MPEG-4 XMT Format

XMT Format

XMT is the official textural description of MPEG-4 scenes. It is part of ISO/IEC 14496-11, and is quite similar to the X3D XML language. For more details on the XMT syntax, please have a look at the tutorial.

Importing media with MP4Box and XMT

There is no standard element in XMT-A allowing to describe multiplexing parameters for MP4. In order to do this MP4Box uses an XML representation of MuxInfo in the StreamSource sub elements (encoding hints) called MP4MuxHints.

The complete syntax is:

<StreamSource url=”filename” >
<MP4MuxHints GroupID=”…” startTime=”…” duration=”…” useDataReference=”…” noFrameDrop=”…” SBR_Type=”…” frameRate=”…” compactSize=”…” textNode=”…” fontNode=”…” />
</StreamSource>

The streamFormat parameter is not represented in XMT-A.

Note When decompressing an mp4 file to bt (XMT-A), a MuxInfo (MP4MuxHints) is automatically generated for all streams other than BIFS and OD in order to keep track of media location in the original MP4. You can then simply modify and reencode the BT or XMT file without specifying the media data location.