1/* Copyright 2017 The TensorFlow Authors. All Rights Reserved.
2
3Licensed under the Apache License, Version 2.0 (the "License");
4you may not use this file except in compliance with the License.
5You may obtain a copy of the License at
6
7 http://www.apache.org/licenses/LICENSE-2.0
8
9Unless required by applicable law or agreed to in writing, software
10distributed under the License is distributed on an "AS IS" BASIS,
11WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
12See the License for the specific language governing permissions and
13limitations under the License.
14==============================================================================*/
15
16#include <math.h>
17
18#include "tensorflow/core/kernels/mfcc.h"
19
20#include "tensorflow/core/platform/logging.h"
21
22namespace tensorflow {
23
24const double kDefaultUpperFrequencyLimit = 4000;
25const double kDefaultLowerFrequencyLimit = 20;
26const double kFilterbankFloor = 1e-12;
27const int kDefaultFilterbankChannelCount = 40;
28const int kDefaultDCTCoefficientCount = 13;
29
30Mfcc::Mfcc()
31 : initialized_(false),
32 lower_frequency_limit_(kDefaultLowerFrequencyLimit),
33 upper_frequency_limit_(kDefaultUpperFrequencyLimit),
34 filterbank_channel_count_(kDefaultFilterbankChannelCount),
35 dct_coefficient_count_(kDefaultDCTCoefficientCount) {}
36
37bool Mfcc::Initialize(int input_length, double input_sample_rate) {
38 bool initialized = mel_filterbank_.Initialize(
39 input_length, input_sample_rate, filterbank_channel_count_,
40 lower_frequency_limit_, upper_frequency_limit_);
41 initialized &=
42 dct_.Initialize(filterbank_channel_count_, dct_coefficient_count_);
43 initialized_ = initialized;
44 return initialized;
45}
46
47void Mfcc::Compute(const std::vector<double>& spectrogram_frame,
48 std::vector<double>* output) const {
49 if (!initialized_) {
50 LOG(ERROR) << "Mfcc not initialized.";
51 return;
52 }
53 std::vector<double> working;
54 mel_filterbank_.Compute(spectrogram_frame, &working);
55 for (int i = 0; i < working.size(); ++i) {
56 double val = working[i];
57 if (val < kFilterbankFloor) {
58 val = kFilterbankFloor;
59 }
60 working[i] = log(val);
61 }
62 dct_.Compute(working, output);
63}
64
65} // namespace tensorflow
66