The Research And Implementation Of Very Large Scale VOD Architecture And Service Strategy

Along with the advancement of communication and computing technology, the human society is on the way to a broadband network-centered information era. As a typical broadband network application, Very Large Scale VOD (Video-On-Demand), VLS-VOD in short, will affect the. way of entertainment, education, working, shopping and even the people's life. The technique of small or medium scale VOD has matured, but there are some great challenges on the way towards VLS-VOD, including challenges to the existing video server architecture, service strategy, transmission and storing techniques. Current research of VLS-VOD are focused on scalable software and hardware architecture and effective bandwidth-sharing mechanism, which are two foundation stones in scaling the VOD system to serve more users. The VLS-VOD architecture and service strategies presented in this dissertation are developed to solve the two problems. Based on the analysis of the VLS-VOD requirements and two existing architectures, multi-node video server and virtual server, we present a scalable video server architecture, named as VVS, for Virtual Video Server. By introducing into strategy server, VVS can support different user service strategies in VLS-VOD systems, and make the VOD software and hardware to be used more effectively.Designing of VOD software architecure, instead of VOD functions, has become the main task in VOD software research. It is important to design an open and scalable software architecture while developing the VOD software. Based on the analysis of VOD service process and service characteristics, we design and implement an open and scalable stream service environment (OSSE). The cores of the OSSE are the two components: channel and channel controller. A series of applications have been developed in use of OSSE, and the OSSE has revealed excellent openness and scalability. The OSSE has been used in some successful distributed multimedia products we developed.Effective bandwidth-sharing strategy can improve the service ability of VOD system with limited system resource significantly. Most of existing VOD bandwidth-sharing strategies are analyzed in this dissertation, and a new strategy is proposed, named as Layer-staggered Segmental Broadcasting (LSB) strategy. LSB can share bandwidth effectively amongusers requesting the same movie program, thus save the server's bandwidth and provide service to large numbers of users with limited resource. The analytic results have shown that the LSB strategy outperforms other existing strategies. Two enhanced strategies are proposed based on LSB: Dynamic LSB (D-LSB) and Real-Time LSB(RT-LSB). D-LSB make the server's bandwidth to be used more effectively and can adapt the changing of program requesting frequency automatically, while RT-LSB provides users with real-time service.The VOD data layout is tightly correlated with the service strategy. After analyzing the data access characteristics of LSB, we present a Segmental Hybrid Data Layout (SHDL) scheme to be used in multi-node video servers. With a little redundant data, SHDL can avoid performance degrading caused by memory overflow, tolerate more data access skew and improve the whole performance of the VOD system.Providing VLS-VOD service in the Internet is another important research topic. Multimedia proxy server and its service strategy are the basis of the Internet VOD service. A multimedia proxy server model is proposed based on the layer-encoding model. The server model makes the server's cache be used effectively and can adapt the changing of network bandwidth. In the server model, the data quality of a program stored in the server's cache, is directly related to the requesting frequency and requested bandwidth of the program.As a typical broadband network application, VLS-VOD has attracted large numbers of service providers and users. What we have done and what we will do next will advance the VLS-VOD application, and provide a good theoretical and practical foundation for VLS-VOD research.