pitch_a.c

来自「g.729汇编手工优化」· C语言 代码 · 共 97 行

/*---------------------------------------------------------------------------*
 * Pitch related functions                                                   *
 * ~~~~~~~~~~~~~~~~~~~~~~~                                                   *
 *---------------------------------------------------------------------------*/

#include "typedef.h"
#include "basic_op.h"
#include "oper_32b.h"
#include "ld8a.h"
#include "tab_ld8a.h"

/*--------------------------------------------------------------------------*
 *  Function  Pitch_fr3_fast()                                              *
 *  ~~~~~~~~~~~~~~~~~~~~~~~~~~                                              *
 * Fast version of the pitch close loop.                                    *
 *--------------------------------------------------------------------------*/
extern  Word32 Dot_Product(Word16 x[],Word16 y[], Word16 lg);
Word16 Pitch_fr3_fast(/* (o)     : pitch period.                          */
  Word16 exc[],       /* (i)     : excitation buffer                      */
  Word16 xn[],        /* (i)     : target vector                          */
  Word16 h[],         /* (i) Q12 : impulse response of filters.           */
  Word16 L_subfr,     /* (i)     : Length of subframe                     */
  Word16 t0_min,      /* (i)     : minimum value in the searched range.   */
  Word16 t0_max,      /* (i)     : maximum value in the searched range.   */
  Word16 i_subfr,     /* (i)     : indicator for first subframe.          */
  Word16 *pit_frac    /* (o)     : chosen fraction.                       */
)
{
  Word16 t, t0;
  Word16 Dn[L_SUBFR];
  Word16 exc_tmp[L_SUBFR];
  Word32 max, corr, L_temp;

 /*-----------------------------------------------------------------*
  * Compute correlation of target vector with impulse response.     *
  *-----------------------------------------------------------------*/

  Cor_h_X(h, xn, Dn);

 /*-----------------------------------------------------------------*
  * Find maximum integer delay.                                     *
  *-----------------------------------------------------------------*/

  max = MIN_32;
  t0 = t0_min; /* Only to remove warning from some compilers */

  for(t=t0_min; t<=t0_max; t++)
  {
    corr = Dot_Product(Dn, &exc[-t], L_subfr);
    L_temp = L_sub(corr, max);
    if(L_temp > 0) {max = corr; t0 = t;  }
  }

 /*-----------------------------------------------------------------*
  * Test fractions.                                                 *
  *-----------------------------------------------------------------*/

  /* Fraction 0 */

  Pred_lt_3(exc, t0, 0, L_subfr);
  max = Dot_Product(Dn, exc, L_subfr);
  *pit_frac = 0;

  /* If first subframe and lag > 84 do not search fractional pitch */

  if( (i_subfr == 0) && (sub(t0, 84) > 0) )
    return t0;

  Copy(exc, exc_tmp, L_subfr);

  /* Fraction -1/3 */

  Pred_lt_3(exc, t0, -1, L_subfr);
  corr = Dot_Product(Dn, exc, L_subfr);
  L_temp = L_sub(corr, max);
  if(L_temp > 0) {
     max = corr;
     *pit_frac = -1;
     Copy(exc, exc_tmp, L_subfr);
  }

  /* Fraction +1/3 */

  Pred_lt_3(exc, t0, 1, L_subfr);
  corr = Dot_Product(Dn, exc, L_subfr);
  L_temp = L_sub(corr, max);
  if(L_temp > 0) {
     max = corr;
     *pit_frac =  1;
  }
  else
    Copy(exc_tmp, exc, L_subfr);
  return t0;
}