Subjective QoE Evaluation of User-Centered Adaptive Streaming of Dynamic Point Clouds

Technological advances in head-mounted displays and novel real-time 3D acquisition and reconstruction solutions have fostered the development of 6 Degrees of Freedom (6DoF) teleimmersive systems for social VR applications. Point clouds have emerged as a popular format for such applications, owing to their simplicity and versatility; yet, dense point cloud contents are too large to deliver directly over bandwidth-limited networks. In this context, user-adaptive delivery mechanisms are a promising solution to exploit the increased range of motion offered by 6DoF VR applications to yield gains in perceived quality of 3D point cloud user representations, while reducing their bandwidth requirements. In this paper, we perform a user study in VR to quantify the gains adaptive tile selection strategies can bring with respect to non-adaptive solutions. In particular, we define an auxiliary utility function, we employ established methods from the literature and newly-proposed schemes for distributing the bit budget across the tiles, and we evaluate them together with non-adaptive streaming baselines through subjective QoE assessment. Results confirm that considerable gains can be obtained with user-adaptive streaming, achieving bit rate gains of up to 65% with respect to a non-adaptive approach to deliver comparable quality. Our analysis provides useful insights for the design and development of social VR applications.