   
   /******************************************************************
   
       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];
               }
           }
       }
   }
   
   
