| /* |
| * 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 "Wav2LetterMfcc.hpp" |
| |
| #include "PlatformMath.hpp" |
| |
| #include <cfloat> |
| |
| namespace arm { |
| namespace app { |
| namespace audio { |
| |
| bool Wav2LetterMFCC::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) |
| { |
| 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(); |
| auto end = melFilterBank[bin].end(); |
| /* Avoid log of zero at later stages, same value used in librosa. |
| * The number was used during our default wav2letter model training. */ |
| float melEnergy = 1e-10; |
| const uint32_t firstIndex = filterBankFilterFirst[bin]; |
| const uint32_t lastIndex = std::min<uint32_t>(filterBankFilterLast[bin], fftVec.size() - 1); |
| |
| for (uint32_t i = firstIndex; i <= lastIndex && filterBankIter != end; ++i) { |
| melEnergy += (*filterBankIter++ * fftVec[i]); |
| } |
| |
| melEnergies[bin] = melEnergy; |
| } |
| |
| return true; |
| } |
| |
| void Wav2LetterMFCC::ConvertToLogarithmicScale( |
| std::vector<float>& melEnergies) |
| { |
| float maxMelEnergy = -FLT_MAX; |
| |
| /* Container for natural logarithms of mel energies. */ |
| std::vector <float> vecLogEnergies(melEnergies.size(), 0.f); |
| |
| /* Because we are taking natural logs, we need to multiply by log10(e). |
| * Also, for wav2letter model, we scale our log10 values by 10. */ |
| constexpr float multiplier = 10.0 * /* Default scalar. */ |
| 0.4342944819032518; /* log10f(std::exp(1.0))*/ |
| |
| /* Take log of the whole vector. */ |
| math::MathUtils::VecLogarithmF32(melEnergies, vecLogEnergies); |
| |
| /* Scale the log values and get the max. */ |
| for (auto iterM = melEnergies.begin(), iterL = vecLogEnergies.begin(); |
| iterM != melEnergies.end() && iterL != vecLogEnergies.end(); ++iterM, ++iterL) { |
| |
| *iterM = *iterL * multiplier; |
| |
| /* Save the max mel energy. */ |
| if (*iterM > maxMelEnergy) { |
| maxMelEnergy = *iterM; |
| } |
| } |
| |
| /* Clamp the mel energies. */ |
| constexpr float maxDb = 80.0; |
| const float clampLevelLowdB = maxMelEnergy - maxDb; |
| for (float & melEnergie : melEnergies) { |
| melEnergie = std::max(melEnergie, clampLevelLowdB); |
| } |
| } |
| |
| std::vector<float> Wav2LetterMFCC::CreateDCTMatrix( |
| const int32_t inputLength, |
| const int32_t coefficientCount) |
| { |
| std::vector<float> dctMatix(inputLength * coefficientCount); |
| |
| /* Orthonormal normalization. */ |
| const float normalizerK0 = 2 * math::MathUtils::SqrtF32(1.0f / |
| static_cast<float>(4*inputLength)); |
| const float normalizer = 2 * math::MathUtils::SqrtF32(1.0f / |
| static_cast<float>(2*inputLength)); |
| |
| const float angleIncr = M_PI/inputLength; |
| float angle = angleIncr; /* We start using it at k = 1 loop. */ |
| |
| /* First row of DCT will use normalizer K0 */ |
| for (int32_t n = 0; n < inputLength; ++n) { |
| dctMatix[n] = normalizerK0 /* cos(0) = 1 */; |
| } |
| |
| /* Second row (index = 1) onwards, we use standard normalizer. */ |
| for (int32_t k = 1, m = inputLength; k < coefficientCount; ++k, m += inputLength) { |
| for (int32_t n = 0; n < inputLength; ++n) { |
| dctMatix[m+n] = normalizer * |
| math::MathUtils::CosineF32((n + 0.5f) * angle); |
| } |
| angle += angleIncr; |
| } |
| return dctMatix; |
| } |
| |
| float Wav2LetterMFCC::GetMelFilterBankNormaliser( |
| const float& leftMel, |
| const float& rightMel, |
| const bool useHTKMethod) |
| { |
| /* Slaney normalization for mel weights. */ |
| return (2.0f / (MFCC::InverseMelScale(rightMel, useHTKMethod) - |
| MFCC::InverseMelScale(leftMel, useHTKMethod))); |
| } |
| |
| } /* namespace audio */ |
| } /* namespace app */ |
| } /* namespace arm */ |