preemph.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/preemph.c
 Functions:

     Date: 02/04/2002

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

 Description: Removed the functions preemphasis_init and preemphasis_exit.
 The preemphasis related structure is no longer dynamically allocated.
 Placed file in the appropriate PV Software Template format.

 Description: Changed to accept the pOverflow flag for EPOC compatibility.

 Description:  Replaced OSCL mem type functions and eliminated include
               files that now are chosen by OSCL definitions

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

 Description:

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

 Purpose          : Preemphasis filtering
 Description      : Filtering through 1 - g z^-1

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

/*----------------------------------------------------------------------------
; INCLUDES
----------------------------------------------------------------------------*/
#include "preemph.h"
#include "typedef.h"
#include "basic_op.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:  preemphasis_reset
------------------------------------------------------------------------------
 INPUT AND OUTPUT DEFINITIONS

 Inputs:
    st -- double pointer to preemphasisState

 Outputs:
    st -- double ponter to preemphasisState

 Returns:
    -1 if an error occurs
     0 if OK

 Global Variables Used:
    None

 Local Variables Needed:
    None

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

    Initializes state memory to zero
------------------------------------------------------------------------------
 REQUIREMENTS

 None

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

 preemph.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]

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

Word16 preemphasis_reset(preemphasisState *state)
{
    if (state == (preemphasisState *) NULL)
    {
        /* fprintf(stderr, "preemphasis_reset: invalid parameter\n"); */
        return -1;
    }

    state->mem_pre = 0;

    return 0;
}

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

 Inputs:
    st -- Pointer to preemphasisState -- preemphasis filter state
    signal -- array of type Word16 -- input signal overwritten by the output
    g -- Word16 -- preemphasis coefficient
    L -- Word16 -- size of filtering

 Outputs:
    st -- Pointer to preemphasisState -- preemphasis filter state
    signal -- array of type Word16 -- input signal overwritten by the output
    pOverflow -- pointer to type Flag -- overflow indicator
 Returns:
    None

 Global Variables Used:
    None

 Local Variables Needed:
    None

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

    Filtering through 1 - g z^-1
------------------------------------------------------------------------------
 REQUIREMENTS

 None

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

 preemph.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 preemphasis(
    preemphasisState *st, /* (i/o) : preemphasis filter state               */
    Word16 *signal,       /* (i/o) : input signal overwritten by the output */
    Word16 g,             /* (i)   : preemphasis coefficient                */
    Word16 L,             /* (i)   : size of filtering                      */
    Flag  *pOverflow      /* (o)   : overflow indicator                     */
)
{
    Word16 *p1;
    Word16 *p2;
    Word16 temp;
    Word16 temp2;
    Word16 i;

    p1 = signal + L - 1;
    p2 = p1 - 1;
    temp = *p1;

    for (i = 0; i <= L - 2; i++)
    {
        temp2 = mult(g, *(p2--), pOverflow);
        *p1 = sub(*p1, temp2, pOverflow);

        p1--;
    }

    temp2 = mult(g, st->mem_pre, pOverflow);

    *p1 = sub(*p1, temp2, pOverflow);

    st->mem_pre = temp;

    return;
}