decorr.c

来自「Reference Implementation of G.711 standa」· C语言 代码 · 共 88 行

/**************************************************************************

                (C) Copyright 1990, Motorola Inc., U.S.A.

Note:  Reproduction and use for the development of North American digital
       cellular standards or development of digital speech coding
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Systems Research Laboratories
Chicago Corporate Research and Development Center
Motorola Inc.

**************************************************************************/
/*-------------------------------------------------------------*/
/**/
/*	decorr.c -- Decorrelation of basis vectors from given vector.*/
/**/
/*-------------------------------------------------------------*/
/**/
/*	Written by: Matt Hartman*/
/**/
/*-------------------------------------------------------------*/
/*	inclusions*/
/**/
#include "vparams.h"

void            DECORR(vecPtr, basisPtr, numBasis)
  FTYPE          *vecPtr;
  FTYPE          *basisPtr;
  int             numBasis;
{
  FTYPE           gamma = 0.0;	/* Energy in the given vector (i.e. the
				 * vector from */
  /* which the basis set will be decorrelated) */
  FTYPE           psi;		/* Energy in the current basis vector */
  FTYPE           proj;		/* Gamma / psi */
  FTYPE          *bvPtr;	/* Points to the basis vector currently being */
  /* decorrelated */

  FTYPE          *tmpPtr, *tmpPtr2, *endPtr, *endPtr2;

/*	compute energy in the given vector*/
/**/
  tmpPtr = vecPtr;
  for (endPtr = tmpPtr + S_LEN; tmpPtr < endPtr; tmpPtr++)
    gamma += *tmpPtr * *tmpPtr;

/*	decorrelate each basis vector from the given vector*/
/**/
  bvPtr = basisPtr;
  for (endPtr = bvPtr + S_LEN * numBasis; bvPtr < endPtr; bvPtr += S_LEN)
  {
    /* get dot-product of basis vector and given vector */
    /**/
    psi = 0.0;
    tmpPtr = bvPtr;
    tmpPtr2 = vecPtr;
    for (endPtr2 = tmpPtr + S_LEN; tmpPtr < endPtr2; tmpPtr++)
    {
      psi += *tmpPtr * *tmpPtr2;
      tmpPtr2++;
    }

    /* subtract component of basis vector that is in the direction */
    /* of the given vector */
    /**/
    proj = psi / gamma;
    tmpPtr = bvPtr;
    tmpPtr2 = vecPtr;
    for (endPtr2 = tmpPtr + S_LEN; tmpPtr < endPtr2; tmpPtr++)
    {
      *tmpPtr = *tmpPtr - proj * *tmpPtr2;
      tmpPtr2++;
    }
  }
}