aptdec/filter.c

/*
 *  Atpdec
 *  Copyright (c) 2003 by Thierry Leconte (F4DWV)
 *
 *      $Id$
 *
 *   This library is free software; you can redistribute it and/or modify
 *   it under the terms of the GNU Library General Public License as
 *   published by the Free Software Foundation; either version 2 of
 *   the License, or (at your option) any later version.
 *
 *   This program is distributed in the hope that it will be useful,
 *   but WITHOUT ANY WARRANTY; without even the implied warranty of
 *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *   GNU Library General Public License for more details.
 *
 *   You should have received a copy of the GNU Library General Public
 *   License along with this library; if not, write to the Free Software
 *   Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 *
 */
#include "filter.h"

float fir( float *buff, const float *coeff, const int len)
{
int i;
double r;

r=0.0;
for(i=0;i<len;i++) {
	r+=buff[i]*coeff[i];
}
return r;
}


void iqfir( float *buff, const float *Icoeff, const float *Qcoeff, const int len, float *Iptr,float *Qptr)
{
int i;
float I,Q;

I=Q=0.0;
for(i=0;i<len;i++) {
	double v;

	v=buff[i];
	I+=v*Icoeff[i];
	Q+=v*Qcoeff[i];
}
*Iptr=I;
*Qptr=Q;
}

float rsfir(float *buff,const float *coeff,const int len , const double offset , const  double delta)
{
int i;
double n;
double out;

out=0.0;
for(i=0,n=offset;n<len-1;n+=delta,i++) {
	int k;
	double alpha;

	k=(int)n;
	alpha=n-k;
	out+=buff[i]*(coeff[k]*(1.0-alpha)+coeff[k+1]*alpha);
}

return out;
}

double iir(double x,iirbuff_t *buff,const iircoeff_t *coeff)
{
buff->x[4]=buff->x[3];
buff->x[3]=buff->x[2];
buff->x[2]=buff->x[1];
buff->x[1]=buff->x[0];
buff->x[0]=x/coeff->G;

buff->y[2]=buff->y[1];
buff->y[1]=buff->y[0];
buff->y[0] = buff->x[4]
     + coeff->x[2] * buff->x[3]
     + coeff->x[1] * buff->x[2]
     + coeff->x[0] * buff->x[1]
     + buff->x[0]
     + coeff->y[1] * buff->y[2]
     + coeff->y[0] * buff->y[1];

return (buff->y[0]);
}