d8_31pf.cpp

实现3GPP的GSM中AMR语音的CODECS。

                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]

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

static void decompress_code(
    Word16 indx[],      /* i : position and sign of 8 pulses (compressed) */
    Word16 sign_indx[], /* o : signs of 4 pulses (signs only)             */
    Word16 pos_indx[],  /* o : position index of 8 pulses (position only) */
    Flag  *pOverflow    /* o : Flag set when overflow occurs              */
)
{
    Word16 i;
    Word16 ia;
    Word16 ib;
    Word16 MSBs;
    Word16 LSBs;
    Word16 MSBs0_24;
    Word32 tempWord32;

    for (i = 0; i < NB_TRACK_MR102; i++)
    {
        sign_indx[i] = indx[i];
    }

    /*
      First index: 10x10x10 -> 2x5x2x5x2x5-> 125x2x2x2 -> 7+1x3 bits
      MSBs = indx[NB_TRACK]/8;
      LSBs = indx[NB_TRACK]%8;
      */
    MSBs =
        shr(
            indx[NB_TRACK_MR102],
            3,
            pOverflow);

    LSBs = indx[NB_TRACK_MR102] & 0x7;

    decompress10(
        MSBs,
        LSBs,
        0,
        4,
        1,
        pos_indx,
        pOverflow);

    /*
      Second index: 10x10x10 -> 2x5x2x5x2x5-> 125x2x2x2 -> 7+1x3 bits
      MSBs = indx[NB_TRACK+1]/8;
      LSBs = indx[NB_TRACK+1]%8;
      */
    MSBs =
        shr(
            indx[NB_TRACK_MR102+1],
            3,
            pOverflow);

    LSBs = indx[NB_TRACK_MR102+1] & 0x7;

    decompress10(
        MSBs,
        LSBs,
        2,
        6,
        5,
        pos_indx,
        pOverflow);

    /*
      Third index: 10x10 -> 2x5x2x5-> 25x2x2 -> 5+1x2 bits
      MSBs = indx[NB_TRACK+2]/4;
      LSBs = indx[NB_TRACK+2]%4;
      MSBs0_24 = (MSBs*25+12)/32;
      if ((MSBs0_24/5)%2==1)
         pos_indx[3] = (4-(MSBs0_24%5))*2 + LSBs%2;
      else
         pos_indx[3] = (MSBs0_24%5)*2 + LSBs%2;
      pos_indx[7] = (MSBs0_24/5)*2 + LSBs/2;
      */

    MSBs =
        shr(
            indx[NB_TRACK_MR102+2],
            2,
            pOverflow);

    LSBs = indx[NB_TRACK_MR102+2] & 0x3;

    tempWord32 =
        L_mult(
            MSBs,
            25,
            pOverflow);

    ia =
        (Word16)
        L_shr(
            tempWord32,
            1,
            pOverflow);

    ia =
        add(
            ia,
            12,
            pOverflow);


    MSBs0_24 =
        shr(
            ia,
            5,
            pOverflow);

    ia =
        mult(
            MSBs0_24,
            6554,
            pOverflow);

    ia &= 1;


    ib =
        mult(
            MSBs0_24,
            6554,
            pOverflow);

    tempWord32 =
        L_mult(
            ib,
            5,
            pOverflow);

    ib =
        (Word16)
        L_shr(
            tempWord32,
            1,
            pOverflow);

    ib =
        sub(
            MSBs0_24,
            ib,
            pOverflow);

    if (ia == 1)
    {
        ib =
            sub(
                4,
                ib,
                pOverflow);
    }


    ib =
        shl(
            ib,
            1,
            pOverflow);

    ia = LSBs & 0x1;

    pos_indx[3] =
        add(
            ib,
            ia,
            pOverflow);

    ia =
        mult(
            MSBs0_24,
            6554,
            pOverflow);

    ia =
        shl(
            ia,
            1,
            pOverflow);

    ib =
        shr(
            LSBs,
            1,
            pOverflow);

    pos_indx[7] =
        add(
            ia,
            ib,
            pOverflow);
}

/*
------------------------------------------------------------------------------
 FUNCTION NAME: dec_8i40_31bits
------------------------------------------------------------------------------
 INPUT AND OUTPUT DEFINITIONS

 Inputs:
    index   array of type Word16 --  index of 8 pulses (sign+position)

 Outputs:
    cod     array of type Word16 --  algebraic (fixed) codebook excitation
    pOverflow pointer to type Flag -- Flag set when overflow occurs

 Returns:
    None

 Global Variables Used:
    None

 Local Variables Needed:
    None

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

 PURPOSE:  Builds the innovative codevector from the received
           index of algebraic codebook.

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

 None

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

 d8_31pf.c, UMTS GSM AMR speech codec, R99 - Version 3.2.0, March 2, 2001

------------------------------------------------------------------------------
 PSEUDO-CODE


------------------------------------------------------------------------------
 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 dec_8i40_31bits(
    Word16 index[],    /* i : index of 8 pulses (sign+position)         */
    Word16 cod[],      /* o : algebraic (fixed) codebook excitation     */
    Flag  *pOverflow   /* o : Flag set when overflow occurs             */
)
{
    Word16 i;
    Word16 j;
    Word16 pos1;
    Word16 pos2;
    Word16 sign;
    Word32 tempWord32;

    Word16 linear_signs[NB_TRACK_MR102];
    Word16 linear_codewords[NB_PULSE];

    for (i = 0; i < L_CODE; i++)
    {
        cod[i] = 0;
    }

    decompress_code(
        index,
        linear_signs,
        linear_codewords,
        pOverflow);

    /* decode the positions and signs of pulses and build the codeword */
    for (j = 0; j < NB_TRACK_MR102; j++)
    {
        /* compute index i */

        i = linear_codewords[j];

        tempWord32 =
            L_mult(
                i,
                4,
                pOverflow);

        i =
            (Word16)
            L_shr(
                tempWord32,
                1,
                pOverflow);

        pos1 =
            add(
                i,
                j,
                pOverflow);   /* position of pulse "j" */

        if (linear_signs[j] == 0)
        {
            sign = POS_CODE; /* +1.0 */
        }
        else
        {
            sign = -NEG_CODE; /* -1.0 */
        }

        cod[pos1] = sign;

        /* compute index i */

        i =
            add(
                j,
                4,
                pOverflow);

        i = linear_codewords[i];

        tempWord32 =
            L_mult(
                i,
                4,
                pOverflow);

        i =
            (Word16)
            L_shr(
                tempWord32,
                1,
                pOverflow);

        pos2 =
            add(
                i,
                j,
                pOverflow);      /* position of pulse "j+4" */

        if (pos2 < pos1)
        {
            sign = negate(sign);
        }

        cod[pos2] =
            add(
                cod[pos2],
                sign,
                pOverflow);

    } /* for (j = 0; j < NB_TRACK_MR102; j++) */

    return;
}