| /* ---------------------------------------------------------------------- |
| * Project: CMSIS DSP Library |
| * Title: arm_rfft_q31.c |
| * Description: FFT & RIFFT Q31 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 |
| * -------------------------------------------------------------------- */ |
| |
| void arm_split_rfft_q31( |
| q31_t * pSrc, |
| uint32_t fftLen, |
| const q31_t * pATable, |
| const q31_t * pBTable, |
| q31_t * pDst, |
| uint32_t modifier); |
| |
| void arm_split_rifft_q31( |
| q31_t * pSrc, |
| uint32_t fftLen, |
| const q31_t * pATable, |
| const q31_t * pBTable, |
| q31_t * pDst, |
| uint32_t modifier); |
| |
| /** |
| @addtogroup RealFFT |
| @{ |
| */ |
| |
| /** |
| @brief Processing function for the Q31 RFFT/RIFFT. |
| @param[in] S points to an instance of the Q31 RFFT/RIFFT structure |
| @param[in] pSrc points to input buffer |
| @param[out] pDst points to output buffer |
| @return none |
| |
| @par Input an output formats |
| Internally input is downscaled by 2 for every stage to avoid saturations inside CFFT/CIFFT process. |
| Hence the output format is different for different RFFT sizes. |
| The input and output formats for different RFFT sizes and number of bits to upscale are mentioned in the tables below for RFFT and RIFFT: |
| @par |
| \image html RFFTQ31.gif "Input and Output Formats for Q31 RFFT" |
| @par |
| \image html RIFFTQ31.gif "Input and Output Formats for Q31 RIFFT" |
| */ |
| |
| void arm_rfft_q31( |
| const arm_rfft_instance_q31 * S, |
| q31_t * pSrc, |
| q31_t * pDst) |
| { |
| const arm_cfft_instance_q31 *S_CFFT = S->pCfft; |
| uint32_t L2 = S->fftLenReal >> 1U; |
| uint32_t i; |
| |
| /* Calculation of RIFFT of input */ |
| if (S->ifftFlagR == 1U) |
| { |
| /* Real IFFT core process */ |
| arm_split_rifft_q31 (pSrc, L2, S->pTwiddleAReal, S->pTwiddleBReal, pDst, S->twidCoefRModifier); |
| |
| /* Complex IFFT process */ |
| arm_cfft_q31 (S_CFFT, pDst, S->ifftFlagR, S->bitReverseFlagR); |
| |
| for(i = 0; i < S->fftLenReal; i++) |
| { |
| pDst[i] = pDst[i] << 1U; |
| } |
| } |
| else |
| { |
| /* Calculation of RFFT of input */ |
| |
| /* Complex FFT process */ |
| arm_cfft_q31 (S_CFFT, pSrc, S->ifftFlagR, S->bitReverseFlagR); |
| |
| /* Real FFT core process */ |
| arm_split_rfft_q31 (pSrc, L2, 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_q31( |
| q31_t * pSrc, |
| uint32_t fftLen, |
| const q31_t * pATable, |
| const q31_t * pBTable, |
| q31_t * pDst, |
| uint32_t modifier) |
| { |
| uint32_t i; /* Loop Counter */ |
| q31_t outR, outI; /* Temporary variables for output */ |
| const q31_t *pCoefA, *pCoefB; /* Temporary pointers for twiddle factors */ |
| q31_t CoefA1, CoefA2, CoefB1; /* Temporary variables for twiddle coefficients */ |
| q31_t *pOut1 = &pDst[2], *pOut2 = &pDst[4 * fftLen - 1]; |
| q31_t *pIn1 = &pSrc[2], *pIn2 = &pSrc[2 * fftLen - 1]; |
| |
| /* 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]); |
| */ |
| |
| CoefA1 = *pCoefA++; |
| CoefA2 = *pCoefA; |
| |
| /* outR = (pSrc[2 * i] * pATable[2 * i] */ |
| mult_32x32_keep32_R (outR, *pIn1, CoefA1); |
| |
| /* outI = pIn[2 * i] * pATable[2 * i + 1] */ |
| mult_32x32_keep32_R (outI, *pIn1++, CoefA2); |
| |
| /* - pSrc[2 * i + 1] * pATable[2 * i + 1] */ |
| multSub_32x32_keep32_R (outR, *pIn1, CoefA2); |
| |
| /* (pIn[2 * i + 1] * pATable[2 * i] */ |
| multAcc_32x32_keep32_R (outI, *pIn1++, CoefA1); |
| |
| /* pSrc[2 * n - 2 * i] * pBTable[2 * i] */ |
| multSub_32x32_keep32_R (outR, *pIn2, CoefA2); |
| CoefB1 = *pCoefB; |
| |
| /* pIn[2 * n - 2 * i] * pBTable[2 * i + 1] */ |
| multSub_32x32_keep32_R (outI, *pIn2--, CoefB1); |
| |
| /* pSrc[2 * n - 2 * i + 1] * pBTable[2 * i + 1] */ |
| multAcc_32x32_keep32_R (outR, *pIn2, CoefB1); |
| |
| /* pIn[2 * n - 2 * i + 1] * pBTable[2 * i] */ |
| multSub_32x32_keep32_R (outI, *pIn2--, CoefA2); |
| |
| /* write output */ |
| *pOut1++ = outR; |
| *pOut1++ = outI; |
| |
| /* write complex conjugate output */ |
| *pOut2-- = -outI; |
| *pOut2-- = outR; |
| |
| /* update coefficient pointer */ |
| pCoefB = pCoefB + (2 * modifier); |
| pCoefA = pCoefA + (2 * modifier - 1); |
| |
| /* Decrement loop count */ |
| i--; |
| } |
| |
| pDst[2 * fftLen] = (pSrc[0] - pSrc[1]) >> 1U; |
| pDst[2 * fftLen + 1] = 0; |
| |
| pDst[0] = (pSrc[0] + pSrc[1]) >> 1U; |
| pDst[1] = 0; |
| } |
| |
| |
| /** |
| @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_q31( |
| q31_t * pSrc, |
| uint32_t fftLen, |
| const q31_t * pATable, |
| const q31_t * pBTable, |
| q31_t * pDst, |
| uint32_t modifier) |
| { |
| q31_t outR, outI; /* Temporary variables for output */ |
| const q31_t *pCoefA, *pCoefB; /* Temporary pointers for twiddle factors */ |
| q31_t CoefA1, CoefA2, CoefB1; /* Temporary variables for twiddle coefficients */ |
| q31_t *pIn1 = &pSrc[0], *pIn2 = &pSrc[2 * fftLen + 1]; |
| |
| 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 = (pIn[2 * i] * pATable[2 * i] */ |
| mult_32x32_keep32_R (outR, *pIn1, CoefA1); |
| |
| /* - pIn[2 * i] * pATable[2 * i + 1] */ |
| mult_32x32_keep32_R (outI, *pIn1++, -CoefA2); |
| |
| /* pIn[2 * i + 1] * pATable[2 * i + 1] */ |
| multAcc_32x32_keep32_R (outR, *pIn1, CoefA2); |
| |
| /* pIn[2 * i + 1] * pATable[2 * i] */ |
| multAcc_32x32_keep32_R (outI, *pIn1++, CoefA1); |
| |
| /* pIn[2 * n - 2 * i] * pBTable[2 * i] */ |
| multAcc_32x32_keep32_R (outR, *pIn2, CoefA2); |
| CoefB1 = *pCoefB; |
| |
| /* pIn[2 * n - 2 * i] * pBTable[2 * i + 1] */ |
| multSub_32x32_keep32_R (outI, *pIn2--, CoefB1); |
| |
| /* pIn[2 * n - 2 * i + 1] * pBTable[2 * i + 1] */ |
| multAcc_32x32_keep32_R (outR, *pIn2, CoefB1); |
| |
| /* pIn[2 * n - 2 * i + 1] * pBTable[2 * i] */ |
| multAcc_32x32_keep32_R (outI, *pIn2--, CoefA2); |
| |
| /* write output */ |
| *pDst++ = outR; |
| *pDst++ = outI; |
| |
| /* update coefficient pointer */ |
| pCoefB = pCoefB + (modifier * 2); |
| pCoefA = pCoefA + (modifier * 2 - 1); |
| |
| /* Decrement loop count */ |
| fftLen--; |
| } |
| |
| } |
