S/PDIF, which stands for Sony/Philips Digital Interface Format, is a commonly used audio interface that allows the transmission of digital audio signals between audio devices. When it comes to the number of audio channels supported by S/PDIF, it depends on whether the audio is compressed or uncompressed.
In the case of uncompressed audio, S/PDIF can carry two channels of PCM (Pulse Code Modulation) audio. PCM is the standard method used to digitally represent analog audio signals. It samples the audio wave at regular intervals and converts it into a series of binary numbers, which can be transmitted and reconstructed as analog audio at the receiving end. So, with S/PDIF, you can transmit two separate audio channels in their uncompressed form.
On the other hand, S/PDIF is also capable of carrying compressed audio formats, such as Dolby Digital or DTS, which are commonly used for surround sound systems. These formats utilize data compression techniques to reduce the amount of data needed to transmit the audio signal. In the case of compressed formats, S/PDIF can support 5.1 or 7.1 channels of audio, which means it can transmit a multi-channel surround sound signal to compatible devices.
However, it’s important to note that S/PDIF has limitations in terms of bandwidth, and it cannot support lossless audio formats that require higher data rates. Lossless audio formats, such as FLAC (Free Lossless Audio Codec) or ALAC (Apple Lossless Audio Codec), preserve the original audio quality without any loss of information. These formats typically require a higher bandwidth than what S/PDIF can provide.
In my personal experience, I have used S/PDIF connections to transmit stereo audio between devices such as CD players, audio interfaces, and home theater systems. It has been a reliable and convenient method for connecting audio devices, especially when I wanted to maintain the original uncompressed audio quality. However, when dealing with surround sound systems or lossless audio formats, I have had to rely on other interfaces, such as HDMI or Ethernet-based audio protocols, which can support higher channel counts and bandwidths.
To summarize, S/PDIF can support two channels of uncompressed PCM audio or compressed 5.1/7.1 surround sound. It is a widely used interface for transmitting digital audio signals, but it has limitations when it comes to supporting lossless audio formats that require greater bandwidth.