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多媒体同步的一个主要问题是多媒体同步时间要求的描述与建模。文中基于时间流Ｐｅｔｒｉ网模型（ＴＳＰＮ），通过分析ＴＳＰＮ 模型的不足之处，提出了一种新的多媒体同步模型——扩展时间流Ｐｅｔｒｉ网模型（ＸＴＳＰＮ）．ＸＴＳＰＮ 不但可以完全、准确地描述媒体流内和流间的时间行为，而且通过引入容许阻塞时间、回溯算法等对ＴＳＰＮ进行扩展，可以有效地克服网络随机延迟、阻塞和丢包等因素的不良影响，提高了模型的建模能力和对分布式网络环境的适应能力．
A major problem with multimedia synchronization is the description and modeling of multimedia synchronization time requirements. In this paper, based on the time-flow Petri nets model (TSPN), a new multimedia synchronization model-extended time-stream Petri nets model (XTSPN) is proposed by analyzing the shortcomings of the TSPN model. XTSPN not only can completely and accurately describe the time behavior in and out of the media stream, but also can effectively overcome the adverse effects of network random delay, blocking and packet loss by introducing the allowable blocking time and backtracking algorithm to extend TSPN , Improving the model’s modeling ability and adaptability to distributed network environment.