d3_14pf.cpp

实现3GPP的GSM中AMR语音的CODECS。

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 *
 * 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
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 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either
 * express or implied.
 * See the License for the specific language governing permissions
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/****************************************************************************************
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/d3_14pf.c
 Functions: decode_3i40_14bits

     Date: 01/28/2002

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

 Description: Modified to place file in the correct template format. Eliminated
 use of special functions to perform simple mathematical operations.

 Description: Per review comments...
 (1) Removed include of "count.h" and "basic_op.h"
 (2) Updated the pathname to indicate the correct file.  (Line 39)

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

 Description:

------------------------------------------------------------------------------
 MODULE DESCRIPTION


 FUNCTION:  decode_3i40_14bits (decod_ACELP())

 PURPOSE:   Algebraic codebook decoder. For details about the encoding see
            c3_14pf.c
*/

/*----------------------------------------------------------------------------
; INCLUDES
----------------------------------------------------------------------------*/
#include "typedef.h"
#include "cnst.h"
#include "d3_14pf.h"

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

/*----------------------------------------------------------------------------
; DEFINES
; Include all pre-processor statements here. Include conditional
; compile variables also.
----------------------------------------------------------------------------*/
#define NB_PULSE 3           /* number of pulses  */


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

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

/*
------------------------------------------------------------------------------
 FUNCTION NAME: decode_3i40_14bits
------------------------------------------------------------------------------
 INPUT AND OUTPUT DEFINITIONS

 Inputs:
    sign  -- Word16 -- signs of 3 pulses.
    index -- Word16 -- Positions of the 3 pulses.

 Outputs:
    cod[] -- array of type Word16 -- algebraic (fixed) codebook excitation

 Returns:
    None

 Global Variables Used:
    None

 Local Variables Needed:
    None

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


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

 None

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

 d2_9pf.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 decode_3i40_14bits(
    Word16 sign,   /* i : signs of 3 pulses.                       */
    Word16 index,  /* i : Positions of the 3 pulses.               */
    Word16 cod[]   /* o : algebraic (fixed) codebook excitation    */
)
{
    Word16 i;
    Word16 j;

    Word16 pos[NB_PULSE];

    /* Decode the positions */

    i = index & 0x7;

    pos[0] = i * 5;





    index >>= 3;

    j = index & 0x1;

    index >>= 1;

    i = index & 0x7;

    pos[1] = i * 5 + j * 2 + 1;





    index >>= 3;

    j = index & 0x1;

    index >>= 1;

    i = index & 0x7;

    pos[2] = i * 5 + j * 2 + 2;


    /* decode the signs  and build the codeword */

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

    for (j = 0; j < NB_PULSE; j++)
    {
        i = sign & 1;

        /* This line is equivalent to...
         *
         *
         *  if (i == 1)
         *  {
         *      cod[pos[j]] = 8191;
         *  }
         *  if (i == 0)
         *  {
         *      cod[pos[j]] = -8192;
         *  }
         */

        cod[pos[j]] = i * 16383 - 8192;

        sign >>= 1;

    }

    return;
}