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Old 08-07-03, 12:47 PM   #49
puterguy
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Here are some interesting new findings to report:

In response to Andy's request for a screenshot, I discovered the following.

Screenshots look perfectly fine and do not show any evidence of the jaggies.

Thinking about it, this makes sense, since the problem is probably not with the actual video bits themselves but with the refresh rate and the way they are converted to DVI signals.

This would explain why the problem only occurs at certain refresh rates (and screen resolutions) and also why the problem only seems to happen under DVI (not analog).

The one perplexing issue is why this seems to effect only some people. My guess is that the reason is one of the following:
-- Different XF86 configurations
-- Different video cards (might be something subtle in the output of the card or could be a bug effecting only some chipsets)
-- Different DVI LCD monitors (maybe some are more sensitive to flakey signals than others)

I *really* would like to solve this having spent almost $1000 on my high end monitor and nVidia card combined.

In any case, a direct screenshot won't reproduce the jaggies. You would probably need to take a picture with a digital camera (which I don't have). Anyone willing to do that and post the pics on this thread?

Thanks,
Jeff

T
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Old 08-07-03, 12:52 PM   #50
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Just upgraded to 4496... still get jaggies unless I force the vertrefresh to 60Hz
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Old 08-07-03, 12:59 PM   #51
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Quote:
Originally posted by puterguy
The one perplexing issue is why this seems to effect only some people. My guess is that the reason is one of the following:
-- Different XF86 configurations
-- Different video cards (might be something subtle in the output of the card or could be a bug effecting only some chipsets)
-- Different DVI LCD monitors (maybe some are more sensitive to flakey signals than others)
Actually, the more I think about it, the more I realize that this *can't* be an LCD monitor problem and is probably not a video card problem (unless some of the broken scaling functions are implemented in hardware). The reason is that the picture looks fine when running video in less than full screen or when running any other type of application (including games like Quake). Also, the fact that the drivers seemed to work OK in earlier versions and that the video works fine if it is the *second* video clip running tends to point more to a driver problem.
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Old 08-07-03, 01:06 PM   #52
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Just wanted to restate some of the interesting facts that should help a good nVidia troubleshooter to narrow down the problem:

1. Problem occurs at 75Hz vertrefresh, but goes away at 60Hz
2. Problem only seems to occur under DVI and not analog
3. Problem also only occurs at certain screen resolutions
4. Problem doesn't occur when watching a video at normal size, but suddenly clicks in when you expand the picture size beyond a (repeatedly) specific size (about 2/3 screen on a 1280x1024 screen)
5. Problem goes away if you have another video running in the background
6. Problem doesn't show up on screenshots
7. Problem doesn't seem to affect games like Quake even at highest resolution.
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Old 08-07-03, 01:08 PM   #53
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Pictures are located here:

http://www.duke.edu/~kcd6/nvidia/


All these pictures are xine using the xv driver.

IMG_0407.JPG is just the xine splash screen in fullscreen.

IMG_0408.JPG is the xine splash screen zoomed in to show the lines better

IMG_0409.JPG is a zoomed in picture of a family guy episode on some guys face. This is from the family guy dvd

IMG_0410.JPG is another family guy dvd picture. It shows the side of the monitor and the jaggies produced there.

Hope this helps,
Kareem
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Old 08-07-03, 01:37 PM   #54
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Thanks Kareemy... those look just like my favorite "jaggies" too!!!

The key thing to note is that the jaggies seem to most effect high contrast edges and lines. This makes things like text look almost unreadable. (I don't know whether such lines are truly affected more or just the jaggies are more noticeable when the horizonatl jaggies intersect such a well-defined vertical line.)

Now when does this get entered as an "official" bug in the driver release information (instead of the usual crap like all known bugs have been fixed)
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Old 08-07-03, 01:57 PM   #55
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its just more noticeable on colours which contrast it, like animation. i can barely tell on badly lit porn, but it might be because my eyesight is so bad :P

... anyway, are those images enough to convince nvdidia there's a problem? i'm sticking to 3123 until this issue is resolved.
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Old 08-09-03, 03:49 PM   #56
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ah, just to add what i wrote before... i notice that with the 3xxx drivers, my tft tells me the refresh rate is 60hx (even theough RANDR tells me its 75). same configuration with any of the latter drivers, and the tft reports 75hz.

was the reason this bug was not evident until the 4xxx releases because the 3xxx series were not correctly ouputting 75hx through dvi?

... if anyone can confirm this please do
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Old 08-17-03, 12:16 AM   #57
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Very interesting finding about the 3.xxx drivers -- this could definitely explain why the old drivers did not seem to have the problem.

Has anyone verified whether a similar problem occurs under Windoze? (and whether one gets a true 75Hz refresh under windoze)

I REALLY WISH THE NVIDIA TECHS MONITORING THIS B-BOARD WOULD PAY SOME ATTENTION TO THIS THREAD!!! It seems to me that combining all of our observations should give the nvidia techs a strong clue about what might be going wrong here.

In fact my cynical mind observes that the only time, nvidia has responded to this problem is when I posted a thread with the provocative subject header "nVidia gets an F for Linux support"...
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Old 08-20-03, 06:21 PM   #58
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Default Samsung 171p scaling problem

I've got a 171p, and I've been having the same trouble as some of you here with full screen video. This problem was present in Windows(looked nasty) and Linux(even nastier) ever since I went to DVI as my interface. I recently upgraded my Windows drivers and went poking through their settings. Turns out that there's a "use adapter scaling/use display scaling" option. Guess what? When I set the option to "use adapter scaling" the problem went away.

I realize that this is really a problem with my display(and others, it seems), but I'm REALLY hoping that there's either a setting already present like this for Linux that I'm not aware of, or that this option can be added to the Linux drivers in the near future. FYI, NVIDIA, my upcoming purchase of a 5900 class board basically hinges on having this option in Linux. Don't make me know the pain of ATI's drivers; I like you guys.

Last edited by rkh; 08-20-03 at 06:33 PM.
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Old 08-20-03, 09:58 PM   #59
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Interesting, but I am not sure I understand why it would be a display problem.

How would the dispaly "know" whether you are watching a movie at fullscreen or not (in fact according to my experimentation the shift to getting the "jaggies" occurs somewhere between 1x and 2x scaling).

Doesn't the DVI display just get a dump of ones-and zeros corresponding to the pixels on the screen some 60-75 times a second (depending on the vertical refresh rate)? How would the display "know" whether you are sending it a moving picture or a still frame or whether you are sending it a 1x or a scaled video image?

To me, it seems like problem must be either in the video card drivers or hardware. Am I missing something?

Also, could anyone else verify whether Windows gives the same "jaggies" problems when showing a full-screen DVD at 75Hz? (also make sure that the video is actually being refreshed at 75Hz)
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Old 08-21-03, 01:08 PM   #60
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Puterguy:

Bear in mind that DVI is a digital interface. There's a protocol involved, and I bet that part of that involves specifing scaling(I'm not going to register with the DDWG to get the spec, can someone confirm this?). I did look up your panel, though, and found this:

http://www.viewsonic.com/pdf/VG171_171b.pdf

The second bulleted item states, "Displays a native resolution of 1280x1024 for incredible detail and clarity[haha] lower resolutions are scaled to full screen using a third-generation processor with variable sharpness control"

I bet that NVIDIA's driver on Linux is opting for the panel scaling by default. Here's a lame review of my screen:

http://www.pcstats.com/articleview.c...id=1046&page=3

I didn't know that scaling was an option that I could turn on and off! When I get home today, I'll give that a try and let you know how I fare.
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