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

Movie AtomsMedia AtomsMedia types that are derived from the base media handler may add other atoms within the base mediainformation atom, as appropriate. At present, the only media type that defines additional atoms is timecodemedia. See “Timecode Media” (page 189) for more information about this media types.Figure 2-28The layout of a base media information atomBase media information atomAtom sizeType = 'minf'Base media information header atom'gmhd'‡‡ Required atomThe base media information atom contains the following data elements.SizeA 32-bit integer that specifies the number of bytes in this base media information atom.TypeA 32-bit integer that identifies the atom type; this field must be set to 'minf'.Base media information header atomSee “Base Media Information Header Atoms” (page 90).Base Media Information Header AtomsThe base media information header atom indicates that this media information atom pertains to a base media.Figure 2-29 (page 90) shows the layout of this atom.Figure 2-29The layout of a base media information header atomBase media information header atomAtom sizeType = 'gmhd'Base media information atom'gmin'‡Text media information atom'text'‡ Required atom2012-08-14 | © 2004, 2012 Apple Inc. All Rights Reserved.90