Demuxing

Process that reads the container format and separates audio, video, and subtitles, if any. Demuxing files doesn't weaken the video nor audio quality, it doesn't do anything for these data streams, it just simply saves them into separate files, each containing one element of the original file.

VLC uses modules called demuxer module or demuxer to do that. Examples of demuxers are WMV/ASF, Ogg or Mkv.