What is "True HDTV"?

Since I have a big family, I shop at Costco all the time as I need everything in bulk. But as many of you know, Costco also sells individual items such as lawnmowers, small swimming pools and plasma televisions. It's the latter that always draws me to the electronics section of the store because it's always fun to see the latest mass-market product be displayed under ridiculously bright lights with a questionable video distribution system -- and an HDTV image.

In spite of the "unfriendly" environment that these units are being displayed in, I'm always fascinated by the reaction of many fellow Costco shoppers when they see the image. It is obvious that these people, most of them presumably NOT in the AV business like us, are blown away by how good the image looks even with the light blaring down on these poor 'ol '480p' plasmas. I guess the point is that even with a ton of light interference and a mediocre video distribution system, a high-definition signal STILL looks better than any other video source, to even the most extreme of laymen.

This describes HDTV in the worst-case scenario. So if that is good, what is "True HDTV"? It may seem like a simple question with a simple answer, but in reality it's the one thing that keeps many people from buying certain video displays because of the fear that they won't be watching "true" HDTV. Let me assure you that you can all rest at night, because the reality of HDTV is that it's pretty darn good no matter what you watch it on.

That said, there is a technical side to DTV/HDTV, and the question about true HDTV is a valid one. You see, there are 18 different ASTC formats, many of which are high-definition. Each format has its own resolution such as 720p (1280 x 720 progressive) or 1080i (1920 x 1080 interlaced), with each having its own pros and cons. We won't go too deep into that, but the one thing that is relevant here is that we are in the era of the fixed-pixel (DLP, LCD, etc.) display, and these displays all have their own specific or "native" resolutions. The bottom line is that to get the best performance out of an image, the input resolution should match the display's resolution so no scaling (additional processing) is required. Otherwise, it is possible to "lose" something in the translation.

Here's an example. Let's say that you own a Runco CL-810 DLP projector, which has a native resolution of 1280 x 720. If you input a 720p signal to it, you'll have matched the resolution of the input signal to that of the display. But what if you input a 1080i signal to the same projector? It will still display it of course, but the 1080i signal would have to be scaled to match the resolution of the projector. Likewise, if you have a Vidikron Vision 80 projector with a native resolution of 1920 x 1080 and input a 1080i signal, you'll have effectively matched the resolution of the projector, but if you input a 720p signal it will have to be scaled to match the 1920 x 1080 resolution of the projector.

In the days of the CRT projector, none of this mattered. CRT projectors had the ability to display any resolution in their native form since these projectors are not limited by a fixed number of pixels. But while that was a significant advantage, their low light output and complicated setup offset the resolution advantages. Slowly but surely the CRT faded into oblivion, and with it went the ability to display any resolution natively.

Now we're in 2005 and well into the era of the fixed-pixel display. Since we don't have the resolution advantage of the CRT, does this mean that we won't get "true HDTV?" Hardly. While it is true that some scaling will be necessary for non-native signals, scaling algorithms have become so good that it's becoming almost unimportant to talk about. There is absolutely nothing wrong with watching a 1080i image on a 1280 x 720 display, for example, nor are you getting any additional benefit from watching a 720p signal on a higher resolution display.

Many folks are still clinging to the idea that in order for an image to be 'true', an input signal must match the resolution of the display precisely. But did you know that even a "native" signal has to be processed? Whether it's an analog (e.g. component) signal that has to be converted to digital or a digital signal (e.g. DVI) that has to go through a "digital to digital" process, you're still processing it. All that said, let's throw that issue in the round file.

Another issue is that your satellite and/or cable provider is also compressing the HD signal to some extent. In order to shoehorn all those high-definition images through the satellite or cable system, the signal must be compressed to save bandwidth.

The moral to the story is that being in the digital age has its advantages and disadvantages, but no matter what, we're still benefiting from video technology that is FAR beyond anything the typical consumer has ever had in their homes. As noted at the beginning of this article, even bad HDTV looks good (though we strive to do better than that!). Scaling, compression and other forms of processing are realities of life now, much like having a car requires that it have tires to be useful.