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Julien Chevalley
283
Drivers/CMSIS/DSP/Source/TransformFunctions/arm_rfft_q31.c
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283
Drivers/CMSIS/DSP/Source/TransformFunctions/arm_rfft_q31.c
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/* ----------------------------------------------------------------------
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* Project: CMSIS DSP Library
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* Title: arm_rfft_q31.c
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* Description: FFT & RIFFT Q31 process function
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*
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* $Date: 27. January 2017
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* $Revision: V.1.5.1
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*
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* Target Processor: Cortex-M cores
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* -------------------------------------------------------------------- */
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/*
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* Copyright (C) 2010-2017 ARM Limited or its affiliates. All rights reserved.
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*
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* SPDX-License-Identifier: Apache-2.0
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*
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* Licensed under the Apache License, Version 2.0 (the License); you may
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* not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an AS IS BASIS, WITHOUT
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* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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#include "arm_math.h"
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/* ----------------------------------------------------------------------
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* Internal functions prototypes
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* -------------------------------------------------------------------- */
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void arm_split_rfft_q31(
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q31_t * pSrc,
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uint32_t fftLen,
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q31_t * pATable,
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q31_t * pBTable,
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q31_t * pDst,
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uint32_t modifier);
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void arm_split_rifft_q31(
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q31_t * pSrc,
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uint32_t fftLen,
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q31_t * pATable,
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q31_t * pBTable,
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q31_t * pDst,
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uint32_t modifier);
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/**
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* @addtogroup RealFFT
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* @{
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*/
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/**
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* @brief Processing function for the Q31 RFFT/RIFFT.
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* @param[in] *S points to an instance of the Q31 RFFT/RIFFT structure.
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* @param[in] *pSrc points to the input buffer.
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* @param[out] *pDst points to the output buffer.
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* @return none.
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*
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* \par Input an output formats:
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* \par
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* Internally input is downscaled by 2 for every stage to avoid saturations inside CFFT/CIFFT process.
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* Hence the output format is different for different RFFT sizes.
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* 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:
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* \par
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* \image html RFFTQ31.gif "Input and Output Formats for Q31 RFFT"
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*
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* \par
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* \image html RIFFTQ31.gif "Input and Output Formats for Q31 RIFFT"
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*/
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void arm_rfft_q31(
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const arm_rfft_instance_q31 * S,
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q31_t * pSrc,
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q31_t * pDst)
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{
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const arm_cfft_instance_q31 *S_CFFT = S->pCfft;
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uint32_t i;
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uint32_t L2 = S->fftLenReal >> 1;
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/* Calculation of RIFFT of input */
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if (S->ifftFlagR == 1U)
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{
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/* Real IFFT core process */
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arm_split_rifft_q31(pSrc, L2, S->pTwiddleAReal,
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S->pTwiddleBReal, pDst, S->twidCoefRModifier);
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/* Complex IFFT process */
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arm_cfft_q31(S_CFFT, pDst, S->ifftFlagR, S->bitReverseFlagR);
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for(i=0;i<S->fftLenReal;i++)
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{
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pDst[i] = pDst[i] << 1;
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}
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}
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else
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{
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/* Calculation of RFFT of input */
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/* Complex FFT process */
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arm_cfft_q31(S_CFFT, pSrc, S->ifftFlagR, S->bitReverseFlagR);
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/* Real FFT core process */
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arm_split_rfft_q31(pSrc, L2, S->pTwiddleAReal,
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S->pTwiddleBReal, pDst, S->twidCoefRModifier);
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}
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}
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/**
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* @} end of RealFFT group
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*/
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/**
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* @brief Core Real FFT process
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* @param[in] *pSrc points to the input buffer.
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* @param[in] fftLen length of FFT.
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* @param[in] *pATable points to the twiddle Coef A buffer.
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* @param[in] *pBTable points to the twiddle Coef B buffer.
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* @param[out] *pDst points to the output buffer.
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* @param[in] modifier twiddle coefficient modifier that supports different size FFTs with the same twiddle factor table.
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* @return none.
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*/
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void arm_split_rfft_q31(
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q31_t * pSrc,
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uint32_t fftLen,
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q31_t * pATable,
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q31_t * pBTable,
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q31_t * pDst,
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uint32_t modifier)
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{
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uint32_t i; /* Loop Counter */
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q31_t outR, outI; /* Temporary variables for output */
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q31_t *pCoefA, *pCoefB; /* Temporary pointers for twiddle factors */
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q31_t CoefA1, CoefA2, CoefB1; /* Temporary variables for twiddle coefficients */
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q31_t *pOut1 = &pDst[2], *pOut2 = &pDst[(4U * fftLen) - 1U];
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q31_t *pIn1 = &pSrc[2], *pIn2 = &pSrc[(2U * fftLen) - 1U];
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/* Init coefficient pointers */
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pCoefA = &pATable[modifier * 2U];
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pCoefB = &pBTable[modifier * 2U];
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i = fftLen - 1U;
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while (i > 0U)
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{
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/*
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outR = (pSrc[2 * i] * pATable[2 * i] - pSrc[2 * i + 1] * pATable[2 * i + 1]
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+ pSrc[2 * n - 2 * i] * pBTable[2 * i] +
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pSrc[2 * n - 2 * i + 1] * pBTable[2 * i + 1]);
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*/
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/* outI = (pIn[2 * i + 1] * pATable[2 * i] + pIn[2 * i] * pATable[2 * i + 1] +
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pIn[2 * n - 2 * i] * pBTable[2 * i + 1] -
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pIn[2 * n - 2 * i + 1] * pBTable[2 * i]); */
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CoefA1 = *pCoefA++;
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CoefA2 = *pCoefA;
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/* outR = (pSrc[2 * i] * pATable[2 * i] */
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mult_32x32_keep32_R(outR, *pIn1, CoefA1);
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/* outI = pIn[2 * i] * pATable[2 * i + 1] */
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mult_32x32_keep32_R(outI, *pIn1++, CoefA2);
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/* - pSrc[2 * i + 1] * pATable[2 * i + 1] */
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multSub_32x32_keep32_R(outR, *pIn1, CoefA2);
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/* (pIn[2 * i + 1] * pATable[2 * i] */
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multAcc_32x32_keep32_R(outI, *pIn1++, CoefA1);
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/* pSrc[2 * n - 2 * i] * pBTable[2 * i] */
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multSub_32x32_keep32_R(outR, *pIn2, CoefA2);
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CoefB1 = *pCoefB;
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/* pIn[2 * n - 2 * i] * pBTable[2 * i + 1] */
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multSub_32x32_keep32_R(outI, *pIn2--, CoefB1);
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/* pSrc[2 * n - 2 * i + 1] * pBTable[2 * i + 1] */
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multAcc_32x32_keep32_R(outR, *pIn2, CoefB1);
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/* pIn[2 * n - 2 * i + 1] * pBTable[2 * i] */
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multSub_32x32_keep32_R(outI, *pIn2--, CoefA2);
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/* write output */
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*pOut1++ = outR;
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*pOut1++ = outI;
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/* write complex conjugate output */
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*pOut2-- = -outI;
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*pOut2-- = outR;
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/* update coefficient pointer */
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pCoefB = pCoefB + (modifier * 2U);
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pCoefA = pCoefA + ((modifier * 2U) - 1U);
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i--;
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}
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pDst[2U * fftLen] = (pSrc[0] - pSrc[1]) >> 1;
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pDst[(2U * fftLen) + 1U] = 0;
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pDst[0] = (pSrc[0] + pSrc[1]) >> 1;
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pDst[1] = 0;
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}
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/**
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* @brief Core Real IFFT process
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* @param[in] *pSrc points to the input buffer.
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* @param[in] fftLen length of FFT.
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* @param[in] *pATable points to the twiddle Coef A buffer.
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* @param[in] *pBTable points to the twiddle Coef B buffer.
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* @param[out] *pDst points to the output buffer.
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* @param[in] modifier twiddle coefficient modifier that supports different size FFTs with the same twiddle factor table.
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* @return none.
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*/
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void arm_split_rifft_q31(
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q31_t * pSrc,
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uint32_t fftLen,
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q31_t * pATable,
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q31_t * pBTable,
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q31_t * pDst,
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uint32_t modifier)
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{
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q31_t outR, outI; /* Temporary variables for output */
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q31_t *pCoefA, *pCoefB; /* Temporary pointers for twiddle factors */
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q31_t CoefA1, CoefA2, CoefB1; /* Temporary variables for twiddle coefficients */
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q31_t *pIn1 = &pSrc[0], *pIn2 = &pSrc[(2U * fftLen) + 1U];
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pCoefA = &pATable[0];
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pCoefB = &pBTable[0];
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while (fftLen > 0U)
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{
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/*
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outR = (pIn[2 * i] * pATable[2 * i] + pIn[2 * i + 1] * pATable[2 * i + 1] +
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pIn[2 * n - 2 * i] * pBTable[2 * i] -
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pIn[2 * n - 2 * i + 1] * pBTable[2 * i + 1]);
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outI = (pIn[2 * i + 1] * pATable[2 * i] - pIn[2 * i] * pATable[2 * i + 1] -
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pIn[2 * n - 2 * i] * pBTable[2 * i + 1] -
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pIn[2 * n - 2 * i + 1] * pBTable[2 * i]);
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*/
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CoefA1 = *pCoefA++;
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CoefA2 = *pCoefA;
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/* outR = (pIn[2 * i] * pATable[2 * i] */
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mult_32x32_keep32_R(outR, *pIn1, CoefA1);
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/* - pIn[2 * i] * pATable[2 * i + 1] */
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mult_32x32_keep32_R(outI, *pIn1++, -CoefA2);
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/* pIn[2 * i + 1] * pATable[2 * i + 1] */
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multAcc_32x32_keep32_R(outR, *pIn1, CoefA2);
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/* pIn[2 * i + 1] * pATable[2 * i] */
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multAcc_32x32_keep32_R(outI, *pIn1++, CoefA1);
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/* pIn[2 * n - 2 * i] * pBTable[2 * i] */
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multAcc_32x32_keep32_R(outR, *pIn2, CoefA2);
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CoefB1 = *pCoefB;
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/* pIn[2 * n - 2 * i] * pBTable[2 * i + 1] */
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multSub_32x32_keep32_R(outI, *pIn2--, CoefB1);
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/* pIn[2 * n - 2 * i + 1] * pBTable[2 * i + 1] */
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multAcc_32x32_keep32_R(outR, *pIn2, CoefB1);
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/* pIn[2 * n - 2 * i + 1] * pBTable[2 * i] */
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multAcc_32x32_keep32_R(outI, *pIn2--, CoefA2);
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/* write output */
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*pDst++ = outR;
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*pDst++ = outI;
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/* update coefficient pointer */
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pCoefB = pCoefB + (modifier * 2U);
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pCoefA = pCoefA + ((modifier * 2U) - 1U);
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/* Decrement loop count */
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fftLen--;
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}
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}
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