BS EN 50221-1997 条件存取和其它数字视频广播译码器用通用接口规范

标准号：BS EN 50221-1997
中文标准名称：条件存取和其它数字视频广播译码器用通用接口规范
英文标准名称：Common interface specification for conditional access and other digital video broadcasting decoder applications
标准类型：L70
发布日期：1997/8/15 12:00:00
实施日期：1997/8/15 12:00:00
中国标准分类号：L70
国际标准分类号：33.170
适用范围：A set of standards has been designed to be used in digital video broadcasting. These standards include source coding, channel coding, service information and decoder interfaces. In addition, a conditional access system is used when there is a need to control access to a broadcast service. It has been decided that the conditional access system need not be standardised, although a common scrambling algorithm is provided. It remains for broadcasters to access decoders with different conditional access systems and to ensure that they have choice of supply of such systems. A solution is to use the common scrambling algorithm and to execute solutions for access based on commercial agreements between operators. This solution can operate with single CA systems embedded in decoders. A second solution is based on a standardised interface between a module and a host where CA and more gen-erally defined proprietary functions may be implemented in the module. This solution also allows broadcasters to use modules containing solutions from different suppliers in the same broadcast system, thus increasing their choice and anti-piracy options. The scope of this document is to describe this common interface. The decoder, referred to in this specification as the host, includes those functions that are necessary to receive MPEG-2 video, audio and data in the clear. This specification defines the interlace between the host and the scrambling and CA applications, which will operate on an external module. Two logical interfaces, to be included on the same physical interface, are defined The first interface is the MPEG-2 Transport Stream. The link and physical layers are defined in this specification and the higher layers are defined in the MPEG-2 specifications. The second interface, the command interface, carries commands between the host and the module. Six layers are defined for this interface. An example of a single module in connection with a host is shown in figure 1. This specification only defines those aspects of the host that are required to completely specify the interactions across the interface. The specification assumes nothing about the host design except to define a set of services which are required of the host in order to allow the module to operate. The specification does not define the operation or functionality of a conditional access system application on the module. The applications which may be performed by a module communicating across the interface are not limited to conditional access or to those described in this specification. More than one module may be sup-ported concurrently.