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iosswiftsignalsprocessingsignal-processing
Altair Jones
Altair Jones

Reputation: 914

Applying DSP Filters to data in iOS

I'm working to an app that needs to applying some DSP filters to data coming from sensors. I found the vDSP section of the Accelerate Framework, but the initialisers for the Biquad filter (that then you will apply) expects the a and b coefficients already calculated.

I have the cut-off frequency for the low-pass and high-pass filters and the band interval for the band-pass filter. How do you calculate the coefficients? Is there any specific library? Or does vDSP has some helpers that I wasn't able to find in the documentation?

Thanks

Upvotes: 0

Views: 751

Answers (1)

hotpaw2
hotpaw2

Reputation: 70733

Here's one version of RBJ's canonical Biquad cookbook recipe to compute Biquad coefficients from a description of cutoff frequency and Q, for HP, LP and BP filters:

https://www.w3.org/2011/audio/audio-eq-cookbook.html

Many variants of C source code for RBJ's cookbook on GitHub, for instance:

https://github.com/wooters/miniDSP/blob/master/biquad.c

Should be easy to convert this to Swift.

Upvotes: 1

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