preemp.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:	preemp.c
| 
*/

#ifdef SCCS
static char *sccs_id = "@(#)preemp.c	1.3 8/20/86 (preemp.c)";
#endif
/* pre-emphasis filtering using second order IIR filter */
pre_emphasis(data,length,num,den,state)
float data[],num[],den[],state[];
int length;
{
	int i;
	float temp;

	for (i = 0; i < length; i++)
		{
		temp = data[i] - den[1]*state[0] - den[2]*state[1];
		data[i] = num[0]*temp + num[1]*state[0] + num[2]*state[1];
		state[1] = state[0];
		state[0] = temp;
		}
}