MIT Attacks Wireless VR Problem With 'Millimeter Waves' Solution

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nutjob2

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"Now, less than eight months after the magical technology of virtual reality was bestowed upon the world..."

Another Millennial who thinks the world was created the day he was born.
 

kcarbotte

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Well that's the first time anyone has ever referred to me as a millenial. lol
 

clonazepam

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I'm confused. I've seen testing on a standard PC with a wired USB mouse where they hooked up LED directly to the mouse. Then they taped the LED to the monitor. Using a high speed camera, they recorded the latency between clicking the mouse (LED light) and the action taking place on the screen.

Now we're talking about a wireless controller to the PC, and then to the headset. Also, headset movement to the PC and then back. What kind of round trips are we talking about?

I think a 60 hz monitor, v-sync with double or triple buffer sees a latency of around 140ms average. The average latency for 144fps, 144Hz vsync, double triple buffer is around 80ms or thereabouts. If you just forego vsync altogether on the 144Hz and shoot for 300fps, you're looking at about 40ms avg.

Where does all of this tech land compared to that? Perhaps they aren't even aiming for a gaming environment anyway, so it'd be fine, if a little frustrating like the latency when trying to bring up your cable or satellite service's guide.
 

none12345

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"I think a 60 hz monitor, v-sync with double or triple buffer sees a latency of around 140ms average. The average latency for 144fps, 144Hz vsync, double triple buffer is around 80ms or thereabouts. If you just forego vsync altogether on the 144Hz and shoot for 300fps, you're looking at about 40ms avg."

Just changing your monitors in your example wouldnt affect the latency numbers as much as you indicate.

60hz = 16.66ms, 144hz = 6.94ms, 300 hz = 3.33ms. In all 3 cases, with vsync, thats on top of whatever delay you get from the game engine to the graphics driver to the link to the monitor. As well as the delay from mouse click or keyboard press till the game engine registers it. Changing the monitor wouldnt affect any of that. If you have a gpu rendering 60 fps, you are seeing a new frame every ~16.66ms, but with tripple buffering its at least 50 ms old, if we had freesync/gsync throw on another 10 ms or so, if we have neither then add the above monitor numbers, then throw on say another 1/4 to 1/2 of that again for the image to actually stabilize, and say another 10ms for the mouse click or keyboard press to be recgonized by the game engine.

The 80ms guess is probably pretty good if you have a gpu rendering 60 fps and a 60 fps monitor; 10ms mouse/keyboard + 50ms tripple bufering + 16.66ms cycle time + 4 ms image stabilization + say 10 ms everythign else.

However, changing the montior only affects the 16.66+4ms number above. A 300 hz monitor would only be say 3.33ms+1.6 = 5ms, youd only save 15ms. And be about 65ms or so.

What would cut off a lot more latency would be changing the gpu to a 300 fps gpu on the same crappy 60hz monitor. Now you can cut into that huge 50ms delay in the tripple buffer and drop it to 10ms. And on the same crappy 60hz monitor you are down to a ~40ms delay. Course would make no sense to buy a gpu that can do 300fps and cheap out on a 60hz monitor!

Do both and you can could get down to about 25ms. Even tho the gpu can render in 3 and the monitor can display in 3, there are still other sources of latency you havent fixed.

Of course dont forget human reaction time, add about 250ms for average human reaction time.....so umm....oops none of the above matterd because humans arent very quick by comparison!
 

clonazepam

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Yeah, reaction time matters when doing something for the first time. It's fine until you begin predicting when to enter your input, which can be down to just a few frames. Now it matters quite a bit.
 

anbello262

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I would actually like to have a link or more info about those numbers. From my understanding, the real numbers are a lot lower than yours, but I might be believing some incorrect rumours. Still, I believe that claiming "input lag" for a simple mouse click to be over 100ms is not only far from reality. Having more than 100ms total input lag for simple mouse lcick is very easily noticeable. I think you're off by a factor of 5 at least.

Maybe, when you are saying "average" you are also taking into account very slow TVs that are not designed to be used with any kind of fast input instruction?
 

clonazepam

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I'm skeptical as well.

https://www.youtube.com/watch?v=L07t_mY2LEU

 

TJ Hooker

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Those results just don't make sense to me. Fast-sync as I understand it, and how it is explained in the video, is the very definition of triple buffering. Yet somehow triple buffering doubles input lag compared to fast-sync.

Also, he states that G-sync/free-sync add input lag, without providing any evidence/reasoning behind that. I don't think that's the case unless you're trying to drive fps higher than monitor refresh rate.

All that being said, biggest difference in input lag was only like 60 ms, which I'm pretty sure is insignificant given the limitations of human reaction time.
 

SockPuppet

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None of you seem to understand what is happening here.

In VR, you have a movement-to-photon budget of 20ms. From the time the user moves their head to the time the screen updates and fires a photon at the user's eyeball you have a MAXIMUM of 20ms. If you go over that your brain realizes that something isn't right, the most likely cause of your brain-movement disconnect is food poisoning, and then it empties your stomach in response.
 

bit_user

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Reaction time and perception are two different things. Your brain has learned how it expects the inputs from your senses to change, as you move about. When a delay is introduced, your brain senses something isn't right. That is the problem with latency.

As @SockPuppet says, I have also heard that an evolved response is nausea, due to the fact that this delayed perception is a common effect of food poisoning.
 

anbello262

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SockPuppet, I actually understand that part. I was just trying to bring attention to some unlikely high input lag numbers written by Clonazepam.

By the way, I have tested that myself, and my result (worst case scenario) was less than half those numbers, using a sub-optimal cheap 60Hz monitor (NOT TV).

I was saying that 120-150ms is WAY more than noticeable, and is really annoying even for windoes desktop.


I know that for VR, it is strongly advised to stay below 20ms, and that is really hard to do with most wireless communication methods.
 
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