ref: 826ecd8f682bf7396ea9ca0520f589da626ef261
dir: /src/wavesynth/cst_reflpc.c/
/*************************************************************************/
/* */
/* Language Technologies Institute */
/* Carnegie Mellon University */
/* Copyright (c) 2001 */
/* All Rights Reserved. */
/* */
/* Permission is hereby granted, free of charge, to use and distribute */
/* this software and its documentation without restriction, including */
/* without limitation the rights to use, copy, modify, merge, publish, */
/* distribute, sublicense, and/or sell copies of this work, and to */
/* permit persons to whom this work is furnished to do so, subject to */
/* the following conditions: */
/* 1. The code must retain the above copyright notice, this list of */
/* conditions and the following disclaimer. */
/* 2. Any modifications must be clearly marked as such. */
/* 3. Original authors' names are not deleted. */
/* 4. The authors' names are not used to endorse or promote products */
/* derived from this software without specific prior written */
/* permission. */
/* */
/* CARNEGIE MELLON UNIVERSITY AND THE CONTRIBUTORS TO THIS WORK */
/* DISCLAIM ALL WARRANTIES WITH REGARD TO THIS SOFTWARE, INCLUDING */
/* ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS, IN NO EVENT */
/* SHALL CARNEGIE MELLON UNIVERSITY NOR THE CONTRIBUTORS BE LIABLE */
/* FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES */
/* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN */
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/* THIS SOFTWARE. */
/* */
/*************************************************************************/
/* Author: Alan W Black (awb@cs.cmu.edu) */
/* Date: November 2001 */
/*************************************************************************/
/* */
/* reflection coefficients, algorithms from Festival */
/* */
/*************************************************************************/
#include "cst_alloc.h"
void lpc2ref(const float *lpc, float *rfc, int order)
{
/* LPC to reflection coefficients, converted from Festival */
int i,j;
float f,ai;
float *vo,*vx;
float *vn = cst_alloc(float,order);
i = order-1;
rfc[i] = ai = lpc[i];
f = 1-ai*ai;
i--;
for (j=0; j<=i; j++)
rfc[j] = (lpc[j]+((ai*lpc[i-j])))/f;
vo=rfc;
for ( ;i>0; )
{
ai=vo[i];
f = 1-ai*ai;
i--;
for (j=0; j<=i; j++)
vn[j] = (vo[j]+((ai*vo[i-j])))/f;
rfc[i]=vn[i];
vx = vn;
vn = vo;
vo = vx;
}
cst_free(vn);
}
void ref2lpc(const float *rfc, float *lpc, int order)
{
/* Here we use Christopher Longet Higgin's algorithm converted to */
/* an equivalent by awb. Its doesn't have the reverse order or */
/* negation requirement. */
float a,b;
int n,k;
for (n=0; n < order; n++)
{
lpc[n] = rfc[n];
for (k=0; 2*(k+1) <= n+1; k++)
{
a = lpc[k];
b = lpc[n-(k+1)];
lpc[k] = a-b*lpc[n];
lpc[n-(k+1)] = b-a*lpc[n];
}
}
}