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Diffstat (limited to 'samples/SpeechRecognition/include/MFCC.hpp')
| -rw-r--r-- | samples/SpeechRecognition/include/MFCC.hpp | 244 |
1 files changed, 0 insertions, 244 deletions
diff --git a/samples/SpeechRecognition/include/MFCC.hpp b/samples/SpeechRecognition/include/MFCC.hpp deleted file mode 100644 index 14b6d9fe79..0000000000 --- a/samples/SpeechRecognition/include/MFCC.hpp +++ /dev/null @@ -1,244 +0,0 @@ -// -// Copyright © 2020 Arm Ltd and Contributors. All rights reserved. -// SPDX-License-Identifier: MIT -// - -#pragma once - -#include <vector> -#include <cstdint> -#include <cmath> -#include <limits> -#include <string> - -/* MFCC's consolidated parameters */ -class MfccParams -{ -public: - float m_samplingFreq; - int m_numFbankBins; - float m_melLoFreq; - float m_melHiFreq; - int m_numMfccFeatures; - int m_frameLen; - int m_frameLenPadded; - bool m_useHtkMethod; - int m_numMfccVectors; - - /** @brief Constructor */ - MfccParams(const float samplingFreq, const int numFbankBins, - const float melLoFreq, const float melHiFreq, - const int numMfccFeats, const int frameLen, - const bool useHtkMethod, const int numMfccVectors); - - /* Delete the default constructor */ - MfccParams() = delete; - - /* Default destructor */ - ~MfccParams() = default; - - /** @brief String representation of parameters */ - std::string Str(); -}; - -/** - * @brief Class for MFCC feature extraction. - * Based on https://github.com/ARM-software/ML-KWS-for-MCU/blob/master/Deployment/Source/MFCC/mfcc.cpp - * This class is designed to be generic and self-sufficient but - * certain calculation routines can be overridden to accommodate - * use-case specific requirements. - */ -class MFCC -{ - -public: - - /** - * @brief Extract MFCC features for one single small frame of - * audio data e.g. 640 samples. - * @param[in] audioData - Vector of audio samples to calculate - * features for. - * @return Vector of extracted MFCC features. - **/ - std::vector<float> MfccCompute(const std::vector<float>& audioData); - - MfccParams _m_params; - - /** - * @brief Constructor - * @param[in] params - MFCC parameters - */ - MFCC(const MfccParams& params); - - /* Delete the default constructor */ - MFCC() = delete; - - /** @brief Default destructor */ - ~MFCC() = default; - - /** @brief Initialise */ - void Init(); - - /** - * @brief Extract MFCC features and quantise for one single small - * frame of audio data e.g. 640 samples. - * @param[in] audioData - Vector of audio samples to calculate - * features for. - * @param[in] quantScale - quantisation scale. - * @param[in] quantOffset - quantisation offset - * @return Vector of extracted quantised MFCC features. - **/ - template<typename T> - std::vector<T> MfccComputeQuant(const std::vector<float>& audioData, - const float quantScale, - const int quantOffset) - { - this->_MfccComputePreFeature(audioData); - float minVal = std::numeric_limits<T>::min(); - float maxVal = std::numeric_limits<T>::max(); - - std::vector<T> mfccOut(this->_m_params.m_numMfccFeatures); - const size_t numFbankBins = this->_m_params.m_numFbankBins; - - /* Take DCT. Uses matrix mul. */ - for (size_t i = 0, j = 0; i < mfccOut.size(); ++i, j += numFbankBins) - { - float sum = 0; - for (size_t k = 0; k < numFbankBins; ++k) - { - sum += this->_m_dctMatrix[j + k] * this->_m_melEnergies[k]; - } - /* Quantize to T. */ - sum = std::round((sum / quantScale) + quantOffset); - mfccOut[i] = static_cast<T>(std::min<float>(std::max<float>(sum, minVal), maxVal)); - } - - return mfccOut; - } - - /* Constants */ - static constexpr float logStep = 1.8562979903656 / 27.0; - static constexpr float freqStep = 200.0 / 3; - static constexpr float minLogHz = 1000.0; - static constexpr float minLogMel = minLogHz / freqStep; - -protected: - /** - * @brief Project input frequency to Mel Scale. - * @param[in] freq - input frequency in floating point - * @param[in] useHTKmethod - bool to signal if HTK method is to be - * used for calculation - * @return Mel transformed frequency in floating point - **/ - static float MelScale(const float freq, - const bool useHTKMethod = true); - - /** - * @brief Inverse Mel transform - convert MEL warped frequency - * back to normal frequency - * @param[in] freq - Mel frequency in floating point - * @param[in] useHTKmethod - bool to signal if HTK method is to be - * used for calculation - * @return Real world frequency in floating point - **/ - static float InverseMelScale(const float melFreq, - const bool useHTKMethod = true); - - /** - * @brief Populates MEL energies after applying the MEL filter - * bank weights and adding them up to be placed into - * bins, according to the filter bank's first and last - * indices (pre-computed for each filter bank element - * by _CreateMelFilterBank 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 - */ - virtual bool ApplyMelFilterBank( - std::vector<float>& fftVec, - std::vector<std::vector<float>>& melFilterBank, - std::vector<int32_t>& filterBankFilterFirst, - std::vector<int32_t>& filterBankFilterLast, - std::vector<float>& melEnergies); - - /** - * @brief Converts the Mel energies for logarithmic scale - * @param[in/out] melEnergies - 1D vector of Mel energies - **/ - virtual void ConvertToLogarithmicScale(std::vector<float>& melEnergies); - - /** - * @brief Create a matrix used to calculate Discrete Cosine - * Transform. - * @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. - */ - virtual std::vector<float> CreateDCTMatrix( - const int32_t inputLength, - const int32_t coefficientCount); - - /** - * @brief Given the low and high Mel values, get the normaliser - * for weights to be applied when populating the filter - * bank. - * @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 - */ - virtual float GetMelFilterBankNormaliser( - const float& leftMel, - const float& rightMel, - const bool useHTKMethod); - -private: - - std::vector<float> _m_frame; - std::vector<float> _m_buffer; - std::vector<float> _m_melEnergies; - std::vector<float> _m_windowFunc; - std::vector<std::vector<float>> _m_melFilterBank; - std::vector<float> _m_dctMatrix; - std::vector<int32_t> _m_filterBankFilterFirst; - std::vector<int32_t> _m_filterBankFilterLast; - bool _m_filterBankInitialised; - - /** - * @brief Initialises the filter banks and the DCT matrix **/ - void _InitMelFilterBank(); - - /** - * @brief Signals whether the instance of MFCC has had its - * required buffers initialised - * @return True if initialised, false otherwise - **/ - bool _IsMelFilterBankInited(); - - /** - * @brief Create mel filter banks for MFCC calculation. - * @return 2D vector of floats - **/ - std::vector<std::vector<float>> _CreateMelFilterBank(); - - /** - * @brief Computes and populates internal memeber buffers used - * in MFCC feature calculation - * @param[in] audioData - 1D vector of 16-bit audio data - */ - void _MfccComputePreFeature(const std::vector<float>& audioData); - - /** @brief Computes the magnitude from an interleaved complex array */ - void _ConvertToPowerSpectrum(); - -}; - |