基于嵌入式客户端的流媒体服务质量-智能与分布计算实验室

基于嵌入式客户端的流媒体服务质量

姓名	梁少波
论文答辩日期	2007.01.26
论文提交日期	2007.02.02
论文级别	硕士
中文题名	基于嵌入式客户端的流媒体服务质量
英文题名	Research and Implementation on Quality of Service Control for Streaming Media
导师1	卢正鼎
导师2
中文关键词	嵌入式;流媒体;服务质量;缓冲区;控制策略
英文关键词	embed;streaming media;quality of service;cache buffer;control strategy
中文文摘	随着网络技术和多媒体技术的迅速发展，网络音频视频也成为必不可少的内容。于是，流媒体技术应运而生，不仅应用在PC机上，而且也广泛的应用在一些嵌入式设备上。流媒体具有实时性要求高、误码率敏感、数据量大以及计算复杂等特点，所以目前的因特网存在的丢包、失序、延迟、抖动等问题以及嵌入式客户端存在的资源限制都严重的影响了流媒体的服务质量。为了解决上述问题，嵌入式的流媒体客户端需要通过实施一定的控制策略来保证流媒体的服务质量。基于对流媒体相关技术的分析，构建了一个基于嵌入式客户端的优化控制模型，研究了影响流媒体服务质量的各参数如平均速率、延时抖动、解码码率以及丢帧率等的简化计算方法，并基于这些参数改进了缓冲区长度估算方法，提出了一系列控制策略来平滑网络传输带来的影响，节约客户端资源，保证流媒体的质量。这些控制策略主要包括伪命令策略、磁盘缓存策略、零拷贝策略、主动丢弃策略、反馈机制。伪命令策略和磁盘缓存策略可以在缓冲区上溢预警时来采取措施避免缓冲区发生上溢；零拷贝策略通过指针传递的方式以及良好的数据结构设计避免内存数据的拷贝，从而节约客户端CPU资源和缓冲区资源；主动丢弃策略策略可以在丢包时利用数据的相关性合理抛弃相关联的其它数据包，提高缓冲区的有效利用率；反馈机制可以通过传递关键性能参数至服务器端，由服务器调整流媒体的发送速率，从而保证流媒体服务质量。将嵌入式客户端的控制模型实际应用在具有水印检测功能的嵌入式IPTV接收终端的系统中，对系统运行的结果进行了分析。实践验证控制模型的引入确实良好的保证了嵌入式系统中的流媒体服务质量。
英文文摘	With the rapid development of network and multimedia technologies,requirements for information diversity make network audio and video programs more and more indispensable. Thus Streaming media technology has emerged, used not only in the PC applications, but also widely in embedded equipment. Streaming media has some characteristics ,such as real-time transmission ,sensitive to transmission delay,large data volume and comlexity of computation. So, it seriously affects the streaming media's service quality ,which is packet loss, out-of-order, delay, jitters , and the resource limit of the embed client.To solve these problems,the embed client should implement some control strategies to ensure streaming media's quality. Based on the analysis of streaming media , we construct a client-based control model,to analysis the simplified calculating methods of these service parameters affecting streaming media,such as average speed, delay jitter, bit rate decoding. These parameters are used to improve estimates of the buffer zone's length.A series of control strategies are constructed to smooth the network transmission, save client resources,and ensure the quality of streaming media. These strategies include pseudo-order control strategies, disk caching strategies, zero-copy strategy initiative discarded strategy, a feedback mechanism. Pseudo disk caching strategies and tactics can take measures to avoid buffer overflow when the warning occurred;Zero-Copy good strategy takes the data transmission methods and the data structure design to avoid the copy Client CPU resources and thereby saving resources buffer; Strategy initiative can be discarded in a reasonable correlation between the use of data packet loss when connected to the other data packets discarded and thereby increase the effective utilization of the buffer zone; Feedback mechanism can send key performance parameters to the server, which adjusts the streaming media server transmission rate , so as to guarantee service quality streaming media. The client-based control model will be used in the IPTV system which is embedded watermark detection receiving end, and does the results of the analysis of the system's operation. Practice has proven that the model is indeed, and the introduction of the embedded system can ensure good quality of streaming media.