excite.c

来自「Reference Implementation of G.711 standa」· C语言 代码 · 共 100 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
       standards within the International Telecommunications Union -
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       The availability of this material does not provide any license
       by implication, estoppel, or otherwise under any patent rights
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       herein.

       Any copies or derivative works must incude this and all other
       proprietary notices.


Systems Research Laboratories
Chicago Corporate Research and Development Center
Motorola Inc.

**************************************************************************/
/*-------------------------------------------------------------*/
/**/
/*	excite.c -- Scales and combines excitations.*/
/**/
/*-------------------------------------------------------------*/
/**/
/*	Written by: Matt Hartman*/
/**/
/*-------------------------------------------------------------*/
/*	inclusions*/
/**/
#include "vparams.h"

FTYPE           EXCITE(gsp0, lag, rs00, rs11, rs22, pVecPtr, x1VecPtr, x2VecPtr, oPtr)
  int             gsp0;
  int             lag;
  FTYPE           rs00;
  FTYPE           rs11;
  FTYPE           rs22;
  FTYPE          *pVecPtr;
  FTYPE          *x1VecPtr;
  FTYPE          *x2VecPtr;
  FTYPE          *oPtr;
{
  FTYPE          *gsp0Ptr;	/* points into the GSP0 quantization table to */
  /* retrieve values needed to determine gains */
  FTYPE           beta;		/* the pitch excitation gain */
  FTYPE           gamma1;	/* the 1st codebook excitation gain */
  FTYPE           gamma2;	/* the 2nd codebook excitation gain */

  FTYPE          *tmpPtr, *endPtr;

/*	get beta, scale pitch, and put into combined excitation buffer*/
/*	(if no pitch, zero-out buffer)*/
/**/
/*	Note: factor of 0.5 applied to gains offsets the factor of 2 in*/
/*		the table entries*/
/**/
  gsp0Ptr = GSP0_TABLE + GSP0_TERMS * gsp0;
  if (lag)
    beta = 0.5 * rs00 * *gsp0Ptr;
  else
    beta = 0.0;
  tmpPtr = oPtr;
  for (endPtr = tmpPtr + S_LEN; tmpPtr < endPtr; tmpPtr++)
  {
    *tmpPtr = beta * *pVecPtr;
    pVecPtr++;
  }

/*	get gamma1, scale 1st-codebook excitation and add to combined*/
/*	excitation*/
/**/
  gsp0Ptr++;
  gamma1 = 0.5 * rs11 * *gsp0Ptr;
  tmpPtr = oPtr;
  for (endPtr = tmpPtr + S_LEN; tmpPtr < endPtr; tmpPtr++)
  {
    *tmpPtr += gamma1 * *x1VecPtr;
    x1VecPtr++;
  }

/*	get gamma2, scale 2nd-codebook excitation and add to combined*/
/*	excitation*/
/**/
  gsp0Ptr++;
  gamma2 = 0.5 * rs22 * *gsp0Ptr;
  tmpPtr = oPtr;
  for (endPtr = tmpPtr + S_LEN; tmpPtr < endPtr; tmpPtr++)
  {
    *tmpPtr += gamma2 * *x2VecPtr;
    x2VecPtr++;
  }
  return beta;
}				/* end of excite */