Can SNAC Zapper Work on 31Khz VGA CRT Monitor

[naylord]

I know the obvious answer to anything lightgun related is simple: it will never work on ANYTHING that isn't your standard consumer 15Khz CRT. I can see why this necessary for two reasons: 1 the lag and 2 the sync signal. With the guncon 2 you strip the sync signal and that gets used to infer when the frame starts drawing, from there the precise timing of when the gun detects light effectively gives you a pointer on the screen.

The Zapper is much simpler though; you can't target any random location on the screen. It seems to just flash only on the targets in a sequence of frames allowing it to detect light on a specific frame, and then infer a target hit/miss based on that. In my view, as long as the lag is still zero, it should still work. Forced scandoubler shouldn't add any lag so in theory to me it sounds like this should work.

I ask if anyone has tried it because I haven't bought a snac cable for NES yet. Basically weather I would or wouldn't would be based on this research as I mainly play on a VGA CRT as it's giving me a PVM like experience that I love.

[Nioreh]

The NES Zapper has a filter in it tuned to only register a 15kHz light source. This is done so you can't point it at a lightbulb etc. 31kHz should be too high a flicker rate for the Zapper to register, but I haven't tried it myself.

[Nioreh]

Thinking about it a little more; if you use 100% black scanline effect you will effectively recreate a 240p 15kHz flicker rate on a 31kHz VGA display, so then it should work.

[naylord]

Is it tuned to 15Khz? I thought the way it defeats "lightbulbs" from hacking it wasnt through any sort of frequency but just noticing the black frame before the light frame. Basically when you fire a shot the screen turns totally black, and then only the targets are white. So it has to measure black and then white to be a hit. With multiple targets it staggers their white square on the screen so it can know based on the delay to seeing light which target it was. Though this defeats using a lightbulb to cheat because it knows right away that it was detecting light from the start of the shot if you fire while pointed at one.

[Nioreh]

Yes, there is a filter in it, and that is the main reason it won't register lightbulbs. That "black frame check" is a mix of misconceptions and sort of facts, and it is unfortunately spread by a lot of youtubers etc. There is no need to look for a black frame before looking for a hit, even though some games do this as well. Even if there was no filter, you could look for black at the end of vblank for example, instead of wasting an entire frame of black. The response time of the zapper is really quick, a couple of scanlines maybe. The extra black frame is not necessary, and is not used by all games.

[nymous]

I can confirm it works, tried several games like Wild Gunman or Hogan's Alley, both works fine with CRT monitor. AFAIK SNES/Genesis wouldn't work though.

[naylord]

Yeah I finally got the SNAC adapter and it's awesome getting to enjoy lightgun games on my 31Khz CRT monitor! My 15 Khz consumer trinitron is so much fuzzier so it always sucks needing to play lightgun games on that.

[Missus]

Yeah I finally got the SNAC adapter and it's awesome getting to enjoy lightgun games on my 31Khz CRT monitor! My 15 Khz consumer trinitron is so much fuzzier so it always sucks needing to play lightgun games on that.

so what was the one weird trick?
the 100% black scanline mentioned before?
or it 'just worked' as you originally postulated?

[naylord]

Yeah I finally got the SNAC adapter and it's awesome getting to enjoy lightgun games on my 31Khz CRT monitor! My 15 Khz consumer trinitron is so much fuzzier so it always sucks needing to play lightgun games on that.

so what was the one weird trick?
the 100% black scanline mentioned before?
or it 'just worked' as you originally postulated?

It just worked. It's because the 31 khz monitor still has zero lag so the timing for the black frame + frame with target being white still lines up.
As an experiment, I tried my Guncon with point blank on psx core running over snac; the snac port has a composite sync out but obviously it shouldn't quite line up here. It interestingly you actually get the correct vertical position, but you'll be all over the place horizontally (or "miss" the screen entirely about 2/3rds of the time). That makes sense though because if you draw every line multiple times, the timings of when the beam hits the lightgun won't have anything to do with the expected horizontal position but the vertical position will be in the ballpark.