ISO/IEC 23002-3:20 07将辅助视频流定义为编码为视频序列并补充主视频序列的数据。深度图和视差图是与立体视图视频内容相关的第一指定类型的辅助视频流。在此上下文中，ISO/IEC 23002-3:20 07规定了用于传达描述辅助视频流的解释的信息的语法和语义。用于这种信息的语法在ISO/IEC 23002-3:20 07中规定为被称为补充信息(SI)消息流的数据流。已经包括了可扩展性的规定，使得可以在ISO/IEC对当前SI消息流语法的未来扩展中定义附加类型的数据。SI消息流可以包含多个级联的SI消息，因此传送各种类型的信息。辅助视频SI(AVSI)是唯一当前定义的SI类型(除了保留的SI消息类型之外，保留的SI消息类型是由ISO/IEC为将来的规范保留的并且如果存在的话将被解码器忽略)。AVSI消息表征伴随主视频序列的辅助视频序列的解释。例如，AVSI可以指示辅助视频表示深度图信息，并且可以提供用于将辅助视频正确解释为这样的深度信息的参数。用于识别这些消息所属的主视频流和辅助视频流的装置是超出ISO/IEC 23002-3:20 07范围的系统级问题。虽然辅助视频SI是目前ISO/IEC 23002中唯一规定的SI类型-参考3:20 07，SI消息格式已经以通用方式定义，使得它可以潜在地用于除了帮助解释辅助视频序列之外的目的。任何类型的数据都可能以SI消息格式携带。

ISO/IEC 23002-3:2007 defines auxiliary video streams as data coded as video sequences and supplementing a primary video sequence. Depth maps and parallax maps are the first specified types of auxiliary video streams, relating to stereoscopic-view video content. In this context, ISO/IEC 23002-3:2007 specifies syntax and semantics for conveying information describing the interpretation of auxiliary video streams.

Syntax for such information is specified in ISO/IEC 23002-3:2007 as a stream of data referred to as a supplemental information (SI) message stream. Provisions for extensibility have been included, so that additional types of data can be defined in future extensions of the current SI message stream syntax by ISO/IEC.

An SI message stream can contain several concatenated SI messages, hence conveying various types of information. The auxiliary video SI (AVSI) is the only currently-defined type of SI (other than reserved SI message types that are reserved for future specification by ISO/IEC and are to be ignored by decoders if present). An AVSI message characterizes the interpretation of an auxiliary video sequence that accompanies a primary video sequence. For instance, an AVSI can indicate that the auxiliary video represents depth map information, and can provide parameters for the proper interpretation of the auxiliary video as such depth information. The means for identifying the primary video stream and the auxiliary video stream to which these messages pertain is a system-level issue that is outside the scope of ISO/IEC 23002-3:2007.

Although the auxiliary video SI is the only type of SI that is currently specified in ISO/IEC 23002-3:2007, the SI message format has been defined in a generic fashion so that it can potentially be used for purposes other than aiding in the interpretation of auxiliary video sequences. Any kind of data could potentially be carried in the SI message format.