Laxmi Kant Tiwari
CMSIS DSP Lib
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Diff: cmsis_dsp/TransformFunctions/arm_cfft_f32.c
- Revision:
- 3:7a284390b0ce
--- /dev/null Thu Jan 01 00:00:00 1970 +0000
+++ b/cmsis_dsp/TransformFunctions/arm_cfft_f32.c Fri Nov 08 13:45:10 2013 +0000
@@ -0,0 +1,616 @@
+/* ----------------------------------------------------------------------
+* Copyright (C) 2010-2013 ARM Limited. All rights reserved.
+*
+* $Date: 17. January 2013
+* $Revision: V1.4.1
+*
+* Project: CMSIS DSP Library
+* Title: arm_cfft_f32.c
+*
+* Description: Combined Radix Decimation in Frequency CFFT Floating point processing 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"
+#include "arm_common_tables.h"
+
+extern void arm_radix8_butterfly_f32(
+ float32_t * pSrc,
+ uint16_t fftLen,
+ const float32_t * pCoef,
+ uint16_t twidCoefModifier);
+
+extern void arm_bitreversal_32(
+ uint32_t * pSrc,
+ const uint16_t bitRevLen,
+ const uint16_t * pBitRevTable);
+
+/**
+* @ingroup groupTransforms
+*/
+
+/**
+* @defgroup ComplexFFT Complex FFT Functions
+*
+* \par
+* The Fast Fourier Transform (FFT) is an efficient algorithm for computing the
+* Discrete Fourier Transform (DFT). The FFT can be orders of magnitude faster
+* than the DFT, especially for long lengths.
+* The algorithms described in this section
+* operate on complex data. A separate set of functions is devoted to handling
+* of real sequences.
+* \par
+* There are separate algorithms for handling floating-point, Q15, and Q31 data
+* types. The algorithms available for each data type are described next.
+* \par
+* The FFT functions operate in-place. That is, the array holding the input data
+* will also be used to hold the corresponding result. The input data is complex
+* and contains <code>2*fftLen</code> interleaved values as shown below.
+* <pre> {real[0], imag[0], real[1], imag[1],..} </pre>
+* The FFT result will be contained in the same array and the frequency domain
+* values will have the same interleaving.
+*
+* \par Floating-point
+* The floating-point complex FFT uses a mixed-radix algorithm. Multiple radix-8
+* stages are performed along with a single radix-2 or radix-4 stage, as needed.
+* The algorithm supports lengths of [16, 32, 64, ..., 4096] and each length uses
+* a different twiddle factor table.
+* \par
+* The function uses the standard FFT definition and output values may grow by a
+* factor of <code>fftLen</code> when computing the forward transform. The
+* inverse transform includes a scale of <code>1/fftLen</code> as part of the
+* calculation and this matches the textbook definition of the inverse FFT.
+* \par
+* Preinitialized data structures containing twiddle factors and bit reversal
+* tables are provided and defined in <code>arm_const_structs.h</code>. Include
+* this header in your function and then pass one of the constant structures as
+* an argument to arm_cfft_f32. For example:
+* \par
+* <code>arm_cfft_f32(arm_cfft_sR_f32_len64, pSrc, 1, 1)</code>
+* \par
+* computes a 64-point inverse complex FFT including bit reversal.
+* The data structures are treated as constant data and not modified during the
+* calculation. The same data structure can be reused for multiple transforms
+* including mixing forward and inverse transforms.
+* \par
+* Earlier releases of the library provided separate radix-2 and radix-4
+* algorithms that operated on floating-point data. These functions are still
+* provided but are deprecated. The older functions are slower and less general
+* than the new functions.
+* \par
+* An example of initialization of the constants for the arm_cfft_f32 function follows:
+* \par
+* const static arm_cfft_instance_f32 *S;
+* ...
+* switch (length) {
+* case 16:
+* S = & arm_cfft_sR_f32_len16;
+* break;
+* case 32:
+* S = & arm_cfft_sR_f32_len32;
+* break;
+* case 64:
+* S = & arm_cfft_sR_f32_len64;
+* break;
+* case 128:
+* S = & arm_cfft_sR_f32_len128;
+* break;
+* case 256:
+* S = & arm_cfft_sR_f32_len256;
+* break;
+* case 512:
+* S = & arm_cfft_sR_f32_len512;
+* break;
+* case 1024:
+* S = & arm_cfft_sR_f32_len1024;
+* break;
+* case 2048:
+* S = & arm_cfft_sR_f32_len2048;
+* break;
+* case 4096:
+* S = & arm_cfft_sR_f32_len4096;
+* break;
+* }
+* \par Q15 and Q31
+* The library provides radix-2 and radix-4 FFT algorithms for fixed-point data. The
+* radix-2 algorithm supports lengths of [16, 32, 64, ..., 4096]. The radix-4
+* algorithm supports lengths of [16, 64, 256, ..., 4096]. When possible, you
+* should use the radix-4 algorithm since it is faster than the radix-2 of the
+* same length.
+* \par
+* The forward FFTs include scaling in order to prevent results from overflowing.
+* Intermediate results are scaled down during each butterfly stage. In the
+* radix-2 algorithm, a scale of 0.5 is applied during each butterfly. In the
+* radix-4 algorithm, a scale of 0.25 is applied. The scaling applies to both
+* the forward and the inverse FFTs. Thus the forward FFT contains an additional
+* scale factor of <code>1/fftLen</code> as compared to the standard textbook
+* definition of the FFT. The inverse FFT also scales down during each butterfly
+* stage and this corresponds to the standard textbook definition.
+* \par
+* A separate instance structure must be defined for each transform used but
+* twiddle factor and bit reversal tables can be reused.
+* \par
+* 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 table and bit reversal table pointers.
+* \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 should be manually
+* initialized as follows:
+* <pre>
+*arm_cfft_radix2_instance_q31 S = {fftLen, ifftFlag, bitReverseFlag, pTwiddle, pBitRevTable, twidCoefModifier, bitRevFactor};
+*arm_cfft_radix2_instance_q15 S = {fftLen, ifftFlag, bitReverseFlag, pTwiddle, pBitRevTable, twidCoefModifier, bitRevFactor};
+*arm_cfft_radix4_instance_q31 S = {fftLen, ifftFlag, bitReverseFlag, pTwiddle, pBitRevTable, twidCoefModifier, bitRevFactor};
+*arm_cfft_radix4_instance_q15 S = {fftLen, ifftFlag, bitReverseFlag, pTwiddle, pBitRevTable, twidCoefModifier, bitRevFactor};
+*arm_cfft_instance_f32 S = {fftLen, pTwiddle, pBitRevTable, bitRevLength};
+* </pre>
+* \par
+* where <code>fftLen</code> length of CFFT/CIFFT; <code>ifftFlag</code> Flag for
+* selection of forward or inverse transform. When ifftFlag is set the inverse
+* transform is calculated.
+* <code>bitReverseFlag</code> Flag for selection of output order (Set bitReverseFlag to output in normal order otherwise output in bit reversed order);
+* <code>pTwiddle</code>points to array of twiddle coefficients; <code>pBitRevTable</code> points to the bit reversal table.
+* <code>twidCoefModifier</code> modifier for twiddle factor table which supports all FFT lengths with same table;
+* <code>pBitRevTable</code> modifier for bit reversal table which supports all FFT lengths with same table.
+* <code>onebyfftLen</code> value of 1/fftLen to calculate CIFFT;
+* \par
+* The Q15 and Q31 FFT functions use a large bit reversal and twiddle factor
+* table. The tables are defined for the maximum length transform and a subset
+* of the coefficients are used in shorter transforms.
+*
+*/
+
+void arm_cfft_radix8by2_f32( arm_cfft_instance_f32 * S, float32_t * p1)
+{
+ uint32_t L = S->fftLen;
+ float32_t * pCol1, * pCol2, * pMid1, * pMid2;
+ float32_t * p2 = p1 + L;
+ const float32_t * tw = (float32_t *) S->pTwiddle;
+ float32_t t1[4], t2[4], t3[4], t4[4], twR, twI;
+ float32_t m0, m1, m2, m3;
+ uint32_t l;
+
+ pCol1 = p1;
+ pCol2 = p2;
+
+ // Define new length
+ L >>= 1;
+ // Initialize mid pointers
+ pMid1 = p1 + L;
+ pMid2 = p2 + L;
+
+ // do two dot Fourier transform
+ for ( l = L >> 2; l > 0; l-- )
+ {
+ t1[0] = p1[0];
+ t1[1] = p1[1];
+ t1[2] = p1[2];
+ t1[3] = p1[3];
+
+ t2[0] = p2[0];
+ t2[1] = p2[1];
+ t2[2] = p2[2];
+ t2[3] = p2[3];
+
+ t3[0] = pMid1[0];
+ t3[1] = pMid1[1];
+ t3[2] = pMid1[2];
+ t3[3] = pMid1[3];
+
+ t4[0] = pMid2[0];
+ t4[1] = pMid2[1];
+ t4[2] = pMid2[2];
+ t4[3] = pMid2[3];
+
+ *p1++ = t1[0] + t2[0];
+ *p1++ = t1[1] + t2[1];
+ *p1++ = t1[2] + t2[2];
+ *p1++ = t1[3] + t2[3]; // col 1
+
+ t2[0] = t1[0] - t2[0];
+ t2[1] = t1[1] - t2[1];
+ t2[2] = t1[2] - t2[2];
+ t2[3] = t1[3] - t2[3]; // for col 2
+
+ *pMid1++ = t3[0] + t4[0];
+ *pMid1++ = t3[1] + t4[1];
+ *pMid1++ = t3[2] + t4[2];
+ *pMid1++ = t3[3] + t4[3]; // col 1
+
+ t4[0] = t4[0] - t3[0];
+ t4[1] = t4[1] - t3[1];
+ t4[2] = t4[2] - t3[2];
+ t4[3] = t4[3] - t3[3]; // for col 2
+
+ twR = *tw++;
+ twI = *tw++;
+
+ // multiply by twiddle factors
+ m0 = t2[0] * twR;
+ m1 = t2[1] * twI;
+ m2 = t2[1] * twR;
+ m3 = t2[0] * twI;
+
+ // R = R * Tr - I * Ti
+ *p2++ = m0 + m1;
+ // I = I * Tr + R * Ti
+ *p2++ = m2 - m3;
+
+ // use vertical symmetry
+ // 0.9988 - 0.0491i <==> -0.0491 - 0.9988i
+ m0 = t4[0] * twI;
+ m1 = t4[1] * twR;
+ m2 = t4[1] * twI;
+ m3 = t4[0] * twR;
+
+ *pMid2++ = m0 - m1;
+ *pMid2++ = m2 + m3;
+
+ twR = *tw++;
+ twI = *tw++;
+
+ m0 = t2[2] * twR;
+ m1 = t2[3] * twI;
+ m2 = t2[3] * twR;
+ m3 = t2[2] * twI;
+
+ *p2++ = m0 + m1;
+ *p2++ = m2 - m3;
+
+ m0 = t4[2] * twI;
+ m1 = t4[3] * twR;
+ m2 = t4[3] * twI;
+ m3 = t4[2] * twR;
+
+ *pMid2++ = m0 - m1;
+ *pMid2++ = m2 + m3;
+ }
+
+ // first col
+ arm_radix8_butterfly_f32( pCol1, L, (float32_t *) S->pTwiddle, 2u);
+ // second col
+ arm_radix8_butterfly_f32( pCol2, L, (float32_t *) S->pTwiddle, 2u);
+
+}
+
+void arm_cfft_radix8by4_f32( arm_cfft_instance_f32 * S, float32_t * p1)
+{
+ uint32_t L = S->fftLen >> 1;
+ float32_t * pCol1, *pCol2, *pCol3, *pCol4, *pEnd1, *pEnd2, *pEnd3, *pEnd4;
+ const float32_t *tw2, *tw3, *tw4;
+ float32_t * p2 = p1 + L;
+ float32_t * p3 = p2 + L;
+ float32_t * p4 = p3 + L;
+ float32_t t2[4], t3[4], t4[4], twR, twI;
+ float32_t p1ap3_0, p1sp3_0, p1ap3_1, p1sp3_1;
+ float32_t m0, m1, m2, m3;
+ uint32_t l, twMod2, twMod3, twMod4;
+
+ pCol1 = p1; // points to real values by default
+ pCol2 = p2;
+ pCol3 = p3;
+ pCol4 = p4;
+ pEnd1 = p2 - 1; // points to imaginary values by default
+ pEnd2 = p3 - 1;
+ pEnd3 = p4 - 1;
+ pEnd4 = pEnd3 + L;
+
+ tw2 = tw3 = tw4 = (float32_t *) S->pTwiddle;
+
+ L >>= 1;
+
+ // do four dot Fourier transform
+
+ twMod2 = 2;
+ twMod3 = 4;
+ twMod4 = 6;
+
+ // TOP
+ p1ap3_0 = p1[0] + p3[0];
+ p1sp3_0 = p1[0] - p3[0];
+ p1ap3_1 = p1[1] + p3[1];
+ p1sp3_1 = p1[1] - p3[1];
+
+ // col 2
+ t2[0] = p1sp3_0 + p2[1] - p4[1];
+ t2[1] = p1sp3_1 - p2[0] + p4[0];
+ // col 3
+ t3[0] = p1ap3_0 - p2[0] - p4[0];
+ t3[1] = p1ap3_1 - p2[1] - p4[1];
+ // col 4
+ t4[0] = p1sp3_0 - p2[1] + p4[1];
+ t4[1] = p1sp3_1 + p2[0] - p4[0];
+ // col 1
+ *p1++ = p1ap3_0 + p2[0] + p4[0];
+ *p1++ = p1ap3_1 + p2[1] + p4[1];
+
+ // Twiddle factors are ones
+ *p2++ = t2[0];
+ *p2++ = t2[1];
+ *p3++ = t3[0];
+ *p3++ = t3[1];
+ *p4++ = t4[0];
+ *p4++ = t4[1];
+
+ tw2 += twMod2;
+ tw3 += twMod3;
+ tw4 += twMod4;
+
+ for (l = (L - 2) >> 1; l > 0; l-- )
+ {
+
+ // TOP
+ p1ap3_0 = p1[0] + p3[0];
+ p1sp3_0 = p1[0] - p3[0];
+ p1ap3_1 = p1[1] + p3[1];
+ p1sp3_1 = p1[1] - p3[1];
+ // col 2
+ t2[0] = p1sp3_0 + p2[1] - p4[1];
+ t2[1] = p1sp3_1 - p2[0] + p4[0];
+ // col 3
+ t3[0] = p1ap3_0 - p2[0] - p4[0];
+ t3[1] = p1ap3_1 - p2[1] - p4[1];
+ // col 4
+ t4[0] = p1sp3_0 - p2[1] + p4[1];
+ t4[1] = p1sp3_1 + p2[0] - p4[0];
+ // col 1 - top
+ *p1++ = p1ap3_0 + p2[0] + p4[0];
+ *p1++ = p1ap3_1 + p2[1] + p4[1];
+
+ // BOTTOM
+ p1ap3_1 = pEnd1[-1] + pEnd3[-1];
+ p1sp3_1 = pEnd1[-1] - pEnd3[-1];
+ p1ap3_0 = pEnd1[0] + pEnd3[0];
+ p1sp3_0 = pEnd1[0] - pEnd3[0];
+ // col 2
+ t2[2] = pEnd2[0] - pEnd4[0] + p1sp3_1;
+ t2[3] = pEnd1[0] - pEnd3[0] - pEnd2[-1] + pEnd4[-1];
+ // col 3
+ t3[2] = p1ap3_1 - pEnd2[-1] - pEnd4[-1];
+ t3[3] = p1ap3_0 - pEnd2[0] - pEnd4[0];
+ // col 4
+ t4[2] = pEnd2[0] - pEnd4[0] - p1sp3_1;
+ t4[3] = pEnd4[-1] - pEnd2[-1] - p1sp3_0;
+ // col 1 - Bottom
+ *pEnd1-- = p1ap3_0 + pEnd2[0] + pEnd4[0];
+ *pEnd1-- = p1ap3_1 + pEnd2[-1] + pEnd4[-1];
+
+ // COL 2
+ // read twiddle factors
+ twR = *tw2++;
+ twI = *tw2++;
+ // multiply by twiddle factors
+ // let Z1 = a + i(b), Z2 = c + i(d)
+ // => Z1 * Z2 = (a*c - b*d) + i(b*c + a*d)
+ // Top
+ m0 = t2[0] * twR;
+ m1 = t2[1] * twI;
+ m2 = t2[1] * twR;
+ m3 = t2[0] * twI;
+
+ *p2++ = m0 + m1;
+ *p2++ = m2 - m3;
+ // use vertical symmetry col 2
+ // 0.9997 - 0.0245i <==> 0.0245 - 0.9997i
+ // Bottom
+ m0 = t2[3] * twI;
+ m1 = t2[2] * twR;
+ m2 = t2[2] * twI;
+ m3 = t2[3] * twR;
+
+ *pEnd2-- = m0 - m1;
+ *pEnd2-- = m2 + m3;
+
+ // COL 3
+ twR = tw3[0];
+ twI = tw3[1];
+ tw3 += twMod3;
+ // Top
+ m0 = t3[0] * twR;
+ m1 = t3[1] * twI;
+ m2 = t3[1] * twR;
+ m3 = t3[0] * twI;
+
+ *p3++ = m0 + m1;
+ *p3++ = m2 - m3;
+ // use vertical symmetry col 3
+ // 0.9988 - 0.0491i <==> -0.9988 - 0.0491i
+ // Bottom
+ m0 = -t3[3] * twR;
+ m1 = t3[2] * twI;
+ m2 = t3[2] * twR;
+ m3 = t3[3] * twI;
+
+ *pEnd3-- = m0 - m1;
+ *pEnd3-- = m3 - m2;
+
+ // COL 4
+ twR = tw4[0];
+ twI = tw4[1];
+ tw4 += twMod4;
+ // Top
+ m0 = t4[0] * twR;
+ m1 = t4[1] * twI;
+ m2 = t4[1] * twR;
+ m3 = t4[0] * twI;
+
+ *p4++ = m0 + m1;
+ *p4++ = m2 - m3;
+ // use vertical symmetry col 4
+ // 0.9973 - 0.0736i <==> -0.0736 + 0.9973i
+ // Bottom
+ m0 = t4[3] * twI;
+ m1 = t4[2] * twR;
+ m2 = t4[2] * twI;
+ m3 = t4[3] * twR;
+
+ *pEnd4-- = m0 - m1;
+ *pEnd4-- = m2 + m3;
+ }
+
+ //MIDDLE
+ // Twiddle factors are
+ // 1.0000 0.7071-0.7071i -1.0000i -0.7071-0.7071i
+ p1ap3_0 = p1[0] + p3[0];
+ p1sp3_0 = p1[0] - p3[0];
+ p1ap3_1 = p1[1] + p3[1];
+ p1sp3_1 = p1[1] - p3[1];
+
+ // col 2
+ t2[0] = p1sp3_0 + p2[1] - p4[1];
+ t2[1] = p1sp3_1 - p2[0] + p4[0];
+ // col 3
+ t3[0] = p1ap3_0 - p2[0] - p4[0];
+ t3[1] = p1ap3_1 - p2[1] - p4[1];
+ // col 4
+ t4[0] = p1sp3_0 - p2[1] + p4[1];
+ t4[1] = p1sp3_1 + p2[0] - p4[0];
+ // col 1 - Top
+ *p1++ = p1ap3_0 + p2[0] + p4[0];
+ *p1++ = p1ap3_1 + p2[1] + p4[1];
+
+ // COL 2
+ twR = tw2[0];
+ twI = tw2[1];
+
+ m0 = t2[0] * twR;
+ m1 = t2[1] * twI;
+ m2 = t2[1] * twR;
+ m3 = t2[0] * twI;
+
+ *p2++ = m0 + m1;
+ *p2++ = m2 - m3;
+ // COL 3
+ twR = tw3[0];
+ twI = tw3[1];
+
+ m0 = t3[0] * twR;
+ m1 = t3[1] * twI;
+ m2 = t3[1] * twR;
+ m3 = t3[0] * twI;
+
+ *p3++ = m0 + m1;
+ *p3++ = m2 - m3;
+ // COL 4
+ twR = tw4[0];
+ twI = tw4[1];
+
+ m0 = t4[0] * twR;
+ m1 = t4[1] * twI;
+ m2 = t4[1] * twR;
+ m3 = t4[0] * twI;
+
+ *p4++ = m0 + m1;
+ *p4++ = m2 - m3;
+
+ // first col
+ arm_radix8_butterfly_f32( pCol1, L, (float32_t *) S->pTwiddle, 4u);
+ // second col
+ arm_radix8_butterfly_f32( pCol2, L, (float32_t *) S->pTwiddle, 4u);
+ // third col
+ arm_radix8_butterfly_f32( pCol3, L, (float32_t *) S->pTwiddle, 4u);
+ // fourth col
+ arm_radix8_butterfly_f32( pCol4, L, (float32_t *) S->pTwiddle, 4u);
+
+}
+
+/**
+* @addtogroup ComplexFFT
+* @{
+*/
+
+/**
+* @details
+* @brief Processing function for the floating-point complex FFT.
+* @param[in] *S points to an instance of the floating-point CFFT structure.
+* @param[in, out] *p1 points to the complex data buffer of size <code>2*fftLen</code>. Processing occurs in-place.
+* @param[in] ifftFlag flag that selects forward (ifftFlag=0) or inverse (ifftFlag=1) transform.
+* @param[in] bitReverseFlag flag that enables (bitReverseFlag=1) or disables (bitReverseFlag=0) bit reversal of output.
+* @return none.
+*/
+
+void arm_cfft_f32(
+ const arm_cfft_instance_f32 * S,
+ float32_t * p1,
+ uint8_t ifftFlag,
+ uint8_t bitReverseFlag)
+{
+
+ uint32_t L = S->fftLen, l;
+ float32_t invL, * pSrc;
+
+ if(ifftFlag == 1u)
+ {
+ /* Conjugate input data */
+ pSrc = p1 + 1;
+ for(l=0; l<L; l++) {
+ *pSrc = -*pSrc;
+ pSrc += 2;
+ }
+ }
+
+ switch (L) {
+ case 16:
+ case 128:
+ case 1024:
+ arm_cfft_radix8by2_f32 ( (arm_cfft_instance_f32 *) S, p1);
+ break;
+ case 32:
+ case 256:
+ case 2048:
+ arm_cfft_radix8by4_f32 ( (arm_cfft_instance_f32 *) S, p1);
+ break;
+ case 64:
+ case 512:
+ case 4096:
+ arm_radix8_butterfly_f32( p1, L, (float32_t *) S->pTwiddle, 1);
+ break;
+ }
+
+ if( bitReverseFlag )
+ arm_bitreversal_32((uint32_t*)p1,S->bitRevLength,S->pBitRevTable);
+
+ if(ifftFlag == 1u)
+ {
+ invL = 1.0f/(float32_t)L;
+ /* Conjugate and scale output data */
+ pSrc = p1;
+ for(l=0; l<L; l++) {
+ *pSrc++ *= invL ;
+ *pSrc = -(*pSrc) * invL;
+ pSrc++;
+ }
+ }
+}
+