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View Full Version : nvidia GeForce 6600GT, can I tweak it?


LogicDeLuxe
24th December 2005, 01:44
I just installed a Gigabyte graphics board with that chipset which I actually got for gaming, though I noticed its video input connector and I tried it immediately.
The picture quality is much better than that of my BT878 board.
My problem is, I have those black bars on the sides, even on sources that I'm sure they go into the overscan of a 720 resolution. Also, the picture is set a few lines too high, ie. the top lines are cropped and at the bottom has a few black lines.
Is there a tool like the BT-tweaker, or maybe a better driver which has the options for tweaking such things?

setarip_old
24th December 2005, 02:18
Hi!

I believe you should have some board-specific tools available from the system tray...

LogicDeLuxe
24th December 2005, 11:23
I believe you should have some board-specific tools available from the system tray...There are many output settings, but nothing for video input.
The input functionality is not in the standard driver. There is a separate WDM driver you have to install after the standard driver.
Also there is only the basic setup in the device properties like TV norm and contrast etc..

Qjimbo
25th December 2005, 00:04
Have you tried it with DScaler? Though if you want to capture stuff with it I know thats not an ideal fix.

LogicDeLuxe
25th December 2005, 23:17
Now I did an accurate comparision. The main advantage of the BT878 board is that it doesn't care about macrovision. The picture quality, especially the signal to noise ratio is much supperior with the GeForce board.

Mainly, I did that comparision in order to find out what's wrong.
It turned out that the driver defaults for the pixel clock is slightly too high and was off about 16 pixels at the right, hence cutting the image there. That was the reason it seemed like it captured a wider overscan which actually wasn't the case.

Interestingly, also my DVD player (an old SEG) is not perfectly accurate as it seems to shift the entire picture downwards by 2 lines, compared with the BT878 capture, which is perfectly centered vertically, as the WSS line on top and the last half line at the bottom can proof.

The GeForece seems to have a perfect pixel clock at 720 which matches my DVD player. I was right about the shifting, which is exactly 4 pixels up and about 6.5 pixels to the right. After shift correction, there are 4 pixels missing at the top and still about 16 pixels missing at the right (where 7 of them belong to the active image). That makes 4 lines and 7 columns not captures at a full resolution at 720x576. I don't really care about the overscan, although I want all 702 colums which are defined as part of the active image.

However, maybe the DVD player is off by some horizontal pixels as well. As neither the capture drivers nor my DVD player is trustworthy, I can't be sure. How can I find out?

I was also amazed how different the notch filters for the color carrier could be with CVBS sources. The BT878 does a lot color noise near the carrier frequency, while in the GeForce capture is non at all, though it seems to produce slightly stonger ghosting which are completely absent in the S-Video capture.

There is another little drawback with the GeForce: The PAL system isn't properly implemented. A PAL decoder is supposed to sum up the current line with the previous one in order to ensure color stability. The GeForce apparently does not, as you can see on the horinzontal stripes on colored parts. This can be easily fixed in post processing, that it, actually converting to YV12 does the trick.

There is only a CVBS shoot for my BT878, since it has no S-Video connector.

BT878 CVBS source (http://www.gratissaugen.de/files/bt878_cvbs.png)
GeForce 6600 GT CVBS source (http://www.gratissaugen.de/files/6600gt_cvbs.png)
GeForce 6600 GT S-Video source (http://www.gratissaugen.de/files/6600gt_s-video.png)
And for comparision:
Original image from VOB, captured with VirtualDubMod (http://www.gratissaugen.de/files/original.png)

I'll also try it with Dscaler.