多媒体即时通信技术在远程教育平台上的应用
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摘要
互联网技术的发展为实现知识从教育者向学习者的传递提供了新的手段,主要包括丰富的学习资源、信息检索与查询工具、各种通信工具等,支持学习者独立或合作获取知识。全民逐步确立的终身学习观念直接导致庞大的网络教育用户群体。P2P即时通信技术和P2P流媒体技术的出现成功解决C/S和B/S模式带来的瓶颈问题,成为当前互联网技术研究和应用的热点。这使得构造具有个性化学习功能的远程多媒体互动教学平台不仅必要而且成为可能。
“方达即时通”远程教育平台是一个基于互联网络、采用混合式P2P通信结构的远程教学系统,提供了即时通信、音视频交流、资源共享和教学管理等功能,是教师、学生、家长之间相互即时交流的平台,目前已在中小学推广使用。但该系统的远程教学功能不够完善,只能通过文字和视频实现交流,不提供课件实时教学功能,在技术上采用濒于淘汰的VFW体系结构,因此多媒体教学问题必须很好的解决。
本文在“方达即时通”远程教学平台基础上,对其教学功能进行了强化。利用Directshow技术框架改善了实时音视频交流的性能,增加了课件同步播放和电子白板功能。使得系统的教学功能大大提高。
本文首先阐述了研究背景和相关理论,提出了系统实现的解决方案和关键技术设计,包括音视频实时交流的DirectShow框架,结合MP3和MPEG-4音视频编码技术,利用精简的RTP协议实现了优良的音视频数据封装和解析策略,并使用RTCP协议提供的相关信息,设计了根据网络带宽变化自适应调整的发送速率算法,来控制发送端输出码率,利用有限的网络带宽尽量满足用户的通信质量要求。最后,本文详细介绍了系统的实现,包括音视频的采集、编解码、传输和回放,PPT课件的传输、显示和控制,白板教学的绘图、远程共享控制等,设计和实现了音视频和PPT课件教学三元同步问题,对相关技术做了深入的研究和探讨。
系统的设计和实现采用当前先进成熟的主流技术,硬件成本低,在远程教育平台上运行良好,是多媒体技术与即时通信技术在远程教学系统上应用的新形式。
The development of Internet technologies provides a new means for passing knowledge from pedagogs to learners. It includes abundant learning resources, information retrieval and query tools, all kinds of communication tools, which supports learners to acquire knowledge on his own or by working together. The concept of lifelong learning all gradually established causes a direct result of a huge user groups for education network.Instant communication technology and streaming media technology based on P2P solve the choke point of C/S and B/S models successfully, and become hot issues of research and application in Internet technology.This makes it possible and essencial to build a personalized multimedia platform for distance interactive teaching and learning.
Distance education platform of "Founder Messenger" is a distance education system using hybrid P2P communication structure based on Internet, providing instant communications, audio and video exchanges, the sharing of resources and teaching management. It facilitates teachers, students and parents to immediate communicate, and now already be promoted in the primary and secondary schools. However, the teching fuction of the system can be realized only through text and video exchanges without real-time couseware teaching, and use the technical architecture of VFW which will eliminate. From the above analysis, it requires a good solution to multimedia teaching.
This paper enhances the teaching function of "Founder Messenger ".It ameliorates the performance of audio and video using Diretshow framework, adds simultaneous courseware teaching and whiteboard tomake the system improves grately.
This paper's structure is as follows. Firstly,related technologies and research background are introduced. Secondly,the resolution of system and key models' design are analyzed aiming at using limited network bandwidth as possible to meet the quality of the user's communication requirements,including DirectShow framework of real-time audio and video chatting, MP3 and MPEG-4 audio and video coding technologies,good packing and unpacking strategy in the use of the simplified RTP protocol, the adaptive rate control algorithm in accordance with changes of network bandwidth from the feedback of RTCP.Finally,the realization of the system is detailedly described, including collection, coding, transmission and playback of audio and video, the transmission,display and remote control of PPT courseware and the graphics' drawing, remote sharing control of whiteboard teaching.Meanwhile, synchronization problemof audio and video mixed with PPT courseware is solved, and the related technologies are studied for in-depth research.
System Design and Implementation makes use of the current matural mainstream technologies. Although it costs low in hardware, it runs well on the distance education platform.The software is a new form of applying the multimedia technology with instant communication technologies to distance education system.
“方达即时通”远程教育平台是一个基于互联网络、采用混合式P2P通信结构的远程教学系统,提供了即时通信、音视频交流、资源共享和教学管理等功能,是教师、学生、家长之间相互即时交流的平台,目前已在中小学推广使用。但该系统的远程教学功能不够完善,只能通过文字和视频实现交流,不提供课件实时教学功能,在技术上采用濒于淘汰的VFW体系结构,因此多媒体教学问题必须很好的解决。
本文在“方达即时通”远程教学平台基础上,对其教学功能进行了强化。利用Directshow技术框架改善了实时音视频交流的性能,增加了课件同步播放和电子白板功能。使得系统的教学功能大大提高。
本文首先阐述了研究背景和相关理论,提出了系统实现的解决方案和关键技术设计,包括音视频实时交流的DirectShow框架,结合MP3和MPEG-4音视频编码技术,利用精简的RTP协议实现了优良的音视频数据封装和解析策略,并使用RTCP协议提供的相关信息,设计了根据网络带宽变化自适应调整的发送速率算法,来控制发送端输出码率,利用有限的网络带宽尽量满足用户的通信质量要求。最后,本文详细介绍了系统的实现,包括音视频的采集、编解码、传输和回放,PPT课件的传输、显示和控制,白板教学的绘图、远程共享控制等,设计和实现了音视频和PPT课件教学三元同步问题,对相关技术做了深入的研究和探讨。
系统的设计和实现采用当前先进成熟的主流技术,硬件成本低,在远程教育平台上运行良好,是多媒体技术与即时通信技术在远程教学系统上应用的新形式。
The development of Internet technologies provides a new means for passing knowledge from pedagogs to learners. It includes abundant learning resources, information retrieval and query tools, all kinds of communication tools, which supports learners to acquire knowledge on his own or by working together. The concept of lifelong learning all gradually established causes a direct result of a huge user groups for education network.Instant communication technology and streaming media technology based on P2P solve the choke point of C/S and B/S models successfully, and become hot issues of research and application in Internet technology.This makes it possible and essencial to build a personalized multimedia platform for distance interactive teaching and learning.
Distance education platform of "Founder Messenger" is a distance education system using hybrid P2P communication structure based on Internet, providing instant communications, audio and video exchanges, the sharing of resources and teaching management. It facilitates teachers, students and parents to immediate communicate, and now already be promoted in the primary and secondary schools. However, the teching fuction of the system can be realized only through text and video exchanges without real-time couseware teaching, and use the technical architecture of VFW which will eliminate. From the above analysis, it requires a good solution to multimedia teaching.
This paper enhances the teaching function of "Founder Messenger ".It ameliorates the performance of audio and video using Diretshow framework, adds simultaneous courseware teaching and whiteboard tomake the system improves grately.
This paper's structure is as follows. Firstly,related technologies and research background are introduced. Secondly,the resolution of system and key models' design are analyzed aiming at using limited network bandwidth as possible to meet the quality of the user's communication requirements,including DirectShow framework of real-time audio and video chatting, MP3 and MPEG-4 audio and video coding technologies,good packing and unpacking strategy in the use of the simplified RTP protocol, the adaptive rate control algorithm in accordance with changes of network bandwidth from the feedback of RTCP.Finally,the realization of the system is detailedly described, including collection, coding, transmission and playback of audio and video, the transmission,display and remote control of PPT courseware and the graphics' drawing, remote sharing control of whiteboard teaching.Meanwhile, synchronization problemof audio and video mixed with PPT courseware is solved, and the related technologies are studied for in-depth research.
System Design and Implementation makes use of the current matural mainstream technologies. Although it costs low in hardware, it runs well on the distance education platform.The software is a new form of applying the multimedia technology with instant communication technologies to distance education system.
引文
[1]马仝芬.一种用于网络教育的P2P通信模型的研究与实现:[硕士学位论文].北京:北方工业大学,2006
[2]张立涓.校园网网络教师多媒体信息传输技术的研究:[硕士学位论文].大连:大连海事大学计算机应用技术,2003
[3]王月娟.多媒体白板系统及其在远程教育中的应用:[硕士学位论文].大连:大连理工大学,2006.
[4]Philip C.A,Robert M B.Research on distance education:in defense of field experiments.Distance Education.2006,27(1):5-26.
[5]徐盈.即时通信教育平台中负载均衡技术的研究与实现:[硕士学位论文].b北京:北方工业大学,2007.
[6]马丹.即时通信系统终端的设计与实现:[硕士学位论文].成都:电子科技大学,2004
[7]庄严.IP网视频音频实时传输的研究:[硕士学位论文].南京:南京工业大学,2004
[8]张益贞,刘滔.Visual C++实现MPEG/JPEG编解码技术.北京:人民邮电出版社.2002
[9]董振亚,张拥军,彭宇行.基于RTP的MPEG-4视频传输.计算机应用研究.2003,7:52-55.
[10]H.Sehulzrinne,S.Casner,R.Frederick,et al.RTP:A Transport Protocol for Real-Time Applications.RFC 3550.Internet Engineering Task Force.2003.
[11]罗明宇,陶孜谨,卢锡城.RTP在网络视频传输中的实现研究.计算机工程,2000,26(9):65-66.
[12]杨鑫.低速数据网与局域网实时数据传输研究:[硕士学位论文].四川:四川大学电力系统及其自动化,2005
[13]罗杰森(Rogerson,D.).COM技术内幕:微软组件对象模型(,杨秀章译).北京:清华大学出版社,1999.
[14]陆其明.DirectShow开发指南.北京:清华大学出版社.2003:2-52.
[15]陈明宏.基于Directshow的视频监控传输系统:[硕士学位论文].武汉:华中师范大学电路与系统,2005
[16]吴洁明,袁山龙.软件工程应用实践教程.北京:清华大学出版社.2003
[17]何炯.实时传输协议(RTP)的简化设计与实现:[硕士学位论文].四川:西南交通大学计算机应用技术,2003
[18]杨鑫.低速数据网与局域网实时数据传输研究:[硕士学位论文].四川:四川大学电力系统及其自动化,2005
[19]H.Schulzrinne,S.Casner.RTP Profile for Audio and Video Conferences with Minimal Control.RFC 3551.Interact Engineering Task Force.2003
[20]Mark Allen Weiss.数据结构与算法分析(,张怀勇等译).北京:人民邮电出版社,2007.
[21]奚克凡.流媒体软件设计框架下网络视频的研究:[硕士学位论文].浙江:浙江工业大学,2005
[22]张勇.远程视频监控系统的传输技术的实现:[硕士学位论文].成都:电子科技大学,2004.
[23]Jim Beveridge & Robert Wiener.Win32多线程程序设计(,侯捷译).武汉:华中科技大学出版社,2002.
[241]郝文化,文自勇,王浩强,等.WindowS多线程编程技术与实例.北京:中国水利水电出版社,2005.
[25]Hung-Ju Lee,Thhao Chiang,Ya-Qin Zhang.Scalable Rate Control for MPEG-4 Video.IEEE Transactons on Vircuits and Systems for Video Technology,2000,10(6):878-894.
[26]Reza Rejair,Mark Handley,Deborah Estrin.RAP:An End-to-end Rate-based Congestion Control Mechanism for Realtime Streams in the Internet.INFOCOM '99.Eighteenth Annual Joint Conference of the IEEE Computer and Communications Societies.Proceedings.IEEE.1995,3:1337-1345.
[27]Y.Thomas Hou,Shivendra S.Panwar,Zhi-Li Zhang,et al.Network Bandwidth Sharing for Transporting Rate-Adaptive Packet Video Using Feedback.Global Telecommunications Conference,1998.GLOBECOM 98.The Bridge to Global Integration.IEEE,1998,3:1547-1555.
[28]宁兆彬.自适应网络带宽的音视频交互系统研究与实现:[硕士学位论文].汕头:汕头大学计算机软件与理论,2004
[29]陈理.视频会议系统的设计与实现:[硕士学位论文].成都:电子科技大学,2004.
[30]陆其明.DirectShow实务精选.北京:科学出版社.2004
[31]Y.Kikuchi,T.Nomura,S.Fukunaga,et al.RTP Payload Format for MPEG-4 Audio/Visual Streams.RFC 3016.Interact Engineering Task Force.2000.
[32]FengPan,A.Li,K.Lim,et al.A Study of MPEG-4 Rate Control Scheme and Its Improvements.IEEE Transactions on Circuits and Systems for Video Technology.2003,13(5):440-446.
[33]Dapeng Wu,Yiwei Thomas Hou,Wenwu Zhu,et al.On End-to-End Architecture for Transporting MPEG-4 Video over the Internet.IEEE Transactions on Circuits and Systems for Video Technology.2000,10(6):923-941.
[34]Anthony Vetro,Huifang Sun,Yao Wang.MPEG-4 Rate Control for Multiple Video Objects.IEEE Transactions on Circuits and Systems for Video Technology.1999,9(1):186-199.
[35]纪雯.网上视音频信息传输及处理的研究与实现:[硕士学位论文].西安:西北工业大学,2003.
[36]崔莉,王敏,吉逸.流媒体同步机制的研究.计算机应用研究.2005,1:73-75.
[37]吴炜,常义林.在接收端实现的媒体同步控制算法.系统工程与电子技术,2006,28(10):1587-1591.
[38]张立涓.校园网网络教室多媒体信息传输技术的研究:[硕士学位论文].大连:大连海事大学计算机应用技术,2003.
[39]顾俊杰.基于H.323协议的多媒体会议系统关键技术的研究:[硕士学位论文].南京:河海大学.2005.
[40]张刚毅.电子白板功能的设计与实现.现代电子技术.2006,1:140-144.
[41]Hung-Ju Lee,Thhao Chiang,Ya-Qin Zhang.Scalable Rate Control for MPEG-4 Video.IEEE Transactons on Vircuits and Systems for Video Technology,2000,10(6):878-894.
[42]杨宗凯,吴砥,刘清堂.网络教育标准与技术.北京:清华大学出版社,2003:20-55.
[2]张立涓.校园网网络教师多媒体信息传输技术的研究:[硕士学位论文].大连:大连海事大学计算机应用技术,2003
[3]王月娟.多媒体白板系统及其在远程教育中的应用:[硕士学位论文].大连:大连理工大学,2006.
[4]Philip C.A,Robert M B.Research on distance education:in defense of field experiments.Distance Education.2006,27(1):5-26.
[5]徐盈.即时通信教育平台中负载均衡技术的研究与实现:[硕士学位论文].b北京:北方工业大学,2007.
[6]马丹.即时通信系统终端的设计与实现:[硕士学位论文].成都:电子科技大学,2004
[7]庄严.IP网视频音频实时传输的研究:[硕士学位论文].南京:南京工业大学,2004
[8]张益贞,刘滔.Visual C++实现MPEG/JPEG编解码技术.北京:人民邮电出版社.2002
[9]董振亚,张拥军,彭宇行.基于RTP的MPEG-4视频传输.计算机应用研究.2003,7:52-55.
[10]H.Sehulzrinne,S.Casner,R.Frederick,et al.RTP:A Transport Protocol for Real-Time Applications.RFC 3550.Internet Engineering Task Force.2003.
[11]罗明宇,陶孜谨,卢锡城.RTP在网络视频传输中的实现研究.计算机工程,2000,26(9):65-66.
[12]杨鑫.低速数据网与局域网实时数据传输研究:[硕士学位论文].四川:四川大学电力系统及其自动化,2005
[13]罗杰森(Rogerson,D.).COM技术内幕:微软组件对象模型(,杨秀章译).北京:清华大学出版社,1999.
[14]陆其明.DirectShow开发指南.北京:清华大学出版社.2003:2-52.
[15]陈明宏.基于Directshow的视频监控传输系统:[硕士学位论文].武汉:华中师范大学电路与系统,2005
[16]吴洁明,袁山龙.软件工程应用实践教程.北京:清华大学出版社.2003
[17]何炯.实时传输协议(RTP)的简化设计与实现:[硕士学位论文].四川:西南交通大学计算机应用技术,2003
[18]杨鑫.低速数据网与局域网实时数据传输研究:[硕士学位论文].四川:四川大学电力系统及其自动化,2005
[19]H.Schulzrinne,S.Casner.RTP Profile for Audio and Video Conferences with Minimal Control.RFC 3551.Interact Engineering Task Force.2003
[20]Mark Allen Weiss.数据结构与算法分析(,张怀勇等译).北京:人民邮电出版社,2007.
[21]奚克凡.流媒体软件设计框架下网络视频的研究:[硕士学位论文].浙江:浙江工业大学,2005
[22]张勇.远程视频监控系统的传输技术的实现:[硕士学位论文].成都:电子科技大学,2004.
[23]Jim Beveridge & Robert Wiener.Win32多线程程序设计(,侯捷译).武汉:华中科技大学出版社,2002.
[241]郝文化,文自勇,王浩强,等.WindowS多线程编程技术与实例.北京:中国水利水电出版社,2005.
[25]Hung-Ju Lee,Thhao Chiang,Ya-Qin Zhang.Scalable Rate Control for MPEG-4 Video.IEEE Transactons on Vircuits and Systems for Video Technology,2000,10(6):878-894.
[26]Reza Rejair,Mark Handley,Deborah Estrin.RAP:An End-to-end Rate-based Congestion Control Mechanism for Realtime Streams in the Internet.INFOCOM '99.Eighteenth Annual Joint Conference of the IEEE Computer and Communications Societies.Proceedings.IEEE.1995,3:1337-1345.
[27]Y.Thomas Hou,Shivendra S.Panwar,Zhi-Li Zhang,et al.Network Bandwidth Sharing for Transporting Rate-Adaptive Packet Video Using Feedback.Global Telecommunications Conference,1998.GLOBECOM 98.The Bridge to Global Integration.IEEE,1998,3:1547-1555.
[28]宁兆彬.自适应网络带宽的音视频交互系统研究与实现:[硕士学位论文].汕头:汕头大学计算机软件与理论,2004
[29]陈理.视频会议系统的设计与实现:[硕士学位论文].成都:电子科技大学,2004.
[30]陆其明.DirectShow实务精选.北京:科学出版社.2004
[31]Y.Kikuchi,T.Nomura,S.Fukunaga,et al.RTP Payload Format for MPEG-4 Audio/Visual Streams.RFC 3016.Interact Engineering Task Force.2000.
[32]FengPan,A.Li,K.Lim,et al.A Study of MPEG-4 Rate Control Scheme and Its Improvements.IEEE Transactions on Circuits and Systems for Video Technology.2003,13(5):440-446.
[33]Dapeng Wu,Yiwei Thomas Hou,Wenwu Zhu,et al.On End-to-End Architecture for Transporting MPEG-4 Video over the Internet.IEEE Transactions on Circuits and Systems for Video Technology.2000,10(6):923-941.
[34]Anthony Vetro,Huifang Sun,Yao Wang.MPEG-4 Rate Control for Multiple Video Objects.IEEE Transactions on Circuits and Systems for Video Technology.1999,9(1):186-199.
[35]纪雯.网上视音频信息传输及处理的研究与实现:[硕士学位论文].西安:西北工业大学,2003.
[36]崔莉,王敏,吉逸.流媒体同步机制的研究.计算机应用研究.2005,1:73-75.
[37]吴炜,常义林.在接收端实现的媒体同步控制算法.系统工程与电子技术,2006,28(10):1587-1591.
[38]张立涓.校园网网络教室多媒体信息传输技术的研究:[硕士学位论文].大连:大连海事大学计算机应用技术,2003.
[39]顾俊杰.基于H.323协议的多媒体会议系统关键技术的研究:[硕士学位论文].南京:河海大学.2005.
[40]张刚毅.电子白板功能的设计与实现.现代电子技术.2006,1:140-144.
[41]Hung-Ju Lee,Thhao Chiang,Ya-Qin Zhang.Scalable Rate Control for MPEG-4 Video.IEEE Transactons on Vircuits and Systems for Video Technology,2000,10(6):878-894.
[42]杨宗凯,吴砥,刘清堂.网络教育标准与技术.北京:清华大学出版社,2003:20-55.