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Keyboard latency

danluu.com

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Re: Keyboard latency

#131

Post by kazinator »

You have to look at fingertip travel time, not keycap travel time, for a more complete picture.

Those cracker-thin chicklets that comprise the Apple Magic keyboard will only make you faster if you rest your fingertips on the caps.

That may not work so well in all games; it depends on the controls. If you rest a finger on a certain key, but a situation requires you to use that finger to react with a different (though near by) key, you're at a disadvantage compared to having the finger raised so that it can strike either key with equal speed.

Re: Keyboard latency

#132

Post by clebio »

AmVess wrote: post #16
colanderman wrote: post #9

I'm surprised the "humans don't notice 100 ms" argument is even made. That's trivially debunkable with a simple blind A/B test at the command line using `sleep 0.1` with and without `sleep` aliased to `true`. To my eyes, the delay is obvious at 100 ms, noticeable at 50 ms, barely perceptible at 20 ms, and unnoticeable at 10 ms. Not to mention that 100 ms is musically a 16th note at 150 bpm. Being off by a 16th note e…

Yes, and something like a touch interface is very obvious, too. Look at this video on Youtube from Microsoft Applied Sciences Group: High Performance Touch. https://www.youtube.com/watch?v=vOvQCPLkPt4 You can plainly see that 100ms is an eternity. While keyboards aren't the same thing, but high latency is noticeable. I had to change a keyboard because of the near eternity of when I pressed a key and when it registere…

You realize this video (or a version of it) is linked in the article itself, yeah?

Re: Keyboard latency

#133

Post by stefco_ »

xbkingx wrote: post #112
korethr wrote: post #2

IMO, a better measure would be from activation of the switch, as opposed to the beginning of key travel. I don't start waiting for the character to appear on my screen from the moment I begin to press down. My anticipation begins when I feel the tactile feedback of the switch activating (or the switch bottoming out on switches that don't offer tactile feedback). On a keyboard with good tactile feedback, I might not m…

I immediately switched to skeptic mode when I saw no actuation points or normalization for travel distance. All this is showing is that to move further it takes longer. Duh. Why even bother pointing out the polling rate? That's like setting up runners at random places on the racetrack to measure who's faster. The guy/gal that starts closest to the finish line isn't necessarily faster. I'm using Cherry MX Speed switch…

> I immediately switched to skeptic mode when I saw no actuation points or normalization for travel distance. All this is showing is that to move further it takes longer.

I thought his explanation (that delay from the start of the motion) was a good one. Unless someone is starting with a key partially depressed/near the actuation point (which you certainly could do), the key travel time is going to be a part of the perceived delay. Seems fair to me, given that delay and perception are the point of the post.

Now, if you think that gamers are starting with partially-depressed keys and therefore will actually experience less of a keystroke delay, that would be a valid counterargument.

> Every step of the process has huge flaws and he doesn't even use a reasonable set of devices.

I don't think this is being portrayed as an especially accurate study; the author includes plenty of caveats.

Re: Keyboard latency

#134

Post by triclops200 »

JimmyAustin wrote: post #98
tomxor wrote: post #89

Earlier quoted context omitted.

Your probably right, it's an old TN panel in a 10yr old laptop... I'm gona have to steal someones shiny modern IPS in a minute :P (I know they are generally slower response but it's 10 years newer so you never know) [edit] No IPS still super slow. How common are >60Hz computer displays these days?

Common for gamers, relatively unknown for everyone else. They typically go up to 144Hz.

There are newer ones that do 240hz, but they are TN.

Re: Keyboard latency

#135

Post by crispyambulance »

colanderman wrote: post #9

I'm surprised the "humans don't notice 100 ms" argument is even made. That's trivially debunkable with a simple blind A/B test at the command line using `sleep 0.1` with and without `sleep` aliased to `true`. To my eyes, the delay is obvious at 100 ms, noticeable at 50 ms, barely perceptible at 20 ms, and unnoticeable at 10 ms. Not to mention that 100 ms is musically a 16th note at 150 bpm. Being off by a 16th note e…

The other thing to consider is how is latency perceived when actually TYPING in real life. My guess is that the difference between the shortest latency and the longest latency hardly matters for the purpose of a human putting words on a screen. There's so many other cognitive activities going on that I can't imagine someone would notice unless they're specifically looking for it and nothing else. Really, does anyone complain about this stuff? even world-class touch typists?

Of course there is some threshold of latency when it starts to become noticeable/disconcerting for some fraction of people and probably quite a lot more when half of all typists start to notice. Anyone can definitely feel this on terminals connected to very remote machines.

This is an interesting topic and am glad that Mr Luu is looking into it. The measurements described are absolutely a valuable first step towards understanding what latency really means for human factors in typing (first, what is the f-ing latency). I expect the folks at Logitech and other places have significant proprietary research on this stuff, but maybe not?

Re: Keyboard latency

#136

Post by ilaksh »

This great article and the other recent one from him started me down the path of thinking about an end-to-end optimized modern computer and operating environment.

If you _could_ (not saying it's easy or even necessarily practical at all) drop replace all of the slow stuff like high-latency keyboards, syscalls, CPU-GPU communication (i.e. effective HSA) and build some proof-of-concept operating environment (that was explicitly incompatible with existing stuff).. I think you could get a pretty fast computer. It would be fun to try.

Anyway is there a Cherry MX keyboard that has low travel and low latency overall?

Re: Keyboard latency

#137

Post by kentt »

Makes me wonder about the latency of bt keyboards as well as my custom made keyboard controller.

HHKB JP with Hasu's controller

Re: Keyboard latency

#138

Post by DigitalJack »

xbkingx wrote: post #112
korethr wrote: post #2

IMO, a better measure would be from activation of the switch, as opposed to the beginning of key travel. I don't start waiting for the character to appear on my screen from the moment I begin to press down. My anticipation begins when I feel the tactile feedback of the switch activating (or the switch bottoming out on switches that don't offer tactile feedback). On a keyboard with good tactile feedback, I might not m…

I immediately switched to skeptic mode when I saw no actuation points or normalization for travel distance. All this is showing is that to move further it takes longer. Duh. Why even bother pointing out the polling rate? That's like setting up runners at random places on the racetrack to measure who's faster. The guy/gal that starts closest to the finish line isn't necessarily faster. I'm using Cherry MX Speed switch…

Do they spec the force in newtons? Without mass, g’s don’t really say much except as maybe a relative measure between things of the same mass.

Re: Keyboard latency

#139

Post by drivebyops »

colanderman wrote: post #9

I'm surprised the "humans don't notice 100 ms" argument is even made. That's trivially debunkable with a simple blind A/B test at the command line using `sleep 0.1` with and without `sleep` aliased to `true`. To my eyes, the delay is obvious at 100 ms, noticeable at 50 ms, barely perceptible at 20 ms, and unnoticeable at 10 ms. Not to mention that 100 ms is musically a 16th note at 150 bpm. Being off by a 16th note e…

People have made AB input lag tolerance game here

https://forums.blurbusters.com/viewtopic.php?f=10&t=1134&sid...

Some people in that thread are tolerant to 10ms...

Re: Keyboard latency

#140

Post by cakebrewery »

BoppreH wrote: post #117
pdkl95 wrote: post #92

Earlier quoted context omitted.

> strike a key less than 100 ms after some visual stimuli, I'm sure I couldn't do it The video game "Super Hexagon"[1] is a surprisingly interesting demonstration of this limitation, and how the mind tries to workaround the problem. The higher difficulties ("hexagonest"[2]) seem impossible at first. In the easier levels you can react , but now the time it takes to see the scree, parse the simple graphics, recognize t…

This is also clear on rhythm games like Stepmania. Here's a random video from a keyboard user: https://youtu.be/TWiMnENdcyY?t=56 At this speed the player is reacting (and hitting with correct timing) about ten notes (arrows) per second. This is possible by memorizing and reacting to group patterns instead of individual notes, but more importantly, reacting unconsciously. A player can play at this level without consci…

It's hard to explain, but with these sort of games your brain "feels" if something is off (a little bit of latency, etc). I get a similar feeling playing instruments. It's quick to adapt to these changes, but the feeling of something being "different" still lingers for a bit.

Used to play (still could if I got back to it) at that difficulty with my keyboard. Got to the point where I could have conversations while playing. I also play guitar so I stopped playing Stepmania to avoid extra strain.

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