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When is HDTV not HDTV?

By Jim Bray

Now that HDTV is catching on, you're probably asking more questions about it.

Besides the logical “What's being broadcast in HDTV?”, one potentially controversial area involves what constitutes “real” HDTV. I don't mean the difference between 1080i, 720p etc. I mean the difference between 1080i and what you're seeing in the stores as 1080i.


Count the pixels (now there's a job for someone with great eyesight!)!

You may have had some sharp eyed, mathematically-inclined friend question the claims in your store. After all, it takes more than two million pixels (1920 x 1080) to show 1080i. Yet I saw a sign on a lovely 50 inch plasma a while back that claimed 1080i compatibility – and giving a pixel count of 1366 x 768.

Is that plasma really 1080i - or are you seeing TV's that aren't really HD-compatible? Is your favorite store guilty of false advertising?

Maybe – but when all things are considered remember the words of Star Trek's Mr. Spock: “A difference that makes no difference is no difference.”

So what gives? I spoke to some people far more knowledgeable than me (which is a large crowd!) and concluded that, while “true” HDTV isn't being sold by many mainstream retailers today, there's a good reason for it: the technology is immature and the cost/benefit ratio doesn't make building truly mainstream 1080i (or 1080p, which would be even better, for that matter) feasible.

It isn't easy getting 1920 pixels on a line or a chip; Sources tell me it takes nine inch tubes to do it on a CRT projection television, whereas most mainstream RPTV's today use seven inch tubes.

And smaller screen sizes mean smaller pixels, which exacerbates the problem. Sony's 1999-vintage direct view HDTV KW-34HD1 FD, for example, was a $9000US 34 inch TV that claimed 1080i, though its pixel count was under a million. This was because the electron beam required to create “that extra megapixel” would have been virtually invisible and created a picture that could only be watched in a very dark room – a negative for direct view TV's.

Besides, a new friend at Hitachi (whose name I'll withhold lest he go to work on my face) tells me that 1080i (and 720p) doesn't necessarily indicate the capability of the playback unit, but rather the recording medium. He also says the Society of Motion Picture and Television Engineers (SMPTE) allows 5% “overscan” at the top and bottom of the screen to eliminate video noise and “on set anomalies” like microphone booms hanging into the picture.

This isn't new; NTSC actually has 525 lines, interlaced, but the TV's are called 480i; the “vertical blanking interval,” that black line you can see when the picture flips, isn't counted. So taking overscan into account, 1080 pixels become 972 and if we continue the analogy to the horizontal resolution (assuming we can!), 1920 pixels becomes 1730 – for 1.68 million pixels (1730 x 972) rather than 2.07 million.

According to my Hitachi contact, the HDTV specifications as written were beyond what manufacturers could actually produce at the time. Only now are they catching up; new chips and LCD panels will reproduce 1,080 x 1,920, promising “true” HD at more affordable price points. Soon.

So the future's bright.

Where does that leave people today?

I've seen all sorts of HDTV displays over the years (including the analog system Japanese broadcasters used for years), and have been receiving Bell ExpressVu's Canadian HD offerings (which are getting better all the time) for a couple of years. I've seen HD on LCD rear projectors, front projectors, CRT rear projectors, and my eyes are dazzled every time there's a true HD broadcast.

And the “dumbed down” 1080i I get on my 57 inch RPTV is outstanding. The colors are deep and rich and textures look marvelous. Sure, Jay Leno's face looks pasty, but boy do his wardrobe people have good taste in suit materials! So maybe it's just Leno's complexion...

So the difference is, at least for now, moot. And because these HDTV's are now getting quite affordable, the market is exploding – and this is pushing broadcasters to convert to HD as quickly as they can.

Which begs the bigger question: why aren't there more HD broadcasts? Most HD channels merely simulcast standard definition programming with HD thrown in where available, and most commercials and promos are in Standard Definition. But it's getting better and will continue to do so.

But if consumers had had to wait for the technology to catch up with “true” HD, there'd be little incentive for broadcasters to make the changeover in this “chicken and egg” situation. There'd also be far fewer new HD-ready models coming from manufacturers – and fewer choices for you as consumers.

So while the HD you're buying right now probably isn't as good as it will be in a year or two, it's still a win win scenario. Today's models are getting quite affordable, and that means you can enjoy the growing HD market with fine quality and secure in the knowledge that when it wears out the new generations of HDTV that replace it will be even better.

Ain't technology grand?

Jim Bray's technology columns are distributed by the TechnoFile Syndicate


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