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

Media Data Atom TypesSprite Track Media FormatThe image container atom contains one atom of type kImageAtomType for each image in the key framesample. The image atom IDs are numbered from 1 to the number of images (numImages). Each image atomcontains a leaf atom that holds the image data (type kSpriteImageDataAtomType) and an optional leafatom (type kSpriteNameAtomType) that holds the name of the image.Figure 4-15Atoms that describe sprite imageskSpriteSharedDataAtomTypeID:1kSpriteImageContainerAtomTypeID:1kSpriteImageAtomTypeID:1kSpriteImageAtomTypeID:numImageskSpriteImageDataAtomTypeID:1Image datakSpriteNameAtomTypeID:1“The image name”kSpriteImageDataAtomTypeID:1Image dataSprite Media Format AtomsThe sprite track’s sample format enables you to store the atoms necessary to describe action lists that areexecuted in response to QuickTime events. “QT Atom Container Description Key” (page 221) defines a grammarfor constructing valid action sprite samples, which may include complex expressions.Both key frame samples and override samples support the sprite action atoms. Override samples overrideactions at the QuickTime event level. In effect, what you do by overriding is to completely replace one eventhandler and all its actions with another. The sprite track’s kSpriteTrackPropertySampleFormat propertyhas no effect on how actions are performed. The behavior is similar to the defaultkKeyFrameAndSingleOverride format where, if in a given override sample there is no handler for the event,the key frame’s handler is used, if there is one.Sprite Media Format ExtensionsThis section describes some of the atom types and IDs used to extend the sprite track’s media format, thusenabling action sprite capabilities.A complete description of the grammar for sprite media handler samples, including action sprite extensions,is included in the section “Sprite Media Handler Track Properties QT Atom Container Format” (page 222).2012-08-14 | © 2004, 2012 Apple Inc. All Rights Reserved.213