Quicktime File Format (2012-08-14).pdf

Movie AtomsOverview of Movie AtomsFigure 2-5 (page 48) shows the layout of a user data atom.Figure 2-5The layout of a user data atomBytesUser data atomAtom sizeType = 'udta'44User data list‡Atom sizeType = user data types44User data list‡ Required atomThe user data atom contains the following data elements.SizeA 32-bit integer that specifies the number of bytes in this user data atom.TypeA 32-bit integer that identifies the atom type; this field must be set to 'udta'.User data listA user data list that is formatted as a series of atoms. Each data element in the user data list contains sizeand type information along with its payload data. For historical reasons, the data list is optionallyterminated by a 32-bit integer set to 0. If you are writing a program to read user data atoms, you shouldallow for the terminating 0. However, if you are writing a program to create user data atoms, you cansafely leave out the terminating 0.Table 2-1 (page 48) lists the currently defined list entry types.Table 2-1User data list entry typesList entry type'©arg''©ark''©cok'DescriptionName of arrangerKeywords for arrangerKeywords for composerForSortingXX2012-08-14 | © 2004, 2012 Apple Inc. All Rights Reserved.48