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

Media Data Atom TypesSprite Track Media FormatFigure 4-13 (page 212) shows the high-level structure of a sprite track key frame sample. Each atom in the atomcontainer is represented by its atom type, atom ID, and, if it is a leaf atom, the type of its data.Figure 4-13A key frame sample atom containerQT atomcontainerkSpriteAtomTypeID:1kSpriteAtomTypeID:numSpriteskSpriteSharedDataAtomTypeID:1Sprite property atomsShared data atomsThe QT atom container contains one child atom for each sprite in the key frame sample. Each sprite atom hasa type of kSpriteAtomType. The sprite IDs are numbered from 1 to the number of sprites defined by the keyframe sample (numSprites).Each sprite atom contains leaf atoms that define the properties of the sprite, as shown in Figure 4-14 (page212). For example, the kSpritePropertyLayer property defines a sprite’s layer. Each sprite property atomhas an atom type that corresponds to the property and an ID of 1.Figure 4-14Atoms that describe a sprite and its propertieskSpriteAtomTypeID:1kSpritePropertyImageIndexID:1shortkSpritePropertyLayerID:1shortkSpritePropertyGraphicsModeID:1ModifierTrackGraphicsModeRecordkSpritePropertyMatrixkSpritePropertyVisiblekSpriteNameAtomTypekSpriteURLLinkAtomTypeID:1ID:1ID:1ID:1MatrixRecordshort“The sprite name”“The URL”In addition to the sprite atoms, the QT atom container contains one atom of typekSpriteSharedDataAtomType with an ID of 1. The atoms contained by the shared data atom describe datathat is shared by all sprites. The shared data atom contains one atom of typekSpriteImagesContainerAtomType with an ID of 1 (Figure 4-15 (page 213)).2012-08-14 | © 2004, 2012 Apple Inc. All Rights Reserved.212