www.pudn.com > p_voice.rar > VAD2.C

 
/* 
** 
** File:        "vad2.c" 
** 
** Description:     Voice Activity Detection 
** 
** Functions:       Init_Vad() 
**                  Vad() 
** 
** 
*/ 
/* 
    ITU-T G.723.1 Floating Point Speech Coder ANSI C Source Code.  Version 5.1F 
    copyright (c) 1995, AudioCodes, DSP Group, France Telecom, 
    Universite de Sherbrooke.  All rights reserved. 
 
    Floating-point code copyright (c) 1996, 
    Intel Corporation and France Telecom (CNET). 
    All rights reserved. 
*/ 
 
#include  
#include  
#include  
 
#include "typedef2.h" 
#include "cst2.h" 
#include "tab2.h" 
#include "lsp2.h" 
#include "vad2.h" 
#include "coder2.h" 
#include "lbccode2.h" 
 
VADSTATDEF  VadStat ; 
 
void    Init_Vad(void) 
{ 
    int i ; 
 
    VadStat.Hcnt = 3 ; 
    VadStat.Vcnt = 0 ; 
    VadStat.Penr = (FLOAT) 1024.0; 
    VadStat.Nlev = (FLOAT) 1024.0; 
 
    VadStat.Aen = 0; 
 
    VadStat.Polp[0] = 1; 
    VadStat.Polp[1] = 1; 
    VadStat.Polp[2] = SubFrLen; 
    VadStat.Polp[3] = SubFrLen; 
 
    for (i=0; i < LpcOrder; i++) 
        VadStat.NLpc[i] = (FLOAT)0.0; 
 
} 
 
Flag Comp_Vad(FLOAT *Dpnt) 
{ 
    int     i, j, bexp; 
 
    FLOAT   Acc0, Frac, Thresh, Enr; 
    FLOAT   Temp; 
    Word32  Tm1, Tm2; 
    Word16  Minp; 
 
    Flag    VadState = 1 ; 
 
    static  FLOAT  ScfTab[11] = { 
        (FLOAT)  9170.0, 
        (FLOAT)  9170.0, 
        (FLOAT)  9170.0, 
        (FLOAT)  9170.0, 
        (FLOAT) 10289.0, 
        (FLOAT) 11544.0, 
        (FLOAT) 12953.0, 
        (FLOAT) 14533.0, 
        (FLOAT) 16306.0, 
        (FLOAT) 18296.0, 
        (FLOAT) 20529.0 
    }; 
 
    if ( !UseVx ) 
        return VadState ; 
 
    /* Find Minimum pitch period */ 
    Minp = (Word16) PitchMax ; 
    for ( i = 0 ; i < 4 ; i ++ ) { 
        if ( Minp > VadStat.Polp[i] ) 
            Minp = VadStat.Polp[i] ; 
    } 
 
    /* Check that all are multiplies of the minimum */ 
    Tm2 = 0 ; 
    for ( i = 0 ; i < 4 ; i ++ ) { 
        Tm1 = Minp ; 
        for ( j = 0 ; j < 8 ; j ++ ) { 
            if (abs((int)(Tm1 - VadStat.Polp[i])) <= 3) 
                Tm2++ ; 
            Tm1 += Minp; 
        } 
    } 
 
    /* Update adaptation enable counter if not periodic and not sine */ 
    if ( (Tm2 == 4) || (CodStat.SinDet < 0) ) 
        VadStat.Aen += 2 ; 
    else 
        VadStat.Aen -- ; 
 
    /* Clip it */ 
    if ( VadStat.Aen > 6 ) 
        VadStat.Aen = 6 ; 
    if ( VadStat.Aen < 0 ) 
        VadStat.Aen = 0 ; 
 
    /* Inverse filter the data */ 
    Enr = (FLOAT) 0.0; 
    for ( i = SubFrLen ; i < Frame ; i ++ ) { 
        Acc0 = Dpnt[i]; 
        for ( j = 0 ; j < LpcOrder ; j ++ ) 
            Acc0 -= Dpnt[i-j-1] * VadStat.NLpc[j]; 
        Enr += Acc0 * Acc0; 
    } 
 
    /* Scale the rezidual energy. 
     * Multiplication by 0.5 yields a value approximately equal 
     * to the corresponding computation in the fixed point code. 
     * Thus the same bounds, computations and thresholds as in the 
     * fixed point code can be used below. 
     */ 
    Enr = (FLOAT)0.5 * (Enr / (FLOAT)180.0); 
 
    /* Clip noise level in any case */ 
    if ( VadStat.Nlev > VadStat.Penr ) { 
        VadStat.Nlev = (FLOAT)0.25 * VadStat.Nlev + (FLOAT)0.75 * VadStat.Penr; 
    } 
 
    /* Update the noise level, if adaptation is enabled */ 
    if ( !VadStat.Aen ) { 
        VadStat.Nlev *= (FLOAT)33.0 / (FLOAT)32.0; 
    } 
    /* Decay Nlev by small amount */ 
    else { 
        VadStat.Nlev *= (FLOAT)2047.0 / (FLOAT)2048.0; 
    } 
 
    /* Update previous energy */ 
    VadStat.Penr = Enr; 
 
    /* CLip Noise Level */ 
    if (VadStat.Nlev < (FLOAT) 128.0) 
        VadStat.Nlev = (FLOAT) 128.0; 
    if (VadStat.Nlev > (FLOAT) 131071.0) 
        VadStat.Nlev = (FLOAT) 131071.0; 
 
    /* Compute the threshold */ 
    Frac = (FLOAT) frexp(VadStat.Nlev, &bexp); 
    /* VadStat.Nlev = Frac x 2**bexp, where Frac = 0.1bbbbbb...., binary. 
     * Isolate the 6 fractional bits 'b', Temp = 0.bbbbbb. 
     */ 
    Temp = ((FLOAT)floor(Frac * (FLOAT)128.0) / (FLOAT)64.0) - (FLOAT)1.0; 
    Temp = ((FLOAT)1.0 - Temp) * ScfTab[18 - bexp] + Temp * ScfTab[17 - bexp]; 
    Thresh = (Temp * VadStat.Nlev) / (FLOAT)4096.0; 
 
    /* Compare with the threshold */ 
    if (Thresh > Enr) 
        VadState = 0 ; 
 
    /* Do the various counters */ 
    if ( VadState ) { 
        VadStat.Vcnt ++ ; 
        VadStat.Hcnt ++ ; 
    } 
    else { 
        VadStat.Vcnt -- ; 
        if ( VadStat.Vcnt < 0 ) 
            VadStat.Vcnt = 0 ; 
    } 
 
    if ( VadStat.Vcnt >= 2 ) { 
        VadStat.Hcnt = 6 ; 
        if (VadStat.Vcnt >= 3) 
            VadStat.Vcnt = 3; 
    } 
 
    if ( VadStat.Hcnt ) { 
        VadState = 1 ; 
        if ( VadStat.Vcnt == 0 ) 
            VadStat.Hcnt -- ; 
    } 
 
    /* Update Periodicy detector */ 
    VadStat.Polp[0] = VadStat.Polp[2] ; 
    VadStat.Polp[1] = VadStat.Polp[3] ; 
 
    return VadState ; 
}