getarspec.c

speech signal process tools

/*
 * This material contains proprietary software of Entropic Speech, Inc.
 * Any reproduction, distribution, or publication without the prior
 * written permission of Entropic Speech, Inc. is strictly prohibited.
 * Any public distribution of copies of this work authorized in writing by
 * Entropic Speech, Inc. must bear the notice
 *
 *    "Copyright (c) 1986, 1987 Entropic Speech, Inc.; All rights reserved"
 *
 */
/*--------------------------------------------------------------+
|								|
|  get_arspect -- compute max-entropy spectrum from residual 	|
|                 power and filter coefficients			|
|								|
|  by Shankar Narayan, EPI; enhancements by Rod Johnson.	|
|								|
|  Module:  getarspec.c						|
|  								|
|  Accepts an array c of analysis filter coefficients of given	|
|  order, a residual energy renergy, a sampling frequency	|
|  sampfreq, and a number n of frequencies.  Computes an array	|
|  y of (log) spectral power densities in db at n equispaced	|
|  frequencies.  Calls getfft to compute a discrete Fourier	|
|  transform.							|
|								|  
+--------------------------------------------------------------*/
#ifdef SCCS
    static char *sccs_id  = "@(#)getarspec.c	1.2	6/25/87";
#endif

#include <stdio.h>
#include "getarspec.h"

typedef struct complex {
    double  real;
    double  imag;
}       COMPLEX ;

double  log10(), sqrt();
extern  debug_level;


get_arspect(c, order, renergy, sampfreq, y, n)
    int     order, sampfreq, n;
    float   c[], renergy, y[];
{
    double  t;
    int     i;
    static COMPLEX temp[DFTMAX];  /* Size defined in getarspec.h */
    int     dftsize = 2*(n-1);
    c[0] = -1.0;
    if (debug_level)
        fprintf(stderr, "Filter coefficients:\n");
    for (i = 0; i < dftsize; i++)
    {
	temp[i].real = (i <= order) ? c[i] : 0.0;
	temp[i].imag = 0.0;
        if (debug_level)
	{
	    fprintf(stderr, "%lf\t", temp[i].real);
            if (i%5 == 4 || i == dftsize - 1)
                fprintf(stderr, "\n");
        }
    }
    get_fft_comp(temp, dftsize);
    for (i = 0; i < n; i++)
    {
	t = temp[i].real * temp[i].real
	    + temp[i].imag * temp[i].imag;
	if (t < .0000001)
	    t = 0.0000001;
	y[i] = 10.0 * log10((2.0*renergy) / (t*sampfreq));
    }
}