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Naomi video on 15Khz looks pretty terrible

BroadwayJose

BroadwayJose

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The title kinda says it all. For the first time I hooked up my Naomi2 via Capcom I/O to an Astro City cab. Colors are washed out and the image is pretty crap overall. Up to now I've been running on 31Khz mode directly connected to VGA monitors and it looked outstanding of course. On 15Khz mode via the IO board (using same VGA cable and everything else including a Sun PSU to power the Naomi itself), it's night and day how much worse the video looks.

Tried also with the Sega ver b I/O and it looked even worse than with the Capcom I/O: wavy effects, shaky image, colors even more washed out. By comparison I have no such issues running a system 256 via Namco I/O on the same cab in 15Khz mode - video looks sharp and much cleaner than the Naomi setup. Definitely no such issues with native 15Khz hardware on this machine, so it's not the monitor and likely not the cabinet components directly. Pretty sure it's a problem with the IO board but I'm not sure what to do to improve the image. Any suggestions?
 
Didn't have much time to capture more in-game images this afternoon but hopefully this one from the netboot loading process helps a bit:

20220622_132704.jpg


I was able to stabilize the wavy and stutter effects a bit by playing with the v-hold pot on the monitor, so thats a plus. No such luck with the poor colors unfortunately. What sucks is that I can run Dreamcast via RGB into the same cab through the Jammaizer and it looks much better than what these Naomi I/O boards are producing. Pretty sure the Dreamcast is pushing out 480i also in this case.

In any case, I'm all ears on what options might exist to service these I/O boards or if there's another board out there which is known to produce a cleaner 15Khz signal + support 6 buttons via kick harness.
 
Seems to be the same issue I'm having with my Naomi setup in my NAC. I've been looking for help and got in touch with @RealMFnG to create a video amp gerber based off the supergun schematics of @Arthrimus. I *think* that would solve the problem, @RealMFnG was kind enough to help me with that. The thread is here on AP somewhere, I ordered PCB's and soldered one up but it didn't work. He then found a little mistake in the PCB, which he didn't find time yet for to correct. I don't know of any similar standalone product that could help resort this issue. I tried the video amp by Ultimarc before, but that also didn't work. Maybe someone else could chime in with a possible solution.

Edit: found the topic https://www.arcade-projects.com/threads/rgb-amp-vga-to-jamma.15501/
 
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This is a crazy issue. Looking at the work from @RealMFnG this is an issue many folks are having. Why is it happening in some cases? I've used naomi's through capcom I/O's on both big blues with k7000 and candy cabs at 15khz with no loss of image quality.
 
Sp33dFr34k said:
It's probably because it's interlaced. Most 15Khz stuff you run in a cab is progressive, which does look a lot better than 480i.
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^this. A lot of arcade monitors look terrible in 480i and unfortunately that's what you get with NAOMI in 15KHz mode. it literally just throws out every odd line of the image on one frame and then every even line of the image on the next... and viola you've cut the resolution in half without having to design the game for a lower resolution.

Taito Type X1 works the same way as NAOMI for it's 15KHz support.

Namco System 12 and System 10 have a number of interlaced games (some of them can be changed between 480i and 240P in the test menu) and Aleck64 is another one with mostly interlaced games, some of the G-Net Games like ZOOO are 480i as well.

if you have any of these other 480i platforms I'd test those to see if it's really an IO issue or your monitor just not liking 480i
 
I don't have a Naomi to test exactly but interlaced Dreamcast via RGB on my 15khz PVM looks way, way worse than the few interlaced G-Net games like Block Kuzushi or RC de Go on the same monitor via supergun. I think whatever hardware Sega used for this is just crap
 
Before the Naomi experiment I tried Tekken 5 DR on a Namco 256 with the same cab. Looks so much better than the Naomi. I'm assuming the 256 is sending 480i in this setup?

Everything I'm reading so far seems to point that I'm SOL when it comes to Naomi on 15Khz sadly. Although it's strange that other monitors seem to handle this setup better than ms8 or ms9.

I have Tekken Tag on System 12. Any idea if this game is interlaced? I'll check in the test menu tomorrow but from what I recall it looked pretty fantastic in 15Khz on this cab.
 
Just my anecdotal experience: I used to run a NAOMI2 through a Capcom IO onto a PVM-14M4U via 480i and the picture was pretty damn good. I consider myself pretty damn picky as well. Looking at what others have written it looks like quite a few monitors simply don't like 480i. There is a plus side to this, however. Now you have an excuse to get another cabinet! : )
 
The best method is set the Naomi to 480p (this keeps it progressive signal) then feed that (VGA) into a UVC for 240p (RGBs) output.
Once you interduce interlacing, at any point in the chain, the quality turns to total garbage.

UVC achieves lagless downscale of 640x480 via decimation (every other line is removed).
1655964399721.jpeg


I owned one, when I forever banished CRTs from my home I no longer had a use for it.
If you still believe CRTs have a place in this world, I highly suggest purchasing one.
 
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@jassin000 the UVC is REALLY hard to get, and if you can get hold of one, it's really expensive. However, a GBS-C like device costs peanuts and can do 240P downscaling as well. I've actually tried (emulated) 240P Naomi/Atomiswave games on my MS9, but that looks really shitty, like the graphics are way worse than 480i. I prefer the dull 480i to 240P, these games really weren't designed to be played in 240P imo. I'm still hoping @RealMFnG will have time to correct the issue with the video amp, have high hopes that should fix it :)

Oh, and for those referencing the Capcom IO, I actually think that one has a RGB amp onboard or something as it does really look better. It's just I don't need any of the other Capcom IO features, just the video amp part of it.
 
The thing about interlaced games on arcade monitors, is that it's very important you adjust your monitor's v-hold so that the lines are separated. This will give you a full, complete image. Before adjusting, you may get inverted lines, or lines drawn on top of each other (kind of like a pseudo 240p but with 30hz flicker).

Unfortunately this is where the MS8 and MS9 monitors suffer the most. The MS9 doesn't have a v-hold adjustment, and it's always adjusted so that interlaced lines are always drawn on top of each other, preserving the 240p scanline effect, but now with 100% more flickering lines. The MS8 has a v-hold adjustment, but it doesn't fare any better.

Other monitors can properly handle interlaced content by separating the lines. I've had good success with the Hitachi from a Super Neo 29 (although this monitor isn't that great), and a Pentranic 38" from a Gauntlet Legends showcase cab. Other off-brand monitors like Toei should also perform well for 480i.

The tl;dr is: avoid Nanao MS8/MS9 for 480i.
 
BroadwayJose said:
I have Tekken Tag on System 12. Any idea if this game is interlaced? I'll check in the test menu tomorrow but from what I recall it looked pretty fantastic in 15Khz on this cab.
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Yes, the system 12 games are either non interlaced (240p) or interlaced (480i) and can be set in the menu for certain games. Through JAMMA and the vga (in JAMMA MODE) the board will use composite sync, however if you hook up a JVS board, you have the additional settings of changing the sync type: Composite (RGBS) or Separate (RGBHV) sync. This will only work in JVS MODE and you have to use the VGA ports. Separate sync looks incredible.

I’m guessing the reason some interlaced games look terrible on certain monitors is because the Naomi uses RGBHV instead or RGBS, could that possibly affect the V hold on certain monitors? I don’t have a arcade monitor so I use a CRT tv (which only does 480i through component) and use a RGBS/HV to COMPONENT video converter box and it looks great!
 
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Interesting insights, I'm not quite sure I understand it though. @andynumbers what you're saying is that the MS8/MS9's should be giving weird (flickering/inverted) lines with 480i as they don't have a (adequate) vhold pot? I can't relate to those issues, just the image being dull and not very vibrant. I guess I will try and source a Capcom IO again as in my mind it looked better on one of those. Just too bad I've sold both mine for peanuts as I thought I wasn't going to use them again... :) If I'm wrong and it doesn't look any better then I guess it's time for us to give up on this quest.
 
Sp33dFr34k said:
Interesting insights, I'm not quite sure I understand it though. @andynumbers what you're saying is that the MS8/MS9's should be giving weird (flickering/inverted) lines with 480i as they don't have a (adequate) vhold pot? I can't relate to those issues, just the image being dull and not very vibrant. I guess I will try and source a Capcom IO again as in my mind it looked better on one of those. Just too bad I've sold both mine for peanuts as I thought I wasn't going to use them again... :) If I'm wrong and it doesn't look any better then I guess it's time for us to give up on this quest.
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The Sega JAMMA IO with the little brown capacitors has a garbage video amp. It looks terrible. The 2nd Sega JAMMA IO with the SMD caps is a little better but still not great. The amp on the Capcom IO is probably the best. If that amp could be reproduced as a standalone board it would be real nice.

The issue with MS9 I think is that MS9 was designed with 240p in mind. There's a chip on the chassis that handles automatic V-hold, so it's not adjustable. But basically it's designed to always treat the scanlines like they are always 240p. The result on a 480i signal is that the scanlines are still drawn on top of each other like 240p, but of course now they flicker at a 30hz frequency. It's a bit hard to explain, but you can really notice it on fine details like small text and checkerboarded pixels.
 
Get yourself a downscaler that does 24khz, flip the jumper on the chassis to switch it to 24khz (or if you have the auto-switching variant, don’t need to do anything to the chassis).
Connect the Naomi outputting 31khz to the downscaler then feed the output from that to the Jamma edge.

Enjoy the beautiful image of medium resolution.

0DA80835-F5B3-4C4D-B318-826C2B886E8D.jpeg

9F611EFB-F6AF-4254-AC20-63C72D52DB99.jpeg

38E9D450-15CE-4CD7-8247-A4EA3B8927DE.jpeg
 
opt2not said:
Get yourself a downscaler that does 24khz, flip the jumper on the chassis to switch it to 24khz (or if you have the auto-switching variant, don’t need to do anything to the chassis).
Connect the Naomi outputting 31khz to the downscaler then feed the output from that to the Jamma edge.

Enjoy the beautiful image of medium resolution.

0DA80835-F5B3-4C4D-B318-826C2B886E8D.jpeg

9F611EFB-F6AF-4254-AC20-63C72D52DB99.jpeg

38E9D450-15CE-4CD7-8247-A4EA3B8927DE.jpeg
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Very interesting, didn't think of this at all. NEVER used 24khz on my NAC, not even sure where the jumper is haha. The GBS-C should do downscaling 24Khz, so definitely something I'd like to try, thanks for the tip. Good looking setup btw! :)
 
@opt2not 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.

Also I'm assuming you're using Retrotink5x in this case or something else?
 
BroadwayJose said:
@opt2not 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.

Also I'm assuming you're using Retrotink5x in this case or something else?
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I’ve got the UVC for downscaling, and I followed Emphatic’s guide here for connecting: http://emphatic.se/?p=139

It’s basically an adapter that passes through everything but the video. The video feed comes from the UVC.
 
@opt2not I see - thanks for the breakdown. Too bad UVC is basically unobtainable now, so I'll have to try something different like GBS-C I suppose.

If I'm going to try with an "external" device instead of UVC in this case, I suppose all I would need to do is wire up an input to R, G, B, ground and composite sync to the passthrough board? I don't plan on powering the downscaling device through the cabinet directly.
 
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