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Linus Tech Tip - Steam Link confusing input lag math.

PostPosted: 20 Apr 2016, 12:19
by lexlazootin
Linus Tech Tip recently released a video going over the Steam Link and the shortly going over the input lag of the device. At this point i kinda expect for him too get this sort of information wrong TBH but i can't figure out for the love of jebus what these graphs are trying to show.

https://youtu.be/mliW5zppm00?t=6m33s

He says he's using a 240fps camera and then shows how many frames he took the 'Mouse click' to register a shot on the screen. for "Client" and "Server" which i have no idea what that means. And then says the server has 3.12Milliseconds of lag and the Client has 5.76?

WHAT? i can't figure out what he is trying to say at all...

Maybe some else can make sense of it.

Re: Linus Tech Tip - Steam Link confusing input lag math.

PostPosted: 21 Apr 2016, 06:21
by Sparky
It looks to me like whoever did the graph screwed up the calculation.


I'm assuming:
Client would be the input latency measurement of the monitor plugged into the steam link.
Server would be the machine the game is running on.
Frames on the first graph is number of video frames from their 240fps camera.


Now, 1/240 of a second is 4.16 milliseconds. That makes the 13 and 24 frames from the first graph translate to 54ms and 100ms respectively. For CS:GO that's ridiculously high(in both cases). Their milliseconds graph would require a framerate of 4166.6 to match up to the data in the previous graph.

Basically instead of dividing by .24(frames per millisecond), they multiplied by .24

Re: Linus Tech Tip - Steam Link confusing input lag math.

PostPosted: 10 May 2017, 12:53
by RealNC
They should have used their 960FPS camera. They have one. They didn't use it.

240FPS is just not good enough for this.

Re: Linus Tech Tip - Steam Link confusing input lag math.

PostPosted: 11 May 2017, 14:38
by Chief Blur Buster
(To be nicer than y'all). I enjoy watching Linus, but *ahem* I do humbly think this test was flawed in certain ways.

(Nonwithstanding the math calculation errors by his assistants. Ugh).

While 240fps is not 100% useless (considering 100-200ms buttons-to-pixels chain of modern games running at low frame rates), the error margin is rather huge and I imagine that there are also calculation errors adding to the mix. You can get some very granular lag test results with a 240fps camera, but the error is very huge (+/- 4ms).

With the error margin increasing if you've got CMOS camera sensor scanout inaccuracy (different part of photograph is 1/240sec different from another part), i.e. not keeping lag test on the same CMOS sensor scanout orientation (proper camera orientation to eliminate scanout error). Ouch.