A digital audio communication protocol called S/PDIF is used to transmit music between two devices. It handles both compressed surround sound and raw stereo music and is unidirectional (one-way).

A coaxial or fiber optic wire may be used to send a S/PDIF audio transmission. RCA connections are used for coax communications while Toslink connectors are used for optical transmissions. Any transmission device can be used, but a S/PDIF stream is always digital rather than acoustic.

S/PDIF interfaces on AVRs and other devices might not be consistent since it allows a variety of links. The majority of contemporary S/PDIF-compatible products offer an optical Toslink communication.

S/PDIF is the perfect gateway for Disc players, turntables, and other stereo audio equipment because it allows raw 2-channel (stereo) audio. S/PDIF can send surround sound data, but it only has enough capacity for two channels of raw digital audio to be transmitted at once. In order to transmit 5.1 and 7.2 surround sound music, S/PDIF must use a compressed file, like Dolby Digital.