基于RTP的视频传输控制方法的研究
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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。
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 provided
by 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.
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。
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 provided
by 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.
引文
[1] 流媒体中国．http://www.liumeiti.com/
[2] 蓝宇视频流媒体应用网．http://www.chinameal.com/
[3] 黎洪松．数字视频技术及其应用[M]．北京：清华大学出版社，1997．
[4] 丁贵广，郭宝龙．多媒体数据压缩标准化的现状与发展．计算机工程与应用，2002，01，104-107．
[5] 赵明阳．多用户计算机远程监控系统：[硕士学位论文]．北京：首都师范大学物理系，2000．
[6] H. Schulzrinne et al. RTP: A Transport Protocol for Real-Time Applications [S]. Internet RFC 1889, 1996-01.
[7] H. Schulzrinne. RTP Profile for Audio and Video Conferences with Minimal Control IS]. Internet RFC 1890, 1996-01.
[8] H. Schulzrinne, AT&T Bell Laboratories (Murray Hill). RTP. MCNC 2nd Packet Video Workshop. December 1992.
[9] C. Zhu, Intel Corp.. RTP Payload Format for H.263 Video Streams. Internet RFC 2190, September 1997.
[10] 罗明宇，卢锡城，韩亚欣．Internet多媒体实时传输技术．计算机工程与应用．2000，9，119-120．
[11] 郭大群．多媒体信息在网络中实时传输的研究与应用：[硕士学位论文]．南京：航空航天大学机械工程．2002．
[12] 朱一群，朱秋萍．多媒体实时传输协议(RTP)的研究．计算机应用研究，2002，10，122-124．
[13] 严俊，潘建平．Microsoft Windows环境RTP协议的实现及其适应性应用的研究．数据通信，1999，(2)，24-26．
[14] 严俊，马小骏，顾冠群．RTP协议的研究与实现．计算机工程与应用，2000，(9)，121-123．
[15] 张占军，韩承德，杨学良．多媒体实时传输协议RTP．计算机工程与应用，2001，(4)，9-11．
[16] 冯晔，冯忠义，曹宁．基于Socket网络编程接口实现局域网上视频传输的研究．微计算机信息，1998，14(5)，17-20．
[17] 吴勇，吴月珠，程剑峰．视频信息在网络上的实时传输和处理．小型微型计算机系统，1999，20(8)，637-640．
[18] 黄文涛，熊磊，毕笃彦．网络实时视频传输研究及实现．计算机应用，2003，23(2)，100-101．
[19] Henning Schulzrinne's RTP site, http://www.cs.columbia.edu/～hgs/rtp/
[20] Xin Wang and Henning Schulzrinne. Comparison of Adaptive Internet Multimedia Applications.
[21] 李晓东，裘正定．IP网上视频通信的控制机制．现代电信科技，2000，11(11)，4-7．
[22] Linda S.Cline et al. DirectShow RTP Support for Adaptivity in Networked Multimedia Applications. IEEE Multimedia Systems, 1998, 1-15.
[23] Jonathan Rosenberg and Henning Schulzrinne. Timer Reconsideration for Enhanced RTP Scalability. Proc. of Infocom, (San Francisco, California), March/April 1998.
[24] Andrea Basso, G. L. Cash and M. Reha Civanlar. Transmission of MPEG-2 Streams over Non-Guaranteed Quality of Service Networks. Proc. of Picture Coding Symposium, (Berlin, Germany), Sept.1997.
[25] Jonathan Rosenberg and Henning Schulzrinne. Issues and options for an aggregation service within RTP. November 1996.
[26] R. Klein. The Real-time Transport Protocol. Technical Report, Northwest Alliance for Computational Science and Engineering, Oct. 1996.
[27] I. Busse, B. Deffner and H. Schulzrinne. Dynamic QoS control of multimedia applications based on RTP. Computer Communications, Jan. 1996.
[28] 许先斌，安晖，吴国东．一种基于RTP的MPEG-2实时传输系统．计算机工程，2002，28(10)，167-168．
[29] 葛广英．多媒体信息网络实时传输的应用研究．计算机工程，2001，27(7)，56-58．
[30] 江冰，张金波，张学武等．局域网上动态视频实时传输技术的研究．计算机工程，2002，28(6)，208-210．
[31] 刘浩，胡栋．基于RTP/RTCP协议的IP视频系统设计与实现．计算机应用研究，2002，10，140-143．
[32] 刘锋，彭宇行．网络视频应用的程序设计模式研究．计算机应用研究，2002，8，7-9．
[33] 周敬利，张超，余胜生等．一种基于RTP的多媒体业务质量控制算法．华中科技大学学报(自然科学版)，2002，30(9)，18-20．
[34] K. Brown. The RTCP gateway: scaling real-time control bandwidth for wireless networks. Computer Communications, 23(2000), 1470-1483.
[35] Microsoft. Microsoft DirectX 8.1 SDK (C++), 2000. http://www.microsoft.com.
[36] Packet-based multimedia communications systems [S]. ITU-T Recommendation H.323, 1998.
[37] Dale Rogerson．COM技术内幕．北京：清华大学出版社．
[38] Randy Abernethy著．汪浩，郭钰等译．COM/DCOM技术内幕[M]．电子工业出版社，2000-01．
[39] 刘长有，周小林．VC++下利用DirectShow播放多媒体文件．现代计算机，2001，4，28-32．
[40] 林志勇，张昱，陈意云．DirectShow在MPEG-1流式播放器中的应用．计算机工程，2001，27(6)，140-142．
[41] 陈淑珍，陈睿．基于COM技术的多媒体监控系统的设计与实现．武汉大学学报(理学版)，2001，47(3)，377-380．
[42] 欧海翔．IP网上自适应QOS的研究：[硕士学位论文]．广东：工业大学计算机应用，2000．
[43] 江明，王群生．WDM/DirectShow视频捕捉架构解析．数字电视与数字视频，2002，10(244)，6-9．
[44] 李岚．基于AVI的流媒体多播技术研究：[硕士学位论文]．湖北：华中师范大学计算机应用，2002．
[45] 刘平，高胜法，王金富．一种基于DirectShow COM接口的多媒体流解码程序的设计．山东科学，2002，15(3)，17-21．
[2] 蓝宇视频流媒体应用网．http://www.chinameal.com/
[3] 黎洪松．数字视频技术及其应用[M]．北京：清华大学出版社，1997．
[4] 丁贵广，郭宝龙．多媒体数据压缩标准化的现状与发展．计算机工程与应用，2002，01，104-107．
[5] 赵明阳．多用户计算机远程监控系统：[硕士学位论文]．北京：首都师范大学物理系，2000．
[6] H. Schulzrinne et al. RTP: A Transport Protocol for Real-Time Applications [S]. Internet RFC 1889, 1996-01.
[7] H. Schulzrinne. RTP Profile for Audio and Video Conferences with Minimal Control IS]. Internet RFC 1890, 1996-01.
[8] H. Schulzrinne, AT&T Bell Laboratories (Murray Hill). RTP. MCNC 2nd Packet Video Workshop. December 1992.
[9] C. Zhu, Intel Corp.. RTP Payload Format for H.263 Video Streams. Internet RFC 2190, September 1997.
[10] 罗明宇，卢锡城，韩亚欣．Internet多媒体实时传输技术．计算机工程与应用．2000，9，119-120．
[11] 郭大群．多媒体信息在网络中实时传输的研究与应用：[硕士学位论文]．南京：航空航天大学机械工程．2002．
[12] 朱一群，朱秋萍．多媒体实时传输协议(RTP)的研究．计算机应用研究，2002，10，122-124．
[13] 严俊，潘建平．Microsoft Windows环境RTP协议的实现及其适应性应用的研究．数据通信，1999，(2)，24-26．
[14] 严俊，马小骏，顾冠群．RTP协议的研究与实现．计算机工程与应用，2000，(9)，121-123．
[15] 张占军，韩承德，杨学良．多媒体实时传输协议RTP．计算机工程与应用，2001，(4)，9-11．
[16] 冯晔，冯忠义，曹宁．基于Socket网络编程接口实现局域网上视频传输的研究．微计算机信息，1998，14(5)，17-20．
[17] 吴勇，吴月珠，程剑峰．视频信息在网络上的实时传输和处理．小型微型计算机系统，1999，20(8)，637-640．
[18] 黄文涛，熊磊，毕笃彦．网络实时视频传输研究及实现．计算机应用，2003，23(2)，100-101．
[19] Henning Schulzrinne's RTP site, http://www.cs.columbia.edu/～hgs/rtp/
[20] Xin Wang and Henning Schulzrinne. Comparison of Adaptive Internet Multimedia Applications.
[21] 李晓东，裘正定．IP网上视频通信的控制机制．现代电信科技，2000，11(11)，4-7．
[22] Linda S.Cline et al. DirectShow RTP Support for Adaptivity in Networked Multimedia Applications. IEEE Multimedia Systems, 1998, 1-15.
[23] Jonathan Rosenberg and Henning Schulzrinne. Timer Reconsideration for Enhanced RTP Scalability. Proc. of Infocom, (San Francisco, California), March/April 1998.
[24] Andrea Basso, G. L. Cash and M. Reha Civanlar. Transmission of MPEG-2 Streams over Non-Guaranteed Quality of Service Networks. Proc. of Picture Coding Symposium, (Berlin, Germany), Sept.1997.
[25] Jonathan Rosenberg and Henning Schulzrinne. Issues and options for an aggregation service within RTP. November 1996.
[26] R. Klein. The Real-time Transport Protocol. Technical Report, Northwest Alliance for Computational Science and Engineering, Oct. 1996.
[27] I. Busse, B. Deffner and H. Schulzrinne. Dynamic QoS control of multimedia applications based on RTP. Computer Communications, Jan. 1996.
[28] 许先斌，安晖，吴国东．一种基于RTP的MPEG-2实时传输系统．计算机工程，2002，28(10)，167-168．
[29] 葛广英．多媒体信息网络实时传输的应用研究．计算机工程，2001，27(7)，56-58．
[30] 江冰，张金波，张学武等．局域网上动态视频实时传输技术的研究．计算机工程，2002，28(6)，208-210．
[31] 刘浩，胡栋．基于RTP/RTCP协议的IP视频系统设计与实现．计算机应用研究，2002，10，140-143．
[32] 刘锋，彭宇行．网络视频应用的程序设计模式研究．计算机应用研究，2002，8，7-9．
[33] 周敬利，张超，余胜生等．一种基于RTP的多媒体业务质量控制算法．华中科技大学学报(自然科学版)，2002，30(9)，18-20．
[34] K. Brown. The RTCP gateway: scaling real-time control bandwidth for wireless networks. Computer Communications, 23(2000), 1470-1483.
[35] Microsoft. Microsoft DirectX 8.1 SDK (C++), 2000. http://www.microsoft.com.
[36] Packet-based multimedia communications systems [S]. ITU-T Recommendation H.323, 1998.
[37] Dale Rogerson．COM技术内幕．北京：清华大学出版社．
[38] Randy Abernethy著．汪浩，郭钰等译．COM/DCOM技术内幕[M]．电子工业出版社，2000-01．
[39] 刘长有，周小林．VC++下利用DirectShow播放多媒体文件．现代计算机，2001，4，28-32．
[40] 林志勇，张昱，陈意云．DirectShow在MPEG-1流式播放器中的应用．计算机工程，2001，27(6)，140-142．
[41] 陈淑珍，陈睿．基于COM技术的多媒体监控系统的设计与实现．武汉大学学报(理学版)，2001，47(3)，377-380．
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