S/PDIF

S/PDIF, also referred to as SPDIF, is a data link and physical specification for transmitting digital audio streams. S/PDIF signals may be sent across coaxial or optical (TOSLINK) cables. It stands for Sony/Phillips Digital Interconnect Format.

The signals generally carried across S/PDIF connections are either 16 bit / 44.1kHz CD audio or 5.1 (or 3/2) surround sound for DVDs, digital television, or other consumer formats.

Because S/PDIF was developed prior to uncompressed or losslessly compressed multichannel surround sound it's not capable of carrying such a signal. It can carry 24 bit audio at 96kHz on 2 channels, but additional channels or sample frequencies require either 6 channel analog connections or HDMI for a digital signal.