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I'm looking to build a really simple EQ that plays a filtered version of a song in the user's library. It would essentially be a parametric EQ: I'd specify the bandwidth, cut/boost (in dB), and centre frequency, and then be returned some object that I could play just like my original MPMediaItem.

For MPMediaItems, I've generally used AVAudioPlayer in the past with great success. For audio generation, I've used AudioUnits. In MATLAB, I'd probably just create custom filters to do this. I'm at a bit of a loss for how to approach this in iOS! Any pointers would be terrific. Thanks for reading

Rogare
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1 Answers1

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iOS ships with a fairly sizeable number of audio units. One of kAudioUnitSubType_ParametricEQ, kAudioUnitSubType_NBandEQ or kAudioUnitSubType_BandPassFilter is probably what you want depending on whether you want to control Q as well as Fc and Gain.

I suspect you will have to forego using higher-level components such as AVAudioPlayer to make use of it.

The relevant iOS audio unit reference can be found here

marko
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  • It seems that Audio Units are exactly what I need, but I'm struggling with getting an item from the music library to the Units. I'll be investigating AVAssetReaders for now to do this. – Rogare Feb 17 '14 at 18:40