macOS Equalizer

It's just a bunch of Slider controls. The audio 'brains' behind what an EQ actually does are probably complicated.

http://en.wikipedia.org/wiki/Equalization_(audio)

Resister said:

Yeah, I'm just wanting to know if anyone has any code for the "brains" of it.

I've read that Apple's AudioUnits would need to be used, but thats a bit above me.

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A digital equaliser requires some rather complex maths, FFTs, manipulating the frequencies, transforming back, doing everything very carefully to avoid audible glitches, so I think going through the documentation for audio units is your best chance.

BTW. If you find something in there that allows changing playback speed without changing pitch I would be interested in hearing about that, just out of curiosity.

You may want to look at CoreAudio

Free software

You might want to search for free open software doing audio editing. Reading the source code might help in understanding how the algorithms work. You might also have a starting point for experiments.

The projects coming to my mind are
Audacity -- I believe it only runs equalizer in "batch" mode
Ardour -- source code available

//gunnar

gnasher729 said:

BTW. If you find something in there that allows changing playback speed without changing pitch I would be interested in hearing about that, just out of curiosity.

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Core Audio on Mac OS X includes the AUTimePitch Audio Unit.

On iOS, Dirac reportedly sells a commercial time pitch library.