Digital screen media expert witnesses may opine on video files, media formats, media players, and associated matters. The Digital Screen Media Association offers a glossary at http://www.digitalscreenmedia.org/glossary including:
Back channel – a data communication from which a media player exchanges information with a network management server. The back channel communications include content and playlist download, playback and system log upload, remote system control, etc.
Read more: digitalscreenmedia.org.