Sound Tweak Rpi4

[philrandal]

The case against preempt is it hurts performance a bit, the voluntary setting seems like a good compromise especially for older hardware. The Pi 4 can afford to give up a few cycles, especially in an audio context where the processor isn’t working very hard and the newer processor might not suffer as much of a perf hit. 

Back when the linked tweaks were under a different name I thought they helped when running the 32-bit kernel but were counterproductive with the newer mpd versions and/or 64-bit kernel (can’t remember the timeline, it was one of them though). It was never a big difference in any case. I used to underclock and do the other type of tweaks until I complained once to Tim about library loading being slower in a test version and tracing the difference to those changes. It had a pretty noticeable impact and any sound improvement was very minor so I stopped bothering when I moved to the Pi 4. I might try the non-config.txt ones again out of nostalgia.

The tweaks were @dynobot's.

I just refactored his script to make it more readable and use unique files for the tweaks.  His original stuff is now back up on github.

On a Pi 3B, I still hear a difference, but I haven't tracked down which of those changes is responsible.

As one of those still working through lockdown, I have had limited opportunity to play with this.

On my hardware (see my sig) 64-bit kernel, sox 32/384 highest quality sounds best to my ears.

Phil