摘要
随着网络的迅速发展，人们对视频的需求越来越强烈。视频服务对带宽的要求很高，使得这些服务不能在Internet上得到很好地应用，而CATV网能够提供稳定高速的下行带宽。如何结合CATV网和IP网的优点，提供高质量的视频服务，是本论文研究的内容。
本论文的工作主要体现在以下方面：
1)提出了集成CATV和IP网络、具有交互功能的组播视频系统技术方案。
2)利用CATV网作为高速下行通道，基于组播机制，采用SAP／SDP协议实现传输节目的宣告和描述，节目的传输包括视频流的高速稳定传输和视频文件的可靠传输。该方法有效地解决了单向CATV网中视频传送和接收的协调问题。
3)利用Internet网作为交互链路，提供视频点播、视频BBS等交互功能。其中，交互的部分通过Internet传送，包括视频点播中的点播请求、视频BBS中的文字聊天部分；视频流通过CATV网传送，包括点播的视频流、视频BBS的视频流。这种机制既保证了交互性，又保证了视频流的高速稳定传输。
4)提出了基于Agent的文件分发模型，实现整个系统信源加载的自动化和智能化。
该组播视频系统已经在“浙江省信息化科技村镇建设与示范”项目中得到应用，并在浙江省绍兴县杨汛桥镇开始试运行，运行期间平台稳定，得到了用户的好评。
本文首先介绍了组播视频系统的整体框架，然后对其中的关键技术和主要模块进行了详细的介绍，在第五章，给出了应用实例，最后，对系统进行总结和展望。
With the development of network technology and application, video-related applications attract more and more interests from people. Due to the requirements of stable and high bandwidth, the video service can't be widely employed in Internet. However, the CATV network can provide the stable and high-bandwidth downstream channel. The topic of this thesis is how to integrate the CATV network with Internet to provide multicast video services with high qualities.
My main works include four important aspects:
1) A multicast video platform, which combines CATV network with Internet network, is proposed with the characteristic of interaction.
2) Delivering two types of data on the CATV network as downstream channel-the datagrams based on the SAP/SDP protocols for announcing and describing the video program, and the programs, which include the video file transmitted based on the reliable multicast technique, and the video streaming transmitted with the qualities of stability and high-speed based on the multicast technique. Guaranteed by this mechanism, the video sending and receiving are effectively correspond with each other in the single-direction CATV network.
3) Providing the interactive services via the Internet as interactive channel, such as video on demand, video chat. The interactive messages, such as the demand request in video on demand and the plain text in video chat, are delivered over the Internet. The video streaming involved in video on demand and video chat, is delivered over the CATV network. The mechanism ensures the interactivity and the stably, high-speed delivering of video streaming.
4) The file distributing model based on Agent technology is proposed, over which the content of the platform is loaded in an automatic and intelligent manner.
The multicast video platform is designed and implemented to satisfy the above for requirements, which has been employed in the system of the informationalization of village in Zhejiang province, and tested run in the town of Yangxun bridge. The platform is accepted by the users because of the fine effects of the video services.
The paper begins with an introduction of the framework of the multicast video platform. In the following chapters, the key techniques in our platform for the above four requirements are interpreted, and based on the research of the techniques, the design and implements of main modules are depicted. In chapter 5, the application of our platform is introduced briefly. At last, a summary of current work and the future work are proposed.
引文
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