QT atom container description key

Overview

Because QT atom container–based data structures are widely used in QuickTime, a description key is presented here. Its usage is illustrated in the following sections, Sprite media handler track properties QT atom container format and Sprite media handler sample QT atom container formats.

[(QTAtomFormatName)] =
atomType_1, id, index
    data
atomType_n, id, index
    data

The atoms may be required or optional:

 // optional atom
 // required atom
<atomType>
atomType

The atom ID may be a number if it is required to be a constant, or it may be a list of valid atom IDs, indicating that multiple atoms of this type are allowed.

3               // one atom with id of 3
(1..3)          // three atoms with id's of 1, 2, and 3
(1, 5, 7)       // three atoms with id's of 1, 5, and 7
(anyUniqueIDs)  // multiple atoms each with a unique id

The atom index may be a 1 if only one atom of this type is allowed, or it may be a range from 1 to some constant or variable.

1               // one atom of this type is allowed, index is always  1
(1..3)          // three atoms with indexes 1, 2, and 3
(1..numAtoms)   // numAtoms atoms with indexes of 1 to numAtoms

The data may be leaf data in which its data type is listed inside of brackets [], or it may be a nested tree of atoms.

[theDataType]   // leaf data of type theDataType
childAtoms      // a nested tree of atoms

Nested QTAtom format definitions [(AtomFormatName)] may appear in a definition.

See Also

Media data atom types

• Sprite media
• Sprite track properties
• Sprite track media format
• Sprite media atom and data types
• Sprite button behaviors
• Sprite media handler track properties QT atom container format
• Sprite media handler sample QT atom container formats
• Wired action grammar
• Tween media
• 3D media
• VR media
• Node parent atom
• Node location atom structure ('nloc')
• Custom cursor atom
• Node information atom container