基于P2P的远程教学直播系统设计与实现
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摘要
远程教学直播系统是现代远程教育的基础平台,它能够实时采集教师授课时的屏幕图像、视频和音频数据,通过压缩后实时向远程直播,从而实现远程实时课堂。实现流媒体数据的高效采集,更有效地利用服务器的处理能力,支持尽可能多的在线用户数量,成为研制远程教学直播系统的关键。
目前国内市场上已有一些远程教学直播系统产品,其中较为成熟的是基于C/S模式的PowerCreator,其特点是具有高效地流媒体数据采集效率。但由于该系统基于C/S模式,当用户数量增加时,系统易出现性能瓶颈,导致服务质量降低。
为支持尽可能多的在线用户数量,充分利用服务器的处理能力,基于对等网络(P2P)的解决方案是一种有效的途径。据此,实现了基于P2P的远程教学直播系统,以P2P的方式在网络上传输流媒体数据。由于服务器不再需要为每一个客户端直接发送数据,因而降低了服务器的压力,增加了在线的用户人数。从另一方面来看,在相同用户数的条件下,基于P2P的远程教学直播服务器对网络带宽和服务器处理能力要求明显降低,因而降低了系统的硬件成本。
采用了PowerCreator的基于虚拟显卡的底层驱动抓屏方法,快速有效的抓取屏幕上变化区域的图像数据,做到了实时连续捕捉屏幕,提高了屏幕数据的采集效率;采用具有高压缩比的JPEG压缩算法对捕捉到的屏幕数据进行压缩,采用经典的MPEG-4压缩算法对采集的视频和音频数据进行压缩,减小了需要在网络上传输的数据量,实现了流媒体数据的高效采集。
经过对系统的测试表明,系统对流媒体数据的采集效率与PowerCreator相当。在相同在线人数的条件下,基于P2P的解决方案较之C/S模式降低了对服务器CPU和网络带宽的占用率。从而可以解决基于C/S模式当用户数量增加系统性能下降的问题。
Distance education live-cast system was the foundation of modern distance education. The data of teachers’screen ,video and audio could collected by it and broadcasted to remote client after compressed. Realized remote real-time classroom. How to improve the collection efficiency of streaming media data and transmission in a more effective way was a urgent problems to solve in designing distance education system.
At present, the domestic market has some distance learning broadcast systems. PowerCreater was the mature products which based on Client/Server(C/S). Highly Streaming Media data collection efficiency was PowerCreater’s feature. But because of it based on C/S, lower quality of service was easy led by system performance bottleneck when the number of users increases,
The solution which based on peer-to-peer network was an effective way to support more users as possible and make full use of the server capacity. Accordingly, a distance learning broadcast system which based on P2P was realized and the media data was transmitted in the form of P2P. Because each server is no longer a need for direct delivery of client data, thereby the pressure of server was reduced, and the number of users online was increased. From another side, the cost of hardware was reduced for the system which based on P2P require lower network bandwidth and server capacity.
The method of capturing screen which in virtual display driver can grasp the changed image data on screen ,and the collection efficiency of the data was improved by use the method. The screen data was compressed by using the JPEG compression algorithm. The video data and the audio data was compressed by using MPEG-4 compression algorithm. The data need to transmit was reduced after been compressed.
The test of the system shows that the system for the efficient collection of data streaming media. Meanwhile it is a effective solution based on C/S system performance falling when the number of users to increase.
目前国内市场上已有一些远程教学直播系统产品,其中较为成熟的是基于C/S模式的PowerCreator,其特点是具有高效地流媒体数据采集效率。但由于该系统基于C/S模式,当用户数量增加时,系统易出现性能瓶颈,导致服务质量降低。
为支持尽可能多的在线用户数量,充分利用服务器的处理能力,基于对等网络(P2P)的解决方案是一种有效的途径。据此,实现了基于P2P的远程教学直播系统,以P2P的方式在网络上传输流媒体数据。由于服务器不再需要为每一个客户端直接发送数据,因而降低了服务器的压力,增加了在线的用户人数。从另一方面来看,在相同用户数的条件下,基于P2P的远程教学直播服务器对网络带宽和服务器处理能力要求明显降低,因而降低了系统的硬件成本。
采用了PowerCreator的基于虚拟显卡的底层驱动抓屏方法,快速有效的抓取屏幕上变化区域的图像数据,做到了实时连续捕捉屏幕,提高了屏幕数据的采集效率;采用具有高压缩比的JPEG压缩算法对捕捉到的屏幕数据进行压缩,采用经典的MPEG-4压缩算法对采集的视频和音频数据进行压缩,减小了需要在网络上传输的数据量,实现了流媒体数据的高效采集。
经过对系统的测试表明,系统对流媒体数据的采集效率与PowerCreator相当。在相同在线人数的条件下,基于P2P的解决方案较之C/S模式降低了对服务器CPU和网络带宽的占用率。从而可以解决基于C/S模式当用户数量增加系统性能下降的问题。
Distance education live-cast system was the foundation of modern distance education. The data of teachers’screen ,video and audio could collected by it and broadcasted to remote client after compressed. Realized remote real-time classroom. How to improve the collection efficiency of streaming media data and transmission in a more effective way was a urgent problems to solve in designing distance education system.
At present, the domestic market has some distance learning broadcast systems. PowerCreater was the mature products which based on Client/Server(C/S). Highly Streaming Media data collection efficiency was PowerCreater’s feature. But because of it based on C/S, lower quality of service was easy led by system performance bottleneck when the number of users increases,
The solution which based on peer-to-peer network was an effective way to support more users as possible and make full use of the server capacity. Accordingly, a distance learning broadcast system which based on P2P was realized and the media data was transmitted in the form of P2P. Because each server is no longer a need for direct delivery of client data, thereby the pressure of server was reduced, and the number of users online was increased. From another side, the cost of hardware was reduced for the system which based on P2P require lower network bandwidth and server capacity.
The method of capturing screen which in virtual display driver can grasp the changed image data on screen ,and the collection efficiency of the data was improved by use the method. The screen data was compressed by using the JPEG compression algorithm. The video data and the audio data was compressed by using MPEG-4 compression algorithm. The data need to transmit was reduced after been compressed.
The test of the system shows that the system for the efficient collection of data streaming media. Meanwhile it is a effective solution based on C/S system performance falling when the number of users to increase.
引文
[1] Marvin J. Croy Distance education, individualization, and the demise of the university, Technology In Society-1998 (20),317-326.
[2] Monson H. Hayes Michael. Mayercik. Distance learning across the Atlantic, IEEE Transaction on Education, VOL. 44, NO. 2, MAY 2001
[3] Mahbubur Rahman. Diminishing the distance in distance education , IEEE Multimedia 2001 (3), 18-20
[4]沈显君,归伟夏,冯刚等.基于Internet的远程教育软件的设计与实现[J].计算机应用研究.1999,5:20-22
[5]王艳丽,鲜继清,白洁.基于P2P的流媒体技术[J].计算机应用,2005,25(6):1267-1230
[6] Silverston, T; Fourmaux, O; Source vs Data-driven Approach for Live P2P Streaming [J]. Networking International Conference on Systems and International Conference on Mobile Communications and Learning Technologies, 2006, 4:99-105
[7]伍华健.P2P技术在远程教育系统开发中的应用研究[J].计算机科学.2006,3(39):287-290
[8] Kothapalli, K.; Scheideler, C.; Supervised peer-to-peer systems. IEEE Parallel Architectures, Algorithms and Networks, 2005. ISPAN 2005. Proceedings. 8th International Symposium on 7-9 Dec. 2005 Page(s):6
[9] Chan S H G, Tobagi F. Distributed serves architecture for networked video services[J]. Networking, IEEE/ACM Transactions, 2001,9(2):125-136
[10] Tay Y C, Hweehwa P.Load sharing in distributed multimedia-on-demand systems[J]. Knowledge and Data Engineering, IEEE Transactions. 2000,12(3):410-428
[11] Krishnamurthy R, Schwan K, West R, et al. On network Coprocessors for scalable, predictable media services[J]. Parallel and Distributed Systems, IEEE Transactions, 2003, 14(7):655-670
[12]朱秋萍,王亚楠,罗云峰. IP网络内不支持组播路由的流媒体通信研究.武汉大学学报(理学版)[J]. 2004,50(5):384-388
[13] Park J,Seok J K, Shin G K.. Multicast delivery based on unicast and subnet multicast[J]. IEEE Communications Letters, 2001,5(4):181-183
[14] Yang hua Chu, S G Rao, Seshan S Hui Zhang. A Case for End System Multicast [J]. IEEE Journal on Selected Areas in Communication (JSAC), 2002, 20(8): 1456-1471
[15] J. Jannotti ,et al. Overcast : Reliable multicasting with an overlay network1 In : Proc. USENIX OSDI Los Alamitos , California :IEEE Computer Society Press ,2000
[16] D. Pendarakis ,et al. ALMI : An application level multicast in-frastructure1 In: Proc 3rd USENIX Symposium on Internet Technologies1 Los Alamitos , California : IEEE Computer Society Press , 2001
[17] H. Deshpande , M. Bawa , H. Garcia-Molina. Streaming live media over a peer-to-peer network. Standford Database Group ,Tech1 Rep1 : 2001230 , 2002
[18] M. Castro, et al. Split Stream: High-bandwidth content distribution in a cooperative environment. In: Proc. IPTPS. Los Alamitos , California : IEEE Computer Society Press , 2003
[19] X. Jiang , Y. Dong , D. Xu , et al. GnuStream: A P2P media streaming system prototype. In : Proc. 4th ICME’031 Los Alamitos , California : IEEE Computer Society Press , 2003
[20] M. Hefeeda , A. Habib , B. Botev , et al. PROMISE : A peer to peer media streaming using CollectCast1 In : Proc. ACM MM’03. New York : ACM Press , 2003
[21] Zhang X, Liu J, Li B, et al. CoolStreaming/DONet: A Data-driven Overlay Network for Live Media Streaming [J]. IEEE INFOCOM, 2005, 1:2103-2111
[22] Igarashi, D.; Tsuchiya, T.; Kikuno, T. Overlay network topologies for gossip-based multicast. Parallel and Distributed Systems[J], 2005.Proceedings.11th International Conference on Volume 1, 2005, 1:2-7
[23]吴洪才,殷人昆,贺思德.屏幕捕获技术在多媒体教学中的实现探讨[J].计算机工程,2003,29(13):195-196
[24]姜超. Intel IPP库在视频编码中的应用[J].数字电视与数字视频,2003 , (11) :35-37
[25]纪雯,卢选民,史浩山.基于自适应控制的实时视频传输处理系统研究[J].计算机工程与应用,2004,(31):156-158
[26]汤力,余松煜. MPEG-4自然视频编码技术[J].红外与激光工程,2002,31(5):461-463
[27]黄磊,周海骄.多媒体通信新标准MPEG-4[J].信息技术,2003,27(4):2-5
[28] Touradj E, Caspar H. MPEGv-4 natural video coding– an overview[J]. Signal Processing: Image Communication, 2000,(15):365-385
[29]钟玉琢,王琪,贺玉文.基于对象的多媒体数据压缩编码国际标准-MPEG-4及其校验模型[M].北京:科学出版社,2000.1-471
[30]陈功,黄祥林,卓力. MPEG-4基于对象的多媒体压缩新标准[J].测控技术,2002,21(5):26-29
[31]周敬利,姚超,余胜声. MPEG-4视频标准及其在可视电话中的应用[J].小型微型计算机系统,2000,21(6):577-580
[32] Thomas M, King N N. Automatic segmentation of moving object for video object plane generation[J]. IEEE Trans Circuits Syst Video Technol, 1998,8(5):525-538
[33] Zhong D,Change S F. AMOS: an active system for MPEG-4 video object segmentation[A]. In: Benois-Pineau J, Braquelaire J P. International Conference on Image Processing[C]. Chicago: IEEE Computer Society,1998:647-651
[34]田毅珂,卢朝阳,高西全. MPEG4视频标准及其关键算法[J].现代电子技术,2002,(1):38-41
[35]王猛,张春田. MPEG-4视频编码及其在交互式多媒体通讯中的应用[J].天津通信技术,1998,(2):9-11
[36]赵刚,林瑶,蒋慧译.用TCP/IP进行网际互联第三卷:客户-服务器编程与应用
[37]赵敏,何华灿,张剑.基于视频发送端速率控制的Qos技术研究[J].计算机工程与应用,2004,(27):38-41
[38] IETF/RFC 1889-1996,RTP: A Transport protocol for real-time applications[S]
[39]李华,戴琼海.现场直播多编码器压缩编码的研究[J].计算机工程与应用,2004,(5):122-124
[40]李辉,胡瑞敏,艾浩军等.基于RTP的多媒体流的自适应传输[J].计算机工程与应用,2004,(5):174-156
[2] Monson H. Hayes Michael. Mayercik. Distance learning across the Atlantic, IEEE Transaction on Education, VOL. 44, NO. 2, MAY 2001
[3] Mahbubur Rahman. Diminishing the distance in distance education , IEEE Multimedia 2001 (3), 18-20
[4]沈显君,归伟夏,冯刚等.基于Internet的远程教育软件的设计与实现[J].计算机应用研究.1999,5:20-22
[5]王艳丽,鲜继清,白洁.基于P2P的流媒体技术[J].计算机应用,2005,25(6):1267-1230
[6] Silverston, T; Fourmaux, O; Source vs Data-driven Approach for Live P2P Streaming [J]. Networking International Conference on Systems and International Conference on Mobile Communications and Learning Technologies, 2006, 4:99-105
[7]伍华健.P2P技术在远程教育系统开发中的应用研究[J].计算机科学.2006,3(39):287-290
[8] Kothapalli, K.; Scheideler, C.; Supervised peer-to-peer systems. IEEE Parallel Architectures, Algorithms and Networks, 2005. ISPAN 2005. Proceedings. 8th International Symposium on 7-9 Dec. 2005 Page(s):6
[9] Chan S H G, Tobagi F. Distributed serves architecture for networked video services[J]. Networking, IEEE/ACM Transactions, 2001,9(2):125-136
[10] Tay Y C, Hweehwa P.Load sharing in distributed multimedia-on-demand systems[J]. Knowledge and Data Engineering, IEEE Transactions. 2000,12(3):410-428
[11] Krishnamurthy R, Schwan K, West R, et al. On network Coprocessors for scalable, predictable media services[J]. Parallel and Distributed Systems, IEEE Transactions, 2003, 14(7):655-670
[12]朱秋萍,王亚楠,罗云峰. IP网络内不支持组播路由的流媒体通信研究.武汉大学学报(理学版)[J]. 2004,50(5):384-388
[13] Park J,Seok J K, Shin G K.. Multicast delivery based on unicast and subnet multicast[J]. IEEE Communications Letters, 2001,5(4):181-183
[14] Yang hua Chu, S G Rao, Seshan S Hui Zhang. A Case for End System Multicast [J]. IEEE Journal on Selected Areas in Communication (JSAC), 2002, 20(8): 1456-1471
[15] J. Jannotti ,et al. Overcast : Reliable multicasting with an overlay network1 In : Proc. USENIX OSDI Los Alamitos , California :IEEE Computer Society Press ,2000
[16] D. Pendarakis ,et al. ALMI : An application level multicast in-frastructure1 In: Proc 3rd USENIX Symposium on Internet Technologies1 Los Alamitos , California : IEEE Computer Society Press , 2001
[17] H. Deshpande , M. Bawa , H. Garcia-Molina. Streaming live media over a peer-to-peer network. Standford Database Group ,Tech1 Rep1 : 2001230 , 2002
[18] M. Castro, et al. Split Stream: High-bandwidth content distribution in a cooperative environment. In: Proc. IPTPS. Los Alamitos , California : IEEE Computer Society Press , 2003
[19] X. Jiang , Y. Dong , D. Xu , et al. GnuStream: A P2P media streaming system prototype. In : Proc. 4th ICME’031 Los Alamitos , California : IEEE Computer Society Press , 2003
[20] M. Hefeeda , A. Habib , B. Botev , et al. PROMISE : A peer to peer media streaming using CollectCast1 In : Proc. ACM MM’03. New York : ACM Press , 2003
[21] Zhang X, Liu J, Li B, et al. CoolStreaming/DONet: A Data-driven Overlay Network for Live Media Streaming [J]. IEEE INFOCOM, 2005, 1:2103-2111
[22] Igarashi, D.; Tsuchiya, T.; Kikuno, T. Overlay network topologies for gossip-based multicast. Parallel and Distributed Systems[J], 2005.Proceedings.11th International Conference on Volume 1, 2005, 1:2-7
[23]吴洪才,殷人昆,贺思德.屏幕捕获技术在多媒体教学中的实现探讨[J].计算机工程,2003,29(13):195-196
[24]姜超. Intel IPP库在视频编码中的应用[J].数字电视与数字视频,2003 , (11) :35-37
[25]纪雯,卢选民,史浩山.基于自适应控制的实时视频传输处理系统研究[J].计算机工程与应用,2004,(31):156-158
[26]汤力,余松煜. MPEG-4自然视频编码技术[J].红外与激光工程,2002,31(5):461-463
[27]黄磊,周海骄.多媒体通信新标准MPEG-4[J].信息技术,2003,27(4):2-5
[28] Touradj E, Caspar H. MPEGv-4 natural video coding– an overview[J]. Signal Processing: Image Communication, 2000,(15):365-385
[29]钟玉琢,王琪,贺玉文.基于对象的多媒体数据压缩编码国际标准-MPEG-4及其校验模型[M].北京:科学出版社,2000.1-471
[30]陈功,黄祥林,卓力. MPEG-4基于对象的多媒体压缩新标准[J].测控技术,2002,21(5):26-29
[31]周敬利,姚超,余胜声. MPEG-4视频标准及其在可视电话中的应用[J].小型微型计算机系统,2000,21(6):577-580
[32] Thomas M, King N N. Automatic segmentation of moving object for video object plane generation[J]. IEEE Trans Circuits Syst Video Technol, 1998,8(5):525-538
[33] Zhong D,Change S F. AMOS: an active system for MPEG-4 video object segmentation[A]. In: Benois-Pineau J, Braquelaire J P. International Conference on Image Processing[C]. Chicago: IEEE Computer Society,1998:647-651
[34]田毅珂,卢朝阳,高西全. MPEG4视频标准及其关键算法[J].现代电子技术,2002,(1):38-41
[35]王猛,张春田. MPEG-4视频编码及其在交互式多媒体通讯中的应用[J].天津通信技术,1998,(2):9-11
[36]赵刚,林瑶,蒋慧译.用TCP/IP进行网际互联第三卷:客户-服务器编程与应用
[37]赵敏,何华灿,张剑.基于视频发送端速率控制的Qos技术研究[J].计算机工程与应用,2004,(27):38-41
[38] IETF/RFC 1889-1996,RTP: A Transport protocol for real-time applications[S]
[39]李华,戴琼海.现场直播多编码器压缩编码的研究[J].计算机工程与应用,2004,(5):122-124
[40]李辉,胡瑞敏,艾浩军等.基于RTP的多媒体流的自适应传输[J].计算机工程与应用,2004,(5):174-156
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