[PD] latest Pd-Extended cpu usage (was: new editing features of Pd-extended 0.43, now in beta)

[Jamie Bullock]

On 28 Feb 2012, at 21:10, katja wrote:

> 
> 
> On Tue, Feb 28, 2012 at 9:06 PM, Jamie Bullock <jamie at 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.
> 

It seems that you're right, so I've closed the bug (my apologies to PortAudio!). 

I guess the real 'fix' for this is that Pd now has a block size setting in Preferences. With a block size of 1024, using the PortAudio driver I get a CPU use of <2% with DSP on. Checking "use callbacks" also seems to reduce CPU. Here, I got a reduction of ~2% with that checked.

Also, I'm not sure if this is an improvement in recent versions of OS X, but Pd now runs at only ~5% with DSP on using the PortAudio driver with a blocksize of 64. This is on a MacBook Air i7/1.8.

best,

Jamie

--
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