A matrix mixer for the QC USB audio channels.
QC mono mix Row1 out MainOutL and USBout1 to computer.
Processed computer mix of USBout1 back to QC into Row2 set to USBin1.
QC mono mix Row2 out MainOutL (or any other QC output)
Today the routing variants for multiout are not flexible enough.
Instead of adding more variants
a matrix mixer like it is found in RME Audio TotalMix is used
to be able to do any possible routing and store it in the preset/bank/setlist.
The RME hardware does not produce sound itself like the QC does, this is more simple.
So for the QC mixer, the computer must know about and reflect the choosen configuration on the QC.