MiSTer FPGA Forum

I've got MiSTer connected to my Sony CRT via VGA -> Component.

Have SOG turned on (otherwise I get rolling image).

Colors initially seem 'right', but in certain instances they seem to have a bit of a red tint, especially in greys.

Here's an example, at the start of Metal Slug on the Neo Geo core, the background is purple
Here's how it looks on the same TV via same component input but from original hardware:
Also seeing simliar issues on the genesis core, here's Castlevania, the ground is purple where it should be more brown:
This is how I'm seeing the test pattern on the main menu, seems to also have a bit of banding ?
Does anyone have any clues/ thoughts ?

Mister's VGA output is limited to 8-bit color. The Component setting further degrades it to 6-bit. Not sure that fully explains the purple shift, but some banding is probably expected at least.

I also have a VGA monitor that can detect SoG. The colors come out slightly different with it on versus off. (Wheras on a monitor that doesn't recognize SoG, you get an enormous green tint from it.) I'm not sure if that is more the monitor's fault or the Mister's.

FoxbatStargazer wrote: ↑Wed Dec 29, 2021 3:24 am Mister's VGA output is limited to 8-bit color. The Component setting further degrades it to 6-bit Not sure that fully explains the purple shift, but some banding is probably expected at least.

Ok thanks for the reply. The banding I’m not so concerned about, just wondered if it pointed to the issue. It’s a shame the mister can’t put out the colors correctly, maybe will need to keep the original consoles around for a bit longer ha.

I am using a scart to component converter for the original hardware. I wonder if I tried going vga -> scart -> scart / component converter -> component , if it would help fix whatever is going wrong in the mister signal.

Does anyone know if there are vga to scart cables that would do the job ?

I doubt very much it's MiSTer's fault, since for most people the colours are displayed correctly - even on CRTs. This might have something to do with the way you connect, or the TV itself - some Trinitrons are known to be sensitive to non-standard signals. I also had a problem with colours: viewtopic.php?f=33&t=614&p=4352#p4352

(this might be something completely different than your problem but is worth checking out, especially the atari-forum link)

I got the exact same problem with a Kit I bought on amazon.ca. My I/O board look a lot like yours with the RGB fan. I wonder if it's not just a defect with bad resistor values. I'm trying to find a reliable way to try HDMI direct video to component without having to mod a cable to put sync on green, but I can't find anything. I'm kind of scared to buy a new I/O board from a more reputable seller, because I'm not sure if this is not just a 6bits vs 8bits DAC symptom or an actual defect.

Another example for me are the first enemy planes in 1942 on NES are gray instead of green. The bigger green planes show up as the correct green. It seem to only affect certain values of green.

It's a more cumbersome setup, but you're better off using Direct Video along with an RGB-to-YPbPr transcoder.

EDIT: Just adding an external RGB-to-YPbPr transcoder to the analogue I/O board might be enough to fix these specific colour issues, but I don't have any experience with the analogue I/O board. Direct Video was released just before I setup my MiSTer two years ago, and that's the path I went down.

zaffo256 wrote: ↑Wed Dec 29, 2021 9:31 pm I got the exact same problem with a Kit I bought on amazon.ca. My I/O board look a lot like yours with the RGB fan. I wonder if it's not just a defect with bad resistor values. I'm trying to find a reliable way to try HDMI direct video to component without having to mod a cable to put sync on green, but I can't find anything. I'm kind of scared to buy a new I/O board from a more reputable seller, because I'm not sure if this is not just a 6bits vs 8bits DAC symptom or an actual defect.

Ah ok, great to know. Seems it's most likely a defective I/O board then .. ?

I just thought to try this on my Retrotink 5x. It exhibits pretty much the exact same issues my CRT was having.

For anyone interested here's a video connected to the Retrotink & OLED: https://youtu.be/CW1HzBBsYvY

It also shows some interference in the static pattern that I thought was my CRT having a hard time, but is in fact part of the signal coming out.

The Retrotink (like the CRT) required SOG to be set to OVR. Setting it to auto gave no image on the Retortink, and a rolling on on the CRT.

zaffo256 wrote: ↑Wed Dec 29, 2021 9:31 pm Another example for me are the first enemy planes in 1942 on NES are gray instead of green. The bigger green planes show up as the correct green. It seem to only affect certain values of green.

Yeah there's lots of weird but subtle differences. On NES Contra, the mountains in the background look reddish. Initially I thought it was the pallette as if you change it from 'Smooth' to something else it goes away! But same colors aren't seen via HDMI.

Fired up mister outputting scandoubled RGBHV over the VGA port to my Mitsubishi VGA CRT that can handle SoG. I looked at the RGBW full color screens in 240p test suite on Genesis, and toggled the SoG switch while looking at each color. Green intensity decreased slightly when flipping SoG to ON. Red and Blue where unaffected. White took on a more reddish hue (guessing since it includes green naturally.)

I also observed slightly purple sky in the opening of Metal Slug with SoG ON. My I/O board is a 6.1 from Misteraddons. So I suspect this is just another flaw of the I/O board design and not a sign of a defective unit, but maybe more people with the right equipment can replicate.

The difference I observed was slight but I have a feeling it would be more pronounced at 240p; when I've worked with a VGA monitor that does not recognize SoG and instead turns very green when the SoG switch flipped on, the intensity of the green tint was higher at lower resolutions. So the degree to which SoG skews the color the opposite direction (reducing green) on a display that can interpret SoG, might be larger at 240p.

One person on the forum with an aliexpress board reported the same problem and screenshotted the same Metal Slug level with purple tinting that matches yours.

I made the mistake of buying chinese parts which apparently lack 1% resistors and I've decided to keep them and maybe swap out the electrical components except the connectors to build a second MiSTer with them as a project. I didn't end up testing the analog I/O I got since the SNAC pins wouldn't fit all the way due to bulging solder joints but I regrettably tried the ram module which tested bad right away as well as the USB board. Thankfully I got official MiSTer parts coming and if I'm not horribly unlucky I didn't affect my DE-10 in any deleterious way

FoxbatStargazer wrote: ↑Wed Dec 29, 2021 3:24 am
Does anyone know if there are vga to scart cables that would do the job ?

https://misteraddons.com/products/video ... 3472225413

mineral55 wrote: ↑Thu Dec 30, 2021 4:10 am One person on the forum with an aliexpress board reported the same problem and screenshotted the same Metal Slug level with purple tinting that matches yours.

Ok cheers, this looks to be exactly the same issue. It’s like the curve of the green is off rather than reduced. Guess points at incorrect parts being used on the I/O board.