【作者】 翁肇杰；

【导师】 陈春法；

【作者基本信息】 华东师范大学 ， 计算机应用技术， 2004， 硕士

【摘要】 远程教育是网络多媒体技术应用的一个重要方向。它突破了时间和空间的限制，为广大的学习者提供了极大的方便。 网络视频教育是远程教育的一个重要组成部分，它实现了师生们在网络上的视频和音频交流。它有三种实现方式：纯硬件方案、纯软件方案和软硬结合的方案。 现阶段我国的网络多媒体教育得到了广泛的运用，但是在实现网络视频教育时，还存在着如下一些问题： 1．纯硬件网络视频教育方案成本过高，不能为普通用户接受，限制了它的推广，也不便于升级换代。 2．纯软件网络视频教育方案视频和音频质量不高，不支持异步教学和多点视频通讯。 3．无论是纯硬件方案还是纯软件方案，它们所采用的视频和音频编解码器都遵循H.323标准，所输出的媒体数据格式较为单一，不能适应用户需求和网络环境的变化。 针对上述问题，本文提出了基于DirectShow技术的网络视频教育方案。该方案是一个纯软件方案，它克服了以前软件方案的缺点，所作的工作主要有以下几方面： 1．使用廉价的设备替代原有的专业设备，利用软件来实现视频音频的捕获、编码和录制。 2．提供对MPEG-4、MP3等先进编码技术的支持，实现这些媒体数据流的网络传输。 3．兼容多种编码器，并提供对编码器属性和视频音频质量的配置方式。 4．提供对同步和异步教学模式的支持，并使用组播来实现多点通讯。 本文主要介绍了方案三个层次的实现： 1．用户界面层。它提供程序的界面，让用户可以根据自身和环境的需要对各类设备和编码器进行选择和配置。 2．Graph管理层。这层中，本文在DirectShow所提供的底层API基础上，设计了一系列完成特定功能的高级函数，供用户界面层调用。 3．Filter层。在这层中，本文设计了一个网络传输Filter，来实现媒体数据的网络发送和接收。网络传输Filter对各类媒体数据进行RTP数据报封装，并对MPEG-4数据进行特殊的分片处理；在接收时，使用异步接收方式、多重缓冲和多线程技术来提高系统的性能。并且它使用COM技术开发，有很好的扩展性。 经过实际运行和测试，本方案完全达到了设计的要求。Directshow网络视频教育方案的实现 本文的研究意义在于:使用最新的Directshow技术，以纯软件的方式，来实现网络视频教育。方案的成本低，视频和音频质量好，兼容性强，配置灵活，能适应不同网络带宽，由于方案采用的是层次型结构，因而也提高了它的扩展性。更多还原

【Abstract】 Remote education is an important part of the network multimedia technique. It breaks through the limitation of the space-time and brings great convenience to the learners.The network video education plays an important role in the remote education. It realizes the communication of the video/audio on the network between the teachers and students. There are three ways to implement the network video education: hardware solution, software solution and hardware-software solution.Remote education has been widely used in our country, but there are still some problems in the realization of the network video education:1. The cost of the hardware solution of the network video education is too high for the users.2. The video/audio quality of the software solution can not satisfy the users. And the software solution doesn’t support asynchronism education and multicast.3. The codecs used in the hardware solution and software solution follow the H.323 standard. The output media format is so simplex that it can not adapt well to the change of the users’ requirement and network condition.Aiming at these problems, this paper designed a software solution of network video education which was developed with DirectShow. This software solution overcomes the shortcomings of the software solution before , it accomplishes the following work:1. Replacing the special and expensive equipments by the cheap ones, using software to capture, encode/decode, and record the video/audio data.2. Supporting MPEG-4 and MP3 codec, designing the network transmit method of these media data.3. Providing the compatibility for kinds of codecs, and the configuration of these codecs and video/audio’s quality.4. Supporting synchronism education, asynchronism education and multicast. This paper is mainly about the three layers’ design of the solution:1. UI layer. It provides the user interface, which allows the users configuring the devices and the codecs to meet their requirement.2. Graph manager layer. In this layer, to serve for the UI layer, this paper designed a series ofhigh level functions based on the DirectShow API.3. Filter layer. In the Filter layer, this paper designed a network transmit filter to implement the media data’s transmission. The network transmit filter encapsulates the media data into the RTP packets, and uses special method to separate the MPEG-4 data. When receiving media data, it uses asynchronism receiving mode, multi-cache and multi-thread to improve the system performance. And because it is developed with COM, it has better expansibility.The purpose of this paper is: designing a software solution of network video education with the advanced DirectShow technique. The features of this solution are: low cost, better Video/Audio quality, compatibility for more codecs, kinds of configurations which allow users doing different tasks and adjustment for the change of network condition.更多还原