This part of ISO/IEC 23002 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, this part of ISO/IEC 23002 specifies syntax and semantics for conveying information describing the interpretation of auxiliary video streams. Syntax for such information is specified herein 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.