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# Track reference atom ('tref')

An atom that defines relationships between tracks.

## Topics

### Data fields

[`Size`](/documentation/quicktime-file-format/Track_reference_atom/Size)

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

[`Type`](/documentation/quicktime-file-format/Track_reference_atom/Type)

A 32-bit integer that identifies the atom type.

[`Track reference type atom`](/documentation/quicktime-file-format/Track_reference_atom/Track_reference_type_atom)

A list of track reference type atoms containing the track reference information.


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