Ten HDTV myths

High-definition TV is just around the corner, so we dispel some of the HD myths proliferating around the US television industry.

Plasma TV sets start out bright and beautiful, but burn out to an early death. Every single high-definition television program looks equally crisp and gorgeous. The higher resolution of a 1080p high-def set means that your programmes and DVDs will always look better than on a ordinary 720p set.

Are these gospel truths about HDTV? Nope. Just a sampling of the many popular factoids, half-truths, and myths that can make choosing and enjoying a high-def television set complicated and confusing – and in some cases, needlessly expensive.

To help dispel these myths, we consulted an A-team of HDTV experts. The challenge: Identify and debunk troublesome, costly, and all-too-prevalent misconceptions about high-definition TV – from the basics of broadcasting to the arcane secrets of hardware.

MYTH 1: An HD set is all you need to get high-def programs.

Sadly not. To experience the vibrant images and the Dolby 5.1 sound of true high-definition TV, you need several things – and an HD-ready set (a display that can accept HD-format input and display it at a minimum of 720 lines of progressive-scan or non-interlaced video) is just one of them.

First, a programme needs to be shot in HD, and that may not be the case, even when a show claims that it is. Bjorn Dybdahl, owner of Bjorn’s, a high-end audio-video store in San Antonio, Texas, says that he’s seen many high-def sports broadcasts shown partly in standard definition because the producer is using some non-HD cameras in its coverage.

Second, the program must be transmitted in HD by a station that you can receive either over the air or from your cable or satellite provider.

Third, you need an HD receiver to process the signal. A set that has a built-in ATSC digital tuner can display over-the-air HD broadcasts with nothing more than a good antenna. ATSC, which stands for Advanced Television Standards Committee, is the group that defined the 18 formats of the coming digital TV system, only six of which are considered high definition.

And by the way, there is no such thing as an HD antenna--there are just antennas. If your HDTV set comes with picture-in-picture, you won’t get high-def-picture-in-high-def-picture unless your set comes with two ATSC tuners.

An HD-ready set lacks such a tuner, so you’ll need either a set-top box with a tuner, or an HD box from your cable or satellite service. Regardless of the box you get, you need to make sure that you’re feeding its digital output into your HD-ready set. “A lot of people will get an HD-ready set [and] an HD cable box, but they will use the analog feed from the HD box,” says Jeff Cove, Panasonic’s vice president for technology and alliances.

Finally, you must tune your HDTV set to a high-definition channel showing actual HD content. Picking up the analog transmission from your local affiliate on your high-def cable box won’t result in delivery of a show in HD.

MYTH 2: The bigger your HDTV set, the better it will look.

Bigger isn’t better if you are seated so close to the set that you can see every pixel or line of resolution. Generally, you don’t want to sit closer to a 720p HDTV than twice the length of the screen diagonal.

On the other hand, if you sit too far away from a high-resolution TV, its special benefits may disappear. “For an awful lot of viewing, what limits the resolution is the human eye,” says Larry Weber, president-elect of the Society for Information Display, a group of display industry pros.

At a distance of 10 feet from the screen, the eye can’t detect pixels smaller than 1mm; so if you look at a 37-inch set from that far away, you won’t notice significant difference between a high-definition image and a standard-def image.

Content also affects perceived image quality. Digital TVs are fixed-pixel displays – the screen resolution is hard-wired, so content has to be scaled, or adjusted, to fit the screen resolution.

Not surprisingly, most television content is most attractive when displayed at its native resolution. That’s why today’s DVD movies, which reproduce the original film at 480 lines of progressive-scan video, may look better on an Enhanced Definition TV than on an HDTV: EDTV has the same screen resolution (480p) that DVDs have, while HDTV must scale the number of lines to 720p or 1080p (depending on the set), usually via software interpolation.

Conversely, to display HD programming, an EDTV has to eliminate lines of content (once again, usually by software interpolation), and on larger sets the resulting quality loss may be quite obvious.

MYTH 3: The higher the screen resolution, the better the image quality of an HDTV.

Most HDTV sets today are 720p displays, but a few vendors are beginning to offer 1080p sets – either LCDs or rear-projection micro-display (LCD, LCoS, DLP) models. As yet, no 1080p plasmas are available (though some have been announced in very large sizes). These sets will clearly do the best job of handling 1080p content – when it arrives.

But today’s HDTV shows are shown in either 720p or 1080i format: nobody broadcasts in 1080p because of bandwidth issues. Movies may someday be available in 1080p on optical media, but Hollywood hasn’t settled on the next-generation hardware standard (Blu-ray or HD-DVD), much less chosen a content format.

MYTH 4: You have to relinquish the fluid motion of a CRT screen when you move up to HDTV.

Not at all. You can purchase a high-definition CRT set – and you’ll save a lot of money if you do, because they cost less than LCD and plasma-screen televisions of similar size. But in doing so you’ll lose the sleek flat-panel chic of a plasma or LCD set.

If you want that slim profile, however, be aware that LCDs have trouble rendering fluid motion, as a result of their somewhat pedestrian response times. Plasma and DLP screens aren’t susceptible to this technological weakness.

MYTH 5: Burn-in will wreck your plasma HDTV within a year.

The plasma display has advanced since the days when most of us saw plasmas only at airports, where constantly switched-on screens showing formatted flight information suffered from burn-in – ghost images that linger on screen despite no longer being transmitted.

Today, vendors rate the life expectancy of high-quality plasma TVs at 60,000 hours. That works out to more than 20 years of use if you watch eight hours a day, 365 days a year. “If you’re not worried about burn-in for your CRT, you shouldn’t worry about it for your plasma TV,” says the Society for Information Display’s Larry Weber.

MYTH 6: Bright LCDs look beautiful everywhere, and they use much less power than plasma or CRT sets do.

It’s true that LCDs are bright, which makes them a good choice if you watch TV in a brightly lit room. But if you’re inclined to turn down the lights for your rendezvous with Entourage or Medium, you probably don’t want the brightest set on the block, and plasmas and CRTs offer superior colour capabilities without introducing the response-time (and associated motion artifacting) issues that have long plagued LCDs.

As for power consumption, a study by Japan’s Green Purchasing Network – an organization dedicated to promoting environmentally friendly purchasing by consumers, business, and government – concluded that the power consumption of similar-size plasma, CRT, and traditional LCD displays in real-world viewing situations is practically the same.

However, the coming generation of LCDs that use LED backlighting, while expected to deliver significantly better colour, will consume roughly twice as much power as traditional LCDs of the same size.

MYTH 7: These pricey TVs look so great out of the box that it’s a waste to pay a small fortune to have a professional calibrate your set.

That’s a double-whammy myth. It’s well known in the TV business that vendors usually ship sets turned to their highest possible brightness level, since brightness draws customers on the showroom floor.

At home, however, many people watch TV under low lighting conditions in which an overly bright set can look jarring. In addition, the TV may arrive with less-than-accurate colour settings. Consequently, almost any set will benefit from calibration.

A professional calibrator has tools that can access settings most of us can’t reach – and shouldn’t, since we wouldn’t know what to do with them. But the pros do charge a few hundred dollars for their services, and you can achieve reasonably good results on your own with software such as the $40 DVD Essentials.

MYTH 8: All true HDTV programming looks equally great.

This claim gets us to a dirty little secret of HD broadcasting: All HDTV programs are compressed – some to a greater extent than others. The FCC allots each TV station sufficient airwave spectrum to broadcast a little over 19Mbps of data, but stations aren’t required to devote their share to a single HD program.

They may compress an HD show enough to leave room for one or two SD broadcasts as well – a practice known as multicasting. The ATSC standard includes support for MPEG2 video encoding, but it says nothing about compression levels.

Broadcasting an uncompressed MPEG2 video would require 885Mbps (for 720p content) or 995Mbps (for 1080i content).

If a station uses its bandwidth to broadcast both an HD show and a standard-def show, the HD program has to fit into 13 or 14Mbps.

Such high compression produces artifacts that might not be noticeable on a small CRT, but can be quite obvious on a big fixed-pixel display.

These include mosquito noise, an effect in which small dots seem to surround a person’s head; and macroblock errors, similar to what a fast-moving video game looks like on a PC with too little graphics power.

MYTH 9: Standard-definition TV is unwatchable on HDTV.

Well...this is a case of hyperbole, not of outright fabrication. True, standard-def programming will never look as good as HD programming on an HDTV because of the scaling issues mentioned previously.

But vendors are toiling to better the SD experience on their HD sets, and the success of these efforts varies between vendors and sets. So if you’re expecting to watch standard-definition TV on an HD set, make sure that you do your own taste tests.

MYTH 10: I’ll have to toss all my current analog sets when the digital conversion kicks in.

Though this is not strictly an HDTV issue, it is a common misconception about the digital transition, which Congress seems bent on completing by 2008. At that point your old sets won’t be able to snag over-the-air broadcasts without help, but you should still be able to use them by buying inexpensive digital-to-analog converters. And cable or satellite boxes will still work because the service provider will take care of the conversion.

The truth is out there

These may not be the only myths you’ll encounter in your quest for the perfect HDTV – and you can’t trust everything you hear (or see) in a showroom. So careful research is essential before you pay for what’s likely to be the most expensive TV set you’ve ever bought. And that is the gospel truth.

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