On-Demand P2P Video Streaming: Integration of Video Coding and Network Application Design

现有的视频流网络(VSN)依赖于几个专用服务器来存储和分发视频。这种架构在服务器成本和互联网连接成本方面都非常昂贵。单个服务器的故障也可能导致整个系统崩溃。本研究项目研究一种基于点对点的视频点播网络，它承诺提供低成本但高质量的视频点播服务。该系统将每个视频编码成多个同等重要的子流(称为描述)，并将每个子流放置在不同的对等体上。当客户端想要观看视频时，多个对等点充当服务器，每个对等点向客户端发送视频的不同子流。当服务对等体在流会话中途断开连接时，系统寻找存储相同视频子流并且具有足够剩余上行链路带宽的替换对等体。视频编码器被设计成使得在定位替换对等体之前的时间段中视频质量只有适度的下降。该系统设计包括五个交互部分：1)多描述视频编码；2)子流放置；3)接纳控制；4)子流服务器选择；5)子流分发。分析研究和实验都是为了检验系统的性能及其相对于基于基础设施的系统的收益。该系统的成功开发将使人们能够以极低的成本搜索和点播大量用于教育、医疗和娱乐等目的的数字视频内容库，从而造福整个社会。

Existing video streaming networks (VSN) rely on a few dedicated servers to store and distribute videos. Such architecture is very costly, both in terms of server cost and Internet-connection cost. Failures of a single server can also cause the collapse of the entire system. This research project investigates a peer-to-peer based VSN that has the promise to provide low-cost and yet high quality video on-demand service. The system encodes each video into multiple equally important sub-streams (called descriptions) and places each sub-stream on a different peer. When a client wants to see a video, multiple peers act as servers, each sending a different sub-stream of the video to the client. When a serving peer disconnects in the middle of a streaming session, the system looks for a replacement peer that stores the same video sub-stream and has sufficient surplus uplink bandwidth. The video coder is designed such that there is only a modest degradation in video quality in the period before a replacement peer is located. The system design has five interacting components: 1) multiple description video coding; 2) sub-stream placement; 3) admission control; 4) sub-stream server selection; and 5) sub-stream delivery. Both analytical studies and experimentations are conducted to examine the system performance and its gain over infrastructure-based systems. Successful development of the system will enable people to, at very low cost, search and view on-demand enormous libraries of digital video content for the purpose of education, healthcare, entertainment, etc., thus benefiting the society as a whole.