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Monday, June 30, 2008

Modern Snake Oil: The "Upconverter"

I've finally lost it. I simply cannot take one more mention of, news story about, or claim that an "upconverting dvd player" will give you a picture which is "almost as good as HD."

A quick primer: digital devices display an image at a certain resolution. Many PC monitors, for instance, display at 1,024 x 768. This means the image is 1,024 pixels wide by 768 pixels tall, making for a total of 786,432 discrete pieces of possible information which can be displayed on your screen. Most TVs before the big HD/flat panel wave display an image at 720 x 480, which multiplies out to 345,600 pixels. Less information, right? Certainly you've noticed that your PC monitor looks sharper than your old TV. Most new televisions display images at 1280 x 720 or 1920 x 1080 resolution, equaling 921,600 and 2,073,600 pixels, respectively. This is significantly more detail than is possible with a 480i/p screen.

Wait: i or p? Don't fret. I stands for "interlaced" while p stands for "progressive." This simply describes the way the display renders the image on the screen. Have you ever seen a video of a TV screen on TV? Notice how it flickers? That's interlacing. The screen renders half the image at a time - faster than your eye can see, but not fast enough to fool a camera. Old style PC monitors have a setting called "refresh rate" which fiddles with the speed at which the screen interlaces. The higher the refresh rate, the less likely you will notice any flickering while the screen draws each half of the image. On the other hand, if you take a video or a still picture of a progressive screen, you will always see the entire thing, no flickering whatsoever. That's because the display draws the entire image and it doesn't have to refresh 24 or 30 times a second, instead the display merely needs to keep up with changes in the image (this is not refresh rate, but response time). It looks more stable than an interlaced image.

All right, i/p lesson complete. So: DVD was introduced the mid 1990s, with the intent of offering a good storage medium for computer files as well as a better video source than VHS. VHS plays an analog image at 330 x 480, for a total of 158,400 pixels on the screen. This is sort of a pseudo-480i image - it doesn't offer the full horizontal resolution. DVD, on the other hand, is encoded digitally at 720 x 480, for a total of 345,600 pixels. As anyone could plainly see, even on an old television, DVD offered a picture which was twice as sharp at VHS. All was good. We were all in video nirvana.

But then, TV got better. High definition televisions, or those capable of displaying 720p and up, hit the market. Programming was sparse at first, but eventually networks and PBS stations began offering programs recorded and encoded at 720p and even 1080i (but not p) over the air. Just as the comparison between VHS and DVD, seeing the difference between an image at 345,600 vs. one at 2,073,600 pixels was pretty glaring. Things look "real" at the much higher resolutions. We want THAT for our movies!

So, enterprising DVD player manufacturers set to work on adapting the most successful video format ever (DVD) to these new sets. Well, heck, if you can just show the 480p disc at 720p or 1080p resolutions, it will look better, right?

Well, no. Imagine that the 480p image is composed of 480 lines alternating between red and blue (forget for the moment why you would wish to watch such an image!). If you "upconverted" that image to 960p, what would you have? You'd have an image full of lines which are two pixels wide instead of one pixel wide. You are not seeing any more detail. There are still and always only 480 lines.

But remember that digital displays such as LCD monitors display everything at their native resolution, whatever it is. Many LCD screens used for home theater viewing, for instance, display at 1366 x 768. That's 1,049,088 pixels. Woo hoo! That's more detailed than DVD, right? Sure, if you feed it a signal that has more detail that DVD. But if you pop in a DVD, you will still see that same image of 480 alternating lines. They'll just be 1.6 pixels wide instead of 1 pixel wide... uh, oh... what happens when you "upconvert" an image to a resolution which doesn't neatly correspond to a multiple of the original image?

This is where the wonderful world of "scaling" comes in. 2 pixels can't display 1.6 pixels worth of information. They can display 0, 1, or 2 pixels. Those are the only options. It's like a Lite-Brite. There are only so many holes to punch those pegs into, see? So the scaler needs to do what your childhood brain does when you try to render a picture into a Lite-Brite: decide which lines can be lost and which ones can be stretched to average out into a picture which looks just as real to your brain as the original. (Of course, Lite-Brite pictures never look that real... but that's just because the resolution is so crappy! ;-) It involves lots of math and circuitboards, but essentially, your 720p LCD screen scales the 480p image from a DVD to fit the resolution of the screen., deciding which lines to add and lose to aberage out into a picture which looks to your brain identical to the 480p image.

But you only get what you pay for, right? Some scalers are better than others. Usually, though not always, the more expensive the TV you bought, the better scaler it has on board. Some TVs present a picture which seems to be swimming with jagged lines or "shimmering" - because it is making poor choices of which lines to add or drop. Better TVs make better choices, presenting you with a smooth, uniform image that delivers on detail but doesn't swim with extra noise.

THIS IS WHAT AN "UPSCALING" DVD PLAYER CAN DO FOR YOU. If you have a cheaper TV, it may well be that a DVD player with its own scaler will do a better job converting a 480p dvd image into a 720p or 1080p one. It will not ADD detail to an image. It will REDUCE unwanted "false information" from the image. It will make better choices as far as which lines to add or drop when converting the image. ALL TELEVISIONS AT 720P OR ABOVE "UPSCALE" OR "UPCONVERT" EVERY IMAGE FED INTO THEM. You do not need a new DVD player to do this. The question is simply whether a DVD player can do it better than your TV.

High definition images have 921,600 or 2,073,600 pixels in them. People who claim that they get an image which looks "just as good as HD" from a disc which has 345,600 pixels worth of information are either grossly misinformed, legally blind, or lying through their teeth.

The last option, for instance: during the whole Blu-Ray vs. HD-DVD imbroglio, "upconverting" was being sold to the average consumer as a good alternative to upgrading to a new format. Oddly enough, most of these recommendations were being proselytized by the HD-DVD camp, in an effort to prevent people from buying Blu-Ray players, and likely in an attempt to get them to avoid HD disc adoption altogether, in preference for future digital download formats. Turns out, Microsoft was behind the "proselytizing effort," and its notoriously soft support for HD-DVD was seen by many (including me) as an attempt to prolong the format war, weakening both formats in advance of its own digital downloads.

Another thing to realize in the claim "just as good as HD"... just as good as WHAT high definiton? The cable going into your TV is capable of relaying a certain maximum amount of information. Which do you think has more information - an image with 345,600 pixels, or an image with 921,600 pixels? That's right, the higher one. So if you decide that of your 100 channels, you're going to switch 50 of them to 921,600 pixels, what are you left with? A bandwidth crunch. The coaxial cable can only push through a certain amount of data. When you reach that physical limit, something has to give. Some times, it's going to be that standard definition channels - heck, since they didn't look that good anyway, who cares if they look a teeny bit worse? Let's just send an image at VHS resolution, 158,400 pixels. Great! But the bandwidth savings there aren't as big as the savings in reducing the quality of high definition signals... what if you were to compress a 2,073,600 pixel signal down to, say, 800,000 pixels? That's a big savings in bandwidth. And it still looks "better" than a 345,600 pixel image, so great, everyone's happy. Most consumers won't be able to tell the difference, right?

Except we can, if we have the facts, and we have things to compare the crappy, compressed-to-shit images on cable services like Comcast and DirecTV to. Like Blu-Ray. Blu-Ray discs have a lot of storage space, and connections with precisely the amount of bandwidth necessary to display a 1080p image in perfect clarity and detail.

Look, I own an "upconverting" player, the Oppo DV971H. I think it's a fantastic player, and I do indeed have it set to scale from 480p to 1080i. Why? Because I think its onboard scaler does a slightly better job than the scaler in my Sony SXRD set. But I don't think that a DVD on it, let's say "The Prestige," looks better than a Blu-Ray of the same movie played on my Playstation 3. I've compared the two side by side (much to my girlfriend's chagrin...). There's a difference. It's not "near" anything. It's as good as a DVD will look on my setup, and I'm glad for it. But the Blu-Ray is WAY clearer and sharper, and has deeper colors, better blacks, and punchier sound to boot.

So please, please, please... don't go around saying that your "upconverting" player gives you a "near-HD" image. What your upconverting player is doing instead is giving you a near-480p image! If you had a 720x480 digital display, and a player which mapped the disc pixel to pixel, you'd have the best possible image from your DVD. But there are only ever 345,600 pixels of information. Blowing than number of pixels up to 2,073,600 does not increase the amount of information - indeed, it may end up losing information because of inadequate scaling from one size to another, since the multiple of the size is not a round number. An "upscaler" might blow the image up better than your TV, it might not. But the best it can possibly do is render the image in all its 480p glory and clarity. It will never look 720p, 1080p, or any number inbetween. And in all likelihood, it will look less than 480p.


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