4 ms·

It's a tricky thing to perceive because there's a lot of variables at play. A lot of LCD monitors have 50-75ms of input lag. That means you don't even see what

by nickjj 8y ago

It's a tricky thing to perceive because there's a lot of variables at play. A lot of LCD monitors have 50-75ms of input lag. That means you don't even see what you type until 75ms afterwards so you might not even have a chance to see how a low latency application behaves. Then on top of that, there's the human factor. Some people are just more sensitive to this sort of thing. The monitor I use happens to have about 13ms of input lag (verified with camera tests) which is pretty much as good as you can ask for with an IPS panel. I wrote all about picking monitors for programming at https://nickjanetakis.com/blog/how-to-pick-a-good-monitor-for-software-development https://nickjanetakis.com/blog/how-to-pick-a-good-monitor-fo.... The difference is night and day when typing in an application that's not efficient vs one that is. Even typing in this comment box on HN feels like I'm typing in mud because Chrome's input lag is horrendous compared to xterm, WSL Ubuntu terminal or any other application that doesn't have a million layers of UI framework abstractions piled on. If you're curious, one of the developers from the WSL Ubuntu terminal went into great detail on why their terminal is so fast. It's at https://github.com/Microsoft/console/issues/327 https://github.com/Microsoft/console/issues/327. The sad thing is, I've opened high input latency issues to a number of other terminals and the author of those terminals often come back saying "nah, your computer must be broken, otherwise everyone would be complaining" even after I supply them video proof. I guess that's what happens when you live in a world where everyone has low end monitors and are used to using Electron apps all day.

mixmastamyk 8y ago
Yep my gear, especially the dock, probably enforces a minimum latency on everything. The only time latency is noticeable to me is if I can type faster than displayed on screen. I type around 50 wpm so the computer doesn't have to respond that quickly to keep up. Online I found that equals 250 cpm, or ~4.2 cps, lets say it has 240ms per keypress to not fall behind. Plenty of time.
- wtallis 8y ago
  Your dock is a glorified USB hub, unless it's a more expensive Thunderbolt dock, in which case it's a glorified PCIe switch. In either case, the added latency is completely imperceptible to humans, and in the latter case, pretty hard to measure from userspace software. The dock is not even close to being the largest source of latency in the chain. The components that can be responsible for tens or hundreds of milliseconds of latency are the display, hard drives and overloaded SSDs, network, and bad software.
  - mixmastamyk 8y ago
    Yes, usb-c probably thunderbolt. Checked my dell external monitor, folks say they have a small lag. Don’t notice any difference between it and laptop monitor.
leeoniya 8y ago
i recently purchased a monitor and was looking for a way to figure out input lag without a camera setup. one recommendation was to test your reaction time [1] on a known low-latency display. mine old one was a 1080p 21.5" Dell IPS LCD. I was worried that a 2k or 4k display would introduce lag, though at 60hz anything within 16ms g2g will feel the same and the 1440p Viewsonic i got advertised 15ms. Best reaction time (~190ms) over multiple trials did not change after switching to new display. Not scientific, but certainly enough to catch something as large as 20ms+. [1] https://www.humanbenchmark.com/tests/reactiontime https://www.humanbenchmark.com/tests/reactiontime
- nickjj 8y ago
  For semi-new monitors you can find super in depth reviews at http://www.tftcentral.co.uk http://www.tftcentral.co.uk. They often include input lag. I highly recommend that site to get the true input lag of your monitor (without having to resort to your own tests). g2g typically measures the response time of the monitor which is a different thing than input lag. Most manufacturers won't even list input lag on their specs even though it's one of the most important attributes of a monitor since it affects everything. I could see the reaction time being a fun way to get an average with enough samples. I did 3 sets of 5 and it was 201, 194 and 196 as the average. But I think reaction time and being able to perceive input delay are different skill sets. I'm almost 40 so my reaction time sucks, but I can still notice a delay difference in apps when pressing a key.
raphlinus 8y ago
The best way to measure end-to-end latency is an Arduino with a light sensor, with the Arduino programatically injecting USB events. I made an Amazon shopping list[1] a year ago. I hope to rework my code and post a blog soon. [1] https://www.amazon.com/ideas/amzn1.account.AGSZP5AWBGH7772O35NTI7RN3JLQ/2LZEHRCO3YHSZ https://www.amazon.com/ideas/amzn1.account.AGSZP5AWBGH7772O3...
- nickjj 8y ago
  If you're into this sort of thing I recommend reading this article: http://www.tftcentral.co.uk/articles/input_lag.htm http://www.tftcentral.co.uk/articles/input_lag.htm It goes into a lot of depth on input lag and how to measure it accurately. The site also happens to have recorded input lag numbers for hundreds of monitors. In the article it mentions using photo sensors and oscilloscopes as the best way to get a reading but they settle on using a special type of stopwatch test that gets results that are nearly the same.
- nzjrs 8y ago
  I did such a thing a while ago at my last job. I guess it still works https://github.com/strawlab/lagtest https://github.com/strawlab/lagtest

by nickjj 8y ago

mixmastamyk 8y ago

Yep my gear, especially the dock, probably enforces a minimum latency on everything. The only time latency is noticeable to me is if I can type faster than displayed on screen. I type around 50 wpm so the computer doesn't have to respond that quickly to keep up. Online I found that equals 250 cpm, or ~4.2 cps, lets say it has 240ms per keypress to not fall behind. Plenty of time.

wtallis 8y ago
Your dock is a glorified USB hub, unless it's a more expensive Thunderbolt dock, in which case it's a glorified PCIe switch. In either case, the added latency is completely imperceptible to humans, and in the latter case, pretty hard to measure from userspace software. The dock is not even close to being the largest source of latency in the chain. The components that can be responsible for tens or hundreds of milliseconds of latency are the display, hard drives and overloaded SSDs, network, and bad software.
- mixmastamyk 8y ago
  Yes, usb-c probably thunderbolt. Checked my dell external monitor, folks say they have a small lag. Don’t notice any difference between it and laptop monitor.

leeoniya 8y ago

i recently purchased a monitor and was looking for a way to figure out input lag without a camera setup. one recommendation was to test your reaction time [1] on a known low-latency display. mine old one was a 1080p 21.5" Dell IPS LCD. I was worried that a 2k or 4k display would introduce lag, though at 60hz anything within 16ms g2g will feel the same and the 1440p Viewsonic i got advertised 15ms. Best reaction time (~190ms) over multiple trials did not change after switching to new display. Not scientific, but certainly enough to catch something as large as 20ms+. [1] https://www.humanbenchmark.com/tests/reactiontime https://www.humanbenchmark.com/tests/reactiontime

nickjj 8y ago
For semi-new monitors you can find super in depth reviews at http://www.tftcentral.co.uk http://www.tftcentral.co.uk. They often include input lag. I highly recommend that site to get the true input lag of your monitor (without having to resort to your own tests). g2g typically measures the response time of the monitor which is a different thing than input lag. Most manufacturers won't even list input lag on their specs even though it's one of the most important attributes of a monitor since it affects everything. I could see the reaction time being a fun way to get an average with enough samples. I did 3 sets of 5 and it was 201, 194 and 196 as the average. But I think reaction time and being able to perceive input delay are different skill sets. I'm almost 40 so my reaction time sucks, but I can still notice a delay difference in apps when pressing a key.

raphlinus 8y ago

The best way to measure end-to-end latency is an Arduino with a light sensor, with the Arduino programatically injecting USB events. I made an Amazon shopping list[1] a year ago. I hope to rework my code and post a blog soon. [1] https://www.amazon.com/ideas/amzn1.account.AGSZP5AWBGH7772O35NTI7RN3JLQ/2LZEHRCO3YHSZ https://www.amazon.com/ideas/amzn1.account.AGSZP5AWBGH7772O3...

nickjj 8y ago
If you're into this sort of thing I recommend reading this article: http://www.tftcentral.co.uk/articles/input_lag.htm http://www.tftcentral.co.uk/articles/input_lag.htm It goes into a lot of depth on input lag and how to measure it accurately. The site also happens to have recorded input lag numbers for hundreds of monitors. In the article it mentions using photo sensors and oscilloscopes as the best way to get a reading but they settle on using a special type of stopwatch test that gets results that are nearly the same.
nzjrs 8y ago
I did such a thing a while ago at my last job. I guess it still works https://github.com/strawlab/lagtest https://github.com/strawlab/lagtest