Adjusting for "overscan" on DLP while maintaining 1:1 pixel mapping?

I could swear I had this working properly before. I don't know if a driver update broke it, or what has happened. I have an HTPC with a GTX460 connected to a Mits WD-73736 through a Denon 4311. I need to use the desktop resize to prevent the edges from being lost out in the overscan area. I could swear that doing this before only affected desktop programs, and that video still worked at the full 1080x1920 resolution. But now both TMT and PDVD are using the desktop resolution, so I'm not getting 1:1 pixel mapping.

Is there a trick here that I've forgotten or am overlooking?

I have a GTX460, I don't think the ATI drivers will work very well on it. But yes, in the nvidia control panel, if I set the resolution to 1920x1080 instead of the 1842x1036 resolution that it created when I did the desktop resize, I get proper 1:1 pixel mapping in TMT. But then I lose the edges of my desktop. I THOUGHT that previously with video I had proper 1:1 while in video mode and reduced resolution in the desktop. But now I can't seem to get both working properly without constantly changing the resolution.

But that's the catch... how do I get them to automatically use a different resolution than the desktop? I don't remember having to manually switch the resolution before. I don't need a custom resolution... selecting the standard 1920x1080 resolution produces the correct results for video.

My understanding has always been that these overscan adjustments don't change the actual output to the display... 1842x1036 isn't a valid resolution. They simply cause windows to operate at that desktop size, centered within the real 1920x1080 output. And I thought that previously on my system, video output automatically used the full 1920x1080 dimensions, but now it's using the "fake" 1842x1036 resolution, and scaling the image to fit that.

I really don't think that's true. You think my display supports a 1842x1036 input? Or 1840x1036? Or 1840x1034? Using the desktop resize controls in the video drivers, I can come up with any number of odd resolutions. The TV can only accept a handful of standard resolutions. All you're doing when you adjust this setting is changing the resolution Windows uses internally for the desktop, while the output remains at a standard resolution. Similar to the way some drivers will allow you to set a desktop size larger than the resolution being sent to the display, and panning as the mouse gets to the edge. But in reverse.


Most of the ones I'm aware of do. I don't have a Samsung DLP, bit IIRC, it's a function of some user settings (I think they call it "just scan", or something like that - like I said, I don't have one). With Mitsubishi, you have to go into the service menu and disable geometry correction. Of course, in either case, 1:1 pixel mapping is automatic in 3D mode, as it's necessary in the checkerboard format (and another reason why you want to make sure you aren't messing it up in the PC).

I have it now as long as I leave my desktop resolution at standard 1920x1080. I'm simply trying to see if there's a way to get video output to use the full 1920x1080 when the desktop is set to something smaller. I can do it in Media Center (tell it to use 1920x1080 despite the desktop being set at something smaller), but TMT reverts back to the deskop settings.


Like I said, getting true 1:1 pixel mapping is not an issue. It's easily comfirmable with test video. The issue is simply getting TMT or PDVD to use a resolution other than what Windows reports as the desktop resolution. That is simple with games, as many of them have their own independent resolution settings when not in windowed mode. I just can't find a comparable setting for TMT, unless there's a registry setting for it.

Plenty of people have a lot more. I'm not sure what you're getting at.

I don't follow... my question has nothing to do with my display device, and I'm not talking about any settings in the display. I'm simply trying to see if there's a way to get video output from TMT or PDVD to use full 1920x1080 when in fullscreen mode even if the desktop is set to something less.

I don't see why everyone is trying to make this out as something more complicated than it is.

Then we're on the same page. When you said "The overscan adjustments on the source change the actual resoloution that is being sent to the display" I took that literally. I guess you meant something different than how it sounds.


Sure there is. Without using the resize adjustments in the video drivers (which create these fake resolutions that are less than 1920x1080), things like the task bar, shortcuts to the far left of the screen, the close/minimize controls on maximized apps, etc., are partially or fully off-screen, stuck in the "overscan" area, making them hard to access. You have to try to guess where they are if you want to access them. It's not the end of the world, but it's certainly not ideal. Though I'll take it over compromised video quality.


You HAVE to get 1:1 pixel mapping, or 3D wont't work properly. In the checkerboard format, every other pixel is intended for the "other" eye. If the PC interpolates the 1920x1080 image down to 1842x1036 (or whatever) you lose 1:1 pixel mapping, and the individual pixels might not end up mapped to the correct eye.


But the input signal is still a a standard 1080p signal with 1920x1080 dimensions. The left/right images are separated in the TV, based on a checkerboard pattern. To use a checkerboard analogy, if you take a checkerboard of 8x8 squares, the source sends the entire 8x8 grid as one frame, and the TV breaks out the red squares and black squares, and shows the red squares to the right eye, then shows the black squares to the left eye during the next sub-frame. If I were to resize the desktop to account for the overscan, it would try to scale the 8x8 squares down into something smaller (say 6x6), with a boarder around it that is out of the visible area (in this case, the boarder is 1 square wide). When you scale that 8x8 grid down to 6x6, each individual pixel is no longer where it should be. Some red squares may end up where the TV is expecting a black square, and therefore shown to the left eye instead of the right.

Apparently I'm not communicating this very well. I'll try again: When I use what nvidia calls desktop resize to "fit" the desktop into the visible area of the TV, it creates a new bogus resolution (in my case 1842x1036). When I use TMT or PDVD, they are using this resolution instead of 1920x1080. This is preventing 1:1 pixel mapping, because 1920x1080 is being scaled down to 1842x1036.


I'm not sure what this will tell us that we don't already know: my display has overscan. For the reasons that DanPackMan has already stated. That is something I can't change. Ideally, you deal with it by using the resize functions in the video drivers, but you DON'T want them to come into play during video.

Finally someone who understands. I'm currently using 290.53 (so I guess the same as yours under a different naming convention). This is what I'm not clear of: if this is a driver issue, or a TMT/PDVD issue. Regular desktop software should use the fake resolutions, as that's what keeps it within the visible area. "video" software should be using 1920x1080. I don't know if it's up to TMT to override the desktop resolution and use 1920x1080, or if it's up to the video drivers to recognize that it's a video application, and switch to 1920x1080.

Hmmm, but it looks like you're on the same drivers I am. Do you know you're getting 1:1? If the image is scaled, it won't mess up SBS 3D, only checkerboard (SBS can be scaled and still be SBS). Have you checked with the AVS test video? Though if you're using a projector, I expect you don't have anywhere near as much overscan as I do on my RPTV.

Right, on RP DLP, a significant number of pixels are physically outside of the screen area (in my case, about 78 horizontally, and 44 vertically). I certainly don't expect to get 1920x1080 pixels to fit in the viewable screen area, as that is impossible without being able to make physical changes to the set (which I've actually considered trying, as per here). Even if that is possible, you can't completely eliminate overscan, as a RP set doesn't produce a geometrically perfect picture. Though one day I may try to reduce it.

But that's not what I'm referring to here. What you want is to be able to reduce the size of the desktop (in my case, to 1842x1036) so that Windows elements are not lost to the overscan area. This is done with the resize option in the video drivers, which causes Windows to use a reduced resolution desktop framed within the 1920x1080 output, so that the only thing lost to the overscan area is black border. Obviously a standard 1920x1080 video won't fit into that 1842x1036 space without scaling, so what you want is to revert to normal (unframed) output during video mode. This can be accomplished by manually switching the resolution to 1920x1080 when playing video, and back to the fake 1842x1036 when using the desktop.

I'm trying to figure out how to make this happen automatically. I thought I had it working at one time... perhaps a driver update broke it, perhaps a software update broke it, or perhaps my memory is just bad.

I think the issue you experienced previously was different... To the best of my knowledge, when I switch to the "resized" 1842x1036 resolution, it's not changing the output. I don't have a way to confirm exactly what's being output, but when I switch between 1920x1080 and 1842x1036, there's no new handshake. It seems fairly clear that it is simply changing the size of the desktop within the 1920x1080 output (as it should). It sounds like what you experienced before is your output resolution actually changing. My problem is simply getting TMT to use the full 1920x1080 without having to manually switch it.

True, but if you do that, then it's impossible to get 1:1 pixel mapping. I have specifically disabled geometry correction so I could get 1:1 pixel mapping. So at least I can get it without desktop resizing. I wouldn't even be able to get then if I tried to adjust it out with the TV.