latticefilt.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:	latticefilt.c
| 
*/

#ifdef SCCS
static char *sccs_id = "@(#)latticefilt.c	1.4 8/20/86 EPI";
#endif
/* Synthesis filter in ladder form */
extern int  smooth_int_flag;
float   lattice_filt (rc, delta_rc, order, lsstate, input)
float   rc[], delta_rc[], lsstate[], input;
int     order;
{
    int     i;
    float   output, ki;

    output = input;
/* Vertical code used to make the program run faster */
    if (smooth_int_flag)
    {
	for (i = order; i > 0; i--)
	{
	    ki = rc[i - 1];
	    output += ki * lsstate[i];
	    lsstate[i + 1] = lsstate[i] - ki * output;
	    rc[i - 1] = ki + delta_rc[i - 1];
	}
    }
    else
    {
	for (i = order; i > 0; i--)
	{
	    ki = rc[i - 1];
	    output += ki * lsstate[i];
	    lsstate[i + 1] = lsstate[i] - ki * output;
	}
    }
    lsstate[1] = output;
    return (output);
}