A Study on Accuracy Controllable Media Synchronization Schemes in QoS Non-Guaranteed Networks

研究成果可分为以下六大类。建立了媒体同步的基本概念，概述了媒体同步的基本算法，明确了它们之间的关系。我们对9种异步恢复控制方案的媒体同步质量进行了主观和客观的评估，这些方案包括4种反应性控制技术的组合。通过多元回归分析，考察了主观素质测评与客观素质测评之间的关系。提出了一种基于重传的实时音视频流传输层差错恢复方案，称为RVTR。通过实验，我们对RVTR和其他四种方案的媒体同步质量进行了评估，并验证了RVTR的有效性。我们还增强了RVTR以支持组播通信。通过实验比较了因特网路由器上的四种分组调度算法(FIFO、优先级排队、基于类的排队和WFQ)在实时音视频传输中的媒体同步质量。实验结果表明，WFQ的质量是四种算法中最好的。在DiffServ的AF服务中，研究了TCP/UDP计算机数据流对媒体同步质量的影响，以考察TCP数据流的AFCP对媒体同步质量的影响。此外，我们还发现，随着端到端时延的增加，TCP数据流的影响会减小。利用本研究中建立的基本媒体同步算法，我们开发了两种基于组播通信的网络多媒体应用的媒体同步技术。一种是同时执行目标间同步控制的自适应因果关系控制方案，另一种是具有交互控制的存储媒体与直播媒体的联合同步方案。

The research results can be classified into the following six categories.1. We have established basic concepts of media synchronization, have surveyed its fundamental algorithms and then clarified their relationships.2. We have carried out both subjective and objective assessment of the media synchronization quality of nine recovery control schemes from asynchrony, which consist of combinations of four reactive control techniques. Then, we have investigated the relation between the subjective quality measure and the objective ones by multiple regression analysis.3. A transport-layer error recovery scheme based on retransmission for live audio-video streams has been proposed, which is referred to as RVTR. By experiment, we have assessed the media synchronization quality of RVTR and four other schemes; we then demonstrated the effectiveness of RVTR. We have also enhanced RVTR to support multicast communications.4. Four packet scheduling algorithms (FIFO, Priority Queueing, Class-Based Queueing, and WFQ) at routers in the Internet have been compared by experiment in terms of the media synchronizat ion quality in live audio-video transmission. The experimental results showed that WFQ achieves the best quality among the four.5. In the AF service of Diffserv, the effect of TCP/UDP computer data flows on media synchronization quality has been studied to examine how AFCP of the TCP data flow affects the quality. Moreover, we showed that the effect of the TCP data flow decreases as the end-to-end delay increases.6. Utilizing the basic media synchronization algorithms established in this research, we have developed two media synchronization techniques for networked multimedia applications based on multicast communications. One is an adaptive causality control scheme that also performs inter-destination synchronization control, and the other is a scheme for joint synchronization between stored media with interactive control and live media.