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

Movie AtomsSample AtomsSamples are stored in a series of chunks in a media. Chunks are a collection of data samples in a media thatallow optimized data access. A chunk may contain one or more samples. Chunks in a media may have differentsizes, and the individual samples within a chunk may have different sizes from one another, as shown in Figure2-32 (page 96).Figure 2-32Samples in a mediaData streamSample 1Chunk 1Sample 2Sample 3Sample 4Chunk 2Sample 5Sample 6Chunk 3Sample 7Chunk 4Sample 8Chunk 5Sample 9One way to describe a sample is to use a sample table atom. The sample table atom acts as a storehouse ofinformation about the samples and contains a number of different types of atoms. The various atoms containinformation that allows the media handler to parse the samples in the proper order. This approach enforcesan ordering of the samples without requiring that the sample data be stored sequentially with respect to movietime in the actual data stream.The next section discusses the sample table atom. Subsequent sections discuss each of the atoms that mayreside in a sample table atom.Sample Table AtomsThe sample table atom contains information for converting from media time to sample number to samplelocation. This atom also indicates how to interpret the sample (for example, whether to decompress the videodata and, if so, how). This section describes the format and content of the sample table atom.2012-08-14 | © 2004, 2012 Apple Inc. All Rights Reserved.96