src/iLBC/StateConstructW.c

   1
   2    /******************************************************************
   3
   4        iLBC Speech Coder ANSI-C Source Code
   5
   6        StateConstructW.c
   7
   8        Copyright (c) 2001,
   9        Global IP Sound AB.
  10        All rights reserved.
  11
  12    ******************************************************************/
  13
  14    #include <math.h>
  15    #include <string.h>
  16
  17    #include "iLBC_define.h"
  18    #include "constants.h"
  19    #include "filter.h"
  20
  21    /*----------------------------------------------------------------*
  22     *  decoding of the start state
  23     *---------------------------------------------------------------*/
  24
  25    void StateConstructW(
  26        int idxForMax,      /* (i) 6-bit index for the quantization of
  27                                   max amplitude */
  28        int *idxVec,    /* (i) vector of quantization indexes */
  29        float *syntDenum,   /* (i) synthesis filter denumerator */
  30        float *out,         /* (o) the decoded state vector */
  31        int len             /* (i) length of a state vector */
  32    ){
  33        float maxVal, tmpbuf[LPC_FILTERORDER+2*STATE_LEN], *tmp,
  34            numerator[LPC_FILTERORDER+1];
  35        float foutbuf[LPC_FILTERORDER+2*STATE_LEN], *fout;
  36        int k,tmpi;
  37
  38        /* decoding of the maximum value */
  39
  40        maxVal = state_frgqTbl[idxForMax];
  41        maxVal = (float)pow(10,maxVal)/(float)4.5;
  42
  43        /* initialization of buffers and coefficients */
  44
  45        memset(tmpbuf, 0, LPC_FILTERORDER*sizeof(float));
  46        memset(foutbuf, 0, LPC_FILTERORDER*sizeof(float));
  47        for (k=0; k<LPC_FILTERORDER; k++) {
  48            numerator[k]=syntDenum[LPC_FILTERORDER-k];
  49        }
  50        numerator[LPC_FILTERORDER]=syntDenum[0];
  51        tmp = &tmpbuf[LPC_FILTERORDER];
  52
  53     \f
  54
  55        fout = &foutbuf[LPC_FILTERORDER];
  56
  57        /* decoding of the sample values */
  58
  59        for (k=0; k<len; k++) {
  60            tmpi = len-1-k;
  61            /* maxVal = 1/scal */
  62            tmp[k] = maxVal*state_sq3Tbl[idxVec[tmpi]];
  63        }
  64
  65        /* circular convolution with all-pass filter */
  66
  67        memset(tmp+len, 0, len*sizeof(float));
  68        ZeroPoleFilter(tmp, numerator, syntDenum, 2*len,
  69            LPC_FILTERORDER, fout);
  70        for (k=0;k<len;k++) {
  71            out[k] = fout[len-1-k]+fout[2*len-1-k];
  72        }
  73    }
  74
  75