FrameClassify.c

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

 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++) {





 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++) {






 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;
 }