(1) In Core Audio, a linear block of data consisting of a short, descriptive header followed by the described data. A chunk-based file is an on-disk file laid out as a series of chunks. (2) In QuickTime, A collection of sample data in a media structure. Chunks, which may contain one or more samples, allow optimized data access. Chunks in a media structure may have different sizes, and the samples within a chunk may have different sizes.