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View Full Version : Noise in Windows video output under Boot Camp


Muriac
20th April 2006, 06:03 PM
Ok, I've found a few threads on other forums where people were complaining about this:

When I'm running Windows on my iMac, the whole screen shows random noise on it. The noise is static, both in that it is not animated and in that it is not related to any UI element. Windows move under the static rather than with it. The effect is only in the output: screenshots and any other saved images are not affected.

The effect looks like a random noise saturation overlay with maybe four levels. It is most noticeable in medium grey areas, but can be seen anywhere there is solid colour that is not too bright. The most obvious example I have found is in the Steam client. I thought that Valve had textured it in the last update before I realized my whole screen was showing the static. I might make a mock-up in Photoshop if this description doesn't make sense.

The noise only appears when running Windows natively. It does not appear when using Parallels, even in full-screen mode. Moreover, the noise is exactly the same no matter what resolution I run Windows in. That is, it covers every actual pixel on the screen, even if multiple pixels are being used to display one downsampled "virtual" pixel.

Before you ask: Yes, I have checked and re-checked that I am running in 24-bit colour. I am. I'm sure. The bit depth is there in the control panel, and it is very apparent that all the colours are present on the screen. They are simply covered in light noise. Changing the bit depth to something lower than 24 gives the same effect, but with less colours (as one would expect). Changing it back to 24 does not get rid of the static. This is not a bit depth issue (at least not one that is controlled by the Displays control panel).

Is anyone seeing this? Has anyone found a fix for it? In the other threads I've seen, I haven't encountered anyone who doesn't have the issue. One guy checked five MacBooks, and they all showed the problem. I'd really like to know how to get rid of it.

Edit to add: Just thought I'd mention that I'm running a 17" iMac with (of course) a 128MB ATI X1600. I know this issue occurs on at least some MacBooks, so it would be interesting if it did not occur on 20" iMacs with their 256MB of VRAM.

Jmerkow
20th April 2006, 06:11 PM
Im having the exact same problem with my macbook pro with the x1600 256mb....

Muriac
20th April 2006, 06:35 PM
Good to hear. Well, not good for you, but good for everyone because the more widespread the issue is, the more likely a fix will come.

I did a mock-up, using someone else's Windows screenshot. Here's the original:

http://img54.imageshack.us/img54/6479/steam9pb.th.png (http://img54.imageshack.us/my.php?image=steam9pb.png)

And here's what it would look like on my machine under Boot Camp:

http://img54.imageshack.us/img54/2024/noise3el.th.png (http://img54.imageshack.us/my.php?image=noise3el.png)

Krevnik
20th April 2006, 10:58 PM
It is dithering noise. ATi's video cards have had it for the longest time when running in 16-bit mode. Essentially the problem is that even if you set it to 24/32 bpp mode... the hardware is displaying 16 bpp to the LCD... thus the noise.

Muriac
21st April 2006, 04:06 AM
It is dithering noise. ATi's video cards have had it for the longest time when running in 16-bit mode. Essentially the problem is that even if you set it to 24/32 bpp mode... the hardware is displaying 16 bpp to the LCD... thus the noise.
After playing games for a bit, I think you're absolutely right. So: why in Windows and not in Mac OS (or virtualized Windows)? And how do I get it to display properly in Windows?

Jmerkow
21st April 2006, 02:59 PM
I turned off POWERPLAY and it seems to reduce the noise. its still there but reduced. Not sure exactly why it works but.... whatever.

Muriac
21st April 2006, 06:39 PM
I can't think why that would be. Powerplay is a clockspeed stepping controller. Bit depth shouldn't be related to clockspeed. Are you sure this isn't just an illusion? No offence, just that the dithering should either be there or not be there, rather than anything in between.

Raa
23rd April 2006, 09:21 AM
I too get this issue with my 17" iMac

I noticed it a lot in games, but if you come back to the desktop and set the theme to windows classic and get up close you'll notice it looks dithered/noisy

I'm not happy about this one!!! :(

Krevnik
27th April 2006, 12:45 AM
After playing games for a bit, I think you're absolutely right. So: why in Windows and not in Mac OS (or virtualized Windows)? And how do I get it to display properly in Windows?
The answer is easy: the problem is related to the firmware or drivers (I am willing to guess that it might even be a symptom of the two interacting). OS X does it correctly, and virtualization uses OS X's drivers. Remember, the firmware on the ATi cards are essentially UGA 'beta' builds.

EDIT: Quick update as of 4/30/06. I just picked up a SyncMaster 215TW to use with the MacBook Pro. Well... how about this oddity: The noise went away in Windows XP. I don't see it on the external display, and I don't see it on the built-in display. I will find out tomorrow if this 'fixed' it for good, or just as long as the external display is also hooked up.

Krevnik
1st May 2006, 06:45 PM
Okay, here is the skinny on the noise issue:

It is related to external displays with the X1600, and the MBP/iMac. Something is getting mis-configured between Windows and the ATi drivers when there is no external display attached. The moment you attach an external display, and boot into Windows that way, it works just fine. The noise goes away. Shut down, disconnect the monitor, and reboot, and you will see the noise again.

Personally, I have a feeling it is related to the same bug that makes a 640x480 'display' appear to Windows (the external display), even when there isn't one. This might be confusing Windows into telling the drivers to mis-configure the card, because the drivers are returning poor information.

Because it is driver related, I would love to test this out on Vista and see if the UGA beta drivers resolve the issue. However, I can't go mucking with my MBP and wiping the HD just to test.

Correction: The external display will not exhibit the noise. HOWEVER, the internal display still displays the noise, I just didn't notice it until recently.

slava
23rd July 2006, 01:48 PM
Hi all. I have the same problem on my 17 MBP 2.16Ghz 2G ram. External display does not solve any problems. The funny thing that if you swap displays (23 inch cinema) the noise still there on the secondary (built in) display but works fine on the external. I installed windows several times so far, with omega drivers, catalyst, AtiTray tools, AtiTools, and of course the supplied Ati drivers from the BootCamp CD but the problem always there. If I want to see a bright error free windows display I have to uninstall all Ati drivers. Before you ask why can't use external display only if there's no screen noise..... Well, for some reasons the external display has its own life. Sometimes turns on works fine. Then I restart for some reasons, and there's no way I can make the external to work. Can't even turn it off. But the system detects it's there, so you can move any window to a complete black screen. Going back to OSX wakes the display and make it working fine. Please help to solve this issue. Sorry for my English

betonfoot
21st September 2006, 11:40 AM
Hey, has this issue been solved?? Any new drivers to fix the problem?

OptimismPrime
24th September 2006, 02:49 PM
As can be read on several forums, this issue is supposedly not a firmware/driver issue, but a hardware issue.

The MacBook Pros and 17" iMacs use 18Bit LCD Panles.
That's right, not 24, not 16, but 18.

To display "full" (pseudo-)24Bit Colors, OSX uses temporal dithering, so it changes the pixels color values over time, timed in such a way, that the human eye percieves different colors. So they "emulate" rather then display 24Bit.

The Windows drivers seem to either not know how to do temporal dithering, or do it wrong (or aren't aware they should, if they can).

This is not quite so noticeable in OSX, but it is THERE, if you try and work on greenscreen compositing you'll notice.

So the problem seems to be inferior hardware, hidden by OSX drivertweaks, not present in XP drivers.

This is one of the main reasons i didn't buy a MBP yet.
I realy do need a new OSX Laptop, but one suitable for production purposes....
Maybe in the pending Merom-MBP refresh they'll start using different LCD panels aswell