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

研究结果可以分为五类。第一项研究考察了存储MPEG视频和语音的四种唇同步方案；两种方案将语音和视频交织到一个传输流中，其他方案分别处理它们。在每一种类型中，一个在目的地施加同步控制，而另一个则没有。此外，我们将MPEG视频的动态分辨率控制方案应用于这两种方案，并进行同步控制。我们已经在ALTAIR无线局域网上实现了这些方案。实测性能表明，重载网络需要同步控制，动态分辨率控制是有效的。其次，和第一篇研究一样，我们研究了MPEG实时视频和语音的媒体同步。第三，提出了存储视频、实时语音和实时视频流的联合同步方案。该方案利用了实时媒体和存储媒体之间的特性差异。我们在一个集成ATM和无线局域网上实现了该方案，并验证了其有效性。第四项研究测量了小灵通网络接入中滑动控制下存储媒体同步的质量。为实现H.263视频和G.726音频从媒体服务器到小灵通移动终端的传输，开发了一个简单的实验系统。研究了小灵通信道中的瑞利衰落和网络中的数据负载对媒体同步质量的影响。最后，我们研究了滑动控制在小灵通中H.223附件规定的视频和音频直播交错传输中的应用。我们还提出了一种QOS控制方案来控制媒体同步质量和传输延迟。通过仿真验证了该方案的有效性。此外，我们还进行了基于PIAFS和UDP/IP协议的G.728音频实时传输实验。

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.