OSSC Pro and the NAC Splitfire Jamma Capture Compatibility Thread-a-go-go.

[djpsykom1]

Ahoy arcadians, candycabbers, and CGA freaks!
Per request, we’re creating a thread to follow compatibility issues with the NAC Splitfire Jamma Capture Device.

What is the Splitfire?  https://www.arcade-projects.com/threads/nac-splitfire-jamma-streaming-solution.7200/
How can I buy one?  Buy it from the fine folks at Birdland here… https://birdlandarcade.com/products/splitfire

Over the last few years, the Splitfire has been the rather defacto standard for capturing most arcade cabinets for fighting tournaments, twitchstreams, and content creators world-wide.  I personally run these in all my cabinets, and during testing with the OSSC Pro, I instantly ran into an issue with compatibility after receiving and employing the new OSSC Pro.

Working with the good folks at VGP, we were able to get some stability via X-posts (twitter)
Convoluted Twitter Timeline Details here: https://twitter.com/psykomantis/status/1726308750498390395

I broadcast using the current OSSC 1.07 and Splitfire combination in multiple arcade cabinets in my setup.
My Twitchstream here : http://twitch.tv/djpsykom1

I’ve been starting to extensively test the OSSC Pro with my PCB collection.  If there’s a board you’d like tested, I’m here to assist as best as I can (time & tides)
Link to this collection here : https://docs.google.com/spreadsheets/d/1LIKeDgNmQ7dPtS7dlCaVbb8IQLE1ODMxCIorEP2CXTg/edit?usp=sharing

I’ll be just leaving this as a placeholder for any OSSCP settings, and findings as Birdland is actively working with VGP to get a test unit shipped out to them.

Thank you for everybody coming together to make this the best scaler ever!

 

My configuration:
Arcade PCB -> Splitfire Capture card -> CGA/VGA out -> OSSCP/OSSC -> Datapath E1S Capture Card (in workstation)
Extron cabling between all.

• This topic was modified 1 year, 1 month ago by djpsykom1.
• This topic was modified 1 year, 1 month ago by djpsykom1.
• This topic was modified 1 year, 1 month ago by djpsykom1.

[BuckoA51]

Hi, thanks for opening a thread. That’s an amazing collection of arcade boards you have there and will provide a huge amount of interesting data.

I did see your Twitter thread and I just want to get a bit more information, and make sure we’ve covered all bases.

Let’s just focus on NBA Jam for now. You said that you can capture using OSSC Classic and the Splitfire ?

Can you confirm that you tried OSSC Pro in both pure and adaptive line multiplier mode, and did it work then?

In scaler mode, it looked like you were unlocking the frame rate to 100hz? Is this board 60hz or is it more like 59, 58, etc… can you please post what the OSSC thinks the boards refresh rate is (also the OSSC Classic would be interesting to see too).

In scaler mode you sometimes had output mode set to CRT, can you confirm you’re NOT doing this now?

Many thanks and hopefully we’ll get to the bottom of this.

[djpsykom1]

I’ll start with NBA JAM

Here’s my settings.
These settings kinda work with the Splitfire in Scaler mode.
You get consistent visual glitching and artifacting in this mode.
The below settings were pretty much the closest I could get the OSSCP to somewhat lock on to the signal from the splitfires.
Switching from Scaler to line modes, I lose picture or get intermittent picture.
I’ll be updating the main thread with my current capture configuration.

CRT mode gives me a non-centered picture, and lower quality.
DFP seems to be more stable to the capture card, and also frames the picture better for all PCBs.

 

• This reply was modified 1 year, 1 month ago by djpsykom1.
• This reply was modified 1 year, 1 month ago by djpsykom1.
• This reply was modified 1 year, 1 month ago by djpsykom1.
• This reply was modified 1 year, 1 month ago by djpsykom1.
• This reply was modified 1 year, 1 month ago by djpsykom1.

[BuckoA51]

That’s interesting that you say the OSSC Pro behaves differently in line multiplication mode compared to the OSSC Classic, as they should be identical.

Now, from your screenshots the first thing that jumps out at me is framelock is set to “Off – 120hz”. I assume it’s because NBA jam has a refresh of 54.70hz. Can you select the framelock option and show me exactly which options are shown?

[djpsykom1]

I’ll mess with Framelock later, and see if I can get you detail when I get home.

 

Mind you, I can use my current OSSC 1.07 (pre-hardware mod) all day with only capture issues with certain PCBs. (as noted above).
This is why I wanted to graduate to the OSSCP because I assumed the new generation will capture the oddball boards I have.
Now… Screwing around with the OSSCP and the slightly stable settings listed above, I was able to somewhat lock into an image through the OSSCP and the splitfire with Batsugun.

 

Testing the OSSCP using an old jamma capture method (one I was using to successfully capture Toaplan boards, and other oddities the old OSSC/Splitfire didn’t work well with),
this SCART adapter works fine with Line Multiplication mode and Scaler modes.
The sync distortion, and incompatibilities seem to only exist between the Splitfire and the OSSCP no matter if Scaler or Line Multiplier modes.

• This reply was modified 1 year, 1 month ago by djpsykom1.
• This reply was modified 1 year, 1 month ago by djpsykom1.

[BuckoA51]

At 59.39 I would not expect that board to have an issue frame locking with OSSC Pro at all. Is there a reason you unlocked the frame rate to 120hz?

[marqs]

Have you tried tweaking any of the AV1-3 sync settings, especially TTL Hsync Vth and glitch filter length? You should also set H-PLL Loop Gain to maximum when using e.g. certain Toaplan2 PCBs with extreme sync irregularity where framelock needs to be disabled. In general most arcade boards should run fine with framelock so I’m wondering why that kind of setup has issues when the TTL sync is supposed to be clean. Analog sync path has slighly more filtering which may explain why a scart adapter or usual supergun works without issues out of the box.

[marqs]

I just tested a Toaplan 2 PCB (Knuckle Bash) which has the problematic sync characteristic. I have a typical supergun with 100ohm series resistor on the sync line (apparently Splitfire has a sync buffer + 470ohm resistor). I tried with both normal SCART cable and a special SCART cable which connects sync directly to HSYNC pin as in your setup.

1. Normal SCART cable
Works out of the box on my monitor at default settings (framelock on, HPLL loop gain=0). Unsurprisingly there is skew at top of the picture where sync irregularity takes place. Increasing HPLL loop gain to 1 removes most of the skew while the monitor still keeps sync. Increasing the setting further breaks sync unless I switch off framelock in which case the skew can be almost completely eliminated.

2. Special SCART cable
Out of the box with default settings there are frequent sync drops (framelock on) or artifacts (framelock off). This is best highlighted by the red LED in LM modes. If I increase or decrease TTL Hsync Vth by 1, the sync stabilizes. This indicates there is a bug in the ADC chip datasheet and I need investigate further. Decreasing or increasing the value by one additional step retains stable sync, but going further up/down makes in unstable again.

Out of your PCBs it would be good to test if Killer Instinct and Xexex work OK since they have been reported having problems with original OSSC (anything not working with OSSC would be good to check).

[djpsykom1]

Sorry for the late response, I tried all the settings you suggested, and still had issues.

Cabling doesn’t make a difference.  The problem is specifically with the Splitfire capture card.
Everything else I’ve plugged into the unit bypassing that card works fine.

Using a Scart bypass jamma capture card, I’m able to get a stable signal, but it’s not optimal for my application as it degrades the signal going to the arcade monitors.

I just don’t understand why the old OSSC works fine with the Splitfire vs the new pro unit.  All things point to it working fine, but I feel it’s something that you folks just need to get a hold of a unit yourselves and experience the issues.
It doesn’t matter what PCB I have plugged in, they all exhibit the same sync behavior.  This is also tested with multiple splitfire units I have on hand, running in different cabinets.  They all perform the same.
I had 2 spare unboxed units on hand, and they had the same sync issues, no matter what OSSC settings I chose.

• This reply was modified 1 year, 1 month ago by djpsykom1.

[marqs]

I think I’ve found a potential root cause for the issue. It seems that a capacitor in level conversion circuit recommended by video ADC manufacturer is doing more harm than good. After removing that my setup with the special scart cable started to work with default settings (previously needed adjustment of sync threshold). I’ll need to continue the investigation, but if you are eager to try and are confident with your soldering skills, C41 is the one to remove (at the same time it makes sense to remove C42 to avoid similar issue with HV sync source). They are close to the video ADC either on top or bottom side of the PCB.

[BuckoA51]

I’ll add that as long as this work is done to a good standard on your OSSC Pro PCB I’ll honour the warranty.

Markus we should discuss if we modify this for the next batch too.

[djpsykom1]

 

 

I removed c41 and c42.  Still having the issue with the Splitfire.

 

[djpsykom1]

Tried all settings.  Still unstable signal.  The picture is a bit clearer but it still jumps and throws the capture offline.

[marqs]

I’ll need to build similar sync buffer circuit that Splitfire has and test with that. Does it have some 74HCT IC or what on the sync line?

[BuckoA51]

@marqs, Birdland Arcade reached out to me by e-mail and offered to send a Splitfire unit to test with, if you like I can e-mail them back and get them to send it to you in Finland. Looks like they’re based in Germany so no customs to worry about.

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