MLECO-2079 Adding the C++ KWS example

Signed-off-by: Eanna O Cathain <eanna.ocathain@arm.com>
Change-Id: I81899bbfaada32f478c2e2fc6441eabb94d8d0fc

1 files changed, 78 insertions, 0 deletions

diff --git a/samples/SpeechRecognition/include/Wav2LetterMFCC.hpp b/samples/SpeechRecognition/include/Wav2LetterMFCC.hpp
new file mode 100644
index 0000000000..aa88aafb3b
--- /dev/null
+++ b/samples/SpeechRecognition/include/Wav2LetterMFCC.hpp
@@ -0,0 +1,78 @@
+//
+// Copyright © 2020 Arm Ltd and Contributors. All rights reserved.
+// SPDX-License-Identifier: MIT
+//
+#pragma once
+
+#include "MFCC.hpp"
+
+/* Class to provide Wav2Letter specific MFCC calculation requirements. */
+class Wav2LetterMFCC : public MFCC 
+{
+
+public:
+    explicit Wav2LetterMFCC(const MfccParams& params)
+        :  MFCC(params)
+    {}
+
+    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;
+};
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