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/* ----------------------------------------------------------------------
* Project: CMSIS DSP Library
* Title: arm_rfft_f32.c
* Description: RFFT & RIFFT Floating point process function
*
* $Date: 18. March 2019
* $Revision: V1.6.0
*
* Target Processor: Cortex-M cores
* -------------------------------------------------------------------- */
/*
* Copyright (C) 2010-2019 ARM Limited or its affiliates. All rights reserved.
*
* SPDX-License-Identifier: Apache-2.0
*
* 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
*
* 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.
*/
#include "arm_math.h"
/* ----------------------------------------------------------------------
* Internal functions prototypes
* -------------------------------------------------------------------- */
extern void arm_radix4_butterfly_f32(
float32_t * pSrc,
uint16_t fftLen,
const float32_t * pCoef,
uint16_t twidCoefModifier);
extern void arm_radix4_butterfly_inverse_f32(
float32_t * pSrc,
uint16_t fftLen,
const float32_t * pCoef,
uint16_t twidCoefModifier,
float32_t onebyfftLen);
extern void arm_bitreversal_f32(
float32_t * pSrc,
uint16_t fftSize,
uint16_t bitRevFactor,
const uint16_t * pBitRevTab);
void arm_split_rfft_f32(
float32_t * pSrc,
uint32_t fftLen,
const float32_t * pATable,
const float32_t * pBTable,
float32_t * pDst,
uint32_t modifier);
void arm_split_rifft_f32(
float32_t * pSrc,
uint32_t fftLen,
const float32_t * pATable,
const float32_t * pBTable,
float32_t * pDst,
uint32_t modifier);
/**
@ingroup groupTransforms
*/
/**
@addtogroup RealFFT
@{
*/
/**
@brief Processing function for the floating-point RFFT/RIFFT.
@deprecated Do not use this function. It has been superceded by \ref arm_rfft_fast_f32 and will be removed in the future.
@param[in] S points to an instance of the floating-point RFFT/RIFFT structure
@param[in] pSrc points to the input buffer
@param[out] pDst points to the output buffer
@return none
*/
void arm_rfft_f32(
const arm_rfft_instance_f32 * S,
float32_t * pSrc,
float32_t * pDst)
{
const arm_cfft_radix4_instance_f32 *S_CFFT = S->pCfft;
/* Calculation of Real IFFT of input */
if (S->ifftFlagR == 1U)
{
/* Real IFFT core process */
arm_split_rifft_f32 (pSrc, S->fftLenBy2, S->pTwiddleAReal, S->pTwiddleBReal, pDst, S->twidCoefRModifier);
/* Complex radix-4 IFFT process */
arm_radix4_butterfly_inverse_f32 (pDst, S_CFFT->fftLen, S_CFFT->pTwiddle, S_CFFT->twidCoefModifier, S_CFFT->onebyfftLen);
/* Bit reversal process */
if (S->bitReverseFlagR == 1U)
{
arm_bitreversal_f32 (pDst, S_CFFT->fftLen, S_CFFT->bitRevFactor, S_CFFT->pBitRevTable);
}
}
else
{
/* Calculation of RFFT of input */
/* Complex radix-4 FFT process */
arm_radix4_butterfly_f32 (pSrc, S_CFFT->fftLen, S_CFFT->pTwiddle, S_CFFT->twidCoefModifier);
/* Bit reversal process */
if (S->bitReverseFlagR == 1U)
{
arm_bitreversal_f32 (pSrc, S_CFFT->fftLen, S_CFFT->bitRevFactor, S_CFFT->pBitRevTable);
}
/* Real FFT core process */
arm_split_rfft_f32 (pSrc, S->fftLenBy2, S->pTwiddleAReal, S->pTwiddleBReal, pDst, S->twidCoefRModifier);
}
}
/**
@} end of RealFFT group
*/
/**
@brief Core Real FFT process
@param[in] pSrc points to input buffer
@param[in] fftLen length of FFT
@param[in] pATable points to twiddle Coef A buffer
@param[in] pBTable points to twiddle Coef B buffer
@param[out] pDst points to output buffer
@param[in] modifier twiddle coefficient modifier that supports different size FFTs with the same twiddle factor table
@return none
*/
void arm_split_rfft_f32(
float32_t * pSrc,
uint32_t fftLen,
const float32_t * pATable,
const float32_t * pBTable,
float32_t * pDst,
uint32_t modifier)
{
uint32_t i; /* Loop Counter */
float32_t outR, outI; /* Temporary variables for output */
const float32_t *pCoefA, *pCoefB; /* Temporary pointers for twiddle factors */
float32_t CoefA1, CoefA2, CoefB1; /* Temporary variables for twiddle coefficients */
float32_t *pDst1 = &pDst[2], *pDst2 = &pDst[(4U * fftLen) - 1U]; /* temp pointers for output buffer */
float32_t *pSrc1 = &pSrc[2], *pSrc2 = &pSrc[(2U * fftLen) - 1U]; /* temp pointers for input buffer */
/* Init coefficient pointers */
pCoefA = &pATable[modifier * 2];
pCoefB = &pBTable[modifier * 2];
i = fftLen - 1U;
while (i > 0U)
{
/*
outR = ( pSrc[2 * i] * pATable[2 * i]
- pSrc[2 * i + 1] * pATable[2 * i + 1]
+ pSrc[2 * n - 2 * i] * pBTable[2 * i]
+ pSrc[2 * n - 2 * i + 1] * pBTable[2 * i + 1]);
outI = ( pIn[2 * i + 1] * pATable[2 * i]
+ pIn[2 * i] * pATable[2 * i + 1]
+ pIn[2 * n - 2 * i] * pBTable[2 * i + 1]
- pIn[2 * n - 2 * i + 1] * pBTable[2 * i]);
*/
/* read pATable[2 * i] */
CoefA1 = *pCoefA++;
/* pATable[2 * i + 1] */
CoefA2 = *pCoefA;
/* pSrc[2 * i] * pATable[2 * i] */
outR = *pSrc1 * CoefA1;
/* pSrc[2 * i] * CoefA2 */
outI = *pSrc1++ * CoefA2;
/* (pSrc[2 * i + 1] + pSrc[2 * fftLen - 2 * i + 1]) * CoefA2 */
outR -= (*pSrc1 + *pSrc2) * CoefA2;
/* pSrc[2 * i + 1] * CoefA1 */
outI += *pSrc1++ * CoefA1;
CoefB1 = *pCoefB;
/* pSrc[2 * fftLen - 2 * i + 1] * CoefB1 */
outI -= *pSrc2-- * CoefB1;
/* pSrc[2 * fftLen - 2 * i] * CoefA2 */
outI -= *pSrc2 * CoefA2;
/* pSrc[2 * fftLen - 2 * i] * CoefB1 */
outR += *pSrc2-- * CoefB1;
/* write output */
*pDst1++ = outR;
*pDst1++ = outI;
/* write complex conjugate output */
*pDst2-- = -outI;
*pDst2-- = outR;
/* update coefficient pointer */
pCoefB = pCoefB + (modifier * 2U);
pCoefA = pCoefA + ((modifier * 2U) - 1U);
i--;
}
pDst[2U * fftLen] = pSrc[0] - pSrc[1];
pDst[(2U * fftLen) + 1U] = 0.0f;
pDst[0] = pSrc[0] + pSrc[1];
pDst[1] = 0.0f;
}
/**
@brief Core Real IFFT process
@param[in] pSrc points to input buffer
@param[in] fftLen length of FFT
@param[in] pATable points to twiddle Coef A buffer
@param[in] pBTable points to twiddle Coef B buffer
@param[out] pDst points to output buffer
@param[in] modifier twiddle coefficient modifier that supports different size FFTs with the same twiddle factor table
@return none
*/
void arm_split_rifft_f32(
float32_t * pSrc,
uint32_t fftLen,
const float32_t * pATable,
const float32_t * pBTable,
float32_t * pDst,
uint32_t modifier)
{
float32_t outR, outI; /* Temporary variables for output */
const float32_t *pCoefA, *pCoefB; /* Temporary pointers for twiddle factors */
float32_t CoefA1, CoefA2, CoefB1; /* Temporary variables for twiddle coefficients */
float32_t *pSrc1 = &pSrc[0], *pSrc2 = &pSrc[(2U * fftLen) + 1U];
pCoefA = &pATable[0];
pCoefB = &pBTable[0];
while (fftLen > 0U)
{
/*
outR = ( pIn[2 * i] * pATable[2 * i]
+ pIn[2 * i + 1] * pATable[2 * i + 1]
+ pIn[2 * n - 2 * i] * pBTable[2 * i]
- pIn[2 * n - 2 * i + 1] * pBTable[2 * i + 1]);
outI = ( pIn[2 * i + 1] * pATable[2 * i]
- pIn[2 * i] * pATable[2 * i + 1]
- pIn[2 * n - 2 * i] * pBTable[2 * i + 1]
- pIn[2 * n - 2 * i + 1] * pBTable[2 * i]);
*/
CoefA1 = *pCoefA++;
CoefA2 = *pCoefA;
/* outR = (pSrc[2 * i] * CoefA1 */
outR = *pSrc1 * CoefA1;
/* - pSrc[2 * i] * CoefA2 */
outI = -(*pSrc1++) * CoefA2;
/* (pSrc[2 * i + 1] + pSrc[2 * fftLen - 2 * i + 1]) * CoefA2 */
outR += (*pSrc1 + *pSrc2) * CoefA2;
/* pSrc[2 * i + 1] * CoefA1 */
outI += (*pSrc1++) * CoefA1;
CoefB1 = *pCoefB;
/* - pSrc[2 * fftLen - 2 * i + 1] * CoefB1 */
outI -= *pSrc2-- * CoefB1;
/* pSrc[2 * fftLen - 2 * i] * CoefB1 */
outR += *pSrc2 * CoefB1;
/* pSrc[2 * fftLen - 2 * i] * CoefA2 */
outI += *pSrc2-- * CoefA2;
/* write output */
*pDst++ = outR;
*pDst++ = outI;
/* update coefficient pointer */
pCoefB = pCoefB + (modifier * 2);
pCoefA = pCoefA + (modifier * 2 - 1);
/* Decrement loop count */
fftLen--;
}
}
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