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View topic - Possible means for RGB/YPbPr/etc off the SMS/Genesis

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  • Joined: 21 Apr 2019
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Possible means for RGB/YPbPr/etc off the SMS/Genesis
Post Posted: Tue Jun 18, 2019 2:37 pm
Last edited by boye on Tue Jun 18, 2019 5:45 pm; edited 1 time in total
I know this is probably not news to you, but the AV DIN socket outputs RGB natively, so I had an idea kicking around for a plug-and-play box that allows you to display HDMI, RGB, Component, maybe HDMI, and hell, maybe even better Composite video! Also, there could be a switch to switch between the SMS pallette and a true SG-1000 palette.
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Post Posted: Tue Jun 18, 2019 2:53 pm
Perhaps better RGB and Component for sure. I dont know about HDMI to be honest since the signal wouldnt get any better than RGB without a direct digital output and I'm not sure the VDP directly outputs a digital RGB signal either.
As far as true SG-1000 color mode maybe. If someone can find a way to get digital out and make a fast enough digital interpreter then perhaps an FPGA driven internal adapter could do all of these things and more for the SMS.
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Post Posted: Tue Jun 18, 2019 3:51 pm
With the true SG palette, it just replaces the colors that the SMS uses when playing SG games with the true colors the SG-1000 uses. Also, it wouldn't be that hard to map out the colors from an SMS to digital RGB values.
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Post Posted: Tue Jun 18, 2019 4:16 pm
the biggest issue is timing, you dont want a delay between the VDP outputting an image and the "adapter" displaying it. That and there not being any digital signal outputs is one of the biggest reasons why there are not many HDMI adapters for retro consoles. When those consoles have them, they usually require a lot of work and are usually large or complex adapter circuits that become expensive.
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Post Posted: Tue Jun 18, 2019 4:22 pm
You could probably make a replacement VDP with an FPGA to get the desired features. Far from simple, of course.
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Post Posted: Tue Jun 18, 2019 4:31 pm
Maxim wrote
You could probably make a replacement VDP with an FPGA to get the desired features. Far from simple, of course.


I want to say there's already a Mega Drive/Genesis open source VDP out there you can use for a wide range of Altera FPGAs so I assume there may be an SMS one. Though... even making that adapter board and de-soldering the original VDP would not be easy.
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Post Posted: Tue Jun 18, 2019 5:19 pm
What about including a built-in upscaler?
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Post Posted: Tue Jun 18, 2019 5:41 pm
You're still not going to get a clean/cleaner image and cheaper upscalers will have a worse delay and color output.
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Post Posted: Tue Jun 18, 2019 5:44 pm
OK, I'll remove HDMI as a possibility for the time being.
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Post Posted: Tue Jun 18, 2019 5:59 pm
Either way you would need an FPGA just to get the SG1000 color mode. If you go that far you might as well include HDMI and just make a replacement VDP which would be a lot simpler than how they do it on the NES with the PPU pass through. There are already cables out there that give high quality RGB and Composite output, granted through the Mega Drive/Genesis MiniDin but that wouldn't be hard to mod onto an SMS. Both my Game Gear and Sega Master System have been modded with a Mega Drive miniDin port so I dont have to have so many different cables.
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Post Posted: Tue Jun 18, 2019 7:55 pm
Well, the whole idea is that there are no mods necessary.
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Post Posted: Tue Jun 18, 2019 7:58 pm
You can't turn analogue to digital without loss, even with some funky quantisation algorithm to try to hide the noise. Mods are necessary to keep things in the digital realm.
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Post Posted: Tue Jun 18, 2019 8:36 pm
So HDMI is out of the question.
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Post Posted: Wed Jun 19, 2019 12:30 am
At this point yea you only have the ability to work with RGB and Composite. There are quite a few people out there that sell filter and amplifier boards and boast that they're super good... but they're trivial to make in my opinion. Just an amp circuit and maybe a few filter caps all soldered onto a board. Add a nice size ground plane and maybe some shielding over the amp circuit and each individual signal line if you really want to go all out. At that point youre just going overkill though... I personally dont see the use of it, if you want a clear picture then why stop half way, go for digital or go home.
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