Toward Immersive Mobile Virtual Reality

Virtual reality head-mounted displays (VR HMDs) are attracting users with the promise of full sensory immersion in virtual environments. Creating the illusion of immersion on HMDs requires high framerate, low latency, and high visual quality - a tall order for mobile device-based VR approaches. In this talk, I will discuss two systems we have built to overcome the inherent limitations of mobile VR. The first, Outatime, focuses on compute offload via app streaming, an emerging app execution model in which remote rendering servers stream interactive video to thin clients. While servers dwarf mobile devices in compute power, the key challenge is coping with network latency. I will discuss how we have employed speculative execution to overcome this challenge on high-quality VR games. The second system, Flashback, aggressively precomputes all possible images that a VR user might encounter well ahead of time. During run-time, Flashback indexes into the device's storage hierarchy to quickly lookup images that the user ought to be seeing. Flashback not only works for static scenes, but also for dynamic scenes with moving and animated objects. We observe substantial improvements in framerate, latency and energy consumption. In some cases, it even delivers better framerate and responsiveness than a tethered high-end computer.