xref: /frameworks/av/media/libstagefright/codecs/amrnb/common/src/lsp_lsf.cpp

/* ------------------------------------------------------------------
 * Copyright (C) 1998-2009 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/lsp_lsf.c
 Functions: Lsp_lsf
            Lsf_lsp

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

 Description: Updated template used to PV coding template.

 Description: Deleted variables listed in the Local Stores Needed/Modified
              section.

 Description: Synchronized file with UMTS version 3.2.0. Updated coding
              template and removed unnecessary include files.

 Description: Replaced basic_op.h with the header file of the math functions
              used in the file.

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

 Description: Placed table declarations in a .c file, rather than an included
 .tab.  The tables are now referenced via an extern in this file.

 Description:  For Lsp_lsf()
              1. Eliminated unused include file typedef.h.
              2. Replaced array addressing by pointers

 Description:  Replaced "int" and/or "char" with defined types.
               Added proper casting (Word32) to some left shifting operations

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

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

 Who:                           Date:
 Description:

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

 This file contains the functions that convert line spectral pairs (LSP) to
 line spectral frequencies (LSF) and vice-versa.

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

/*----------------------------------------------------------------------------
; INCLUDES
----------------------------------------------------------------------------*/
#include "lsp_lsf.h"
#include "basicop_malloc.h"
#include "basic_op.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 VARIABLE DEFINITIONS
    ; Variable declaration - defined here and used outside this module
    ----------------------------------------------------------------------------*/

    extern const Word16 table[];
    extern const Word16 slope[];


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

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

 Inputs:
    lsf = buffer containing normalized line spectral frequencies; valid
          range is between 0 and 0.5 (Word16)
    lsp = buffer containing line spectral pairs; valid range is between
          -1 and 1 (Word16)
    m = LPC order (Word16)

 Outputs:
    lsp contains the newly calculated line spectral pairs

 Returns:
    None

 Global Variables Used:
    table = cosine table

 Local Variables Needed:
    None

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

 This function performs the LSF to LSP transformation using the equation:

    lsf[i] = arccos(lsp[i])/(2*pi)

 The transformation from lsp[i] to lsf[i] is approximated by a look-up table
 and interpolation.

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

 None

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

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

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

void Lsf_lsp (
    Word16 lsf[],       // (i) : lsf[m] normalized (range: 0.0<=val<=0.5)
    Word16 lsp[],       // (o) : lsp[m] (range: -1<=val<1)
    Word16 m            // (i) : LPC order
)
{
    Word16 i, ind, offset;
    Word32 L_tmp;

    for (i = 0; i < m; i++)
    {
        ind = shr (lsf[i], 8);      // ind    = b8-b15 of lsf[i]
        offset = lsf[i] & 0x00ff;    // offset = b0-b7  of lsf[i]

        // lsp[i] = table[ind]+ ((table[ind+1]-table[ind])*offset) / 256

        L_tmp = L_mult (sub (table[ind + 1], table[ind]), offset);
        lsp[i] = add (table[ind], extract_l (L_shr (L_tmp, 9)));

    }
    return;
}

------------------------------------------------------------------------------
 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 Lsf_lsp(
    Word16 lsf[],       /* (i) : lsf[m] normalized (range: 0.0<=val<=0.5) */
    Word16 lsp[],       /* (o) : lsp[m] (range: -1<=val<1)                */
    Word16 m,           /* (i) : LPC order                                */
    Flag   *pOverflow   /* (o) : Flag set when overflow occurs            */
)
{
    Word16 i, ind, offset;
    Word32 L_tmp;

    for (i = 0; i < m; i++)
    {
        ind = lsf[i] >> 8;           /* ind    = b8-b15 of lsf[i] */
        offset = lsf[i] & 0x00ff;    /* offset = b0-b7  of lsf[i] */

        /* lsp[i] = table[ind]+ ((table[ind+1]-table[ind])*offset) / 256 */

        L_tmp = ((Word32)(table[ind + 1] - table[ind]) * offset) >> 8;
        lsp[i] = add(table[ind], (Word16) L_tmp, pOverflow);

    }

    return;
}

/****************************************************************************/


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

 Inputs:
    lsp = buffer containing line spectral pairs; valid range is between
          -1 and 1 (Word16)
    lsf = buffer containing normalized line spectral frequencies; valid
          range is between 0 and 0.5 (Word16)
    m = LPC order (Word16)

 Outputs:
    lsf contains the newly calculated normalized line spectral frequencies

 Returns:
    None

 Global Variables Used:
    table = cosine table
    slope = table to used to calculate inverse cosine

 Local Variables Needed:
    None

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

 This function performs the LSP to LSF transformation using the equation:

    lsp[i] = cos(2*pi*lsf[i])

 The transformation from lsf[i] to lsp[i] is approximated by a look-up table
 and interpolation.

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

 None

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

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

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

void Lsp_lsf (
    Word16 lsp[],       // (i)  : lsp[m] (range: -1<=val<1)
    Word16 lsf[],       // (o)  : lsf[m] normalized (range: 0.0<=val<=0.5)
    Word16 m            // (i)  : LPC order
)
{
    Word16 i, ind;
    Word32 L_tmp;

    ind = 63;                        // begin at end of table -1

    for (i = m - 1; i >= 0; i--)
    {
        // find value in table that is just greater than lsp[i]

        while (sub (table[ind], lsp[i]) < 0)
        {
            ind--;

        }

        // acos(lsp[i])= ind*256 + ( ( lsp[i]-table[ind] ) *
           slope[ind] )/4096

        L_tmp = L_mult (sub (lsp[i], table[ind]), slope[ind]);
        //(lsp[i]-table[ind])*slope[ind])>>12
        lsf[i] = pv_round (L_shl (L_tmp, 3));
        lsf[i] = add (lsf[i], shl (ind, 8));
    }
    return;
}

------------------------------------------------------------------------------
 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 Lsp_lsf(
    Word16 lsp[],       /* (i)  : lsp[m] (range: -1<=val<1)                */
    Word16 lsf[],       /* (o)  : lsf[m] normalized (range: 0.0<=val<=0.5) */
    Word16 m,           /* (i)  : LPC order                                */
    Flag  *pOverflow    /* (o)  : Flag set when overflow occurs            */
)
{
    Word16 i;
    Word16 ind;
    Word16 temp;
    Word32 L_tmp;
    Word16 *p_lsp = &lsp[m-1];
    Word16 *p_lsf = &lsf[m-1];
    OSCL_UNUSED_ARG(pOverflow);

    ind = 63;                        /* begin at end of table -1 */

    for (i = m - 1; i >= 0; i--)
    {
        /* find value in table that is just greater than lsp[i] */
        temp = *(p_lsp--);
        while (table[ind] < temp)
        {
            ind--;
        }

        /* acos(lsp[i])= ind*256 + ( ( lsp[i]-table[ind] ) *
           slope[ind] )/4096 */

        L_tmp = (Word32)(temp - table[ind]) * slope[ind];

        /*(lsp[i]-table[ind])*slope[ind])>>12*/
        L_tmp  = (L_tmp + 0x00000800) >> 12;

        *(p_lsf--) = (Word16)(L_tmp) + (ind << 8);
    }

    return;
}