X1800XT and 1366x768 resolution through DVI?

M

Miksu

Regular
I'm planning on buying a new LCD TV and connecting my computer to it. But after some reading it seems that it's impossible to get Ati cards to output 1366x768 resolution through DVI, even when TV's EDID includes this resolution. Is this correct?

I have X1800XT currently up and running and wouldn't like to buy a new card just for this. How about if I connect my card to TV via VGA? Would this resolve the problem? I suppose I'm going to lose HDCP if I do that, but that shouldn't be a problem at this point. Is image quality worse if VGA is used?

Thanks for replies.
 
Heh, I almost asked that myself. New TV coming this or next week, same situation. But I don't see a reason why it shouldn't work.
 
At the avsforums this seems to be what people are saying: "the ATI's don't support 1366. They only support multiples of 8 in resolutions over both VGA and DVI." And then there were some talk that VGA doesn't have the same limitation. Go figure.

Finnish forum dvdplaza.com also has a FAQ about HTPCs and it states that you can't get 1366 work with Radeons.
 
One thing to consider is will the TV accept it's native res over HDMI/ DVI, many TVs (more specifically LCD and Plasma) only accept HDTV resolutions (720p, 1080i and 1080p) over HDMI.

Also some TVs (again LCD and Plasma) automatially simulate overscan on HDMI inputs thus making it very difficult to achive 1:1 pixel mapping.
 
Bouncing Zabaglione Bros. said:
Don't they pretty much all do some kind of post-processing? So you're never going to get the same pixels you output from the card.
Click to expand...

Hmh, don't know about post-processing but pixelperfect seems to be the thing people are after at HTPC-forums. Meaning no scaling is done.

Found couple test pictures. This is what I'm after: http://www.marky.com/misc/testpatterns/Digital_TestPattern_ByMark.gif

This is what I'll get if the image isn't "pixelperfect": http://www.marky.com/misc/testpatterns/Digital_TestPattern_ByMark_TRACKING-ADJUST-NEEDED.gif
 
Miksu said:
Hmh, don't know about post-processing but pixelperfect seems to be the thing people are after at HTPC-forums. Meaning no scaling is done.

Found couple test pictures. This is what I'm after: http://www.marky.com/misc/testpatterns/Digital_TestPattern_ByMark.gif

This is what I'll get if the image isn't "pixelperfect": http://www.marky.com/misc/testpatterns/Digital_TestPattern_ByMark_TRACKING-ADJUST-NEEDED.gif
Click to expand...

That's not what happens at the high end. You use the output (like a DVD player) as a transport to a dedicated scaler and scale the picture that way (as dedicated scalers are better than what you find in most TV's or players). The reason people are doing this is because DVD's are a lower res than most HD TVs anyway, so will always have to be scaled unless you want a tiny picture in the middle of a black screen.

Even if you're using it for DivX/Xvid replay, unless you have a HD source (from which it will probably have to be downscaled anyway) they will have come from SD DVDs and not be the same as the source. If it came from a HD broadcast, they will have been post processed too.

As far as I understand it, I can't see how you're ever going to get a pixels that haven't been messed about with one way or another.
 
Miksu said:
Hmhm, you seem to know quite much about these and I'm a newbie on the subject, so it's quite hard for me to explain anything :)

Maybe this brief article explains better what I mean with "pixelperfect": http://www.eirikso.com/2006/04/06/perfect-adjustment-of-your-lcd/
Click to expand...

Well I suppose it depends what you're going to use your display for, and the quality of your scaler. There's a lot of poor scalers out there, even in some pretty expensive displays. For display of a GUI, I can see that you would ideally want a 1:1 duplication, especially if your scaler isn't very good.

For movies, the requirements are slightly different, and you want some kind of scaling somewhere along the chain in order to get your SD DVD up to the resolution of your display.
 
Bouncing Zabaglione Bros. said:
Well I suppose it depends what you're going to use your display for, and the quality of your scaler. There's a lot of poor scalers out there, even in some pretty expensive displays. For display of a GUI, I can see that you would ideally want a 1:1 duplication, especially if your scaler isn't very good.

For movies, the requirements are slightly different, and you want some kind of scaling somewhere along the chain in order to get your SD DVD up to the resolution of your display.
Click to expand...

Aye aye, computer will be used as a HTPC but propably some gaming and surfing is done with it so 1:1 duplication would be ideal. When playing DVDs, I'm planning on using ffdshow to scale the picture.
 
A couple of points that may, or may not be useful.

First off, not all scalers scale all the time. If there is only a small difference in resolution between the output and the native resolution then the devce may choose not to bother as all. The Dell 3007 30" panel, for instance, doesn't even bother scaling the difference from a 2048x1536 res to its native 2560x1600 resolution, preferring instead to black border some of it.

Second. I also recentlybought myself a cheap LCD HDTV when coming over to Canada to hook up to the laptop to watch movies and play the 360 with. This also has some funky resolution like 1366, however the VGA recognises a maximum resolution of only 1280 for the panel, the TV doesn't report any larger resolutions. Whe connecting it to the laptop I'd also be buggered if I culd get it set to an HDTV resolution - it would either go to 1280x1024 or 1024x768, screwing the aspect ratio. I read on one forum that using Powersctrip allows you to add resolutions with LCD TV timings/refresh, and viola that worked. 1280x720 now get enabled, but only when pstrip is running. This is with a few years older laptop, not with ATI graphics though, so I don't know if an X1800 would recognise the refreshes straight off.
 
Okeydokey, thanks for answers.

I'm going to pick the TV from local shop in few hours so I can report back later today.
 
As I understand it, hardly anyLCD TV's quote compatibility with 1:1 pixel mapping via VGA or DVI, but almost all can be forced via powerstrip.
 
i now one thing, my Samsung could only accept 1080i or 720p over DVI. nomatter what i tried i couldnt get him accept 1368x768 (or whatever the exact res was..)
trough vga no problem (this was tested on my GF6800 )
 
..playing live for speed right now at 1360x768 with 9800pro through DVI to my HDTV LG 32LX2r

im having 1:1 mapping. The card reads the Tv information just fine.

1on1mapping32lx2rwj1.jpg

1on1mapping32lx2r2sq9.jpg

http://img219.imageshack.us/img219/2772/1on1mapping32lx2r5fk7.jpg
http://img219.imageshack.us/img219/407/1on1mapping32lx2r6jg0.jpg

the tv res is 1366x768, DVI only see's 1360x768, but my TV DOES NOT strech the image to fit those extra 6 pixels, so its perfect :)
 
Last edited by a moderator:
Miksu said:
At the avsforums this seems to be what people are saying: "the ATI's don't support 1366. They only support multiples of 8 in resolutions over both VGA and DVI." And then there were some talk that VGA doesn't have the same limitation. Go figure.
Click to expand...
It is just the horizontal resolution that has to be a multiple of 8, at least on my x800xt-pe is limited like that over VGA anyway, and that goes for my 6800gt as well. I can add 1366x768 as a custom resolution in the Nvidia drivers, but the signal is still 1360 active horizontal pixels wide. So with the picture position/size controls on my display I can adjust that signal to fill the screen, but many TVs don't offer such controls and have to be worked around though powerstrip. Many TVs even automatically under-scan the picture on various inputs to avoid junk that comes on the edges of poor edits and if your display doesn't offer position/size controls then that also requires turning to PowerStrip to correct.

And beyond that is what hey69 mentioned, most TV's only accept your basic 480i/480p/720p/1080i over digital inputs, or at least not much more. That something you can't work past with PowerStirp or anything else, and it is exactly why I stick to VGA with my display. For gaming, render as high a custom resolution as will run well is of far more benift than avoiding the digital-analog-digital conversion inherent to using VGA.
 
Last edited by a moderator:
dskneo said:
..playing live for speed right now at 1360x768 with 9800pro through DVI to my HDTV LG 32LX2r

the tv res is 1366x768, DVI only see's 1360x768, but my TV DOES NOT strech the image to fit those extra 6 pixels, so its perfect :)
Click to expand...

I'm gonna have to mess with my LG LCD a bit more, because I had zero luck getting anything but 720p/1080i to work through the DVI input. 1366x768 does work over the VGA input, and it's pretty close the 1:1, but I'd really prefer to use the DVI connection. But I don't think I tried 1360x768. And I was using an old Radeon 9000, which absolutely sucks for configuring resolutions.

Could also be that my TV is a different model (it's a 37", can't remember the #), so it doesn't handle certain resolutions.
 
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