docplc.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

    doCPLC.c 

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

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

#include <math.h>
#include <string.h>
#include <stdio.h>

#include "iLBC_define.h"
#include "doCPLC.h"

/*----------------------------------------------------------------*
 *  Compute cross correlation and pitch gain for pitch prediction
 *  of last subframe at given lag.
 *---------------------------------------------------------------*/

static void compCorr(
    float *cc,      /* (o) cross correlation coefficient */
    float *gc,      /* (o) gain */
    float *pm,
    float *buffer,  /* (i) signal buffer */
    int lag,    /* (i) pitch lag */
    int bLen,       /* (i) length of buffer */
    int sRange      /* (i) correlation search length */
){


    int i;
    float ftmp1, ftmp2, ftmp3;

    /* Guard against getting outside buffer */
    if ((bLen-sRange-lag)<0) {
        sRange=bLen-lag;
    }

    ftmp1 = 0.0;
    ftmp2 = 0.0;
    ftmp3 = 0.0;
    for (i=0; i<sRange; i++) {
        ftmp1 += buffer[bLen-sRange+i] *
            buffer[bLen-sRange+i-lag];
        ftmp2 += buffer[bLen-sRange+i-lag] * 
                buffer[bLen-sRange+i-lag];
        ftmp3 += buffer[bLen-sRange+i] * 
                buffer[bLen-sRange+i];
    }

    if (ftmp2 > 0.0) {
        *cc = ftmp1*ftmp1/ftmp2;
        *gc = (float)fabs(ftmp1/ftmp2);
        *pm=(float)fabs(ftmp1)/
            ((float)sqrt(ftmp2)*(float)sqrt(ftmp3));
    }
    else {
        *cc = 0.0;
        *gc = 0.0;
        *pm=0.0;
    }
}

/*----------------------------------------------------------------*
 *  Packet loss concealment routine. Conceals a residual signal
 *  and LP parameters. If no packet loss, update state.
 *---------------------------------------------------------------*/

void doThePLC(
    float *PLCresidual, /* (o) concealed residual */ 
    float *PLClpc,      /* (o) concealed LP parameters */  
    int PLI,        /* (i) packet loss indicator 
                               0 - no PL, 1 = PL */ 
    float *decresidual, /* (i) decoded residual */
    float *lpc,         /* (i) decoded LPC (only used for no PL) */
    int inlag,          /* (i) pitch lag */
    iLBC_Dec_Inst_t *iLBCdec_inst 
                        /* (i/o) decoder instance */
){
    int lag=20, randlag;
    float gain, maxcc;
    float use_gain;
    float gain_comp, maxcc_comp, per, max_per;
    int i, pick, use_lag;


    float ftmp, randvec[BLOCKL_MAX], pitchfact, energy;
            
    /* Packet Loss */

    if (PLI == 1) {
        
        iLBCdec_inst->consPLICount += 1;
        
        /* if previous frame not lost, 
           determine pitch pred. gain */
        
        if (iLBCdec_inst->prevPLI != 1) {

            /* Search around the previous lag to find the 
               best pitch period */
            
            lag=inlag-3;
            compCorr(&maxcc, &gain, &max_per, 
                iLBCdec_inst->prevResidual,
                lag, iLBCdec_inst->blockl, 60);
            for (i=inlag-2;i<=inlag+3;i++) {
                compCorr(&maxcc_comp, &gain_comp, &per,
                    iLBCdec_inst->prevResidual,
                    i, iLBCdec_inst->blockl, 60);
                
                if (maxcc_comp>maxcc) {
                    maxcc=maxcc_comp;
                    gain=gain_comp;
                    lag=i;
                    max_per=per;
                }
            }
            
        }

        /* previous frame lost, use recorded lag and periodicity */

        else {
            lag=iLBCdec_inst->prevLag;
            max_per=iLBCdec_inst->per;
        }
        
        /* downscaling */

        use_gain=1.0;
        if (iLBCdec_inst->consPLICount*iLBCdec_inst->blockl>320)
            use_gain=(float)0.9;
        else if (iLBCdec_inst->consPLICount*
                        iLBCdec_inst->blockl>2*320)
            use_gain=(float)0.7;
        else if (iLBCdec_inst->consPLICount*
                        iLBCdec_inst->blockl>3*320)
            use_gain=(float)0.5;
        else if (iLBCdec_inst->consPLICount*


                        iLBCdec_inst->blockl>4*320)
            use_gain=(float)0.0;

        /* mix noise and pitch repeatition */
        ftmp=(float)sqrt(max_per);
        if (ftmp>(float)0.7)
            pitchfact=(float)1.0;
        else if (ftmp>(float)0.4)
            pitchfact=(ftmp-(float)0.4)/((float)0.7-(float)0.4);
        else
            pitchfact=0.0;


        /* avoid repetition of same pitch cycle */
        use_lag=lag;
        if (lag<80) {
            use_lag=2*lag;
        }

        /* compute concealed residual */

        energy = 0.0;
        for (i=0; i<iLBCdec_inst->blockl; i++) {

            /* noise component */

            iLBCdec_inst->seed=(iLBCdec_inst->seed*69069L+1) & 
                (0x80000000L-1);
            randlag = 50 + ((signed long) iLBCdec_inst->seed)%70;
            pick = i - randlag;
            
            if (pick < 0) {
                randvec[i] = 
                    iLBCdec_inst->prevResidual[
                                iLBCdec_inst->blockl+pick];
            } else {
                randvec[i] =  randvec[pick];
            }

            /* pitch repeatition component */
            pick = i - use_lag;
            
            if (pick < 0) {
                PLCresidual[i] =  
                    iLBCdec_inst->prevResidual[
                                iLBCdec_inst->blockl+pick];
            } else {
                PLCresidual[i] = PLCresidual[pick];
            }

            /* mix random and periodicity component */

            if (i<80)
                PLCresidual[i] = use_gain*(pitchfact * 


                            PLCresidual[i] +
                            ((float)1.0 - pitchfact) * randvec[i]);
            else if (i<160)
                PLCresidual[i] = (float)0.95*use_gain*(pitchfact * 
                            PLCresidual[i] +
                            ((float)1.0 - pitchfact) * randvec[i]);
            else
                PLCresidual[i] = (float)0.9*use_gain*(pitchfact * 
                            PLCresidual[i] +
                            ((float)1.0 - pitchfact) * randvec[i]);

            energy += PLCresidual[i] * PLCresidual[i];
        }
        
        /* less than 30 dB, use only noise */
        
        if (sqrt(energy/(float)iLBCdec_inst->blockl) < 30.0) { 
            gain=0.0;
            for (i=0; i<iLBCdec_inst->blockl; i++) {
                PLCresidual[i] = randvec[i];
            }
        }

        /* use old LPC */

        memcpy(PLClpc,iLBCdec_inst->prevLpc,
            (LPC_FILTERORDER+1)*sizeof(float));
        
    }

    /* no packet loss, copy input */

    else {
        memcpy(PLCresidual, decresidual, 
            iLBCdec_inst->blockl*sizeof(float));
        memcpy(PLClpc, lpc, (LPC_FILTERORDER+1)*sizeof(float));
        iLBCdec_inst->consPLICount = 0;
    }
    
    /* update state */

    if (PLI) {
        iLBCdec_inst->prevLag = lag;
        iLBCdec_inst->per=max_per;
    }

    iLBCdec_inst->prevPLI = PLI;
    memcpy(iLBCdec_inst->prevLpc, PLClpc, 
        (LPC_FILTERORDER+1)*sizeof(float));
    memcpy(iLBCdec_inst->prevResidual, PLCresidual,
        iLBCdec_inst->blockl*sizeof(float));
}