media/libstagefright/codecs/aacdec/fwd_short_complex_rot.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.
 * -------------------------------------------------------------------
 */
/*
 Pathname: ./src/fwd_short_complex_rot.c
 Funtions:  fwd_short_complex_rot

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

 Date: 10/18/2002
 Description:
            (1) Change the input argument, only a single max is passed.
            (2) Eliminate search for max, a fixed shift has replaced the
                search for max with minimal loss of precision.
            (3) Eliminated unused variables

 Date: 10/28/2002
 Description:
            (1) Added comments per code review
            (2) Eliminated hardly used condition on if-else (exp==0)

 Description:

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

 Inputs:

    Data_in   = Input vector (sized for short windows
                2*FWD_SHORT_CX_ROT_LENGTH elements), with freq. domain samples
                type Int32 *

    Data_out  = Output vector with a post-rotation by exp(-j(2pi/N)(k+1/8)),
                (sized for short windows 2*FWD_SHORT_CX_ROT_LENGTH)
                type Int32 *

    max       = Input, carries the maximum value of the input vector
                "Data_in"
                type Int32


 Local Stores/Buffers/Pointers Needed:
    None

 Global Stores/Buffers/Pointers Needed:
    None

 Outputs:
    exp = shift factor to reflect signal scaling

 Pointers and Buffers Modified:
    Results are return in "Data_out"

 Local Stores Modified:
    None

 Global Stores Modified:
    None
------------------------------------------------------------------------------
 FUNCTION DESCRIPTION

    fwd_short_complex_rot() performs the complex rotation for the MDCT
    for the case of short windows. It performs digit reverse ordering as well
    word normalization to ensure 16 by 16 bit multiplications.

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

    fwd_short_complex_rot() should execute a pre-rotation by
    exp(-j(2pi/N)(k+1/8)), digit reverse ordering and word normalization
------------------------------------------------------------------------------
 REFERENCES

------------------------------------------------------------------------------
 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 "fwd_short_complex_rot.h"
#include "digit_reversal_tables.h"
#include "imdct_fxp.h"
#include "pv_normalize.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
----------------------------------------------------------------------------*/

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

/*----------------------------------------------------------------------------
; EXTERNAL VARIABLES REFERENCES
; Declare variables used in this module but defined elsewhere
----------------------------------------------------------------------------*/

Int fwd_short_complex_rot(
    Int32 *Data_in,
    Int32 *Data_out,
    Int32  max)

{
    Int     i;
    Int16     I;
    const   Int16 *pTable;
    const   Int32 *p_rotate;

    Int32   *pData_in_1;
    Int     exp;
    Int32   temp_re;
    Int32   temp_im;

    Int32   cos_n;
    Int32   sin_n;
    Int32   temp_re_32;
    Int32   temp_im_32;

    Int32   *pData_in_ref;

    Int32   *pData_out_1;
    Int32   *pData_out_2;
    Int32   *pData_out_3;
    Int32   *pData_out_4;

    pTable    =  digit_reverse_64;
    p_rotate  =  exp_rotation_N_256;

    pData_in_ref  =  Data_in;

    exp = 16 - pv_normalize(max);

    if (exp < 0)
    {
        exp = 0;
    }

    pData_out_1 = Data_out;
    pData_out_2 = &Data_out[TWICE_FWD_SHORT_CX_ROT_LENGTH_m_1];
    pData_out_3 = &Data_out[TWICE_FWD_SHORT_CX_ROT_LENGTH];
    pData_out_4 = &Data_out[FOUR_FWD_SHORT_CX_ROT_LENGTH_m_1];

    /*
     *  Data_out
     *                                   >>>>                   <<<<
     *                                pData_out_3             pData_out_4
     *      |             |             |             |             |
     * pData_out_1               pData_out_2
     *      >>>>                     <<<<
     */


    for (i = FWD_SHORT_CX_ROT_LENGTH; i != 0; i--)
    {
        /*
         *   Perform digit reversal by accessing index I from table
         */

        I = *pTable++;
        pData_in_1 = pData_in_ref + I;

        /*
         * cos_n + j*sin_n == exp(j(2pi/N)(k+1/8))
         */

        sin_n = *p_rotate++;
        cos_n = sin_n >> 16;
        sin_n = sin_n & 0xFFFF;

        /*
         *  Use auxiliary variables to avoid double accesses to memory.
         *  Data in is scaled to use only lower 16 bits.
         */

        temp_re =  *(pData_in_1++) >> exp;
        temp_im =  *(pData_in_1) >> exp;

        /*
         *   Pre-rotation
         */

        temp_re_32 = (temp_re * cos_n + temp_im * sin_n) >> 16;
        temp_im_32 = (temp_im * cos_n - temp_re * sin_n) >> 16;

        *(pData_out_1++) = - temp_re_32;
        *(pData_out_2--) =   temp_im_32;
        *(pData_out_3++) = - temp_im_32;
        *(pData_out_4--) =   temp_re_32;

        /*
         *   Pointer increment to jump over imag (1 & 4) or real parts
         *   (2 & 3)
         */

        pData_out_1++;
        pData_out_2--;
        pData_out_3++;
        pData_out_4--;

    } /* for(i) */

    return (exp);
}