VOGONS


First post, by gedbag

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Hi everyone,

I have recently put together a Pentium 3 retro PC equipped with a Diamond Monster 3D II I got off of eBay. Everything seemed to work as intended but I noticed a banding pattern when running games on the Voodoo 2.

At first I assumed this was an issue with my cheap VGA to HDMI adapter (the same issue is present running the card into an Extron RGB HDMI 300 A), but today upon further inspection it seems like the issue is limited to games running at 640x480. Running at 640x480 introduces some vertical banding with different bands going across the image having differences in brightness. There is also severe flicker going on in the affected areas.

What's odd is that 512x384 and 800x600 look perfect and don't have this issue. The passthrough image from the other card (GeForce4 Ti 4400) is also clean at any resolution (including 640x480). Only when the Voodoo itself is rending does the issue crop up.

Anyone know what this could be? Could the card be defective? Any troubleshooting ideas would be greatly appreciated.

Thanks.

Reply 2 of 14, by subhuman@xgtx

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try to set this variable on a batch file before running the game:

SET=SSTV2_VIDEO_24BPP=0

Also try playing around with different gamma values on the V2 Property Sheet.

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tbh9k2-6.png

Reply 3 of 14, by appiah4

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I had a very similar problem (color artifacting in 640x480 that was absent in 800x600) and it turned out to be a bent leg shorting with its neighbor. Don't ask me why or how that can happen, just visually check your card.

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Reply 4 of 14, by maxtherabbit

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The problem is the extremely noisy output of the V2. High frequency noise is shitting on the ADC. I had the exact same problem when trying to digitize a V2 with the RGB HDMI 300. I solved it by adding a low pass filter

Reply 5 of 14, by gedbag

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leileilol wrote on 2021-09-29, 19:56:

Have you tried moving the refresh rate sliders around in the Voodoo2's panel in Display Properties?

I wasn't able to do from the control panel but just tried Voodoo 2 Tweaker which worked. Setting the refresh rate to 75hz makes the banding much finer, like thin horizontal stripes, which is much more pleasing to look at than the wider banding. I wonder if this issue was more widespread but went unnoticed back in the day to to higher refresh rates being more prevalent. The big bands only seem to appear at 60hz.

subhuman@xgtx wrote on 2021-09-29, 20:27:

try to set this variable on a batch file before running the game:

SET=SSTV2_VIDEO_24BPP=0

Also try playing around with different gamma values on the V2 Property Sheet.

This didn't get rid of it but mitigated it somewhat. The banding is less noticable with it on.

appiah4 wrote on 2021-09-29, 22:24:

I had a very similar problem (color artifacting in 640x480 that was absent in 800x600) and it turned out to be a bent leg shorting with its neighbor. Don't ask me why or how that can happen, just visually check your card.

I've checked it and it looks pretty good. There was some dust underneath one of the memory chips which I cleaned up but other than that the chip connections looked good. I also compared capacitors with other cards online and couldn't find anything missing or broken.

https://abload.de/img/img_33711qjjwu.png
https://abload.de/img/img_337210ek8v.png

Maybe someone else is able to spot something?

maxtherabbit wrote on 2021-09-30, 02:02:

The problem is the extremely noisy output of the V2. High frequency noise is shitting on the ADC. I had the exact same problem when trying to digitize a V2 with the RGB HDMI 300. I solved it by adding a low pass filter

That sounds like a good idea, I may give that a go.

I should be getting a capture device tomorrow and will post some examples of the issue. Still would like to know if trying another card would yield better results. Thanks so far everyone!

Reply 6 of 14, by gedbag

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https://youtu.be/Qk0eCpgo6_c

Here is a video I recorded of UT99 running at multiple resolutions. The specific banding issue is visible at 0:17. There is also a lot of fuzziness at 800x600 which you can also see in this video. Do you guys think this is par for the course for a Voodoo 2 or would it make sense to source another card? Thanks again.

Reply 9 of 14, by pixel_workbench

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Was the video recording a direct capture, or off a monitor? I often see vertical banding on a Voodoo1, that is fixed by adjusting the vertical and horizontal clock signal on the monitor. Usually after changing resolution the monitor has to be readjusted for best results.

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Reply 10 of 14, by gedbag

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pixel_workbench wrote on 2021-10-03, 01:59:

Was the video recording a direct capture, or off a monitor? I often see vertical banding on a Voodoo1, that is fixed by adjusting the vertical and horizontal clock signal on the monitor. Usually after changing resolution the monitor has to be readjusted for best results.

It was a direct capture. Sadly I don't have a monitor with VGA input to check.

I was however able to make progress using the Extron RGB HDMI 300 A and now can capture a mostly good looking image. In case someone has these same components and the same issue:

1. Adjust the Total Pixels under "Input Configuration". This should manipulate the width of the banding from very narrow bands to wider ones.
2. Adjust the value until there is no visible banding on screen. It will probably lead to the whole screen looking fuzzy.
3. You should then be able to adjust the phase, moving the fuzziness "off screen".
4. Use the other options to resize and center the image in case it's off center.

There is still some fuzziness but that is to be expected with a Voodoo 2 I guess.

Here is Carmageddon running like this: https://www.twitch.tv/videos/1166218573

I'm still probably going to get a second Voodoo 2 for SLI eventually and will check if it has the same issuse.

Reply 12 of 14, by gedbag

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maxtherabbit wrote on 2021-10-02, 00:04:

yeah that's normal, look for something to low-pass that signal before trying to digitize it

I recently got back to this after acquiring two Voodoo 2s for SLI and they exhibit the same issue. (Was kinda hoping the interleaved signal would maybe hide it a bit, but it only doubled the amount of bands 🤣) Can you give me a pointer in regards to what you used to filter the output? Is there some sort of device that does this?

Thanks!

Reply 13 of 14, by maxtherabbit

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gedbag wrote on 2022-04-08, 15:48:
maxtherabbit wrote on 2021-10-02, 00:04:

yeah that's normal, look for something to low-pass that signal before trying to digitize it

I recently got back to this after acquiring two Voodoo 2s for SLI and they exhibit the same issue. (Was kinda hoping the interleaved signal would maybe hide it a bit, but it only doubled the amount of bands 🤣) Can you give me a pointer in regards to what you used to filter the output? Is there some sort of device that does this?

Thanks!

I designed an inline LPF dongle specifically for the purpose. If you're in the United States I can sell you one, DM if interested

Reply 14 of 14, by gedbag

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maxtherabbit wrote on 2022-04-08, 17:00:
gedbag wrote on 2022-04-08, 15:48:
maxtherabbit wrote on 2021-10-02, 00:04:

yeah that's normal, look for something to low-pass that signal before trying to digitize it

I recently got back to this after acquiring two Voodoo 2s for SLI and they exhibit the same issue. (Was kinda hoping the interleaved signal would maybe hide it a bit, but it only doubled the amount of bands 🤣) Can you give me a pointer in regards to what you used to filter the output? Is there some sort of device that does this?

Thanks!

I designed an inline LPF dongle specifically for the purpose. If you're in the United States I can sell you one, DM if interested

I'd definitely be interested but unfortunately I'm in Germany.