Editing S/PDIF (section)

==== IEC 61937 encapsulation ====
IEC 61937 defines a way to transmit compressed, multi-channel data over S/PDIF.<ref>Digitalton - Schnittstelle für nichtlinear-PCM-codierte Audio-Bitströme unter Verwendung von IEC 60958 - Teil 1: Allgemeines (IEC 61937-1:2007 + A1:2011); Deutsche Fassung EN 61937-1:2007 + A1:2011</ref>

* The control word bit 0:1 is set to indicate the presence of non-linear-PCM data.
* The sample rate is set to maintain the needed symbol (data) rate. The symbol rate is usually 64 times the sample rate.
* Data is packed into blocks. Each data block is given a IEC 61937 preamble, containing two 16-bit sync words and indicating the state and identity (type, validity, bitstream number, length) of encapsulated data present. Padding is added to match full block size as required by timing.

A number of encodings are available over IEC 61937, including Dolby [[Dolby Digital|AC-3]]/[[E-AC-3]], [[Dolby TrueHD]], MP3, AAC, [[ATRAC]], [[DTS Coherent Acoustics|DTS]], and [[WMA Pro]].<ref>{{cite web |title=FFmpeg: libavformat/spdif.h File Reference |url=https://ffmpeg.org/doxygen/trunk/spdif_8h.html |website=ffmpeg.org}}</ref><ref>{{cite web |title=Representing Formats for IEC 61937 Transmissions - Win32 apps |url=https://learn.microsoft.com/en-us/windows/win32/coreaudio/representing-formats-for-iec-61937-transmissions |website=learn.microsoft.com |language=en-us |date=15 May 2023}}</ref>