Living with lag

We put this video up on our various social media sites earlier in the week (here’s our Facebook page, if you’re not familiar with it yet: we’re also on G+ and Twitter if you’d like to chat), but so many of you have emailed me about it since then that I’m giving it a spot here, too. Ume.net are a Swedish broadband provider, and they conducted this experiment to demonstrate just how sucky lag would be if you had to put up with it in real life, using an Oculus Rift headset and a Raspberry Pi. In the end, this is just a piece of advertising: but it’s a beautifully realised project which made us laugh, and if my inbox is anything to go by, it seems that a lot of you liked it too. Enjoy!

12 comments

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Craziest part of that video for me came at the end… Gigabit Fiber! Are the Swedes actually getting that to the home?!

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In answer to my own question, they DO for between 599 and 725 kr!

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The bit with the eggs is my favourite – had me giggling like a loon the first time I watched it :-D

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Do people adapt to the lag in time?

Experiments of 1960s/70s with mirror-reversing vision caused initial confusion and then the subjects adapted. This included playing pingpong and riding a bike, threading a needle etc.

Soldiers adapt their vision so that they can integrate their right eye through a magnifying optic sight and the un-mangified left one. Takes a little practice and you feel drunk when you try, then it becomes easy, and really useful.

Admittedly this is spatial rather than temporaral shifting.

Our brains have a lag built in anyway, so maybe we can just change a few configs and we work normally.

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Even if people could adapt to lag, it only works in cases where you can extrapolate events. In the case of playing ping pong, it may be possible for a person to project the motion of a ball after it is hit. It would be impossible to extrapolate the path of the ball prior to it being hit. Since ping pong balls can travel rather quickly, and considering the typical amount of lag I see online, it is probable that the ball would have already passed the opponent before they even saw the serve (i.e. it would be impossible to adapt to the lag).

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Batsmen extrapolate quite happily. The ball takes about half a second to get from the bowler and if it bounces he has even less time to track the ball. So he has to use his experience to predict where the ball will be when it gets to him.

Most of the time he gets it right. Clever bowlers of course attempt to trick him to the wrong choice.

Martial artists and many other people use fairly open-loop control to perform their actions. A bit like with American football, they look at the situation and decide on a “play”. By the time it eventually happens many 10s of ms later they have to hope they made the right punt. If you are dan grade then you get it right most of the time.

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Absolutely. When training with a medieval longsword I’ve found that there is (subjectively) absolutely no time (in reality there’s a dinky little bit of course) between your opponent starting to strike and the blade landing on target, yet you have to react. You can predict the type attack they will do based on their feet, arm and blade position, ie: stance.

However if you spend time consciously analysing the above you’ll get hit. Best thing is to be prepared and let your brain do what it does best: calculate without conscious effort.

Curiously the opposite is true as well: if you consciously think “I’m going to strike his shoulder… that means I have to stand like this and hold the blade at this angle before I strike” then this will slow your attack down to the point where an experienced opponent then has more than enough time to prepare to parry and counter.

And when you get it wrong… *shrug* that’s what the steel plate armour is for :)

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“When training with a medieval longsword I’ve found that…” wins this comments section’s award for the best opening of a sentence this year. (There is no prize.)

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“Just edit the config.txt on your /brain partition…” ;-)

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Adapting to lag means being able to predict the future. If it’s the position of your own arms/legs, maybe you can rely on your own immediate feel of things. For short times (< 1 second) you can extrapolate from past ("current") direction and velocity, but that is increasingly inaccurate as the time lag increases. This is the classic sensor integration problem in inertial navigation.

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The food bits remind me of watching a baby/toddler feeding themselves, you think that their coordination gets better as they age, perhaps it is lag which is decreasing as brain gets wired.

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I am not even worried about ‘lag’ at the moment – not unless ‘lag’ describes the rubbish connection speeds available to us in third-world UK.

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