Quicktime File Format (2012-08-14).pdf

Media Data Atom TypesTrack References for Object TracksTrack References for Object TracksNote VR Media is deprecated in the QuickTime file format. The information that follows is intendedto document existing content containing VR Media and should not be used for new development.The track references to an object’s image and hot spot tracks are not handled the same way as track referencesto panoramas. The track reference types are the same (kQTVRImageTrackRefType andkQTVRHotSpotTrackRefAtomType), but the location of the reference indexes is different. There is no entryin the object sample atom for the track reference indexes. Instead, separate atoms using the VRTrackRefEntrystructure are stored as siblings to the object sample atom. The types of these atoms arekQTVRImageTrackRefAtomType and kQTVRHotSpotTrackRefAtomType. If either of these atoms is notpresent, then the reference index to the corresponding track is assumed to be 1.Note The trackResolution field in the VRTrackRefEntry structure is ignored for object tracks.The actual views of an object for an object node are contained in an object image track, which is usually astandard QuickTime video track. (An object image track can also be any type of track that is capable of displayingan image, such as a QuickTime 3D track.)As described in Chapter 1 of QuickTime VR , these views are often captured by moving a camera around theobject in a defined pattern of pan and tilt angles. The views must then be ordered into an object image array,which is stored as a one-dimensional sequence of frames in the movie’s video track (see Figure 4-29 (page309)).Figure 4-29The structure of an image track for an object1,1 1,2 1,3 1,4 ...... 1,m 2,1 2,2 2,3 ..... ..... n,1 n,2 ..... n,mView durationFor object movies containing frame animation, each animated view in the object image array consists of theanimating frames. It is not necessary that each view in the object image array contain the same number offrames, but the view duration of all views in the object movie must be the same.2012-08-14 | © 2004, 2012 Apple Inc. All Rights Reserved.309