【作者】 卢选民；

【导师】 史浩山；

【作者基本信息】 西北工业大学 ， 电路与系统， 2002， 博士

【摘要】 多媒体同步是分布式多媒体系统的关键技术和基础，多媒体同步关系存在于多媒体的整个生命周期中。本文深入研究了分布式多媒体系统中，多媒体具有的复杂的时态关系和动态同步特性，以及关键媒体在应用中享有同步优先权等问题；深入研究了多媒体通信过程和多媒体对象的传输特性、同步需求，以及同步通信方案中信道分配以及同步传输调度算法等问题；同时，深入研究了实际分组交换网络中多媒体同步控制机制等问题。 概括起来，本文在以下几个方面取得了研究成果： 1．从时间理论和时态逻辑的途径出发，结合多媒体表现的动态特性，通过分析推导得出适合多媒体系统的非确定的时间片关系的扩展集，并将其简化为只有6个操作符规范的、非常直观的多媒体时态模型。 2．给出了建于多媒体系统时态关系扩展集基础之上的TPN网模型描述，证明了任意多个媒体对象之间的同步关系均可以用TPN网模型来表达。 3．提出了一个新的基于TPN网的交互式多媒体动态同步模型IDSM，该模型充分考虑到分布式环境中多媒体的动态同步特性以及关键媒体的优先权和人机交互要求，通过引入容许阻塞时间、回溯算法等有效克服了网络随机延迟、阻塞和丢包等因素的影响，以形式化的方式完整、准确地描述了多媒体信息流的时间行为。 4．依据IDSM模型，提出了一个新的优化信道分配方案，并在此基础上，提出了同步通信控制模型DSCM，包括服务器DSCM模型和客户DSCM模型。 5．提出了基于漏桶算法的自适应多媒体同步控制方案，该方案利用媒体单元的时间戳，对延时及延时抖动进行动态估计，及时了解网络负载的变动情况。当监测到实时媒体的播放质量恶化时，利用估计的结果，适当地调节多媒体对象的播放时刻，以此来达到重新同步和维持播放质量的目的。更多还原

【Abstract】 Synchronization is the key technique and basis of the distributed multimedia system. The synchronization relationship exists during the life period. In this thesis,the complicated temporal relationship and dynamic synchronization properties existed in multimedia in distributed multimedia system,and the problem of higher priority demands of key medium in application,and etc. are studied thoroughly;The course of multimedia communication,the transmission characteristics and the synchronization requirements of multimedia objects,and the algorithms of channel allocation and synchronization transmission schedule in synchronization communication scheme,and etc. are studied deeply;At the same time,the problems of multimedia synchronization control mechanism in the practical packet-switching networks and so on are studied too. The main contributions of this thesis as follows:1. Starting from the time theory and the temporal logic,and taking into account the dynamic properties of multimedia performance,the extended uncertain interval relationships set adapting to describe the multimedia system is proposed. By deducing in theory,it is simplified to a very plain temporal model that has only 6 canonical operation symbols.2. The TPN model based on the extended temporal relationships set is described. Furthermore,it is proved that every synchronization relationship among multimedia objects can be denoted with the TPN model.3. An improved interactive dynamic multimedia synchronization model (IDSM) based on TPN is proposed. The new model takes the dynamic synchronization properties and the demands of the priority of key medium and the function of user interaction in the distributed systems into account,introduces the allowed blocking time,backtracking rules and so on to handle the problems caused by random delay,blocking or lost packets,and describes the temporal behavior of multimedia information stream fully,accurately and formally.4. A new optimized channel allocation scheme is proposed according to the model of IDSM,and a control model of synchronization communication (DSCM) is proposed based on the optimized channel allocation scheme,including server DSCM and client DSCM.5. A adaptive multimedia synchronization control mechanism based on the leak-bucket algorithm is proposed. It estimates the range of delay according to the practical network load by making use of the time-stamp of the medium units,and adjusts dynamically. It is effective in various networks,and can satisfy the QoS demands of multimedia synchronization.更多还原