shithub: sox

ref: 47134f81bfadd4dd8616803e6e60158df7c7a834
dir: /amr-wb/autocorr.c/

/*------------------------------------------------------------------------*
 *                         AUTOCORR.C                                     *
 *------------------------------------------------------------------------*
 *   Compute autocorrelations of signal with windowing                    *
 *                                                                        *
 *------------------------------------------------------------------------*/

#include "typedef.h"
#include "basic_op.h"
#include "oper_32b.h"
#include "acelp.h"
#include "count.h"

#include "ham_wind.tab"


void Autocorr(
     Word16 x[],                           /* (i)    : Input signal                      */
     Word16 m,                             /* (i)    : LPC order                         */
     Word16 r_h[],                         /* (o) Q15: Autocorrelations  (msb)           */
     Word16 r_l[]                          /* (o)    : Autocorrelations  (lsb)           */
)
{
    Word16 i, j, norm, shift, y[L_WINDOW];
    Word32 L_sum, L_tmp;

    /* Windowing of signal */

    for (i = 0; i < L_WINDOW; i++)
    {
        y[i] = mult_r(x[i], window[i]);    move16();
    }

    /* calculate energy of signal */

    L_sum = L_deposit_h(16);               /* sqrt(256), avoid overflow after rounding */
    for (i = 0; i < L_WINDOW; i++)
    {
        L_tmp = L_mult(y[i], y[i]);
        L_tmp = L_shr(L_tmp, 8);
        L_sum = L_add(L_sum, L_tmp);
    }

    /* scale signal to avoid overflow in autocorrelation */

    norm = norm_l(L_sum);
    shift = sub(4, shr(norm, 1));
    test();
    if (shift < 0)
    {
        shift = 0;                         move16();
    }
    for (i = 0; i < L_WINDOW; i++)
    {
        y[i] = shr_r(y[i], shift);         move16();
    }

    /* Compute and normalize r[0] */

    L_sum = 1;                             move32();
    for (i = 0; i < L_WINDOW; i++)
        L_sum = L_mac(L_sum, y[i], y[i]);

    norm = norm_l(L_sum);
    L_sum = L_shl(L_sum, norm);
    L_Extract(L_sum, &r_h[0], &r_l[0]);    /* Put in DPF format (see oper_32b) */

    /* Compute r[1] to r[m] */

    for (i = 1; i <= m; i++)
    {
        L_sum = 0;                         move32();
        for (j = 0; j < L_WINDOW - i; j++)
            L_sum = L_mac(L_sum, y[j], y[j + i]);

        L_sum = L_shl(L_sum, norm);
        L_Extract(L_sum, &r_h[i], &r_l[i]);
    }

    return;
}