Track Atoms

QuickTime Movie File Format Specification, May 1996

Track Atoms

Track atoms define a single track of a movie. A movie may consist of one or more tracks. Each track is independent of the other tracks in the movie and carries its own temporal and spatial information. Each track atom contains its associated media atom.

Figure 0-9 shows the layout of a track atom. Track atoms have an atom type value of 'trak' . The track atom requires the track header atom ('tkhd' ) and the media atom ('mdia' ). Other child atoms are optional and may include a track clipping atom ('clip' ), a track matte atom ('matt' ), an edit atom ('edts' ), a track reference atom ('tref' ), a track input map atom ('imap' ), and a user data atom ('udta' ).

Figure 9 The layout of a track atom

Track atoms contain the following data elements.

Size: A 32-bit integer that specifies the number of bytes in this track atom.
Type: A 32-bit integer that identifies the atom type; this field must be set to 'trak' .
Track header: The track header atom associated with this track. See the next section for details.
Track clipping: The track clipping atom associated with this track. See "Clipping Atoms," beginning on [link] , for more information.
Track matte: The track matte atom associated with this track. See "Track Matte Atoms," beginning on [link] , for more information.
Edits: The edit atom associated with this track. See "Edit Atoms," beginning on [link] , for details.
Track references: The track reference atom associated with this track. See "Track Reference Atoms," beginning on [link] , for details.
Track load settings: The track load settings atom associated with this track. See "Track Load Settings Atoms," beginning on [link] , for details.
Track input map: The track input map atom associated with this track. See "Track Input Map Atoms," beginning on [link] , for details.
Media: The media atom associated with this track. See "Media Atoms," beginning on [link] , for details.
User data: The user data atom associated with this track. See "User Data Atoms" for more information.

Track Atoms

Track Header Atoms

Clipping Atoms

Clipping Region Atoms

Track Matte Atoms

Compressed Matte Atoms

Edit Atoms

Edit List Atoms

Track Load Settings Atoms

Track Reference Atoms

Track Input Map Atoms