonies would contain a video clip of an actual performance.
Such video programs are now available on special compact disks that attach to personal computers, but in the future they could be transmitted through television cables. Apple Computer Inc. recently said it would develop consumer electronics products to work with digital cable television.
The technology might also pave the way for "interactive" programs in which viewers of a football game, for instance, might be able to select from among a variety of camera angles on any given play.
One major impact of having more channels will be that cable systems will be able to offer something close to video-on-demand, in which viewers request specific programs that are then transmitted over cable.
Multiple channels would allow cable television companies to steal the thunder of telephone companies, which are gradually installing high-capacity optical fibers to replace the copper wire used in the phone system.
Phone companies, which have been counting on offering movies and television programs to help pay for the costs of providing fibers to homes, have argued that they alone can deliver video on demand because the phone system dedicates a private channel to each customer.
But cable executives challenge this view.