Track Load Settings Atoms

QuickTime Movie File Format Specification, May 1996

Track Load Settings Atoms

Track load settings atoms contain information that indicates how the track is to be used in its movie. Applications that read QuickTime files can use this information to process the movie data more efficiently. Track load settings atoms are optional and have an atom type value of 'load' .

Figure 15 The layout of a track load settings atom

Track load settings atoms contain the following data elements.

Size: A 32-bit integer that specifies the number of bytes in this track load settings atom.
Type: A 32-bit integer that identifies the atom type; this field must be set to 'load' .
Preload start time: A 32-bit integer specifying the starting time, in the movie's time coordinate system, of a segment of the track that is to be preloaded. Used in conjunction with the Preload duration value.
Preload duration: A 32-bit integer specifying the duration, in the movie's time coordinate system, of a segment of the track that is to be preloaded. If the duration is set to -1, it means that the preload segment extends from the preload start time to the end of the track. All media data in the segment of the track defined by the preload start time and preload duration values should be loaded into memory when the movie is to be played.
Preload flags: A 32-bit integer containing flags governing the preload operation. Only two flags are defined and they are mutually exclusive. If Preload flags is set to 1, the track is to be preloaded regardless of whether it is enabled. If Preload flags is set to 2, the track is only preloaded if it is enabled.
Default hints: A 32-bit integer containing playback hints. More than one flag may be enabled. Flags are enabled by setting them to 1. The following flags are defined.