preemp.c File Reference

#include "f2c.h"

Include dependency graph for preemp.c:

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Functions
int	preemp_ (real *inbuf, real *pebuf, integer *nsamp, real *coef, real *z__)

Function Documentation

preemp_()

int preemp_	(	real *	inbuf,
		real *	pebuf,
		integer *	nsamp,
		real *	coef,
		real *	z__
	)

Definition at line 82 of file preemp.c.

References inbuf().

Referenced by analys_().

{
 /* System generated locals */
 integer i__1;

 /* Local variables */
 real temp;
 integer i__;

/* Arguments */
/* Local variables */

/* None of these need to have their values saved from one */
/* invocation to the next. */

/* Logically, this subroutine computes the output sequence */
/* pebuf(1:nsamp) defined by: */

/* pebuf(i) = inbuf(i) - coef * inbuf(i-1) */

/* where inbuf(0) is defined by the value of z given as input to */
/* this subroutine. */

/* What is this filter's frequency response and phase response? */

/* Why is this filter applied to the speech? */

/* Could it be more efficient to apply multiple filters */
/* simultaneously, by combining them into one equivalent filter? */

/* Are there ever cases when "factoring" one high-order filter into
*/
/* multiple smaller-order filter actually reduces the number of */
/* arithmetic operations needed to perform them? */
/* When I first read this subroutine, I didn't understand why the */
/* variable temp was used. It seemed that the statements in the do
*/
/* loop could be replaced with the following: */

/* pebuf(i) = inbuf(i) - coef * z */
/* z = inbuf(i) */

/* The reason for temp is so that even if pebuf and inbuf are the */
/* same arrays in memory (i.e., they are aliased), then this */
/* subroutine will still work correctly. I didn't realize this */
/* until seeing the comment after PEBUF above that says "(can be */
/* equal to INBUF)". */
 /* Parameter adjustments */
 --pebuf;
 --inbuf;

 /* Function Body */
 i__1 = *nsamp;
 for (i__ = 1; i__ <= i__1; ++i__) {
 temp = inbuf[i__] - *coef * *z__;
 *z__ = inbuf[i__];
 pebuf[i__] = temp;
/* L10: */
 }
 return 0;
} /* preemp_ */