What is "demultiplexer"

n. (context computing electronics English) A device or piece of software used to separate signals that were previously combined using a multiplexer.

A demultiplexer for digital media files, or media demultiplexer also called a file splitter by laymen or consumer software providers, is software that demultiplexes individual elementary streams of a media file, e.g., audio, video, or subtitles and sends them to their respective decoders for actual decoding. Media demultiplexers are not decoders themselves, but are format container handlers that separate program streams from a file and supply them to their respective audio, video, or subtitles decoders.