How to convert RGB to composite?

[punkysuen]

I successfully installed art_emudriver and everything works fine.
I am currently connecting a Windows PC to PVM by VGA cable.
The next step I want to try is to play AES games by GroovyMAME on CRT TV through composite RCA.

Should I do soldering work on VGA cable to make RGBHV into composite signal?
If so, what should I solder to make it succeed?
Or any suggestion?

As I want to get the result as close as the original AES console, a VGA-to-RCA box is not preferred.

Thanks!

[buttersoft]

Not a simple conversion, and not one that gets used very much, so i'm not aware of any schematics. Have you tried google?

Short of that, something like a j-rok converter is about as good as it gets. They do seem to be out of stock tho, so you might ask about that - http://www.arcadeshop.com/s/1/c_jrok%2btv.htm

[keilmillerjr]

I am always seeking the same thing as almost all our TV's in usa have composite video. However, I am always disappointed. I bought a $40 HDMI to composite adapter that is complete garbage. Bought 4 Roku express plus that has composite video. They "upgraded" the model to drop composite. Thought about getting a mister. Someone makes a composite adapter for it. No case and will get broken. Scraped that idea. Raspberry pi has composite, but I got fed up with the Bluetooth never working right. Anything that will be around kids needs a case!

[lilshawn]

I bought a $40 HDMI to composite adapter that is complete garbage.

no no, that's just... how it is. anything that mixes a signal with another signal that later has to be stripped out electronically is going to leave tons of artifacting, ghosting, colorshifting, noise, and lord knows what else. it's just what composite is. it's something that will always look bad compared to literally EVERY other output method except RF modulation.

sadly, you are right. most every TV in North America is basically RF and composite...sometimes S-video... with the occasional Component input (480i only) in really late models before flat panel TV started to become popular.

about the only thing I suggest is to see if you can manage to RGB modify the TV. you will be disappointed with literally any other convertor or adapter.

[keilmillerjr]

I bought a $40 HDMI to composite adapter that is complete garbage.

no no, that's just... how it is. anything that mixes a signal with another signal that later has to be stripped out electronically is going to leave tons of artifacting, ghosting, colorshifting, noise, and lord knows what else. it's just what composite is. it's something that will always look bad compared to literally EVERY other output method except RF modulation.

sadly, you are right. most every TV in North America is basically RF and composite...sometimes S-video... with the occasional Component input (480i only) in really late models before flat panel TV started to become popular.

about the only thing I suggest is to see if you can manage to RGB modify the TV. you will be disappointed with literally any other convertor or adapter.

no, no. Audio and video signal quality is fine. It is complete garbage because it drops audio and video signal.

[punkysuen]

Not a simple conversion, and not one that gets used very much, so i'm not aware of any schematics. Have you tried google?

Short of that, something like a j-rok converter is about as good as it gets. They do seem to be out of stock tho, so you might ask about that - http://www.arcadeshop.com/s/1/c_jrok%2btv.htm

Thanks for the direction, I will try to contact Jrok.

I have searched a while, but no schematic found.

[buttersoft]

https://pdf1.alldatasheet.com/datasheet-pdf/view/46645/SONY/CXA1645M.html
That chip does RGB to S-Video, and there's example schamtics for PAL and NTSC on page 10. You could then go Y/C to composite somehow?

I'm sure i learned about that chip on the shmups forum. If you want to search, this is the link - https://shmups.system11.org/search.php?keywords=CXA1645&terms=all&author=&sc=1&sf=all&sk=t&sd=d&sr=posts&st=0&ch=300&t=0&sid=275c16b1f77f3b05a2690d862db82684&submit=Search

[Recapnation]

The original AES console was not meant for composite video (no matter if you lived in the USA), don't delude yourself.

[Zebidee]

You can solder so RGB mod a TV and you'll be very happy.

[Recapnation]

He said he already has a PVM, so getting RGB is not an issue for him.

[Zebidee]

*deleted*

[buttersoft]

Zeb, i thought he was expressing the opinion that it wasn't worth hunting down a solution to produce composite video. Especially given he has an RGB display. I'm not sure I see the contradiction? And I'm certain recap wasn't trying to attack you, he's more helpful than that

[Zebidee]

Zeb, i thought he was expressing the opinion that it wasn't worth hunting down a solution to produce composite video. Especially given he has an RGB display. I'm not sure I see the contradiction? And I'm certain recap wasn't trying to attack you, he's more helpful than that

OK, point taken and I appreciate your input buttersoft. Maybe I'm a bit too sensitive to trolling at the moment, there seems to be a lot of it about in the age of COVID (stress levels, depression etc are high atm). I felt that recapnation was trying to shut me down as off-topic which immediately raises a red flag to me, thus my reaction. I've been doing this hobby for 15 years & done more cabs etc than most people here, with all kinds of displays, so if I think I have something worthwhile to add then I will, and won't be told off like a newbie. With benefit of doubt, my sincere apologies to recapnation, I want this to be a place for everyone to be nice, friendly, inclusive and helpful.

I would like to make some points to explain different perspectives and exactly why I think OP should reconsider RGB modding CRT TV:

1. For anyone seriously into this hobby, too many CRTs is barely enough. So multiple RGB displays is always good in my books (so long as you have the space and partner allows!). I personally have 8-10 CRTs (would need to check), at other times my count has been over 20.
2. In this hobby, people usually (95%) look at RGB-composite conversion so they can use a TV they have. If that is the case, then modding a TV to RGB would probably be easier than soldering a conversion circuit. There is another 5% or so that might just really want to play console games on composite because that is what some were made for (eg Nintendo 64), but recapnation has already made the point that AES games would look bad that way. So moving on...
3. My third take on this is that a PVM (assuming a Sony) will have a Trinitron screen which gives bright colours and extremely sharp pixels with well-defined scan lines. The screen is a weird shape too. Not everybody likes this for all games - I personally don't like PVMs at all for vertical games. Having a CRT TV for playing arcade & console games would probably be a better retro-experience. If that is what the OP really wants, then again RGB modding is probably the more sensible way to go.
4. Most people agree that RGB will look better than composite anyway
5. OP appears to have the soldering skills required

So there we go, five reasons and eight paragraphs instead of one sentence. Hope that makes more sense now. We all like to make assumptions, but maybe punkysuen has something to add here, like a dedication to the purity of composite video of something, given that is who we are talking about.

[punkysuen]

https://pdf1.alldatasheet.com/datasheet-pdf/view/46645/SONY/CXA1645M.html
That chip does RGB to S-Video, and there's example schamtics for PAL and NTSC on page 10. You could then go Y/C to composite somehow?

I'm sure i learned about that chip on the shmups forum. If you want to search, this is the link - https://shmups.system11.org/search.php?keywords=CXA1645&terms=all&author=&sc=1&sf=all&sk=t&sd=d&sr=posts&st=0&ch=300&t=0&sid=275c16b1f77f3b05a2690d862db82684&submit=Search

Thanks for sharing.
The diagram is so much fun to study.

[punkysuen]

Sorry that I made some sentences not clear enough.
My purpose of converting RGB to composite is not just for AES, actually I want to play other emulators such as NES and SNES. Taken AES to say is simply because I played it by composite in a video game shop in my childhood, so I want to try composite.

[punkysuen]

I have an idea, and want to hear some thoughts on it.
Rather than soldering by myself, would it be simpler to use C-Box?
I found a stuff like C-Box but only includes the video signal part.
Does anyone think the result would be exact the same as using Jrok's converter or do soldering job?

[Zebidee]

My Chinese is too rusty to read that! Note that getting anything out of China (assuming that's where it is) might take a while in the current climate.

Unfortunately, not so many people on this forum do composite - I guess it might be more common on the console-related forums like what buttersoft linked to. But stay here because this is an interesting topic!

The main thing to watch out for is a transcoder that maintains the original video mode, rather than just scaling the picture or forcing it into a preset mode like 640x480i.

Difficult to judge C-Box from just that pic (I googled it and got nothing useful). If you can read the big IC label/number (can be hard to read, can't see in pic), you could look up the datasheet to see what it does to the signal. I'd guess the IC handles the colour space conversion into Y/C (luma/chroma), combines and amplifies it for output. Is that a s-video output as well (can't see end)? Makes sense if you have already have the Y/C. Looks like it can handle both NTSC and PAL as it has both oscillators. Pots on the RGB inputs is a good sign too, gives you some flexibilty there to get the colour balance right. What do the 4 dip-switches do? If it is not too expensive it might be worth trying out.

[punkysuen]

My Chinese is too rusty to read that! Note that getting anything out of China (assuming that's where it is) might take a while in the current climate.

Unfortunately, not so many people on this forum do composite - I guess it might be more common on the console-related forums like what buttersoft linked to. But stay here because this is an interesting topic!

The main thing to watch out for is a transcoder that maintains the original video mode, rather than just scaling the picture or forcing it into a preset mode like 640x480i.

Difficult to judge C-Box from just that pic (I googled it and got nothing useful). If you can read the big IC label/number (can be hard to read, can't see in pic), you could look up the datasheet to see what it does to the signal. I'd guess the IC handles the colour space conversion into Y/C (luma/chroma), combines and amplifies it for output. Is that a s-video output as well (can't see end)? Makes sense if you have already have the Y/C. Looks like it can handle both NTSC and PAL as it has both oscillators. Pots on the RGB inputs is a good sign too, gives you some flexibilty there to get the colour balance right. What do the 4 dip-switches do? If it is not too expensive it might be worth trying out.

This board is about 12USD, not expensive, and I am not rushing for the project, so can wait for the shipping.
I will take a closer look on IC and post a photo here when I get the item.
The Chinese words show that it supports RGBS signal input, S video output and RCA socket (it does not mention input or output).
The 4 dip-switches is for switching between PAL and NTSC.

[Zebidee]

The right side is all the inputs (RGBs & 5v, looks like two options for each).

The middle-right with mostly SMD components (resistors, capacitors and 4 transistors) and smattering of electro caps is for input atttenuation - consistency of RGBs inputs to the big IC.

Big IC does the hard work of colour space conversion to Y/C and combining them. The PAL/NTSC oscillators are the long shiny dudes near the dip-switches.

Outputs are all on the left. I see they have provided a pin to attach ground (?) if needed (back of RCA socket).

USD$12 is a very good price (if it does what we think/hope it does).

[lilshawn]

I guess it might be more common on the console-related forums like what buttersoft linked to.

ehhhh not so much. Most classic console gamers have modded systems to output RGB or compoNENT...most consoles from the NES/Famicom era and up have the ability to output RGB with a few mods or have custom boards available designed to pull video straight out of the PPU chips for display on monitors. compoSITE video is really bad and dirty video and almost nobody but people who don't know about modding or anything would still use composite video...and typically those people just play on emulators or XXXXXXXmini consoles they can hook directly up to HDMI and don't really care what things are supposed to look like. that said, it's supposed to look like hot garbage cause TV's where hot garbage at the time.

like I mentioned, composite is a video signal, with color data jammed into it...with sync data jammed into that. a circuit has to peel each thing out to use it individually...unfortunately, this leaves all kinds of ghosting and lines and color shifting issues after you try and peel all the stuff out and get back down to raw video that you can start putting out to a TV.

this is why basically everything in the world has transitioned to video picture data and video sync data being stored and transmitted separately from each other.

[Zebidee]

lilshawn, Amen to that! Though I have heard of NES modders complaining that RGB is too sharp. Guess it also depends on the CRT used.

Here's a few half-serious, light hearted but innovative solutions to getting that composite look - output to monitor in RGB but tweak the focus knob slightly so that the image is a bit blurrier; move the yoke or dynamic convergence (other knobs) until it is all slightly out; introduce lots of crappy RF interference around the signal lines to reproduce that nostalgic ghosting (there's two of me!), and/or maybe just run them for about 30-60 metres (adjust length to suit); run a power drill or washing machine from the same power socket as well to get some quality electromagnetic interference on the AC line, just like you had at home as a kid. 

[arfink]

Op, you probably want a Neobitz-S. I believe they are currently sold by Jamma Nation X.