Console Gaming: The Lag Factor
Getting to grips with in-game latency, with help from Infinity Ward and friends.
The game is unresponsive. It's laggy. The joypad acts in a merely advisory manner. The control is rubbish. Game reviewers and players alike can be quick to put the boot into any given release - and rightly so, if it deserves it - but at the very least there should be a way of quantifying what has come to be known as controller latency. Human perception is something of an imprecise instrument, and similar to the wayward estimations of frame-rate that sometimes creep into reviews, a more scientific approach needs to be taken to get to the heart of the issue.
If cold, hard figures can be attached to specific gameplay experiences, comparisons can be made and deeper understandings can be reached. 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. The end result? Players get better, smoother, more responsive games.
"Our mantra of '60FPS 60FPS 60FPS!' would all be for nothing if we had horrible input lag," says Infinity Ward's Drew McCoy. "It is extremely helpful being able to see the physical, measurable, result of what is going on in our game - especially if things change or if someone in the office complains that things 'don’t feel right'. If anyone cares about the end user experience of their game, they should be heavily invested in their input latency."
Criterion senior engineer Alex Fry concurred in our expansive Burnout tech interview. "We try to get the latency down to the lowest possible, because it's just a better experience. It's one of the reasons Burnout runs at 60FPS."
In basic terms, controller latency is very easy to define. It's the time, usually measured in frames or milliseconds, between pressing the button on your controller and the appropriate action kicking in on-screen during gameplay. The longer the delay, the less responsive the controls, and the more unsatisfying the game can feel.
Methodology for measuring gameplay lag is remarkably straightforward and was first put forward by Neversoft co-founder Mick West in this Gamasutra feature, which combined the explanation of his techniques with measurements for a number of the most popular video games. Getting a very close reading really is very simple: stick a camera capable of recording at 60FPS in front of a monitor and record the gameplay while getting the controller in the same shot. West used a Canon digicam to do the deed, while I went for a Kodak Zi6 for its cheapness and 720p60 HD capabilities. Once you've recorded your clips, simply count the frames between the button press and the resulting action on-screen. As each frame remains on-screen for 16.67ms, simply multiply that by the number of frames and - boom - that's your latency.
Of course there are complications to the basic theory. LCD displays have lag of their own. Processing and scaling can take anything up to five frames depending on how aged and decrepit your flatscreen is. West's solution was ingenious: get a baseline measurement using a CRT screen (no latency there) and use the same measurement to factor out the lag of your flatscreen. With that in mind, I was able to see that my old, but still brilliant, Dell 2405FPW lags to the tune of three frames (50ms!) running at 720p, and two frames at 1080p (not surprising really as 1080p is far closer to the screen's native 1920x1200 resolution). Nice screen, pretty awful latency.
As Neversoft itself is responsible for most of the latest Guitar Hero games, where latency is hugely important, it is perhaps not surprising that Mick West took such an interest in this subject, and his conclusions are intriguing.
- The lowest latencies a video game can have is 50ms (three frames) - the PS3 XMB runs at this rate, but few games reach it.
- Most 60FPS games have a 66.67ms latency - Ridge Racer 7, for example.
- 30FPS games have a minimum potential lag of 100ms, but many exceed this.
- Game developers should test their own games using the camera technique in order to weed out bugs - West says that Heavenly Sword's response slows down to 300ms just by turning the character, and reckons it's a technical issue that should have been resolved before going gold with the game.
- Citing GTAIV as an example, West suggests that a 166ms response is where gamers notice controller lag, which could also explain the Killzone 2 furore too.
- Game reviewers should accurately measure latency for their reviews where controller lag is an issue, in the hope that sloppy game response times come under far more scrutiny.
Taking West at his word on that last point, I decided to give it a go and while initial testing was successful, I soon ran into a pretty big problem, as EG comment writers predicted I would. While the methodology is absolutely sound, the issue in frame-counting is all down to where the "zero frame" is: that is, the point at which the joypad button is fully depressed, and where you need to start counting from. I found the only way to verify results was to continuously test them again and again until a common result becomes apparent. Here are my initial efforts, using Killzone 2.
The video counts the frames for you, but all results need the three-frame lag of the display subtracted. In this case, Killzone 2 appears to have a 12-frame lag from button press to action on-screen shown here firing the gun. But judging the zero-frame is difficult so the measurement is only 'ballpark'...
Based on this video, we see that the lag in the fully patched Killzone 2 is 12 frames. Factor out the three frames of lag in the display itself and we're left with a 150ms "ping" between gamer and on-screen action. Now, many people have complained about the unresponsive nature of the controls in Guerrilla Games' epic to the point where the game was patched (this is captured from the latest code by the way), though based on my experiences I believe the analogue "dead zone" on the sticks was the main focus of the tweaks.
But the hassle in just getting one measurement I was reasonably happy with (but not 100 per cent confident in) was enough to give me pause. On a feature where accuracy really had to be second to none, I didn't feel I could proceed without a rethink.
Thankfully better minds than mine had done the thinking for me. Infinity Ward - creators of the Call of Duty franchise - loved Mick West's feature, and had used his techniques for eliminating unnecessary lag from their games. They too sought to improve the methodology, removing the zero-frame issue from the equation and making the whole exercise somewhat easier into the bargain.
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Comments (66) 2 years ago
Comments threads automatically close after 30 days, but please feel free to continue chatting on the forum!
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60FPS, 60FPS, 60FPS, 60FPS, 60FPS, 60FPS, 60FPS, 60FPS, 60FPS, 60FPS, 60FPS!!!!!!!
But congrats also to Halo 3 and BioShock on their relatively low 30FPS lag. Nicely done.
GTA, you'd better improve next time....
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Could you perhaps test Gears of War too? This would be a very interesting part of future reviews/previews.
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Nonetheless an interesting read
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I'd really like to see something like this measured on the Wii. I've found the wands to be very 'wooly' on some games and spot-on in others, and that's without the dongle attached. Wii Sports for example - the baseball bat seems have hardly any latency (at least until the ball is thrown) but boxing and tennis can be ropey. Does the dongle reduce latency at all, or does it really just add another gyro (or whatever)?
I know you can neutralise lag simply by anticipating delay, but what really makes some games a nightmare is inconsistency. Maybe developers would do better to concentrate less on delivering rock-sold 60 or 30fps, and concentrate on delivering consistent lag first. Once you know that a game is always going to show a fixed delay to your input, you adapt and then forget about it.
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And, of course! Pleeeaseeeee Richard, could you measure the display latency of some LCDs around the office? New models, old models, cheaper models, those sort of geeky things that give us some idea in other to decide which brand is good for gaming. The famous "Game Mode" could be put to test also.
Edit: Format.
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Oof @ the gta latency. I always put the sluggishness down to the relatively low fps. Its definately more noticable in an fps like kz2.
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Yes they are, if not they would be quite useless in racing games as accelerator/brake
The bumpers are not. The face buttons are tricky, they feel a little loose and could give the impression that are analogue, but I don't think they are, in any case I haven't found any game that felt like they were. Didn't the PS2 have analogue face buttons?
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Yep they do, and so do ds3's
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Well done!
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Yet another reason why 60fps is important and on current gen consoles every game should have it. On the PC I always adjust the graphics so I get a steady 60.
Some of the games listed fare very poorly. Was not surprised to see GTA4 didn't fare well. It felt horrible to me.
Would be VERY interested to get accurate latency marks for Killzone 2, to see if it really was "weight" as many fans claimed, or just high latency. I suspect the latter personally.
Forza does quite well, which is good for a realistic racer. Would be interesting to see how GT5 fares.
Great to see these things measured in ways that can't be disputed. Removes another argument between fanboys.
@Dill_Doe and Nephirion, hilarious. Just proves how many people comment without reading the content. Why do you even bother visiting the site?
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For example, Wii sports Tennis again - I thought it was going to be 1:1 mapping when I first got it, but 'spin' turned out to be a choice of only three options - no spin, a single degree of topspin or a single degree of slice. So, the wand provides full feedback but the game will only interpret that feedback in one of three way ways. Anyway - a bit off-topic. And a bit nerdy.
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Good to see some tests though, even if they are a bit rough around the edges.
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Also might be down to monitor thourgh as my pc has a very nice benq monitor with 4ms latency i think , but my TV downstairs is a couple years old Sanyo lcd.
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Yeah I think the PS2 did, at least I remember in MGS2, if you lightly held the square button you'd aim and if you pressed it harder you'd shoot.
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Yeah, measurements on the Wii would be interesting to see, especially on stuff like pointer movement, probably not so much on gestures (after all the detection for those is pretty damn floaty anyway).
Bremenacht: I guess more than three lights would be impractical to build and unnecessary, while fine differences may be recognized by the game you probably won't see them quickly reflected ingame anyway.
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:'-D
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In all seriousness, game latency between controller press and resultant action on screen IS very heart of what makes game great or just good. The lag in Killzone 2 and Inc deadzone is what 'lessen' the potentially great game to a visually nice game with control issues. If latency was shorter then no doubt my appreciation would have been better.
Same for gta4, control lag made some combat setpieces more difficult than it need be.
So if devs focus on keeping control lag short and fps to reasonable level, then that would make a difference to how playable or frustrating a game is. Don't just use latency for false difficult spikes or saying it is to impart weights!
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Lag can be introduced for a myriad of reasons, many of which are more significant than input latency, and when all's said and done if you don't like the way a game "feels", putting a number to it isn't going to soften the blow.
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If you read the comments, it seems that the fanboys didn't read the article anyway!
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Would it be possible to see some pc game results next time? and, as someone has already said it would also be nice if you could test some hdtvs and monitors someday, to see which ones are adding 5 frames and which add one or none at all... it doesn't seem as if we have that many ms to spare
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No its not, its bullshit.
Feels overly twitchy, feels really good, feels laggy. That's all you need to know.
Offline its the same for everyone, so its a level playing-field.
Online it doesn't matter how razor-sharp YOUR controls feel if you are seeing where your opponents were a second ago!
And besides, the single biggest cause of "laggyness" is shitty game-design where actions are animation dependent, so you need to watch all 100 frames of that lovely muzzle-flash and recoil before you can fire again.
If you want bleeding-edge responsiveness all you need do is run your simulation at a higher frequency than your rasterizer. This is what's meant when people talk about their code always running at 60hz internally irrespective of frame-rate, which should be standard practice in these days of multi-threaded programming.
The reality is that if you are waiting for visual feedback then, yes, of course a higher framerate will give you that feedback sooner. But that isn't measuring LAG that's measuring frame-rate! It doesn't matter that you didn't see the first frame of the bullet exiting the muzzle of the gun, so long as the simulation knows when it happened.
This is a complex technical issue (actually many issues depending on application) that's being simplified to the point of misrepresentation. Its classic junk science. Sorry.
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Also Richard, you might want to go into the fact that lower-res games have higher lag on HDTVs. PGR3 and Halo 3 feel nearly unplayable to me on my 1080p native, and I don't think it's a coincidence that they both can't even manage 720p.
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No it doesn't soften the blow. But it allows us to know weather there is an underlying issue with the game or not.
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In any case, there is one thing that can be easily measured: The time elapsed between pushing the button and the action on the screen, which is what this article is about. Maybe the underlying reasons given are not accurate, but the bottom line conclusions hold: Some games such as GTA4 feel sluggish and the frame counting shows that the engine is just taking too long to show in screen what the player is doing.
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Hopefully they'll have this sorted for the sequel.
edit:
That GreyBeard person is hilarious. If Halo had a 200ms lag, and Killzone a 67ms, then he'd be preaching about how essential low controller lag is to an enjoyable gameplay experience.
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Yeah, because every second counts when you could instead be trolling the comments section of EG.
*snore*
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And no, I'm not related to any of them
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Just another idiot fanboy, then.
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Both great games, but I always feel detached from the controls. I could be wrong, but input lag doesn't seem to be high on DICE's agenda.
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But, consider this: latency is one thing, but human perception and therefore reaction time adapts itself to the given circumstances (by means of prediction) . This implies that it is possible players can bridge different "lag gaps" (small/medium/large) and still get a similar result in final performance because the mind adapts to the laggy situation and compensates. So, together with this technical research, one should also take into account the human factor. Finally, reaction to lag is subjective: different people will react differently to a same amount of lag. It is this result of [lag + personal reaction/prediction] that is experienced by the player. Constant adapting of the players reaction to what he predicts the amount of lag will be.
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It'd be nice if df came up with a standard set of tests (including lag) that can be attached as a boxout to eg reviews.
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I don't know about GTA IV though...don't remember noticing that much lag when i played it...but that was ages ago. Anyway...good article...will be interesting to see this with a game running online as well.
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1 point which may be of use.
I work in games and make fx like muzzle flashs. i know with our engine there is a 1 frame delay between asking a particle system to emit a particle and and a particle being emitted. If other gmaes engine have the same approach then that might mean the response time might be 1 frame less than it looks like on screen.
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Anyway.
@a.j2020
I mean at first when i played killzone 2 it felt very slow in response time but then i grew used to it and I personally think that slowness adds to the experience.
How can lag possibly add to the experience. If you are a firing a real gun is there a pause between you thinking of firing a gun and actually pulling the trigger?
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And it's a good article. You should read it.
Really, go ahead. It even has some videos in it
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My enjoyment of oblivion on the ps3 was ruined because the deadzone and the progression from turning slow to fast based on how far the stick was pressed was rubbish. It meant that I couldn't play as an archer character. (I've played it on 360 but it looks horrible on the 40" tv I got after the game, and on PC the game frame skips like crazy)
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<a href="http://www .youtube.com/watch?v=d_9vyjmEMbc
">http://www .youtube.com/watch?v=d_9vyjmEMbc
</a>
(My own engine responds withing one frame.)
Unfortunately in games there is enormous input lag. :/
<a href="http://www .youtube.com/watch?v=YtjzcmliDkw
">http://www .youtube.com/watch?v=YtjzcmliDkw
</a>
(Farcry 2)
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"gta4 used deferred lighting like killzone 2 and both games have pretty significant input delay because of it."
Care to elaborate on this? How exactly does deferred lighting in a (nominally) 30fps shooter increase input delay?
Input delay is a function of:
- polling or event receipt (which can be done multiple times per "frame"
- game-logic response (the first available opportunity that the game gets to respond to the polling),
- physics/motion/camera response (what objects move as a consequence of the input?),
- visual & audio response (what does the user see/hear in response to the input, how long does the animation/sound take?)
- frame rate (what is the minimum delay before responses can be shown).
So how does a deferred renderer increase input lag? Yes, deferred rendering has an impact on overall processing and the frame-rate, but that's true of any renderer. The renderer is just one component in a chain of time-draining activities.
BTW, I'm NOT defending KZ2's input lag here. I find it's not acceptable. But I don't believe their choice of render is the issue.
BTW2, KZ2 uses a variety of renderers, for the job at hand. It doesn't always use a deferred renderer.
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Or Quakeworld at 300+fps on a 200hz CRT
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Also, how does this affect PC gaming? If you tell your video card to output the same resolution as is native to your LCD monitor, does the latency go away completely? Or is there still some inherent latency even without having to scale the image?
I guess it's a little disappointing... my awesomeness at twitch shooting in CoD4 may be down not to the fact that I have supernatural reflexes, but to the fact that I use a CRT and my opponent uses an LCD, so even if we both show a 30ms ping to the server, he may be another 10th of a second or more behind me
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Do you mean server to client? And can you explain what you mean here in general, regarding cloud gaming and this latency helps it?
"But in the meantime, while overall "pings" between console and gamer remain rather high, the bottom line seems to be that players are now used to it, to the point where developers - like Infinity Ward - centred on getting the very lowest possible latencies are using that to give their games an edge over the competition. Call of Duty's ultra-crisp response is one of the key reasons why it's a cut above its rivals, and it's a core part of a gameplay package that will once again top the charts this Christmas."
Just a side question, but do the PC versions of Call of Duty have the same low internal input lag?
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In GOW, you've got a lot of interruptible animations - so when you hit block, it cancels out of whatever you're doing and you block. That's good - how it should work the vast majority of the time. In worse games, like Star Wars: The Force Unleashed, they force you to play through the whole animation before blocking. If you think the difference between 50 and 150ms is bad, the difference between 50ms and 3 SECONDS is a billion times worse.
I can't even play those kinds of action games anymore unless they allow move-canceling - the controls feel utterly broken. It'd be really interesting to get a good overview of which action games have properly designed systems... and which are garbage.