HDMI buffer delay

[therealquaid]

From what I understand the HDMI output on the Nestang currently buffers one frame.
Which I think means one more frame of delay compared to a NES on a CRT?

I play NES Tetris on a Retron AV 1 on a CRT. And am hoping to find an affordable option that has minimal delay and doesn't require a CRT.

What I'm wondering is if there is a way to buffer less than one frame and still work with most monitors?

I've read through the GitHub page on Snestang too and it is mentioned that there is less than a frame buffered due to memory constraints.

And I've also read that the Mister only buffers four scanlines when using VGA out/line doubling.

Is it possible to use the same buffer from SNESTang? And would this provide less of a delay?

I don't know much about FPGA programming or upscaling but I'd be willing to fiddle with it myself once my Nano 20K arrives.

[therealquaid]

There's at least a way to test the lag of LCDs deterministically, here: https://github.com/MiSTer-devel/MiSTerLaggy_MiSTer

That is a great way to test latency.
And as for the Time Sleuth, You can even make one out of the Tang Nano 20k.
https://www.youtube.com/watch?v=UXOC4lAyS5Q
But not usable as a NES at the same time so probably not that useful in this case.

I found my current monitor by people in forums testing it with a Time Sleuth and posting the results (an LG 32MP58HQ). It has around 10ms at the middle of the screen. Where a CRT has about 8.3.
If you want to find monitors tested for input lag rtings is probably the best site for this.
https://www.rtings.com/monitor/tests/inputs/input-lag
You need to check the 60hz input lag. The closer to 8.3 the better. I think anything around 10 or under is going to be basically indistinguishable as long as the input source isn't adding any extra lag. (the NESTang core in this case at the moment)
The monitors there tend to be more on the expensive side.
I think a lot of cheaper monitors can work with the frame rate and have low input lag but the problem is they're mostly untested so it's hard to choose without taking a risk.

RetroRGB is also a good channel and site talking about input lag often.
https://www.youtube.com/watch?v=7VOsOuQ5mhM

Testing for capabilities for non-standard framerates would be harder. Do you know of any in particular that do this?

I'm not sure of a way to test this. The only way I know of is people plugging in their console through an upscaler that doesn't change the framerate (like the Retrotink 2x) and seeing if it works for them. Usually if it's not compatible the image won't show or will be like a flickering mess.

This also makes me think, if we are unable to obviate this requirement, perhaps adding VGA out and using a CRT computer monitor might be easier and less expensive than to find an LCD with all these requirements, if we have enough LUTs to do it. There's a VGA encoder for another NES FPGA implementation here: https://github.com/brandonpelfrey/ice40-nes/blob/master/src/mod_vga_encoder.v

Yeah having an analogue output is the easiest way to ensure you're getting the minimal amount of lag possible.
I'm not sure if the Tang Nano 20k has the LUTs to do it. But that's because I know very little about FPGA programming at the moment. It's all new to me. I was thrust into this after plugging my console into a tv and getting really bad input lag about 6 months ago.
Then began the search for ways to mitigate it.
I just got the Tang Nano 20k a few weeks ago but the controller wasn't working and was waiting for that to be worked out. Nice work on fixing that last problem by the way.
Now I will be able to start doing some testing.

My lag testing has been simply recording at 240fps and calculating the difference between a button press and an action on the screen.
Not as accurate as the Time Sleuth but it helped me get an emulator closer by comparing it to a console on CRT. The problem there is the emulators polling of the controller is not synchronized. So you get jitter, where sometimes an input will be received only on the next frame. When you're doing movements that require one input on one frame and another input on the next (an 8 high quicktap on level 19 in Tetris requires this) it means sometimes even if you hit the input at the perfect time you miss because of the way the controller is polled.
That's how I started looking into FPGA stuff.