基于RTP的视频传输控制方法的研究

【作者】 张明华；

【导师】 谢琦；

【作者基本信息】 郑州大学 ， 计算机应用技术， 2003， 硕士

【摘要】 计算机网络技术和多媒体技术的不断进步成为网络多媒体应用日益普及和发展的强大动力。视频会议，视频点播，远程教育，无人监控等分布式多媒体应用逐渐走入人们的生活，给人们的工作和生活带来了极大的便利和无穷的乐趣。 然而，基于IP的网络中提供的尽力而为的服务并不适合多媒体视频信息的传输。视频信息的传输常常会因为网络拥塞而暂停或出现马赛克，网络状态的波动极大的影响着视频信息的播放效果，服务质量很难保证。 本文的研究项目由网络多媒体应用中的视频传输需求提出，旨在研究基于RTP协议的视频传输控制方法，使之能够适应网络状态的变化。论文的论述从以下四个方面展开： (1)IP网络的快速发展使得数字视频的传输逐渐成为现实。本文首先分析了网络多媒体应用中常用的流媒体技术，视频压缩编码技术。从当今流行的视频应用系统中指出视频应用的关键性问题。 (2)本文深入分析了RTP的特点、内容，认为该协议非常适合视频信息的网上传输。IETF制订的实时传输协议RTP是一个基于传输层的协议，它提供端到端的实时数据传输服务，其中的实时传输控制协议RTCP提供的控制功能可以有效的监控视频信息的传输。合理利用RTCP提供的控制信息并加上一些控制策略就可以更好的控制视频信息的传输，满足某方面服务质量的要求。 (3)针对视频传输中的速率控制，本文分析了几种控制方法和思路，提出了一种基于RTP的源端视频传输控制策略。该方法可以使发送方的视频传输速率自动适应网络状态的变化，并有效减少网络的拥塞。 (4)为了实现RTP及传输控制策略，本文采用Microsoft DirectShow所提供的平台。利用DirectShow提供的宽松的格式支持和基于组件对象模型的特征，本文研究了DirectShow的体系结构、基本原理和基本构件——过滤器的构造方法，将RTP协议作为过滤器进行了实现，并利用DirectShow的体系结构和已有的采集、编码组件，实现了一套完整的视频传输实验模型。 本文的主要工作在于： (1)分析和研究了RTP协议的主要内容，特点。针对视频传输的特点，提出了基于RTP的视频传输控制方法。该方法着重在速率控制。 (2)设计了一个基于Directshow技术的视频传输模型。该模型灵活方便，无需使用视频捕捉卡，可以在中小型的应用中使用。更多还原

【Abstract】 The steady advancement of technology in the field of computer networks and multimedia has become a strong impetus to the development and popularization of the networked multimedia applications. Distributed multimedia applications such as videoconference, video on demand, long-distance education, automatic monitor system etc. are slowly coming into people’s life. They also bring much facilities and fun to people’s work and life.But on the other hand, the best-effort service based on IP provided by Internet isn’t suitable for the transmission of video information. The video information transmission always pauses or appears mosaic because of network congestion. The playback effect of video information is always affected by the fluctuation of network states. QOS is difficult to be guaranteed.Coming from a video transmission need in networked multimedia application, the research project the thesis discusses is to research an RTP-based video transmission control method, which can adapt to the changes of network states. The thesis includes the following four parts:Firstly, fast development of IP network makes transmission of digital video information real. This thesis analyzes stream media technology and video compression coding technology, then points out the key problems in networked multimedia application from many popular video transmission systems.Secondly, this thesis lucubrates the contents and characters of RTP and thinks that RTP is well suitable for the video transmission. The real-time transport protocol (RTP) drawn by IETF is a protocol worked on the top of transport protocol. RTP provides end-to-end real-time multimedia data transmission. RTCP, one of its components, can effectively control and monitor the transmission. Making good use of the control messages providedby RTCP and some control strategies, we can well control video transmission and meet some requires in QOS.Thirdly, about rate control during video transmission, this thesis analyzes several control methods and ideas, puts forward an RTP-based source video transmission control policy. This policy can make video transmission rate of sender automatically adaptive to the changes of network states and efficiently reduces network congestion.Fourthly, in order to realize RTP and transmission control policy, this thesis makes use of the platform of Microsoft DirectShow. Using the wide variety of formats supported by DirectShow and the characters based on COM, this thesis researches the architecture of DirectShow, its basic theory and construction of its basic component-filter, realizes RTP as two filters. With the help of existing capture and encode components, making use of DirectShow architecture, this thesis realizes an integrated video transmission experiment model.The main work of this thesis:The first, this thesis analyzes the contents and characters of RTP. Aiming at the characters of video transmission, it brings forward an RTP-based video transmission control method, which is mainly for rate control.The second, this thesis designs a DirectShow-based video transmission model. This model is flexible and convenient, without need to use video capture card. It can be applied to small or middle scale application.更多还原