Functions for generic, 3 tap, iir filtering. More...

Functions
void	iir_filt_forward (float in, int stepin, float out, int stepout, int length, float coeffs, float i0)
	Functions iir_filt_forward and iir_filt_backward do a 3 tap recursive filtering operation on floating point buffers. More...

void	iir_filt_backward (float in, int stepin, float out, int stepout, int length, float coeffs, float i0)

void	iir_filt_forward (float in, float out, int length, float coeffs, float i0)

void	iir_filt_backward (float in, float out, int length, float coeffs, float i0)

void	iir_filt_forward (float in, float out, int stepout, int length, float coeffs, float i0)

void	iir_filt_backward (float in, float out, int stepout, int length, float coeffs, float i0)

void	iir_filt_forward (float in, int stepin, float out, int length, float coeffs, float i0)

void	iir_filt_backward (float in, int stepin, float out, int length, float coeffs, float i0)

Detailed Description

Functions for generic, 3 tap, iir filtering.

Author: Alex Bernardino, ISR-IST

Date: 2006-2007

Note: Release under GNU GPL v2.0

Author: Alex Bernardino, ISR-IST

Date: 2006-2007

Note: Released under GNU GPL v2.0

See also: IIRFilt.h

Definition in file IIRFilt.h.

Function Documentation

◆ iir_filt_forward()

void iir_filt_forward	(	float *	in,
		int	stepin,
		float *	out,
		int	stepout,
		int	length,
		float *	coeffs,
		float *	i0
	)

Functions iir_filt_forward and iir_filt_backward do a 3 tap recursive filtering operation on floating point buffers.

Forward filtering:

$y(t) = b_0 x(t) - a_1 y(t-1) - a_2 y(t-2) - a_3 y(t-3)$

Parameters

in	Floating point buffer with the input signal.
stepin	Spacing between consecutive input signal samples.
out	Floating point buffer to store the computation results.
stepout	Spacing between consecutive output buffer samples.
length	Number of samples to process (N)
coeffs	Filter coefficients. A length 4 floating point array containing
i0	Filter boundary conditions. A length 3 floating point array containing: in the forward filtering case $(y_{-1}, y_{-2}, y_{-3})$ in the backward filtering case $(y_{N}, y_{N+1}, y_{N+2})$

Note: Several overloads exist for the cases when stepin or stepout parameters are unitary.

Definition at line 19 of file IIRFilt.cpp.

 {
     int j;
     float b0 = coeffs[0];
     float a1 = coeffs[1]; 
     float a2 = coeffs[2];
     float a3 = coeffs[3];
  
     out[0] = b0*in[0] - a1*i0[0] - a2*i0[1] - a3*i0[2];
     out[1*stepout] = b0*in[stepin] - a1*out[0] - a2*i0[0] - a3*i0[1];
     out[2*stepout] = b0*in[2*stepin] - a1*out[stepout] - a2*out[0] - a3*i0[0];
     for(j = 3; j < length; j++)
         out[j*stepout] = b0*in[j*stepin] - a1*out[(j-1)*stepout] - a2*out[(j-2)*stepout] - a3*out[(j-3)*stepout];
 }