| The Bronx Journal
Online-Technology
High Definition Television (HDTV)
Mike Masinick
Advanced Television Technology Center
A new kind of television system that involves improvements in
both the production and reception of television broadcast system
What is HDTV?
High definition television (HDTV) is a new
kind of television system that involves improvements in both the
production and reception of television broadcast system. The most
distinguishing feature of HDTV is the aspect ratio. HDTV’s aspect
ratio is 16:9 (Width:Height) as opposed to 4:3 of the current NTSC
system. This will make the home theater atmosphere exactly as it was
meant to be.
Films will retain their original size and
re-solution, and the sound can be delivered in "CD quality" 5
channel digital audio. Current systems and recording media, NTSC
(National Television Standards Committee), the type of system that
everyone has in their home right now has 525 lines of resolution as
compared with 1125 lines of resolution that HDTV will offer. Back in the
1950’s, Hollywood came up with many tricks to get people out of their
living rooms and into the theater. Perhaps the longest lasting of these
features was the wide aspect ratio movie format. While regular
television is broadcast at 4:3 (the ratio of the picture's width to
height) movies have been shot in ratios even greater than 2:1. When such
a movie is shown on television, if its full height is to be broadcast,
its sides must be cropped to fit the TV screen, thus losing information
originally intended for viewing. However, newer video formats, such as
laser disc and satellite broadcast, often show a movie in its original
format with blanking on the top and bottom of the picture to preserve
its aspect ratio. Wide screen (16:9) televisions allow the viewer to see
the movie with little or no blanking, thus presenting the movie closer
to its original format.
Where are the Broadcasters putting this
signal?
Broadcasters have been granted FREE
bandwidth for use for the transition to HDTV. They actually have the
choice of what they want to do with that bandwidth. The bandwidth
required by HDTV is 6MHz which is 4 times that of a normal NTSC signal,
which means you can fit 4 channels in that bandwidth instead of 1! What
do you think some stations are going to do? Yep, broadcast 4 channels.
For example, NBC could broadcast regular NBC, MSNBC, a full time sports
channel, and a shopping channel, all in their own bandwidth.
Do I need a new antenna?
Well, if you have an antenna outside and
can currently receive channels 14-69 on your TV, then there should be no
problem in the switch to HD. If your antenna is on the back of your TV,
or you have a VHF only antenna, you will have to install a new antenna
outside.
All HDTV systems must have each of the
following components in order to function properly. a demodulator, which
separates the digital signals from the analog carrier wave on which they
are transmitted; a demultiplexer, which separates the audio portion of a
transmission from the video portion; an image decoder, which
decompresses an encoded video signal; an audio decoder, which does the
same for the audio portion of the transmission; and a display processor,
which transforms decoded video signals to various display formats.
As a consumer, you really don't need to
know what is inside, but this helps you understand what the industry has
to do in the next year...
Will HDTV make my $4000 television
obsolete?
Again, hard to say... here is where it gets
hard to understand. No matter what you do, your large screen that you
have now will only get 525 lines of resolution. Resolution is what makes
the picture clearer. You will be able to buy a set-top box that will
convert the 1125 lines of resolution of HD into 525 lines of resolution
of the current system. It will put ugly black bars at the top and bottom
of the screen and yes, you will be able to see what is being
transmitted, but NOT in high definition. Some people say that DVD on a
normal TV looks as good as high definition. Trust me, these people have
not seen a demonstration of HDTV. I do not know one person who has seen
true High Definition that thinks DVD or any other NTSC system is better
or clearer.
Will my VCR be able to record and playback
HDTV?
No. VCR’s today are all analog. Digital
Video and audio can not be recorded on those systems. It is likely that
you will be able to play back your current library of tapes on the HD TV
with black bars on the sides to compensate for the aspect ratio
difference.
What will I be able to receive if I buy one
of the first HDTV's?
Each city will have a different answer for
that. I am fortunate to live in Washington DC which is one of the major
hubs of HDTV activity. With any luck there will be 4-5 stations
broadcasting in High Definition in Washington, New York, and Seattle in
the next year. Other slightly smaller markets such as Miami, Dallas, and
Chicago will have 2-3 stations... and most other markets will vary. It
all depends on what the individual station owner wants to do.
There are 2 stations currently on the air
in Washington. WHD and WETA. While they are broadcasting either a camera
out the window or colorbars most of the day, they are still on the air.
It is interesting now having one of the only systems that can receive
HDTV. I get to see everything that is broadcast.
In September 1990 the FCC decided to select
a simulcast HDTV system. Broadcasters would be required to send two
over-the-air transmission signals, one in NTSC (analog) and the other in
HDTV (digital). The FCC believes that terrestrial transmission will be
the quickest and least expensive way to introduce this exciting new
service to the American people. Two years later, in 1992, the FCC
proposed a timetable for HDTV implementation. The timetable breaks down
as follows.
Existing full-power broadcasters would have
2 years to apply for HDTV spectrum. 3 years to build new HDTV
facilities, 7 years to simulcast 50% of their programming in HDTV, 9
years to simulcast 100% of their programming, and 15 years to fully
convert their stations from NTSC to HDTV. After the 15 year conversion
period, broadcasters would have to give up one of their channels and
quit broadcasting in NTSC. This conversion period has not yet been
adopted, but the debate over implementation continues.
Will the cable industry soon be sending an
HD signal?
It is technically possible for digital
television to be transmitted over a cable system's existing 6 MHz cable
channel. But there is not guarantee that your local cable system is gong
to carry HD. The FCC requires that all cable companies carry the local
stations, but they do not mention High Definition.
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