Find: Microsoft’s predictive modeling reduces latency in online gaming

Prediction to compensate for input lag goes back to flight simulators. The problem is misprediction, which is worse than lag itself. The idea of rendering several future possibilities and choosing the most accurate when input is finally known is clever; it'd be good to learn how much this reduces the harm misprediction causes. 


How Microsoft’s predictive modeling could make streaming gaming tolerable
// Ars Technica

A timeline comparison between a simple streaming game server setup (left) and the DeLorean system with predictive modeling (right)

No matter how fast your Internet connection is, streaming game services like OnLive and PlayStation Now always bump up against a hard latency limit based on the total round-trip time (RTT) it takes to send user input to a remote server and receive a frame of game data from that server. The hope for these systems is that broadband speeds and server connections will eventually improve enough so that trip is quick, to the point of being nearly unnoticeable for end users. Until then, a team at Microsoft research seems to have done an end run around the RTT latency limit, using predictive modeling to improve apparent performance even when the server trip takes a full quarter of a second.

Late last week, Microsoft released a paper detailing the development and testing of DeLorean, a system that uses a number of techniques to mask the inherent latency between the server running a streaming game and the user giving inputs at home. The main technique involves future input prediction: by analyzing previous inputs in a Markov chain, DeLorean tries to predict the most likely choices for the user's next input (or series of inputs) and then generates speculative frames that fit those inputs and sends them back to the user.

By the time those predicted frames get back to the user, the system can see which input was actually entered, then immediately show the appropriate predicted frame for that situation rather than waiting for another round-trip to the server. The DeLorean system also improves performance by "supersampling" inputs at a faster rate than the game normally does, and it applies a Kalman filter to reduce the shakiness of the predicted frames.

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