Questions On Anamorphic DVDs
Dear Gary: I have been a longtime subscriber to your magazine. I find the articles and information invaluable. However, your articles on anamorphic DVDs (or enhanced for 16:9) seems rather lacking. I wonder if you could answer some questions for me which may clear things up. I would like to think that I have a high-end system. My processor is a Krell Audio+Video Standard, my projector is a Runco 980 Ultra, and I have a Stewart 80-inch wide 1.3 gain screen. I use the DVDO iScan Plus doubler (and am waiting for a scaler that offers value for money). My loudspeakers are Thiel 7.2s and I have Krell Class A amplification throughout. I have a Sony DVP-S7000 which I will upgrade soon. The questions I have on anamorphic DVDs are as follows: A) Your writing seems to concentrate on the effects of anamorphic DVDs on widescreen (16:9) TVs. Is there any value to having anamorphic DVDs for projection systems like mine? B) You seem to imply that special circuitry is need to “unsqueeze” anamorphic DVDs. I don’t believe the Runco 980 Ultra has this special circuitry so can the Runco be set up to play anamorphic DVDs? If I configure and adjust one of the memories in the Runco 980 Ultra to display a 1:78:1 image correctly, will using this unsqueeze the anamorphic DVD? C) If I set up my DVP-S7000 to output 16:9 instead of 4:3, will it automatically send out the “squeezed” data to all outputs, or will this only come out on the component outputs? (I have to use S-video as the Krell does not have component outputs.) I hope you can shed some light on this mystifying subject or maybe you can include a series of articles that will better explain the processes with anamorphic DVDs. I recall seeing such an article recently but again, it does not seem to help if someone like me is using a front projector.
Foo Suan Pin
Video Technical Editor Greg Rogers Comments:
Thanks for your questions. It gives me the opportunity to get up on my soapbox and perform one of my annual rants about the term “anamorphic.” Have patience—I will directly answer your questions before I’m finished. If I were the “Ruler of the Universe,” I would decree that the words “anamorphic,” “unsqueeze,” and “DVD” could never again be used in the same sentence. I believe the only reason this subject is so mystifying is because of the unfortunate terminology that was adopted right after the DVD Big Bang. As the DVD universe began to expand there was chaos over terminology. DVD popularized a new picture format—the 16:9 format. It really wasn’t new, a few LaserDiscs had used the same picture format earlier, and standard-definition 16:9 TVs had been made for several years. No one then, or since, has called them anamorphic TVs. In fact, the 16:9 picture format had already been adopted as the standard for HDTV, even though HDTV broadcasts were still a few years away. Again, no one uses the term anamorphic to describe HDTV. When DVD came along it was caught in the middle, between the old analog TV standard of 4:3 (1.33:1) aspect ratio screens, and the new digital HDTV standard with 16:9 (1.78:1) aspect ratio screens. To make a long story a bit shorter, the rulers of the DVD universe decided they could have it both ways. They decreed that the MPEG data that was stored on the DVD could represent either the older 4:3 shaped picture, or the newer 16:9 shaped picture. What’s important to remember is that there are no images stored on a DVD. It’s not like film. We can’t hold it up to the light and see the pictures. What’s stored on the DVD are just a bunch of 1’s and 0’s. It’s an incredibly long string of data (more than 37 billion 1’s or 0’s per layer) that represent pictures we want to reconstruct and display. The data on the DVD has no inherent shape itself, it just represents the pictures we have when we start making the DVD. Those pictures could have any shape at all, the DVD wouldn’t have to know or care. But because it was decreed, our pictures must either have a 16:9 shape or a 4:3 shape. So suppose we start with pictures that have a 16:9 shape, and then extract all of the information in the picture and turn into a string a 1’s and 0’s. We can then put that string of data on the DVD. Later we can read the data off the DVD and send it to a TV. The TV takes all the data for each picture and distributes it evenly over its entire screen. What shape is our picture now? It’s going to be the same shape as the TV screen. If the picture originally had a 16:9 shape, and the TV screen has a 16:9 shape, then the picture is going to look exactly right. We started with a 16:9 format picture and we got back a 16:9 format picture. And we never once mentioned squeezing or unsqueezing anything. So why does anyone want to call this 16:9 picture format, the “anamorphic” format? Why would anyone say the picture was squeezed on the DVD, and unsqueezed in the TV? Beats me. Suppose we had started instead with a 4:3-shaped picture, and did exactly the same things. Suppose we had turned the picture into exactly the same amount of data and stored that on the DVD in exactly the same way. Then we read it off the DVD exactly as before, and sent it to a TV. Then the TV distributed it evenly over its screen just like before. What shape will this picture be? If this TV screen has a 4:3 shape, then the picture will have a 4:3 shape and look exactly like the original 4:3 picture. Everything is done exactly the same way as before, but this time we got a 4:3 picture simply because we used a 4:3-shaped TV screen. No one wants to call this process anamorphic, or talk about squeezing or unsqueezing the picture. Yet the same process was used to put the picture on the DVD and to take it off. We simply call this the 4:3 format, so why not simply call the first format the 16:9 format? Why does anyone care what we call these formats? For one thing, “anamorphic” confuses people into thinking that special circuits are needed in the DVD player or the TV to unsqueeze the 16:9 pictures. In reality, all we need is a TV with a 16:9 display for pictures that were originally 16:9, and a 4:3 display for pictures that were originally 4:3. All we need to do is just match the shape of the TV display to the shape of the original picture. Now I’ll climb off my soapbox and use what I just covered to answer your questions. Let’s start with question B. Does the Runco IDP980 need some “special circuits” to unsqueeze the 16:9 pictures? Nope. It just needs to project a 16:9 display. You should do exactly as you said and set up a memory to project a 16:9 (1.78:1) aspect ratio picture. Use that memory whenever you watch a DVD that uses the 16:9 picture format. (Yep, it’s still going to say “anamorphic” on the box most of the time.) Question C. Does the Sony DVP-S7000 DVD player output “squeezed” data to all outputs when you put it in the 16:9 mode? Hopefully it’s clear now that it doesn’t put out “squeezed” data in the 16:9 mode. In the 16:9 mode, it just puts out, to all outputs, what was put on the DVD. So if the disc has 16:9 format pictures, you switch your Runco to produce 16:9 pictures. But if the disc has 4:3 format pictures, you switch the Runco to produce 4:3 pictures. The same thing applies for any TV or projector that can produce multiple aspect ratios. Just match the shape of the display to the shape of the picture format on the DVD, and always leave the DVD player in the 16:9 mode. Question A. Is there any value to the 16:9 DVD format when you have a projection system? Absolutely! Because you have a projection system you can make the display any aspect ratio you want. You can project a 4:3 display for DVDs with the 4:3 format, and project a 16:9 display for DVDs with the 16:9 format. Why is that so important? Because you will get more vertical resolution when you display the 16:9 format DVDs on a 16:9 screen, than if you only had a 4:3 screen. That’s going to take a few more paragraphs to explain, and that’s why I saved this question for last. Suppose that you only had a 4:3 screen. What would happen when you played a DVD with the 16:9 format? Remember that the TV just evenly distributes the picture data over its screen. It doesn’t know what the original picture looked like. The original 16:9 picture would fill the boundaries of the 4:3 screen. Everything in the picture would be distorted because the screen shape wouldn’t match the original picture shape. Everything would look too tall, because the 4:3 screen is taller compared to its width than the 16:9 picture was originally. Now you can say the 16:9 picture has been stretched. It wasn’t stretched on the DVD, but the display is just the wrong shape for the original picture. Put the same signals into a 16:9 TV screen and everything looks great. Some of the newer 4:3 TVs have a switch that will change the shape of their display area from 4:3 to 16:9. Part of the screen area at the top and bottom is no longer used, so it works just like it was a 16:9 TV. The incoming picture data is evenly distributed in the 16:9 area of the screen, so 16:9 format DVDs are displayed correctly. Unfortunately, a lot more people have older 4:3 shaped TVs that do not provide the ability to change the shape of the display area. Something had to be done to allow those TVs to correctly display the 16:9 format DVDs. That’s why there is a menu item to tell the DVD player it’s being used with a 4:3 TV. When the DVD player is told that the display has a 4:3 aspect ratio, it knows that DVDs with the 16:9 format will look wrong because the DVD format does not match the screen format. It knows everything will look 33 percent taller than it should. In this mode, the DVD player uses special digital processing to shrink the height of the picture so it will no longer look too tall on a 4:3 screen. All DVD pictures, whether they are 4:3- or 16:9-shaped pictures, have 480 horizontal scan lines from the top of the visible picture to the bottom of the visible picture. The DVD player takes those 480 scan lines and scales them down into 360 scan lines. It then adds back 60 black lines at the top of the picture, and 60 black lines at the bottom of the picture. When it’s done there are still 480 scan lines, otherwise your TV wouldn’t work. When those 480 scan lines are spread out over the height of the 4:3 TV screen, the 360 scan lines in the middle form a 16:9 picture. The original 16:9 picture is properly proportioned once again. Ironically, this is the only time a picture is “squeezed.” Only when a 16:9 format DVD is played back for a 4:3 TV screen, is it “squeezed” (scaled) vertically by the DVD player. Nothing at all happens to 4:3 or 16:9 format data when the DVD player is in the 16:9 mode, yet the popular myth is exactly the opposite. What happens when a picture is scaled from 480 scan lines to occupy just 360 scan lines? Vertical resolution is lost. So if you have a TV with a 16:9 display you will have 33 percent more scan lines in the picture, and therefore more vertical resolution, than if you have a 4:3 screen and the DVD player has to downconvert (scale down) the 16:9 DVD format. So it’s much better to have a 16:9 display for viewing 16:9 format DVDs than to only have a 4:3 display. One final point. What if the DVD producer decides to use the 4:3 picture format, but still has the same 16:9 picture? As we just saw, the picture must be placed within the 4:3 picture frame so that it occupies only 360 of the 480 scan lines. We call this 4:3 letterboxing, and the picture must be viewed on a 4:3 display because the overall picture frame is 4:3. If we want to maintain the same picture width that we use for displaying 16:9 format pictures, the display needs another aspect ratio setting. It needs to produce a 4:3 display of the same width as the 16:9 aspect ratio. If the physical screen is 16:9, the black letterbox bars will be unseen above and below the screen. If the DVD producer had used the 16:9 format, instead of the 4:3 format, all 480 scan lines would have been in the 16:9 picture. Hence, the 16:9 format provides 33 percent more vertical resolution than the 4:3 letterbox format if we have a 16:9 display. Otherwise this additional resolution is lost when the picture is downconverted for a 4:3 display as we saw before.
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