LiveDeep: Online Viewport Prediction for Live Virtual Reality Streaming Using Lifelong Deep Learning

Live virtual reality (VR) streaming has become a popular and trending video application in the consumer market providing users with 360-degree, immersive viewing experiences. To provide premium quality of experience, VR streaming faces unique challenges due to the significantly increased bandwidth consumption. To address the bandwidth challenge, VR video viewport prediction has been proposed as a viable solution, which predicts and streams only the user's viewport of interest with high quality to the VR device. However, most of the existing viewport prediction approaches target only the video-on-demand (VOD) use cases, requiring offline processing of the historical video and/or user data that are not available in the live streaming scenario. In this work, we develop a novel viewport prediction approach for live VR streaming, which only requires video content and user data in the current viewing session. To address the challenges of insufficient training data and real-time processing, we propose a live VR-specific deep learning mechanism, namely LiveDeep, to create the online viewport prediction model and conduct real-time inference. LiveDeep employs a hybrid approach to address the unique challenges in live VR streaming, involving (1) an alternate online data collection, labeling, training, and inference schedule with controlled feedback loop to accommodate for the sparse training data; and (2) a mixture of hybrid neural network models to accommodate for the inaccuracy caused by a single model. We evaluate LiveDeep using 48 users and 14 VR videos of various types obtained from a public VR user head movement dataset. The results indicate around 90% prediction accuracy, around 40% bandwidth savings, and premium processing time, which meets the bandwidth and real-time requirements of live VR streaming.