1 /* ----------------------------------------------------------------------
2 * Project: CMSIS DSP Library
3 * Title: arm_mfcc_q31.c
4 * Description: MFCC function for the q31 version
5 *
6 * $Date: 07 September 2021
7 * $Revision: V1.10.0
8 *
9 * Target Processor: Cortex-M and Cortex-A cores
10 * -------------------------------------------------------------------- */
11 /*
12 * Copyright (C) 2010-2021 ARM Limited or its affiliates. All rights reserved.
13 *
14 * SPDX-License-Identifier: Apache-2.0
15 *
16 * Licensed under the Apache License, Version 2.0 (the License); you may
17 * not use this file except in compliance with the License.
18 * You may obtain a copy of the License at
19 *
20 * www.apache.org/licenses/LICENSE-2.0
21 *
22 * Unless required by applicable law or agreed to in writing, software
23 * distributed under the License is distributed on an AS IS BASIS, WITHOUT
24 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
25 * See the License for the specific language governing permissions and
26 * limitations under the License.
27 */
28
29
30
31 #include "dsp/transform_functions.h"
32 #include "dsp/statistics_functions.h"
33 #include "dsp/basic_math_functions.h"
34 #include "dsp/complex_math_functions.h"
35 #include "dsp/fast_math_functions.h"
36 #include "dsp/matrix_functions.h"
37
38 /* Constants for Q31 implementation */
39 #define LOG2TOLOG_Q31 0x02C5C860
40 #define MICRO_Q31 0x08637BD0
41 #define SHIFT_MELFILTER_SATURATION_Q31 10
42 /**
43 @ingroup MFCC
44 */
45
46
47
48 /**
49 @addtogroup MFCCQ31
50 @{
51 */
52
53 /**
54 @brief MFCC Q31
55 @param[in] S points to the mfcc instance structure
56 @param[in] pSrc points to the input samples in Q31
57 @param[out] pDst points to the output MFCC values in q8.23 format
58 @param[inout] pTmp points to a temporary buffer of complex
59
60 @par Description
61 The number of input samples is the FFT length used
62 when initializing the instance data structure.
63
64 The temporary buffer has a 2*fft length.
65
66 The source buffer is modified by this function.
67
68 The function may saturate. If the FFT length is too
69 big and the number of MEL filters too small then the fixed
70 point computations may saturate.
71
72 */
73
arm_mfcc_q31(const arm_mfcc_instance_q31 * S,q31_t * pSrc,q31_t * pDst,q31_t * pTmp)74 arm_status arm_mfcc_q31(
75 const arm_mfcc_instance_q31 * S,
76 q31_t *pSrc,
77 q31_t *pDst,
78 q31_t *pTmp
79 )
80 {
81 q31_t m;
82 uint32_t index;
83 uint32_t fftShift=0;
84 q31_t logExponent;
85 q63_t result;
86 arm_matrix_instance_q31 pDctMat;
87 uint32_t i;
88 uint32_t coefsPos;
89 uint32_t filterLimit;
90 q31_t *pTmp2=(q31_t*)pTmp;
91
92 arm_status status = ARM_MATH_SUCCESS;
93
94 // q31
95 arm_absmax_q31(pSrc,S->fftLen,&m,&index);
96
97 if ((m != 0) && (m != 0x7FFFFFFF))
98 {
99 q31_t quotient;
100 int16_t shift;
101
102 status = arm_divide_q31(0x7FFFFFFF,m,"ient,&shift);
103 if (status != ARM_MATH_SUCCESS)
104 {
105 return(status);
106 }
107
108 arm_scale_q31(pSrc,quotient,shift,pSrc,S->fftLen);
109 }
110
111
112 // q31
113 arm_mult_q31(pSrc,S->windowCoefs, pSrc, S->fftLen);
114
115
116 /* Compute spectrum magnitude
117 */
118 fftShift = 31 - __CLZ(S->fftLen);
119 #if defined(ARM_MFCC_CFFT_BASED)
120 /* some HW accelerator for CMSIS-DSP used in some boards
121 are only providing acceleration for CFFT.
122 With ARM_MFCC_CFFT_BASED enabled, CFFT is used and the MFCC
123 will be accelerated on those boards.
124
125 The default is to use RFFT
126 */
127 /* Convert from real to complex */
128 for(i=0; i < S->fftLen ; i++)
129 {
130 pTmp2[2*i] = pSrc[i];
131 pTmp2[2*i+1] = 0;
132 }
133 arm_cfft_q31(&(S->cfft),pTmp2,0,1);
134 #else
135 /* Default RFFT based implementation */
136 arm_rfft_q31(&(S->rfft),pSrc,pTmp2);
137 #endif
138 filterLimit = 1 + (S->fftLen >> 1);
139
140
141 // q31 - fftShift
142 arm_cmplx_mag_q31(pTmp2,pSrc,filterLimit);
143 // q30 - fftShift
144
145
146 /* Apply MEL filters */
147 coefsPos = 0;
148 for(i=0; i<S->nbMelFilters; i++)
149 {
150 arm_dot_prod_q31(pSrc+S->filterPos[i],
151 &(S->filterCoefs[coefsPos]),
152 S->filterLengths[i],
153 &result);
154
155
156 coefsPos += S->filterLengths[i];
157
158 // q16.48 - fftShift
159 result += MICRO_Q31;
160 result >>= (SHIFT_MELFILTER_SATURATION_Q31 + 18);
161 // q16.29 - fftShift - satShift
162 pTmp[i] = __SSAT(result,31) ;
163
164 }
165
166 if ((m != 0) && (m != 0x7FFFFFFF))
167 {
168 arm_scale_q31(pTmp,m,0,pTmp,S->nbMelFilters);
169 }
170
171 // q16.29 - fftShift - satShift
172 /* Compute the log */
173 arm_vlog_q31(pTmp,pTmp,S->nbMelFilters);
174
175
176 // q5.26
177
178 logExponent = fftShift + 2 + SHIFT_MELFILTER_SATURATION_Q31;
179 logExponent = logExponent * LOG2TOLOG_Q31;
180
181
182 // q5.26
183 arm_offset_q31(pTmp,logExponent,pTmp,S->nbMelFilters);
184 arm_shift_q31(pTmp,-3,pTmp,S->nbMelFilters);
185
186
187 // q8.23
188
189 pDctMat.numRows=S->nbDctOutputs;
190 pDctMat.numCols=S->nbMelFilters;
191 pDctMat.pData=(q31_t*)S->dctCoefs;
192
193 arm_mat_vec_mult_q31(&pDctMat, pTmp, pDst);
194
195 return(status);
196 }
197
198 /**
199 @} end of MFCCQ31 group
200 */
201
