1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
|
/* ----------------------------------------------------------------------
* Project: CMSIS DSP Library
* Title: arm_rfft_q31.c
* Description: FFT & RIFFT Q31 process function
*
* $Date: 18. March 2019
* $Revision: V1.6.0
*
* Target Processor: Cortex-M cores
* -------------------------------------------------------------------- */
/*
* Copyright (C) 2010-2019 ARM Limited or its affiliates. All rights reserved.
*
* SPDX-License-Identifier: Apache-2.0
*
* Licensed under the Apache License, Version 2.0 (the License); you may
* not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an AS IS BASIS, WITHOUT
* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
#include "arm_math.h"
/* ----------------------------------------------------------------------
* Internal functions prototypes
* -------------------------------------------------------------------- */
void arm_split_rfft_q31(
q31_t * pSrc,
uint32_t fftLen,
const q31_t * pATable,
const q31_t * pBTable,
q31_t * pDst,
uint32_t modifier);
void arm_split_rifft_q31(
q31_t * pSrc,
uint32_t fftLen,
const q31_t * pATable,
const 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 input buffer
@param[out] pDst points to output buffer
@return none
@par Input an output formats
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 L2 = S->fftLenReal >> 1U;
uint32_t i;
/* 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] << 1U;
}
}
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 input buffer
@param[in] fftLen length of FFT
@param[in] pATable points to twiddle Coef A buffer
@param[in] pBTable points to twiddle Coef B buffer
@param[out] pDst points to 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,
const q31_t * pATable,
const q31_t * pBTable,
q31_t * pDst,
uint32_t modifier)
{
uint32_t i; /* Loop Counter */
q31_t outR, outI; /* Temporary variables for output */
const 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[4 * fftLen - 1];
q31_t *pIn1 = &pSrc[2], *pIn2 = &pSrc[2 * fftLen - 1];
/* Init coefficient pointers */
pCoefA = &pATable[modifier * 2];
pCoefB = &pBTable[modifier * 2];
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 + (2 * modifier);
pCoefA = pCoefA + (2 * modifier - 1);
/* Decrement loop count */
i--;
}
pDst[2 * fftLen] = (pSrc[0] - pSrc[1]) >> 1U;
pDst[2 * fftLen + 1] = 0;
pDst[0] = (pSrc[0] + pSrc[1]) >> 1U;
pDst[1] = 0;
}
/**
@brief Core Real IFFT process
@param[in] pSrc points to input buffer
@param[in] fftLen length of FFT
@param[in] pATable points to twiddle Coef A buffer
@param[in] pBTable points to twiddle Coef B buffer
@param[out] pDst points to 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,
const q31_t * pATable,
const q31_t * pBTable,
q31_t * pDst,
uint32_t modifier)
{
q31_t outR, outI; /* Temporary variables for output */
const 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[2 * fftLen + 1];
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 * 2);
pCoefA = pCoefA + (modifier * 2 - 1);
/* Decrement loop count */
fftLen--;
}
}
|
