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

Movie AtomsOverview of Movie AtomsOverview of Movie AtomsQuickTime movie atoms have an atom type of 'moov'. These atoms act as a container for the informationthat describes a movie’s data. This information, or metadata, is stored in a number of different types of atoms.Generally speaking, only metadata is stored in a movie atom. Sample data for the movie, such as audio or videosamples, are referenced in the movie atom, but are not contained in it.The movie atom is essentially a container of other atoms. These atoms, taken together, describe the contentsof a movie. At the highest level, movie atoms typically contain track atoms, which in turn contain media atoms.At the lowest level are the leaf atoms, which contain non-atom data, usually in the form of a table or a set ofdata elements. For example, a track atom contains an edit atom, which in turn contains an edit list atom , a leafatom which contains data in the form of an edit list table. All of these atoms are discussed later in this document.Figure 2-1 (page 39) provides a conceptual view of the organization of a simple, one-track QuickTime movie.Each nested box in the illustration represents an atom that belongs to its parent atom. The figure does notshow the data regions of any of the atoms. These areas are described in the sections that follow.Note that this figure shows the organization of a standard movie atom. It is possible to compress the moviemetadata using a lossless compression algorithm. In such cases, the movie atom contains only a single childatom—the compressed movie atom ('cmov'). When this child atom is uncompressed, its contents conformto the structure shown in the following illustration. For details, see “Compressed Movie Resources” (page 117)2012-08-14 | © 2004, 2012 Apple Inc. All Rights Reserved.38