extendrc.c

speech signal process tools

/*
| This material contains proprietary software of Entropic Processing, Inc.
| Any reproduction, distribution, or publication without the the prior
| written permission of Entropic Processing, Inc. is strictly prohibited.
| Any public distribution of copies of this work authorized in writing by
| Entropic Processing, Inc. must bear the notice
|
|              "Copyright 1986 Entropic Processing, Inc."
|
| Written by:  S. Shankar Narayan
|
| Module:	extendrc.c
| 
*/

#ifdef SCCS
static char *sccs_id = "@(#)extendrc.c	1.4 8/20/86 EPI";
#endif
extend_rc (rc, window_size, inp_order, out_order)
int     inp_order, out_order, window_size;
float   rc[];
{
    double  r[100], sin (), w;
    float   state[100], nrc[100], drc[100], a[100], num[100];
    float   fowrd_filter (), gain;
    int     i;

    for (i = 1; i <= inp_order; i++)
    {
	state[i] = 0.0;
	nrc[i] = -rc[i - 1];
	drc[i] = rc[i - 1];
    }
    rctoc (drc, inp_order, a, &gain);
    rctoc (nrc, inp_order, num, &gain);

    r[0] = 1.0;
    num[0] = r[0] / 2.0;
    for (i = 1; i <= inp_order; i++)
	num[i] = -0.5 * r[0] * num[i];
    for (i = inp_order + 1; i <= out_order; i++)
        num[i] = 0;
    for (i = 0; i <= out_order; i++)
	r[i] = fowrd_filter (a, state, inp_order, num[i]);

    r[0] = 2.0 * r[0];

/* Multiplication of auto-correlation by sin(x)/(x) function */
    w = 3.141592654 / window_size;
    for (i = 1; i <= out_order; i++)
	r[i] = r[i] * sin (w * i) / (w * i);

    get_atal (r, out_order, a, rc, &gain);
    for (i = 1; i <= out_order; i++)
	rc[i - 1] =  rc[i];
}