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

Movie AtomsSample AtomsThe sample table atom has an atom type of 'stbl'. It can contain the sample description atom, thetime-to-sample atom, the sync sample atom, the sample-to-chunk atom, the sample size atom, the chunkoffset atom, and the shadow sync atom. Recent additions to the list of atom types that a sample table atomcan contain are the optional sample group description and sample-to-group atoms included in Appendix G:“Audio Priming - Handling Encoder Delay in AAC” (page 421).The sample table atom contains all the time and data indexing of the media samples in a track. Using tables,it is possible to locate samples in time, determine their type, and determine their size, container, and offsetinto that container.If the track that contains the sample table atom references no data, then the sample table atom does not needto contain any child atoms (not a very useful media track).If the track that the sample table atom is contained in does reference data, then the following child atoms arerequired: sample description, sample size, sample to chunk, and chunk offset. All of the subtables of the sampletable use the same total sample count.The sample description atom must contain at least one entry. A sample description atom is required becauseit contains the data reference index field that indicates which data reference atom to use to retrieve the mediasamples. Without the sample description, it is not possible to determine where the media samples are stored.The sync sample atom is optional. If the sync sample atom is not present, all samples are implicitly sync samples.2012-08-14 | © 2004, 2012 Apple Inc. All Rights Reserved.97