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Drivers/CMSIS/DSP/Source/TransformFunctions/arm_mfcc_q15.c

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+/* ----------------------------------------------------------------------
+ * Project:      CMSIS DSP Library
+ * Title:        arm_mfcc_q15.c
+ * Description:  MFCC function for the q15 version
+ *
+ * $Date:        07 September 2021
+ * $Revision:    V1.10.0
+ *
+ * Target Processor: Cortex-M and Cortex-A cores
+ * -------------------------------------------------------------------- */
+/*
+ * Copyright (C) 2010-2021 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 "dsp/transform_functions.h"
+#include "dsp/statistics_functions.h"
+#include "dsp/basic_math_functions.h"
+#include "dsp/complex_math_functions.h"
+#include "dsp/fast_math_functions.h"
+#include "dsp/matrix_functions.h"
+
+/* Constants for Q15 implementation */
+#define LOG2TOLOG_Q15 0x02C5C860
+#define MICRO_Q15 0x00000219
+#define SHIFT_MELFILTER_SATURATION_Q15 10
+/**
+  @ingroup groupTransforms
+ */
+
+
+/**
+  @defgroup MFCC MFCC
+
+  MFCC Transform
+
+  There are separate functions for floating-point, Q15, and Q15 data types.
+ */
+
+
+
+/**
+  @addtogroup MFCC
+  @{
+ */
+
+/**
+  @brief         MFCC Q15
+  @param[in]    S       points to the mfcc instance structure
+  @param[in]     pSrc points to the input samples in Q15
+  @param[out]     pDst  points to the output MFCC values in q8.7 format
+  @param[inout]     pTmp  points to a temporary buffer of complex
+
+  @return        none
+
+  @par           Description
+                   The number of input samples is the FFT length used
+                   when initializing the instance data structure.
+
+                   The temporary buffer has a 2*fft length.
+
+                   The source buffer is modified by this function.
+
+                   The function may saturate. If the FFT length is too
+                   big and the number of MEL filters too small then the fixed
+                   point computations may saturate.
+
+ */
+
+arm_status arm_mfcc_q15(
+  const arm_mfcc_instance_q15 * S,
+  q15_t *pSrc,
+  q15_t *pDst,
+  q31_t *pTmp
+  )
+{
+    q15_t m;
+    uint32_t index;
+    uint32_t fftShift=0;
+    q31_t logExponent;
+    q63_t result;
+    arm_matrix_instance_q15 pDctMat;
+    uint32_t i;
+    uint32_t coefsPos;
+    uint32_t filterLimit;
+    q15_t *pTmp2=(q15_t*)pTmp;
+
+    arm_status status = ARM_MATH_SUCCESS;
+    
+    // q15
+    arm_absmax_q15(pSrc,S->fftLen,&m,&index);
+
+    if (m !=0)
+    {
+       q15_t quotient;
+       int16_t shift;
+
+       status = arm_divide_q15(0x7FFF,m,&quotient,&shift);
+       if (status != ARM_MATH_SUCCESS)
+       {
+          return(status);
+       }
+ 
+       arm_scale_q15(pSrc,quotient,shift,pSrc,S->fftLen);
+    }
+
+
+    // q15
+    arm_mult_q15(pSrc,S->windowCoefs, pSrc, S->fftLen);
+
+
+    /* Compute spectrum magnitude 
+    */
+    fftShift = 31 - __CLZ(S->fftLen);
+#if defined(ARM_MFCC_CFFT_BASED)
+    /* some HW accelerator for CMSIS-DSP used in some boards
+       are only providing acceleration for CFFT.
+       With ARM_MFCC_CFFT_BASED enabled, CFFT is used and the MFCC
+       will be accelerated on those boards.
+ 
+       The default is to use RFFT
+    */
+    /* Convert from real to complex */
+    for(i=0; i < S->fftLen ; i++)
+    {
+      pTmp2[2*i] = pSrc[i];
+      pTmp2[2*i+1] = 0;
+    }
+    arm_cfft_q15(&(S->cfft),pTmp2,0,1);
+#else
+    /* Default RFFT based implementation */
+    arm_rfft_q15(&(S->rfft),pSrc,pTmp2);
+#endif
+    filterLimit = 1 + (S->fftLen >> 1);
+
+
+    // q15 - fftShift
+    arm_cmplx_mag_q15(pTmp2,pSrc,filterLimit);
+    // q14 - fftShift
+
+    /* Apply MEL filters */
+    coefsPos = 0;
+    for(i=0; i<S->nbMelFilters; i++)
+    {
+      arm_dot_prod_q15(pSrc+S->filterPos[i],
+        &(S->filterCoefs[coefsPos]),
+        S->filterLengths[i],
+        &result);
+
+      coefsPos += S->filterLengths[i];
+
+      // q34.29 - fftShift
+      result += MICRO_Q15;
+      result >>= SHIFT_MELFILTER_SATURATION_Q15;
+      // q34.29 - fftShift - satShift
+      pTmp[i] = __SSAT(result,31) ;
+
+    }
+
+
+    // q34.29 - fftShift - satShift
+    /* Compute the log */
+    arm_vlog_q31(pTmp,pTmp,S->nbMelFilters);
+
+
+    // q5.26
+   
+    logExponent = fftShift + 2 + SHIFT_MELFILTER_SATURATION_Q15;
+    logExponent = logExponent * LOG2TOLOG_Q15;
+
+
+    // q8.26
+    arm_offset_q31(pTmp,logExponent,pTmp,S->nbMelFilters);
+    arm_shift_q31(pTmp,-19,pTmp,S->nbMelFilters);
+    for(i=0; i<S->nbMelFilters; i++)
+    { 
+      pSrc[i] = __SSAT((q15_t)pTmp[i],16);
+    }
+
+    // q8.7
+
+    pDctMat.numRows=S->nbDctOutputs;
+    pDctMat.numCols=S->nbMelFilters;
+    pDctMat.pData=(q15_t*)S->dctCoefs;
+
+    arm_mat_vec_mult_q15(&pDctMat, pSrc, pDst);
+
+    return(status);
+}
+
+/**
+  @} end of MFCC group
+ */