/* ----------------------------------------------------------------------
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* Copyright (C) 2010-2014 ARM Limited. All rights reserved.
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*
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* $Date: 19. March 2015
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* $Revision: V.1.4.5
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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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*
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* Description: RFFT & RIFFT Q31 process function
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*
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*
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* Target Processor: Cortex-M4/Cortex-M3/Cortex-M0
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* - Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* - Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in
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* the documentation and/or other materials provided with the
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* distribution.
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* - Neither the name of ARM LIMITED nor the names of its contributors
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* may be used to endorse or promote products derived from this
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* software without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
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* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
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* COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
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* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
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* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
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* LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
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* CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
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* ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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* POSSIBILITY OF SUCH DAMAGE.
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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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