Specification of audio representations in audio-related standards: Three audio representations: channel-based, object-based, and scene-based

Currently, there are three mainstream audio representations, namely channel-based audio, object-based audio, and scene-based audio. The features of content expression differ among these audio representations, the details of which have been specified in the International Telecommunication Union: Radiocommunication Sector (ITU-R) Recommendations. The effective use of these audio representations in accordance with what is to be expressed in the content requires a deep understanding of the technical specifications and capabilities of the audio representations. This review first traces the evolution of loudspeaker layouts developed in recent years, i.e., a history of multichannelization, which is indispensable for the understanding of audio representations. Then, the position of each audio representation among various audio-related standards is described and the method of adopting and implementing each audio representation in other audio-related standards is reviewed using the Moving Picture Experts Group (MPEG) standards as examples.