A collection of IIR/FIR filter and filterbank designs. More...

#include "saf_utilities.h"

Enumerations
enum	BIQUAD_FILTER_TYPES { BIQUAD_FILTER_LPF , BIQUAD_FILTER_LPF_EQCB , BIQUAD_FILTER_HPF , BIQUAD_FILTER_HPF_EQCB , BIQUAD_FILTER_PEAK , BIQUAD_FILTER_PEAK_EQCB , BIQUAD_FILTER_LOW_SHELF , BIQUAD_FILTER_LOW_SHELF_EQCB , BIQUAD_FILTER_HI_SHELF , BIQUAD_FILTER_HI_SHELF_EQCB }
	Bi-quadratic (second-order) IIR filter design options. More...

enum	BUTTER_FILTER_TYPES { BUTTER_FILTER_LPF , BUTTER_FILTER_HPF , BUTTER_FILTER_BPF , BUTTER_FILTER_BSF }
	Butterworth Infinite Impulse Response (IIR) filter design options. More...

enum	FIR_FILTER_TYPES { FIR_FILTER_LPF , FIR_FILTER_HPF , FIR_FILTER_BPF , FIR_FILTER_BSF }
	Finite Impulse Response (FIR) filter design options. More...

enum	WINDOWING_FUNCTION_TYPES { WINDOWING_FUNCTION_RECTANGULAR , WINDOWING_FUNCTION_HAMMING , WINDOWING_FUNCTION_HANN , WINDOWING_FUNCTION_BARTLETT , WINDOWING_FUNCTION_BLACKMAN , WINDOWING_FUNCTION_NUTTALL , WINDOWING_FUNCTION_BLACKMAN_NUTTALL , WINDOWING_FUNCTION_BLACKMAN_HARRIS }
	Windowing function types. More...

Functions
void	getWindowingFunction (WINDOWING_FUNCTION_TYPES type, int winlength, float *win)
	Computes the weights of a specific windowing function.

void	getOctaveBandCutoffFreqs (float centreFreqs, int nCentreFreqs, float cutoffFreqs)
	Converts octave band CENTRE frequencies into CUTOFF frequencies.

void	flattenMinphase (float *x, int len)
	Equalises input sequence by its minimum phase form, in order to bring its magnitude response to unity, as described in [1].

void	interpolateFiltersH (int inFFTsize, int outFFTsize, int nFilters, float_complex filters_in, float_complex filters_out)
	Interpolate filters (w.r.t.

float	convertBW2Q (float BW)
	Converts filter octave band-width to Q-factor.

float	convertQ2BW (float Q)
	Converts filter Q-factor to octave band-width.

void	biQuadCoeffs (BIQUAD_FILTER_TYPES filterType, float fc, float fs, float Q, float gain_dB, float b[3], float a[3])
	Calculates 2nd order IIR filter coefficients [1].

void	applyBiQuadFilter (float b[3], float a[3], float w_z_12[2], float *signal, int nSamples)
	Applies biQuad filter to an input signal using the direct form II difference equation: https://en.wikipedia.org/wiki/Digital_biquad_filter.

void	evalBiQuadTransferFunction (float b[3], float a[3], float freqs, int nFreqs, float fs, int mag2dB, float magnitude, float *phase_rad)
	Evaluates the 2nd order IIR transfer function at one or more frequencies, returning its magnitude and/or phase response.

void	evalIIRTransferFunction (double b, double a, int nCoeffs, float freqs, int nFreqs, float fs, int mag2dB, float magnitude, float *phase_rad)
	Computes magnitude and phase response of an IIR filter from its coefficients at user-specified frequencies (Hz).

void	evalIIRTransferFunctionf (float b, float a, int nCoeffs, float freqs, int nFreqs, float fs, int mag2dB, float magnitude, float *phase_rad)
	Computes magnitude and phase response of an IIR filter from its coefficients (floats) at user-specified frequencies (Hz).

void	applyIIR (float in_signal, int nSamples, int nCoeffs, float b, float a, float wz, float *out_signal)
	Applies an IIR filter to a time-domain signal (using the direct form II difference equation)

void	butterCoeffs (BUTTER_FILTER_TYPES filterType, int order, float cutoff1, float cutoff2, float sampleRate, double b_coeffs, double a_coeffs)
	Computes Butterworth IIR filter coefficients [1].

void	faf_IIRFilterbank_create (void *phFaF, int order, float fc, int nCutoffFreqs, float sampleRate, int maxNumSamples)
	Computes a bank of IIR filter coefficients required to divide a signal into frequency bands, based on the design by Favrot & Faller [1].

void	faf_IIRFilterbank_apply (void hFaF, float inSig, float **outBands, int nSamples)
	Applies the Favrot & Faller filterbank.

void	faf_IIRFilterbank_flushBuffers (void *hFaF)
	Zeros the delay lines used during faf_IIRFilterbank_apply()

void	faf_IIRFilterbank_destroy (void **hFaF)
	Destroys an instance of the Favrot & Faller filterbank.

void	FIRCoeffs (FIR_FILTER_TYPES filterType, int order, float cutoff1, float cutoff2, float sampleRate, WINDOWING_FUNCTION_TYPES windowType, int scalingFLAG, float *filter)
	Computes FIR filter coefficients by windowing.

void	FIRFilterbank (int order, float fc, int nCutoffFreqs, float sampleRate, WINDOWING_FUNCTION_TYPES windowType, int scalingFLAG, float filterbank)
	Computes a bank of FIR filter coefficients required to divide a signal into frequency bands.

Detailed Description

A collection of IIR/FIR filter and filterbank designs.

Author: Leo McCormack

Date: 01.03.2019

License: ISC

Definition in file saf_utility_filters.h.

Enumerations

Functions

Detailed Description