基于宽带网的DVB接收系统的软件设计及其实现

【作者】 管瑞峰；

【导师】 潘雪增； 平玲娣；

【作者基本信息】 浙江大学 ， 计算机系统结构， 2002， 硕士

【摘要】 DVB体系的应用起始于直播卫星系统，后来逐渐被有线电视系统采用，由于Internet的崛起，有人开始了基于Internet的DVB系统的研究，可是Internet带宽低，错误率高，这些Internet网络固有的局限性，限制了需要大量数据的传播的DVB系统的广泛应用。采用广播电视系统的有线电视高速宽带网络，并且通过利用DVB标准中规定的各种控制信息，以PC机为客户端，实现了基于宽带的DVB接收系统。这个接收系统采用Windows平台，硬件采用专用接收卡接收DVB广播数据；驱动软件部分采用NDIS体系结构，这样的体系结构能够易于在各个Windows平台中移植；应用软件部分采用DirectShow中的过滤器结构，实现了一个SourceFilter，这样可以使用通用的控制媒体播放器MediaPlayer来播放MPEG节目，又能够控制媒体流的播放。通过测试，该DVB接收系统能够同时完成MPEG-2和MPEG-1格式的播放以及文件的下载。 本系统和以往的同类系统或机顶盒方式相比有着以下特点： 1)基于NDIS的驱动部分设计使得本系统能够在各个Windows平台上面进行方便的移植，而不需要修改太多的源代码。 2)采用多级缓存方式，解决了播放速度暂时不匹配和包重组缓存问题。系统采用核心态一级缓存和用户态二级缓存的设计方式，使得在发送数据速率和播放速率暂时不一致的情况下能够顺利播放，使得二级缓存中的缓存数据量整体保持在一个稳定的水平。 3)采用分级处理的方式使得各个模块的功能明确，便于修改和升级。比如小端口驱动只负责和接收卡的通讯和包的接收，而包的重新组合则在协议层完成，这样如果需要增加一种播放类型则不需要修改小端口层。 4)媒体播放采用Windows自带的MediaPla控件，文件下载和浏览都采用IE浏览器，这样使得所有操作都是所有Windows用户所熟悉的，也是友好的。 实现本系统就能使得以往的DVB接收由机顶盒硬件方式转变成软件方式，扩大了DVB系统的使用范围，便于数字电视的更快发展。更多还原

【Abstract】 The application of DVB system which started with satellite living broadcast system was adoptted by CATV gradually. By the growing up of Internet, DVB system based on llnternet became the research object of researchers and engineers. However, narrow band and high error rate of Internet limited the application of DVB system which should transport lots of data on network. Nowadays high-speed broadband network of CATV is used to realize DVB system whose client is personal computer. We developed the client software of this DVB system which was based on windows platform. The hardware used in client is a DVI3 receive card and the archecture of the receive card driver is NDIS which makes the driver can be migrated in different windows platforms easily. The application software part is based on filter structure in Directshow and we developed a source filter through which ~ve can control the playing back of the mediaplayer. By our test, the DVB receive system can play back the MPEG-2 and MPEG-I vedio and download files. The softe-vare part of the DVB receiving system has following advantages. 1) The design of driver based on NDIS make it easy that the software can be migrated in different windows platforms without too much modification. 2) Multi-level buffer is used to resolve the problem of slow play and packet re-assemble. The system use one buffer in kernel mode and one buffer in user mode which makes the movie can be played frequently when there is any speed difference between sending and receiving. 3) Multi-level software module is used which makes the system can be updated and modified easily. For example, miniport dirver answers for the communication to receiving card and the receiption of TS packet without re-assembling the TS packet to PS packet. So if a new kind of media type is demanded in this system, the miniport driver part of the system should not be aniniended. 4) MediaPlayer and IE are the most popular software built in windows operating system. So the software using these tools are friendly to users.更多还原