dec_gain.cpp

实现3GPP的GSM中AMR语音的CODECS。

/* ------------------------------------------------------------------
 * Copyright (C) 2008 PacketVideo
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either
 * express or implied.
 * See the License for the specific language governing permissions
 * and limitations under the License.
 * -------------------------------------------------------------------
 */
/****************************************************************************************
Portions of this file are derived from the following 3GPP standard:

    3GPP TS 26.073
    ANSI-C code for the Adaptive Multi-Rate (AMR) speech codec
    Available from http://www.3gpp.org

(C) 2004, 3GPP Organizational Partners (ARIB, ATIS, CCSA, ETSI, TTA, TTC)
Permission to distribute, modify and use this file under the standard license
terms listed above has been obtained from the copyright holder.
****************************************************************************************/
/*
------------------------------------------------------------------------------



 Pathname: ./audio/gsm-amr/c/src/dec_gain.c
 Funtions: dec_gain

     Date: 01/31/2002

------------------------------------------------------------------------------
 REVISION HISTORY

 Description: Updating include file lists, and other things as per review
              comments.

 Description: Added fixes to the code as per review comments. Removed nested
              function calls and declared temp2 as a variable.

 Description: A Word32 was being stored improperly in a Word16.

 Description: Removed qua_gain.tab and qgain475.tab from Include section and
              added qua_gain_tbl.h and qgain475_tab.h to Include section.

 Description: Changed round function name to pv_round to avoid conflict with
              round function in C standard library.

 Description:  Added casting to eliminate warnings

 Description:  Replaced "int" and/or "char" with OSCL defined types.

 Description:

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


/*----------------------------------------------------------------------------
; INCLUDES
----------------------------------------------------------------------------*/

#include "dec_gain.h"
#include "typedef.h"
//#include "stdlib.h"
#include "mode.h"
#include "cnst.h"
#include "pow2.h"
#include "log2.h"
#include "gc_pred.h"
#include "basic_op.h"
#include "qua_gain_tbl.h"
#include "qgain475_tab.h"

/*----------------------------------------------------------------------------
; MACROS
; Define module specific macros here
----------------------------------------------------------------------------*/


/*----------------------------------------------------------------------------
; DEFINES
; Include all pre-processor statements here. Include conditional
; compile variables also.
----------------------------------------------------------------------------*/

/*----------------------------------------------------------------------------
; LOCAL FUNCTION DEFINITIONS
; Function Prototype declaration
----------------------------------------------------------------------------*/

/*----------------------------------------------------------------------------
; LOCAL VARIABLE DEFINITIONS
; Variable declaration - defined here and used outside this module
----------------------------------------------------------------------------*/

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

 Inputs:
    pred_state = pointer to MA predictor state of type gc_predState
    index = AMR mode of type enum Mode
    code[] = pointer to innovative vector of type Word16
    evenSubfr = Flag for even subframes of type Word16
    pOverflow = pointer to overflow flag


 Outputs:
    pred_state = pointer to MA predictor state of type gc_predState
    gain_pit = pointer to pitch gain of type Word16
    gain_cod = pointer to code gain of type Word16

 Returns:
    None.

 Global Variables Used:
    None.

 Local Variables Needed:
    None.

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

      File             : dec_gain.c
      Purpose          : Decode the pitch and codebook gains

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

 None.

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

 agc.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_gain(
    gc_predState *pred_state, /* i/o: MA predictor state           */
    enum Mode mode,           /* i  : AMR mode                     */
    Word16 index,             /* i  : index of quantization.       */
    Word16 code[],            /* i  : Innovative vector.           */
    Word16 evenSubfr,         /* i  : Flag for even subframes      */
    Word16 * gain_pit,        /* o  : Pitch gain.                  */
    Word16 * gain_cod,        /* o  : Code gain.                   */
    Flag   * pOverflow
)
{
    const Word16 *p;
    Word16 frac;
    Word16 gcode0;
    Word16 exp;
    Word16 qua_ener;
    Word16 qua_ener_MR122;
    Word16 g_code;
    Word32 L_tmp;
    Word16 temp1;
    Word16 temp2;

    /* Read the quantized gains (table depends on mode) */
    index = shl(index, 2, pOverflow);

    if (mode == MR102 || mode == MR74 || mode == MR67)
    {
        p = &table_gain_highrates[index];

        *gain_pit = *p++;
        g_code = *p++;
        qua_ener_MR122 = *p++;
        qua_ener = *p;
    }
    else
    {
        if (mode == MR475)
        {
            temp1 = sub(1, evenSubfr, pOverflow);
            temp2 = shl(temp1, 1, pOverflow);
            index = add(index, temp2, pOverflow);
            p = &table_gain_MR475[index];

            *gain_pit = *p++;
            g_code = *p++;

            /*---------------------------------------------------------*
             *  calculate predictor update values (not stored in 4.75  *
             *  quantizer table to save space):                        *
             *  ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  *
             *                                                         *
             *   qua_ener       = log2(g)                              *
             *   qua_ener_MR122 = 20*log10(g)                          *
             *---------------------------------------------------------*/

            /* Log2(x Q12) = log2(x) + 12 */
            temp1 = (Word16) L_deposit_l(g_code);
            Log2(temp1, &exp, &frac, pOverflow);
            exp = sub(exp, 12, pOverflow);

            temp1 = shr_r(frac, 5, pOverflow);
            temp2 = shl(exp, 10, pOverflow);
            qua_ener_MR122 = add(temp1, temp2, pOverflow);

            /* 24660 Q12 ~= 6.0206 = 20*log10(2) */
            L_tmp = Mpy_32_16(exp, frac, 24660, pOverflow);
            L_tmp = L_shl(L_tmp, 13, pOverflow);
            qua_ener = pv_round(L_tmp, pOverflow);
            /* Q12 * Q0 = Q13 -> Q10 */
        }
        else
        {
            p = &table_gain_lowrates[index];

            *gain_pit = *p++;
            g_code = *p++;
            qua_ener_MR122 = *p++;
            qua_ener = *p;
        }
    }

    /*-------------------------------------------------------------------*
     *  predict codebook gain                                            *
     *  ~~~~~~~~~~~~~~~~~~~~~                                            *
     *  gc0     = Pow2(int(d)+frac(d))                                   *
     *          = 2^exp + 2^frac                                         *
     *                                                                   *
     *  gcode0 (Q14) = 2^14*2^frac = gc0 * 2^(14-exp)                    *
     *-------------------------------------------------------------------*/

    gc_pred(pred_state, mode, code, &exp, &frac, NULL, NULL, pOverflow);

    gcode0 = (Word16) Pow2(14, frac, pOverflow);

    /*------------------------------------------------------------------*
     *  read quantized gains, update table of past quantized energies   *
     *  ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~   *
     *  st->past_qua_en(Q10) = 20 * Log10(g_fac) / constant             *
     *                       = Log2(g_fac)                              *
     *                       = qua_ener                                 *
     *                                           constant = 20*Log10(2) *
     *------------------------------------------------------------------*/

    L_tmp = L_mult(g_code, gcode0, pOverflow);
    temp1 = sub(10, exp, pOverflow);
    L_tmp = L_shr(L_tmp, temp1, pOverflow);
    *gain_cod = extract_h(L_tmp);

    /* update table of past quantized energies */

    gc_pred_update(pred_state, qua_ener_MR122, qua_ener);

    return;
}