FPGA S/PDIF digital audio mixer

In the process of learning FPGA development I'm making a digital audio mixer that takes a couple of S/PDIF inputs, decodes the samples, passes them through volume controllers and then mixes them together into a new output signal.

Currently the receiver stage is functional and work is currently being done on the mixing stage. In the meantime it's sitting on my desk, acting as a TPPM (True Peak Programme Meter) using the on-board LEDs on the DE0-Nano FPGA development board, as can be seen in the video below (early test, meter looks better now).


I made a very basic I/O-board with 2x Toslink transmitters (TOTX177), 4x receivers (TORX177) and a header to connect it to the FPGA. Later on this will also host the mixer controls and VU-meters.