d_gain_p.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/d_gain_p.c
 Functions: d_gain_p

     Date: 01/31/2002

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

 Description:
 (1) Removed extra includes
 (2) Replaced function calls to basic math operations with ANSI C standard
     mathemtical operations.
 (3) Placed code in the proper software template.

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

 Description: Added #ifdef __cplusplus around extern'ed table.

 Description:

 ------------------------------------------------------------------------------
 INPUT AND OUTPUT DEFINITIONS

 Inputs:
    mode  -- enumerated type -- AMR mode
    index -- Word16          -- index of quantization
 Outputs:
    None

 Returns:
    Word16 gain -- (Q14)

 Global Variables Used:
    None

 Local Variables Needed:
    None

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

 Function    : d_gain_pitch
 Purpose     : Decodes the pitch gain using the received index.
               output is in Q14

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



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

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

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



------------------------------------------------------------------------------
 RESOURCES USED
   When the code is written for a specific target processor the
     the resources used should be documented below.

 STACK USAGE: [stack count for this module] + [variable to represent
          stack usage for each subroutine called]

     where: [stack usage variable] = stack usage for [subroutine
         name] (see [filename].ext)

 DATA MEMORY USED: x words

 PROGRAM MEMORY USED: x words

 CLOCK CYCLES: [cycle count equation for this module] + [variable
           used to represent cycle count for each subroutine
           called]

     where: [cycle count variable] = cycle count for [subroutine
        name] (see [filename].ext)

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


/*----------------------------------------------------------------------------
; INCLUDES
----------------------------------------------------------------------------*/
#include "d_gain_p.h"
#include "typedef.h"
#include "mode.h"

/*--------------------------------------------------------------------------*/
#ifdef __cplusplus
extern "C"
{
#endif

    /*----------------------------------------------------------------------------
    ; 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 STORE/BUFFER/POINTER DEFINITIONS
    ; Variable declaration - defined here and used outside this module
    ----------------------------------------------------------------------------*/

    /*----------------------------------------------------------------------------
    ; EXTERNAL FUNCTION REFERENCES
    ; Declare functions defined elsewhere and referenced in this module
    ----------------------------------------------------------------------------*/

    /*----------------------------------------------------------------------------
    ; EXTERNAL GLOBAL STORE/BUFFER/POINTER REFERENCES
    ; Declare variables used in this module but defined elsewhere
    ----------------------------------------------------------------------------*/
    extern const Word16 qua_gain_pitch[];

    /*--------------------------------------------------------------------------*/
#ifdef __cplusplus
}
#endif

/*----------------------------------------------------------------------------
; FUNCTION CODE
----------------------------------------------------------------------------*/

Word16 d_gain_pitch(       /* return value: gain (Q14)                */
    enum Mode mode,        /* i   : AMR mode                          */
    Word16 index           /* i   : index of quantization             */
)
{
    Word16 gain;

    gain = qua_gain_pitch[index];

    if (mode == MR122)
    {
        /* clear 2 LSBits */
        gain &= 0xFFFC;
    }

    return gain;
}