S/PDIF ( SPDIF )
IEC958 (named IEC60958 at 1998)
'Sony/Philips Digital Interface'
IEC958 (named IEC60958 at 1998) is the standard for AES/EBU and S-PDIF.
S/PDIF is the consumer version of the AES/EBU-interface.
The two formats differ only in the subcode information and the connector.
S/PDIF was never intended to run through audio cables. It's a 75-ohm format and requires 75-ohm coaxial cable.
It is now usual to use standard audio cable for S/PDIF, but it is not recommended and the
transmission quality can vary.
By specification, the max. length is 25 feet. If good 75-ohm cable with good 75-ohm connectors
is used, it is possible to get
good results with much longer lines. It depends on the quality of the transmitter, the receiver
and the impedance match for the entire line, including the connectors.
| S/PDIF |
| Cable |
75ohm |
|
| Line Driver |
Zout: 75ohm +/-20% (100kHz .. 6Mhz) |
Vout: 0.4Vpp .. 0.6Vpp |
| Line Receiver |
Zin: 75ohm |
Vin: 0.2Vpp .. 0.6Vpp |
| Connector |
RCA (or BNC) |
|
| Signal Level |
0.5..1V |
|
| Modulation |
biphase-mark-code |
|
| Subcode information |
SCMS copy protection info |
|
| Max. Resolution |
20 bits (24 bit optional) |
|
| Comparison between AES/EBU and S/PDIF |
| AES/EBU | S/PDIF (IEC-958) |
| Cabling | 110 ohm shileded TP | 75 ohm coaxial or fiber |
| Connector | 3-pin XLR | RCA (or BNC) |
| Signal level | 2..7V | 0.5..1V |
| Modulation | biphase-mark-code | biphase-mark-code |
| Subcode information | ASCII ID text | SCMS copy protection info |
| Max. Resolution | 24 bits | 20 bits (24 bit optional) |
Digital audio (SPDI/F and AES/EBU) contain frame rate (timing speed) information in the audio bit stream but not frame number (timecode) information. Therefore timecode can not be 'withdrawn' out of the audio bit stream.
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