Preview Atoms

QuickTime Movie File Format Specification, May 1996

Preview Atoms

The preview atom contains information that allows you to find the preview image associated with a QuickTime movie. The preview image, or poster, is a representative image suitable for display to the user in, say, file-open dialogs. Figure 0-4 depicts the layout of a preview atom.

Figure 4 The layout of a preview atom

The preview atom has an atom type value of 'pnot' and, following its atom header, contains the following fields.

Size: A 32-bit integer that specifies the number of bytes in this preview atom.
Type: A 32-bit integer that identifies the atom type; this field must be set to 'pnot'.
Modification date: A 32-bit unsigned integer containing a date that indicates when the preview was last updated. The date is in standard Macintosh format.
Version number: A 16-bit integer that must be set to 0.
Atom type: A 32-bit integer that indicates the type of atom that contains the preview data. Typically, this is set to 'PICT' to indicate a QuickDraw picture.
Atom index: A 16-bit integer that identifies which atom of the specified type is to be used as the preview. Typically, this field is set to 1 to indicate that you should use the first atom of the type specified in the Atom type field.