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

Movie AtomsTrack AtomsFigure 2-17 (page 72) shows the layout of this atom.Figure 2-17The layout of a track load settings atomBytesTrack load settings atomAtom sizeType = 'load'Preload start timePreload durationPreload flagsDefault hints444444Track load settings atoms contain the following data elements.SizeA 32-bit integer that specifies the number of bytes in this track load settings atom.TypeA 32-bit integer that identifies the atom type; this field must be set to 'load'.Preload start timeA 32-bit integer specifying the starting time, in the movie’s time coordinate system, of a segment of thetrack that is to be preloaded. Used in conjunction with the preload duration.Preload durationA 32-bit integer specifying the duration, in the movie’s time coordinate system, of a segment of the trackthat is to be preloaded. If the duration is set to –1, it means that the preload segment extends from thepreload start time to the end of the track. All media data in the segment of the track defined by thepreload start time and preload duration values should be loaded into memory when the movie is to beplayed.Preload flagsA 32-bit integer containing flags governing the preload operation. Only two flags are defined, and theyare mutually exclusive. If this flag is set to 1, the track is to be preloaded regardless of whether it is enabled.If this flag is set to 2, the track is to be preloaded only if it is enabled.2012-08-14 | © 2004, 2012 Apple Inc. All Rights Reserved.72