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Diffstat (limited to 'samples/SpeechRecognition/include/Preprocess.hpp')
| -rw-r--r-- | samples/SpeechRecognition/include/Preprocess.hpp | 175 |
1 files changed, 175 insertions, 0 deletions
diff --git a/samples/SpeechRecognition/include/Preprocess.hpp b/samples/SpeechRecognition/include/Preprocess.hpp new file mode 100644 index 0000000000..80c568439b --- /dev/null +++ b/samples/SpeechRecognition/include/Preprocess.hpp @@ -0,0 +1,175 @@ +// +// Copyright © 2020 Arm Ltd and Contributors. All rights reserved. +// SPDX-License-Identifier: MIT +// + +#pragma once + +#include "DataStructures.hpp" +#include "SlidingWindow.hpp" +#include <numeric> +#include "MFCC.hpp" + +/* Class to facilitate pre-processing calculation for Wav2Letter model + * for ASR */ +using AudioWindow = SlidingWindow <const float>; + +class Preprocess +{ +public: + + MFCC _m_mfcc; /* MFCC instance */ + + /* Actual buffers to be populated */ + Array2d<float> _m_mfccBuf; /* Contiguous buffer 1D: MFCC */ + Array2d<float> _m_delta1Buf; /* Contiguous buffer 1D: Delta 1 */ + Array2d<float> _m_delta2Buf; /* Contiguous buffer 1D: Delta 2 */ + + uint32_t _m_windowLen; /* Window length for MFCC */ + uint32_t _m_windowStride; /* Window stride len for MFCC */ + AudioWindow _m_window; /* Sliding window */ + + /** + * @brief Constructor + * @param[in] numMfccFeatures number of MFCC features per window + * @param[in] windowLen number of elements in a window + * @param[in] windowStride stride (in number of elements) for + * moving the window + * @param[in] numMfccVectors number of MFCC vectors per window + */ + Preprocess( + const uint32_t windowLen, + const uint32_t windowStride, + const MFCC mfccInst); + Preprocess() = delete; + ~Preprocess(); + + /** + * @brief Calculates the features required from audio data. This + * includes MFCC, first and second order deltas, + * normalisation and finally, quantisation. The tensor is + * populated with feature from a given window placed along + * in a single row. + * @param[in] audioData pointer to the first element of audio data + * @param[in] audioDataLen number of elements in the audio data + * @param[in] tensor tensor to be populated + * @return true if successful, false in case of error. + */ + bool Invoke(const float* audioData, + const uint32_t audioDataLen, + std::vector<int8_t>& output, + int quantOffset, + float quantScale); + + +protected: + /** + * @brief Computes the first and second order deltas for the + * MFCC buffers - they are assumed to be populated. + * + * @param[in] mfcc MFCC buffers + * @param[out] delta1 result of the first diff computation + * @param[out] delta2 result of the second diff computation + * + * @return true if successful, false otherwise + */ + static bool _ComputeDeltas(Array2d<float>& mfcc, + Array2d<float>& delta1, + Array2d<float>& delta2); + + /** + * @brief Given a 2D vector of floats, computes the mean + * @param[in] vec vector of vector of floats + * @return mean value + */ + static float _GetMean(Array2d<float>& vec); + + /** + * @brief Given a 2D vector of floats, computes the stddev + * @param[in] vec vector of vector of floats + * @param[in] mean mean value of the vector passed in + * @return stddev value + */ + static float _GetStdDev(Array2d<float>& vec, + const float mean); + + /** + * @brief Given a 2D vector of floats, normalises it using + * the mean and the stddev + * @param[in/out] vec vector of vector of floats + * @return + */ + static void _NormaliseVec(Array2d<float>& vec); + + /** + * @brief Normalises the MFCC and delta buffers + * @return + */ + void _Normalise(); + + /** + * @brief Given the quantisation and data type limits, computes + * the quantised values of a floating point input data. + * @param[in] elem Element to be quantised + * @param[in] quantScale Scale + * @param[in] quantOffset Offset + * @param[in] minVal Numerical limit - minimum + * @param[in] maxVal Numerical limit - maximum + * @return floating point quantised value + */ + static float _GetQuantElem( + const float elem, + const float quantScale, + const int quantOffset, + const float minVal, + const float maxVal); + + /** + * @brief Quantises the MFCC and delta buffers, and places them + * in the output buffer. While doing so, it transposes + * the data. Reason: Buffers in this class are arranged + * for "time" axis to be row major. Primary reason for + * this being the convolution speed up (as we can use + * contiguous memory). The output, however, requires the + * time axis to be in column major arrangement. + * @param[in] outputBuf pointer to the output buffer + * @param[in] outputBufSz output buffer's size + * @param[in] quantScale quantisation scale + * @param[in] quantOffset quantisation offset + */ + template <typename T> + bool _Quantise(T* outputBuf, int quantOffset, float quantScale) + { + /* Populate */ + T* outputBufMfcc = outputBuf; + T* outputBufD1 = outputBuf + this->_m_mfcc._m_params.m_numMfccFeatures; + T* outputBufD2 = outputBufD1 + this->_m_mfcc._m_params.m_numMfccFeatures; + const uint32_t ptrIncr = this->_m_mfcc._m_params.m_numMfccFeatures * 2; /* (3 vectors - 1 vector) */ + + const float minVal = std::numeric_limits<T>::min(); + const float maxVal = std::numeric_limits<T>::max(); + + /* We need to do a transpose while copying and concatenating + * the tensor*/ + for (uint32_t j = 0; j < this->_m_mfcc._m_params.m_numMfccVectors; ++j) { + for (uint32_t i = 0; i < this->_m_mfcc._m_params.m_numMfccFeatures; ++i) + { + *outputBufMfcc++ = static_cast<T>(this->_GetQuantElem( + this->_m_mfccBuf(i, j), quantScale, + quantOffset, minVal, maxVal)); + *outputBufD1++ = static_cast<T>(this->_GetQuantElem( + this->_m_delta1Buf(i, j), quantScale, + quantOffset, minVal, maxVal)); + *outputBufD2++ = static_cast<T>(this->_GetQuantElem( + this->_m_delta2Buf(i, j), quantScale, + quantOffset, minVal, maxVal)); + } + outputBufMfcc += ptrIncr; + outputBufD1 += ptrIncr; + outputBufD2 += ptrIncr; + } + + return true; + } +}; + |