Programming With QuickTime VR

Track Reference Entry Structure

Since there are no fields in the sample track atom to indicate the presence of low-resolution image tracks, a separate sibling atom must be added to the panorama sample atom container. The track reference array atom contains an array of track reference entry structures that specify information about any low-resolution image tracks contained in a movie. Its atom type is kQTVRTrackRefArrayAtomType ('tref' ).

A track reference entry structure is defined by the VRTrackRefEntry data type:



 
typedef struct VRTrackRefEntry {

    UInt32                              trackRefType;

    UInt16                              trackResolution;

    UInt32                              trackRefIndex;

} VRTrackRefEntry;

trackRefType: The track reference type. See "Track References" for a description of the available track reference types.
trackResolution: The track resolution. See "Resolutions" in Chapter 2, "QuickTime VR Manager," for a description of the values that can occur in this field.
trackRefIndex: The index of the track reference.

The number of entries in the track reference array atom is determined by dividing the size of the atom by sizeof (VRTrackRefEntry ).

kQTVRPreviewTrackRes is a special value for the trackResolution field in the VRTrackRefEntry structure. This is used to indicate the presence of a special preview image track. Preview image tracks are discussed in "Optimizing QuickTime VR Movies for Web Playback" .