Predicting player inputs smooths streaming PC games

Everything is hosted in the cloud these days, including an increasing number of games. Heck, you can even roll your own remote gaming server and tap into it with one of Nvidia's Shield devices. The trouble is, the latency inherent to most mobile Internet connections can taint the streaming experience with certain kinds of titles. Researchers at Microsoft, the University of Michigan, and the Siberian Federal University have developed a speculative system that seems to mitigate the damage, though.

Dubbed DeLorean, the system is claimed to compensate for up to 250 milliseconds of round-trip latency. Blind-test subjects reported "only minor differences in responsiveness" between streaming Doom 3 and Fable 3 on a 250-ms connection and one with "no latency." The findings are detailed in this research paper (PDF).

DeLorean works by speculatively rendering frames based on likely player actions. These extra frames are sent to the client early, and the player's actual input determines which one is used. "Supersampling" player inputs and filtering the results reportedly improves the accuracy of the prediction engine, while "view interpolation" helps to correct the appearance of mispredicted frames. "A small amount of additional 3D metadata" packaged with each frame allows DeLorean to shift the viewport if it guesses wrong.

The system sends multiple frames to cover a range of possible outcomes, so it uses a lot more bandwidth than typical streaming solutions. Even with compression, researchers observed a 1.5-4.5X increase increase in the data rate.

Despite the bandwidth penalty, DeLorean looks promising. There's clearly room to improve streaming performance for high-latency connections. Microsoft hasn't announced plans to incorporate the research into any actual products, though. Thanks to Slashdot for the tip.

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