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

Movie AtomsTrack AtomsDefault hintsA 32-bit integer containing playback hints. More than one flag may be enabled. Flags are enabled bysetting them to 1. The following flags are defined.Double bufferThis flag indicates that the track should be played using double-buffered I/O. This flag’s value is0x0020.High qualityThis flag indicates that the track should be displayed at highest possible quality, without regardto real-time performance considerations. This flag’s value is 0x0100.Track Reference AtomsTrack reference atoms define relationships between tracks. Track reference atoms allow one track to specifyhow it is related to other tracks. For example, if a movie has three video tracks and three sound tracks, trackreferences allow you to identify the related sound and video tracks. Track reference atoms have an atom typevalue of 'tref'.Track references are unidirectional and point from the recipient track to the source track. For example, a videotrack may reference a time code track to indicate where its time code is stored, but the time code track wouldnot reference the video track. The time code track is the source of time information for the video track.A single track may reference multiple tracks. For example, a video track could reference a sound track to indicatethat the two are synchronized and a time code track to indicate where its time code is stored.A single track may also be referenced by multiple tracks. For example, both a sound and video track couldreference the same time code track if they share the same timing information.If this atom is not present, the track is not referencing any other track in any way. Note that the array of trackreference type atoms is sized to fill the track reference atom. Track references with a reference index of 0 arepermitted. This indicates no reference.For more information about Track References, see “Track References” (page 248).2012-08-14 | © 2004, 2012 Apple Inc. All Rights Reserved.73