SPDIF on the network set-top box refers to Sony/Philips digital interface format (short for Sony and Philips digital audio interface).

As far as transmission modes are concerned, SPDIF can be divided into two types: output type (SPDIF output) and input type (SPDIF input). At present, most sound card chips can support SPDIF output, but it should be noted that not every product will provide digital interface. There are relatively few sound card chips supporting SPDIF IN, such as EMU 10K 1, YMF-744, FM80 1-AU, CMI8738, etc. The typical application of SPDIF in sound card is CD SPDIF, but not every sound card supporting SPDIF provides this interface.