Pixel perfect lagless Neo Geo on an HDTV (WIP)

[Bibin]

Cross-posted from nesdev, sorry, I'm lazy.
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I'll go into details when I have more of a chance to do a proper write-up, but I'm working on a solution that scales up the Neo Geo RGB output to exactly double the resolution to allow for unencumbered use on a modern display, like a TFT monitor or HDTV. The targeted output is DVI/HDMI, but for now I am using VGA since my FPGA dev board has the DAC on board, but not TMDS-capable outputs.

The timings are exactly double that of the Neo Geo MVS, with a horizontal scan rate of ~31KHz and a vertical scan rate of 60Hz. There are absolutely zero frames of lag as an entire frame is not buffered but rather an alternating line buffer is used. Right now I am busy doing some rewiring to get all the colors working, so my initial tests only use a few bits from each color channel (initially just one!)

Here are some progress pictures:






I will post as I make more progress. I will be moving this to a different FPGA platform as this Altera DE2 isn't actually mine and it would be awful to have to stop half way through because I had to return a rented FPGA.

[Guntz]

That is really awesome! Any hope this proof of concept could be consolidated into a converter box for regular gamers?

[Bibin]

That is really awesome! Any hope this proof of concept could be consolidated into a converter box for regular gamers?

I don't think it can be so easily packaged for an end user, as the way I'm doing it relies on clocking in pixels from the pixel clock (or some relation thereof). This could theoretically be adapted for any system that has similar timings and has an external DAC with the RGB bits separated (Sega System C comes to mind). This could work for any home console, but you'd have to provide 1) a good ADC for the analogue RGB and 2) a phase-locked loop to generate double the horizontal scan rate based on the console's TTL sync output. This design manages to be simple because the Neo Geo makes these signals available without any conversion. It also means I can probably fit this on a somewhat cheap CPLD and not have much trouble packaging it onto something tiny instead of a big FPGA dev board.

We will cross that road when we get to it, though.

On that note, here is the blue channel working 100% with the timings fixed to work nicely on both a modern LCD monitor and an old CRT monitor:




The only thing stopping me from using full color right now is that I'm out of female header pins to use... other than that, it's pretty far along!

[Bibin]

I'm pretty much done with the development phase of this project:




Optional scanlines as well:




With the scanlines turned on, on a PC CRT monitor, it looks very authentic:

[Bibin]

Here is it working:

[slk486]

This is an absurdly cool and innovative project. 'scribed.

[fluxcore]

I'm interested in this.

I guess I kind of prefer the idea of an external line doubler (such as the BitBlitz which is some kind of development hell by the looks of things) though, since it would be much more universal. This appears to require a large number of connections (specifically in the bowels of the system) which probably isn't very externalisable/reusable. For instance, I have both an MVS and an AES - I can't imagine being able to swap it between the two very easily.

Of course, I suppose it should be fairly cheap if it's just a CPLD.

[Guntz]

What's the big deal about modding an MVS board with this VGA add-on? It's completely worth it. I don't know if drilling more AES shells is though. I wouldn't do that even for component, not when RGB is easily available on the AV out port.

[Bibin]

I'm interested in this.

I guess I kind of prefer the idea of an external line doubler (such as the BitBlitz which is some kind of development hell by the looks of things) though, since it would be much more universal. This appears to require a large number of connections (specifically in the bowels of the system) which probably isn't very externalisable/reusable. For instance, I have both an MVS and an AES - I can't imagine being able to swap it between the two very easily.

Of course, I suppose it should be fairly cheap if it's just a CPLD.

Yeah, this is the sort of thing you'd build into the system. For a dedicated system though, anything that is doing conversion from the analogue format will be objectively worse than one that doesn't do that. With a good PLL and a decent ADC, this same concept could be utilized to make a lag-free generic RGB line doubler.

[fluxcore]

What's the big deal about modding an MVS board with this VGA add-on? It's completely worth it. I don't know if drilling more AES shells is though. I wouldn't do that even for component, not when RGB is easily available on the AV out port.

Oh sure, completely agree. I may have fiddled with the innards of my AES, but I really don't want to drill holes into the case. And MVSes are totally ripe for defamation I'm certainly looking to replace my GBS-8200 wherever possible (it has a few undesirable behaviours, including some lag), and this could do the trick nicely for the MVS, would just be nice for it to be a bit more generic

[Bibin]

Oh sure, completely agree. I may have fiddled with the innards of my AES, but I really don't want to drill holes into the case. And MVSes are totally ripe for defamation I'm certainly looking to replace my GBS-8200 wherever possible (it has a few undesirable behaviours, including some lag), and this could do the trick nicely for the MVS, would just be nice for it to be a bit more generic

Oh boy, don't get me started on the GBS-8200, there's just too much to go over...

[fluxcore]

Saw this on Hack-a-day today, nice!