本标准提供了数字电影（D-Cinema）系统安全通信中用于单向通信信道的通用额外影院信息（ETM）格式规范。为了满足不同的应用程序安全性要求，XML包装器可以扩展为不同的应用程序安全级别。（例如，密钥传递消息（KDM）就是这种格式的一个特定实例。）ETM使用W3C可扩展标记语言（见[XML]）来表示信息负载。它使用XML加密和签名原语提供安全性。

This standard presents a specification for a generic Extra-Theatre Message (ETM) format for use with unidirectional communications channels used in security communcations for Digital Cinema (D-Cinema) systems.The ETM specification is a generic XML security wrapper that includes specific fields which can be extended to carry different kinds of information to meet various application-level requirements. (For example, the Key Delivery Message (KDM) is a specific instance of this format.) The ETM uses W3C Extensible Markup Language (see [XML]) to represent the information payload. It provides security using the XML encryption and signature primitives.