mfcc.h

00001 /*
00002  * Copyright (C) 2018 Arm Limited or its affiliates. All rights reserved.
00003  *
00004  * SPDX-License-Identifier: Apache-2.0
00005  *
00006  * Licensed under the Apache License, Version 2.0 (the License); you may
00007  * not use this file except in compliance with the License.
00008  * You may obtain a copy of the License at
00009  *
00010  * www.apache.org/licenses/LICENSE-2.0
00011  *
00012  * Unless required by applicable law or agreed to in writing, software
00013  * distributed under the License is distributed on an AS IS BASIS, WITHOUT
00014  * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
00015  * See the License for the specific language governing permissions and
00016  * limitations under the License.
00017  */
00018 
00019 #ifndef __KWS_MFCC_H__
00020 #define __KWS_MFCC_H__
00021 
00022 #include "arm_math.h"
00023 #include "string.h"
00024 
00025 #define SAMP_FREQ 16000
00026 #define NUM_FBANK_BINS 40
00027 #define MEL_LOW_FREQ 20
00028 #define MEL_HIGH_FREQ 4000
00029 
00030 #define M_2PI 6.283185307179586476925286766559005
00031 #define M_PI M_2PI/2
00032 
00033 class MFCC{
00034   private:
00035     int num_mfcc_features;
00036     int frame_len;
00037     int frame_len_padded;
00038     int mfcc_dec_bits;
00039     float * frame;
00040     float * buffer;
00041     float * mel_energies;
00042     float * window_func;
00043     int32_t * fbank_filter_first;
00044     int32_t * fbank_filter_last;
00045     float ** mel_fbank;
00046     float * dct_matrix;
00047     arm_rfft_fast_instance_f32 * rfft;
00048     float * create_dct_matrix(int32_t input_length, int32_t coefficient_count); 
00049     float ** create_mel_fbank();
00050  
00051     static inline float InverseMelScale(float mel_freq) {
00052       return 700.0f * (expf (mel_freq / 1127.0f) - 1.0f);
00053     }
00054 
00055     static inline float MelScale(float freq) {
00056       return 1127.0f * logf (1.0f + freq / 700.0f);
00057     }
00058 
00059   public:
00060     MFCC(int num_mfcc_features, int frame_len, int mfcc_dec_bits);
00061     ~MFCC();
00062     void mfcc_compute(const int16_t* data, q7_t* mfcc_out);
00063 };
00064 
00065 #endif