Pixel Perfect HD advice needed (1 Viewer)

[Pat Clark]

I'm trying to achieve pixel perfect screens on an HDTV which does not have any sort of "direct" HDMI mode. We surely don't want the computer to scale one way and the TV to rescale the other way.

My assumption is that a graphics system always outputs 1920x1080 pixels if that is what is selected.

But I don't understand what the system does to achieve over- or underscan. I hope it doesn't send more or fewer pixels, or scale an over- or underscanned representation back to 1920x1080. That would make Radeon's CCC overscan setting "impossible" to set correctly.

I also assume an HD LCD TV has exactly 1920x1080 pixels.

Does anybody know how all this works, and what is right or wrong in the above?

Currently, I have CCC's overscan set to an intermediate point where I guessed 0 would be if it was marked, and the TV's width and height set accordingly.

 

[mr viggo]

It was a long time ago I did this on my tv. But if I recall correctly, this was a tricky bit the first time. Try google for "pixel mapping test patterns", they might help you. I've got my CCC overscan set to 15 i think, far most to the right. And the tv has something like "fit to screen" turned on.

 

[Pat Clark]

Thanks. Googling as you suggested, I found a program that generates a 1x1 checker board at full res, among other test patterns. (http://tft.vanity.dk/)

I can see no artifacts. I suppose if I can't see any with that pattern, I won't see any with a normal image.

My TV has no fit to screen mode. It does report a 1920x1080 signal no matter what I do on the PC.

 

[kiwijunglist]

yeah scaling/overscan/underscan scales the picture by shrinking or adding a border, but it doesn't change the output resolution just the picture resolution. To achieve 1:1 pixel mapping (which is what you mean by pixel perfect" you have to set overscan/underscan to 0%, then adjust any TV settings so that you can see the whole picture. On A samsung TV this is called "Just Scan" in the picture settings menu.

Here is the best test pattern

http://www.post76.com/discuss/attachments/forumid_5/0812240919c4060853512dad48.gif

The best way to view the tiger dave test pattern is to set it as the desktop background (as you have to view at 100% zoom for it to actually work.

^ view this 1:1 picture on your desktop PC using your LCD monitor (which I assume has 1:1 mapping, and you will be able to see what the test pattern should look like on your TV with and without 1:1 mapping.

http://upload.wikimedia.org/wikipedia/commons/1/15/Effects_of_overscan_on_fixed-pixel_displays.png

 

[kiwijunglist]

It was a long time ago I did this on my tv. But if I recall correctly, this was a tricky bit the first time. Try google for "pixel mapping test patterns", they might help you. I've got my CCC overscan set to 15 i think, far most to the right. And the tv has something like "fit to screen" turned on.

^ with these settings you definitely are not getting the sharpest picture possible.

 

[mr viggo]

Just checked, I've no over- underscan set in CCC. Slider to the right at 0%. Sammy Tv has "fit to screen" in picture settings to achive 1:1 mapping.

 

[kiwijunglist]

0% is where you want it, unless you have a TV that doesn't support 1:1 mapping, in which case you are forced to adjust the overscan so that you can see the entire picture without the edges being cut off.