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

Movie AtomsMedia AtomsSound Media Information Header AtomsThe sound media information header atom stores the sound media’s control information, such as balance.Figure 2-27 (page 89) shows the layout of this atom.Figure 2-27The layout of a sound media information header atomSound media informationheader atomAtom sizeType = 'smhd'VersionFlagsBalanceReservedBytes441322The sound media information header atom contains the following data elements.SizeA 32-bit integer that specifies the number of bytes in this sound media information header atom.TypeA 32-bit integer that identifies the atom type; this field must be set to 'smhd'.VersionA 1-byte specification of the version of this sound media information header atom.FlagsA 3-byte space for sound media information flags. Set this field to 0.BalanceA 16-bit integer that specifies the sound balance of this sound media. Sound balance is the setting thatcontrols the mix of sound between the two speakers of a computer. This field is normally set to 0. See“Balance” (page 323) for more information about balance values.ReservedReserved for use by Apple. Set this field to 0.Base Media Information AtomsThe base media information atom (shown in Figure 2-28 (page 90)) stores the media information for mediatypes such as text, MPEG, time code, and music.2012-08-14 | © 2004, 2012 Apple Inc. All Rights Reserved.89