We Want Our . . . We Want Our . . . HDTV

In the immortal words of Fat Bastard, Austin Powers’ huge, boil-encrusted Scots enemy, "Crrrrrrap!" The word sums up just about every "high-definition" programming source except hi-def Blu-ray and HD DVD discs, which are still the only sources to actually deliver on the promise of high-definition video. But how can that be? Hi-def is digital. And digital is perfect.

The hype and the reality are very different. In the real world, great hi-def and crrrrrrap! coexist. It all boils down to compression and bandwidth. Lower-resolution HDTV now even has a more-or-less official name: HD Lite.

The amount of MPEG compression applied by the mastering engineer can be varied from very little to way too much. Small amounts of MPEG compression don’t do much harm to images, but the more compression used, the greater the damage.

Below right is an example of what compression does to detail in a still image. The image is zoomed to make details larger. Zooming-in makes the detail look a bit soft, but that’s OK for this example.

The right side is the same image with compression applied. Notice that not only is there much less detail on the right side, but some colors have changed as well: The bright green blotch at the middle right doesn’t appear in the left-hand image. Compression shifts the fuzzy lavender flower in the upper left of the right-hand image to blue and changes its shape. The three yellow buds just below left center of the left-hand image have, in the right-hand image, bunched up and turned darker. All the detail visible in the center of the left-hand image has lost color and has no real shapes visible in the right-hand image.

The same sort of thing happens when you compress moving images with MPEG compression.

HDTV broadcasts received via an antenna could potentially be OK, but more and more local broadcast affiliates have added to these signals as many as three standard-definition channels, which must share the limited digital broadcast bandwidth with the HD signal. Those extra SD channels need their own bandwidth, and that’s always stolen from the HD signal, which must be compressed to make room for the SD signals. When you’re used to low-resolution, standard-definition TV images, HD Lite looks impressive at first. But when you get close to the screen, you’ll probably find that everything in the picture is made of "blocks" rather than looking smooth and detailed. This "blocking" is another of the visible results of MPEG compression, which removes detail from images and leaves something of considerably less than HD quality. As much as such compression degrades HD, usually the result still looks better than SD. But though they continue to get away with calling it "high definition," it isn’t. Even if the channel runs an onscreen "HD" logo, what you see can be much worse than you would ever expect.

Cable and satellite are the next step down -- when it comes to HD image quality, both signal sources are crrrrrrap! These companies turn the MPEG compression knob up to 11, which results in images that are of only fair quality even when there’s little motion onscreen, and that are downright horrible with quickly moving images. Cable companies try to squeeze 100 analog channels, 200 digital channels, and up to 30 HD channels, plus pay-per-view and on-demand broadcasts, Internet and telephone service, and who knows what else, all down that single wire coming into your house -- a single wire shared with tens of thousands of other customers. The satellite services do the same thing; satellite bandwidth is expensive, and a single dish can be aimed at only so many satellites.

Then there’s the Internet. What passes for "streaming HD" online is a joke -- it’s far worse than SD. It may fill a widescreen PC monitor, but it’s nowhere near the full HD resolution of 1920x1080 pixels. Home Internet connections, no matter how blazingly fast, are still not fast enough to deliver HD in real time -- you have to buffer the content for quite a while before you can start watching, or you risk having the program stop midstream. Full-resolution HD images display at the rate of 372 million pixels per second, and each pixel has 8 bits (10 bits would be better, but we’re unlikely to get that anytime soon). That’s 3 gigabits per second. Non-destructive compression techniques can get this down to the range of 1.5Gbps, but the more compression is applied after that, the more degraded HD images become.

My DSL service is the fastest available to residences in our area -- about the same speed as fast cable Internet connections. Tests show it running up to 2-2.5 megabits per second for downloading. But you’ll need an Internet connection 600 to 750 times faster than that to watch content of HD-disc quality without long download times. Of course, to do this, you’ll need all-new Internet infrastructure. So if you’re thinking maybe you’ll just skip discs altogether and wait for the Internet to deliver your HD content, think again. It’ll be years -- perhaps a decade -- before the infrastructure and Internet connections have enough speed and bandwidth to deal with millions of connections simultaneously receiving uncompromised 1.5Gbps HD. Undoubtedly, there are services that claim to deliver HD programming now, or that promise to in the near future, but it’s nowhere near what you get from hi-def discs.

Bottom line: Just because programming bears an "HD" logo doesn’t mean it’s HD. High-definition discs are going to be your only source for "perfect" HD programming for quite some time.

 ...Doug Blackburn
db@hometheatersound.com

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