A set of interfaces and data structures (i.e., a demultiplexer API) for representing a demultiplexer of multimedia data is presented. The data structure utilizes a number of fields, each containing an element of a command. In one embodiment, at least seven commands are formed for proper operation of the demultiplexer, including Initialize, SetPresentationDescriptor, GetPresentationDescriptor, GetPendingPresentationDescriptor, ProcessInput, ProcessOutput, and Flush commands. The demultiplexer API allows the consumer to use muxed stream data such as DV in a uniform manner to generate elementary stream data such as audio and video (compressed or uncompressed) and allows demultiplexers to be used as an independent component.