ISO/IEC 23002-3:2007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。深度贴图和视差贴图是第一种指定类型的辅助视频流，与立体视图视频内容有关。在这种情况下，ISO/IEC 23002-3:2007规定了用于传输描述辅助视频流解释的信息的语法和语义。 ISO/IEC 23002-3:2007将此类信息的语法规定为数据流，称为补充信息（SI）消息流。 还包括了可扩展性规定，以便在ISO/IEC对当前SI消息流语法的未来扩展中定义其他类型的数据。 SI消息流可以包含多个串联的SI消息，因此可以传输各种类型的信息。辅助视频SI（AVSI）是当前唯一定义的SI类型（ISO/IEC为未来规范保留的保留SI消息类型除外，如果存在，解码器将忽略这些类型）。AVSI消息描述了伴随主视频序列的辅助视频序列的解释。 例如，AVSI可以指示辅助视频代表深度映射信息，并且可以提供用于将辅助视频正确解释为这种深度信息的参数。识别这些消息所涉及的主视频流和辅助视频流的方法是一个系统级问题，不在ISO/IEC 23002-3:2007的范围内。 尽管辅助视频SI是ISO/IEC 23002-3:2007中当前规定的唯一SI类型，但SI消息格式已以通用方式定义，因此它可能用于辅助视频序列解释以外的目的。 任何类型的数据都可能以SI消息格式传输。

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.