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What HDTV will mean to us

technofile  by al fasoldt

Columns and commentaries in a life-long dance with technology
 

Simple gray rule



What HDTV will mean to us 


By Al Fasoldt

Copyright © 1989, The Syracuse Newspapers

Because no final standards for High Definition TV exist, prototype sets come in a variety of forms. But they all have these features in common:

  • A sharper and clearer picture than standard TVs.
  • A wider screen than present sets.
  • Hi-fi stereo sound.

HDTV pictures are better because HDTV sets use many more scanning lines to draw the images on the screen.

These lines are drawn from left to right by an electron gun inside the set. It shoots electrons—tiny particles that help make up atoms—at the back of the screen, and this makes the front of the screen glow.

In a regular TV set, these lines aren't very close together. If you get close to the screen, you can see them clearly. They make the picture look segmented, as if you were looking out a window through a lot of tiny slats.

Present sets can have a maximum of about 450 lines, counted from top to bottom. But usually TVs have fewer scanning lines than that, with the average set showing about 350.

High Definition sets have about three times that many, or about 1,100 scanning lines. The lines are closer together and seem to disappear. The result is an image as sharp and clear as the picture on a motion picture screen.

Adding to the theater-like quality is the shape of the screen. The shape—or, more precisely, the "aspect ratio"—is intentionally designed to match theater screens.

This wider shape adds a panorama effect, and it also makes sure that theatrical movies can be seen full-frame for the first time on TV. To be seen on old-fashioned sets, movies have to be cropped at the sides, and the scenes often have to be panned left and right to get the main action in the picture.

The sound quality of HDTVs is expected to be much better than current sets. All HDTVs will have stereo sound, and most are also expected to have alternate sound channels. These could be used for second languages such as a Spanish sound track for a TV show, and they could also be used for FM stereo broadcasts.

All of this comes at a price, both in dollars and in the space used in the television frequency spectrum.

HDTV sets are expected to cost as much as $5,000 when they are introduced in the early 1990s. But the price could drop quickly. Arno Penzias, head of research for Bell Laboratories, says the price should come down to $1,000 once HDTV starts to become popular.

But the price of space in the broadcast spectrum may not come down so readily.

Just as an unabridged encyclopedia takes up more space on the shelf, the more detailed HDTV signal takes up more of the radio spectrum.

With such devices as cellular telephones taking up radio frequencies that could have been used for TV, there are only a few frequency blocks left—only a few more spots on the dial.

Some HDTV developers take the brute-force approach, insisting that High Definition Television is so important that it is worth hogging the spectrum.

But others have been working hard to get around this problem, possibly by compressing the HDTV signal to fit into a regular TV spectrum.

An even more pressing problem is compatibility. The Federal Communications Commission has ruled that any HDTV system used in the United States must be compatible with existing sets. This is the same kind of rule the FCC came up with four decades ago, when it rejected a superior color TV system designed by CBS in favor of an RCA system—because RCA color broadcasts could be viewed on older, black-and-white sets.

Many in the industry worry that the FCC is shooting itself in the foot again. Some Japanese, in particular, have argued that compromising the quality of High Definition Television in this way can be compared to the laws that required footmen carrying lanterns to walk in front of all motor vehicles 100 years ago.

But Zenith and some other companies have developed HDTV systems that comply with the FCC rule. Zenith's approach is to broadcast the HDTV signal over an unused channel while sending the old version over a normal channel.

Another approach is to transmit the center of the HDTV picture—the part that is the same shape as regular screens—over a normal channel, while sending the rest of the HDTV picture over a special channel that only High Definition sets could receive.


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