pitch_fr.cpp

实现3GPP的GSM中AMR语音的CODECS。

    corr = &corr_v[-t_min];

    //-----------------------------------------------------------------------
      Compute normalized correlation between target and filtered excitation
     -----------------------------------------------------------------------

    Norm_Corr (exc, xn, h, L_subfr, t_min, t_max, corr);

    //-----------------------------------------------------------------------
                                Find integer pitch
     -----------------------------------------------------------------------

    max = corr[t0_min];
    lag = t0_min;

    for (i = t0_min + 1; i <= t0_max; i++) {
        if (sub (corr[i], max) >= 0) {
            max = corr[i];
            lag = i;
        }
    }

    //-----------------------------------------------------------------------
                             Find fractional pitch
     -----------------------------------------------------------------------
    if ((delta_search == 0) && (sub (lag, max_frac_lag) > 0)) {

        // full search and integer pitch greater than max_frac_lag
        // fractional search is not needed, set fractional to zero

        frac = 0;
    }
    else {

        // if differential search AND mode MR475 OR MR515 OR MR59 OR MR67
        // then search fractional with 4 bits resolution

       if ((delta_search != 0) &&
           ((sub ((Word16)mode, (Word16)MR475) == 0) ||
            (sub ((Word16)mode, (Word16)MR515) == 0) ||
            (sub ((Word16)mode, (Word16)MR59) == 0) ||
            (sub ((Word16)mode, (Word16)MR67) == 0))) {

          // modify frac or last_frac according to position of last
          // integer pitch: either search around integer pitch,
          // or only on left or right side

          tmp_lag = st->T0_prev_subframe;
          if ( sub( sub(tmp_lag, t0_min), 5) > 0)
             tmp_lag = add (t0_min, 5);
          if ( sub( sub(t0_max, tmp_lag), 4) > 0)
               tmp_lag = sub (t0_max, 4);

          if ((sub (lag, tmp_lag) == 0) ||
              (sub (lag, sub(tmp_lag, 1)) == 0)) {

             // normal search in fractions around T0

             searchFrac (&lag, &frac, last_frac, corr, flag3);

          }
          else if (sub (lag, sub (tmp_lag, 2)) == 0) {
             // limit search around T0 to the right side
             frac = 0;
             searchFrac (&lag, &frac, last_frac, corr, flag3);
          }
          else if (sub (lag, add(tmp_lag, 1)) == 0) {
             // limit search around T0 to the left side
             last_frac = 0;
             searchFrac (&lag, &frac, last_frac, corr, flag3);
          }
          else {
             // no fractional search
             frac = 0;
            }
       }
       else
          // test the fractions around T0
          searchFrac (&lag, &frac, last_frac, corr, flag3);
    }

    //-----------------------------------------------------------------------
     //                           encode pitch
     //-----------------------------------------------------------------------

    if (flag3 != 0) {
       // flag4 indicates encoding with 4 bit resolution;
       // this is needed for mode MR475, MR515 and MR59

       flag4 = 0;
       if ( (sub ((Word16)mode, (Word16)MR475) == 0) ||
            (sub ((Word16)mode, (Word16)MR515) == 0) ||
            (sub ((Word16)mode, (Word16)MR59) == 0) ||
            (sub ((Word16)mode, (Word16)MR67) == 0) ) {
          flag4 = 1;
       }

       // encode with 1/3 subsample resolution

       *ana_index = Enc_lag3(lag, frac, st->T0_prev_subframe,
                             t0_min, t0_max, delta_search, flag4);
       // function result

    }
    else
    {
       // encode with 1/6 subsample resolution

       *ana_index = Enc_lag6(lag, frac, t0_min, delta_search);
       // function result
    }

     //-----------------------------------------------------------------------
     //                          update state variables
     //-----------------------------------------------------------------------

    st->T0_prev_subframe = lag;

     //-----------------------------------------------------------------------
     //                      update output variables
     //-----------------------------------------------------------------------

    *resu3    = flag3;

    *pit_frac = frac;

    return (lag);
}


------------------------------------------------------------------------------
 RESOURCES USED [optional]

 When the code is written for a specific target processor the
 the resources used should be documented below.

 HEAP MEMORY USED: x bytes

 STACK MEMORY USED: x bytes

 CLOCK CYCLES: (cycle count equation for this function) + (variable
                used to represent cycle count for each subroutine
                called)
     where: (cycle count variable) = cycle count for [subroutine
                                     name]

------------------------------------------------------------------------------
 CAUTION [optional]
 [State any special notes, constraints or cautions for users of this function]

------------------------------------------------------------------------------
*/
Word16 Pitch_fr(         /* o   : pitch period (integer)                    */
    Pitch_frState *st,   /* i/o : State struct                              */
    enum Mode mode,      /* i   : codec mode                                */
    Word16 T_op[],       /* i   : open loop pitch lags                      */
    Word16 exc[],        /* i   : excitation buffer                      Q0 */
    Word16 xn[],         /* i   : target vector                          Q0 */
    Word16 h[],          /* i   : impulse response of synthesis and
                                  weighting filters                     Q12 */
    Word16 L_subfr,      /* i   : Length of subframe                        */
    Word16 i_subfr,      /* i   : subframe offset                           */
    Word16 *pit_frac,    /* o   : pitch period (fractional)                 */
    Word16 *resu3,       /* o   : subsample resolution 1/3 (=1) or 1/6 (=0) */
    Word16 *ana_index,   /* o   : index of encoding                         */
    Flag   *pOverflow
)
{
    Word16 i;
    Word16 t_min;
    Word16 t_max;
    Word16 t0_min = 0;
    Word16 t0_max;
    Word16 max;
    Word16 lag;
    Word16 frac;
    Word16 tmp_lag;
    Word16 *corr;
    Word16 corr_v[40];    /* Total length = t0_max-t0_min+1+2*L_INTER_SRCH */

    Word16 max_frac_lag;
    Word16 flag3;
    Word16 flag4;
    Word16 last_frac;
    Word16 delta_int_low;
    Word16 delta_int_range;
    Word16 delta_frc_low;
    Word16 delta_frc_range;
    Word16 pit_min;
    Word16 frame_offset;
    Word16 delta_search;

    /*-----------------------------------------------------------------------*
     *                      set mode specific variables                      *
     *-----------------------------------------------------------------------*/

    max_frac_lag    = mode_dep_parm[mode].max_frac_lag;
    flag3           = mode_dep_parm[mode].flag3;
    frac            = mode_dep_parm[mode].first_frac;
    last_frac       = mode_dep_parm[mode].last_frac;
    delta_int_low   = mode_dep_parm[mode].delta_int_low;
    delta_int_range = mode_dep_parm[mode].delta_int_range;

    delta_frc_low   = mode_dep_parm[mode].delta_frc_low;
    delta_frc_range = mode_dep_parm[mode].delta_frc_range;
    pit_min         = mode_dep_parm[mode].pit_min;

    /*-----------------------------------------------------------------------*
     *                 decide upon full or differential search               *
     *-----------------------------------------------------------------------*/

    delta_search = 1;

    if ((i_subfr == 0) || (i_subfr == L_FRAME_BY2))
    {

        /* Subframe 1 and 3 */

        if (((mode != MR475) && (mode != MR515)) || (i_subfr != L_FRAME_BY2))
        {

            /* set t0_min, t0_max for full search */
            /* this is *not* done for mode MR475, MR515 in subframe 3 */

            delta_search = 0; /* no differential search */

            /* calculate index into T_op which contains the open-loop */
            /* pitch estimations for the 2 big subframes */

            frame_offset = 1;
            if (i_subfr == 0)
                frame_offset = 0;

            /* get T_op from the corresponding half frame and */
            /* set t0_min, t0_max */

            getRange(T_op[frame_offset], delta_int_low, delta_int_range,
                     pit_min, PIT_MAX, &t0_min, &t0_max, pOverflow);
        }
        else
        {

            /* mode MR475, MR515 and 3. Subframe: delta search as well */
            getRange(st->T0_prev_subframe, delta_frc_low, delta_frc_range,
                     pit_min, PIT_MAX, &t0_min, &t0_max, pOverflow);
        }
    }
    else
    {

        /* for Subframe 2 and 4 */
        /* get range around T0 of previous subframe for delta search */

        getRange(st->T0_prev_subframe, delta_frc_low, delta_frc_range,
                 pit_min, PIT_MAX, &t0_min, &t0_max, pOverflow);
    }

    /*-----------------------------------------------------------------------*
     *           Find interval to compute normalized correlation             *
     *-----------------------------------------------------------------------*/

    t_min = sub(t0_min, L_INTER_SRCH, pOverflow);
    t_max = add(t0_max, L_INTER_SRCH, pOverflow);

    corr = &corr_v[-t_min];

    /*-----------------------------------------------------------------------*
     * Compute normalized correlation between target and filtered excitation *
     *-----------------------------------------------------------------------*/

    Norm_Corr(exc, xn, h, L_subfr, t_min, t_max, corr, pOverflow);

    /*-----------------------------------------------------------------------*
     *                           Find integer pitch                          *
     *-----------------------------------------------------------------------*/

    max = corr[t0_min];
    lag = t0_min;

    for (i = t0_min + 1; i <= t0_max; i++)
    {
        if (corr[i] >= max)
        {
            max = corr[i];
            lag = i;
        }
    }

    /*-----------------------------------------------------------------------*
     *                        Find fractional pitch                          *
     *-----------------------------------------------------------------------*/
    if ((delta_search == 0) && (lag > max_frac_lag))
    {

        /* full search and integer pitch greater than max_frac_lag */
        /* fractional search is not needed, set fractional to zero */

        frac = 0;
    }
    else
    {

        /* if differential search AND mode MR475 OR MR515 OR MR59 OR MR67   */
        /* then search fractional with 4 bits resolution           */

        if ((delta_search != 0) &&
                ((mode == MR475) || (mode == MR515) ||
                 (mode == MR59) || (mode == MR67)))
        {

            /* modify frac or last_frac according to position of last */
            /* integer pitch: either search around integer pitch, */
            /* or only on left or right side */

            tmp_lag = st->T0_prev_subframe;
            if (sub(sub(tmp_lag, t0_min, pOverflow), 5, pOverflow) > 0)
                tmp_lag = add(t0_min, 5, pOverflow);
            if (sub(sub(t0_max, tmp_lag, pOverflow), 4, pOverflow) > 0)
                tmp_lag = sub(t0_max, 4, pOverflow);

            if ((lag == tmp_lag) || (lag == (tmp_lag - 1)))
            {

                /* normal search in fractions around T0 */

                searchFrac(&lag, &frac, last_frac, corr, flag3, pOverflow);

            }
            else if (lag == (tmp_lag - 2))
            {
                /* limit search around T0 to the right side */
                frac = 0;
                searchFrac(&lag, &frac, last_frac, corr, flag3, pOverflow);
            }
            else if (lag == (tmp_lag + 1))
            {
                /* limit search around T0 to the left side */
                last_frac = 0;
                searchFrac(&lag, &frac, last_frac, corr, flag3, pOverflow);
            }
            else
            {
                /* no fractional search */
                frac = 0;
            }
        }
        else
            /* test the fractions around T0 */
            searchFrac(&lag, &frac, last_frac, corr, flag3, pOverflow);
    }

    /*-----------------------------------------------------------------------*
     *                           encode pitch                                *
     *-----------------------------------------------------------------------*/

    if (flag3 != 0)
    {
        /* flag4 indicates encoding with 4 bit resolution;         */
        /* this is needed for mode MR475, MR515 and MR59           */

        flag4 = 0;
        if ((mode == MR475) || (mode == MR515) ||
                (mode == MR59) || (mode == MR67))
        {
            flag4 = 1;
        }

        /* encode with 1/3 subsample resolution */

        *ana_index = Enc_lag3(lag, frac, st->T0_prev_subframe,
                              t0_min, t0_max, delta_search, flag4, pOverflow);
        /* function result */

    }
    else
    {
        /* encode with 1/6 subsample resolution */

        *ana_index = Enc_lag6(lag, frac, t0_min, delta_search, pOverflow);
        /* function result */
    }

    /*-----------------------------------------------------------------------*
     *                          update state variables                       *
     *-----------------------------------------------------------------------*/

    st->T0_prev_subframe = lag;

    /*-----------------------------------------------------------------------*
     *                      update output variables                          *
     *-----------------------------------------------------------------------*/

    *resu3    = flag3;

    *pit_frac = frac;

    return (lag);
}