A Three-Stage Progressive Transmission Scheme for Virtual Environments Over Lossy Networks

The rapid development of Virtual Environments (VEs) gives rise to its prominent performance in a myriad of multimedia applications. Accompanied by this is the increasingly massive data used for ascending user's visual experience. Recently, 3D streaming makes it viable to put VEs into real-time use through progressive transmission. Nonetheless, downloading VEs over inevitable lossy networks still remains a major bottleneck that urgently needs to be solved. In this paper, we propose a three-stage progressive transmission scheme for VEs over lossy networks, which aims to minimize distortion even when encountering poor network condition. The first stage is the Pre-coding Stage that offers the most feasible transmission scheme for subsequent transmission, in this stage we combine the advanced interest management algorithm and our proposed scene distortion estimation algorithm to bring up a scene update strategy which takes the user's visual features, quality of the scene and bandwidth estimation into account, so as to determine the download priority comprehensively. In the following Transmitting Stage, we apply Transmission Control Protocol (TCP) to make sure that we convey the essential information. More importantly, we adopt expanding window fountain (EWF) codes to provide an unequal error protection (UEP) for data with different importance. Eventually in the third After-process Stage, we employ a geometry prediction algorithm for the scenario with packet loss. The final results of our experiments show that the three-stage scheme can offer preeminent visual experience especially when it comes to a relatively inferior network condition.