cl_ltp.cpp

实现3GPP的GSM中AMR语音的CODECS。

    // deallocate memory
    free(*state);
    *state = NULL;

    return;
}

------------------------------------------------------------------------------
 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]

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

void cl_ltp_exit(clLtpState **state)
{
    if (state == NULL || *state == NULL)
    {
        return;
    }

    /* dealloc members */
    Pitch_fr_exit(&(*state)->pitchSt);

    /* deallocate memory */
    oscl_free(*state);
    *state = NULL;

    return;
}

/****************************************************************************/

/*
------------------------------------------------------------------------------
 FUNCTION NAME: cl_ltp
------------------------------------------------------------------------------
 INPUT AND OUTPUT DEFINITIONS

 Inputs:
    clSt = pointer to the clLtpState struct
    tonSt = pointer to the tonStabState structure
    mode = codec mode value, of type enum Mode
    frameOffset = offset to subframe (Word16)
    T_op = pointer to buffer of open loop pitch lags (Word16)
    h1 = pointer to impulse response vector (Word16)
    exc = pointer to excitation vector (Word16)
    res2 = pointer to long term prediction residual (Word16)
    xn = pointer to target vector for pitch search (Word16)
    lsp_flag = LSP resonance flag (Word16)

 Outputs:
    clSt = pointer to the clLtpState struct
    tonSt = pointer to the tonStabState structure
    exc = pointer to excitation vector (Word16)
    res2 = pointer to long term prediction residual (Word16)
    xn2 = pointer to target vector for codebook search (Word16)
    yl = pointer to buffer of filtered adaptive excitation (Word16)
    T0 = pointer to pitch delay (integer part) (Word16)
    T0_frac = pointer to pitch delay (fractional part) (Word16)
    gain_pit = pointer to pitch gain (Word16)
    g_coeff = pointer to array of correlations between xn, y1, & y2 (Word16)
    anap = pointer to pointer to analysis parameters (Word16)
    gp_limit = pointer to the pitch gain limit (Word16)
    pOverflow = pointer to overflow indicator (Flag)

 Returns:
    return_value = 0 (int)

 Global Variables Used:
    None

 Local Variables Needed:
    None

------------------------------------------------------------------------------
 FUNCTION DESCRIPTION

 This function performs closed-loop fractional pitch search.

------------------------------------------------------------------------------
 REQUIREMENTS

 None.

------------------------------------------------------------------------------
 REFERENCES

 cl_ltp.c, UMTS GSM AMR speech codec, R99 - Version 3.2.0, March 2, 2001

------------------------------------------------------------------------------
 PSEUDO-CODE FOR cl_ltp

int cl_ltp (
    clLtpState *clSt,    // i/o : State struct
    tonStabState *tonSt, // i/o : State struct
    enum Mode mode,      // i   : coder mode
    Word16 frameOffset,  // i   : Offset to subframe
    Word16 T_op[],       // i   : Open loop pitch lags
    Word16 *h1,          // i   : Impulse response vector               Q12
    Word16 *exc,         // i/o : Excitation vector                      Q0
    Word16 res2[],       // i/o : Long term prediction residual          Q0
    Word16 xn[],         // i   : Target vector for pitch search         Q0
    Word16 lsp_flag,     // i   : LSP resonance flag
    Word16 xn2[],        // o   : Target vector for codebook search      Q0
    Word16 y1[],         // o   : Filtered adaptive excitation           Q0
    Word16 *T0,          // o   : Pitch delay (integer part)
    Word16 *T0_frac,     // o   : Pitch delay (fractional part)
    Word16 *gain_pit,    // o   : Pitch gain                            Q14
    Word16 g_coeff[],    // o   : Correlations between xn, y1, & y2
    Word16 **anap,       // o   : Analysis parameters
    Word16 *gp_limit     // o   : pitch gain limit
)
{
    Word16 i;
    Word16 index;
    Word32 L_temp;     // temporarily variable
    Word16 resu3;      // flag for upsample resolution
    Word16 gpc_flag;

    *----------------------------------------------------------------------*
    *                 Closed-loop fractional pitch search                  *
    *----------------------------------------------------------------------*
   *T0 = Pitch_fr(clSt->pitchSt,
                  mode, T_op, exc, xn, h1,
                  L_SUBFR, frameOffset,
                  T0_frac, &resu3, &index);

   *(*anap)++ = index;

    *-----------------------------------------------------------------*
    *   - find unity gain pitch excitation (adapitve codebook entry)  *
    *     with fractional interpolation.                              *
    *   - find filtered pitch exc. y1[]=exc[] convolve with h1[])     *
    *   - compute pitch gain and limit between 0 and 1.2              *
    *   - update target vector for codebook search                    *
    *   - find LTP residual.                                          *
    *-----------------------------------------------------------------*

   Pred_lt_3or6(exc, *T0, *T0_frac, L_SUBFR, resu3);

   Convolve(exc, h1, y1, L_SUBFR);

   // gain_pit is Q14 for all modes
   *gain_pit = G_pitch(mode, xn, y1, g_coeff, L_SUBFR);


   // check if the pitch gain should be limit due to resonance in LPC filter
   gpc_flag = 0;
   *gp_limit = MAX_16;
   if ((lsp_flag != 0) &&
       (sub(*gain_pit, GP_CLIP) > 0))
   {
       gpc_flag = check_gp_clipping(tonSt, *gain_pit);
   }

   // special for the MR475, MR515 mode; limit the gain to 0.85 to
   // cope with bit errors in the decoder in a better way.
   if ((sub (mode, MR475) == 0) || (sub (mode, MR515) == 0)) {
      if ( sub (*gain_pit, 13926) > 0) {
         *gain_pit = 13926;   // 0.85 in Q14
      }

      if (gpc_flag != 0) {
          *gp_limit = GP_CLIP;
      }
   }
   else
   {
       if (gpc_flag != 0)
       {
           *gp_limit = GP_CLIP;
           *gain_pit = GP_CLIP;
       }
       // For MR122, gain_pit is quantized here and not in gainQuant
       if (sub(mode, MR122)==0)
       {
           *(*anap)++ = q_gain_pitch(MR122, *gp_limit, gain_pit,
                                     NULL, NULL);
       }
   }

   // update target vector und evaluate LTP residual
   for (i = 0; i < L_SUBFR; i++) {
       L_temp = L_mult(y1[i], *gain_pit);
       L_temp = L_shl(L_temp, 1);
       xn2[i] = sub(xn[i], extract_h(L_temp));

       L_temp = L_mult(exc[i], *gain_pit);
       L_temp = L_shl(L_temp, 1);
       res2[i] = sub(res2[i], extract_h(L_temp));
   }

   return 0;
}

------------------------------------------------------------------------------
 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]

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

void cl_ltp(
    clLtpState *clSt,    /* i/o : State struct                              */
    tonStabState *tonSt, /* i/o : State struct                              */
    enum Mode mode,      /* i   : coder mode                                */
    Word16 frameOffset,  /* i   : Offset to subframe                        */
    Word16 T_op[],       /* i   : Open loop pitch lags                      */
    Word16 *h1,          /* i   : Impulse response vector               Q12 */
    Word16 *exc,         /* i/o : Excitation vector                      Q0 */
    Word16 res2[],       /* i/o : Long term prediction residual          Q0 */
    Word16 xn[],         /* i   : Target vector for pitch search         Q0 */
    Word16 lsp_flag,     /* i   : LSP resonance flag                        */
    Word16 xn2[],        /* o   : Target vector for codebook search      Q0 */
    Word16 yl[],         /* o   : Filtered adaptive excitation           Q0 */
    Word16 *T0,          /* o   : Pitch delay (integer part)                */
    Word16 *T0_frac,     /* o   : Pitch delay (fractional part)             */
    Word16 *gain_pit,    /* o   : Pitch gain                            Q14 */
    Word16 g_coeff[],    /* o   : Correlations between xn, y1, & y2         */
    Word16 **anap,       /* o   : Analysis parameters                       */
    Word16 *gp_limit,    /* o   : pitch gain limit                          */
    Flag   *pOverflow    /* o   : overflow indicator                        */
)
{
    register Word16 i;
    Word16 index;
    Word32 L_temp;     /* temporarily variable */
    Word16 resu3;      /* flag for upsample resolution */
    Word16 gpc_flag;

    Word16 temp;
    Word16 *p_exc;
    Word16 *p_xn;
    Word16 *p_xn2;
    Word16 *p_yl;

    /*----------------------------------------------------------------------*
     *                 Closed-loop fractional pitch search                  *
     *----------------------------------------------------------------------*/
    *T0 =
        Pitch_fr(
            clSt->pitchSt,
            mode,
            T_op,
            exc,
            xn,
            h1,
            L_SUBFR,
            frameOffset,
            T0_frac,
            &resu3,
            &index,
            pOverflow);

    *(*anap)++ = index;

    /*-----------------------------------------------------------------*
     *   - find unity gain pitch excitation (adapitve codebook entry)  *
     *     with fractional interpolation.                              *
     *   - find filtered pitch exc. y1[]=exc[] convolve with h1[])     *
     *   - compute pitch gain and limit between 0 and 1.2              *
     *   - update target vector for codebook search                    *
     *   - find LTP residual.                                          *
     *-----------------------------------------------------------------*/

    Pred_lt_3or6(
        exc,
        *T0,
        *T0_frac,
        L_SUBFR,
        resu3,
        pOverflow);

    Convolve(exc, h1, yl, L_SUBFR);

    /* gain_pit is Q14 for all modes */
    *gain_pit =
        G_pitch(
            mode,
            xn,
            yl,
            g_coeff,
            L_SUBFR,
            pOverflow);


    /* check if the pitch gain should be limit due to resonance in LPC filter */
    gpc_flag = 0;
    *gp_limit = MAX_16;

    if ((lsp_flag != 0) && ((Word32)(*gain_pit) > GP_CLIP))
    {
        gpc_flag = check_gp_clipping(tonSt, *gain_pit, pOverflow);
    }

    /* special for the MR475, MR515 mode; limit the gain to 0.85 to */
    /* cope with bit errors in the decoder in a better way.         */

    if ((mode == MR475) || (mode == MR515))
    {
        *gain_pit = ((Word32) * gain_pit > 13926) ? 13926 : *gain_pit;

        if (gpc_flag != 0)
        {
            *gp_limit = GP_CLIP;
        }
    }
    else
    {
        if (gpc_flag != 0)
        {
            *gp_limit = GP_CLIP;
            *gain_pit = GP_CLIP;
        }
        /* For MR122, gain_pit is quantized here and not in gainQuant */
        if (mode == MR122)
        {
            *(*anap)++ =
                q_gain_pitch(
                    MR122,
                    *gp_limit,
                    gain_pit,
                    NULL,
                    NULL,
                    pOverflow);
        }
    }


    p_exc  = &exc[0];
    p_xn   =  &xn[0];
    p_xn2  = &xn2[0];
    p_yl   =  &yl[0];

    temp = *gain_pit;

    /* update target vector und evaluate LTP residual */
    for (i = 0; i < L_SUBFR; i++)
    {
        L_temp = ((Word32) * (p_yl++) * temp) >> 14;
        *(p_xn2++) = *(p_xn++) - (Word16)L_temp;

        L_temp   = ((Word32) * (p_exc++) * temp) >> 14;
        res2[i] -= (Word16)L_temp;
    }

}