| /* ---------------------------------------------------------------------- | |
| * Project: CMSIS DSP Library | |
| * Title: arm_rfft_f32.c | |
| * Description: RFFT & RIFFT Floating point process function | |
| * | |
| * $Date: 23 April 2021 | |
| * $Revision: V1.9.0 | |
| * | |
| * Target Processor: Cortex-M and Cortex-A cores | |
| * -------------------------------------------------------------------- */ | |
| /* | |
| * Copyright (C) 2010-2021 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. | |
| */ | |
| /* ---------------------------------------------------------------------- | |
| * 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. | |
| Source buffer is modified by this function. | |
| @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 | |
| @par | |
| For the RIFFT, the source buffer must at least have length | |
| fftLenReal + 2. | |
| The last two elements must be equal to what would be generated | |
| by the RFFT: | |
| (pSrc[0] - pSrc[1]) and 0.0f | |
| */ | |
| 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--; | |
| } | |
| } | |