采用被动测量技术分析了PPStream点播系统的节点发现和分发协议,研究了视频缓冲图(Buffer-Map)的结构特点和主要功能,在此基础上设计并实现了一款用于获取PPStream点播节目用户Buffer-Map信息的分布式主动测量爬虫系统,使用该爬虫对PPStream点播系统的用户观看行为进行了分类统计,首次提出了用户观看粘度的概念并做量化统计分析,发现用户观看粘度与平均观看长度成正比,与累计概率曲线斜率成反比.%The analysis results on PPStream-VOD System client behavior characteristics were presented in this paper. This study began from researching on peer-distributing protocol and the architecture of Buffer-Map based on passive measurement. A dedicated PPS-VOD crawler was deployed to capture clients' Buffer-Map and study the characteristics of client watching behavior. By accurate data analysis, the client behavior was classified as Long-Smoother, Short-Smoother and Jumper. Then the proportion of three kinds of clients and their different watching behaviors were proposed. The concept watching viscosity was put forward to reveal the attraction of program to users, which is in direct proportion to average watching time, and in inverse proportion to slope of probability accumulation curve.
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