Enabling Multiparty 3D Tele-Immersive Environments with ViewCast

Three-dimensional tele-immersive (3DTI) environments have great potential to promote collaborative work among geographically distributed users. However, most existing 3DTI systems work with only two sites due to the huge demand of resources and the lack of a simple yet powerful networking model to handle connectivity, scalability, and quality-of-service (QoS) guarantees. In this article, we explore the design space from the angle of multistream management to enable multi-party 3DTI communication. Multiple correlated 3D video streams are employed to provide a comprehensive representation of the physical scene in each 3DTI environment, and rendered together to establish a common cyberspace among all participating 3DTI environments. The existence of multistream correlation provides the unique opportunity for new approaches in QoS provisioning. Previous work mostly concentrated on compression and adaptation techniques on the per-stream basis while ignoring the application layer semantics and the coordination required among streams. We propose an innovative and generalized ViewCast model to coordinate the multistream content dissemination over an overlay network. ViewCast leverages view semantics in 3D free-viewpoint video systems to fill the gap between the high-level user interest and the low-level stream management. In ViewCast, only the view information is specified by the user/application, while the underlying control dynamically performs stream differentiation, selection, coordination and dissemination. We present the details of ViewCast and evaluate it through both simulation and 3DTI sessions among tele-immersive environments residing in different institutes across the Internet2. Our experimental results demonstrate the implementation feasibility and performance enhancement of ViewCast in supporting the multiparty 3DTI collaboration.