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                                                                                TECHNOLOGY, Page 54

The Picture Suddenly Gets Clearer


With this week's first broadcast of digital high-definition TV,
the U.S. takes the lead in a pivotal industry for the 21st
century

By PHILIP ELMER-DEWITT


    If all goes according to plan -- a big "if" when it comes
to new technology -- broadcast history will be made in a
meeting room on Capitol Hill this week. A new kind of television
signal will leave the Bethesda, Md., TV tower of WETA, a PBS
affiliate, fly across downtown Washington, strike an antenna on
the roof of the Capitol building and zip down a cable into the
Thomas P. O'Neill Room two floors below. There, before an
audience of Senators, Congressmen and assorted commissioners,
magician Harry Blackstone Jr. will draw back a black cloth and
reveal the first image ever to be broadcast in digital
high-definition television: a razor-sharp picture of a
fluttering American flag.

    The image is well chosen. Just two years ago,
high-definition television (HDTV) was a symbol of everything
that was wrong with the American electronics industry. After
ceding most of the market for today's television sets to
Japanese and European manufacturers, the U.S. was about to lose
the market for tomorrow's TVs as well. It seemed only a matter
of time before U.S. consumers started replacing their squat,
fuzzy receivers with crisp, wide-screen sets built around a
made-in-Japan technology called analog HDTV.

    Now the situation is reversed. With this week's broadcast,
the U.S. will seize the lead in the HDTV race, having
successfully changed the venue of the battle: from the world of
radio- and TV-signal processing, in which the Japanese excel,
to the digital world of computers, which is dominated by U.S.
firms. "The entrepreneurial spirit is alive and well in the
U.S.," says Donald Rumsfeld, former Secretary of Defense and now
chairman of General Instrument, the Chicago-based company that
spearheaded the push to digital HDTV.

    This week's demonstration, staged by General Instrument,
marks a victory for those who have argued that the Japanese
approach to television design is all wrong, a relic of 19th
century technology that dates back to Marconi and Bell. The
future, they say, is digital. To survive in a world dominated
by digital chips, digital telephones and digital compact discs,
the television of the future must speak in the streams of 0s and
1s that are the language of computers.

    Conventional TV uses analog waves as electronic
representations -- or analogues -- of the light and sound waves
captured by television cameras and microphones. The Japanese
approach to HDTV was to double the number of horizontal lines
used to reproduce the images on the screen -- from just over 500
to more than 1,000 -- while continuing to rely on analog
technology to transmit the images.

    Scientists have long known that it is possible to
represent the information carried in analog waves with strings
of numbers. That is essentially what recording engineers did
when they replaced analog records and tapes with digital compact
discs. The advantages are twofold. Digital signals offer many
more opportunities to identify and eliminate distortions caused
by interference -- the echoes, flutters, ghosts and bursts of
noise that can make today's broadcast television so hard on the
eyes. Going digital also makes it easier to isolate and
manipulate images -- freeze frames, enlarge pictures, even view
scenes from different angles. That feature will grow
increasingly important as television and computer technology
begin to merge.

    The main drawback to representing pictures digitally is
that it is enormously inefficient. For all their disadvantages,
analog waves are very good at packing a lot of information into
a compact form. A single HDTV image, easily captured in a tiny
analog wave, represents about a billion bits of digital data --
100 times more than can be squeezed into the narrow channels of
the broadcast spectrum allocated for television by the Federal
Communications Commission. It would take a supercomputer at
every broadcast station and in every TV set, skeptical experts
said, to compress and decompress the data.

    Then in June 1990, two days before the FCC deadline for
proposing standards for the next generation of broadcast
television, General Instrument announced that it had found a way
to solve the compression problem. That sent everybody back to
the drawing board. Today the Advanced Television Test Center,
an industry-sponsored group under contract to the FCC, is
considering four different digital HDTV systems for adoption as
the U.S. standard: two from General Instrument and the
Massachusetts Institute of Technology; one from Zenith and AT&T;
and one from a consortium made up of NBC, the David Sarnoff
Research Center and the two European electronics giants Philips
and Thomson. (Two analog systems submitted by the consortium and
the Japanese broadcast company NHK are no longer considered
serious contenders.)

    How do these systems squeeze 100 channels' worth of visual
information into one? The trick is to streamline and simplify
the data while taking into consideration what can be seen by the
human eye. For example, the eye cannot perceive detail in color
as well as it can in black-and-white, and so all the systems
save data by transmitting color information at lower resolution.
Then, because the vast majority of TV pictures do not change
very much from one frame to the next, the systems can eliminate
huge quantities of data by sending only the differences between
the frames. This process is made more efficient by tracking
objects as they move from frame to frame. Finally, when there
is too much detail changing too fast for the systems to transmit
all the information, the computers simply drop portions of the
data -- a truncation that shows up on the screen as fleeting
patches of fuzziness. "When the going gets tough," says Robert
Rast, a vice president at General Instrument, "the image gets
coarser."

    General Instrument and the Zenith-AT&T team have submitted
working prototypes to the FCC's test center. Although the
results are closely guarded secrets, experts privy to the
deliberations report that while there have been glitches, no
fatal problems have turned up yet in either system -- a fact
that will make choosing between them more difficult. "There
could be some really tough decisions ahead," says Peter Fannon,
executive director of the test center. Fannon is already talking
about the possibility that the FCC will want to mix and match
technologies from several competing systems. The idea of two or
more contenders joining forces is sure to be raised next month,
when the proponents gather in Las Vegas for an HDTV conference
being held in conjunction with the annual meeting of the
National Association of Broadcasters.

    When will digital HDTV appear in homes? The FCC is
scheduled to pick the winning system in June 1993, and the
betting in Washington is that the commission will not miss that
deadline by more than a few months. Once the U.S. standard has
been set, it will probably be a year before what is now a
haphazard collection of off-the-shelf circuit boards -- housed
in racks the size of refrigerators -- is reduced to a handful
of computer chips that can be sold to manufacturers and stuffed
into TV sets. The first commercial receivers could appear on the
market in late 1994, but probably will not be widely available
before 1995. Prices could start anywhere from $3,500 to $5,000,
and will fall slowly until the technology catches on and the
sets begin to sell in the millions.

    How long that will take is anybody's guess. To create a
successful entertainment medium requires not just flashy new
technology but also programs compelling enough to persuade
viewers to trade their old systems for the new. NHK has been
broadcasting analog HDTV signals since 1989, and last November
Japan's networks expanded their offerings from one hour to eight
hours daily. Despite bold predictions that the Japanese would
sell 500,000 HDTV sets a year by 1991 -- and a price cut that
brought the cost of those sets from $30,000 to $7,700 -- few
people are buying or watching. Things could move faster in the
U.S., the home of Hollywood, HBO and Monday Night Football. But
digital HDTV is likely to remain a toy for the adventurous --
or the rich -- until the early years of the 21st century.