Abstract: An Audio Visual reproduction system for reproducing data from a composite media stream with various stream types including video, audio, and subtitle stream. The audio stream may include a plurality of interchangeable audio substreams and the subtitle stream may include a plurality of interchangeable subtitle substreams. Selected substreams may be simultaneously reproduced under user control. The reproduction includes a composite media stream separator unit, a video decoder unit, an audio decoder unit, and a subtitle decoder unit. The audio decoder unit can simultaneously decode a plurality of audio substreams to produce a plurality of audio outputs. The subtitle decoding unit can simultaneously decode a plurality of subtitle substreams to produce a plurality of subtitle outputs. A player and user model for simultaneously utilizing multiple substreams of a stream type contained within an application that conforms to a standard wherein only one substream of each stream type is used.