Measuring Input Latency In Console Games

The Digital Foundry blog has an article about measuring an important but often nebulous aspect of console gameplay: input lag. Using a video camera and a custom input monitor made by console modder Ben Heck, and after calibrating for display lag, they tested a variety of games to an accuracy of one video frame in order to determine the latency between pressing a button and seeing its effect on the screen. Quoting: "If a proven methodology can be put into place, games reviewers can better inform their readers, but more importantly developers can benefit in helping to eliminate unwanted lag from their code. ... It's fair to say that players today have become conditioned to what the truly hardcore PC gamers would consider to be almost unacceptably high levels of latency to the point where cloud gaming services such as OnLive and Gaikai rely heavily upon it. The average videogame runs at 30fps, and appears to have an average lag in the region of 133ms. On top of that is additional delay from the display itself, bringing the overall latency to around 166ms. Assuming that the most ultra-PC gaming set-up has a latency less than one third of that, this is good news for cloud gaming in that there's a good 80ms or so window for game video to be transmitted from client to server."

Comments

Re:DDR?

[bjorniac]

DDR or any rhythm/timing based game will be perfectly fine with a fair amount of lag so long as the lag is consistent. The game isn't based much on reaction times, more hitting the pads at the right intervals. Once you get accustomed to the lag (which should happen naturally as you dance) the actual amount won't matter so much - you just have to move 160ms before the arrow hits the circle or whatever, something you will have been doing already, moving to land on the beat, rather than waiting for the beat and then moving. This differs from, say, a shooter like counter-strike, where you have to react as fast as possible to what is a non-rhythmic, supposedly non-predictable event (unless the opposing team comes out in synchronized swimming formation).

Inconsistency in lag would be a killer here, as it is everywhere, as it would be essentially adding a random component to your timing that you have no control over. But any time you do rhythmic work you're doing predictable lag compensation already - eg clapping on the beat requires you to start the motion before the beat happens rather than react to it.

Re:Reality check

[sahonen]

Actually, raw reaction time, which doesn't even change too much between 20 and 30, is not the primary element of skill at first person shooters. I've looked at the raw reaction time (i.e. click your mouse when you see a light turn on) of many gamers, some who absolutely dominate me and some at or below my level, and there was no real correlation between that reaction time and skill. From what I've gathered, I've determined that skill at FPS games is more a function of experience and training rather than raw reaction time.

The basic categories that set an elite gamer apart from an average or newbie gamer go something like this:

Predicting your opponent and being unpredictable yourself: Knowing where your opponent is going to be, and acting in a manner that your opponent can't predict. If you can put your crosshair where you know your enemy is going to be, and he can't do the same, you're going to win even if he has better raw reaction time than you. This is a function of experience with the game.

Decision making: Evaluating the importance of the various high-level goals in the game, deciding which ones to prioritize, and acting on that decision. Making better decisions, making them faster. Again, a function of experience with the game.

Aiming skill: If an enemy appears on your screen away from your crosshair, how quickly and accurately you can move your mouse to put the crosshair over him. This is a function of training, learning exactly how much mouse movement corresponds to how much movement on screen, and being able to precisely produce that movement with your hand. This is often confused for reaction time when watching people play, but really, the reaction time component is only in seeing the enemy and deciding to shoot him. The rest is muscle memory.

This is where input lag really hurts, it's very very important that your field of view appears to correspond to your mouse movements with absolutely no lag. Console games don't suffer from this because aiming with console controllers is far less precise than using a mouse, so the input lag "hides" behind the imprecision of the joystick. When the game meets the PC where people are using mice, the lag between moving your mouse and your on screen view changing becomes perceptible.

Movement skill: The ability to manipulate your controls to allow you to travel faster. Not just finding the most efficient routes, but being able to use quirks in the game's movement code to give yourself more velocity. Another function of training, getting the control inputs just right can be difficult to master.

Teamwork: In team-based games, communication, chemistry, planning, and effective group decision making.