Digital television: warp speed on a rocky road.

American television broadcasters currently use a six megahertz frequency, allocated to them by the FCC, which allows them to transmit a single analog television channel in the standard NTSC format. This channel is displayed on a TV set through a process called interlaced scanning, which presents half of the total 525 lines that make up a single screen at a time. Screen and visual persistence result in the appearance of a full picture.

The DTV standard approved by the FCC in November 1996 (actually one standard with 18 possible variations) differs in three ways from the existing TV technology:

* First, the picture is transmitted in a digital rather than an analog format.

* Second, in their six megahertz frequency allocation broadcasters have a choice of providing either a single high-quality High Definition TV (HDTV) channel or five or six Standard Definition TV (SDTV) channels. (The latter give viewers a picture quality equivalent to that of the current NTSC standard.)

* Third, the number of lines traced on a TV screen can vary from 480 to 1080 and use either interlaced scanning or the single-step progressive scanning technique employed by computer manufacturers.

This DTV standard provides for 18 different video scanning alternatives, a representative set of which is shown in the chart below.

Warp Speed 

During the nine-and-a-half year journey of consensus that it took for the new DTV standard to be reached, the FCC proposed that the standard be phased in over a 15-year period. Now the FCC has agreed with broadcasters to adopt a much more aggressive strategy, one that will be completed in less than a decade from the adoption of the standard and eight years from when manufacturers estimate they will have the first DTV standard-compliant TV sets available for sale.

The transition plan focuses initially on network affiliates and on the 10 largest metropolitan areas in the U.S.: Atlanta, Boston, Chicago, Dallas-Fort Worth, Detroit, Los Angeles, New York, Philadelphia, San Francisco and Washington, D.C. During this period stations will maintain their current frequency allocation but will also be assigned a separate six megahertz frequency slot for digital broadcasting.

The plan specifies that within 24 months (by May 1999), all network affiliates in these areas must begin broadcasting in digital format. The focus will then be expanded geographically: within 30 months (by November 1999), the network affiliates in the 30 largest cities must start digital broadcasting. This requirement will be expanded to include all commercial stations by May 2002 and all stations by May 2003. In 2006, the FCC will reclaim the current analog frequency allocations, and DTV will be "the standard of the land."

During the transition period, a station may broadcast both analog and digital programming, provided that 50 percent of its analog video programming is on digital by April 2003, that 75 percent is on digital by April 2004 and that 100 percent is on digital by April 2005.

Of course, things may move more slowly than is anticipated today. The original 15-year plan may be more realistic, turning 2006 into 2011.

Business Advantage

Broadcasters will have to make substantial investments of time and money to convert today's programming to a HDTV format. While this conversion will substantially increase the quality of the video and audio presented to viewers, it will not significantly change the nature of the services provided or the traditional business equation of advertiser financing.

However, the DTV standard will give broadcasters the ability to provide new and innovative services to viewers via SDTV channels. Concepts such as the simultaneous broadcasting of regular programming, time-shifted programming and continuous special interest programming will now be practicable. Thus the 7 p.m. network news on SDTV channel 2A could be rebroadcast at 7:30 p.m. on SDTV channel 2B without disturbing regular programming on 2A while weather, traffic and financial reports were concurrently broadcast on SDTV channels 2C through 2E. Such programming could be the basis for additional advertising revenue.

The additional SDTV channels could also support interactive services such as shopping, banking, games or even Internet surfing. These types of services could be either broadband or narrowband and would require special security protocols (and, to carry the viewer interaction, telephone lines). Similarly, subscription services such as digital audio or a limited version of pay-per-view (the "Movie of the Night") could be offered.

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However, interactive services based on either HDTV or SDTV will require an additional DTV-ready set-top device.

There appears to be a consensus that primetime programming will use the HDTV format. This raises the question of when exactly the chance to capitalize on the features of SDTV will occur. Many hypothesize that we will live in a two-tier TV culture in which daytime programming is dominated by SDTV and programming switches to HDTV format at some convenient evening hour. But what of the Saturday morning cartoons?! It appears that we will either have many more of them or that our children's favorite superheroes will be most elegantly portrayed.

Implementation

The rollout of DTV will require a great deal of new equipment. There are approximately 1,600 TV stations in the U.S., each of which will require new transmitting, testing and monitoring equipment. Existing transmitting towers will also require modification.

Studios may actually present a bigger problem. Not only will each existing studio require updated cameras, recorders and signal processing equipment, but they will almost certainly require substantial physical redesign. Because of the ability of HDTV systems to accurately reflect what they see, set design techniques based on imitation brick and stone will no longer be adequate; the real thing may be required. The "all-seeing eye" of the HDTV camera will also pick up warts, wrinkles and other facial imperfections; thus TV makeup techniques will also need to be upgraded.

The design and manufacture of the equipment and processes necessary to implement DTV nationwide require only time and investment. However, the force of technicians and other professionals needed to install, maintain and operate the new digital infrastructure does not exist today. This problem is further compounded by the fact that broadcasters will have to operate digital and analog facilities simultaneously This means that current technicians cannot just be retrained; instead, the current skill pool must be augmented.

Customer Readiness

What of the viewer? Virtually every household in the United States has at least one TV set, and many have three or more. This amounts to more than 200 million TV sets that, according to the current FCC transition schedule, will be obsolete by the year 2006. If the average DTV set costs $500, this will be a huge financial prize for the consumer electronics industry. Since current prices for DTV sets run in the neighborhood of $2000, the real question is: Can a $500 price be achieved? In addition, can the industry manufacture more 25 million sets per year for eight years? Because that's the output that will be required - and that figure doesn't even allow for the increased desirability of the new technology or for a growing population.

There are other pieces of consumer electronics equipment that commonly interface with the TV set. VCRs are almost as prevalent as TVs. Currently available VCRs are designed for today's NTSC standard and therefore must also be replaced in the transition to the digital millennium. Many of the current home video cameras depend on TVs for playback and thus will also require replacement or modification.

The viewer is not the only customer. Because of the federally mandated "must carry" rule, cable TV companies are also customers of the broadcasters. Cable has a 60 percent household penetration rate in the United States. Each cable household has a set-top box, which provides, among other things, frequency conversion of current NTSC signals. It is probable that a DTV-capable set-top device will have to cope with both HDTV and multiple SDTV channels. Although no such set-top devices are available yet, it is highly probable that they too will be significantly more expensive than their analog predecessors.

Many cable companies also offer to provide their customers with access to "digital TV via cable." Although the names are similar, the technical characteristics of this form of digital TV are extremely different from those of DTV. Furthermore, the transmission formats used by the two services are so different as to render the technologies incompatible. The transition to DTV will clearly render obsolete the set-top boxes currently used to provide "digital TV via cable."At present, the impact of DTV on the cable industry has not been evaluated, but the feeling is that it will turn out to be major.

Dr. Joseph G. Schatz is vp of Telecommunications Engineering Services at Logica, Inc.