I have a USB webcam that allows me to use either the built in audio or the audio from the SPDIF input (I assume either the standard RCA-style input or the optical input) but not a standard 3.5mm ...

I'm guessing that "kit"= PCI bracket + adapter cable. I see no reason why you couldn't roll your own coaxial digital connectors (i.e. RCA plugs) for input/output, as long as you wire them up correctly ...

This application note demonstrates the use of the XMOS Sample Rate Conversion library in a system that receives samples from an SPDIF input and outputs them to a DAC over I2S. The XMOS Asynchronous ...