S/PDIF or SPDIF stands for Sony/Philips Digital Interconnect Format, and only slightly differs from the AES/EBU format. This type of audio format is used to carry compressed digital audio signals, defined by the standard IEC 61937. S/PDIF may carry the audio from a CD player to your headphones, for example. That is, if you still even use portable CD players. Another use would be to carry the audio from a DVD player to the surround sound speakers.

While the actual top transmission rate of S/PDIF is never specified, but maxes out somewhere around 20 bits. CD’s sound limitations are set at 16 bits, so S/PDIF can transport the audio as well as the CD can pump it out. However, if an audio signal of something higher than 20 bits is sent through S/PDIF, it will just shave the rest off and maxes out at 20 bits. For it’s current uses, this problem doesn’t tend to occur too often.

The data itself is carried via a stream that can be broken down into 32 bit data “words”, with 192 words one channel and 192 on the other channel, totaling 284 words. As previosuly mentioned, S/PDIF only slightly differs from AES/EBU, which is another transport standard. The differences are as follows:

• Cabling: AES/EBU - 110 ohm shielded TP (or a 75 ohm coaxial)
  S/PDIF - 75 ohm coaxial or fibre
• Connector:   AES/EBU - Either a BNC, a 25-Pin D-subminiature, or a 3-pin XLR
  S/PDIF - BNC, RCA, or a TOSLINK
• Max Res:       AES/EBU - 24 bits
  S/PDIF - 20 bits
• Modulation: AES/EBU - Biphase mark code
  S/PDIF - This also uses the Biphase mark code
• Signal Level: AES/EBU - 3V to 10V
  S/PDIF - 0.5V to 1V
• Subcode info: AES/EBU - ASCII ID text
  S/PDIF -SCMS copy protection

What is the biphase mark code?

This is a type of encoding used in binary data streams. Binary numbers consist of 1’s and 0’s, and mean either open gate or close gate, and is essentially how your computer operates. The number 1 represents open gate and the number zero represents a closed gate. If a value is not set, such as in a boolean value, the default return value is false, or closed gate (0). Sometimes when the stream is being sent and hasn’t been modified via a channel, there may be a long string of 0’s (or 1’s), which can mess up the synchronization. Biphase mark code is used to fix this, as it makes sure there is at least one transition between every bit on the channel, as to help keep it synchronized.

Related posts:

1. ESN Electronic Serial Number Electronic Serial Numbers (ESNs) are used to identify mobile devices,...
2. No Audio Device The first step to solving your “no audio device” problem...
3. What is DVB-H DVB-H is one of three existent mobile TV formats available...
4. List of Stop Words What are stop words - stop words are commonly used...
5. How does Television broadcasting work Television Broadcasting has major components involved in order to receive...