Dsd upsampling, parallel processing: allow to use more than 2 cores

[WiWavelength (Andrew J Shepherd)]

Roon CTO several years ago already addressed multi core DSP. Not likely to be implemented because of inefficiency and tradeoffs.

DSD512 - Is this even possible? [yes, just needs more cpu]

The majority of systems used to run Roon have 2 cores / 4 threads or less. NUCs are the typical archetype. We monitor these stats on an ongoing basis to drive these decisions. There is overhead associated to splitting/joining work across cores. It is most efficient to run things on 1 core if they fit there. We enabled the split to 2 cores as a technique for making extreme DSD upsampling cases workable. Unnecessary multi-core processing has other have negative consequences for the overall user…

AJ