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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: mix_radix_fft.c
Funtions: mix_radix_fft
------------------------------------------------------------------------------
REVISION HISTORY
Description: Eliminated pointer dependency ( pData_1) on Buffer address.
Modified for-loop to countdown loops.
Description: No shift information going in/out from fft_rx4_long.
Description:
(1) Increased precision on the radix 2 fft coeff. (from Q10 to Q12)
(2) Increased precision on the input (from 0.5 to 1.0).
(3) Eliminated hardly used condition (exp = 0).
(4) Change interface to fft_rx4_long, so now the same function is
used for forward and inverse calculations.
Description: per code review comments, eliminated unnecessary headers
Who: Date:
Description:
------------------------------------------------------------------------------
INPUT AND OUTPUT DEFINITIONS
Inputs:
Data = Input vector, with quantized spectral with a pre-rotation
by exp(j(2pi/N)(k+1/8))
type Int32 *
peak_value = Input, carries the maximum value in input vector "Data"
Output, maximum value computed in the first FFT, used
to set precision on next stages
type Int32 *
Local Stores/Buffers/Pointers Needed:
None
Global Stores/Buffers/Pointers Needed:
None
Outputs:
exponent = shift factor to reflect signal scaling
Pointers and Buffers Modified:
Results are return in "Data"
Local Stores Modified:
None
Global Stores Modified:
None
------------------------------------------------------------------------------
FUNCTION DESCRIPTION
mix_radix_fft() mixes radix-2 and radix-4 FFT. This is needed to be able
to use power of 4 length when the input length sequence is a power of 2.
------------------------------------------------------------------------------
REQUIREMENTS
mix_radix_fft() should support only the FFT for the long window case of
the inverse modified cosine transform (IMDCT)
------------------------------------------------------------------------------
REFERENCES
------------------------------------------------------------------------------
PSEUDO-CODE
MODIFY( x[] )
RETURN( exponent )
------------------------------------------------------------------------------
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 "fft_rx4.h"
#include "mix_radix_fft.h"
#include "pv_normalize.h"
#include "fxp_mul32.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
----------------------------------------------------------------------------*/
#ifdef __cplusplus
extern "C"
{
#endif
void digit_reversal_swapping(Int32 *y, Int32 *x);
#ifdef __cplusplus
}
#endif
/*----------------------------------------------------------------------------
; EXTERNAL VARIABLES REFERENCES
; Declare variables used in this module but defined elsewhere
----------------------------------------------------------------------------*/
/*----------------------------------------------------------------------------
; EXTERNAL GLOBAL STORE/BUFFER/POINTER REFERENCES
; Declare variables used in this module but defined elsewhere
----------------------------------------------------------------------------*/
/*----------------------------------------------------------------------------
; FUNCTION CODE
----------------------------------------------------------------------------*/
Int mix_radix_fft(
Int32 *Data,
Int32 *peak_value
)
{
const Int32 *p_w;
Int32 *pData_1;
Int32 *pData_2;
Int32 *pData_3;
Int32 *pData_4;
Int32 exp_jw;
Int32 max1;
Int32 max2;
Int32 temp1;
Int32 temp2;
Int32 temp3;
Int32 temp4;
Int32 diff1;
Int32 diff2;
Int i;
Int exp;
max1 = *peak_value;
p_w = w_512rx2;
pData_1 = Data;
pData_3 = Data + HALF_FFT_RX4_LENGTH_FOR_LONG;
/*
* normalization to 0.9999 (0x7FFF) guarantees proper operation
*/
exp = 8 - pv_normalize(max1); /* use 24 bits for mix radix fft */
if (exp < 4)
{
exp = 4;
}
temp1 = (*pData_3);
pData_4 = pData_3 + FFT_RX4_LENGTH_FOR_LONG;
temp2 = (*pData_4++);
diff1 = (temp1 - temp2) >> exp;
*pData_3++ = (temp1 + temp2) >> exp;
temp3 = (*pData_3);
temp4 = (*pData_4);
*pData_4-- = -diff1;
*pData_3++ = (temp3 + temp4) >> exp;
*pData_4 = (temp3 - temp4) >> exp;
temp1 = (*pData_1);
pData_2 = pData_1 + FFT_RX4_LENGTH_FOR_LONG;
temp2 = (*pData_2++);
temp4 = (*pData_2);
*pData_1++ = (temp1 + temp2) >> exp;
temp3 = (*pData_1);
diff1 = (temp1 - temp2) >> exp ;
*pData_1++ = (temp3 + temp4) >> exp;
*pData_2-- = (temp3 - temp4) >> exp;
*pData_2 = diff1;
temp1 = (*pData_3);
pData_4 = pData_3 + FFT_RX4_LENGTH_FOR_LONG;
temp2 = (*pData_4++);
for (i = ONE_FOURTH_FFT_RX4_LENGTH_FOR_LONG - 1; i != 0; i--)
{
/*
* radix 2 Butterfly
*/
diff1 = (temp1 - temp2) >> (exp - 4);
*pData_3++ = (temp1 + temp2) >> exp;
temp3 = (*pData_3);
temp4 = (*pData_4);
exp_jw = *p_w++;
diff2 = (temp3 - temp4) >> (exp - 4);
*pData_3++ = (temp3 + temp4) >> exp;
*pData_4-- = -cmplx_mul32_by_16(diff1, diff2, exp_jw) >> 3;
*pData_4 = cmplx_mul32_by_16(diff2, -diff1, exp_jw) >> 3;
temp1 = (*pData_1);
pData_2 = pData_1 + FFT_RX4_LENGTH_FOR_LONG;
temp2 = (*pData_2++);
temp4 = (*pData_2);
*pData_1++ = (temp1 + temp2) >> exp;
temp3 = (*pData_1);
diff1 = (temp1 - temp2) >> (exp - 4);
diff2 = (temp3 - temp4) >> (exp - 4);
*pData_1++ = (temp3 + temp4) >> exp;
*pData_2-- = cmplx_mul32_by_16(diff2, -diff1, exp_jw) >> 3;
*pData_2 = cmplx_mul32_by_16(diff1, diff2, exp_jw) >> 3;
temp1 = (*pData_3);
pData_4 = pData_3 + FFT_RX4_LENGTH_FOR_LONG;
temp2 = (*pData_4++);
}/* for i */
fft_rx4_long(
Data,
&max1);
fft_rx4_long(
&Data[FFT_RX4_LENGTH_FOR_LONG],
&max2);
digit_reversal_swapping(Data, &Data[FFT_RX4_LENGTH_FOR_LONG]);
*peak_value = max1 | max2;
return(exp);
}
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