A Study on a Set of Media Synchronization Protocols in Wireless Networks

研究成果可分为五大类。第一项研究考察了四种用于存储的mpeg视频和语音的嘴唇同步方案；两种方案将语音和视频交织到单个传输流中，其他方案分别处理它们。在每种类型中，一个在目的地施加同步控制，而另一个则不。此外，我们还将一种动态的MPEG视频分辨率控制方案应用到两种同步控制方案中。我们在Altair无线局域网上实现了这些方案，测试结果表明，在负载较重的网络中需要进行同步控制，动态分辨率控制是有效的。其次，我们研究了基于实时视频和语音的媒体同步。第三，提出了一种存储视频、实时语音和实时视频流的联合同步方案。该方案利用了直播媒体和存储媒体之间的特性差异。在ATM和无线局域网的集成上实现了该方案，并验证了该方案的有效性。研究四对小灵通互联网接入中滑动控制下的存储媒体同步质量进行了测试。开发了一个从媒体服务器到小灵通移动终端传输H.263视频和G.726音频的简单实验系统。分析了小灵通信道瑞利衰落和网络数据负载对媒体同步质量的影响，研究了滑动控制在视频和音频交织传输中的应用，并提出了一种同时控制媒体同步质量和传输时延的QOS控制方案。通过仿真，验证了该方案的有效性。此外，我们还利用PIAFS和UDP/IP协议进行了G.728音频的实时传输实验。

The research results can be classified into five categories. The first study examines four lip synchronization schemes for stored MPEG video and voice ; two schemes interleave voice and video into a single transport stream, and the others treat them separately. In each kind, one exerts synchronization control at the destination, while the other does not. In addition, we apply a dynamic resolution control scheme of MPEG video to the two schemes with synchronization control. We have implemented those schemes on an ALTAIR wireless LAN.The measured performance shows that heavily loaded networks need synchronization control and that the dynamic resolution control is effective.Secondly, we study media synchronization on live MPEG video and voice as in the first study.Thirdly, we propose a joint synchronization scheme among stored video, live voice and live video streams. The scheme takes advantage of the difference in the feature between live and stored media. We have implemented the scheme on an integrated ATM and wireless LAN and demonstrated its effectiveness.The fourth study measures the quality of stored media synchronization under the slide control in PHS Internet access. A simple experimental system was developed for the transmission of H.263 video and G.726 audio from a media server to PHS mobile terminals. We examine the effects of Rayleigh fading in the PHS channels and the data load in the Internet on the media synchronization quality.Lastly, we study the application of the slide control to interleaved transmission of live video and audio specified by the H.223 Annex in PHS.We also propose a QOS control scheme to control both media synchronization quality and transmission delay. Through simulation, we confirm the effectiveness of the scheme. In addition, we carry out an experiment of live G.728 audio transmission with PIAFS and UDP/IP.