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Naomi video on 15Khz looks pretty terrible

BroadwayJose said:
how exactly are you feeding the downscaled image to the jamma edge? I'd like to try something like this out, but struggling to wrap my head around how this will work alongside translation of the controls from JVS to standard jamma.
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Poor mans way, get a cheap jamma female/male finger board, break the traces for your video signal and tap from there. One side of finger board will be video from the naomi, that goes to your converter then other side will be converted video back into your jamma side of the loom.
 
tiff_lee said:
Poor mans way, get a cheap jamma female/male finger board, break the traces for your video signal and tap from there. One side of finger board will be video from the naomi, that goes to your converter then other side will be converted video back into your jamma side of the loom.
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tiff, tiff, we are all arcade snobs here. C'mon now brutha. Cheap does not mean improper.

Whip up a few of these fingerboards and away you go.
 
@tiff_lee nothing wrong with fingerboard modding if it gets the job done :D

I was wrong though, the GBS-C only downscales to 240P, so no medium res. I have managed to get hold of a UVC in the meantime, and a Sega Jamma IO. So I will be trying out both routes to check what looks best. For sure both will look better than what I'm stuck with now at least.

So basically it will be interlaced and more pixels vs progressive and less pixels.

Thanks again for the tip @opt2not, you managed to extend my "geekstuff to-do list" with a few extra tasks :D
 
Glad you were able to find a UVC, they’re awesome. Lots of uses for this device and probably the best downscaler there is out there.
 
Very interested in seeing your results @Sp33dFr34k. Please share how it goes with UVC. If it's possible to downscale to 240p with UVC, please also show how that goes, as this will likely be my path but with GBS-C.
 
BroadwayJose said:
Very interested in seeing your results @Sp33dFr34k. Please share how it goes with UVC. If it's possible to downscale to 240p with UVC, please also show how that goes, as this will likely be my path but with GBS-C.
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It's definitely my intention to share the results, but it might take a while due to lack of time... I also wonder how I would capture the CRT image properly. Any advise on this would be appreciated. I know @opt2not has one, so maybe he already has some comparison shots he can share? :)

Btw, I think downscaling to 240P will look really bad with most games, they were not made with this resolution in mind. But I will definitely try it out, just to have a complete comparison.
 
Semi on-topic, but I coincidentally just asked Joko about finding one of these:

1656514732078.png


Barely any info out there but it looks to me like an official second RGB amplifier for the Sega Jamma/JVS adapter
I thought my setup was faulty for the longest time 'cause the output of the Naomi through my Rev. B Jamma adapter to my Astro City has always been dogshit. None of the wavyness/overlapping issues OP is describing and the flickering didn't bother me at all (MS8 "soft" switch surprisingly helps!) but the colors are incredibly dim and washed out. I guess Sega knew as much and had a lil daughterboard solution that taps 5v from CN6, basically doing what RealMFnG was plugging away on awhile back.

It looks incredibly simple from the few pics available to recreate but if anyone has the genuine article hit me up, I'd love to trace out the circuit completely and see if it actually improves the situation significantly. Though to be honest it'd probably be easier to just roll your own PCB with the usual TI amps
 
Sp33dFr34k said:
Btw, I think downscaling to 240P will look really bad with most games
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It really depends on the method of downsampling, decimation (as the UVC dose) is perfect for Naomi as its a simple 50% reduction (ie every other line is removed).
640x480 becomes a perfect 320x240.

If your a fan of big/fattie scanlines like me, I think you'll love the look (tho I own a Vewlix and play Naomi @ 640x480 /w no scanlines).
 
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Today I did a quick proof of concept using GBS-C to downscale Naomi 31Khz 480p mode to 15Khz. Did not have a spare standalone 15Khz TV/monitor handy nor a spare fingerboard so I went with the following configuration to test with:

  • Naomi at 31Khz > VGA out to 1x4 distribution device
  • Distribution device > 31Khz VGA monitor
  • Distribution device > GBS-C VGA in > VGA out to Jammacon (there is a HD15 to SCART passthrough installed) > Astro City cab #2

Naomi is connected to the Capcom IO (minus the video of course) which is then connected to Astro City #1. In this test configuration this will route controls to cab #1 while the video goes to cab #2.

Here are my results:
View: https://youtu.be/SxAPARGmjUc


Tried snapping some pics but I'm not really good at this for CRTs, at least not with my current phone. This one is the best of the bunch:
20220705_122817.jpg


The video might paint a better picture, I let the Capcom vs SNK attract mode run through to the end. Although funny enough the Naomi froze when it ended haha.

Again, not really sure how well it will translate through video or pics but to my eyes this is a vast improvement over the capabilities of the Capcom and Sega IO boards. Colors are now vibrant, no motion blur, no ghosting from what little I've seen so far during testing. Need to find time to test further, try other games, etc but as a starting point I think this is significant progress.

Things to note:
The display appeared to not want to lock in initially. What I did to correct this was to play with some resizing and position settings in gbscontrol. Whatever those changes did, it caused the video signal to stabilize. From there I adjusted h-size and h-position on the monitor remote board and we were in business. I should have taken pics prior to the changes but I'll probably see it again in this state as l test further.

I have a netboot setup and while it goes through the options during a game load, this apparently resets the Naomi hardware to a point where the video signal is temporarily lost. GBS-C doesn't react to this well and while my VGA monitor did automatically sync afterwards, GBS-C did not. I needed to switch off and re-select the downscale preset before the signal came back.

In the end, it's a positive first step. Next is finding a jamma fingerboard and wiring up a female HD15 setup to try the video passthrough solution which was suggested earlier in the thread, give it a shot all in one cab this time.
 
Nice looking result, although I wonder if the Jammacon amps the signal in your chain. Curious to see the difference once you hook it up straight from the GBS-C to the jamma fingerboard. MvC is a title which is a very good candidate for 240P, I wonder what a 3D title like DOA2 would look like.
 
MvC and CvS both use pixel-doubled 240p sprites upscaled to 480p, so those games will probably look great downscaled to 240p.
 
Okay, small update from my side. I ordered a Sega Jamma IO, specifically the Rev B also known 838-13683-93. It was recommended to me by @AlxUnderBase.

Previously I had the Naomi connected straight to my MS9 chassis via the 15 pin AMP UP, H and V sync wired seperately. It worked, but the colors were really dull and washed out.

Now with the Sega Jamma IO it looks a LOT better, colors are way more vibrant, white is actually white instead of light-greyish.

Really a huge upgrade, despite what has been said about this IO before. It's sadly really difficult to get this on video properly, at least for my phone.

Next step is getting the UVC wired in for some 15 and 24khz action, also waiting for the 15/24khz relay switcher, which @FrancoB has kindly offered :)

20220719_175117.jpg
 
@Sp33dFr34k That's exactly the same Sega IO I have and got garbage video quality video out of. I wonder if it needs to be serviced or something? In any case, glad you get better results than I did and I still look forward to seeing how your UVC setup performs.

There was also discussion earlier in this thread about an add-on board Sega made to address RGB amplification but I guess nothing has come from that search as of yet.

One other possibility exists here - apparently OP in that thread sees better video results with what appears to be a cloned Capcom IO board:
https://www.arcade-projects.com/threads/setting-up-chinese-naomi-jvs-i-o.21872/

I'm actually waiting on delivery for this to test it out. The whole GBS-C downscaling setup I tried seems a bit clunky to manage and I ultimately see it as a workaround rather than a long term solution in this case. Would rather have a UVC setup to operate in-line with the rest of the JAMMA configuration but since that's basically not an option anymore, hopefully this other IO will be a good enough alternative.
 
I also think it's weird, do you have the exact same partnumber @BroadwayJose? Might be worth recapping it, see if that helps.

BTW, the picture of the IO posted before with the VGA addon board ends in 92 I've noticed, mine is a 93. Not sure what the difference is.

I know @AlxUnderBase has both the Rev. B and the Chinese Capcom IO clone. Maybe he can comment on the differences between the Rev B and the Chinese clone.
 
Just to add some pictures to the talk, obviously it looks better in person, but just to give you guys an idea. Sorry for the bad quality, put my DSLR on a tripod, but it's still quite difficult to capture good quality pics (especially without the bar going across).

These pictures were taken straight via the Naomi's VGA (so no amp).

IMG_5971.JPGIMG_5950.jpgIMG_5961.jpg

These ones are taken with the Sega 838-13683-93 IO (so amped video).

IMG_5891.jpgIMG_5888.jpgIMG_5919.jpgIMG_5908.jpg

The difference is like day and night in person, hopefully the (rather bad) pictures do show the difference as well.
 
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The MS9 is designed to take TTL-level video signals only. (3-5vpp) You were previously feeding the Naomi's VGA connector straight into the MS9. The Naomi only outputs consumer level 0.7vp-p video signals. So of course it's going to look terrible. You'd have to max out your contrast knob to get any sort of visable picture at all.

The JAMMA IO you bought has the worst video amp, but it's still going to look better than no video amp at all. I would still recommend finding another JAMMA IO, either the Capcom IO or the later Sega JAMMA IO with silver SMD caps on it. Those will look even better. I'm willing to bet you're still having to turn the contrast knob up a bit with your current IO.
 
andynumbers said:
The MS9 is designed to take TTL-level video signals only. (3-5vpp) You were previously feeding the Naomi's VGA connector straight into the MS9. The Naomi only outputs consumer level 0.7vp-p video signals. So of course it's going to look terrible. You'd have to max out your contrast knob to get any sort of visable picture at all.
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Of course, I understand that and never said otherwise :) I used to crank the contrast knob all the way up to get it to look anywhere near decent indeed.

andynumbers said:
The JAMMA IO you bought has the worst video amp, but it's still going to look better than no video amp at all. I would still recommend finding another JAMMA IO, either the Capcom IO or the later Sega JAMMA IO with silver SMD caps on it. Those will look even better. I'm willing to bet you're still having to turn the contrast knob up a bit with your current IO.
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I'd be willing to buy the latter one, for the sake of testing it out. The Capcom IO seems to have bad input lag according to Niko IIRC. What's the exact typenumber of the later Sega jamma IO? And no, I didn't touch the contrast knob with this IO, just left it in the middle which looks fine for my jamma PCB's and everything else I throw at it.
 
andynumbers said:
You want the one shown here: https://wiki.arcadeotaku.com/w/JVS#Sega_838-13683-02
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I'll look for one of those, thanks. What's the difference exactly between the two?

Edit: just bought one.

Also wondering, I've tried using the Ultimarc video amp some time ago, but that didn't seem to do work. The image got brighter and brighter up to the point where the image went completely white. Any ideas about that?
 
Sp33dFr34k said:
I'll look for one of those, thanks. What's the difference exactly between the two?

Edit: just bought one.

Also wondering, I've tried using the Ultimarc video amp some time ago, but that didn't seem to do work. The image got brighter and brighter up to the point where the image went completely white. Any ideas about that?
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The video amp is better on the later Sega IO.

I would recommend staying away from the Ultimarc. It's just a crappy generic amp that was pulled from the J-pac design.
 
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