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Question about 1:1 pixel mapping (1 Viewer)

Glenshaw

Grip
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Nov 13, 2009
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David
Hi. I'm not too experienced when it comes to "home theater," but I have a question about which I can't find straight information.


I currently have a very small (22") widescreen TV, but am looking possibly to upgrade to something newer and larger. When I got a widescreen/flatscreen TV a few years ago, I was under the impression that I'd be getting the "full" image that is on a DVD, unlike a CRT TV where the curve of the screen plus some masking on the edges meant that even with a widescreen film, the edges were still cut off (i.e., "overscan"). What I found after getting it, and from online research, was that, although the wide screen gave me slightly more information on the sides, the overscan was still in place on flatscreen TVs. With a 1.85:1 (or 1.78:1, whatever) film, information on both sides and top and bottom is cut off, while on 2.35:1, the left and right is cut off. This means you're not getting the full widescreen image that is encoded on the DVD/Blu-ray, and it's very apparent when you go to a theater for a film, and the ratio is much more extreme than you're getting at home.


Let me be clear that I'm not desiring that a 2.35:1 film fill my TV screen. I'm well aware of the "black bars"; I just want to get the full image that's on the disc.


I've read about 1:1 pixel mapping (also called "dot for dot", apparently) that is available on many newer TVs as a function that you have to turn on manually. Apparently the result of this is to bring the full input image to your screen, thus bypassing the overscan. However, most comments I've read about it don't seem to reference my concern, which is getting the full image that's on a DVD/Blu-ray when attached via HDMI. These comments mostly talk about the value of the 1:1 to using the screen as a computer monitor, which doesn't concern me. This is my question:


Does 1:1 pixel mapping allow you to view a DVD/Blu-ray in its complete encoded aspect ratio via HDMI, showing you exactly what is on the disc without edge information being cut off?


If so, does this cause a loss in image quality in any way, or does the image become smaller/windowboxed (if so, how much smaller compared to screen size)?


I've read my befuddlement that new TVs would still have overscan, echoed by others. When you watch a disc and it has the aspect ratio listed on it, it seems strange that you're not actually getting that full ratio. Is the 1:1 mapping function the way to get it? Is this function pretty much available on most reputable brands today? Thanks for your input.
 

Worth

Senior HTF Member
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Jul 17, 2009
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Nick Dobbs
Overscan and 1:1 pixel mapping are two different things. 1:1 pixel mapping simply means that the source exactly matches the monitor - so a 1080p blu-ray can be displayed pixel for pixel on a 1080p set. A 720p broadcast signal or a 480p DVD aren't displayed 1:1 on an 1080p set. They need to be upscaled, either in the player or by the TV. Computer monitors aside, I don't think any TV will show a 1:1 image of a lower resolution source by displaying it within a small window.


As for overscan, most, if not all, new TVs can be set up with zero overscan for 720p, 1080i and 1080p sources. There's usually 5% overscan on 480p signals, so if you want to display DVDs with no overscan, you'll need to do the scaling in the player.
 

Glenshaw

Grip
Joined
Nov 13, 2009
Messages
19
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David
Thank you. I was just confused because people usually talk about it in reference to using it as a computer monitor.


Another question -- Do 4K TVs deal with turning off overscan in the same way? Considering that the resolution of your regular BD is not equal to the resolution of a 4K TV, how does that work?
 

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