/* ----------------------------------------------------------------------
* Copyright (C) 2010-2014 ARM Limited. All rights reserved.
*
* $Date: 19. March 2015
* $Revision: V.1.4.5
*
* Project: CMSIS DSP Library
* Title: arm_rfft_q31.c
*
* Description: RFFT & RIFFT Q31 process function
*
*
* Target Processor: Cortex-M4/Cortex-M3/Cortex-M0
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* - Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* - Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in
* the documentation and/or other materials provided with the
* distribution.
* - Neither the name of ARM LIMITED nor the names of its contributors
* may be used to endorse or promote products derived from this
* software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
* COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
* LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
* CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
* ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGE.
* -------------------------------------------------------------------- */
#include "arm_math.h"
/*--------------------------------------------------------------------
* Internal functions prototypes
--------------------------------------------------------------------*/
void arm_split_rfft_q31(
q31_t * pSrc,
uint32_t fftLen,
q31_t * pATable,
q31_t * pBTable,
q31_t * pDst,
uint32_t modifier);
void arm_split_rifft_q31(
q31_t * pSrc,
uint32_t fftLen,
q31_t * pATable,
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 the input buffer.
* @param[out] *pDst points to the output buffer.
* @return none.
*
* \par Input an output formats:
* \par
* 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 i;
uint32_t L2 = S->fftLenReal >> 1;
/* 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] << 1;
}
}
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 the input buffer.
* @param[in] fftLen length of FFT.
* @param[in] *pATable points to the twiddle Coef A buffer.
* @param[in] *pBTable points to the twiddle Coef B buffer.
* @param[out] *pDst points to the 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,
q31_t * pATable,
q31_t * pBTable,
q31_t * pDst,
uint32_t modifier)
{
uint32_t i; /* Loop Counter */
q31_t outR, outI; /* Temporary variables for output */
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[(4u * fftLen) - 1u];
q31_t *pIn1 = &pSrc[2], *pIn2 = &pSrc[(2u * fftLen) - 1u];
/* Init coefficient pointers */
pCoefA = &pATable[modifier * 2u];
pCoefB = &pBTable[modifier * 2u];
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 + (modifier * 2u);
pCoefA = pCoefA + ((modifier * 2u) - 1u);
i--;
}
pDst[2u * fftLen] = (pSrc[0] - pSrc[1]) >> 1;
pDst[(2u * fftLen) + 1u] = 0;
pDst[0] = (pSrc[0] + pSrc[1]) >> 1;
pDst[1] = 0;
}
/**
* @brief Core Real IFFT process
* @param[in] *pSrc points to the input buffer.
* @param[in] fftLen length of FFT.
* @param[in] *pATable points to the twiddle Coef A buffer.
* @param[in] *pBTable points to the twiddle Coef B buffer.
* @param[out] *pDst points to the 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,
q31_t * pATable,
q31_t * pBTable,
q31_t * pDst,
uint32_t modifier)
{
q31_t outR, outI; /* Temporary variables for output */
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[(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 = (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 * 2u);
pCoefA = pCoefA + ((modifier * 2u) - 1u);
/* Decrement loop count */
fftLen--;
}
}