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

Glossarytrack A Movie Toolbox data structure thatrepresents a single data stream in a QuickTimemovie. A movie may contain one or more tracks.Each track is independent of other tracks in themovie and represents its own data stream. Each trackhas a corresponding media, which describes the datafor the track.track boundary region A region that describes thearea occupied by a track in the track’s coordinatesystem. QuickTime obtains this region by applyingthe track clipping region and the track matte to thevisual image contained in the track rectangle.track clipping region The clipping region of a trackin the track’s coordinate system. QuickTime appliesthe track’s clipping region and the track matte tothe image contained in the track rectangle to obtainthe track boundary region. Only that portion of thetrack that lies in the track boundary region is thentransformed into an image in the movie coordinatesystem.track header atom A QT atom that specifies thecharacteristics of a track in a QuickTime movie.track height The height, in pixels, of the trackrectangle.track input map A structure of QT atoms thatspecifies how secondary data for a track is to beinterpreted (clipping, blending, etc.).track load settings Information that specifies howand when a track is to be preloaded before runningin a movie.track matte A pixel map that defines the blendingof track visual data. The value of each pixel in thepixel map governs the relative intensity of the trackdata for the corresponding pixel in the result image.QuickTime applies the track matte, along with thetrack clipping region, to the image contained in thetrack rectangle to obtain the track boundary region.See track matte, track rectangle, and track boundaryregion.track movie boundary region A region thatdescribes the area occupied by a track in the moviecoordinate system, before the movie has beenclipped by the movie clipping region. The movieboundary region is built up from the track movieboundary regions for each of the movie’s tracks.track offset The blank space that represents theintervening time between the beginning of a movieand the beginning of a track’s data. In an audio track,the blank space translates to silence; in a video track,the blank space generates no visual image. All of thetracks in a movie use the movie’s time coordinatesystem. That is, the movie’s time scale defines thebasic time unit for each of the movie’s tracks. Eachtrack begins at the beginning of the movie, but thetrack’s data might not begin until some time valueother than 0.track reference A data structure that defines therelation between movie tracks, such as the relationbetween a timecode track and other tracks. Seetimecode track.track rectangle A rectangle that completelyencloses the visual representation of a track in aQuickTime movie. The width of this rectangle inpixels is referred to as the track width; the height,as the track height.track width The width, in pixels, of the trackrectangle.transformation matrix A 3-by-3 matrix that defineshow to map points from one coordinate space intoanother coordinate space.tween data The data in a tween track, such asinterpolation values.2012-08-14 | © 2004, 2012 Apple Inc. All Rights Reserved.444