CRT vs LCD input latency

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EnderW

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I do casual speed runs of the Super Nintendo game Mega Man X and like most people, I use an original console and a CRT (in my case a PVM) monitor since they are still the lowest input lag option (supposedly).

I decided to attempt to test this myself since it’s hard to find much in the way of comparisons online due to the huge number of factors.

Here’s my first attempt. I chose the Alienware AW2521HFL since RTINGS lists it as having the lowest input latency at 60Hz (output frequency of the SNES) of all monitors they’ve tested.

I have the SNES output to a component video splitter, with 1 output going to the PVM, and the other going to a Retrotink 5x and upscaled to the LCD over HDMI.

I recorded a slo-mo video using my iPhone at 240 fps. Looks like the PVM is slightly ahead most of the time.

Would like any input for other or better ways to test this, also suggestions on things to try and get the LCD faster.
 

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EnderW said:
I do casual speed runs of the Super Nintendo game Mega Man X and like most people, I use an original console and a CRT (in my case a PVM) monitor since they are still the lowest input lag option (supposedly).

I decided to attempt to test this myself since it’s hard to find much in the way of comparisons online due to the huge number of factors.

Here’s my first attempt. I chose the Alienware AW2521HFL since RTINGS lists it as having the lowest input latency at 60Hz (output frequency of the SNES) of all monitors they’ve tested.

I have the SNES output to a component video splitter, with 1 output going to the PVM, and the other going to a Retrotink 5x and upscaled to the LCD over HDMI.

I recorded a slo-mo video using my iPhone at 240 fps. Looks like the PVM is slightly ahead most of the time.

Would like any input for other or better ways to test this, also suggestions on things to try and get the LCD faster.
Click to expand...
Why try to get a faster LCD, the PVM is awesome and it will be hard to beat it with any LCD.
 
I think you might want to run tests with a game that has a timer updated on every frame? Like mario kart or some other racing thing. That way it's much easier to track if it's on the same frame or not.
 
DooLocsta said:
Why try to get a faster LCD, the PVM is awesome and it will be hard to beat it with any LCD.
Click to expand...
Well eventually this PVM is probably gonna die and good CRTs are getting harder and harder to find.
 
toast0 said:
I think you might want to run tests with a game that has a timer updated on every frame? Like mario kart or some other racing thing. That way it's much easier to track if it's on the same frame or not.
Click to expand...
That’s a good idea although the input latency may be a smaller difference than the 60Hz output from the SNES. Which appears to be the case here, at 185 fps video, it’s around 1/3 of a frame assuming the scrub on my phone is moving at 1 fps.
 
EnderW said:
Well eventually this PVM is probably gonna die and good CRTs are getting harder and harder to find.
Click to expand...
If you have RetroTink you can use VGA CRT - much cheaper than 15KHz CRT with good resolution tube. HDMI to VGA converters do not add latency.
 
Flod (from this forum) did some cool measurements for input lag (measured as time from mouse input to crt lighting up):

https://www.esreality.com/post/2691945/microsecond-input-lag-measurements/

He measured usb-crt latencies as low as 400 microseconds, whereas his LCD was about 4 times as much latency (which is still only about 1.5 ms so still very fast). See histograms here.

prad.de did some very cool measurements, and measured latency between time the CRT receives info from VGA cable until a photodiode detected light from the phosphors - they got a value of 670 nanseconds.

https://www.prad.de/untersuchung-des-testverfahrens-einer-input-lag-messung/
 
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EnderW said:
That’s a good idea although the input latency may be a smaller difference than the 60Hz output from the SNES. Which appears to be the case here, at 185 fps video, it’s around 1/3 of a frame assuming the scrub on my phone is moving at 1 fps.
Click to expand...

That's pretty good. But 1/3rd of a frame is pretty hard to measure. Not sure if there's any sort of lag test rom maybe someone wrote for this, assuming you've got a flashcart.
 
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