S/PDIF

showstack / protocols / spdif

Also called Sony/Philips Digital Interface, IEC 60958 Type II, SPDIF.

The consumer form of AES3: the same two-channel data format at a much lower voltage, on 75 Ω coax with an RCA connector or on TOSLINK optical fibre. Same bits, different electrical world.

Audio transportPaid specIECReported

Media Large, continuous, on time and in order

Continuous streams that are large enough to be sized properly, and that must arrive in order and on time.

What kills it. Anything that starves the link — usually a management transfer nobody scheduled — and jitter that outruns the receive buffer.

The four flows, and why the model is worth having →

What it carries

Sample rates: 32 kHz, 44.1 kHz, 48 kHz
Audio bit depth: 24-bit
Audio channels: up to 2
Audio encoding: Linear PCM, or a compressed bitstream carried transparently

Audio: The consumer form of AES3. It also carries compressed multichannel bitstreams unchanged, which is why a receiver can be handed something it cannot decode and simply produce nothing.

What goes wrong

Nominal 0.5 V peak-to-peak on 75 Ω, against AES3's several volts on 110 Ω. The data survives a converter; it does not survive a soldered adaptor.

Practical coax runs are short — around 10 m is the usual working figure. TOSLINK is shorter still and intolerant of tight bends.

Consumer channel-status bits carry copy-protection flags that some professional receivers act on and others ignore.

Typical use

Consumer and semi-pro playback sources into a system
Optical feeds where galvanic isolation is wanted
Interfacing a laptop or media player to a professional chain

Sources

IEC 60958-3 — Digital audio interface, Part 3 Consumer applications — International Electrotechnical Commission primary
Interfacing AES3 and S/PDIF (RaneNote 149) — Rane Corporation

Understand the mechanism

Show networks Numbers that stand for signals

Something wrong, or missing?

Known gaps on this entry: default_ports, first_published, implementations. If you can source one of them, that is a ten minute pull request.

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