ref: c770ed0961baf45b0fbc905dfe629f1a4f7ba7c4
dir: /lpc10/ivfilt.c/
/*
* Revision 1.1 1996/08/19 22:31:53 jaf
* Initial revision
*
*/
/* -- translated by f2c (version 19951025).
You must link the resulting object file with the libraries:
-lf2c -lm (in that order)
*/
#include "f2c.h"
extern int ivfilt_(real *lpbuf, real *ivbuf, integer *len, integer *nsamp, real *ivrc);
/* ********************************************************************* */
/* IVFILT Version 48 */
/*
* Revision 1.1 1996/08/19 22:31:53 jaf
* Initial revision
* */
/* Revision 1.3 1996/03/15 21:36:29 jaf */
/* Just added a few comments about which array indices of the arguments */
/* are used, and mentioning that this subroutine has no local state. */
/* Revision 1.2 1996/03/13 00:01:00 jaf */
/* Comments added explaining that none of the local variables of this */
/* subroutine need to be saved from one invocation to the next. */
/* Revision 1.1 1996/02/07 14:47:34 jaf */
/* Initial revision */
/* ********************************************************************* */
/* 2nd order inverse filter, speech is decimated 4:1 */
/* Input: */
/* LEN - Length of speech buffers */
/* NSAMP - Number of samples to filter */
/* LPBUF - Low pass filtered speech buffer */
/* Indices LEN-NSAMP-7 through LEN read. */
/* Output: */
/* IVBUF - Inverse filtered speech buffer */
/* Indices LEN-NSAMP+1 through LEN written. */
/* IVRC - Inverse filter reflection coefficients (for voicing) */
/* Indices 1 and 2 both written (also read, but only after writing).
*/
/* This subroutine has no local state. */
/* Subroutine */ int ivfilt_(real *lpbuf, real *ivbuf, integer *len, integer *
nsamp, real *ivrc)
{
/* System generated locals */
integer i__1;
/* Local variables */
integer i__, j, k;
real r__[3], pc1, pc2;
/* Arguments */
/* Local variables that need not be saved */
/* Local state */
/* None */
/* Calculate Autocorrelations */
/* Parameter adjustments */
--ivbuf;
--lpbuf;
--ivrc;
/* Function Body */
for (i__ = 1; i__ <= 3; ++i__) {
r__[i__ - 1] = 0.f;
k = (i__ - 1) << 2;
i__1 = *len;
for (j = (i__ << 2) + *len - *nsamp; j <= i__1; j += 2) {
r__[i__ - 1] += lpbuf[j] * lpbuf[j - k];
}
}
/* Calculate predictor coefficients */
pc1 = 0.f;
pc2 = 0.f;
ivrc[1] = 0.f;
ivrc[2] = 0.f;
if (r__[0] > 1e-10f) {
ivrc[1] = r__[1] / r__[0];
ivrc[2] = (r__[2] - ivrc[1] * r__[1]) / (r__[0] - ivrc[1] * r__[1]);
pc1 = ivrc[1] - ivrc[1] * ivrc[2];
pc2 = ivrc[2];
}
/* Inverse filter LPBUF into IVBUF */
i__1 = *len;
for (i__ = *len + 1 - *nsamp; i__ <= i__1; ++i__) {
ivbuf[i__] = lpbuf[i__] - pc1 * lpbuf[i__ - 4] - pc2 * lpbuf[i__ - 8];
}
return 0;
} /* ivfilt_ */