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/* ------------------------------------------------------------------
* 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);
}
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