dspl/freqz_8c_source.html

/*

* Copyright (c) 2015-2024 Sergey Bakhurin

* Digital Signal Processing Library [http://dsplib.org]

*

* This file is part of libdspl-2.0.

*

* is free software: you can redistribute it and/or modify

* it under the terms of the GNU Lesser    General Public License as published by

* the Free Software Foundation, either version 3 of the License, or

* (at your option) any later version.

*

* DSPL 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 General Public License for more details.

*

* You should have received a copy of the GNU Lesser General Public License

* along with Foobar.    If not, see <http://www.gnu.org/licenses/>.

*/


#include <stdlib.h>

#include <string.h>

#include <math.h>

#include "dspl.h"


#ifdef DOXYGEN_ENGLISH


#endif

#ifdef DOXYGEN_RUSSIAN


#endif

int DSPL_API freqz(double* b, double* a, int ord, double* w,

                   int n, complex_t *h)

{

    complex_t jw;

    complex_t *bc = NULL;

    complex_t *ac = NULL;

    complex_t num, den;

    double mag;

    int k;

    int res;


    if(!b || !w || !h)

        return ERROR_PTR;

    if(ord<0)

        return ERROR_FILTER_ORD;

    if(n<1)

        return ERROR_SIZE;


    bc = (complex_t*) malloc((ord+1) * sizeof(complex_t));

    res = re2cmplx(b, ord+1, bc);

    if( res!=RES_OK )

        goto exit_label;


    if(a)

    {

        /* IIR filter if a != NULL */

        ac = (complex_t*) malloc((ord+1) * sizeof(complex_t));

        res = re2cmplx(a, ord+1, ac);

        if( res!=RES_OK )

            goto exit_label;

        for(k = 0; k < n; k++)

        {

            RE(jw) =  cos(w[k]);

            IM(jw) = -sin(w[k]);

            res = polyval_cmplx(bc, ord, &jw, 1, &num);

            if(res != RES_OK)

                goto exit_label;

            res = polyval_cmplx(ac, ord, &jw, 1, &den);

            if(res != RES_OK)

                goto exit_label;

            mag = ABSSQR(den);

            if(mag == 0.0)

            {

                res = ERROR_DIV_ZERO;

                goto exit_label;

            }

            mag = 1.0 / mag;

            RE(h[k]) = CMCONJRE(num, den) * mag;

            IM(h[k]) = CMCONJIM(num, den) * mag;

        }

    }

    else

    {

        /* FIR filter if a == NULL */

        for(k = 0; k < n; k++)

        {

            RE(jw) =    cos(w[k]);

            IM(jw) = -sin(w[k]);

            res = polyval_cmplx(bc, ord, &jw, 1, h+k);

            if(res != RES_OK)

                goto exit_label;

        }

    }

    res = RES_OK;

exit_label:

    if(bc)

        free(bc);

    if(ac)

        free(ac);

    return res;

}