The essential intention of conditional access system ( cas ) is to achieve pay - tv of the digital broadcast system by means of subscriber management and authorization control . so cas is the key technology to realize the pay - tv and interact - tv . based on composite technology in transport layer , paper describes the production and structure of transport stream in mpeg - 2 standard , mpeg - 2 program special information and conditional access definition in service information from dvb standard 有条件接收系统( conditionalaccesssystem , cas ) ,其基本目的是通过对用户的授权控制和管理,实现数字广播电视系统的有偿服务,在为运营商带来经济上回报的同时,也能为用户提供更多、更高质量的服务内容,它是实现付费电视、交互电视的关键技术。
Conditional access ( ca ) is a technology used to control access to digital television ( dtv ) services to authorized users by encrypting the transmitted programming . an emm provides general information about the subscriber and the status of the subscription . the emm is sent with the ecm 数字电视用户管理系统通过对用户订购信息的记录与处理，形成用户数据库，并经由与条件接收系统的接口，向条件接收系统发送用户授权管理信息的基本数据，条件接收系统据此实现对用户收看数字电视节目的控制。
This research realized the track monitor system of ca glue , could suitably match all different conditions receiving system , the realization of this module used the interior of examination system to define the track , again add to the transplant condition receiving system , this avoided the problem on difficulty of tracking due to dissimilar parameter name or the mode of working of conditional accessing system 研究实现了适配层的跟踪监测系统,能适配不同的条件接收系统。这个模块的实现是在检测系统中内部定义跟踪函数,然后在移植的条件接收系统中调用这些跟踪函数,这样就避免了在跟踪检测过程中条件接收系统因为工作方法或参数名称类型不同而带来的差异。
