On Tue, Feb 28, 2012 at 9:06 PM, Jamie Bullock <jamie@postlude.co.uk> wrote:

Yup, I think this is related to the Portaudio driver. I reported it here:

http://sourceforge.net/tracker/?func=detail&aid=3100679&group_id=55736&atid=478070

I don't think it's Portaudio itself that's at fault, but rather the way it interfaces with Pd.

DspFuncLib is in:

/System/Library/Extensions/AppleHDA.kext/Content/Plugins/DspFuncLib.kext/Contents/MacOS.

If you run command nm on the lib, you'll see a plethora of dsp functions like MultiBandCompressor, NoiseCanceller, Loudness, Softclip, Limiter and whatnot. Functions in this lib are called when the internal soundcard is used. When using an external soundcard with Pd, DspFuncLib is not called and that makes the big difference in CPU load.

AppleHDA and mach_kernel are Apple libs as well and together with DspFuncLib they are responsible for the crazy CPU load in the 'idle-but-dsp-on' case.

PortAudio functions are apparently statically built into Pd and they consume very little CPU time.

Katja