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

Movie AtomsSample AtomsFigure 2-45 (page 110) shows the layout of the sample-to-chunk atom.Figure 2-45The layout of a sample-to-chunk atomBytesSample-to-chunk atomAtom size4Type = 'stsc' 4VersionFlagsNumber of entriesSample-to-chunk table134VariableThe sample-to-chunk atom contains the following data elements.SizeA 32-bit integer that specifies the number of bytes in this sample-to-chunk atom.TypeA 32-bit integer that identifies the atom type; this field must be set to 'stsc'.VersionA 1-byte specification of the version of this sample-to-chunk atom.FlagsA 3-byte space for sample-to-chunk flags. Set this field to 0.Number of entriesA 32-bit integer containing the count of entries in the sample-to-chunk table.Sample-to-chunk tableA table that maps samples to chunks. Figure 2-46 (page 110) shows the structure of an entry in asample-to-chunk table. Each sample-to-chunk atom contains such a table, which identifies the chunk foreach sample in a media. Each entry in the table contains a first chunk field, a samples per chunk field,and a sample description ID field. From this information, you can ascertain where samples reside in themedia data.Figure 2-46The layout of a sample-to-chunk table entryFirst chunk Samples per chunk Sample description ID4 4 4FieldsBytes2012-08-14 | © 2004, 2012 Apple Inc. All Rights Reserved.110