To provide a definition of the encoding format for audio and video. This is provided as free text in an annotation label or as an identifier pointing to a term in a classification scheme e.g. http://www.ebu.ch/metadata/ontologies/skos/ebu_AudioCompressionCodeCS.rdf or http://www.ebu.ch/metadata/ontologies/skos/ebu_VideoCompressionCodeCS.rdf.