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

Media Data Atom TypesSprite MediaTable 4-13Sprite propertiesProperty namekSpriteProperty-MatrixkSpriteProperty-VisiblekSpritePropertyLayerkSpriteProperty-GraphicsModekSpriteProperty-ActionHandlingSprite-IDkSpriteProperty-ImageIndexValue14568100DescriptionDescribes the sprite’s location and scaling within its spriteworld or sprite track. By modifying a sprite’s matrix, you canmodify the sprite’s location so that it appears to move in asmooth path on the screen or so that it jumps from one placeto another. You can modify a sprite’s size, so that it shrinks,grows, or stretches. Depending on which image compressoris used to create the sprite images, other transformations,such as rotation, may be supported as well. Translation-onlymatrices provide the best performance.Specifies whether or not the sprite is visible. To make a spritevisible, you set the sprite’s visible property to true.Contains a 16-bit integer value specifying the layer into whichthe sprite is to be drawn. Sprites with lower layer numbersappear in front of sprites with higher layer numbers. Todesignate a sprite as a background sprite, you should assignit the special layer number kBackgroundSpriteLayerNum.Specifies a graphics mode and blend color that indicates howto blend a sprite with any sprites behind it and with thebackground. To set a sprite’s graphics mode, you callSetSpriteProperty, passing a pointer to aModifierTrackGraphicsModeRecord structure.Specifies another sprite by ID that delegates QT events.Contains the atom ID of the sprite’s image atom.The override sample differs from the key frame sample in two ways. First, the override sample does not containa shared data atom. All shared data must appear in the key frame. Second, only those sprite properties thatchange need to be specified. If none of a sprite’s properties change in a given frame, then the sprite does notneed an atom in the differenced frame.The override sample can be used in one of two ways: combined, as with video key frames, to construct thecurrent frame; or the current frame can be derived by combining only the key frame and the current overridesample.2012-08-14 | © 2004, 2012 Apple Inc. All Rights Reserved.209