"RetroPix" - CGA->VGA converter

[CraftyMech]

Starting a new project thread for my CGA->VGA converter project. I started the project back in November, and am at the point now where I have a working prototype design.

The purpose of the project is to create a converter board that will accept 15k progressive RGB input, and output VGA. I started the project because of my disappointment with the cheapie solutions out there that suffer from a variety of display quality issues, in particular with low-res games like those on the 60-in-1 board I've been using for testing. Those boards are cheap, but they are jack-of-all-trades designs (supporting interlaced & progressive) and employ a full-frame buffer for conversion, which produces a lag of at least 1 frame. My hope is to be able to provide a optimized line-doubling design, virtually lag free, and built for use with legacy arcade hardware in mind.

There are still a lot of details to take care of, and minor issues to solve, but I wanted to share a short demo video I made using a 60-in-1 board running in CGA mode. Sorry for the so-so video quality, for the next demo video I'll record in HD with proper lighting.

[rablack97]

genius......

[Nephasth]

 

[sharpfork]

  Holy mother of giant, well organized breadboards with SMD breakouts! 

It is really cool to see your idea coming together.  I expect to see a fully functional SMD based prototype at the next meetup!
 

[yotsuya]

Just take my money now!!!! 

[CraftyMech]

Thanks guys, I've been working a lot of late nights over the past month pushing the project closer to completion. More updates will follow soon!

I wanted to avoid SMD chips, but for the speed and capability I needed, DIPs were not available. I figured out a quick and clean technique though for soldering, using a Hakko 808 de-soldering gun. I lay solder across all the pins, and then hit them with quick zaps from the 808. The gun sucks up all the extra solder leaving just the pins soldered to the pads. Not quite as neat as a factory job, but looks clean and works great!

[Nephasth]

What sort of footprint are you aiming for on the final product?

[CraftyMech]

I'm looking to keep the board roughly the same size as the cheapie converter boards. I have not figured out what variety of inputs the board will accept yet, so those choices will impact the size as well. I do want to keep the design compact, so it is still usable in tight spaces, like bartop projects.

[misterbeeez]

I don't understand a thing... 

[emphatic]

This is wonderful, I really look forward to your final version, which I intend to buy.

[dmarcum99]

I'm N-4-1 whenever these make it to market!!!

[CraftyMech]

I'm planning on supporting 16bit color (Neo-geo, CPS) if I can keep the parts cost down. For 8 bit color I can use a cheap resistor network as an effective DAC, but for 16bit color I'll need to switch to dedicated chips.

So time for an informal poll: If you are currently using a CGA->VGA converter board, what platforms/boards are you using it with?

[emphatic]

I currently have a GBS-8220 in my homebuilt Supergun and I have only successfully run Black Tiger, Progear (CPS2) and NEO-GEO on it, my Rygar PCB had horrible input lag, so did my Hacha Mecha Fighter (unplayable). Also tried Silk Worm, but I couldn't get a stable picture. All of these were connected with VGA to my Panasonic Plasma. I hope this information is useful.

[CraftyMech]

I currently have a GBS-8220 in my homebuilt Supergun and I have only successfully run Black Tiger, Progear (CPS2) and NEO-GEO on it, my Rygar PCB had horrible input lag, so did my Hacha Mecha Fighter (unplayable). Also tried Silk Worm, but I couldn't get a stable picture. All of these were connected with VGA to my Panasonic Plasma. I hope this information is useful.

Thanks Emphatic, that info is definitely helpful. Input lag is one attribute where the GBS-8200 falls really short. With a full frame of lag, the delay comes out to ~ 16ms. A line doubling design (buffering a single line of CGA input) has a lag of 64 microseconds, or 250 times faster.

[Pinball Wizard]

Any chance of a medium res to VGA converter in this too or are you just looking to do CGA to VGA?

[Nephasth]

This can't come out soon enough. My Gnobes just lost green!!!

[CraftyMech]

Any chance of a medium res to VGA converter in this too or are you just looking to do CGA to VGA?

Right now just CGA->VGA, but Medium Res is definitely a possibility for the future. The signal timing for Medium Res (25khz) is kind of an odd duck, so the converter design would be a bit different, perhaps with a frame buffer like the GBS-8200. Speaking of the 8200, does anyone know if it will convert a Medium Res signal?

[Rigby]

Combine this with the SLG and you'll really have something, though it will require you to resize the image, and depending on how that's done, you've just added a frame of latency.

Combine this with the SLG, AND(!) support 120hz LCDs and implement alternate frame blanking to improve the LCD performance, and I'll give you $100 per unit.  This will either add 1 source frame of latency (16.6ms) or 0.5 frames of latency (8.4ms), I can't quite work it out in my head.  Seems that while you're drawing the previous frame for 1/120th of a second, the game would render half the next output frame, and while you display a fully blank screen for 1/120th of a second, the game would render the second half of the currently valid frame.  The rendered frame will only be on screen for 1/120th of a second, but that time will begin AFTER the game has written the video to screen, so 0.5 frames of latency.

The proper solution for this is probably to actually reproduce the arcade hardware in an FPGA and drive the video that way.  0 frames of latency, and you could do all the per-line conversion you wanted, though if you chose to support 120hz LCDs, the same 0.5 frame latency would be introduced.  Overall, with MAME itself often providing 1-3 frames of latency, 0.5 frames ain't too shabby.

[CraftyMech]

Combine this with the SLG and you'll really have something, though it will require you to resize the image, and depending on how that's done, you've just added a frame of latency.

Combine this with the SLG, AND(!) support 120hz LCDs and implement alternate frame blanking to improve the LCD performance, and I'll give you $100 per unit.  This will either add 1 source frame of latency (16.6ms) or 0.5 frames of latency (8.4ms), I can't quite work it out in my head.  Seems that while you're drawing the previous frame for 1/120th of a second, the game would render half the next output frame, and while you display a fully blank screen for 1/120th of a second, the game would render the second half of the currently valid frame.  The rendered frame will only be on screen for 1/120th of a second, but that time will begin AFTER the game has written the video to screen, so 0.5 frames of latency.

The proper solution for this is probably to actually reproduce the arcade hardware in an FPGA and drive the video that way.  0 frames of latency, and you could do all the per-line conversion you wanted, though if you chose to support 120hz LCDs, the same 0.5 frame latency would be introduced.  Overall, with MAME itself often providing 1-3 frames of latency, 0.5 frames ain't too shabby.

I am planning on including basic SLG support, similar to how my existing mini SLG product works. The scanline effect is applied to every other line of the VGA output signal.

No plans right now for changing the output refresh rate. The point of the project was a virtually lag-free conversion, so I don't want to implement a frame buffer. The size of the buffers I have implemented is 2 lines of input, which is sufficient for straight line-doubling.

[sabreerbasAlpha]

Sweet xxxxxxxx Who do I make the cheque out too??? Ill buy one right now.

[rCadeGaming]

How is this project coming along?  I know this thread went dead, but I can't find anything else searching.  Is it still in the works?

[CraftyMech]

Wow, it has been almost a year since my first post on this project! I'm still working on this board, although other projects have taken priority during the last year.

I have a Test Pattern Generator for arcade monitors coming out next month, and building and supporting my mini SLG takes up a nice slice of time as well.

That said the CGA->VGA converter project is still alive and well! I've been focusing on stamping out some stubborn issues with some video sources. The design works great with certain signals, and then not so good at all with others. So gradually working towards broader compatibility has been my focus over the last six months. Color depth is also an issue, I designed for 16bit, but since realized that there are 24bit platforms out there that ran at 15k RGB. Still not sure if the first iteration of the board will be 16 or 24bit.

So stay tuned, I can't offer up any kind of release date but the project is definitely still active.

[rCadeGaming]

Glad to hear that the project is alive.  I was wondering if it could be used to linedouble an NTSC standard 480i source to 480p for use with an Extron Emotia.  This would allow a simple method to force 480i to 240p, which would be useful for things like the Game Boy Player (Gamecube), Mega Man 9/10 (Wii), Street Fighter III Third Strike Online (PS3), and various shmups on XBox 360.

[CraftyMech]

If 480i is input, the output signal should be 480p, but probably with some flicker. The converter will see the separate 1/2 frames of the 480i signal as 240p input, but won't handle the offset between 1/2 frames properly without additional logic.

[rCadeGaming]

I know it would normally look awful, but the flickering should get hidden by the Emotia.

I believe all the systems I mentioned output 480i in the NTSC standard, right?

[CraftyMech]

360, Gamecube and Wii I'm pretty sure do 480i, I've actually never owned a PS3 so I'm not sure. For the Xbox 360 I've also used a VGA cable with success for 640x480. I had a chance to play the latest DoDonPachi on a Shmup member's 360 connected to an Astro City via VGA, and it was a pretty sweet setup.

[rCadeGaming]

They all do 480i, I just meant do they exactly follow NSTC standard timing values.  I thought that may help you if we're only talking about a single standard.

DoDonPachi SaiDaiOuJou?  Yeah, that one features updated hi-res graphics on the 360 port, other games in the series, and a lot of the shmups on 360, are 240p.

[CraftyMech]

They should all follow the NTSC 480i standard I would think, given that TVs were the primary display of the target audience. I have a Wii so I can test that out at some point, but I sold my Gamecube awhile back and don't have a PS3. As long as the horizontal timing is close to NTSC, it should not be a problem. The converter locks to the source horizontal timing, rather then looking for a fixed timing interval, so there is some flexibility in the system.

Yep DoDonPachi SaiDaiOuJou would be the game I played. I've been so focused on going from CGA->VGA that I didn't even think about the value of 480i -> 240p for Xbox 360 Shmups. I'm planning a Shmup Jamma cab w/ 15k monitor, it would be great to also be able to play some of the 360 Shmups on there as well.

[rCadeGaming]

Yeah, there are a few titles on every console in between Dreamcast and the current generation that use 240p graphics, but only allow them to be displayed from the system in 480i or higher.  360 is just the worst offender.

[orion]

CraftyMech,
Just out of curiosity have you ever considered expanding your projects outside the scope of the arcade/gaming hobby. I work for a Univesity and my job is to run and install distance learning classrooms done via videoconferencing codecs. Some of our rooms are basically broadcast quality facilities complete with control rooms and the whole 9 yards. This past summer I had to upgrade a classroom/control room from analogue to digital and some of the issues I ran into was a real PITA running the gambit from colorspace issues to HDCP to resolution incompatiblities. While I got everything sorted, I had to use over $10k worth of converters, and scalers to do the job. There are a couple of manufactures out there that offer quality converters for a reasonable price, but they are few and far between. Seems to me with your talents, you could tap into a pretty lucrative market.

[Jusensei]

Hi CraftyMech,

I have a Gonbs basic linedoubler, and I use it with a lot of consoles.
My goal is to have them set at all times and run them instantly.

To achieve this, I need the line doubler to remember the settings for each console.
I know it is not the main purpose of your project, but will your Retropix include such a feature ?

Thanks and keep up the good work ! Love your mini-SLG !

[CraftyMech]

Jusensei: The converter will save separate configurations through the on screen menus, but will not be able to autodetect systems. So you would need to enter the menu, and select the config to load your custom settings when you change systems. At least though you won't have to totally redo your settings each time you switch consoles, like with the Gonbes board. Glad you like the mini SLG!

Orion: I've thought about more advanced video processing before, but there are a couple issues that make the task much more complicated. Unlike a basic line doubler, more versitile upscalers that support HD resolutions make use of a frame buffer, which requires more memory and processing power. The pixel clocks of high resolutions are also much higher, up to and beyond 50mhz. Those speeds require more specialized components, and the design becomes very sensitive to noise and interference, requiring very careful layout and a 4 layer board (top, bottom, ground, and power) to ensure a stable system. I'm not saying I won't explore the possibilities at some point, but I'd need to ramp up my skills before I could tackle that kind of project.

[Jusensei]

Jusensei: The converter will save separate configurations through the on screen menus, but will not be able to autodetect systems. So you would need to enter the menu, and select the config to load your custom settings when you change systems. At least though you won't have to totally redo your settings each time you switch consoles, like with the Gonbes board. Glad you like the mini SLG!

Great ! This is very good news.
How many configs do you think the system will keep in memory ?
I wasn't wishing for any autodetect (but since you said it...).

[CraftyMech]

Probably a dozen config slots, not due to memory constraints (plenty of eprom storage) but just to keep all the slots on a single menu page.

[orion]

Jusensei: The converter will save separate configurations through the on screen menus, but will not be able to autodetect systems. So you would need to enter the menu, and select the config to load your custom settings when you change systems. At least though you won't have to totally redo your settings each time you switch consoles, like with the Gonbes board. Glad you like the mini SLG!

Orion: I've thought about more advanced video processing before, but there are a couple issues that make the task much more complicated. Unlike a basic line doubler, more versitile upscalers that support HD resolutions make use of a frame buffer, which requires more memory and processing power. The pixel clocks of high resolutions are also much higher, up to and beyond 50mhz. Those speeds require more specialized components, and the design becomes very sensitive to noise and interference, requiring very careful layout and a 4 layer board (top, bottom, ground, and power) to ensure a stable system. I'm not saying I won't explore the possibilities at some point, but I'd need to ramp up my skills before I could tackle that kind of project.

I have nothing but the upmost respect for your skills. If I knew then what I know now, I would have busted ---my bottom--- and gone to MIT. Your projects always amaze me (still need to pick up a SLG) and I find them quite interesting. I can see scalers being a different animal from this project, but there are still a lot of converters you could take on. A converter that can take multiple input types and can spit out multiple output types would be nice. A box that could accept HDMI, HD-SDI, and componet, then spit that signal out simultaneously as each format type with selectable colorspace would be a fairly useful converter.

[iscariot]

How's this looking Craftymech?  Any developments?

I was reading the post and got to thinking about integrating the slg into things.  I was wondering if it was possible to hard wire the slg as an effect to the line doubling somehow.  Maybe have it just take the lines and have the output draw only the even lines, and let the odd lines be interpreted by the output device as blanks.  Would that work?