source/use_case/ad/src/MelSpectrogram.cc - ml/ethos-u/ml-embedded-evaluation-kit - Gitiles

 /*
  * 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.
  */
 #include "MelSpectrogram.hpp"

 #include "PlatformMath.hpp"

 #include <cfloat>

 namespace arm {
 namespace app {
 namespace audio {

     MelSpecParams::MelSpecParams(
             const float samplingFreq,
             const uint32_t numFbankBins,
             const float melLoFreq,
             const float melHiFreq,
             const uint32_t frameLen,
             const bool useHtkMethod):
             m_samplingFreq(samplingFreq),
             m_numFbankBins(numFbankBins),
             m_melLoFreq(melLoFreq),
             m_melHiFreq(melHiFreq),
             m_frameLen(frameLen),

             /* Smallest power of 2 >= frame length. */
             m_frameLenPadded(pow(2, ceil((log(frameLen)/log(2))))),
             m_useHtkMethod(useHtkMethod)
     {}

     std::string MelSpecParams::Str()
     {
         char strC[1024];
         snprintf(strC, sizeof(strC) - 1, "\n   \
     \n\t Sampling frequency:         %f\
     \n\t Number of filter banks:     %u\
     \n\t Mel frequency limit (low):  %f\
     \n\t Mel frequency limit (high): %f\
     \n\t Frame length:               %u\
     \n\t Padded frame length:        %u\
     \n\t Using HTK for Mel scale:    %s\n",
                  this->m_samplingFreq, this->m_numFbankBins, this->m_melLoFreq,
                  this->m_melHiFreq, this->m_frameLen,
                  this->m_frameLenPadded, this->m_useHtkMethod ? "yes" : "no");
         return std::string{strC};
     }

     MelSpectrogram::MelSpectrogram(const MelSpecParams& params):
             _m_params(params),
             _m_filterBankInitialised(false)
     {
         this->_m_buffer = std::vector<float>(
                 this->_m_params.m_frameLenPadded, 0.0);
         this->_m_frame = std::vector<float>(
                 this->_m_params.m_frameLenPadded, 0.0);
         this->_m_melEnergies = std::vector<float>(
                 this->_m_params.m_numFbankBins, 0.0);

         this->_m_windowFunc = std::vector<float>(this->_m_params.m_frameLen);
         const float multiplier = 2 * M_PI / this->_m_params.m_frameLen;

         /* Create window function. */
         for (size_t i = 0; i < this->_m_params.m_frameLen; ++i) {
             this->_m_windowFunc[i] = (0.5 - (0.5 *
                                              math::MathUtils::CosineF32(static_cast<float>(i) * multiplier)));
         }

         math::MathUtils::FftInitF32(this->_m_params.m_frameLenPadded, this->_m_fftInstance);
         debug("Instantiated Mel Spectrogram object: %s\n", this->_m_params.Str().c_str());
     }

     void MelSpectrogram::Init()
     {
         this->_InitMelFilterBank();
     }

     float MelSpectrogram::MelScale(const float freq, const bool useHTKMethod)
     {
         if (useHTKMethod) {
             return 1127.0f * logf (1.0f + freq / 700.0f);
         } else {
             /* Slaney formula for mel scale. */
             float mel = freq / ms_freqStep;

             if (freq >= ms_minLogHz) {
                 mel = ms_minLogMel + logf(freq / ms_minLogHz) / ms_logStep;
             }
             return mel;
         }
     }

     float MelSpectrogram::InverseMelScale(const float melFreq, const bool useHTKMethod)
     {
         if (useHTKMethod) {
             return 700.0f * (expf (melFreq / 1127.0f) - 1.0f);
         } else {
             /* Slaney formula for inverse mel scale. */
             float freq = ms_freqStep * melFreq;

             if (melFreq >= ms_minLogMel) {
                 freq = ms_minLogHz * expf(ms_logStep * (melFreq - ms_minLogMel));
             }
             return freq;
         }
     }

     bool MelSpectrogram::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)
     {
         const size_t numBanks = melEnergies.size();

         if (numBanks != filterBankFilterFirst.size() ||
             numBanks != filterBankFilterLast.size()) {
             printf_err("unexpected filter bank lengths\n");
             return false;
         }

         for (size_t bin = 0; bin < numBanks; ++bin) {
             auto filterBankIter = melFilterBank[bin].begin();
             float melEnergy = FLT_MIN; /* Avoid log of zero at later stages */
             int32_t firstIndex = filterBankFilterFirst[bin];
             int32_t lastIndex = filterBankFilterLast[bin];

             for (int i = firstIndex; i <= lastIndex; ++i) {
                 float energyRep = math::MathUtils::SqrtF32(fftVec[i]);
                 melEnergy += (*filterBankIter++ * energyRep);
             }

             melEnergies[bin] = melEnergy;
         }

         return true;
     }

     void MelSpectrogram::ConvertToLogarithmicScale(std::vector<float>& melEnergies)
     {
         for (size_t bin = 0; bin < melEnergies.size(); ++bin) {
             melEnergies[bin] = logf(melEnergies[bin]);
         }
     }

     void MelSpectrogram::_ConvertToPowerSpectrum()
     {
         const uint32_t halfDim = this->_m_params.m_frameLenPadded / 2;

         /* Handle this special case. */
         float firstEnergy = this->_m_buffer[0] * this->_m_buffer[0];
         float lastEnergy = this->_m_buffer[1] * this->_m_buffer[1];

         math::MathUtils::ComplexMagnitudeSquaredF32(
                 this->_m_buffer.data(),
                 this->_m_buffer.size(),
                 this->_m_buffer.data(),
                 this->_m_buffer.size()/2);

         this->_m_buffer[0] = firstEnergy;
         this->_m_buffer[halfDim] = lastEnergy;
     }

     float MelSpectrogram::GetMelFilterBankNormaliser(
             const float&    leftMel,
             const float&    rightMel,
             const bool      useHTKMethod)
     {
         UNUSED(leftMel);
         UNUSED(rightMel);
         UNUSED(useHTKMethod);

         /* By default, no normalisation => return 1 */
         return 1.f;
     }

     void MelSpectrogram::_InitMelFilterBank()
     {
         if (!this->_IsMelFilterBankInited()) {
             this->_m_melFilterBank = this->_CreateMelFilterBank();
             this->_m_filterBankInitialised = true;
         }
     }

     bool MelSpectrogram::_IsMelFilterBankInited()
     {
         return this->_m_filterBankInitialised;
     }

     std::vector<float> MelSpectrogram::ComputeMelSpec(const std::vector<int16_t>& audioData, float trainingMean)
     {
         this->_InitMelFilterBank();

         /* TensorFlow way of normalizing .wav data to (-1, 1). */
         constexpr float normaliser = 1.0/(1<<15);
         for (size_t i = 0; i < this->_m_params.m_frameLen; ++i) {
             this->_m_frame[i] = static_cast<float>(audioData[i]) * normaliser;
         }

         /* Apply window function to input frame. */
         for(size_t i = 0; i < this->_m_params.m_frameLen; ++i) {
             this->_m_frame[i] *= this->_m_windowFunc[i];
         }

         /* Set remaining frame values to 0. */
         std::fill(this->_m_frame.begin() + this->_m_params.m_frameLen,this->_m_frame.end(), 0);

         /* Compute FFT. */
         math::MathUtils::FftF32(this->_m_frame, this->_m_buffer, this->_m_fftInstance);

         /* Convert to power spectrum. */
         this->_ConvertToPowerSpectrum();

         /* Apply mel filterbanks. */
         if (!this->ApplyMelFilterBank(this->_m_buffer,
                                       this->_m_melFilterBank,
                                       this->_m_filterBankFilterFirst,
                                       this->_m_filterBankFilterLast,
                                       this->_m_melEnergies)) {
             printf_err("Failed to apply MEL filter banks\n");
         }

         /* Convert to logarithmic scale */
         this->ConvertToLogarithmicScale(this->_m_melEnergies);

         /* Perform mean subtraction. */
         for (auto& energy:this->_m_melEnergies) {
             energy -= trainingMean;
         }

         return this->_m_melEnergies;
     }

     std::vector<std::vector<float>> MelSpectrogram::_CreateMelFilterBank()
     {
         size_t numFftBins = this->_m_params.m_frameLenPadded / 2;
         float fftBinWidth = static_cast<float>(this->_m_params.m_samplingFreq) / this->_m_params.m_frameLenPadded;

         float melLowFreq = MelSpectrogram::MelScale(this->_m_params.m_melLoFreq,
                                           this->_m_params.m_useHtkMethod);
         float melHighFreq = MelSpectrogram::MelScale(this->_m_params.m_melHiFreq,
                                            this->_m_params.m_useHtkMethod);
         float melFreqDelta = (melHighFreq - melLowFreq) / (this->_m_params.m_numFbankBins + 1);

         std::vector<float> thisBin = std::vector<float>(numFftBins);
         std::vector<std::vector<float>> melFilterBank(
                 this->_m_params.m_numFbankBins);
         this->_m_filterBankFilterFirst =
                 std::vector<int32_t>(this->_m_params.m_numFbankBins);
         this->_m_filterBankFilterLast =
                 std::vector<int32_t>(this->_m_params.m_numFbankBins);

         for (size_t bin = 0; bin < this->_m_params.m_numFbankBins; bin++) {
             float leftMel = melLowFreq + bin * melFreqDelta;
             float centerMel = melLowFreq + (bin + 1) * melFreqDelta;
             float rightMel = melLowFreq + (bin + 2) * melFreqDelta;

             int32_t firstIndex = -1;
             int32_t lastIndex = -1;
             const float normaliser = this->GetMelFilterBankNormaliser(leftMel, rightMel, this->_m_params.m_useHtkMethod);

             for (size_t i = 0; i < numFftBins; ++i) {
                 float freq = (fftBinWidth * i); /* Center freq of this fft bin. */
                 float mel = MelSpectrogram::MelScale(freq, this->_m_params.m_useHtkMethod);
                 thisBin[i] = 0.0;

                 if (mel > leftMel && mel < rightMel) {
                     float weight;
                     if (mel <= centerMel) {
                         weight = (mel - leftMel) / (centerMel - leftMel);
                     } else {
                         weight = (rightMel - mel) / (rightMel - centerMel);
                     }

                     thisBin[i] = weight * normaliser;
                     if (firstIndex == -1) {
                         firstIndex = i;
                     }
                     lastIndex = i;
                 }
             }

             this->_m_filterBankFilterFirst[bin] = firstIndex;
             this->_m_filterBankFilterLast[bin] = lastIndex;

             /* Copy the part we care about. */
             for (int32_t i = firstIndex; i <= lastIndex; ++i) {
                 melFilterBank[bin].push_back(thisBin[i]);
             }
         }

         return melFilterBank;
     }

 } /* namespace audio */
 } /* namespace app */
 } /* namespace arm */
	/*
	* 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.
	*/
	#include "MelSpectrogram.hpp"

	#include "PlatformMath.hpp"

	#include <cfloat>

	namespace arm {
	namespace app {
	namespace audio {

	MelSpecParams::MelSpecParams(
	const float samplingFreq,
	const uint32_t numFbankBins,
	const float melLoFreq,
	const float melHiFreq,
	const uint32_t frameLen,
	const bool useHtkMethod):
	m_samplingFreq(samplingFreq),
	m_numFbankBins(numFbankBins),
	m_melLoFreq(melLoFreq),
	m_melHiFreq(melHiFreq),
	m_frameLen(frameLen),

	/* Smallest power of 2 >= frame length. */
	m_frameLenPadded(pow(2, ceil((log(frameLen)/log(2))))),
	m_useHtkMethod(useHtkMethod)
	{}

	std::string MelSpecParams::Str()
	{
	char strC[1024];
	snprintf(strC, sizeof(strC) - 1, "\n \
	\n\t Sampling frequency: %f\
	\n\t Number of filter banks: %u\
	\n\t Mel frequency limit (low): %f\
	\n\t Mel frequency limit (high): %f\
	\n\t Frame length: %u\
	\n\t Padded frame length: %u\
	\n\t Using HTK for Mel scale: %s\n",
	this->m_samplingFreq, this->m_numFbankBins, this->m_melLoFreq,
	this->m_melHiFreq, this->m_frameLen,
	this->m_frameLenPadded, this->m_useHtkMethod ? "yes" : "no");
	return std::string{strC};
	}

	MelSpectrogram::MelSpectrogram(const MelSpecParams& params):
	_m_params(params),
	_m_filterBankInitialised(false)
	{
	this->_m_buffer = std::vector<float>(
	this->_m_params.m_frameLenPadded, 0.0);
	this->_m_frame = std::vector<float>(
	this->_m_params.m_frameLenPadded, 0.0);
	this->_m_melEnergies = std::vector<float>(
	this->_m_params.m_numFbankBins, 0.0);

	this->_m_windowFunc = std::vector<float>(this->_m_params.m_frameLen);
	const float multiplier = 2 * M_PI / this->_m_params.m_frameLen;

	/* Create window function. */
	for (size_t i = 0; i < this->_m_params.m_frameLen; ++i) {
	this->_m_windowFunc[i] = (0.5 - (0.5 *
	math::MathUtils::CosineF32(static_cast<float>(i) * multiplier)));
	}

	math::MathUtils::FftInitF32(this->_m_params.m_frameLenPadded, this->_m_fftInstance);
	debug("Instantiated Mel Spectrogram object: %s\n", this->_m_params.Str().c_str());
	}

	void MelSpectrogram::Init()
	{
	this->_InitMelFilterBank();
	}

	float MelSpectrogram::MelScale(const float freq, const bool useHTKMethod)
	{
	if (useHTKMethod) {
	return 1127.0f * logf (1.0f + freq / 700.0f);
	} else {
	/* Slaney formula for mel scale. */
	float mel = freq / ms_freqStep;

	if (freq >= ms_minLogHz) {
	mel = ms_minLogMel + logf(freq / ms_minLogHz) / ms_logStep;
	}
	return mel;
	}
	}

	float MelSpectrogram::InverseMelScale(const float melFreq, const bool useHTKMethod)
	{
	if (useHTKMethod) {
	return 700.0f * (expf (melFreq / 1127.0f) - 1.0f);
	} else {
	/* Slaney formula for inverse mel scale. */
	float freq = ms_freqStep * melFreq;

	if (melFreq >= ms_minLogMel) {
	freq = ms_minLogHz * expf(ms_logStep * (melFreq - ms_minLogMel));
	}
	return freq;
	}
	}

	bool MelSpectrogram::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)
	{
	const size_t numBanks = melEnergies.size();

	if (numBanks != filterBankFilterFirst.size() \|\|
	numBanks != filterBankFilterLast.size()) {
	printf_err("unexpected filter bank lengths\n");
	return false;
	}

	for (size_t bin = 0; bin < numBanks; ++bin) {
	auto filterBankIter = melFilterBank[bin].begin();
	float melEnergy = FLT_MIN; /* Avoid log of zero at later stages */
	int32_t firstIndex = filterBankFilterFirst[bin];
	int32_t lastIndex = filterBankFilterLast[bin];

	for (int i = firstIndex; i <= lastIndex; ++i) {
	float energyRep = math::MathUtils::SqrtF32(fftVec[i]);
	melEnergy += (filterBankIter++ energyRep);
	}

	melEnergies[bin] = melEnergy;
	}

	return true;
	}

	void MelSpectrogram::ConvertToLogarithmicScale(std::vector<float>& melEnergies)
	{
	for (size_t bin = 0; bin < melEnergies.size(); ++bin) {
	melEnergies[bin] = logf(melEnergies[bin]);
	}
	}

	void MelSpectrogram::_ConvertToPowerSpectrum()
	{
	const uint32_t halfDim = this->_m_params.m_frameLenPadded / 2;

	/* Handle this special case. */
	float firstEnergy = this->_m_buffer[0] * this->_m_buffer[0];
	float lastEnergy = this->_m_buffer[1] * this->_m_buffer[1];

	math::MathUtils::ComplexMagnitudeSquaredF32(
	this->_m_buffer.data(),
	this->_m_buffer.size(),
	this->_m_buffer.data(),
	this->_m_buffer.size()/2);

	this->_m_buffer[0] = firstEnergy;
	this->_m_buffer[halfDim] = lastEnergy;
	}

	float MelSpectrogram::GetMelFilterBankNormaliser(
	const float& leftMel,
	const float& rightMel,
	const bool useHTKMethod)
	{
	UNUSED(leftMel);
	UNUSED(rightMel);
	UNUSED(useHTKMethod);

	/* By default, no normalisation => return 1 */
	return 1.f;
	}

	void MelSpectrogram::_InitMelFilterBank()
	{
	if (!this->_IsMelFilterBankInited()) {
	this->_m_melFilterBank = this->_CreateMelFilterBank();
	this->_m_filterBankInitialised = true;
	}
	}

	bool MelSpectrogram::_IsMelFilterBankInited()
	{
	return this->_m_filterBankInitialised;
	}

	std::vector<float> MelSpectrogram::ComputeMelSpec(const std::vector<int16_t>& audioData, float trainingMean)
	{
	this->_InitMelFilterBank();

	/* TensorFlow way of normalizing .wav data to (-1, 1). */
	constexpr float normaliser = 1.0/(1<<15);
	for (size_t i = 0; i < this->_m_params.m_frameLen; ++i) {
	this->_m_frame[i] = static_cast<float>(audioData[i]) * normaliser;
	}

	/* Apply window function to input frame. */
	for(size_t i = 0; i < this->_m_params.m_frameLen; ++i) {
	this->_m_frame[i] *= this->_m_windowFunc[i];
	}

	/* Set remaining frame values to 0. */
	std::fill(this->_m_frame.begin() + this->_m_params.m_frameLen,this->_m_frame.end(), 0);

	/* Compute FFT. */
	math::MathUtils::FftF32(this->_m_frame, this->_m_buffer, this->_m_fftInstance);

	/* Convert to power spectrum. */
	this->_ConvertToPowerSpectrum();

	/* Apply mel filterbanks. */
	if (!this->ApplyMelFilterBank(this->_m_buffer,
	this->_m_melFilterBank,
	this->_m_filterBankFilterFirst,
	this->_m_filterBankFilterLast,
	this->_m_melEnergies)) {
	printf_err("Failed to apply MEL filter banks\n");
	}

	/* Convert to logarithmic scale */
	this->ConvertToLogarithmicScale(this->_m_melEnergies);

	/* Perform mean subtraction. */
	for (auto& energy:this->_m_melEnergies) {
	energy -= trainingMean;
	}

	return this->_m_melEnergies;
	}

	std::vector<std::vector<float>> MelSpectrogram::_CreateMelFilterBank()
	{
	size_t numFftBins = this->_m_params.m_frameLenPadded / 2;
	float fftBinWidth = static_cast<float>(this->_m_params.m_samplingFreq) / this->_m_params.m_frameLenPadded;

	float melLowFreq = MelSpectrogram::MelScale(this->_m_params.m_melLoFreq,
	this->_m_params.m_useHtkMethod);
	float melHighFreq = MelSpectrogram::MelScale(this->_m_params.m_melHiFreq,
	this->_m_params.m_useHtkMethod);
	float melFreqDelta = (melHighFreq - melLowFreq) / (this->_m_params.m_numFbankBins + 1);

	std::vector<float> thisBin = std::vector<float>(numFftBins);
	std::vector<std::vector<float>> melFilterBank(
	this->_m_params.m_numFbankBins);
	this->_m_filterBankFilterFirst =
	std::vector<int32_t>(this->_m_params.m_numFbankBins);
	this->_m_filterBankFilterLast =
	std::vector<int32_t>(this->_m_params.m_numFbankBins);

	for (size_t bin = 0; bin < this->_m_params.m_numFbankBins; bin++) {
	float leftMel = melLowFreq + bin * melFreqDelta;
	float centerMel = melLowFreq + (bin + 1) * melFreqDelta;
	float rightMel = melLowFreq + (bin + 2) * melFreqDelta;

	int32_t firstIndex = -1;
	int32_t lastIndex = -1;
	const float normaliser = this->GetMelFilterBankNormaliser(leftMel, rightMel, this->_m_params.m_useHtkMethod);

	for (size_t i = 0; i < numFftBins; ++i) {
	float freq = (fftBinWidth * i); /* Center freq of this fft bin. */
	float mel = MelSpectrogram::MelScale(freq, this->_m_params.m_useHtkMethod);
	thisBin[i] = 0.0;

	if (mel > leftMel && mel < rightMel) {
	float weight;
	if (mel <= centerMel) {
	weight = (mel - leftMel) / (centerMel - leftMel);
	} else {
	weight = (rightMel - mel) / (rightMel - centerMel);
	}

	thisBin[i] = weight * normaliser;
	if (firstIndex == -1) {
	firstIndex = i;
	}
	lastIndex = i;
	}
	}

	this->_m_filterBankFilterFirst[bin] = firstIndex;
	this->_m_filterBankFilterLast[bin] = lastIndex;

	/* Copy the part we care about. */
	for (int32_t i = firstIndex; i <= lastIndex; ++i) {
	melFilterBank[bin].push_back(thisBin[i]);
	}
	}

	return melFilterBank;
	}

	} /* namespace audio */
	} /* namespace app */
	} /* namespace arm */