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Keyboard latency

danluu.com

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Re: Keyboard latency

#41

Post by azernik »

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…

Another point is that, even if a bit of latency isn't noticeable (say, 20 ms), when added to other sources of latency it can make things noticeably worse.

EDIT: Which the original author said better than me:

> Another problem with this line of reasoning is that the full pipeline from keypress to screen update is quite long and if you say that it’s always fine to add 10ms here and 10ms there, you end up with a much larger amount of bloat through the entire pipeline, which is how we got where we are today, where can buy a system with the CPU that gives you the fastest single-threaded performance money can buy and get 6x the latency of a machine from the 70s.

Re: Keyboard latency

#42

Post by lanius »

xigency wrote: post #32
Stenzel wrote: post #29

Compare with musical keyboards where not only key number but also the velocity matters, so each key has two electrical contacts, and the whole thing is usually scanned around 10kHz for proper velocity measurement. Although key contacts are arranged in a diode matrix, the latency is usually below 2 ms, even with good old MIDI. So neither the keyboard matrix nor the debouncing justify a latency of 10 ms or above. It is…

Now to learn to type with a keyboard... or game I suppose.

Now that would be fun! I think it would be possible to achieve a reasonable typing speed given the right "keyboard layout" (aka the QWERTY equivalent for musical keyboards).

Re: Keyboard latency

#43

Post by confounded »

cjbprime wrote: post #30
andyfleming wrote: post #24

Earlier quoted context omitted.

That's fine though. It's about the experience end-to-end. I love the apple keyboards. I still type faster on them than other keyboards, including high-end mechanical keyboards. The short keys and actuation feel responsive, yet I've never felt like I've accidentally triggered a key.

Same -- I like doing speed typing on typeracer, and after going through mech keyboards and different switch types for a few years, I'm consistently fastest on a non-mechanical ThinkPad USB chiclet keyboard.

I've recently got rid of several extremely expensive mechanical keyboards to go back to a new ThinkPad chiclet. I am somewhat embarrassed to say it's been fantastic.

Re: Keyboard latency

#44

Post by marssaxman »

Nition wrote: post #11
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 wouldn't be surprised if the Apple keyboard is the fastest just because it has very shallow keys.

Sounds like a good argument for the superiority of shallow keys. I've always liked Apple keyboards - actually used their wired USB keyboard for a long time specifically because it felt like typing on a Powerbook.

Re: Keyboard latency

#45

Post by krashidov »

andyfleming wrote: post #24
Nition wrote: post #11

Earlier quoted context omitted.

I wouldn't be surprised if the Apple keyboard is the fastest just because it has very shallow keys.

That's fine though. It's about the experience end-to-end. I love the apple keyboards. I still type faster on them than other keyboards, including high-end mechanical keyboards. The short keys and actuation feel responsive, yet I've never felt like I've accidentally triggered a key.

Agreed. When I first used them I hated them, now I can't really use anything else.

Re: Keyboard latency

#46

Post by mjw1007 »

LoSboccacc wrote: post #33
mjw1007 wrote: post #7

Earlier quoted context omitted.

I agree. Presumably he measured it the way he did because it's easier to measure, rather than because he thinks it's the more meaningful way. (Though maybe his way is more useful if he's interested in whether a keyboard gives an advantage in gaming, rather than whether it's pleasant to type with.)

the article specifically states the reasons for why he messured the whole travel, no guesswork needed > This is because, as a human, you don’t activate the switch, you press the key. A measurement that starts from switch activiation time misses this large component to latency.

That's effectively providing a definition of the latency he's discussing, not an explanation of why that's the sort of latency he finds interesting.

But I see he does goes on to say that he cares about game performance, rather than typing experience: « If, for example, you’re playing a game and start dodging when you see something happen, you have pay the cost of the key movement, which is different for different keyboards. »

For me, I don't care about the time after switch activation, rather about time after the tactile feedback (the "click"). Ideally the character would appear on the screen at the same time as the click; not after, and not before. If a keyboard can 'cheat' and activate the switch before that and hide some latency, that's fine by me.

Re: Keyboard latency

#48

Post by sundvor »

LoSboccacc wrote: post #33
mjw1007 wrote: post #7

Earlier quoted context omitted.

I agree. Presumably he measured it the way he did because it's easier to measure, rather than because he thinks it's the more meaningful way. (Though maybe his way is more useful if he's interested in whether a keyboard gives an advantage in gaming, rather than whether it's pleasant to type with.)

the article specifically states the reasons for why he messured the whole travel, no guesswork needed > This is because, as a human, you don’t activate the switch, you press the key. A measurement that starts from switch activiation time misses this large component to latency.

If you game on a mechanical keyboard, you've pretty much worked out exactly where the switch points are and will be working the keys in a fashion different to normal typing. So I'm not quite buying the way the measurements were made vs the purpose of the tests.

Re: Keyboard latency

#49

Post by gsich »

matthavener wrote: post #3

PS/2 keyboards are used by serious gamers because the scan rate is higher than USB. See https://superuser.com/questions/16893/do-usb-or-ps-2-keyboar...

Isn't PS/2 interrupt based? So there would be no scan rate. Haven't looked at your link though.
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