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

Movie AtomsMedia AtomsHandler Reference AtomsThe handler reference atom specifies the media handler component that is to be used to interpret the media’sdata. The handler reference atom has an atom type value of 'hdlr'.Historically, the handler reference atom was also used for data references. However, this use is no longer currentand may now be safely ignored.The handler atom within a media atom declares the process by which the media data in the stream may bepresented, and thus, the nature of the media in a stream. For example, a video handler would handle a videotrack.Figure 2-23 (page 84) shows the layout of a handler reference atom.Figure 2-23The layout of a handler reference atomBytesHandler reference atomAtom sizeType = 'hdlr'VersionFlagsComponent typeComponent subtypeComponent manufacturerComponent flagsComponent flags maskComponent name441344444VariableHandler reference atoms contain the following data elements.SizeA 32-bit integer that specifies the number of bytes in this handler reference atom.TypeA 32-bit integer that identifies the atom type; this field must be set to 'hdlr'.VersionA 1-byte specification of the version of this handler information.FlagsA 3-byte space for handler information flags. Set this field to 0.2012-08-14 | © 2004, 2012 Apple Inc. All Rights Reserved.84