5 ms·

This does encourage optimising the OS or application part (eg double buffering and taking another frame is slow), but it doesn’t measure two significant sources

This does encourage optimising the OS or application part (eg double buffering and taking another frame is slow), but it doesn’t measure two significant sources of latency: The latency in the hardware before the signal makes it to the usb (for most keyboards, even specialised gaming keyboards this is like 30ms, which is 2 frames). There is also the latency from when the monitor gets a signal to when the pixels have perceptually finished transitioning. This can be 10s of ms too. So even if the OS has 0 latency, and the monitor measures that, you could still easily observe a latency of say 60ms.

modeless 6y ago
True! I just watched this video [1] they put out with more details, and it sounds like they are working with monitor and mouse manufacturers to build true end-to-end latency measurement when using supported hardware. It would be easy for manufacturers to game these numbers, but hopefully Nvidia will provide some enforcement to prevent that. Maybe they could also add a microphone to measure audio latency because that is another huge problem with modern systems. The video mentions that they get 15 ms end-to-end latency on a 360 Hz monitor in Fortnite. So that's what it takes for a modern system to finally beat the latency that you used to get on, say, an NES connected to a CRT. Still an order of magnitude above the limits of perception though [2]. [1] https://www.youtube.com/watch?v=-cXg7GQogAE https://www.youtube.com/watch?v=-cXg7GQogAE [2] https://www.youtube.com/watch?v=vOvQCPLkPt4 https://www.youtube.com/watch?v=vOvQCPLkPt4
- ksec 6y ago
  Yes! I watched that video many years ago. And then later I remember when media were hyping how "responsive" Apple Pencil was I was thinking what on earth are these people looking at. I thought to myself we would never get there because no one gives a damn about it. How the world has changed! I often wonder at what cost, could we get it down to Sub Ms. Where everything from Input, Video and Audio are sync to the precision of 1ms. There used to be very little incentive to do so. Now that Gaming has taken over I hope it will develop some market perception and value so we could finally move into that direction. The age of Instantaneous Computing.
kllrnohj 6y ago
> for most keyboards, even specialised gaming keyboards this is like 30ms, which is 2 frames Worth noting that unlike some of the other sources being discussed, this source of latency is more due to physical constraints than bad engineering or bloated software. Keyboards are limited by the physical travel time & de-bounce of the mechanical switches themselves. So this is more a tradeoff of using mechanical keyboards at all rather than "gah bloated electron" or whatever. The other common peripheral, mice, don't have this mechanical constraint. They can even achieve sub-10ms for clicks due to the difference in switch expectations ( https://www.rtings.com/mouse/tests/control/latency https://www.rtings.com/mouse/tests/control/latency ) EDIT: Also 30+ms seems to be quite far off. Cherry MX's specs are around 5ms, and I'm getting 8ms playing around with this tool: http://blog.seethis.link/scan-rate-estimator/ http://blog.seethis.link/scan-rate-estimator/
- modeless 6y ago
  I understand keys take time to travel, but you can press them faster if you want. On the other hand I've never understood debounce as a justification for button latency. Surely a properly designed debounce circuit would add zero latency.
  - kllrnohj 6y ago
    > but you can press them faster if you want I mean, yes but not really? There's very real speed limits to the human finger, after all. But the times given above are also quite far off - the actual keyboard numbers seem to be more in the 5-15ms range, not 30+ms. At least, my mechanical gaming keyboard is hitting 8ms on this test: http://blog.seethis.link/scan-rate-estimator/ http://blog.seethis.link/scan-rate-estimator/
  - mlonkibjuyhv 6y ago
    I'm thinking that a debouncer might give rise to some latency when you let go of a button, or at the very least limit the shortest possible keypress. As in the first rising edge is definitely a keypress, but the falling edge is not necessarily a release.
  - 6y ago

modeless 6y ago

True! I just watched this video [1] they put out with more details, and it sounds like they are working with monitor and mouse manufacturers to build true end-to-end latency measurement when using supported hardware. It would be easy for manufacturers to game these numbers, but hopefully Nvidia will provide some enforcement to prevent that. Maybe they could also add a microphone to measure audio latency because that is another huge problem with modern systems. The video mentions that they get 15 ms end-to-end latency on a 360 Hz monitor in Fortnite. So that's what it takes for a modern system to finally beat the latency that you used to get on, say, an NES connected to a CRT. Still an order of magnitude above the limits of perception though [2]. [1] https://www.youtube.com/watch?v=-cXg7GQogAE https://www.youtube.com/watch?v=-cXg7GQogAE [2] https://www.youtube.com/watch?v=vOvQCPLkPt4 https://www.youtube.com/watch?v=vOvQCPLkPt4

ksec 6y ago
Yes! I watched that video many years ago. And then later I remember when media were hyping how "responsive" Apple Pencil was I was thinking what on earth are these people looking at. I thought to myself we would never get there because no one gives a damn about it. How the world has changed! I often wonder at what cost, could we get it down to Sub Ms. Where everything from Input, Video and Audio are sync to the precision of 1ms. There used to be very little incentive to do so. Now that Gaming has taken over I hope it will develop some market perception and value so we could finally move into that direction. The age of Instantaneous Computing.

kllrnohj 6y ago

> for most keyboards, even specialised gaming keyboards this is like 30ms, which is 2 frames Worth noting that unlike some of the other sources being discussed, this source of latency is more due to physical constraints than bad engineering or bloated software. Keyboards are limited by the physical travel time & de-bounce of the mechanical switches themselves. So this is more a tradeoff of using mechanical keyboards at all rather than "gah bloated electron" or whatever. The other common peripheral, mice, don't have this mechanical constraint. They can even achieve sub-10ms for clicks due to the difference in switch expectations ( https://www.rtings.com/mouse/tests/control/latency https://www.rtings.com/mouse/tests/control/latency ) EDIT: Also 30+ms seems to be quite far off. Cherry MX's specs are around 5ms, and I'm getting 8ms playing around with this tool: http://blog.seethis.link/scan-rate-estimator/ http://blog.seethis.link/scan-rate-estimator/

modeless 6y ago
I understand keys take time to travel, but you can press them faster if you want. On the other hand I've never understood debounce as a justification for button latency. Surely a properly designed debounce circuit would add zero latency.
- kllrnohj 6y ago
  > but you can press them faster if you want I mean, yes but not really? There's very real speed limits to the human finger, after all. But the times given above are also quite far off - the actual keyboard numbers seem to be more in the 5-15ms range, not 30+ms. At least, my mechanical gaming keyboard is hitting 8ms on this test: http://blog.seethis.link/scan-rate-estimator/ http://blog.seethis.link/scan-rate-estimator/
- mlonkibjuyhv 6y ago
  I'm thinking that a debouncer might give rise to some latency when you let go of a button, or at the very least limit the shortest possible keypress. As in the first rising edge is definitely a keypress, but the falling edge is not necessarily a release.
- 6y ago