Anamorphic WS (1 Viewer)

[Eric_R_C]

Okay, here's another question. I thought I had the right answer, but recently saw a post that said otherwise. So, here goes.

Assuming a DVD says that the movie is fullscreen, then the (1.78:1) image is cropped to 1.33:1.
Assuming a DVD says that the movie is letterbox (generic term), then the (1.78:1) image is "shrunk" into a 1.33:1 frame
My question is...
Assuming a DVD says that the movie is "enhanced for widescreen/anamorphic", is the 1.78:1 image "squeezed", or is the image stored in its 1.78:1 form?
Now, I DO know that an anamorphic film means the visual data is squeezed into a 1.33:1 film frame, and that a DVD player must remove scan lines to fit the "anamorphic" picture into a letterbox on a TV (hence being the worst way to watch an anamorphic DVD.)
I ask this because I've read in several places that the term Anamorphic is incorrectly used for DVD's because the image is not "squeezed" onto the DVD, especially since the information is digital (0's and 1's). Now, an anamorphic DVD should contain more visual data (up to 33% more, assuming no compression) than a fullscreen DVD. I guess I should ask, does the area on the DVD that holds this visual data accomodate the data whether it be 1.78:1 or 1.33:1. In other words, does a 1.33:1 movie take up less physical data space on a DVD?
Also, is there a more correct term that should be used instead?
Does this make sense?

 

[Robert Dunnill]

The "lock-in-full" problem is a function of your TV, not the DVD player. (I would go so far as to call it a "design flaw", but I'd probably offend someone. )

I own one of those sets, and I would most definitely call it a problem, one that took nearly $2000 worth of experimenting with players before I had a satisfactory solution (Pentium III home theater computer. :frowning:
RD

 

[Jack Briggs]

Eric:

With current consumer technology, DVD-Video delivers 480 lines of progressive or interlaced video information. One format, 4:3, delivers this information correctly scaled onto a 4:3 screen. The other, 16:9, delivers the same amount of picture information in its proper shape onto a 16:9-shaped screen. One's ability to display this information correctly scaled at full resolution depends on her or his television or monitor—i.e., can it display images at full resolution in a widescreen mode?

Hope this helps.

JB

 

[Eric_R_C]

Jack, I'm afraid not. I'm concerned with how the information is STORED, not how it's displayed. I know the player can manipulate the images and sound (DD 5.1 into DD 2.0 for pro-logic only systems.) An anamorphic image can have up to 33% more resolution than a full screen image. Does this mean a letterboxed image (i.e. in a 4:3 frame) has the least amount of resolution of the 3 formats? I always assumed it did, but I just wanted to verify.
Maybe this is more of a hardware question?

 

[Graeme Clark]

Information is stored as 1's and 0's as you've mentioned.

Does this mean a letterboxed image (i.e. in a 4:3 frame) has the least amount of resolution of the 3 formats?

Yes, because more lines of the picture is black bar than any other, so less lines are of actual picture. You have 480 lines of resolution. If 200 of that is used for black bar, then you've only got 280 left for the actual picture. a 1.78 or 1.33 picture is using the full 480 lines for the picture.

 

[JohnVB]

Vince,

You shouldn't. Some TVs have multiple zoom modes- some zoom in far enough to eliminate bars on 2.35:1 material- in which case they might also crop the sides.

So, if I use zoom1 on a widescreen 1.85:1 movie, I should still see small black bars on top and on bottom of my 16:9 TV, right? If I don't, then either the movie is stretched too tall, or the sides are cropped. Right?

Hm, I think I need to check for black bars next time I do this.

- bones

 

[Michael Reuben]

So, if I use zoom1 on a widescreen 1.85:1 movie, I should still see small black bars on top and on bottom of my 16:9 TV, right?

First of all, you're assuming that everyone here knows what "zoom1" does. There aren't any standard names for zoom modes; consult your TV's manual for a description of what "zoom1" does.

Second, there is very little difference between 1.78:1 and 1.85:1. On most 16:9 TVs the difference will be taken up by overscan, and you won't see any black bars on a 1.85:1 film. This applies whether you're talking about an anamorphic DVD in "full" mode, or a non-anamorphic letterboxed DVD that's been zoomed to fill the width of the screen.

M.

 

[Jack Briggs]

No.

Though you've been answered already on that point, let me give it a whirl. The NTSC standard for Region 1 DVDs is 480 lines of viewable picture information. A DVD mastered at 1.33:1 (4:3) will have the same amount of resolution as one mastered at 1.78:1 (16:9). What is confusing you (I think) is the 4:3-mastered letterboxed DVD; i.e., a widescreen film presented in its OAR but mastered in 4:3. This means more than a third of the picture information on a letterboxed-only DVD is devoted to the black bars, hence a "loss" in active picture resolution.

A so-called "anamorphic" DVD (i.e., 16:9-encoded) will present all its 480 lines of viewable picture information into a 16:9 window.

 

[Keith Helms]

Is this right? If so, couldn't they make anamorphic full screen dvds?

Actually, they COULD do this. Anamorphic just adds pixels horizontally (854x480 instead of 720x480). Normally, they take a 16x9 picture and come up with 854 pixels on each of the scan lines. If they were to take a 4x3 picture and sample it at 854x480, they could then store it on the DVD as anamorphic.

The problem is this would wreak havoc with people's DVD player settings. If they have a 4x3 set, then the DVD player would likely be set to auto-letterbox an anamorphic picture, so the result would have bars at the top and bottom and look flattened. These people would have to go into setup and "lie to the player" that they really have a widescreen TV, just for this particular DVD.

People with widescreen TVs would have the reverse problem. Their player would be set to widescreen output and the 4x3 picture would be stretched out to fill up their 16x9 screen, again looking flattened. They would have to set their TV to 4x3 mode with bars on the sides in order to display an anamorphic 4x3 DVD correctly.

The bottom line is this would cause way too much confusion for the 18% or so increase in horizontal resolution. Maybe somebody with a DVD burner can experiment with this technique, but don't expect to see discs like this in the stores.

 

[Seth Paxton]

Anamorphic is mostly about getting more scan-lines onto the TV.

Still not quite correct. The scan lines on your TV are fixed by the TV itself. We want to have more of those lines devoted to carrying VIDEO rather than black bar image.

Anamorphic is actually quite simple, but it sounds like you need to reset how you think about video displays (TVs).

Let's ignore plasma and LCD sets for now, since they have different methods of displaying video (though still have the resolution contraints like "regular" TVs).

All a display does is draw one line at a time, left to right, starting at the top and ending at the bottom. For non-Hi Def material (meaning for regular NTSC that you know and love) there are 480 lines of video AVAILABLE. Period. NO MATTER WHAT SHAPE YOUR TV IS.

Now the key for you is to think about 2 TVs side by side. Both are the same height (say 18"), but one is wider than the other. If one is a 4x3 ("normal") TV that is 18" high, it is 24" wide. If the other is a 16x9 "widescreen" TV then it is 32" wide and 18" tall.

What does this mean in scan lines? Nothing. Both are 18" tall (and assuming both are showing NTSC regular video with equal overscan) and that 18" is covered by 480 lines of video.

NOW, you have a picture you want to put on these TVs, lets say that this picture is 36" wide when you make it 18" tall. Will that fit on either TV? No.

So you start to shrink it. If you keep the ratio the same then you will get SHORTER as you also reduce width. By the time you get the width down to 32" for the W/S TV you will only have 16" of height. But now the video fits.

However, for the thinner set we need to keep shrinking. All the way down to a width of 24". By the time we get there we only have 12" of height.

Now lets go back to that 18" of 480 lines. If 2" are used on black letterbox bars to fill out the screen then it means we have used 53 lines of the video for painting black on the screen. However, for the other set we end up using 6" on black space on the video to make it fit the screen. That is 160 scan lines, 3 times as many for the 4x3 set as the 16x9 set.


So, someone realized that if the TARGET screen is going to be 16x9 you could avoid wasting as many scan lines on black space. You could paint the picture with more scan lines. The problem? Well, on a 4x3 TV the lines won't scan as wide (you will have the same number of scan lines though), so your picture will appear too thin (or tall if you prefer).

To solve that, the DVD player can be told that the TV is only 4x3 and it will cut down the number of scan lines used for video (and replace them with black lines on the top and bottom) so that the picture looks correct (but with less scan lines of resolution now).


This method is in contrast to if they had made the video so that it would fit correctly on a 4x3 but would then have TOO FEW scan lines to look correct on a 16x9 TV. This method is the non-anamorphic method that used to be more common (and was used with LD and VHS).


The difference is that the DVD player cannot add REAL scan lines to the picture to make if fit the TV (nor can the TV). When the DVD player or TV use a ZOOM method they FAKE the new lines from the ones on the DVD.

So in this system NEITHER TV will ever have as many true original scan lines of video in comparison to an anamorphic video source. If you go anamporphic the 4x3 TV still ends up with the SAME number of lines (after the player removes some of them) as with a non-anamorphic picture. BUT the 16x9 TV has more original lines and the picture fits without having to be zoomed.

It has almost nothing to do with the film's original aspect ratio, except for the fact that if the film is no wider than a 4x3 TV in the first place (like Casablanca) then both TVs will be able to fit the film on the screen using ALL THE SCAN LINES (the 16x9 can be told to only scan across part of the screen so that the picture looks correct).

Any film wider than 4x3 but not wider than 16x9 will use all the scan lines of a 16x9 TV, but not a 4x3 TV. Wider than 16x9 and BOTH will have SOME lines scaning black, but less on the 16x9 set.

From that, you can see when you would and would not need to go anamorphic. You only make the video anamorphic if it would allow a 16x9 set to use more scan lines than if it was not anamporphic (as in, any time the aspect ratio is wider than 4x3).


How many "bits" are used to sample these scan lines and encode the information digitally on a DVD (or hard drive, etc) have nothing to do with anamorphic (except that video lines will tend to require more bits to represent them than flat black lines will, so an anamorphic picture will require more storage space in the end).


Always think of your screen as lines being drawn across it.

With that in mind you can imagine why people are interested in High Definition (ATSC) which can have up to 1080 scan lines instead of 480. That's more than twice the resolution from the top to the bottom of the picture.


Incidentally, the horizontal resolution of a TV is a bit more complex, especially with CRTs (you standard TV or CPU monitor). No need to go into that now. You should know that the amount of resolution does vary from set to set based on quality, among other things. Obviously wider sets should have a greater number of "pixel width", but that doesn't always mean that per inch you are able to show more detail.

And technically you don't add pixel width to make an anamorphic video. Laserdiscs, for example, were starting to mess with anamorphic video, yet LD is a NON-DIGITAL video format. There are analog video signals encoded on the LD, not pixel samples. So "adding pixels" has no meaning in that case. You just had more scan lines devoted to video.

 

[Seth Paxton]

PS, OVERSCAN is when the TV manufacturer chooses to not show all 480 lines on the screen.

WHY? Well, mostly for timing issues. The limits of deflection power (the moving of the line across and down the screen) can mean that a TV just can't scan that many lines over that great a distance in the time it needs to (total screen coverage needs to occur every 1/30th of a second).

So how FAST you can move your beam, primarily when it is OFF (not scanning), can cause problems. Think about the big jumps that must occur. You are going from left to right, la di da. Then you get to the end. Now you have to go hell bent all the way back across to start scanning again. Even worse, you get to the bottom and now you are ready to start scanning the top of the next picture.

Picture a teloscope scanning the sky slowly, but then when it reaches the bottom it has to suddenly be back pointing high in the sky. You can only move that sucker as fast as the motors can handle. So if you have X amount of time to move back to the top, you simply CAN'T scan any farther away from the top than you can get back to at top speed in X time.

So a TV can choose not to show a couple of scan lines in order to use the time of those scan lines to help get the beam aimed back to the top. You do that by putting those lines "off" the screen (overscanned). You might have 5% overscan (24 lines) that won't appear on your screen. The TV will use the time of those 24 lines to get back to the top, basically "giving up" on showing them so that instead it can haul ass to where it needs to be next.

The "motors" for a TV beam have to do with changing magnetic fields, the ICs that do this, and the amount of power available to adjust the fields. Each TV has its limits of power based on a number of design issues. Thus, not every "motor" is equal and some sets must overscan more than others.

Also, TV makers like the "clean" look of not showing the first or last lines or so, for various reasons.

 

[Damin J Toell]

Actually, they COULD do this. Anamorphic just adds pixels horizontally (854x480 instead of 720x480).

Nope. The resolution stays at 720x480. The frame size is always natively 4x3. Anamorphic doesn't add any resolution, it just distorts the 16x9 image so that it fills the vertical resolution of the 720x480 frame. When played back on 16x9 sets, this distortion is accounted for by stretching the image horizontally, bringing it back to its proper geometry. 4x3 sets maintain proper geometry by eliminating every 5th scan line. Either way, simply put, anamorphic NTSC DVDs are still only 720x480. 16x9 is the display AR for them, but they are still encoded as 4x3. If you were to display an anamorphic DVD on a 4x3 set with the player set to output a 16x9 signal (which many people do, although usually unintentionally), you would see the entire 720x480 frame in its native (distorted) format; there is no extra resolution.

And please refer to my first post in this thread as to why "anamorphic 4x3" results in a loss of resolution.

DJ

 

[Eric_R_C]

Okay, this is beginning to help me.

Laserdiscs, for example, were starting to mess with anamorphic video, yet LD is a NON-DIGITAL video format

I had forgotten this, but it makes it even harder for me to conceptualize the storage of the video image.

Okay, here's my problem now. Say that I have 2 TVs, a 4:3 and a 16:9. If I play a DVD in 16:9 mode on BOTH TV's, is there a difference in resolution? Am I confusing the resolution of the display device with the resolution of the visual image?
The 4:3 image will be squeezed (distorted), but the whole image will be onscreen. Does that mean the "pixels" of the image are smaller relative to the "pixels" of the 4:3 TV than they would be on the 16:9? Following this line of reasoning on the 16:9, are the pixels of the image the same size as the pixels of the TV?
I know there are 480 scan lines vertically. What is confusing me is the horizontal resolution. How does the full anamorphic picture get squeezed onto the full 4:3 display, without losing horizontal lines (as is done when the DVD player removes lines to letterbox an anamorphic image onto a 4:3 screen?)
I hope I worded my dilemma better this time.

 

[JohnVB]

Seth,
I get it. I mis-spoke. What I should have written is:
"it's about getting more scanlines devoted to the picture rather than on black bars."
Now that I understand the anamorphic format, it's deceptively simple. The image is squished horizontally just the right amount, so when it's stretched across a 16x9 TV, it looks just right. This provides better picture resolution as opposed to using a zoom feature - which can pixilate more. And they've also figured out how to munge the image so it looks right on 4:3 TVs too.
On the overscan topic.Isn't overscan also done left to right as well so the first and last few "columns" are also not shown?
I thought this was done partly becuase people used to complain that the picture wasn't on "all of the screen" - that they had "black bars" on top, bottom, left and right sides of the screen. Oh wait, what do I mean, 'used to'? I guess people still complain about black bars :rolleyes.
This is not a problem on the computer. In fact most people would be upset if there was overscan on the computer, becuase part of the image would be lost off the screen. Imagine trying to do tech support for computer screens that have overscan .
- bones

 

[JohnVB]

Eric,

I don't believe there are any more "pixels" in a scan line on a 16:9 TV than there are on 4:3 TV. So on the medium, 30 frames more or less take up the same space no matter the format.

What matters more for frame size is the complexity of the image which influences how much compression can be done while still looking good. Black bars, for example, are about as simple you can get, so the space to compress and encode the black bars is pretty small.

Someone pipe in if I'm wrong here.

- bones

 

[Eric_R_C]

But I'm concerned with 1 single frame (interlaced or progressive, I don't think that makes a difference, as there are stil 480 scan lines), NOT the number of frames per second.

 

[JohnVB]

Michael,

Vince mentioned some TVs do have 2 zoom modes. In order to avoid confusion, I wanted to specify the zoom mode to which I was referring. I wanted to describe the zoom mode for the 1.85:1 format and didn't have a better name for it at the time. I figured people would figure it out from the context. I guess I seemed to have just created more confusion in the end.

Sorry. :b

Thanks for the info on the overscan. I thought I'd seen bars on 1.85 anamorphic movies on my TV and figured the zoom mode would give the same appearance. Maybe I don't have that many 1.85 movies and I'm misremembering. I'm going to have to go check this out now.

Cheers,

- bones

 

[JohnVB]

Eric,

Is your post addressed to me?

If so, I'm not sure I understand. I wasn't talking about frames per second. I was talking about how much space is used in 30 frames.

I believe mpeg video stores, in the current frame, differences from the previous frame as part of one of its many compression algorithms. So I don't know if it makes sense to single out a frame and ask how much space that one takes. I believe It takes up a certain amount of space based on the context of the previous frame. So, if you moved that single frame, it will take up a different amount of space.

What I am saying is the amount space taken for a video track is dependent upon the complexity of the images and the amount of compressiont that is applied. I don't believe the format of the film (letterbox, fullscreen, widescreen, anamorphic, etc) directly controls how much space is used. However, the format may indirectly control how much space the track uses by changing the overall complexity of the images.

- bones

 

[Graeme Clark]

What is confusing me is the horizontal resolution. How does the full anamorphic picture get squeezed onto the full 4:3 display, without losing horizontal lines

Open up an image on your computer (say it's 64x480 resolution). Now use the controls on your monitor to compress the screen (in any direction, it doesn't really matter). The number of pixels on the screen are exactly the same, the source image is still 640x480, but the image is now distorted. The pixels haven't been lost, just compressed. A pixel is not a measurement, it's just a dot on the screen and doesn't nessesarily have to be a square. Again, the apect ratio of the image is depends entirely on the display device. In simple math, 640x480 is equal to a 4x3 image. But that is only true if those 300,000+ pizels are square. When you changed your montitor setting, the was no longer true.

We could make 16x9 VHS tapes just as easily as we make 16x9 DVDs. This isn't done though because the majority of people have 4x3 TV's and a VCR cannot convert the 16x9 image to 4x3 like a DVD player can.

God, I'm sure I'm just confusing even more now. You just have to get your head around the fact that video source doesn't actually have a set aspect ratio, but is all dependant on the source used for the video and the display device showing the image at is proper proportions.

 

[Vince Maskeeper]

Where in the world to be people come up with this stuff? Did you actually misread something somewhere- or just make this up on the fly?

Both 4:3 and anamorphic DVD have the exact same number of active pixels- it's just the mindset of how those pixels are displayed that it in question.

DVD does not support at 854x480 resolution.

-Vince