Research Of The Key Technologies In Large-scale Interactive VOD System

With the high-speed development of computer networks, digital compression and storage technology, IP based real-time multimedia communication services grow rapidly. Currently, the IP based stream-media techniques gradually mature, the studies of the relevant techniques of stream-media content distribution offer a possible way to construct large-scale Video-On-Demand systems. In large-scale VOD systems, efficient utilization of resources is a very prominent problem, enormous data transmission makes the network I/O bandwidth and the server disk I/O bandwidth become bottlenecks of the system. At the same time, many of the video service relevant problems are concentrated in the content distribution, the paper mainly focus on these two major bottlenecks, and research how to satisfy media data users request as much as possible in limited service conditions. The study mainly focused on the VOD server implementation strategy, consider how to achieve video stream-sharing mechanism with IP multicast technology, and proposes a realization of interactive functions with stream-sharing mechanism.The paper mainly studies of the cycle patching stream control algorithms which is one of the stream control algorithms in the VOD system. Based on it, introduces decentralized service method of Peer-to-peer technique, and proposes a cycle patching stream control algorithms with P2P method. The algorithm integrates cycle patching and P2P algorithms which are prevailing stream transmission methods nowadays. Based on cycle patching algorithms, stripping out patching stream service, using "virtual patching stream server" to offer patching stream service and video server only provides video source "seed" to the customers in the form of cycle broadcasting. With the P2P based cycle patching algorithms, video server can liberate part of the service load, markedly saving server bandwidth consumption, on the same frequency of requests; it can provide higher quality services.Secondly, researches how to achieve interactive functions (VCR) in multicast environment, using the video separation and combine technology, users dynamically separate from multicast groups, use specialized video stream to achieve interactive operations, and then return to the multicast video streams dynamically. VCR operations aim at resolving the requests in the local first, when the local resources can not meet the requirements, then send the requests to the server, it reduces the consumption of server resources as much as possible to enhance the overall service capacity. Finally, makes an analysis of the multicast transmission and VCR index files generation problems which appear in the VOD system realization, and proposes the corresponding solution. Proposing a structure of multicast module which can solve the file compatibility requirement, file information retrieval efficiency and network transmission efficiency problems very well. Proposing a method of generating VCR index files to solve the problems in the VCR fast-forward and fast-backward operations, establishment of the abstract files and the index files can help to achieve the accurately, quickly and efficiently cut over purposes.