Wide atom ('wide')
An atom that designates reserved space in the movie data file.
Overview
A wide atom typically precedes a movie data atom. The wide atom consists only of a type and size field. This occupies 8 bytes—enough space to add an extended size field to the header of the atom that follows, without displacing the contents of that atom. If an atom grows to exceed 2^32 bytes in size, and it is preceded by a wide atom, you may create a new atom header containing an extended size field by overwriting the existing atom header and the preceding wide atom.