Digital TV is the big picture all set to enter our
living rooms soon. With its wide, huge screen, stunningly bright and crystal clear images,
and crisp 3D surround sound, it promises to make watching TV a cinematic experience.
Looking back progressively, everyday lives
of people have witnessed dramatic changes-from radio age to B/W TV and now to color TV.
Digital TV is the next fundamental change since the introduction of color TV. It would
bring together TV, computer, and communication technology, and with its near total
penetration in homes it would even rival the impact PC has made on the life of common man.
And it is coming sooner than expected. On
April 3, 1997 Federal Communications Commission in the US issued two historic orders. One,
allocating second digital TV channel to each of the nations’ analog television
broadcasters with a mandate to start transmission of at least one digital channel within
24 months. Second, within a transition period of nine years, by the year 2006, all
transmission will have to be digital and the frequency spectrum for current analog NTSC
channels will be taken back entirely by the Government for other land mobile applications.
Why Digital TV
In the present era of analog TV, the entire process of content capture, creation,
processing, storage, broadcast, reception, and display is done in the analog domain. Onset
of Digital TV will shift the entire process to the digital domain. The digital format
provides a number of fundamental benefits. Unlike analog video, digital video can be
manipulated easily. It also can be compressed, providing significant storage and
transmission efficiencies and can be transmitted and reproduced without perceptible image
degradation. Digital formats also provide users with benefits of random access and
superior editing capabilities. More importantly, it permits mixing data with video opening
Consumers would find Digital TV appealing
in several ways. It has approximately twice the vertical and horizontal resolution
compared to existing TVs. The digital transmission will make ghosts and other annoying
picture artifacts disappear. The combination of wide screen, sharp resolution, and clear
transmission will make natural viewing experience a reality. On the audio front, besides
the theater quality 3D sound, it will also offer freedom to mix and match one of the
several audio channels, may be in different languages, for the same picture.
Most significantly, digital technology will
upgrade TV from a receiver of signals to a more sophisticated two-way interactive device.
This would give the viewers capability for online programming of schedules/customized
programming and interactive download of movies, games, data, and programs of their choice.
Electronic shopping would be another offshoot of this interactive capability. With the
mixing of video with data, Digital TV would also be a powerful communication device
offering Internet access, email, and other online services.
The TV should impress broadcasters too. As
it will take smaller frequency spectrum for broadcasts, resulting in cost optimization and
new channels. Digital TV will also open opportunities for additional revenues for
broadcasters by making subscription and pay-per-use revenue possible. They can also be a
part of the distribution channel in electronic shopping and thereby possibly add up
A Walk Through The Standards
Digital TV is a market that has much at stake for the consumer electronics, computer,
broadcasting, and movie industry. With each of them competing for a share of the market
pie, standards are settling amidst intense cross-industry lobbying and negotiations.
In the field of video, a Grand Alliance comprising AT&T, Philips, Thomson, Zenith, GI,
David Sarnoff Research Center, and MIT was formed in 1993 to define a unified systems
approach. Its proposals were largely adopted by Advanced Television Systems Committee
(ATSC). It provides for 18 different video formats (Table-1) which cater to the Standard
Definition TV (SDTV) as well as the High Definition TV (HDTV). It was accepted as a
guideline by the United States Federal Communications Commission (FCC) in December 1996.
MPEG-2 is the video compression standard.
|The Video Formats|
|Aspect Ratio||16:9||16:9||(16:9, 4:3)||4:3|
|Picture Rate||(60I, 30P, 24P)||(60P, 30P, 24P),||(60P, 60I, 30P, 24P)||(60P, 60I, 30P, 24P),|
In June 1997, Intel,
Microsoft, and Compaq formed another group called the Digital TV Team to fight for
dropping of the interlaced scan due to its non-friendliness to computers and also to
eliminate the HDTV resolutions to bring the problem within scope of PC computing power.
However, the dust seems to be settling with the recent announcement of Intel in December
1997, to toe the line of ATSC to receive all 18 formats.
The Audio standards differ between the US and Europe. While Dolby AC-3 six channel
surround sound has been adopted in the US, Europe has settled on the six channel MPEG-2
To address the needs of a new generation of interactive applications, ATSC has formed a
group in November 1997 called Digital TV Applications Software Environment (DASE) to look
into Application Programming Interface (API). Microsoft Windows CE API and Oracle Corp.’s
Network Computer API are jostling with each other to become a part of the ATSC standard.
European Broadcast Union (EBU) has set
itself a deadline of March 1998 to devise a solution for API. It is considering three
different proposals. They are: OpenTV from Sun and Thomson Multimedia, Multimedia Highway
from Canal Plus of France, and MHEG-5-plus-Java from Digital Audio Video Industries
MPEG-2 Transport Stream is the default standard for transmission of multiple video and
audio channels. However, definition for datacasting and Internet support are still in an
infant stage. An industry-wide ‘Open Digital Broadcast Initiative’ is in the offing which
would develop ‘video-plus data’ bit-stream specification and HTML extensions.
Medium For Digital TV Broadcast
Digital TV transmissions are being labeled as ‘bit showers’ that would be falling over the
households. Various digital transmission mediums that would carry these bit showers are
- TERRESTRIAL BROADCAST:
Terrestrial broadcast is the oldest and the most successful way to transmit analog video
and audio. The massive effort put in by major broadcast companies to broadcast digital
signal by the end of 1998 has hastened the movement of all other mediums also to the
- MULTICHANNEL MULTIPOINT DISTRIBUTION
SERVICE (MMDS): MMDS, more commonly referred to as wireless cable, is a
relatively new method for distributing video programming. The service relies on Super High
Frequency (SHF) to transmit through air instead of through overhead or underground wires,
requiring a small receiving antenna to be placed in each home. It is initially being
deployed in areas where there is no cable system or as an alternative to existing cable
services in high-density urban centers.
- LOCAL MULTICHANNEL DISTRIBUTION
SERVICES: Local Multichannel Distribution Service (LMDS) systems operate like a
cellular phone. Transmission takes place at about 30 GHz. At this frequency, the waves do
not travel far. An LMDS transmitter has to set up numerous small cells to cover the
receiving area. This is an advantage as the same channel can be reused in different cells.
This allows the broadcaster to map their transmission to the demographics of the coverage
area. It also offers an excellent opportunity for high-speed Internet access.
- DIRECT BROADCAST SATELLITE
RECEIVERS: By combining digital-video compression technology with high-power
KU-band satellites, DBS systems have the potential to broadcast over 150 channels directly
to an 18-inch dish antenna. The increased channel capacity could be used for new services
such as near-video-on-demand, movie delivery, pay-per-view, and programming directed to
specific segments of the viewing population.
- CABLE SETTOP DECODERS: Most
coaxial cable systems currently have the capability to distribute 40 to 60 analog
channels. By converting to compressed digital video, cable systems have the potential to
deliver additional services by initially expanding to more than 500 channels.
- TELEPHONE DISTRIBUTION SYSTEMS:
A number of new systems are in development and are expected to allow telephone companies
to deliver new services, including digital video to the home. These include a
sophisticated modulation technology, which provides video over twisted pair copper phone
lines (ADSL), Fiber To The Curb (FTTC), and Hybrid Fiber Coax (HFC) networks.
Current State Of Affairs
In line with the FCC time line, a few of the major broadcasters in the US have already
started test runs of digital transmissions and by November 1998, 24 percent of the
consumers are expected to start receiving at least one digital channel. By December 1999,
the coverage is expected to go up to 50 percent.
Similarly, test runs of digital
transmission are reported to have begun in Europe, Australia, and China. In the cable TV
domain, conversion to digital will happen in 1998. Thomson, a member of the Grand Alliance
has successfully teamed up with Hughes, a subsidiary of General Motors, to launch
‘DirectTV’ through the Direct Broadcast Satellite using a proprietary digital format.
Set-top-boxes are being used to convert these digital signals for viewing on the present
The first generation of wide screen digital
HDTV receivers were premiered recently by Zenith and Sharp at in the Consumer Electronics
Show in Las Vegas. Others are likely to follow suit. Interactive features and data
support, however, would not find place in these sets.
The first generation Digital TV receivers
are going to be expensive to make any significant market impact. Costs are high as
cost-effective VLSI solutions are not available as yet. Currently, Lucent and Mitsubishi
have a seven-piece digital HDTV chipset in the market. A handful of companies including
Philips, Armedia, and TeraLogic are developing the highly-integrated second generation
Digital TV chips that would enable cost-effective digital receivers to reach the market in
volume in the year 1999.
Philips solution is based on its revised
Trimedia multimedia processor TM-2. Armedia is leveraging its high-performance studio
quality MPEG-2 422 Profile Video Decoder Technology to leapfrog into the Digital TV
solution. TeraLogic, started by former LSI Logic employees, is focused solely on the
development of Digital TV silicon.
Forms Of Digital TV Receivers
To address the different consumer segments, Digital TV receivers will come in various
forms. Most common of these would be an inexpensive set-top-box converter that would
receive all the 18 ATSC video formats and convert them to a format suitable for the
front-end TV display including the existing NTSC/PAL receivers.
The display units could be of any size or
aspect ratio. Second form would be a wide-screen digital receiver with aspect ratio of
16:9 used for the HDTV. It would integrate the tuner functionality within the display
unit. PC/TV would be another form that would receive all the digital video formats and
display it on the PC monitor with the display resolution remaining limited to standard
Consumer electronics world, where longevity
of the equipment is the norm, would probably make the first two forms more popular with a
large segment which is not computer savvy and also wary of the annual rate of obsolescence
exhibited by the PC market.
Digital TV is possibly one of the biggest markets opening up in the coming millennium. By
the year 2006, when FCC has mandated complete transition to the digital format, in the US
alone 38 million viewers could be tuning to Digital TV, with 16 million of them on
dedicated HDTV sets, according to a consumer electronics study by Multimedia Research
Another study by Instat has made a forecast
of 1.4 million units worldwide in 1998, which would go up to a cumulative figure of 33
million units by the year 2001. More than half of these are predicted to be HDTV sets with
wide screen and a built-in tuner. Yet, this would roughly be only about 7 percent of the
total installation of color TV units worldwide. Clearly, the trend is upbeat and the
entire cross-section of the consumer-broadcasting, movie, and computer industry-is waiting
for the big thing to happen.
Pixels In The Big Picture
Closely watching the fast moving picture about Digital TV, one realizes that this picture
is digital too. The pixels making it include excitement, hope, surprise, belief, pleasure,
innovation, hard work, success, failure, money, market, deadlines, haste, fights, greed,
lobbying, jostling, future, history, control, bits, showers….
No wonder then that Digital TV is slated as
a blockbuster in the making.
RAJENDRA K KHARE,
GM, Armedia Labs.