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[AnandTech] Input Lag

post #1 of 67
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http://www.anandtech.com/video/showdoc.aspx?i=3601

Quote:




In gaming, input lag is defined as the delay between the when a user does something with an input device and when that action is reflected on the monitor.

The definition is straightforward, but the reality of input lag is much more subtle than may readily be apparent. There are many smaller latencies that contribute to the overall whole of input lag and understanding the full situation may prove beneficial to gamers everywhere.

The first subtlety is that there will always be input lag. Input lag is an unavoidable reality that can only be minimized and never eliminated. It will always take some amount of time for input data to get to the software and it will always take some amount of time for the software to use that data to display a frame of animation on the monitor. Keeping this total time as low as possible is a key mission of hardcore twitch gamers out there.

This article will step through all the different contributors to input lag, and we'll give some general estimates on the impact of each different contributor. Exact numbers will vary widely with different hardware and software combinations. But knowing where to focus when optimizing for input latency should help those who are interested.

After drilling down into the causes of input latency, we will provide a few examples of different hardware and settings in our lab. The extra twist is that we will be evaluating actual input latency using a high speed camera to count frames between input activation and monitor response. We'll be looking at three different games with multiple settings on both CRT and LCD monitors.
A refresher on input lag and some good numbers.
Edited by DuckieHo - 7/16/09 at 12:36pm
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post #2 of 67
Neat article, going to have to read the whole thing. Input lag is why I dont do vSync.

Just a note, the last page of the article has a VERY interesting link,

http://www.ngohq.com/news/15043-how-...vista-7-a.html

Lets you overclock your mouse on Vista/W7 x86 AND x64, include a program that lets you patch your own drivers on W7! FINALLY! Bypass driver signature check, lets you OC your mouse (my G5 was at 500), and remove watermark, and finally check your rates after.
Edited by DarkNite - 7/16/09 at 1:06pm
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post #3 of 67
Quote:
Originally Posted by DarkNite View Post
Neat article, going to have to read the whole thing. Input lag is why I dont do vSync.
vsync=input lag?
i vsync all my games,can't stand tearing.
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post #4 of 67
VSync is a monster. Easy to cut out too. Definitely continuing my do-not-touch policy for it. Although i wish gaming mice were purpose sold for lower latency. Their latencies are never advertised.
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post #5 of 67
but isn't vsync smoother? does it really matter? I'm just really a noob
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post #6 of 67
I don't really understand how vsync creates more input lag... doesn't it just lock the frames to a certain multiple of your refresh rate?
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post #7 of 67
People who feel input lag when they use vsync should turn on triple buffering. It really helps (and would also explain why some people, me included, have never experienced noticeable input lag after turning on vsync).

I can't find it right now, but there was an image that showed normal vs double buffering vsync vs triple buffering vsync.

It had 3 sections, each showing 3 frames. The normal section had tearing. The double buffering section had no tearing, but the first frame was a dupe. The triple buffering section showed 3 unique frames, tearing-free.

Quote:
Originally Posted by aaronman View Post
I don't really understand how vsync creates more input lag... doesn't it just lock the frames to a certain multiple of your refresh rate?
It's not literally a lock. It seems that's happening, but it's a bit more complicated. Read the name literally - it synchronizes your GPU with the monitor's refresh rate, so that whenever your monitor polls your card, there's a full frame in the buffer. It introduces (adaptive) delay to the GPU's render chain to achieve this, and triple buffering helps lots with this (although it consumes more memory).

The lower your FPS, the bigger the delay has to be. Fortunately, you only really need vsync when your FPS is absurdly high.
Edited by Coma - 7/16/09 at 12:53pm
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post #8 of 67
Quote:
Originally Posted by Licht View Post
VSync is a monster. Easy to cut out too. Definitely continuing my do-not-touch policy for it. Although i wish gaming mice were purpose sold for lower latency. Their latencies are never advertised.
I'd rather not have tearing\\jumping with the downside of more "laggy" game.

On games with great engines (Crysis, COD, Source games), you really don't get tearing because you don't have to enable Vsync, and don't really get tearing from that.
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post #9 of 67
Thread Starter 
Quote:
Originally Posted by Licht View Post
VSync is a monster. Easy to cut out too. Definitely continuing my do-not-touch policy for it. Although i wish gaming mice were purpose sold for lower latency. Their latencies are never advertised.
Does not matter as the USB polling rate is a 2-3 order of magnitudes longer.
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post #10 of 67
Quote:
Originally Posted by Fox_Smash View Post
vsync=input lag?
i vsync all my games,can't stand tearing.
Same here. Not sure how people can even play without Vsync with all the tearing when you move quickly.

I assume you force Triple Buffering in the Video drivers? I've only seen it on a few select games in the in-game options
Edited by citat3962 - 7/16/09 at 12:49pm
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