bwfwfunc.c

语音压缩编码中的g729p编码程序

/*
   ITU-T G.729 Annex C+ - Reference C code for floating point
                         implementation of G.729 Annex C+
                         (integration of Annexes B, D and E)
                          Version 2.1 of October 1999
*/
/*
 File : BWFWFUNC.C
 */

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

#include "typedef.h"
#include "ld8k.h"
#include "ld8cp.h"
#include "tabld8cp.h"


/* -------------------------------------------------------------------- */
/*                          TST_BWD_DOMINANT                            */
/* -------------------------------------------------------------------- */
/* Test if backward mode is dominant :                                  */
/* Nbre of Backward frames > 4 * Nbre of Forward frames                 */
/* It is used for the choice of the perceptual weighting filter         */
/* Backward dominant : music or stationnary background noise :          */
/*         Quantized filter (30 coef.) + strong weighting               */
/* No backward dominant => Non Stationnary signal (mainly speech) :     */
/*         Unquantized filter (10 coef.) + normal weighting             */
/* -------------------------------------------------------------------- */
static int  count_bwd2 = 0, count_fwd2 = 0;

void tst_bwd_dominant(
int *bwd_dominant, /* O   Dominant backward mode indication */
int mode)          /* I   Selected LPC mode */
{
        
    int tmp, count_all;
        
    if (mode == 0) count_fwd2++;
    else count_bwd2++;
        
    count_all = count_bwd2 + count_fwd2;
        
    if (count_all == 100) {
        count_all = count_all >> 1;
        count_bwd2 = count_bwd2 >> 1;
        count_fwd2 = count_fwd2 >> 1;
    }
        
    *bwd_dominant = 0;
    if (count_all >= 10) {
        tmp = count_fwd2 << 2;
        if (count_bwd2 > tmp) *bwd_dominant = 1;
    }
        
    return;
}




void int_bwd(FLOAT *a_bwd, /* I/O   LPC backward filter */
FLOAT *prev_filter, /* I previous frame filter */
FLOAT *C_int     /* I/O interpolation coefficient */
            )       
{
        
    int i;
    FLOAT tmp1, tmp2;
    FLOAT *pa_bwd;
    FLOAT C_int_loc;
        
    pa_bwd = a_bwd + M_BWDP1;
        
    /* Calculate the interpolated filters  */
    /* ----------------------------------  */
    C_int_loc = *C_int - (F)0.1;
    if( C_int_loc < 0) C_int_loc = 0;
        
    for (i=0; i<M_BWDP1; i++) {
        tmp1 = pa_bwd[i] * ((F)1. - C_int_loc);
        tmp2 = prev_filter[i] * C_int_loc;
        pa_bwd[i] = tmp1 + tmp2;
    }
        
    for (i=0; i<M_BWDP1; i++) {
        a_bwd[i] = (F)0.5 * (pa_bwd[i] + prev_filter[i]);
    }
        
    *C_int = C_int_loc;
    return;
}

/* ---------------------------------------------------------------------- */
/*                                 ENER_DB                                */
/*                                                                        */
/*                        COMPUTATION OF THE ENERGY                       */
/*                                                                        */
/* ---------------------------------------------------------------------- */
FLOAT ener_dB(FLOAT *synth, int L) {
        
    int i;
    FLOAT  energy;
    FLOAT tmp, edB;
    INT32 k, Ltmp;
    int n;
        
    for (i=0, energy=(F)0.0001; i<L; i++) {
        energy += synth[i] * synth[i];
    }
    edB = (FLOAT)log10(energy);
    tmp = edB * INV_LOG2;
    n = (int) tmp;
    if(tmp >= (F)4.) {
        if(energy > (F)2147483647.) energy = (F)93.1814;
        else {
            k = (INT32)energy;
            Ltmp = -(1L << (n-4));
            k &= Ltmp;
            tmp = (FLOAT)k;
            energy = (F)10. * (FLOAT)log10(tmp);
        }
    }
    else energy = (F)0.005;
        
    return(energy);
}
/* ----------------------------------------------------------------------- */
/*                                                                         */
/*                              HYBRID WINDOW                              */
/*                              (as in G728)                               */
/*                                                                         */
/*               1st part (0..35) is sine(i*c) where c = 0.047783          */
/*               2nd part (36....) is b*exp((i-35)*log(a))                 */
/*               where b=sine(35*c)                                        */
/*               and a=0.9928337491 is such as a^^40 = 0.75                */
/*               a^^(2*L_FRAME) = 0.75^^4 = 0.31640625                     */
/*                                                                         */
/* ------------------------------------------------------------------------ */

/*------------------------------------------------------------------------------*/
/* Compute the autocorrelation of speech using hybrid window    (as in G.728)   */
/*------------------------------------------------------------------------------*/
void autocorr_hyb_window(
    FLOAT  *x,         /* (in)     synthetized speech signal */
    FLOAT  *r_bwd,       /* (out)    Autocorrelations    */
    FLOAT *rexp        /* (in/out) */
)
{
    FLOAT  tmp;
    int  i, n, k;
    FLOAT w_s[L_ANA_BWD];
        
    for (n=L_ANA_BWD_M1, k=0; n>=0; n--, k++) w_s[n] = x[n] * hw[k];
        
    for (i=0; i<=M_BWD; i++) {
        tmp = 0;
        for (n=M_BWD; n<N1; n++) tmp += w_s[n] * w_s[n-i];
        rexp[i] = W_FACT * rexp[i] + tmp;
    }
        
    for (i=0; i<=M_BWD; i++) {
        r_bwd[i] = rexp[i];
        for (n=N1; n<L_ANA_BWD; n++) r_bwd[i] += w_s[n] * w_s[n-i];
    }
    return;
        
} /* end of autocorr_hyb_windowing() */


/* ---------------------------------------------------------------------- */
/*                                                                        */
/*                             LAG_WINDOW_BWD                             */
/*                                                                        */
/*      Fixed-point Lag Windowing for backward analysis correlations      */
/*           (values of lag_h_bwd and lag_l_bwd in tab_ld8k.h)            */
/*                                                                        */
/* ---------------------------------------------------------------------- */
void lag_window_bwd(FLOAT *r_bwd)
{
        
    int  i;
        
    for (i=1; i<= M_BWD; i++) {
        /* !!! la fenetre debute en 0 pour un terme != de 1 */
        r_bwd[i] *= lag_bwd[i-1];
    }
        
    if (r_bwd[0]<(F)1.0) r_bwd[0]=(F)1.0;
    return;
}