Toob: Digital TV: Two Roads

by Matthew York
Summer 1998

The FCC has set a new television broadcasting standard that will eventually make all current television sets obsolete. Our national TV standard is currently NTSC. The new television standard: Digital Television (DTV).

You may have heard of high definition television (HDTV), a TV signal with greatly improved picture quality. Its resolution is closer to that of cinema, and it is possible for it to display a wider picture. HDTV is a major reason why the government decided to adopt a new TV standard.

HDTV is a complex video signal. Because it contains so much more picture information, the signal has a larger bandwidth. An HDTV signal takes 6 MHz, enough bandwidth for six standard definition signals.

HDTV research has yielded two monumental breakthroughs. First it has provided an anti-interference technology. This can open the so-called taboo TV channels for video traffic: i.e. the channels adjacent to channels in use. The present NTSC system requires every other channel in the TV broadcasting spectrum to remain clear to avoid interfering with adjacent signals. Second, video compression enables broadcasters to squeeze more information into smaller bands of the radio spectrum.

Under the present system, your TV set has only twelve VHF channels, from 2 to 13. Local broadcasters must leave every other channel vacant. Your city therefore has, at most, six VHF TV channels open to traffic. The UHF spectrum is similarly under-used for the same reasons. The digital technologies I just mentioned were developed to squeeze the HDTV signal into a two-channel bandwidth and to broadcast on each successive channel without interference. The net result? Six HDTV channels in the VHF spectrum. Better pictures, not more available channels.

But we don't have to use these technologies exclusively for that purpose. We could instead employ "taboo" channels and squeeze at least six standard definition digital signals into the bandwidth currently allotted for each VHF channel and its adjacent taboo channel. A city could enjoy at least six times as many channels as is now possible. With continued improvement, compression could eventually allow the broadcast of dozens of additional standard definition channels.

The multiplication of channels could open the way for greater diversity of programming. Cable TV proves this, with entire channels devoted to children, news, weather, science, music, education and sports. In addition to traditional TV shows, these channels can be used to transmit data, such as Web pages.

With so many people hungry for so much content and information, and with so many other people authoring it for them, it seems like the wrong time to limit electronic pathways.

The DTV spec approved by the FCC allows for the broadcast of 18 different kinds of digital signals. A given broadcaster could use the same spectrum to broadcast a single, bandwidth-hungry, high definition interlaced signal or any of a number of thinner or lower-resolution signals.

Early in '98 some broadcasters announced they would rather use the spectrum to broadcast six standard definition channels rather than a single high-definition one. They said that upgrading equipment to HDTV specs would be costly, and that the cost could not be passed along to their advertisers. In opening additional channels with new content, they felt they might garner at least some new revenue from new advertisers. Some legislators raised a fuss about this, as they felt this would not honor the wishes of the citizens--or the government--who gave out the spectrum without cost to the broadcasters. At this writing, all the major broadcasters have joined the HDTV bandwagon, agreeing at the very least to broadcast some HDTV to some markets. HDTV does a nice job of opening new channels and filling them with the existing programming. It allows no newcomers, however, and it would be hard to prove that this is really what American TV consumers are demanding. It seems the most active and vocal people involved in this debate over standards all have a direct financial interest in the outcome.

Before the DTV specification was finalized, the computer industry got involved in the debate. Microsoft, Intel and Compaq submitted specs that make provisions for the transmission of "computer data" (i.e. Web pages, entire Web sites, slide shows, text annotations to a TV show/companion content, Java applications and even your morning newspaper). The spec set by the FCC allows for these transmissions too. I am very pleased that another powerful industry has entered the fray in an effort to lobby for diversity.

Consumers, however, aren't nearly as interested in tech specs as they are in what they can receive when they turn on their TV sets. We hope it's both more and better, but for that answer, we'll just have to wait.

Matthew York is Smart TV's editor and publisher