HTTP/2-Based Streaming Solutions for Tiled Omnidirectional Videos

360° video streaming is coming up against two major technical challenges: network resource consumption and Quality of Experience (QoE). Dynamically adapting the content delivery process to the user behavior is a promising approach to ensure both important network resource savings and satisfying experiences. In this paper, we propose to leverage HTTP Adaptive Streaming (HAS), tiled-based 360° video encoding and the HTTP/2 protocol to implement this dynamic content delivery process. The 360° video stream is spatially encoded into tiles and temporally divided into segments. The client executes two viewport predictions for each segment, one before and one during its delivery. Upon every prediction, it decides on a priority and a quality level for each tile of the video segment; tiles overlapping with the predicted viewport get higher priorities and quality levels. Then it exploits the priority and stream termination features of the HTTP/2 protocol to enforce its decisions. We compare our proposed solution with four alternative schemes on a set of 360° video streaming sessions corresponding to various types of videos, user behaviors and network conditions. Our solution provides better performances: a higher quality on the viewport pixels, a lower ratio of unreceived viewport pixels in bandwidth-constrained networks, and a reduction of the bandwidth consumption, up to 12% compared to the alternative schemes exploiting 2 viewport predictions per video segment.