/****************************************************************** 
 
    iLBC Speech Coder ANSI-C Source Code 
 
    FrameClassify.c  
 
    Copyright (c) 2001, 
    Global IP Sound AB. 
    All rights reserved. 
 
******************************************************************/ 
 
#include "iLBC_define.h" 
#include "FrameClassify.h"
 
/*----------------------------------------------------------------* 
 *  Classification of subframes to localize start state                           
 *---------------------------------------------------------------*/ 
 
int FrameClassify(  /* index to the max-energy sub frame */ 
    float *residual /* (i) lpc residual signal */ 
){ 
    float max_ssqEn, fssqEn[NSUB], bssqEn[NSUB], *pp; 
    int n, l, max_ssqEn_n; 
    const float ssqEn_win[NSUB-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*sizeof(float)); 
    memset(bssqEn, 0, NSUB*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<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=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 */ 
 
    max_ssqEn=(fssqEn[0]+bssqEn[1])*ssqEn_win[0]; 
    max_ssqEn_n=1; 
    for (n=2;n<NSUB;n++) { 
         
        if ((fssqEn[n-1]+bssqEn[n])*ssqEn_win[n-1] > max_ssqEn) { 
            max_ssqEn=(fssqEn[n-1]+bssqEn[n]) * 
                            ssqEn_win[n-1]; 
            max_ssqEn_n=n; 
        } 
    } 
 
    return max_ssqEn_n; 
}