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RFC 3951

 
 
 

Internet Low Bit Rate Codec (iLBC)

Part 5 of 6, p. 109 to 152
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prevText      Top      Up      ToC       Page 109 
A.15.  enhancer.h

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

       iLBC Speech Coder ANSI-C Source Code

       enhancer.h

       Copyright (C) The Internet Society (2004).
       All Rights Reserved.

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

   #ifndef __ENHANCER_H
   #define __ENHANCER_H

   #include "iLBC_define.h"

   float xCorrCoef(
       float *target,      /* (i) first array */
       float *regressor,   /* (i) second array */
       int subl        /* (i) dimension arrays */
   );

   int enhancerInterface(
       float *out,         /* (o) the enhanced recidual signal */
       float *in,          /* (i) the recidual signal to enhance */
       iLBC_Dec_Inst_t *iLBCdec_inst
                           /* (i/o) the decoder state structure */
   );

   #endif

A.16.  enhancer.c

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

       iLBC Speech Coder ANSI-C Source Code

       enhancer.c

       Copyright (C) The Internet Society (2004).
       All Rights Reserved.

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

   #include <math.h>
   #include <string.h>
   #include "iLBC_define.h"
   #include "constants.h"
   #include "filter.h"

   /*----------------------------------------------------------------*
    * Find index in array such that the array element with said
    * index is the element of said array closest to "value"
    * according to the squared-error criterion
    *---------------------------------------------------------------*/

   void NearestNeighbor(

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       int   *index,   /* (o) index of array element closest
                              to value */
       float *array,   /* (i) data array */
       float value,/* (i) value */
       int arlength/* (i) dimension of data array */
   ){
       int i;
       float bestcrit,crit;

       crit=array[0]-value;
       bestcrit=crit*crit;
       *index=0;
       for (i=1; i<arlength; i++) {
           crit=array[i]-value;
           crit=crit*crit;

           if (crit<bestcrit) {
               bestcrit=crit;
               *index=i;
           }
       }
   }

   /*----------------------------------------------------------------*
    * compute cross correlation between sequences
    *---------------------------------------------------------------*/

   void mycorr1(
       float* corr,    /* (o) correlation of seq1 and seq2 */
       float* seq1,    /* (i) first sequence */
       int dim1,           /* (i) dimension first seq1 */
       const float *seq2,  /* (i) second sequence */
       int dim2        /* (i) dimension seq2 */
   ){
       int i,j;

       for (i=0; i<=dim1-dim2; i++) {
           corr[i]=0.0;
           for (j=0; j<dim2; j++) {
               corr[i] += seq1[i+j] * seq2[j];
           }
       }
   }

   /*----------------------------------------------------------------*
    * upsample finite array assuming zeros outside bounds
    *---------------------------------------------------------------*/

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   void enh_upsample(
       float* useq1,   /* (o) upsampled output sequence */
       float* seq1,/* (i) unupsampled sequence */
       int dim1,       /* (i) dimension seq1 */
       int hfl         /* (i) polyphase filter length=2*hfl+1 */
   ){
       float *pu,*ps;
       int i,j,k,q,filterlength,hfl2;
       const float *polyp[ENH_UPS0]; /* pointers to
                                        polyphase columns */
       const float *pp;

       /* define pointers for filter */

       filterlength=2*hfl+1;

       if ( filterlength > dim1 ) {
           hfl2=(int) (dim1/2);
           for (j=0; j<ENH_UPS0; j++) {
               polyp[j]=polyphaserTbl+j*filterlength+hfl-hfl2;
           }
           hfl=hfl2;
           filterlength=2*hfl+1;
       }
       else {
           for (j=0; j<ENH_UPS0; j++) {
               polyp[j]=polyphaserTbl+j*filterlength;
           }
       }

       /* filtering: filter overhangs left side of sequence */

       pu=useq1;
       for (i=hfl; i<filterlength; i++) {
           for (j=0; j<ENH_UPS0; j++) {
               *pu=0.0;
               pp = polyp[j];
               ps = seq1+i;
               for (k=0; k<=i; k++) {
                   *pu += *ps-- * *pp++;
               }
               pu++;
           }
       }

       /* filtering: simple convolution=inner products */

       for (i=filterlength; i<dim1; i++) {

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           for (j=0;j<ENH_UPS0; j++){
               *pu=0.0;
               pp = polyp[j];
               ps = seq1+i;
               for (k=0; k<filterlength; k++) {
                   *pu += *ps-- * *pp++;
               }
               pu++;
           }
       }

       /* filtering: filter overhangs right side of sequence */

       for (q=1; q<=hfl; q++) {
           for (j=0; j<ENH_UPS0; j++) {
               *pu=0.0;
               pp = polyp[j]+q;
               ps = seq1+dim1-1;
               for (k=0; k<filterlength-q; k++) {
                   *pu += *ps-- * *pp++;
               }
               pu++;
           }
       }
   }


   /*----------------------------------------------------------------*
    * find segment starting near idata+estSegPos that has highest
    * correlation with idata+centerStartPos through
    * idata+centerStartPos+ENH_BLOCKL-1 segment is found at a
    * resolution of ENH_UPSO times the original of the original
    * sampling rate
    *---------------------------------------------------------------*/

   void refiner(
       float *seg,         /* (o) segment array */
       float *updStartPos, /* (o) updated start point */
       float* idata,       /* (i) original data buffer */
       int idatal,         /* (i) dimension of idata */
       int centerStartPos, /* (i) beginning center segment */
       float estSegPos,/* (i) estimated beginning other segment */
       float period    /* (i) estimated pitch period */
   ){
       int estSegPosRounded,searchSegStartPos,searchSegEndPos,corrdim;
       int tloc,tloc2,i,st,en,fraction;
       float vect[ENH_VECTL],corrVec[ENH_CORRDIM],maxv;
       float corrVecUps[ENH_CORRDIM*ENH_UPS0];

Top      Up      ToC       Page 114 
       /* defining array bounds */

       estSegPosRounded=(int)(estSegPos - 0.5);

       searchSegStartPos=estSegPosRounded-ENH_SLOP;

       if (searchSegStartPos<0) {
           searchSegStartPos=0;
       }
       searchSegEndPos=estSegPosRounded+ENH_SLOP;

       if (searchSegEndPos+ENH_BLOCKL >= idatal) {
           searchSegEndPos=idatal-ENH_BLOCKL-1;
       }
       corrdim=searchSegEndPos-searchSegStartPos+1;

       /* compute upsampled correlation (corr33) and find
          location of max */

       mycorr1(corrVec,idata+searchSegStartPos,
           corrdim+ENH_BLOCKL-1,idata+centerStartPos,ENH_BLOCKL);
       enh_upsample(corrVecUps,corrVec,corrdim,ENH_FL0);
       tloc=0; maxv=corrVecUps[0];
       for (i=1; i<ENH_UPS0*corrdim; i++) {

           if (corrVecUps[i]>maxv) {
               tloc=i;
               maxv=corrVecUps[i];
           }
       }

       /* make vector can be upsampled without ever running outside
          bounds */

       *updStartPos= (float)searchSegStartPos +
           (float)tloc/(float)ENH_UPS0+(float)1.0;
       tloc2=(int)(tloc/ENH_UPS0);

       if (tloc>tloc2*ENH_UPS0) {
           tloc2++;
       }
       st=searchSegStartPos+tloc2-ENH_FL0;

       if (st<0) {
           memset(vect,0,-st*sizeof(float));
           memcpy(&vect[-st],idata, (ENH_VECTL+st)*sizeof(float));
       }
       else {

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           en=st+ENH_VECTL;

           if (en>idatal) {
               memcpy(vect, &idata[st],
                   (ENH_VECTL-(en-idatal))*sizeof(float));
               memset(&vect[ENH_VECTL-(en-idatal)], 0,
                   (en-idatal)*sizeof(float));
           }
           else {
               memcpy(vect, &idata[st], ENH_VECTL*sizeof(float));
           }
       }
       fraction=tloc2*ENH_UPS0-tloc;

       /* compute the segment (this is actually a convolution) */

       mycorr1(seg,vect,ENH_VECTL,polyphaserTbl+(2*ENH_FL0+1)*fraction,
           2*ENH_FL0+1);
   }

   /*----------------------------------------------------------------*
    * find the smoothed output data
    *---------------------------------------------------------------*/

   void smath(
       float *odata,   /* (o) smoothed output */
       float *sseq,/* (i) said second sequence of waveforms */
       int hl,         /* (i) 2*hl+1 is sseq dimension */
       float alpha0/* (i) max smoothing energy fraction */
   ){
       int i,k;
       float w00,w10,w11,A,B,C,*psseq,err,errs;
       float surround[BLOCKL_MAX]; /* shape contributed by other than
                                      current */
       float wt[2*ENH_HL+1];       /* waveform weighting to get
                                      surround shape */
       float denom;

       /* create shape of contribution from all waveforms except the
          current one */

       for (i=1; i<=2*hl+1; i++) {
           wt[i-1] = (float)0.5*(1 - (float)cos(2*PI*i/(2*hl+2)));
       }
       wt[hl]=0.0; /* for clarity, not used */
       for (i=0; i<ENH_BLOCKL; i++) {
           surround[i]=sseq[i]*wt[0];
       }

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       for (k=1; k<hl; k++) {
           psseq=sseq+k*ENH_BLOCKL;
           for(i=0;i<ENH_BLOCKL; i++) {
               surround[i]+=psseq[i]*wt[k];
           }
       }
       for (k=hl+1; k<=2*hl; k++) {
           psseq=sseq+k*ENH_BLOCKL;
           for(i=0;i<ENH_BLOCKL; i++) {
               surround[i]+=psseq[i]*wt[k];
           }
       }

       /* compute some inner products */

       w00 = w10 = w11 = 0.0;
       psseq=sseq+hl*ENH_BLOCKL; /* current block  */
       for (i=0; i<ENH_BLOCKL;i++) {
           w00+=psseq[i]*psseq[i];
           w11+=surround[i]*surround[i];
           w10+=surround[i]*psseq[i];
       }

       if (fabs(w11) < 1.0) {
           w11=1.0;
       }
       C = (float)sqrt( w00/w11);

       /* first try enhancement without power-constraint */

       errs=0.0;
       psseq=sseq+hl*ENH_BLOCKL;
       for (i=0; i<ENH_BLOCKL; i++) {
           odata[i]=C*surround[i];
           err=psseq[i]-odata[i];
           errs+=err*err;
       }

       /* if constraint violated by first try, add constraint */

       if (errs > alpha0 * w00) {
           if ( w00 < 1) {
               w00=1;
           }
           denom = (w11*w00-w10*w10)/(w00*w00);

           if (denom > 0.0001) { /* eliminates numerical problems
                                    for if smooth */

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               A = (float)sqrt( (alpha0- alpha0*alpha0/4)/denom);
               B = -alpha0/2 - A * w10/w00;
               B = B+1;
           }
           else { /* essentially no difference between cycles;
                     smoothing not needed */
               A= 0.0;
               B= 1.0;
           }

           /* create smoothed sequence */

           psseq=sseq+hl*ENH_BLOCKL;
           for (i=0; i<ENH_BLOCKL; i++) {
               odata[i]=A*surround[i]+B*psseq[i];
           }
       }
   }

   /*----------------------------------------------------------------*
    * get the pitch-synchronous sample sequence
    *---------------------------------------------------------------*/

   void getsseq(
       float *sseq,    /* (o) the pitch-synchronous sequence */
       float *idata,       /* (i) original data */
       int idatal,         /* (i) dimension of data */
       int centerStartPos, /* (i) where current block starts */
       float *period,      /* (i) rough-pitch-period array */
       float *plocs,       /* (i) where periods of period array
                                  are taken */
       int periodl,    /* (i) dimension period array */
       int hl              /* (i) 2*hl+1 is the number of sequences */
   ){
       int i,centerEndPos,q;
       float blockStartPos[2*ENH_HL+1];
       int lagBlock[2*ENH_HL+1];
       float plocs2[ENH_PLOCSL];
       float *psseq;

       centerEndPos=centerStartPos+ENH_BLOCKL-1;

       /* present */

       NearestNeighbor(lagBlock+hl,plocs,
           (float)0.5*(centerStartPos+centerEndPos),periodl);

       blockStartPos[hl]=(float)centerStartPos;

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       psseq=sseq+ENH_BLOCKL*hl;
       memcpy(psseq, idata+centerStartPos, ENH_BLOCKL*sizeof(float));

       /* past */

       for (q=hl-1; q>=0; q--) {
           blockStartPos[q]=blockStartPos[q+1]-period[lagBlock[q+1]];
           NearestNeighbor(lagBlock+q,plocs,
               blockStartPos[q]+
               ENH_BLOCKL_HALF-period[lagBlock[q+1]], periodl);


           if (blockStartPos[q]-ENH_OVERHANG>=0) {
               refiner(sseq+q*ENH_BLOCKL, blockStartPos+q, idata,
                   idatal, centerStartPos, blockStartPos[q],
                   period[lagBlock[q+1]]);
           } else {
               psseq=sseq+q*ENH_BLOCKL;
               memset(psseq, 0, ENH_BLOCKL*sizeof(float));
           }
       }

       /* future */

       for (i=0; i<periodl; i++) {
           plocs2[i]=plocs[i]-period[i];
       }
       for (q=hl+1; q<=2*hl; q++) {
           NearestNeighbor(lagBlock+q,plocs2,
               blockStartPos[q-1]+ENH_BLOCKL_HALF,periodl);

           blockStartPos[q]=blockStartPos[q-1]+period[lagBlock[q]];
           if (blockStartPos[q]+ENH_BLOCKL+ENH_OVERHANG<idatal) {
               refiner(sseq+ENH_BLOCKL*q, blockStartPos+q, idata,
                   idatal, centerStartPos, blockStartPos[q],
                   period[lagBlock[q]]);
           }
           else {
               psseq=sseq+q*ENH_BLOCKL;
               memset(psseq, 0, ENH_BLOCKL*sizeof(float));
           }
       }
   }

   /*----------------------------------------------------------------*
    * perform enhancement on idata+centerStartPos through
    * idata+centerStartPos+ENH_BLOCKL-1
    *---------------------------------------------------------------*/

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   void enhancer(
       float *odata,       /* (o) smoothed block, dimension blockl */
       float *idata,       /* (i) data buffer used for enhancing */
       int idatal,         /* (i) dimension idata */
       int centerStartPos, /* (i) first sample current block
                                  within idata */
       float alpha0,       /* (i) max correction-energy-fraction
                                 (in [0,1]) */
       float *period,      /* (i) pitch period array */
       float *plocs,       /* (i) locations where period array
                                  values valid */
       int periodl         /* (i) dimension of period and plocs */
   ){
       float sseq[(2*ENH_HL+1)*ENH_BLOCKL];

       /* get said second sequence of segments */

       getsseq(sseq,idata,idatal,centerStartPos,period,
           plocs,periodl,ENH_HL);

       /* compute the smoothed output from said second sequence */

       smath(odata,sseq,ENH_HL,alpha0);

   }

   /*----------------------------------------------------------------*
    * cross correlation
    *---------------------------------------------------------------*/

   float xCorrCoef(
       float *target,      /* (i) first array */
       float *regressor,   /* (i) second array */
       int subl        /* (i) dimension arrays */
   ){
       int i;
       float ftmp1, ftmp2;

       ftmp1 = 0.0;
       ftmp2 = 0.0;
       for (i=0; i<subl; i++) {
           ftmp1 += target[i]*regressor[i];
           ftmp2 += regressor[i]*regressor[i];
       }

       if (ftmp1 > 0.0) {
           return (float)(ftmp1*ftmp1/ftmp2);
       }

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       else {
           return (float)0.0;
       }
   }

   /*----------------------------------------------------------------*
    * interface for enhancer
    *---------------------------------------------------------------*/

   int enhancerInterface(
       float *out,                     /* (o) enhanced signal */
       float *in,                      /* (i) unenhanced signal */
       iLBC_Dec_Inst_t *iLBCdec_inst   /* (i) buffers etc */
   ){
       float *enh_buf, *enh_period;
       int iblock, isample;
       int lag=0, ilag, i, ioffset;
       float cc, maxcc;
       float ftmp1, ftmp2;
       float *inPtr, *enh_bufPtr1, *enh_bufPtr2;
       float plc_pred[ENH_BLOCKL];

       float lpState[6], downsampled[(ENH_NBLOCKS*ENH_BLOCKL+120)/2];
       int inLen=ENH_NBLOCKS*ENH_BLOCKL+120;
       int start, plc_blockl, inlag;

       enh_buf=iLBCdec_inst->enh_buf;
       enh_period=iLBCdec_inst->enh_period;

       memmove(enh_buf, &enh_buf[iLBCdec_inst->blockl],
           (ENH_BUFL-iLBCdec_inst->blockl)*sizeof(float));

       memcpy(&enh_buf[ENH_BUFL-iLBCdec_inst->blockl], in,
           iLBCdec_inst->blockl*sizeof(float));

       if (iLBCdec_inst->mode==30)
           plc_blockl=ENH_BLOCKL;
       else
           plc_blockl=40;

       /* when 20 ms frame, move processing one block */
       ioffset=0;
       if (iLBCdec_inst->mode==20) ioffset=1;

       i=3-ioffset;
       memmove(enh_period, &enh_period[i],
           (ENH_NBLOCKS_TOT-i)*sizeof(float));

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       /* Set state information to the 6 samples right before
          the samples to be downsampled. */

       memcpy(lpState,
           enh_buf+(ENH_NBLOCKS_EXTRA+ioffset)*ENH_BLOCKL-126,
           6*sizeof(float));

       /* Down sample a factor 2 to save computations */

       DownSample(enh_buf+(ENH_NBLOCKS_EXTRA+ioffset)*ENH_BLOCKL-120,
                   lpFilt_coefsTbl, inLen-ioffset*ENH_BLOCKL,
                   lpState, downsampled);

       /* Estimate the pitch in the down sampled domain. */
       for (iblock = 0; iblock<ENH_NBLOCKS-ioffset; iblock++) {

           lag = 10;
           maxcc = xCorrCoef(downsampled+60+iblock*
               ENH_BLOCKL_HALF, downsampled+60+iblock*
               ENH_BLOCKL_HALF-lag, ENH_BLOCKL_HALF);
           for (ilag=11; ilag<60; ilag++) {
               cc = xCorrCoef(downsampled+60+iblock*
                   ENH_BLOCKL_HALF, downsampled+60+iblock*
                   ENH_BLOCKL_HALF-ilag, ENH_BLOCKL_HALF);

               if (cc > maxcc) {
                   maxcc = cc;
                   lag = ilag;
               }
           }

           /* Store the estimated lag in the non-downsampled domain */
           enh_period[iblock+ENH_NBLOCKS_EXTRA+ioffset] = (float)lag*2;


       }


       /* PLC was performed on the previous packet */
       if (iLBCdec_inst->prev_enh_pl==1) {

           inlag=(int)enh_period[ENH_NBLOCKS_EXTRA+ioffset];

           lag = inlag-1;
           maxcc = xCorrCoef(in, in+lag, plc_blockl);
           for (ilag=inlag; ilag<=inlag+1; ilag++) {
               cc = xCorrCoef(in, in+ilag, plc_blockl);

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               if (cc > maxcc) {
                   maxcc = cc;
                   lag = ilag;
               }
           }

           enh_period[ENH_NBLOCKS_EXTRA+ioffset-1]=(float)lag;

           /* compute new concealed residual for the old lookahead,
              mix the forward PLC with a backward PLC from
              the new frame */

           inPtr=&in[lag-1];

           enh_bufPtr1=&plc_pred[plc_blockl-1];

           if (lag>plc_blockl) {
               start=plc_blockl;
           } else {
               start=lag;
           }

           for (isample = start; isample>0; isample--) {
               *enh_bufPtr1-- = *inPtr--;
           }

           enh_bufPtr2=&enh_buf[ENH_BUFL-1-iLBCdec_inst->blockl];
           for (isample = (plc_blockl-1-lag); isample>=0; isample--) {
               *enh_bufPtr1-- = *enh_bufPtr2--;
           }

           /* limit energy change */
           ftmp2=0.0;
           ftmp1=0.0;
           for (i=0;i<plc_blockl;i++) {
               ftmp2+=enh_buf[ENH_BUFL-1-iLBCdec_inst->blockl-i]*
                   enh_buf[ENH_BUFL-1-iLBCdec_inst->blockl-i];
               ftmp1+=plc_pred[i]*plc_pred[i];
           }
           ftmp1=(float)sqrt(ftmp1/(float)plc_blockl);
           ftmp2=(float)sqrt(ftmp2/(float)plc_blockl);
           if (ftmp1>(float)2.0*ftmp2 && ftmp1>0.0) {
               for (i=0;i<plc_blockl-10;i++) {
                   plc_pred[i]*=(float)2.0*ftmp2/ftmp1;
               }
               for (i=plc_blockl-10;i<plc_blockl;i++) {
                   plc_pred[i]*=(float)(i-plc_blockl+10)*
                       ((float)1.0-(float)2.0*ftmp2/ftmp1)/(float)(10)+

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                       (float)2.0*ftmp2/ftmp1;
               }
           }

           enh_bufPtr1=&enh_buf[ENH_BUFL-1-iLBCdec_inst->blockl];
           for (i=0; i<plc_blockl; i++) {
               ftmp1 = (float) (i+1) / (float) (plc_blockl+1);
               *enh_bufPtr1 *= ftmp1;
               *enh_bufPtr1 += ((float)1.0-ftmp1)*
                                   plc_pred[plc_blockl-1-i];
               enh_bufPtr1--;
           }
       }

       if (iLBCdec_inst->mode==20) {
           /* Enhancer with 40 samples delay */
           for (iblock = 0; iblock<2; iblock++) {
               enhancer(out+iblock*ENH_BLOCKL, enh_buf,
                   ENH_BUFL, (5+iblock)*ENH_BLOCKL+40,
                   ENH_ALPHA0, enh_period, enh_plocsTbl,
                       ENH_NBLOCKS_TOT);
           }
       } else if (iLBCdec_inst->mode==30) {
           /* Enhancer with 80 samples delay */
           for (iblock = 0; iblock<3; iblock++) {
               enhancer(out+iblock*ENH_BLOCKL, enh_buf,
                   ENH_BUFL, (4+iblock)*ENH_BLOCKL,
                   ENH_ALPHA0, enh_period, enh_plocsTbl,
                       ENH_NBLOCKS_TOT);
           }
       }

       return (lag*2);
   }

A.17.  filter.h

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

       iLBC Speech Coder ANSI-C Source Code

       filter.h

       Copyright (C) The Internet Society (2004).
       All Rights Reserved.

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

Top      Up      ToC       Page 124 
   #ifndef __iLBC_FILTER_H
   #define __iLBC_FILTER_H

   void AllPoleFilter(
       float *InOut,   /* (i/o) on entrance InOut[-orderCoef] to
                              InOut[-1] contain the state of the
                              filter (delayed samples). InOut[0] to
                              InOut[lengthInOut-1] contain the filter
                              input, on en exit InOut[-orderCoef] to
                              InOut[-1] is unchanged and InOut[0] to
                              InOut[lengthInOut-1] contain filtered
                              samples */
       float *Coef,/* (i) filter coefficients, Coef[0] is assumed
                              to be 1.0 */
       int lengthInOut,/* (i) number of input/output samples */
       int orderCoef   /* (i) number of filter coefficients */
   );

   void AllZeroFilter(
       float *In,      /* (i) In[0] to In[lengthInOut-1] contain
                              filter input samples */
       float *Coef,/* (i) filter coefficients (Coef[0] is assumed
                              to be 1.0) */
       int lengthInOut,/* (i) number of input/output samples */
       int orderCoef,  /* (i) number of filter coefficients */
       float *Out      /* (i/o) on entrance Out[-orderCoef] to Out[-1]
                              contain the filter state, on exit Out[0]
                              to Out[lengthInOut-1] contain filtered
                              samples */
   );

   void ZeroPoleFilter(
       float *In,      /* (i) In[0] to In[lengthInOut-1] contain filter
                              input samples In[-orderCoef] to In[-1]
                              contain state of all-zero section */
       float *ZeroCoef,/* (i) filter coefficients for all-zero
                              section (ZeroCoef[0] is assumed to
                              be 1.0) */
       float *PoleCoef,/* (i) filter coefficients for all-pole section
                              (ZeroCoef[0] is assumed to be 1.0) */
       int lengthInOut,/* (i) number of input/output samples */
       int orderCoef,  /* (i) number of filter coefficients */
       float *Out      /* (i/o) on entrance Out[-orderCoef] to Out[-1]
                              contain state of all-pole section. On
                              exit Out[0] to Out[lengthInOut-1]
                              contain filtered samples */
   );

Top      Up      ToC       Page 125 
   void DownSample (
       float  *In,     /* (i) input samples */
       float  *Coef,   /* (i) filter coefficients */
       int lengthIn,   /* (i) number of input samples */
       float  *state,  /* (i) filter state */
       float  *Out     /* (o) downsampled output */
   );

   #endif

A.18.  filter.c

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

       iLBC Speech Coder ANSI-C Source Code

       filter.c

       Copyright (C) The Internet Society (2004).
       All Rights Reserved.

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

   #include "iLBC_define.h"

   /*----------------------------------------------------------------*
    *  all-pole filter
    *---------------------------------------------------------------*/

   void AllPoleFilter(
       float *InOut,   /* (i/o) on entrance InOut[-orderCoef] to
                              InOut[-1] contain the state of the
                              filter (delayed samples). InOut[0] to
                              InOut[lengthInOut-1] contain the filter
                              input, on en exit InOut[-orderCoef] to
                              InOut[-1] is unchanged and InOut[0] to
                              InOut[lengthInOut-1] contain filtered
                              samples */
       float *Coef,/* (i) filter coefficients, Coef[0] is assumed
                              to be 1.0 */
       int lengthInOut,/* (i) number of input/output samples */
       int orderCoef   /* (i) number of filter coefficients */
   ){
       int n,k;

       for(n=0;n<lengthInOut;n++){
           for(k=1;k<=orderCoef;k++){
               *InOut -= Coef[k]*InOut[-k];

Top      Up      ToC       Page 126 
           }
           InOut++;
       }
   }

   /*----------------------------------------------------------------*
    *  all-zero filter
    *---------------------------------------------------------------*/

   void AllZeroFilter(
       float *In,      /* (i) In[0] to In[lengthInOut-1] contain
                              filter input samples */
       float *Coef,/* (i) filter coefficients (Coef[0] is assumed
                              to be 1.0) */
       int lengthInOut,/* (i) number of input/output samples */
       int orderCoef,  /* (i) number of filter coefficients */
       float *Out      /* (i/o) on entrance Out[-orderCoef] to Out[-1]
                              contain the filter state, on exit Out[0]
                              to Out[lengthInOut-1] contain filtered
                              samples */
   ){
       int n,k;

       for(n=0;n<lengthInOut;n++){
           *Out = Coef[0]*In[0];
           for(k=1;k<=orderCoef;k++){
               *Out += Coef[k]*In[-k];
           }
           Out++;
           In++;
       }
   }

   /*----------------------------------------------------------------*
    *  pole-zero filter
    *---------------------------------------------------------------*/

   void ZeroPoleFilter(
       float *In,      /* (i) In[0] to In[lengthInOut-1] contain
                              filter input samples In[-orderCoef] to
                              In[-1] contain state of all-zero
                              section */
       float *ZeroCoef,/* (i) filter coefficients for all-zero
                              section (ZeroCoef[0] is assumed to
                              be 1.0) */
       float *PoleCoef,/* (i) filter coefficients for all-pole section
                              (ZeroCoef[0] is assumed to be 1.0) */
       int lengthInOut,/* (i) number of input/output samples */

Top      Up      ToC       Page 127 
       int orderCoef,  /* (i) number of filter coefficients */
       float *Out      /* (i/o) on entrance Out[-orderCoef] to Out[-1]
                              contain state of all-pole section. On
                              exit Out[0] to Out[lengthInOut-1]
                              contain filtered samples */
   ){
       AllZeroFilter(In,ZeroCoef,lengthInOut,orderCoef,Out);
       AllPoleFilter(Out,PoleCoef,lengthInOut,orderCoef);
   }

   /*----------------------------------------------------------------*
    * downsample (LP filter and decimation)
    *---------------------------------------------------------------*/

   void DownSample (
       float  *In,     /* (i) input samples */
       float  *Coef,   /* (i) filter coefficients */
       int lengthIn,   /* (i) number of input samples */
       float  *state,  /* (i) filter state */
       float  *Out     /* (o) downsampled output */
   ){
       float   o;
       float *Out_ptr = Out;
       float *Coef_ptr, *In_ptr;
       float *state_ptr;
       int i, j, stop;

       /* LP filter and decimate at the same time */

       for (i = DELAY_DS; i < lengthIn; i+=FACTOR_DS)
       {
           Coef_ptr = &Coef[0];
           In_ptr = &In[i];
           state_ptr = &state[FILTERORDER_DS-2];

           o = (float)0.0;

           stop = (i < FILTERORDER_DS) ? i + 1 : FILTERORDER_DS;

           for (j = 0; j < stop; j++)
           {
               o += *Coef_ptr++ * (*In_ptr--);
           }
           for (j = i + 1; j < FILTERORDER_DS; j++)
           {
               o += *Coef_ptr++ * (*state_ptr--);
           }

Top      Up      ToC       Page 128 
           *Out_ptr++ = o;
       }

       /* Get the last part (use zeros as input for the future) */

       for (i=(lengthIn+FACTOR_DS); i<(lengthIn+DELAY_DS);
               i+=FACTOR_DS) {

           o=(float)0.0;

           if (i<lengthIn) {
               Coef_ptr = &Coef[0];
               In_ptr = &In[i];
               for (j=0; j<FILTERORDER_DS; j++) {
                       o += *Coef_ptr++ * (*Out_ptr--);
               }
           } else {
               Coef_ptr = &Coef[i-lengthIn];
               In_ptr = &In[lengthIn-1];
               for (j=0; j<FILTERORDER_DS-(i-lengthIn); j++) {
                       o += *Coef_ptr++ * (*In_ptr--);
               }
           }
           *Out_ptr++ = o;
       }
   }

A.19.  FrameClassify.h

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

       iLBC Speech Coder ANSI-C Source Code

       FrameClassify.h

       Copyright (C) The Internet Society (2004).
       All Rights Reserved.

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

   #ifndef __iLBC_FRAMECLASSIFY_H
   #define __iLBC_FRAMECLASSIFY_H

   int FrameClassify(      /* index to the max-energy sub-frame */
       iLBC_Enc_Inst_t *iLBCenc_inst,
                           /* (i/o) the encoder state structure */
       float *residual     /* (i) lpc residual signal */
   );

Top      Up      ToC       Page 129 
   #endif

A.20.  FrameClassify.c

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

       iLBC Speech Coder ANSI-C Source Code

       FrameClassify.c

       Copyright (C) The Internet Society (2004).
       All Rights Reserved.

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

   #include "iLBC_define.h"

   /*---------------------------------------------------------------*
    *  Classification of subframes to localize start state
    *--------------------------------------------------------------*/

   int FrameClassify(      /* index to the max-energy sub-frame */
       iLBC_Enc_Inst_t *iLBCenc_inst,
                           /* (i/o) the encoder state structure */
       float *residual     /* (i) lpc residual signal */
   ) {
       float max_ssqEn, fssqEn[NSUB_MAX], bssqEn[NSUB_MAX], *pp;
       int n, l, max_ssqEn_n;
       const float ssqEn_win[NSUB_MAX-1]={(float)0.8,(float)0.9,
           (float)1.0,(float)0.9,(float)0.8};
       const float sampEn_win[5]={(float)1.0/(float)6.0,
           (float)2.0/(float)6.0, (float)3.0/(float)6.0,
           (float)4.0/(float)6.0, (float)5.0/(float)6.0};

       /* init the front and back energies to zero */

       memset(fssqEn, 0, NSUB_MAX*sizeof(float));
       memset(bssqEn, 0, NSUB_MAX*sizeof(float));

       /* Calculate front of first seqence */

       n=0;
       pp=residual;
       for (l=0; l<5; l++) {
           fssqEn[n] += sampEn_win[l] * (*pp) * (*pp);
           pp++;
       }
       for (l=5; l<SUBL; l++) {

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           fssqEn[n] += (*pp) * (*pp);
           pp++;
       }

       /* Calculate front and back of all middle sequences */

       for (n=1; n<iLBCenc_inst->nsub-1; n++) {
           pp=residual+n*SUBL;
           for (l=0; l<5; l++) {
               fssqEn[n] += sampEn_win[l] * (*pp) * (*pp);
               bssqEn[n] += (*pp) * (*pp);
               pp++;
           }
           for (l=5; l<SUBL-5; l++) {
               fssqEn[n] += (*pp) * (*pp);
               bssqEn[n] += (*pp) * (*pp);
               pp++;
           }
           for (l=SUBL-5; l<SUBL; l++) {
               fssqEn[n] += (*pp) * (*pp);
               bssqEn[n] += sampEn_win[SUBL-l-1] * (*pp) * (*pp);
               pp++;
           }
       }

       /* Calculate back of last seqence */

       n=iLBCenc_inst->nsub-1;
       pp=residual+n*SUBL;
       for (l=0; l<SUBL-5; l++) {
           bssqEn[n] += (*pp) * (*pp);
           pp++;
       }
       for (l=SUBL-5; l<SUBL; l++) {
           bssqEn[n] += sampEn_win[SUBL-l-1] * (*pp) * (*pp);
           pp++;
       }

       /* find the index to the weighted 80 sample with
          most energy */

       if (iLBCenc_inst->mode==20) l=1;
       else                        l=0;

       max_ssqEn=(fssqEn[0]+bssqEn[1])*ssqEn_win[l];
       max_ssqEn_n=1;
       for (n=2; n<iLBCenc_inst->nsub; n++) {

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           l++;
           if ((fssqEn[n-1]+bssqEn[n])*ssqEn_win[l] > max_ssqEn) {
               max_ssqEn=(fssqEn[n-1]+bssqEn[n]) *
                               ssqEn_win[l];
               max_ssqEn_n=n;
           }
       }

       return max_ssqEn_n;
   }

A.21.  gainquant.h

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

       iLBC Speech Coder ANSI-C Source Code

       gainquant.h

       Copyright (C) The Internet Society (2004).
       All Rights Reserved.

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

   #ifndef __iLBC_GAINQUANT_H
   #define __iLBC_GAINQUANT_H

   float gainquant(/* (o) quantized gain value */
       float in,       /* (i) gain value */
       float maxIn,/* (i) maximum of gain value */
       int cblen,      /* (i) number of quantization indices */
       int *index      /* (o) quantization index */
   );

   float gaindequant(  /* (o) quantized gain value */
       int index,      /* (i) quantization index */
       float maxIn,/* (i) maximum of unquantized gain */
       int cblen       /* (i) number of quantization indices */
   );

   #endif

A.22.  gainquant.c

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

       iLBC Speech Coder ANSI-C Source Code

Top      Up      ToC       Page 132 
       gainquant.c

       Copyright (C) The Internet Society (2004).
       All Rights Reserved.

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

   #include <string.h>
   #include <math.h>
   #include "constants.h"
   #include "filter.h"

   /*----------------------------------------------------------------*
    *  quantizer for the gain in the gain-shape coding of residual
    *---------------------------------------------------------------*/

   float gainquant(/* (o) quantized gain value */
       float in,       /* (i) gain value */
       float maxIn,/* (i) maximum of gain value */
       int cblen,      /* (i) number of quantization indices */
       int *index      /* (o) quantization index */
   ){
       int i, tindex;
       float minmeasure,measure, *cb, scale;

       /* ensure a lower bound on the scaling factor */

       scale=maxIn;

       if (scale<0.1) {
           scale=(float)0.1;
       }

       /* select the quantization table */

       if (cblen == 8) {
           cb = gain_sq3Tbl;
       } else if (cblen == 16) {
           cb = gain_sq4Tbl;
       } else  {
           cb = gain_sq5Tbl;
       }

       /* select the best index in the quantization table */

       minmeasure=10000000.0;
       tindex=0;
       for (i=0; i<cblen; i++) {

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           measure=(in-scale*cb[i])*(in-scale*cb[i]);

           if (measure<minmeasure) {
               tindex=i;
               minmeasure=measure;
           }
       }
       *index=tindex;

       /* return the quantized value */

       return scale*cb[tindex];
   }

   /*----------------------------------------------------------------*
    *  decoder for quantized gains in the gain-shape coding of
    *  residual
    *---------------------------------------------------------------*/

   float gaindequant(  /* (o) quantized gain value */
       int index,      /* (i) quantization index */
       float maxIn,/* (i) maximum of unquantized gain */
       int cblen       /* (i) number of quantization indices */
   ){
       float scale;

       /* obtain correct scale factor */

       scale=(float)fabs(maxIn);

       if (scale<0.1) {
           scale=(float)0.1;
       }

       /* select the quantization table and return the decoded value */

       if (cblen==8) {
           return scale*gain_sq3Tbl[index];
       } else if (cblen==16) {
           return scale*gain_sq4Tbl[index];
       }
       else if (cblen==32) {
           return scale*gain_sq5Tbl[index];
       }

       return 0.0;
   }

Top      Up      ToC       Page 134 
A.23.  getCBvec.h

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

       iLBC Speech Coder ANSI-C Source Code

       getCBvec.h

       Copyright (C) The Internet Society (2004).
       All Rights Reserved.

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

   #ifndef __iLBC_GETCBVEC_H
   #define __iLBC_GETCBVEC_H

   void getCBvec(
       float *cbvec,   /* (o) Constructed codebook vector */
       float *mem,     /* (i) Codebook buffer */
       int index,      /* (i) Codebook index */
       int lMem,       /* (i) Length of codebook buffer */
       int cbveclen/* (i) Codebook vector length */
   );

   #endif

A.24.  getCBvec.c

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

       iLBC Speech Coder ANSI-C Source Code

       getCBvec.c

       Copyright (C) The Internet Society (2004).
       All Rights Reserved.

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

   #include "iLBC_define.h"
   #include "constants.h"
   #include <string.h>

   /*----------------------------------------------------------------*
    *  Construct codebook vector for given index.
    *---------------------------------------------------------------*/

   void getCBvec(

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       float *cbvec,   /* (o) Constructed codebook vector */
       float *mem,     /* (i) Codebook buffer */
       int index,      /* (i) Codebook index */
       int lMem,       /* (i) Length of codebook buffer */
       int cbveclen/* (i) Codebook vector length */
   ){
       int j, k, n, memInd, sFilt;
       float tmpbuf[CB_MEML];
       int base_size;
       int ilow, ihigh;
       float alfa, alfa1;

       /* Determine size of codebook sections */

       base_size=lMem-cbveclen+1;

       if (cbveclen==SUBL) {
           base_size+=cbveclen/2;
       }

       /* No filter -> First codebook section */

       if (index<lMem-cbveclen+1) {

           /* first non-interpolated vectors */

           k=index+cbveclen;
           /* get vector */
           memcpy(cbvec, mem+lMem-k, cbveclen*sizeof(float));

       } else if (index < base_size) {

           k=2*(index-(lMem-cbveclen+1))+cbveclen;

           ihigh=k/2;
           ilow=ihigh-5;

           /* Copy first noninterpolated part */

           memcpy(cbvec, mem+lMem-k/2, ilow*sizeof(float));

           /* interpolation */

           alfa1=(float)0.2;
           alfa=0.0;
           for (j=ilow; j<ihigh; j++) {
               cbvec[j]=((float)1.0-alfa)*mem[lMem-k/2+j]+
                   alfa*mem[lMem-k+j];

Top      Up      ToC       Page 136 
               alfa+=alfa1;
           }

           /* Copy second noninterpolated part */

           memcpy(cbvec+ihigh, mem+lMem-k+ihigh,
               (cbveclen-ihigh)*sizeof(float));

       }

       /* Higher codebook section based on filtering */

       else {

           /* first non-interpolated vectors */

           if (index-base_size<lMem-cbveclen+1) {
               float tempbuff2[CB_MEML+CB_FILTERLEN+1];
               float *pos;
               float *pp, *pp1;

               memset(tempbuff2, 0,
                   CB_HALFFILTERLEN*sizeof(float));
               memcpy(&tempbuff2[CB_HALFFILTERLEN], mem,
                   lMem*sizeof(float));
               memset(&tempbuff2[lMem+CB_HALFFILTERLEN], 0,
                   (CB_HALFFILTERLEN+1)*sizeof(float));

               k=index-base_size+cbveclen;
               sFilt=lMem-k;
               memInd=sFilt+1-CB_HALFFILTERLEN;

               /* do filtering */
               pos=cbvec;
               memset(pos, 0, cbveclen*sizeof(float));
               for (n=0; n<cbveclen; n++) {
                   pp=&tempbuff2[memInd+n+CB_HALFFILTERLEN];
                   pp1=&cbfiltersTbl[CB_FILTERLEN-1];
                   for (j=0; j<CB_FILTERLEN; j++) {
                       (*pos)+=(*pp++)*(*pp1--);
                   }
                   pos++;
               }
           }

           /* interpolated vectors */

           else {

Top      Up      ToC       Page 137 
               float tempbuff2[CB_MEML+CB_FILTERLEN+1];

               float *pos;
               float *pp, *pp1;
               int i;

               memset(tempbuff2, 0,
                   CB_HALFFILTERLEN*sizeof(float));
               memcpy(&tempbuff2[CB_HALFFILTERLEN], mem,
                   lMem*sizeof(float));
               memset(&tempbuff2[lMem+CB_HALFFILTERLEN], 0,
                   (CB_HALFFILTERLEN+1)*sizeof(float));

               k=2*(index-base_size-
                   (lMem-cbveclen+1))+cbveclen;
               sFilt=lMem-k;
               memInd=sFilt+1-CB_HALFFILTERLEN;

               /* do filtering */
               pos=&tmpbuf[sFilt];
               memset(pos, 0, k*sizeof(float));
               for (i=0; i<k; i++) {
                   pp=&tempbuff2[memInd+i+CB_HALFFILTERLEN];
                   pp1=&cbfiltersTbl[CB_FILTERLEN-1];
                   for (j=0; j<CB_FILTERLEN; j++) {
                       (*pos)+=(*pp++)*(*pp1--);
                   }
                   pos++;
               }

               ihigh=k/2;
               ilow=ihigh-5;

               /* Copy first noninterpolated part */

               memcpy(cbvec, tmpbuf+lMem-k/2,
                   ilow*sizeof(float));

               /* interpolation */

               alfa1=(float)0.2;
               alfa=0.0;
               for (j=ilow; j<ihigh; j++) {
                   cbvec[j]=((float)1.0-alfa)*
                       tmpbuf[lMem-k/2+j]+alfa*tmpbuf[lMem-k+j];
                   alfa+=alfa1;
               }

Top      Up      ToC       Page 138 
               /* Copy second noninterpolated part */

               memcpy(cbvec+ihigh, tmpbuf+lMem-k+ihigh,
                   (cbveclen-ihigh)*sizeof(float));
           }
       }
   }

A.25.  helpfun.h

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

       iLBC Speech Coder ANSI-C Source Code

       helpfun.h

       Copyright (C) The Internet Society (2004).
       All Rights Reserved.

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

   #ifndef __iLBC_HELPFUN_H
   #define __iLBC_HELPFUN_H

   void autocorr(
       float *r,       /* (o) autocorrelation vector */
       const float *x, /* (i) data vector */
       int N,          /* (i) length of data vector */
       int order       /* largest lag for calculated
                          autocorrelations */
   );

   void window(
       float *z,       /* (o) the windowed data */
       const float *x, /* (i) the original data vector */
       const float *y, /* (i) the window */
       int N           /* (i) length of all vectors */
   );

   void levdurb(
       float *a,       /* (o) lpc coefficient vector starting
                              with 1.0 */
       float *k,       /* (o) reflection coefficients */
       float *r,       /* (i) autocorrelation vector */
       int order       /* (i) order of lpc filter */
   );

   void interpolate(

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       float *out,     /* (o) the interpolated vector */
       float *in1,     /* (i) the first vector for the
                              interpolation */
       float *in2,     /* (i) the second vector for the
                              interpolation */
       float coef,     /* (i) interpolation weights */
       int length      /* (i) length of all vectors */
   );

   void bwexpand(
       float *out,     /* (o) the bandwidth expanded lpc
                              coefficients */
       float *in,      /* (i) the lpc coefficients before bandwidth
                              expansion */
       float coef,     /* (i) the bandwidth expansion factor */
       int length      /* (i) the length of lpc coefficient vectors */
   );

   void vq(
       float *Xq,      /* (o) the quantized vector */
       int *index,     /* (o) the quantization index */
       const float *CB,/* (i) the vector quantization codebook */
       float *X,       /* (i) the vector to quantize */
       int n_cb,       /* (i) the number of vectors in the codebook */
       int dim         /* (i) the dimension of all vectors */
   );

   void SplitVQ(
       float *qX,      /* (o) the quantized vector */
       int *index,     /* (o) a vector of indexes for all vector
                              codebooks in the split */
       float *X,       /* (i) the vector to quantize */
       const float *CB,/* (i) the quantizer codebook */
       int nsplit,     /* the number of vector splits */
       const int *dim, /* the dimension of X and qX */
       const int *cbsize /* the number of vectors in the codebook */
   );


   void sort_sq(
       float *xq,      /* (o) the quantized value */
       int *index,     /* (o) the quantization index */
       float x,    /* (i) the value to quantize */
       const float *cb,/* (i) the quantization codebook */
       int cb_size     /* (i) the size of the quantization codebook */
   );

   int LSF_check(      /* (o) 1 for stable lsf vectors and 0 for

Top      Up      ToC       Page 140 
                              nonstable ones */
       float *lsf,     /* (i) a table of lsf vectors */
       int dim,    /* (i) the dimension of each lsf vector */
       int NoAn    /* (i) the number of lsf vectors in the
                              table */
   );

   #endif

A.26.  helpfun.c

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

       iLBC Speech Coder ANSI-C Source Code

       helpfun.c

       Copyright (C) The Internet Society (2004).
       All Rights Reserved.

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

   #include <math.h>

   #include "iLBC_define.h"
   #include "constants.h"

   /*----------------------------------------------------------------*
    *  calculation of auto correlation
    *---------------------------------------------------------------*/

   void autocorr(
       float *r,       /* (o) autocorrelation vector */
       const float *x, /* (i) data vector */
       int N,          /* (i) length of data vector */
       int order       /* largest lag for calculated
                          autocorrelations */
   ){
       int     lag, n;
       float   sum;

       for (lag = 0; lag <= order; lag++) {
           sum = 0;
           for (n = 0; n < N - lag; n++) {
               sum += x[n] * x[n+lag];
           }
           r[lag] = sum;
       }

Top      Up      ToC       Page 141 
   }

   /*----------------------------------------------------------------*
    *  window multiplication
    *---------------------------------------------------------------*/

   void window(
       float *z,       /* (o) the windowed data */
       const float *x, /* (i) the original data vector */
       const float *y, /* (i) the window */
       int N           /* (i) length of all vectors */
   ){
       int     i;

       for (i = 0; i < N; i++) {
           z[i] = x[i] * y[i];
       }
   }

   /*----------------------------------------------------------------*
    *  levinson-durbin solution for lpc coefficients
    *---------------------------------------------------------------*/

   void levdurb(
       float *a,       /* (o) lpc coefficient vector starting
                              with 1.0 */
       float *k,       /* (o) reflection coefficients */
       float *r,       /* (i) autocorrelation vector */
       int order       /* (i) order of lpc filter */
   ){
       float  sum, alpha;
       int     m, m_h, i;

       a[0] = 1.0;

       if (r[0] < EPS) { /* if r[0] <= 0, set LPC coeff. to zero */
           for (i = 0; i < order; i++) {
               k[i] = 0;
               a[i+1] = 0;
           }
       } else {
           a[1] = k[0] = -r[1]/r[0];
           alpha = r[0] + r[1] * k[0];
           for (m = 1; m < order; m++){
               sum = r[m + 1];
               for (i = 0; i < m; i++){
                   sum += a[i+1] * r[m - i];
               }

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               k[m] = -sum / alpha;
               alpha += k[m] * sum;
               m_h = (m + 1) >> 1;
               for (i = 0; i < m_h; i++){
                   sum = a[i+1] + k[m] * a[m - i];
                   a[m - i] += k[m] * a[i+1];
                   a[i+1] = sum;
               }
               a[m+1] = k[m];
           }
       }
   }

   /*----------------------------------------------------------------*
    *  interpolation between vectors
    *---------------------------------------------------------------*/

   void interpolate(
       float *out,      /* (o) the interpolated vector */
       float *in1,     /* (i) the first vector for the
                              interpolation */
       float *in2,     /* (i) the second vector for the
                              interpolation */
       float coef,      /* (i) interpolation weights */
       int length      /* (i) length of all vectors */
   ){
       int i;
       float invcoef;

       invcoef = (float)1.0 - coef;
       for (i = 0; i < length; i++) {
           out[i] = coef * in1[i] + invcoef * in2[i];
       }
   }

   /*----------------------------------------------------------------*
    *  lpc bandwidth expansion
    *---------------------------------------------------------------*/

   void bwexpand(
       float *out,      /* (o) the bandwidth expanded lpc
                              coefficients */
       float *in,      /* (i) the lpc coefficients before bandwidth
                              expansion */
       float coef,     /* (i) the bandwidth expansion factor */
       int length      /* (i) the length of lpc coefficient vectors */
   ){
       int i;

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       float  chirp;

       chirp = coef;

       out[0] = in[0];
       for (i = 1; i < length; i++) {
           out[i] = chirp * in[i];
           chirp *= coef;
       }
   }

   /*----------------------------------------------------------------*
    *  vector quantization
    *---------------------------------------------------------------*/

   void vq(
       float *Xq,      /* (o) the quantized vector */
       int *index,     /* (o) the quantization index */
       const float *CB,/* (i) the vector quantization codebook */
       float *X,       /* (i) the vector to quantize */
       int n_cb,       /* (i) the number of vectors in the codebook */
       int dim         /* (i) the dimension of all vectors */
   ){
       int     i, j;
       int     pos, minindex;
       float   dist, tmp, mindist;

       pos = 0;
       mindist = FLOAT_MAX;
       minindex = 0;
       for (j = 0; j < n_cb; j++) {
           dist = X[0] - CB[pos];
           dist *= dist;
           for (i = 1; i < dim; i++) {
               tmp = X[i] - CB[pos + i];
               dist += tmp*tmp;
           }

           if (dist < mindist) {
               mindist = dist;
               minindex = j;
           }
           pos += dim;
       }
       for (i = 0; i < dim; i++) {
           Xq[i] = CB[minindex*dim + i];
       }
       *index = minindex;

Top      Up      ToC       Page 144 
   }

   /*----------------------------------------------------------------*
    *  split vector quantization
    *---------------------------------------------------------------*/

   void SplitVQ(
       float *qX,      /* (o) the quantized vector */
       int *index,     /* (o) a vector of indexes for all vector
                              codebooks in the split */
       float *X,       /* (i) the vector to quantize */
       const float *CB,/* (i) the quantizer codebook */
       int nsplit,     /* the number of vector splits */
       const int *dim, /* the dimension of X and qX */
       const int *cbsize /* the number of vectors in the codebook */
   ){
       int    cb_pos, X_pos, i;

       cb_pos = 0;
       X_pos= 0;
       for (i = 0; i < nsplit; i++) {
           vq(qX + X_pos, index + i, CB + cb_pos, X + X_pos,
               cbsize[i], dim[i]);
           X_pos += dim[i];
           cb_pos += dim[i] * cbsize[i];
       }
   }

   /*----------------------------------------------------------------*
    *  scalar quantization
    *---------------------------------------------------------------*/

   void sort_sq(
       float *xq,      /* (o) the quantized value */
       int *index,     /* (o) the quantization index */
       float x,    /* (i) the value to quantize */
       const float *cb,/* (i) the quantization codebook */
       int cb_size      /* (i) the size of the quantization codebook */
   ){
       int i;

       if (x <= cb[0]) {
           *index = 0;
           *xq = cb[0];
       } else {
           i = 0;
           while ((x > cb[i]) && i < cb_size - 1) {
               i++;

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           }

           if (x > ((cb[i] + cb[i - 1])/2)) {
               *index = i;
               *xq = cb[i];
           } else {
               *index = i - 1;
               *xq = cb[i - 1];
           }
       }
   }

   /*----------------------------------------------------------------*
    *  check for stability of lsf coefficients
    *---------------------------------------------------------------*/

   int LSF_check(    /* (o) 1 for stable lsf vectors and 0 for
                              nonstable ones */
       float *lsf,     /* (i) a table of lsf vectors */
       int dim,    /* (i) the dimension of each lsf vector */
       int NoAn    /* (i) the number of lsf vectors in the
                              table */
   ){
       int k,n,m, Nit=2, change=0,pos;
       float tmp;
       static float eps=(float)0.039; /* 50 Hz */
       static float eps2=(float)0.0195;
       static float maxlsf=(float)3.14; /* 4000 Hz */
       static float minlsf=(float)0.01; /* 0 Hz */

       /* LSF separation check*/

       for (n=0; n<Nit; n++) { /* Run through a couple of times */
           for (m=0; m<NoAn; m++) { /* Number of analyses per frame */
               for (k=0; k<(dim-1); k++) {
                   pos=m*dim+k;

                   if ((lsf[pos+1]-lsf[pos])<eps) {

                       if (lsf[pos+1]<lsf[pos]) {
                           tmp=lsf[pos+1];
                           lsf[pos+1]= lsf[pos]+eps2;
                           lsf[pos]= lsf[pos+1]-eps2;
                       } else {
                           lsf[pos]-=eps2;
                           lsf[pos+1]+=eps2;
                       }
                       change=1;

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                   }

                   if (lsf[pos]<minlsf) {
                       lsf[pos]=minlsf;
                       change=1;
                   }

                   if (lsf[pos]>maxlsf) {
                       lsf[pos]=maxlsf;
                       change=1;
                   }
               }
           }
       }

       return change;
   }

A.27.  hpInput.h

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

       iLBC Speech Coder ANSI-C Source Code

       hpInput.h

       Copyright (C) The Internet Society (2004).
       All Rights Reserved.

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

   #ifndef __iLBC_HPINPUT_H
   #define __iLBC_HPINPUT_H

   void hpInput(
       float *In,  /* (i) vector to filter */
       int len,    /* (i) length of vector to filter */
       float *Out, /* (o) the resulting filtered vector */
       float *mem  /* (i/o) the filter state */
   );

   #endif

A.28.  hpInput.c

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

       iLBC Speech Coder ANSI-C Source Code

Top      Up      ToC       Page 147 
       hpInput.c

       Copyright (C) The Internet Society (2004).
       All Rights Reserved.

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

   #include "constants.h"

   /*----------------------------------------------------------------*
    *  Input high-pass filter
    *---------------------------------------------------------------*/

   void hpInput(
       float *In,  /* (i) vector to filter */
       int len,    /* (i) length of vector to filter */
       float *Out, /* (o) the resulting filtered vector */
       float *mem  /* (i/o) the filter state */
   ){
       int i;
       float *pi, *po;

       /* all-zero section*/

       pi = &In[0];
       po = &Out[0];
       for (i=0; i<len; i++) {
           *po = hpi_zero_coefsTbl[0] * (*pi);
           *po += hpi_zero_coefsTbl[1] * mem[0];
           *po += hpi_zero_coefsTbl[2] * mem[1];

           mem[1] = mem[0];
           mem[0] = *pi;
           po++;
           pi++;

       }

       /* all-pole section*/

       po = &Out[0];
       for (i=0; i<len; i++) {
           *po -= hpi_pole_coefsTbl[1] * mem[2];
           *po -= hpi_pole_coefsTbl[2] * mem[3];

           mem[3] = mem[2];
           mem[2] = *po;
           po++;

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       }
   }

A.29.  hpOutput.h

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

       iLBC Speech Coder ANSI-C Source Code

       hpOutput.h

       Copyright (C) The Internet Society (2004).
       All Rights Reserved.

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

   #ifndef __iLBC_HPOUTPUT_H
   #define __iLBC_HPOUTPUT_H

   void hpOutput(
       float *In,  /* (i) vector to filter */
       int len,/* (i) length of vector to filter */
       float *Out, /* (o) the resulting filtered vector */
       float *mem  /* (i/o) the filter state */
   );

   #endif

A.30.  hpOutput.c

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

       iLBC Speech Coder ANSI-C Source Code

       hpOutput.c

       Copyright (C) The Internet Society (2004).
       All Rights Reserved.

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

   #include "constants.h"

   /*----------------------------------------------------------------*
    *  Output high-pass filter
    *---------------------------------------------------------------*/

   void hpOutput(

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       float *In,  /* (i) vector to filter */
       int len,/* (i) length of vector to filter */
       float *Out, /* (o) the resulting filtered vector */
       float *mem  /* (i/o) the filter state */
   ){
       int i;
       float *pi, *po;

       /* all-zero section*/

       pi = &In[0];
       po = &Out[0];
       for (i=0; i<len; i++) {
           *po = hpo_zero_coefsTbl[0] * (*pi);
           *po += hpo_zero_coefsTbl[1] * mem[0];
           *po += hpo_zero_coefsTbl[2] * mem[1];

           mem[1] = mem[0];
           mem[0] = *pi;
           po++;
           pi++;

       }

       /* all-pole section*/

       po = &Out[0];
       for (i=0; i<len; i++) {
           *po -= hpo_pole_coefsTbl[1] * mem[2];
           *po -= hpo_pole_coefsTbl[2] * mem[3];

           mem[3] = mem[2];
           mem[2] = *po;
           po++;
       }
   }

A.31.  iCBConstruct.h

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

       iLBC Speech Coder ANSI-C Source Code

       iCBConstruct.h

       Copyright (C) The Internet Society (2004).
       All Rights Reserved.

Top      Up      ToC       Page 150 
   ******************************************************************/

   #ifndef __iLBC_ICBCONSTRUCT_H
   #define __iLBC_ICBCONSTRUCT_H

   void index_conv_enc(
       int *index          /* (i/o) Codebook indexes */
   );

   void index_conv_dec(
       int *index          /* (i/o) Codebook indexes */
   );

   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 */
   );

   #endif

A.32.  iCBConstruct.c

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

       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
    *---------------------------------------------------------------*/

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   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;

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       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];
               }
           }
       }
   }



(page 152 continued on part 6)

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