HDTV Answer Guide

Illustration by Tyree Palifka
Illustration: Tyree Palifka
As high-definition television programming finally approaches critical mass and the prices of everything from smaller CRTs to big plasma displays continue to fall, millions of Americans are considering making the upgrade to HD's sharp, luscious picture and movie-quality sound.

But if you visit your local consumer electronics store without doing a little research first, you may leave with more questions than you had when you went in. At the very least, you should know what HD programming you'll be able to get in your area, what equipment you'll need to get it, and whether you'll have to make compromises with your new set that you don't with your analog TV. Here's a good start on that research.

Q. What's the difference between HDTV and digital TV?

A. Under a federal government mandate, broadcasters are switching from our half-century-old analog system to a digital one that promises to use public airwaves more efficiently and to improve broadcast quality. The target date for completing the transition from analog to digital is 2006. In the United States, digital TV is based on Advanced Television Systems Committee standards. HDTV is a subset of digital TV; it is an umbrella term for the higher-resolution formats that are included in the ATSC standards.

ATSC transmission formats are defined by image resolution (the pixels per line and the number of lines per frame); by aspect ratio; by the refresh rate of the image (in frames per second); and by how images are scanned, transmitted, and received. With progressive scanning, the scanner first creates and transmits a line from left to right; then it draws the next line underneath, then the next, and so on, creating each frame in a single pass of sequentially drawn horizontal lines. With interlaced scanning, the scanner creates the odd-number scan lines in its first pass; then it starts over from the top of the screen to complete the image by scanning the even-number lines. Progressive scanning tends to make action scenes look smoother, but interlaced scanning permits greater perceived resolution in the same amount of bandwidth.

Current National Television Systems Committee (NTSC) analog transmissions consist of 480 lines of interlaced video information (plus a 45-line interframe gap inserted for synchronization purposes, making a total of 525 lines). The most similar digital TV counterpart is the ATSC's 480i format, denoting frames with 480 interlaced lines. Known as standard-definition TV, 480i most commonly is broadcast in a 4:3 aspect ratio (a wide-screen version with a 16:9 aspect ratio uses the same number of pixels per line, 704).

The term HDTV applies to 720p, 1080i, or even higher-definition broadcasts (and to the equipment capable of displaying those formats). All such formats are transmitted in a 16:9 aspect ratio, so 1080i refers to a 1080-by-1920-pixel image produced by interlaced scanning, while 720p denotes a 720-by-1280-pixel image produced by progressive scanning. The broadcast networks have committed to different versions of HDTV: Both CBS and NBC have opted for 1080i; ABC and Fox, for 720p. (There is also a 1080p format, but as yet no company makes consumer equipment to handle its huge bandwidth and high processing requirements.)

Yet another ATSC format, 480p, has 480 lines scanned progressively. Though its resolution matches that of standard-definition TV, the progressive scanning results in a better image. This format is known as enhanced-definition TV. The Fox network has been broadcasting some EDTV shows, but it intends to begin its HDTV broadcasts next fall. Most commercial DVD movies are recorded in 480p as well as in 480i; for this reason they will look better on a set that supports EDTV.

Q: So what about watching 1080i or 720p on an EDTV set? And what about switching among broadcasts with different resolutions?

A. Your ATSC tuner will convert whatever format it receives into whatever format your set supports.

Q. What's the difference between an HDTV set and an HD-ready or HD-capable set?

A. High-definition content must be displayed by a tuner that can process the HD signal and by a set capable of displaying HD resolution. A true HDTV set comes with a built-in ATSC-compliant HD tuner (such tuners support all HD formats, so you don't have to worry about which one you're receiving). Some TVs that can support HDTV resolutions lack a built-in tuner; these HD-ready sets require purchase of an external tuner--costing up to $500--in order to receive HD programming.

Q: Why might I want to buy an HD-ready set instead of an HD-capable one (besides to save money)?

A. You might want to purchase an HD-ready set if your cable or satellite company provides a set-top box with an ATSC tuner--there's no point in having two of them (one in the box, one in the TV).

Q. How much HD programming is available?

A. The National Association of Broadcasters reports that ABC, NBC, CBS, and the WB were broadcasting more than 60 prime-time shows in high definition by early 2004.

Under FCC rules, commercial broadcasters had to begin digital TV transmissions by May 2002, and the National Association of Broadcasters' Web site says that 1155 of the United States' over-the-air broadcasters met the deadline. But while the FCC allocated sufficient bandwidth for these stations to broadcast HD content, it established no statutory or regulatory requirement that they do so. At least a few stations have begun using the bandwidth to broadcast standard-definition digital channels--a practice known as multicasting--because they can fit about half a dozen such broadcasts within the bandwidth of 19.4 megabits per second that is required for a single HD channel.

Though the FCC has made no hard-and-fast rule that stations must broadcast HD content, "There's a general understanding that we have to be good stewards and not completely subvert the positioning of HDTV broadcasts," says Steve Pair, vice president of engineering for WCBS (the CBS-owned-and-operated station in New York). The FCC says broadcasters may use the channels "according to their best judgment" as long as they offer free digital service at a resolution comparable to that of the analog shows they air during the same time periods.

A likely scenario, in Pair's opinion, is that stations will use some portion of the 19.4-mbps bandwidth for additional broadcast streams, which would remove some data from an HD show but not enough to degrade the quality of the image significantly.

Q. Can I expect my cable or satellite provider to deliver all those channels?

A. Probably not. Cable carriers don't want to be obligated to carry all of the different data streams that terrestrial (over-the-air) broadcasters choose to send out. The result is an unresolved dispute over how the FCC's must-carry rules (which in effect have required cable services to offer a full range of local programming) should apply to digital TV. Right now they don't, except in the rare instances in which a station has a digital signal but no analog one. Consequently, to pick up local stations, you'll likely have to resort to a special over-the-air HD antenna (pictured on the next page).

HD in the sky: Voom's satellite brings in 34 HDTV channels.
HD in the sky: Voom's satellite brings in 34 HDTV channels.
Most cable and satellite services offer at least some HD content, but it varies depending on the operator. Traditional satellite services have little HD content: DirecTV, for example, offers only eight channels. Four of these (HDNET, HDNET Movies, ESPN HD, and Discovery HD) are in an $11-per-month bundle (on top of whatever your standard service costs); both the HBO and Showtime HD channels are free to customers whose packages include those services. Customers can also buy $5 pay-per-view movies--that's $1 more than other PPV films cost--or adult content.

You can get a lot more HD from the Voom satellite service, which at this writing offers more than 30 channels of HD content (including 21 that it developed and provides exclusively). There is a trade-off, however: Voom offers far fewer standard-cable channels than DirecTV does.

The best way to determine what's available in your area is to get a good online programming guide. Decisionmark's TitanTV, for example, identifies the particular broadcast stations and HD content (as well as the SD content) that you can get at your location. And it's free.

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