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229 lines
6.2 KiB
C
229 lines
6.2 KiB
C
/* ----------------------------------------------------------------------
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* Project: CMSIS DSP Library
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* Title: arm_rfft_fast_f64.c
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* Description: RFFT & RIFFT Double precision Floating point process function
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*
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* $Date: 23 April 2021
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* $Revision: V1.9.0
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*
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* Target Processor: Cortex-M and Cortex-A cores
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* -------------------------------------------------------------------- */
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/*
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* Copyright (C) 2010-2021 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 "dsp/transform_functions.h"
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void stage_rfft_f64(
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const arm_rfft_fast_instance_f64 * S,
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float64_t * p,
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float64_t * pOut)
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{
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uint32_t k; /* Loop Counter */
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float64_t twR, twI; /* RFFT Twiddle coefficients */
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const float64_t * pCoeff = S->pTwiddleRFFT; /* Points to RFFT Twiddle factors */
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float64_t *pA = p; /* increasing pointer */
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float64_t *pB = p; /* decreasing pointer */
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float64_t xAR, xAI, xBR, xBI; /* temporary variables */
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float64_t t1a, t1b; /* temporary variables */
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float64_t p0, p1, p2, p3; /* temporary variables */
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k = (S->Sint).fftLen - 1;
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/* Pack first and last sample of the frequency domain together */
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xBR = pB[0];
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xBI = pB[1];
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xAR = pA[0];
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xAI = pA[1];
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twR = *pCoeff++ ;
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twI = *pCoeff++ ;
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// U1 = XA(1) + XB(1); % It is real
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t1a = xBR + xAR ;
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// U2 = XB(1) - XA(1); % It is imaginary
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t1b = xBI + xAI ;
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// real(tw * (xB - xA)) = twR * (xBR - xAR) - twI * (xBI - xAI);
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// imag(tw * (xB - xA)) = twI * (xBR - xAR) + twR * (xBI - xAI);
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*pOut++ = 0.5 * ( t1a + t1b );
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*pOut++ = 0.5 * ( t1a - t1b );
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// XA(1) = 1/2*( U1 - imag(U2) + i*( U1 +imag(U2) ));
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pB = p + 2*k;
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pA += 2;
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do
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{
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/*
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function X = my_split_rfft(X, ifftFlag)
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% X is a series of real numbers
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L = length(X);
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XC = X(1:2:end) +i*X(2:2:end);
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XA = fft(XC);
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XB = conj(XA([1 end:-1:2]));
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TW = i*exp(-2*pi*i*[0:L/2-1]/L).';
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for l = 2:L/2
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XA(l) = 1/2 * (XA(l) + XB(l) + TW(l) * (XB(l) - XA(l)));
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end
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XA(1) = 1/2* (XA(1) + XB(1) + TW(1) * (XB(1) - XA(1))) + i*( 1/2*( XA(1) + XB(1) + i*( XA(1) - XB(1))));
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X = XA;
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*/
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xBI = pB[1];
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xBR = pB[0];
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xAR = pA[0];
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xAI = pA[1];
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twR = *pCoeff++;
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twI = *pCoeff++;
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t1a = xBR - xAR ;
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t1b = xBI + xAI ;
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// real(tw * (xB - xA)) = twR * (xBR - xAR) - twI * (xBI - xAI);
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// imag(tw * (xB - xA)) = twI * (xBR - xAR) + twR * (xBI - xAI);
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p0 = twR * t1a;
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p1 = twI * t1a;
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p2 = twR * t1b;
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p3 = twI * t1b;
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*pOut++ = 0.5 * (xAR + xBR + p0 + p3 ); //xAR
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*pOut++ = 0.5 * (xAI - xBI + p1 - p2 ); //xAI
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pA += 2;
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pB -= 2;
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k--;
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} while (k > 0U);
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}
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/* Prepares data for inverse cfft */
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void merge_rfft_f64(
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const arm_rfft_fast_instance_f64 * S,
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float64_t * p,
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float64_t * pOut)
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{
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uint32_t k; /* Loop Counter */
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float64_t twR, twI; /* RFFT Twiddle coefficients */
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const float64_t *pCoeff = S->pTwiddleRFFT; /* Points to RFFT Twiddle factors */
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float64_t *pA = p; /* increasing pointer */
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float64_t *pB = p; /* decreasing pointer */
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float64_t xAR, xAI, xBR, xBI; /* temporary variables */
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float64_t t1a, t1b, r, s, t, u; /* temporary variables */
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k = (S->Sint).fftLen - 1;
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xAR = pA[0];
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xAI = pA[1];
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pCoeff += 2 ;
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*pOut++ = 0.5 * ( xAR + xAI );
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*pOut++ = 0.5 * ( xAR - xAI );
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pB = p + 2*k ;
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pA += 2 ;
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while (k > 0U)
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{
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/* G is half of the frequency complex spectrum */
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//for k = 2:N
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// Xk(k) = 1/2 * (G(k) + conj(G(N-k+2)) + Tw(k)*( G(k) - conj(G(N-k+2))));
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xBI = pB[1] ;
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xBR = pB[0] ;
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xAR = pA[0];
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xAI = pA[1];
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twR = *pCoeff++;
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twI = *pCoeff++;
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t1a = xAR - xBR ;
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t1b = xAI + xBI ;
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r = twR * t1a;
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s = twI * t1b;
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t = twI * t1a;
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u = twR * t1b;
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// real(tw * (xA - xB)) = twR * (xAR - xBR) - twI * (xAI - xBI);
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// imag(tw * (xA - xB)) = twI * (xAR - xBR) + twR * (xAI - xBI);
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*pOut++ = 0.5 * (xAR + xBR - r - s ); //xAR
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*pOut++ = 0.5 * (xAI - xBI + t - u ); //xAI
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pA += 2;
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pB -= 2;
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k--;
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}
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}
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/**
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@ingroup groupTransforms
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*/
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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 Double Precision floating-point real FFT.
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@param[in] S points to an arm_rfft_fast_instance_f64 structure
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@param[in] p points to input buffer (Source buffer is modified by this function.)
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@param[in] pOut points to output buffer
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@param[in] ifftFlag
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- value = 0: RFFT
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- value = 1: RIFFT
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@return none
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*/
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void arm_rfft_fast_f64(
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arm_rfft_fast_instance_f64 * S,
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float64_t * p,
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float64_t * pOut,
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uint8_t ifftFlag)
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{
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arm_cfft_instance_f64 * Sint = &(S->Sint);
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Sint->fftLen = S->fftLenRFFT / 2;
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/* Calculation of Real FFT */
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if (ifftFlag)
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{
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/* Real FFT compression */
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merge_rfft_f64(S, p, pOut);
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/* Complex radix-4 IFFT process */
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arm_cfft_f64( Sint, pOut, ifftFlag, 1);
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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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arm_cfft_f64( Sint, p, ifftFlag, 1);
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/* Real FFT extraction */
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stage_rfft_f64(S, p, pOut);
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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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