cor_func.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
                         Version 1.01 of 15.September.98
*/

/*
----------------------------------------------------------------------
                    COPYRIGHT NOTICE
----------------------------------------------------------------------
   ITU-T G.729 Annex C ANSI C source code
   Copyright (C) 1998, AT&T, France Telecom, NTT, University of
   Sherbrooke.  All rights reserved.

----------------------------------------------------------------------
*/

/*
 File : COR_FUNC.C
*/

/* Functions corr_xy2() and cor_h_x()   */

#include "typedef.h"
#include "ld8k.h"

/*----------------------------------------------------------------------------
* corr_xy2 - compute the correlation products needed for gain computation
*----------------------------------------------------------------------------
*/
void corr_xy2(
    FLOAT xn[],            /* input : target vector x[0:l_subfr] */
    FLOAT y1[],            /* input : filtered adaptive codebook vector */
    FLOAT y2[],            /* input : filtered 1st codebook innovation */
    FLOAT g_coeff[]        /* output: <y2,y2> , -2<xn,y2> , and 2<y1,y2>*/
)
{
    FLOAT y2y2, xny2, y1y2;
    int i;
    
    y2y2= (F)0.01;
    for (i = 0; i < L_SUBFR; i++) y2y2 += y2[i]*y2[i];
    g_coeff[2] = y2y2 ;
    
    xny2 = (F)0.01;
    for (i = 0; i < L_SUBFR; i++) xny2+= xn[i]*y2[i];
    g_coeff[3] = (F)-2.0* xny2;
    
    y1y2 = (F)0.01;
    for (i = 0; i < L_SUBFR; i++) y1y2 += y1[i]*y2[i];
    g_coeff[4] = (F)2.0* y1y2 ;
    
    return;
    
}

/*--------------------------------------------------------------------------*
*  Function  cor_h_x()                                                     *
*  ~~~~~~~~~~~~~~~~~~~~                                                    *
* Compute  correlations of input response h[] with the target vector X[].  *
*--------------------------------------------------------------------------*/

void cor_h_x(
    FLOAT h[],        /* (i) :Impulse response of filters      */
    FLOAT x[],        /* (i) :Target vector                    */
    FLOAT d[]         /* (o) :Correlations between h[] and x[] */
)
{
    int i, j;
    FLOAT  s;
    
    for (i = 0; i < L_SUBFR; i++)
    {
        s = (F)0.0;
        for (j = i; j <  L_SUBFR; j++)
            s += x[j] * h[j-i];
        d[i] = s;
    }
    
    return;
}