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What is DTV?
DTV is "digital television." Specifically,
DTV is a revolutionary new form of television that delivers top quality
all-digital audio and video programming to viewers over the air, and via
cable and satellite. DTV uses the new ATSC (Advanced Television Systems
Committee) transmission system standard. DTV encompasses Surround Sound
audio, high definition pictures, standard definition pictures, multicasting
pictures of several programs simultaneously, and data broadcasting. Many
digital TV programs also will incorporate a wider-screen viewing area (known
as the aspect ratio). The current analog aspect ratio is 4:3. The new aspect
ratio for many (but not all) DTV programs will be 16:9, which approximates
the more natural viewing experience of most motion pictures in theaters.
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What is HDTV?
HDTV (High Definition TV) is a DTV format
that offers the highest-quality images and CD-quality Surround Sound audio,
and the 16:9 aspect ratio, with resolution that equals or surpasses 35mm
film commonly viewed in theaters. Therefore, HDTV programming is noticeably
superior to the audio and video currently seen on today's analog sets.
Currently, there are two widely accepted standards for HDTV -- 1080i (interlaced)
and 720p (progressive). Incidentally, The FCC has not specified how much
HDTV programming a TV station must air on its DTV channel. It is likely
that most early HDTV programs will air during evening prime-time hours.
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What is SDTV?
SDTV (Standard Definition TV) is another
DTV format. Since SDTV is transmitted digitally, the images usually are
sharper and clearer than the analog TV we see today. Because the SDTV format
uses less spectrum than HDTV, this format also is used for multicasting
capabilities.
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Will I need to buy a new
TV set to receive DTV programs?
No. Set-top converter boxes will make
it possible to receive DTV (including HDTV) programs on your current analog
TV set. However, you will be viewing this programming in the traditional
analog standard. To get the full benefit of DTV (including digital Surround
Sound), you will need a new DTV-capable TV receiver.
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How is DTV different from
digital broadcast satellite (DBS)?
Broadcast DTV and DBS use digital transmission.
However, DTV uses the ATSC format (which brings you HDTV, multicasting,
datacasting, and other ancillary services). Another key difference is that
terrestrial broadcast DTV will be over-the-air, and is free to all viewers,
whereas DBS is a pay subscription service. Regardless of whether a program
is sent to consumers digitally, such as with many DBS services, consumers
still must purchase a new digital receiver in order to view the program
digitally.
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When will I be able to receive
DTV?
It depends on where you live. Some limited
DTV service in the very largest markets is scheduled to begin in late 1998.
PBS will begin distributing to member stations some HDTV and SDTV programming
starting Nov. 9, 1998. However, public and commercial broadcasters in most
markets intend to begin service between 1999-2001. Consumers will not be
able to receive this initial DTV programming without a new set-top box,
and will only be able to take full advantage of the enhanced digital video
and audio quality and ancillary services when they purchase a new DTV-capable
receiver.
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What is compression?
Compression is a technical way to reduce
the amount of "information" in the TV signal that must be transmitted to
offer a high-quality digital signal. Compression makes the U.S. standard
of digital television feasible, given spectrum limitations in the U.S.
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What is datacasting?
DTV will allow broadcasters to deliver
ancillary digital data in various forms, such as Web site material, and
program and non-program related information, along with the television
signal. This form of data transmission is what we mean by datacasting.
Datacasting does not have to be tied into on-air programming, and can be
used in cooperation with local broadcasters by private businesses, local
government, hospitals, schools, and other entities for the transmission
of all forms of information, including text, pictures, audio, etc.
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What is multicasting?
DTV will allow broadcasters to deliver
more than one SDTV channel at the same time from one station. This multiple
stream of services is called multicasting. Viewers may see this service,
for example, as four program channels coming from one TV station (PBS-1,
PBS-2, PBS-3, PBS-4), and would be able to select the multicast channel
of their choice. Depending on the type of programming and the spectrum
it requires, TV broadcasters may feed 2, 3, 4, or more channels simultaneously.
(The more "information" in a program -- such as a live sports event vs.
panning pictures of the Grand Canyon -- the more spectrum it requires.)
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Where can I see DTV?
DTV receiver demonstrations (and some
early sales of new sets) already have begun in some retail stores in various
parts of the country, but most retailers are expected to roll out their
new receivers (and separate tuners) in time for Christmas 1998. Call your
local consumer electronics retailers for your own market's roll-out plans.
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How much will new DTV sets
cost consumers?
As with any new (or "first generation")
product, initial price tags will be higher than, for example, current NTSC
analog receivers. (It was not too many years ago that a large, bulky cell
phone was priced at around $2,000.) Early indications are that new large-screen
DTV sets may start in the $6,000 range. In addition, since many first-generation
sets will not have built-in tuners to capture specific channels, tuners
will be sold separately and likely will range between $1,500-$2,000. The
second and third generation of sets will have built-in tuners, similar
to today's analog receivers. As more sets come onto the market and retail
competition increases, and as more receivers are sold, these early prices
are widely expected to drop dramatically over the next few years.
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Will DTV interfere with other
local services, such as my local hospital's medical equipment?
Wireless communications are transmitted
over frequencies that are allocated by the Federal Communications Commission.
The FCC has permitted some users to utilize unallocated TV channel frequencies
for local emergency and other services (including some medical equipment).
As terrestrial broadcasters now apply to the FCC to begin to use this spectrum
for DTV, there may be the potential for equipment using these unallocated
frequencies to be interrupted. Hospital administrators should be aware
that if they are using unallocated frequencies for their medical equipment,
the potential for interruption exists. In early 1998, this problem arose
temporarily in Dallas and a handful of other markets. Hospitals, local
broadcasters and the FCC are working closely together on a market-by-market
basis to resolve potential frequency conflicts.
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More questions?
Contact John Merli in the PBS DTV Strategic
Planning Office at: jmerli@pbs.org
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