【作者】 苗国明；

【导师】 付晓玲；

【作者基本信息】 北方工业大学 ， 计算机应用技术， 2008， 硕士

【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。更多还原

【Abstract】 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.更多还原