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Old 09-18-07, 09:24 PM   #1
rhreaton
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Default Problem with Overscan

Hi,

I've spent many hours trying to resolve this issue, to no avail. I've searched the web, searched forumes, etc. I contacted vendor support, and they pointed me here. So here goes.

I have an Nvidia FX 5200 connected DVI out to the DVI in port on my RCA D52W20 HDTV. It works great, except that there's too much overscan, and I can't see the edges of the screen. I'm running Knoppmyth R5F27, with the video driver that comes with that distro. I've tried all sorts of modelines modes, options, etc. and nothing seems to make any difference at all. I've tried to use the info from the nvidia bug log, and I can't seem to translate it into a modeline that works. If anyone can help me figure out an xorg.conf config that will work, I would be grateful! I'll attach my nvidia-bug-report.log file.

Thanks!
Rodd
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File Type: log nvidia-bug-report.log (75.1 KB, 129 views)
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Old 09-19-07, 05:41 PM   #2
Tronic
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Default Re: Problem with Overscan

If you use DVI, you need to adjust overscan from the TV, not from the source. DVI just sends image that the display device is supposed to display entirely. Of course, your TV probably doesn't allow you to... Well, **** happens, get a TFT or a plasma next time (I gather that your current TV uses rear projection) :/
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Old 09-20-07, 03:32 AM   #3
pe1chl
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Default Re: Problem with Overscan

Doesn't matter if you get a TFT or Plasma, the problem will be the same.
The issue is that a TV is manufactured according to TV format standards, e.g. SMPTE 274M, and they DO specify an overscan. This has been put in the standards years ago, when a CRT still was the norm and a consumer TV set could not be manufactured accurately enough to fit the scanned image exactly to the picture area. So, the TV is manufactured to omit a small band of picture all around so there is some margin when the picture gets slightly smaller.
(another reason is that transmission in the old days used to be analog, and the TV system could cause some artifacts at the beginning and end of the lines. to hide those from view, a slight overscan is used)

When you want to use a TV set as a computer monitor displaying an entire desktop: too bad. it is not designed for it, and it won't work correctly.
When you want to use the setup to play movies from the PC on the TV: don't worry about it, it is not noticable in normal use and you have the same effect when playing a DVD on your TV on a normal DVD player. Overscan is used in all TV equipment.
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Old 09-20-07, 06:15 AM   #4
rhreaton
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Cool Re: Problem with Overscan

Quote:
Originally Posted by Tronic
If you use DVI, you need to adjust overscan from the TV, not from the source. DVI just sends image that the display device is supposed to display entirely. Of course, your TV probably doesn't allow you to... Well, **** happens, get a TFT or a plasma next time (I gather that your current TV uses rear projection) :/
Thanks for the reply. You are quite right: it is a rear projection. I called RCA support, and it is correct that you can't change the overscan.

Quote:
Originally Posted by pe1chl
Doesn't matter if you get a TFT or Plasma, the problem will be the same.
Next time, I suppose it will have to be a large LCD monitor. For now, I can tweak the video output of MythTV, but I was hoping to use it for other computer stuff as well. Oh well. Thanks for the replies!! This will save me time by not messing around with it any more, and will give me information for my next TV purchase.
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Old 09-23-07, 12:42 PM   #5
DeFKnoL
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Default Re: Problem with Overscan

I have been dealing with this issue as well and only when I came across this thread did I know what to call it; overscaning. Here is my thread;

http://www.nvnews.net/vbulletin/show...ght=Plasma+DVI

Seeing as how this is a hardware incompatibility, I still have questions since the explanation in the other thread does not make sense.

- The VGA input seems to work just fine - I am guessing that this is due to the television using the signal differently than DVI.

- If it is the way the card is sending the signal to the TV, I would guess that using the TV-out from the card would match the TV standard of adjusting the scan lines - but it does not - at least not when I use the composite video out. Would this be a fault of NVidia's TV-Out functionality? Why have it if it doesn't work?

- Is there a way to force the card (card bios) to add the extra space on the edges so i can get my picture? it seems to get worse the higher my resolution goes. When I do 1080i, i can only see the top HALF of my screen!

- If there is not way to force the card to change, is there a way for X to compensate this? I have looked through the documentation and have found nothing for zooming the picture out - only to zoom in.

Has anyone gotten past this?
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Old 09-23-07, 02:08 PM   #6
pe1chl
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Default Re: Problem with Overscan

Seeing only half the picture on DVI is not overscanning. That is a bug in the NVIDIA driver that the NVIDIA people hate to acknowledge. It has something to do with their EDID interpretation.

Overscan is losing a border all around the picture of about 16 pixels, making it difficult to use a TV as a computer monitor because widgets like a taskbar are partly out of vew. That problem is not in the card. It is in the TV.
However, the trouble is that the maker of the TV will not call this a problem; the TV is working according to industrial standards for a TV set.
What you have here is an incompatability between how a TV works and what you expect to get out of a computer monitor. A TV isn't a computer monitor.
Now, when your TV has a VGA input, that could be designed to offer the function of a computer monitor on the TV. And apparently on your TV, it is. On my TV, it isn't. I.e. the same problem occurs when using VGA at 1080i. but it works OK when I send a VESA-standard VGA signal of 1280x1024.
I am still not a happy camper because that is a 4:3 picture that leaves black bars at the side, and I want a fullscreen picture. That is possible, but not without overscan on my TV.

Well, it is OK for watching movies. Aside from the interlace sync problems, that is.
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Old 10-13-07, 10:34 PM   #7
dburdick
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Default Re: Problem with Overscan

Hi,

This all makes perfect sense. I was wondering...why can't the drivers simply compensate for the fact that TVs generally overscan. I understand that it may be a shortcoming of the television, and that perhaps it was never designed to be a computer monitor.

From what I have read in other threads, Windows drivers seem to be able to overcome this issue. I have never tried Windows with my particular television, so I can't vouch for the accuracy of these claims, but others seem successful. *note: no, I am not going to go to Windows. I don't care quite that much.

I simply curious. Is this an impossibility, or is it perhaps a matter of time before NVidia Linux drivers have this capability.
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