text:    
     /******************************************************************
     
         iLBC Speech Coder ANSI-C Source Code
     
         iCBConstruct.c 
     
         Copyright (C) The Internet Society (2004). 
         All Rights Reserved.
     
     ******************************************************************/
     
     #include <math.h>
     
     #include "iLBC_define.h"
     #include "gainquant.h"
     #include "getCBvec.h"
     
     /*----------------------------------------------------------------*
      *  Convert the codebook indexes to make the search easier
      *---------------------------------------------------------------*/
     
     
     
     void index_conv_enc(
         int *index          /* (i/o) Codebook indexes */
     ){
         int k;
     
         for (k=1; k<CB_NSTAGES; k++) {
             
             if ((index[k]>=108)&&(index[k]<172)) {
                 index[k]-=64;
             } else if (index[k]>=236) {
                 index[k]-=128;
             } else {
                 /* ERROR */
             }
         }
     }
     
     void index_conv_dec(
         int *index          /* (i/o) Codebook indexes */
     ){
         int k;
     
         for (k=1; k<CB_NSTAGES; k++) {
             
             if ((index[k]>=44)&&(index[k]<108)) {
                 index[k]+=64;
             } else if ((index[k]>=108)&&(index[k]<128)) {
                 index[k]+=128;
             } else {
                 /* ERROR */
             }
         }
     }
     
     /*----------------------------------------------------------------*
      *  Construct decoded vector from codebook and gains.
      *---------------------------------------------------------------*/
     
     void iCBConstruct(
         float *decvector,   /* (o) Decoded vector */
         int *index,         /* (i) Codebook indices */
         int *gain_index,/* (i) Gain quantization indices */
         float *mem,         /* (i) Buffer for codevector construction */
         int lMem,           /* (i) Length of buffer */
         int veclen,         /* (i) Length of vector */
         int nStages         /* (i) Number of codebook stages */
     ){
         int j,k;
         float gain[CB_NSTAGES];
         float cbvec[SUBL];
     
         /* gain de-quantization */
     
         gain[0] = gaindequant(gain_index[0], 1.0, 32);
     
     
         if (nStages > 1) {
             gain[1] = gaindequant(gain_index[1], 
                 (float)fabs(gain[0]), 16);  
         }
         if (nStages > 2) {
             gain[2] = gaindequant(gain_index[2], 
                 (float)fabs(gain[1]), 8);
         }
     
         /* codebook vector construction and construction of 
         total vector */
     
         getCBvec(cbvec, mem, index[0], lMem, veclen);
         for (j=0;j<veclen;j++){
             decvector[j] = gain[0]*cbvec[j];
         }
         if (nStages > 1) {
             for (k=1; k<nStages; k++) {
                 getCBvec(cbvec, mem, index[k], lMem, veclen);
                 for (j=0;j<veclen;j++) {
                     decvector[j] += gain[k]*cbvec[j];
                 }
             }
         }
     }
     
     
  