Just what the heck is digital TV?

Posted: 06.14.04

Digital TVUnless you've been in deep freeze waiting for millennium meltdown or Longhorn, most countries are either in the process of, or have a schedule for, the introduction of and then the cut-over to all digital (free) terrestrial transmission of TV. The justification, of course, is that DTV will save bandwidth and thereby give us more utilization of the limited spectrum we have, including the much-heralded but not realized interactive TV (ITV).

The difference between analog and digital TV is the method of modulation, not the content, not the quality, not the resolution, and not the refresh rate—just how the signals are wiggled from the transmitter to your aerial. That means the 6-MHz analog channel can now carry 19.44 Mbps, and in that stream you can squeeze in several formats and aspect ratios all the way up to 1080i 16:9 known as HDTV. However, once those signals come sliding down the wire from your aerial to your TV viewing room, you now have a problem because your old reliable interlaced analog CRT TV speaks analog and these new signals are talking digital and those two couldn't be more different than a Republican and a Democrat in not understanding or being compatible with each other.

So you have two choices if you want to watch DTV. You can buy a digital-to-analog converter box for your old reliable analog interlaced CRT TV set, or you can buy one of those new-fangled digital LCD TVs. The problem is you're going to have a little difficulty finding either device.

You can buy an STB box from Pace, or SA, or an HDTV satellite receiver from DirecTV, and either of those boxes (with an average price of around $300, and as low as $100 in the U.K.) will allow you to hook up your aerial to it and then send out an analog signal to the TV. Here again you have a couple of choices. You can use the RF input of the old analog TV and set the TV on channel 2 or 3 just as you did in the old days with your VCR, or you can hook the STB to your RCA jack marked video-in, if your old analog TV has such a connector. Some STBs will even offer an S-video output.

About the cheapest actual digital TV, that is, a TV that actually has a tuner in it that can actually receive digital TV signals, is $2,500. The problem is the TV set manufacturers are not offering very many sets that actually have a digital TV tuner in them. Instead they are playing dodge ball and advertising "digital TV ready." The buyers of the newer sets are getting systems with built in line doubling, which is possibly the biggest improvement in TV since color. When seen on a digital display like a plasma or LCD, with every pixel bright and in focus, the comparison to an old analog CRT is astounding. The net result is people think they have digital TV and many think they have HDTV.

This is a problem for the TV industry, as well as the cable and satellite industry. And when I say industry I'm not just referring to the box builders, I'm talking about the entire food chain from commercial production (and the sales of those commercials) to the final delivery of the content, as well as the recording of it. The FCC's mandate governing the "phased" introduction of digital TV tuners to new TV sets spotlights an arena where multibillion-dollar issues will be thrashed out over the next three years.

The other problem is the overuse and lack of differentiation of the term "digital" when referring to TV. C-band satellite TV has always been digital and encoded in MPEG-2, requiring an MPEG-2 decoder in the receiver, which currently is an STB. Cable TV in the U.S. and parts of Europe is switching from analog to digital and sending an MPEG-2 transport stream to households, and today they too are STBs. So we have DTV in our homes now if we have satellite or digital cable. But, what comes out of the STB and goes to the "TV" which is being reduced to nothing more than a display device is analog—even if it is the much-vaunted Y,Pr,Pb component commonly referred to as "HD," it is still analog. However, the screen itself can be digital if it is an LCD or plasma. And of course the DVD and DVR are digital devices based on MPEG-2; but they too put out an analog signal for the TV.

A "pure" digital TV then is one that has a digital tuner, a digital de-compressor, and a digital screen, with all the interconnects and signals between these major components digital as well. A HDTV STB that outputs component video signals to a digital projector is not a pure digital system. The first probable pure digital TV will be a self-contained LCD TV with a digital tuner. Until we can buy one of them everything else is a hybrid. So when someone tells you how many digital TVs are being sold, ask them for their definition of digital TV.

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Everyone talks about how great open standards are and often point to the automobile industry as an example of the success of such things. Look at the location of the steering wheel, gas pedal, and brakes they'll say, and the DOT standards on bumper height and middle stop light. Ah huh, right. Well try using any lightbulb from one brand to another or a tire. Swap a radio? Forget about it.

Fact is there are very few truly open standards.