4 ms·

> Humans can’t notice 100ms or 200ms latency Yea, author never played MMOS or FPS games online? Going from 20ms to 100 is going to be VERY noticable.

danpalmer 4y ago
Games are a bit different – how the latency is measured depends on the game, and typically doesn't account for the rendering or local state update required to render correct data, may not account for the server's computation of the new state, won't account for input latency, etc. I agree that it's very noticeable in games, but a quoted 20ms network latency on a game could probably be anywhere from 40 to 200ms of effective latency, so I don't think they're a great example to use here.
- orbital-decay 4y ago
  What absolutely everyone is measuring today in games is motion to photon latency, with the help of a high-speed camera. This is the only thing that actually matters, along with motion-to-photon over network (with RTT measured separately), so you can tell how well both client-side and server-side parts are optimized, how high the server tick rate is etc. For the server part, different actions such as movement or attacking could even have wildly different latencies, depending on how it's implemented in the code. The most responsive games achieve sub 30 ms motion to photon locally, with proper hardware.
acdha 4y ago
The linked comment is poorly written — that is actually the claim which the author of that comment is arguing _against_. He has the correct answer which is that you need to be somewhere around 10ms to be imperceptible but explains where some of the different claims are coming from. There are a number of confounds for measuring things like this because we're often not talking about exactly the same thing: for example, the times needed to perceive motion, size, color, orientation, and recognize something are all different (to a first approximation, the relative latencies are roughly what you'd expect if the most important selection criteria was a relatively weak fructivorous ape trying not to get eaten) and there are measurable differences between how you respond to things you're predicting will happen, continuous motion, or truly unexpected events. This also varies considerably for novel and trained behavior — e.g. if you're waiting to shoot when you see a pixel change, your body is primed and presumably quite well practiced vs. something random happening in a video. All of that means that something like extra keyboard latency is especially noticeable because you're initiating the action, it's extremely practiced, and you thus have a well-honed expectation for when the response should be visible

danpalmer 4y ago

Games are a bit different – how the latency is measured depends on the game, and typically doesn't account for the rendering or local state update required to render correct data, may not account for the server's computation of the new state, won't account for input latency, etc. I agree that it's very noticeable in games, but a quoted 20ms network latency on a game could probably be anywhere from 40 to 200ms of effective latency, so I don't think they're a great example to use here.

orbital-decay 4y ago
What absolutely everyone is measuring today in games is motion to photon latency, with the help of a high-speed camera. This is the only thing that actually matters, along with motion-to-photon over network (with RTT measured separately), so you can tell how well both client-side and server-side parts are optimized, how high the server tick rate is etc. For the server part, different actions such as movement or attacking could even have wildly different latencies, depending on how it's implemented in the code. The most responsive games achieve sub 30 ms motion to photon locally, with proper hardware.

acdha 4y ago

The linked comment is poorly written — that is actually the claim which the author of that comment is arguing _against_. He has the correct answer which is that you need to be somewhere around 10ms to be imperceptible but explains where some of the different claims are coming from. There are a number of confounds for measuring things like this because we're often not talking about exactly the same thing: for example, the times needed to perceive motion, size, color, orientation, and recognize something are all different (to a first approximation, the relative latencies are roughly what you'd expect if the most important selection criteria was a relatively weak fructivorous ape trying not to get eaten) and there are measurable differences between how you respond to things you're predicting will happen, continuous motion, or truly unexpected events. This also varies considerably for novel and trained behavior — e.g. if you're waiting to shoot when you see a pixel change, your body is primed and presumably quite well practiced vs. something random happening in a video. All of that means that something like extra keyboard latency is especially noticeable because you're initiating the action, it's extremely practiced, and you thus have a well-honed expectation for when the response should be visible