The XMT (Extensible MPEG-4 Textual) format is the use of a textual syntax to represent MPEG-4 3-D scene descriptions. XMT was designed to provide content authors the ability to exchange their content with other authors while preserving their intentions in the text format. XMT provides interoperability between MPEG-4, Extensible 3D (X3D), and Synchronized Multimedia Integration Language (SMIL). X3D is a standard developed by the Web3D Consortium to replace Virtual Reality Modeling Language (VRML). The XMT format can be interchanged between SMIL, VRML, and MPEG-4 players.
XMT consists of two levels: XMT-A format and XMT-? format. XMT-A is based on an Extensible Markup Language (XML) version of MPEG-4 content and contains a subset of X3D. XMT-?is based on SMIL. XMT-?provides authors with an escape mechanism from ?to A.