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

Movie AtomsMedia AtomsVideo Media Information Header AtomsVideo media information header atoms define specific color and graphics mode information.Figure 2-25 (page 87) shows the structure of a video media information header atom.Figure 2-25The layout of a media information header atom for videoBytesVideo media information header atomAtom sizeType = 'vmhd'VersionFlagsGraphics modeOpcolor441326The video media information header atom contains the following data elements.SizeA 32-bit integer that specifies the number of bytes in this video media information header atom.TypeA 32-bit integer that identifies the atom type; this field must be set to 'vmhd'.VersionA 1-byte specification of the version of this video media information header atom.FlagsA 3-byte space for video media information flags. There is one defined flag.No lean aheadThis is a compatibility flag that allows QuickTime to distinguish between movies created withQuickTime 1.0 and newer movies. You should always set this flag to 1, unless you are creating amovie intended for playback using version 1.0 of QuickTime. This flag’s value is 0x0001.Graphics modeA 16-bit integer that specifies the transfer mode. The transfer mode specifies which Boolean operationQuickDraw should perform when drawing or transferring an image from one location to another. See“Graphics Modes” (page 321) for a list of graphics modes supported by QuickTime.2012-08-14 | © 2004, 2012 Apple Inc. All Rights Reserved.87