ITU-R has developed Recommendation ITU-R BS.775 for multichannel stereophonic sound system with and without accompanying picture. Multichannel stereo as well as 2-channel stereo audio services are widely used as part of digital broadcasting services. Recommendation ITU-R BS.775 specifies a hierarchy of compatible multichannel sound systems to enhance the directional stability of the frontal sound image and the sensation of spatial reality (ambience), and each loudspeaker is set at the same height as a listener’s ears.