Data Reference Atoms

QuickTime Movie File Format Specification, May 1996

Data Reference Atoms

Data reference atoms contain tabular data that instructs the data handler component how to access the media's data. Figure 0-27 shows the data reference atom.

The data reference atom contains the following data elements.

Size: A 32-bit integer that specifies the number of bytes in this data reference atom.
Type: A 32-bit integer that identifies the atom type; this field must be set to ' dref' .
Version: A 1-byte specification of the version of this data reference atom.
Flags: A 3-byte space for data reference flags. Set this field to 0.
Number of entries: A 32-bit integer containing the count of data references that follow.
Data references: An array of data references.

Each data reference is formatted like an atom and contains the following data elements.

Size: A 32-bit integer that specifies the number of bytes in these data references.
Type: A 32-bit integer that specifies the type of the data in the data references. Table 0-4 lists valid Type values.
Version: A 1-byte specification of the version of these data references.
Flags: A 3-byte space for data reference flags. There is one defined flag.
Data references: The data reference information.

Table 0-4 shows the currently defined data reference types that may be stored in a movie.

Table 4 Data reference types
Data reference type	Description
`'alis'`	Data reference is a Macintosh alias. An alias contains information about the file, including its full path name. For more information, see Inside Macintosh: Files.
`'rsrc'`	Data reference is a Macintosh alias. Appended to the end of the alias is the resource type (stored as a 32-bit unsigned integer) and ID (stored as a 16-bit signed integer) to use within the specified file.