frameclassify.c

视频监控vc源代码.对于做视频系统的朋友们很有帮助

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

    iLBC Speech Coder ANSI-C Source Code

    FrameClassify.c 

    Copyright (C) The Internet Society (2004). 
    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 */
    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;
}