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

Media Data Atom TypesSound MediaTypeAn unsigned 32-bit integer set to zero (0x00000000). This is a rare instance in which the type field is nota four-character ASCII code.MPEG-4 Elementary Stream Descriptor Atom ('esds')This atom is a required extension to the sound sample description for MPEG-4 audio. This atom contains anelementary stream descriptor, which is defined in ISO/IEC FDIS 14496.SizeAn unsigned 32-bit integer holding the size of the elementary stream descriptor atom.TypeAn unsigned 32-bit field containing the four-character code 'esds'.VersionAn unsigned 32-bit field set to zero.Elementary Stream DescriptorAn elementary stream descriptor for MPEG-4 audio, as defined in the MPEG-4 specification ISO/IEC 14496.Audio Channel Layout Atom (‘chan’)This atom is an optional extension to the sound sample description specifying audio channel layouts for soundmedia contained in QuickTime movies. It is a full atom followed by a big-endian audio channel layout structureas defined by Apple’s Core Audio framework. Audio channel layouts can be applied to both compressed anduncompressed sound formats.Note Audio channel layouts with more than two channels per track require implementation witha version 2 sound sample description.SizeAn unsigned 32-bit integer holding the size of the audio channel layout atom.TypeAn unsigned 32-bit field containing the four-character code 'chan'VersionA 1-byte specification of the version of the audio channel layout atom.FlagsA 3-byte space for audio channel layout flags.2012-08-14 | © 2004, 2012 Apple Inc. All Rights Reserved.186