Now, people don't want to watch a postage-stamp-size image on their shiny new HDTV, so the TV will scale the image to full size. So you get a full-size image, more or less. The problem, as you can see, is twofold. The first is that the square image doesn't fill the rectangular HDTV screen. This can only be fixed by adjusting the aspect ratio control on your TV.
I don't recommend this as you'll get a stretched image, lose information at the top and bottom of the image, or both. The other problem, and the one we're talking about here, is that the TV has to create new pixels in order for the original image to fit the screen. No matter what, it's going to be softer than a true HD image. How well a TV creates this new information varies from set to set. All TVs do it, some better than others. Faced with a limited resolution to start with, the upconverter in the TV has to "guess" to create detail.
At its core, detail is the transition from one color to another. The transition from white to black that lets you see the words on this page is a good example of fine detail at its most basic. If we zoom in on something simple like that, we can see the challenge upconverters have. Here is a black line, in its original form, as seen in its native resolution. I've zoomed in so you can see the pixels that make up the line:.
Now, if you were to do a simple upconversion on this image, and show it on an HDTV, it might look something like this:. As you can see, more pixels are used to create the same image.
There are also more pixels used for the transition from black to white. The problem is, those extra "transition pixels" when viewed at a distance make the image appear soft. The upconverter's job is to minimize this softness, perhaps giving something like this:. Better, right? Still not perfect, though. Had this line been created as an HD image originally, it would have perfect black-to-white transitions.
If you can set your box to output the channel in its native resolution, it's worth seeing if your TV does a better job upconverting it. For the most part, the greater the resolution, the sharper the picture quality becomes. This is due to the fact that more visual information can be projected, which may increase the level of detail in the image.
An upconverting DVD player typically uses a computerized algorithm to increase the resolution of basic DVD video and, in theory, increases the quality of the image. The increased resolution provided by an upconverting DVD player may not always increase picture quality, however.
Pixels are usually copied and added to the base image in order to increase the overall number on screen. As a result, the picture quality may not grow sharper with upconversion, but may in fact become blurry, especially on larger screens.
The fact is that, even without a new DVD player, the image will be upconverted. When an HDTV built around one of these technologies receives a DVD's line signal, the television upconverts the image before displaying it. Upconverting, or upscaling, is a complicated process. Some DVD players do it better than others. Same with HDTVs. In my experience they usually do, but the differences are seldom significant. Upscaling at the player level has one theoretical advantage.
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