数字有线电视DVB-C信道编码器与解码器

课程设计说明书 第I页

数字有线电视DVB-C信道编码器与解码器

摘要

数字电视，是将传统的模拟电视信号经过抽样、量化和编码转换成用二进制数代表的数字式信号，然后进行各种功能的处理、传输、存储和记录，也可以用电子计算机进行处理、监测和控制。采用数字技术不仅使各种电视设备获得比原有模拟式设备更高的技术性能，而且还具有模拟技术不能达到的新功能，使电视技术进入崭新时代。

从数字电视的发展和基本组成，引出有线数字电视系统的基本构成和标准，本课题主要按照DVB-C接收数字电缆电视的技术标准设计并实现“标准清晰度数字电视机顶盒”中的信道编码器与解码器，本课题着重分析了有线数字电视DVB-C的信道编码与解码。

关键字：数字电视，信道编码，解码

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目 录

1 绪论···························································································································· 1 1.1 数字电视机的概述 ····························································································· 1 1.2数字电视广播系统的组成及分类 ······································································ 1 2有线数字电视············································································································· 2 2.1有线数字电视基本的构成 ·················································································· 2 2.2有线数字电视基本的标准 ·················································································· 3 2.3 DVB-C标准简述 ································································································· 4 2.3 .1 DVB-C发射系统 ························································································· 4 2.3.2 DVB-C接收系统 ·························································································· 5 3有线数字电视的编码与解码····················································································· 5 3.1信道编码 ·············································································································· 5 3.1.1信道编码的作用···························································································· 5 3.1.2数据随机化···································································································· 6 3.1.3 RS编码算法 ·································································································· 6 3.1.4 数据交织······································································································· 7 3.2 DVB-C信道解码技术 ························································································· 8 3.2.1 解交织··········································································································· 9 3.2.2 RS解码 ·········································································································· 9 3.2.3 解扰··············································································································· 9 总结······························································································································ 11 致谢······························································································································ 12 参考文献······················································································································ 13

课程设计说明书 第1页

1 绪论

1.1 数字电视机的概述

电视技术，经历着从黑白电视到彩色电视的发展过程，数字电视是继黑白电视和彩色电视之后的第三代电视。所谓数字电视，是将传统的模拟电视信号经过抽样、量化和编码转换成用二进制数代表的数字式信号，然后进行各种功能的处理、传输、存储和记录，也可以用电子计算机进行处理、监测和控制。采用数字技术不仅使各种电视设备获得比原有模拟式设备更高的技术性能，而且还具有模拟技术不能达到的新功能，使电视技术进入崭新时代。

近十多年来，由于微电子技术、超大规模集成电路技术、数字信号处理技术、计算机技术的突飞猛进，使数字电视的发展已取得了令人鼓舞的成果。特别是数字图像获取、数字存储、位图打印和图形显示的数字设备的出现,带来了许多数字图像方面的应用。数字电视利用MPEG标准中的各种图像格式，把现行模拟电视制式下的图像、伴音信号的平均码率压缩到大约4.69―21Mbps，其图像质量可以达到电视演播室的质量水平，胶片质量水平，图像水平清晰度达到500―1200线以上，并采用AC―3声音信号压缩技术，传输5.1声道的环绕声信号。

数字电视与模拟电视相比具有许多优点，主要表现在以下几个方面：? ⑴图像和伴音质量高、抗干扰能力强； ⑵频道数量将成数倍增加； ? ⑶可开展多功能业务；? ⑷操作性强； ⑸便于网络化；

⑹具有开放性和兼容性； ⑺易于实现条件接收。? 1.2数字电视广播系统的组成及分类

数字电视系统由信源、信源编码器、信道编码器、信道、信道解码器、信源解码器、信宿等部分组成，如图1所示。

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图1数字通信系统的组成框图

数字电视广播系统包括有线数字电视广播，卫星数字电视广播系统和地面数字电视广播系统三种传输系统。卫星和有线数字广播系统的信道编码和高频调制技术国标已有公认的，优化的方式，就是DVB-C有线数字电视传输系统和DVB-S卫星数字电视传输系统。

2有线数字电视

2.1有线数字电视基本的构成

有线电视系统是采用缆线(电缆或光缆)等作为传输媒质来传送电视节目的一种闭路电视系统CCTV(Closed-circuit television)[用CCTV 称呼有线电视系统，容易与中国中央电视台的简称CCTV (China Central Television)，所以国内常常使用 CATV这个词(共用天线系统/有线电视Community Antenna Television)]，它以有线的方式在电视中心和用户终端之间传递声、像信息。所谓闭路，是指不向自由空间辐射，可供电视接收机通过无线接收方式直接接受的电磁波。

基本组成：接收信号源、 前端设备、干线传输系统（如干线放大器 (AGC)、 (ASC）和干线电缆或光缆) 、用户分配网络、用户终端（电视接收、调频广播 、线缆调制解调器 (Cable Modem，PC机、IP电话等) 等。如图2所示。

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图2有线数字电视基本的构成

2.2有线数字电视基本的标准

有线数字电视根据不同的指标主要分类如表1所示：

表1有线数字电视基本标准

DVB-C ATSC-64QAM ATSC-16VSB ISDB-C 调制方式 带 宽 传输速率 滚将悉数 纠错编码 压宿方式 16-64QAM 8MHz 31.64Mb/s 15% RS(204,188) 64QAM 6MHz 41.34Mb/s 15% RS(128,122) 16VSB 6MHz 43.05Mb/s 11.5% RS(207,187) 64QAM 6MHz 30.31Mb/s 18% RS(204,188) MPEG-2

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