dec_gain.c

arm音频编解码库

/*
********************************************************************************
*
*      GSM AMR-NB speech codec   R98   Version 7.6.0   December 12, 2001
*                                R99   Version 3.3.0                
*                                REL-4 Version 4.1.0                
*
********************************************************************************
*
*      File             : dec_gain.c
*      Purpose          : Decode the pitch and codebook gains
*
********************************************************************************
*/

/*
********************************************************************************
*                         MODULE INCLUDE FILE AND VERSION ID
********************************************************************************
*/
#include "dec_gain.h"
const char dec_gain_id[] = "@(#)$Id $" dec_gain_h;
 
/*
********************************************************************************
*                         INCLUDE FILES
********************************************************************************
*/
#include <stdlib.h>
#include <stdio.h>
#include "typedef.h"
#include "basic_op.h"
#include "oper_32b.h"
#include "count.h"
#include "mode.h"
#include "cnst.h"
#include "pow2.h"
#include "log2.h"
#include "gc_pred.h"

/*
********************************************************************************
*                         LOCAL VARIABLES AND TABLES
********************************************************************************
*/

#include "qua_gain.tab"
#include "qgain475.tab"

/*
********************************************************************************
*                         PUBLIC PROGRAM CODE
********************************************************************************
*/

/*************************************************************************
 *
 *   FUNCTION:  Dec_gain()
 *
 *   PURPOSE: Decode the pitch and codebook gains
 *
 ************************************************************************/
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.                   */
)
{
    const Word16 *p;
    Word16 frac, gcode0, exp, qua_ener, qua_ener_MR122;
    Word16 g_code;
    Word32 L_tmp;
    
    /* Read the quantized gains (table depends on mode) */
    index = shl (index, 2);
    
    test(); test(); test();
    if (    sub (mode, MR102) == 0
         || sub (mode, MR74) == 0
         || sub (mode, MR67) == 0)
    {
        p = &table_gain_highrates[index];                  move16 ();
        
        *gain_pit = *p++;                                  move16 ();
        g_code = *p++;                                     move16 ();
        qua_ener_MR122 = *p++;                             move16 ();
        qua_ener = *p;                                     move16 ();
    }
    else
    {
        test();
        if (sub (mode, MR475) == 0)
        {
            index = add (index, shl(sub(1, evenSubfr), 1));
            p = &table_gain_MR475[index];                  move16 ();
            
            *gain_pit = *p++;                              move16 ();
            g_code = *p++;                                 move16 ();
            
            /*---------------------------------------------------------*
             *  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 */
            Log2 (L_deposit_l (g_code), &exp, &frac); 
            exp = sub(exp, 12);
    
            qua_ener_MR122 = add (shr_r (frac, 5), shl (exp, 10));
    
            /* 24660 Q12 ~= 6.0206 = 20*log10(2) */
            L_tmp = Mpy_32_16(exp, frac, 24660);
            qua_ener = round (L_shl (L_tmp, 13)); /* Q12 * Q0 = Q13 -> Q10 */
        }
        else
        {
            p = &table_gain_lowrates[index];                move16 ();
            
            *gain_pit = *p++;                               move16 ();
            g_code = *p++;                                  move16 ();
            qua_ener_MR122 = *p++;                          move16 ();
            qua_ener = *p;                                  move16 ();
        }
    }
    
    /*-------------------------------------------------------------------*
     *  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);

    gcode0 = extract_l(Pow2(14, frac));

    /*------------------------------------------------------------------*
     *  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);
    L_tmp = L_shr(L_tmp, sub(10, exp));
    *gain_cod = extract_h(L_tmp);

    /* update table of past quantized energies */

    gc_pred_update(pred_state, qua_ener_MR122, qua_ener);

    return;
}