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

Media Data Atom TypesSound MediaSound MediaSound media is used to store compressed and uncompressed audio data in QuickTime movies. It has a mediatype of 'soun'. This section describes the sound sample description and the storage format of sound files usingvarious data formats.Sound Sample DescriptionsThe sound sample description contains information that defines how to interpret sound media data. Thissample description is based on the standard sample description, as described in “Sample DescriptionAtoms” (page 99).The data format field contains the format of the audio data. This may specify a compression format or one ofseveral uncompressed audio formats. Table 4-7 (page 176) shows a list of some supported sound formats.Table 4-7Partial list of supported QuickTime audio formats.FormatNot specifiedkSoundNotCompressedk8BitOffsetBinary-Formatk16BitBigEndianFormatk16BitLittleEndian-Format4-Charactercode0x00000000'NONE''raw ''twos''sowt'DescriptionThis format descriptor should not be used, butmay be found in some files. Samples are assumedto be stored in either 'raw ' or 'twos' format,depending on the sample size field in the sounddescription.This format descriptor should not be used, butmay be found in some files. Samples are assumedto be stored in either 'raw ' or 'twos' format,depending on the sample size field in the sounddescription.Samples are stored uncompressed, inoffset-binary format (values range from 0 to 255;128 is silence). These are stored as 8-bit offsetbinaries.Samples are stored uncompressed, intwo’s-complement format (sample values rangefrom -128 to 127 for 8-bit audio, and -32768 to32767 for 1- bit audio; 0 is always silence). Thesesamples are stored in 16-bit big-endian format.16-bit little-endian, twos-complement2012-08-14 | © 2004, 2012 Apple Inc. All Rights Reserved.176