arm_rfft_f32.c
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CLexer
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r41 | /* ---------------------------------------------------------------------- | ||
* Copyright (C) 2010 ARM Limited. All rights reserved. | ||||
* | ||||
* $Date: 15. July 2011 | ||||
* $Revision: V1.0.10 | ||||
* | ||||
* Project: CMSIS DSP Library | ||||
* Title: arm_rfft_f32.c | ||||
* | ||||
* Description: RFFT & RIFFT Floating point process function | ||||
* | ||||
* Target Processor: Cortex-M4/Cortex-M3/Cortex-M0 | ||||
* | ||||
* Version 1.0.10 2011/7/15 | ||||
* Big Endian support added and Merged M0 and M3/M4 Source code. | ||||
* | ||||
* Version 1.0.3 2010/11/29 | ||||
* Re-organized the CMSIS folders and updated documentation. | ||||
* | ||||
* Version 1.0.2 2010/11/11 | ||||
* Documentation updated. | ||||
* | ||||
* Version 1.0.1 2010/10/05 | ||||
* Production release and review comments incorporated. | ||||
* | ||||
* Version 1.0.0 2010/09/20 | ||||
* Production release and review comments incorporated. | ||||
* | ||||
* Version 0.0.7 2010/06/10 | ||||
* Misra-C changes done | ||||
* -------------------------------------------------------------------- */ | ||||
#include "arm_math.h" | ||||
/** | ||||
* @ingroup groupTransforms | ||||
*/ | ||||
/** | ||||
* @defgroup RFFT_RIFFT Real FFT Functions | ||||
* | ||||
* \par | ||||
* Complex FFT/IFFT typically assumes complex input and output. However many applications use real valued data in time domain. | ||||
* Real FFT/IFFT efficiently process real valued sequences with the advantage of requirement of low memory and with less complexity. | ||||
* | ||||
* \par | ||||
* This set of functions implements Real Fast Fourier Transforms(RFFT) and Real Inverse Fast Fourier Transform(RIFFT) | ||||
* for Q15, Q31, and floating-point data types. | ||||
* | ||||
* | ||||
* \par Algorithm: | ||||
* | ||||
* <b>Real Fast Fourier Transform:</b> | ||||
* \par | ||||
* Real FFT of N-point is calculated using CFFT of N/2-point and Split RFFT process as shown below figure. | ||||
* \par | ||||
* \image html RFFT.gif "Real Fast Fourier Transform" | ||||
* \par | ||||
* The RFFT functions operate on blocks of input and output data and each call to the function processes | ||||
* <code>fftLenR</code> samples through the transform. <code>pSrc</code> points to input array containing <code>fftLenR</code> values. | ||||
* <code>pDst</code> points to output array containing <code>2*fftLenR</code> values. \n | ||||
* Input for real FFT is in the order of | ||||
* <pre>{real[0], real[1], real[2], real[3], ..}</pre> | ||||
* Output for real FFT is complex and are in the order of | ||||
* <pre>{real(0), imag(0), real(1), imag(1), ...}</pre> | ||||
* | ||||
* <b>Real Inverse Fast Fourier Transform:</b> | ||||
* \par | ||||
* Real IFFT of N-point is calculated using Split RIFFT process and CFFT of N/2-point as shown below figure. | ||||
* \par | ||||
* \image html RIFFT.gif "Real Inverse Fast Fourier Transform" | ||||
* \par | ||||
* The RIFFT functions operate on blocks of input and output data and each call to the function processes | ||||
* <code>2*fftLenR</code> samples through the transform. <code>pSrc</code> points to input array containing <code>2*fftLenR</code> values. | ||||
* <code>pDst</code> points to output array containing <code>fftLenR</code> values. \n | ||||
* Input for real IFFT is complex and are in the order of | ||||
* <pre>{real(0), imag(0), real(1), imag(1), ...}</pre> | ||||
* Output for real IFFT is real and in the order of | ||||
* <pre>{real[0], real[1], real[2], real[3], ..}</pre> | ||||
* | ||||
* \par Lengths supported by the transform: | ||||
* \par | ||||
* Real FFT/IFFT supports the lengths [128, 512, 2048], as it internally uses CFFT/CIFFT. | ||||
* | ||||
* \par Instance Structure | ||||
* A separate instance structure must be defined for each Instance but the twiddle factors can be reused. | ||||
* There are separate instance structure declarations for each of the 3 supported data types. | ||||
* | ||||
* \par Initialization Functions | ||||
* There is also an associated initialization function for each data type. | ||||
* The initialization function performs the following operations: | ||||
* - Sets the values of the internal structure fields. | ||||
* - Initializes twiddle factor tables. | ||||
* - Initializes CFFT data structure fields. | ||||
* \par | ||||
* Use of the initialization function is optional. | ||||
* However, if the initialization function is used, then the instance structure cannot be placed into a const data section. | ||||
* To place an instance structure into a const data section, the instance structure must be manually initialized. | ||||
* Manually initialize the instance structure as follows: | ||||
* <pre> | ||||
*arm_rfft_instance_f32 S = {fftLenReal, fftLenBy2, ifftFlagR, bitReverseFlagR, twidCoefRModifier, pTwiddleAReal, pTwiddleBReal, pCfft}; | ||||
*arm_rfft_instance_q31 S = {fftLenReal, fftLenBy2, ifftFlagR, bitReverseFlagR, twidCoefRModifier, pTwiddleAReal, pTwiddleBReal, pCfft}; | ||||
*arm_rfft_instance_q15 S = {fftLenReal, fftLenBy2, ifftFlagR, bitReverseFlagR, twidCoefRModifier, pTwiddleAReal, pTwiddleBReal, pCfft}; | ||||
* </pre> | ||||
* where <code>fftLenReal</code> length of RFFT/RIFFT; <code>fftLenBy2</code> length of CFFT/CIFFT. | ||||
* <code>ifftFlagR</code> Flag for selection of RFFT or RIFFT(Set ifftFlagR to calculate RIFFT otherwise calculates RFFT); | ||||
* <code>bitReverseFlagR</code> Flag for selection of output order(Set bitReverseFlagR to output in normal order otherwise output in bit reversed order); | ||||
* <code>twidCoefRModifier</code> modifier for twiddle factor table which supports 128, 512, 2048 RFFT lengths with same table; | ||||
* <code>pTwiddleAReal</code>points to A array of twiddle coefficients; <code>pTwiddleBReal</code>points to B array of twiddle coefficients; | ||||
* <code>pCfft</code> points to the CFFT Instance structure. The CFFT structure also needs to be initialized, refer to arm_cfft_radix4_f32() for details regarding | ||||
* static initialization of cfft structure. | ||||
* | ||||
* \par Fixed-Point Behavior | ||||
* Care must be taken when using the fixed-point versions of the RFFT/RIFFT function. | ||||
* Refer to the function specific documentation below for usage guidelines. | ||||
*/ | ||||
/*-------------------------------------------------------------------- | ||||
* Internal functions prototypes | ||||
*--------------------------------------------------------------------*/ | ||||
void arm_split_rfft_f32( | ||||
float32_t * pSrc, | ||||
uint32_t fftLen, | ||||
float32_t * pATable, | ||||
float32_t * pBTable, | ||||
float32_t * pDst, | ||||
uint32_t modifier); | ||||
void arm_split_rifft_f32( | ||||
float32_t * pSrc, | ||||
uint32_t fftLen, | ||||
float32_t * pATable, | ||||
float32_t * pBTable, | ||||
float32_t * pDst, | ||||
uint32_t modifier); | ||||
/** | ||||
* @addtogroup RFFT_RIFFT | ||||
* @{ | ||||
*/ | ||||
/** | ||||
* @brief Processing function for the floating-point RFFT/RIFFT. | ||||
* @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. | ||||
*/ | ||||
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 RFFT_RIFFT 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_f32( | ||||
float32_t * pSrc, | ||||
uint32_t fftLen, | ||||
float32_t * pATable, | ||||
float32_t * pBTable, | ||||
float32_t * pDst, | ||||
uint32_t modifier) | ||||
{ | ||||
uint32_t i; /* Loop Counter */ | ||||
float32_t outR, outI; /* Temporary variables for output */ | ||||
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 */ | ||||
pSrc[2u * fftLen] = pSrc[0]; | ||||
pSrc[(2u * fftLen) + 1u] = pSrc[1]; | ||||
/* 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]); */ | ||||
/* 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 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_f32( | ||||
float32_t * pSrc, | ||||
uint32_t fftLen, | ||||
float32_t * pATable, | ||||
float32_t * pBTable, | ||||
float32_t * pDst, | ||||
uint32_t modifier) | ||||
{ | ||||
float32_t outR, outI; /* Temporary variables for output */ | ||||
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 * 2u); | ||||
pCoefA = pCoefA + ((modifier * 2u) - 1u); | ||||
/* Decrement loop count */ | ||||
fftLen--; | ||||
} | ||||
} | ||||