| /* |
| * Copyright (c) 2021 Arm Limited. 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 |
| * |
| * http://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. |
| */ |
| #ifndef KWS_ASR_WAV2LET_MFCC_HPP |
| #define KWS_ASR_WAV2LET_MFCC_HPP |
| |
| #include "Mfcc.hpp" |
| |
| namespace arm { |
| namespace app { |
| namespace audio { |
| |
| /* Class to provide Wav2Letter specific MFCC calculation requirements. */ |
| class Wav2LetterMFCC : public MFCC { |
| |
| public: |
| static constexpr uint32_t ms_defaultSamplingFreq = 16000; |
| static constexpr uint32_t ms_defaultNumFbankBins = 128; |
| static constexpr uint32_t ms_defaultMelLoFreq = 0; |
| static constexpr uint32_t ms_defaultMelHiFreq = 8000; |
| static constexpr bool ms_defaultUseHtkMethod = false; |
| |
| explicit Wav2LetterMFCC(const size_t numFeats, const size_t frameLen) |
| : MFCC(MfccParams( |
| ms_defaultSamplingFreq, ms_defaultNumFbankBins, |
| ms_defaultMelLoFreq, ms_defaultMelHiFreq, |
| numFeats, frameLen, ms_defaultUseHtkMethod)) |
| {} |
| |
| Wav2LetterMFCC() = delete; |
| ~Wav2LetterMFCC() = default; |
| |
| protected: |
| |
| /** |
| * @brief Overrides base class implementation of this function. |
| * @param[in] fftVec Vector populated with FFT magnitudes. |
| * @param[in] melFilterBank 2D Vector with filter bank weights. |
| * @param[in] filterBankFilterFirst Vector containing the first indices of filter bank |
| * to be used for each bin. |
| * @param[in] filterBankFilterLast Vector containing the last indices of filter bank |
| * to be used for each bin. |
| * @param[out] melEnergies Pre-allocated vector of MEL energies to be |
| * populated. |
| * @return true if successful, false otherwise. |
| */ |
| bool ApplyMelFilterBank( |
| std::vector<float>& fftVec, |
| std::vector<std::vector<float>>& melFilterBank, |
| std::vector<uint32_t>& filterBankFilterFirst, |
| std::vector<uint32_t>& filterBankFilterLast, |
| std::vector<float>& melEnergies) override; |
| |
| /** |
| * @brief Override for the base class implementation convert mel |
| * energies to logarithmic scale. The difference from |
| * default behaviour is that the power is converted to dB |
| * and subsequently clamped. |
| * @param[in,out] melEnergies 1D vector of Mel energies. |
| **/ |
| void ConvertToLogarithmicScale( |
| std::vector<float>& melEnergies) override; |
| |
| /** |
| * @brief Create a matrix used to calculate Discrete Cosine |
| * Transform. Override for the base class' default |
| * implementation as the first and last elements |
| * use a different normaliser. |
| * @param[in] inputLength Input length of the buffer on which |
| * DCT will be performed. |
| * @param[in] coefficientCount Total coefficients per input length. |
| * @return 1D vector with inputLength x coefficientCount elements |
| * populated with DCT coefficients. |
| */ |
| std::vector<float> CreateDCTMatrix( |
| int32_t inputLength, |
| int32_t coefficientCount) override; |
| |
| /** |
| * @brief Given the low and high Mel values, get the normaliser |
| * for weights to be applied when populating the filter |
| * bank. Override for the base class implementation. |
| * @param[in] leftMel Low Mel frequency value. |
| * @param[in] rightMel High Mel frequency value. |
| * @param[in] useHTKMethod Bool to signal if HTK method is to be |
| * used for calculation. |
| * @return Value to use for normalising. |
| */ |
| float GetMelFilterBankNormaliser( |
| const float& leftMel, |
| const float& rightMel, |
| bool useHTKMethod) override; |
| |
| }; |
| |
| } /* namespace audio */ |
| } /* namespace app */ |
| } /* namespace arm */ |
| |
| #endif /* KWS_ASR_WAV2LET_MFCC_HPP */ |