基于MPEG-4的多媒体网络教学系统

【作者】 金银琴；

【导师】 杨东勇；

【作者基本信息】 浙江工业大学 ， 计算机应用技术， 2004， 硕士

【摘要】 信息时代给人类社会带来了新的挑战和机遇，传统的以教师、课堂、课本为中心的教学模式将越来越不适应信息社会的需要。随着计算机技术和网络技术的飞速发展，利用网络进行教学已经成为一种必然趋势。多媒体网络教学系统是开展多媒体网络教学的支撑环境。本文对目前的一些多媒体网络教学系统进行了分析讨论，结合校园网络教学的特点，设计开发了一套基于MPEG-4的多媒体网络教学系统。 系统的设计目标是在校园网上建立虚拟的网络课堂，使地理上分散的学生和教师能在同一时间里加入虚拟网络课堂，进行教学活动。教师使用该系统在网络虚拟课堂上授课，学生不但可以同步的看到教师机的屏幕内容、听到教师授课的声音，而且可以看到教师授课时的形象和动作。同时，该系统还提供电子白板讨论功能，为网络分布式教学提供了一种良好的交互环境。所设计的系统具有视音频广播、屏幕图像广播、课件制作等功能。系统的实现综合采用了MPEG-4技术、流媒体技术、网络技术、数据库技术和同步多媒体集成语言SMIL等，采用微软的Visual C++作为开发工具。对所开发的系统进行了功能单元测试和实际的系统联机测试，结果表明系统性能可以满足网络教学的基本要求。 系统实现中解决的关键问题和特色主要有以下几个方面： (1)在视音频直播功能的实现中，通过使用北京算通公司的CV500视频采集卡和CV500 SDK进行视音频数据采集，并采用当今最新的图像和语音编码压缩标准MPEG-4作为视音频数据的采集格式，既保证了图像的质量，又大大缩减了视音频所占的带宽，从而解决了多媒体数据量大、网络带宽利用率低的问题；同时，通过设置环形缓冲区的办法来调和网络传输延时与图像质量之间的矛盾，取得了较好的效果。 (2)在屏幕图像直播功能的实现中，通过采用“屏幕拷贝法”，解决了课件的多媒体链接和屏幕滚动难以控制问题。 (3)在课件实时制作功能的实现中，通过采用SMIL语言制作了一个图形化的SMIL编辑工具，为教师提供一个操作简单的SMIL文档制作编辑环境；用SMIL和RealOne播放器实现了视音频流、图像流在客户端的同步播放。更多还原

【Abstract】 New challenges and opportunities are brought to humanity society in Information era. Traditional teaching mode centers on teacher, classroom and textbook will gradually be unfit for the need of Information era. With the rapid development of both computer and networks technology, networks teaching will be a certain trend. The thesis analyses some contemporary multimedia networks teaching system, and designs a multimedia networks teaching system based on MPEG-4, combined with the characteristic of networks teaching on campus.The aim of this thesis is to build a virtual networks classroom on campus network. By which, students and teachers in different places can join in the teaching activity at the same time. With the system, students can not only receive the contents of the teacher’s screen, voice but also receive the video of the teacher’s movement. Meanwhile, the system provides the function of electronic whiteboard for communication. The designed system includes functions of audio and video broadcast, screen image broadcast, interaction of electronic whiteboard, real-time courseware making, etc. The realization of the system relies on technologies of MPEG-4, streaming media, network, database, SMIL and takes Visual C++ of Microsoft as the development tool. Results of functional unit testing and practical system networking testing show that the system can fulfill the networks teaching requirement.The characteristic and key technologies of the system are as follows:(1) In realizing the live broadcast of audio and video, the problem of immense multimedia data and low networks bandwidth utilizationratio is solved by using MPEG-4 as format of audio and video data. Audio and video data are collected by video card CV500 which developed by Beijing Sum tone Company; meanwhile, the contradictory between the delay of networks transmitting and the quality of the image is well solved by setting a "bi-buffer area".(2) In realizing the live broadcast of the screen image, multimedia interlinkage and screen rolling control is accomplished by "screen-copying".(3) In realizing real-time courseware making, a graphical editing tool of SMIL is made by SMIL language, providing a simple text editing environment; the live broadcast of audio and video stream, image stream and text stream in client realizes by using SMIL and Realone player.更多还原