1 | /* Copyright 2017 The TensorFlow Authors. All Rights Reserved. |
2 | |
3 | Licensed under the Apache License, Version 2.0 (the "License"); |
4 | you may not use this file except in compliance with the License. |
5 | You may obtain a copy of the License at |
6 | |
7 | http://www.apache.org/licenses/LICENSE-2.0 |
8 | |
9 | Unless required by applicable law or agreed to in writing, software |
10 | distributed under the License is distributed on an "AS IS" BASIS, |
11 | WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
12 | See the License for the specific language governing permissions and |
13 | limitations 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 | |
22 | namespace tensorflow { |
23 | |
24 | const double kDefaultUpperFrequencyLimit = 4000; |
25 | const double kDefaultLowerFrequencyLimit = 20; |
26 | const double kFilterbankFloor = 1e-12; |
27 | const int kDefaultFilterbankChannelCount = 40; |
28 | const int kDefaultDCTCoefficientCount = 13; |
29 | |
30 | Mfcc::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 | |
37 | bool 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 | |
47 | void 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 | |