---

QuickTime Movie File Format Specification, May 1996

| Previous | Chapter contents | Chapter top | Next |

Handler Reference Atoms

The handler reference atom specifies the media handler component that is to be used to interpret the media's data. The handler reference atom has an atom type value of 'hdlr' .

Historically, the handler reference atom was also used for data references. However, this use may now be ignored.

Figure 0-20 shows the layout of a handler reference atom.

Figure 20 The layout of a handler reference atom

Handler reference atoms contain the following data elements.

Size

A 32-bit integer that specifies the number of bytes in this handler reference atom.

Type

A 32-bit integer that identifies the atom type; this field must be set to 'hdlr' .

Version

A 1-byte specification of the version of this handler information.

Flags

A 3-byte space for handler information flags. Set this field to 0.

Component type

A four-character code that identifies the type of the handler. Only two values are valid for this field: 'mhlr' for media handlers and 'dhlr' for data references.

Component subtype

A four-character code that identifies the type of the media handler or data handler. For media handlers, this field defines the type of data, for example, 'vide' for video data or 'soun' for sound data .

For data handlers, this field defines the data reference type. For example, a Component subtype value of 'alis' identifies a file alias.

Component manufacturer

Reserved. Set to 0.

Component flags

Reserved. Set to 0.

Component flags mask

Reserved. Set to 0.

Component name

A Pascal string that specifies the name of the component--that is, the media handler used when this movie was created. This field may contain a zero-length (empty) string.

| Previous | Chapter contents | Chapter top | Next |