【作者】 龚剑；

【导师】 黄本雄；

【作者基本信息】 华中科技大学 ， 通信与信息系统， 2007， 硕士

【摘要】 制约网络视频监控系统应用发展的核心问题在于因特网的服务质量,由于因特网的状况是不可靠的,它只提供尽力传送服务,其带宽、丢包率、延时等网络特性时变性很大,难以满足网络视频监控系统的实时性服务质量要求,并常常造成播放延迟、视频质量抖动剧烈等不良情况,给使用者感官造成很大影响。所以,在网络视频监控系统中采用有效的差错恢复手段,解决好视频传输的服务质量问题对于网络视频监控系统的发展是极为重要的。考虑到信道编码对于实时性要求很强的视频数据通信来说是一种非常好的保证传输服务质量(QoS:Qualitity of Service)的方法。在对基于信道编码的三种典型的差错恢复方法进行分析的基础上,通过改变视频帧序列的编解码方式来克服前向纠错技术给通信系统带来的延迟以及对带宽增加的要求,实现了一种基于前向纠错技术的视频图像差错恢复方法,从而改善视频传输的传输质量。横向差错恢复技术克服了传统的纵向差错恢复中高错误相关性、网络拥塞以及由结点故障造成的网络损耗等问题。在采用分布式网络视频监控系统结构的基础上,为了进一步提高系统的鲁棒性,对横向差错恢复方案进行了详细地设计,在横向差错恢复中,结点被随机分配到各个平面,并通过其他平面的差错恢复邻居重传数据包来恢复错误,由于各个平面的数据传递过程相对独立,所以,差错恢复结点和差错恢复邻居间数据的关联性较弱。通过仿真实验,将传统的纵向差错恢复方案和横向差错恢复方案进行比较,证明了横向差错恢复较前者的差错恢复延迟小;通过分析横向差错恢复中平面数、各平面差错恢复邻居结点数与剩余损失率的关系,获得了选择最佳参数的可靠依据。更多还原

【Abstract】 The key problem of restricting the development in application of network surveillance system lies in the QoS (Qualitity of Service) of Internet. For the unreliable state of Internet, and providing best-effort service only, its characteristics such as bandwidth, packet loss rate, delay and etc., often have great alternation, and it is hard to satisfy the quality of service in real time of network surveillance system. Always this also leads to harmful situations as delay, acute vibration of video frequency quality, and so on, which exercises a great influence on users’sense organs. So taking effective measure called error recovery, what is extremely important for the development of network surveillance system is to solve the problem of QoS in video transmission.Considering Channel Coding is a very good measure to guarantee the QoS of transmission when video transmission asks for strong quality of real time. Based on the analysis of three typical error recovery ways of channel coding, this thesis will overcome the problem of delay and the requisition of increasing bandwidth brought by FEC (Forward Error Correction) through changing the coding and decoding of video frequency frame sequence. And it will achieve the goal based on the method of visual image error recovery of FEC, and then improve the quality of video.Horizontal error recovery overcomes the problem of high error correlation, implosion problem, and Outage due to node-link failure in vertical error recovery. In order to improve the robust of system further, basing on distributing network surveillance system, this thesis has an exhaustive design for horizontal error recovery. In horizontal error recovery, nodes are distributed to several planes randomly, recovering error with the help of re-transmission from other planes’error recovery neighbors. For the relatively independent data transmission process of each plane, the data of nodes and neighbors among error recovery are weak in connection. In the simulation experiment, comparing the traditional vertical error recovery with the horizontal error recovery, horizontal error recovery has less recovery delay than the former. And we can get the reliable data of best parameter through analyzing the relationship between numbers of planes of horizontal error recovery, nodes of error recovery neighbor in each plane and residual loss rate.更多还原