The VisionRGB cards are particularly suited to 15KHz capture, which is officially below the VGA standard (IBM VGA is 31KHz). As Qlex mentioned the StarTech PEXHDCAP (which is a no-name version of the Micomsoft SC-500N1) is also capable of 15KHz capture at a much lower price point, albeit with lower picture quality (see here to compare the quality, top and bottom left is VisionRGB, top right is PEXHDCAP). You're right that there's a difference between JAMMA and VGA, most notably the RGB signal level is 3-5 volts peak-to-peak, whereas VGA is 0.7 volts. Of lesser concern is that VGA officially dictates separated horizontal and vertical sync, but the very common practice of using composite sync on the horizontal sync pin of the VGA connector is supported by practically all monitors and capture devices. In order to bring down the levels, the most easy method is with a serial resistor, I use 220Ω but as I recall Burbruee was having problems with the picture being too bright so he used a higher value. Keep in mind that only the RGB signal lines should be reduced, sync should stay 3-5Vpp (so passed through untouched from JAMMA) because it is considered a digital TTL signal.
Really useful. Thanks for clearing this up. I just called the vendor to discuss this, as I was worried the signal may be blown out in the 3-5 V range. According to him, the VGA for digital TTL signal uses different pins and the Epiphan USB3 capture devices accept these inputs without problem. I haven't tested it yet of course, but I really want to rule out a more mobile USB3 solution--much as the PCIe VisionRGB seems perfect for this. Unlike the PEXHDCAP I think these seem to be pro quality capture devices.
My USB 3.0 approach has perhaps lived up to your expectations so far, Muf--with the Epiphan AV.io at least, I had terrible results. It says VGA, but the engineer said it took the EGA/CGA levels. Having tried it though with TGM, it only is able to capture 4 seconds at a time before losing the sync and restarting apparently. Bummer as it captures my high res camcorder beautifully so it isn't anything to do with speed, it's definitely HSYNC problems. I'm waiting on the DVI2USB 3.0 which seems to be more configurable, and allows manual HSYNC config. What if I get the Micomsoft XRGB-3 (to output in HDMI to my capture device) with its DB15 port? Does anyone know if it accepts the RGB, or is it only VGA too? -------------------------------------------------- Edit: There's also this thing I guess. Can anyone vouch for the quality of the VGA output from one of these?
If it's anything like the CGA input on a CM8833, the signal will be digitised (because it expects a digital signal), and the colour depth subsequently reduced to 8 colours. I believe colour_thief still has an Epiphan capture card, and as far as I can remember it does not accept 240p input. To be fair, VisionRGB devices pre-2011 firmware didn't support it either, until I opened a support ticket with them and sent them a physical JAMMA board including supergun, which they used to fix the card's firmware to support these low resolutions. You might be able to do the same with Epiphan, would be nice to have another vendor that also supports pixel-perfect 240p capture. The XRGB is an upscaler specifically meant to scale 240p to 480p (or higher). Note that the XRGB-2 has a switch to enable high impedance CGA/JAMMA sources to be connected directly, which the XRGB-3 lacks. Going through an upscaler probably gets in the way of getting properly pixel-perfect output, though. I also seem to remember paibox mentioning that capturing from an XRGB-mini (Framemeister) also had some issues, at least with SNES/N64 or something. Personally, I think you're complicating the capture setup greatly and introducing an extra point of failure in the processing chain by adding a scaler. KevinDDR has experience with Gonbes scalers, as far as I know they treat 240p as 480i and attempt to "deinterlace" the progressive image. It looks horrible.
Don't get the Gonbes scaler. It's pure shit. And for me personally when used with TAP after a few minutes the picture started to shake. Something with the sync and the TAP frequency. I'd also suggest staying away from XRGB. I had a setup including a framemeister before getting my datapath card and it's good for upscaling but the colors will never look right no matter what.. Colors look really strange actually.
Dang. That's dedication! Thanks for doing it. To be honest, I am not expecting the Epiphan to work without some help from their guys. I will say that they are a pretty awesome team from my experience. I have a Sigma AV7000 I'd be willing to send them, if it comes to that, but it only outputs SCART/JP21 at the moment so I'd have to find a way to wire that together. I also need another test board; TGM is hard to come by these days and I'd be afraid to send that. I will probably get the VisionRGB at this rate, but I'm hopeful the Epiphan DVI2USB 3.0 will work with good quality eventually. -Brandon
