qsinewavevalidator_p.h

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// Copyright (C) 2024 The Qt Company Ltd.
// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR GPL-3.0-only
 
#ifndef QSINEWAVEVALIDATOR_H
#define QSINEWAVEVALIDATOR_H
 
//
//  W A R N I N G
//  -------------
//
// This file is not part of the Qt API. It exists purely as an
// implementation detail. This header file may change from version to
// version without notice, or even be removed.
//
// We mean it.
//
 
#include <array>
 
#include <QtCore/qtconfigmacros.h>
 
QT_BEGIN_NAMESPACE
 
// sine wave validator: accumulating peak value and result of passing the signal through a notch
// filter. A sine wave of that frequency should not pass the notch filter, so if the peak exceeds a
// small threshold, it we can detect discontinuities for example.
struct QSineWaveValidator
{
    QSineWaveValidator(const QSineWaveValidator &) = delete;
    QSineWaveValidator(QSineWaveValidator &&) = delete;
    QSineWaveValidator &operator=(const QSineWaveValidator &) = delete;
    QSineWaveValidator &operator=(QSineWaveValidator &&) = delete;
 
    QSineWaveValidator(float notchFrequency, float sampleRate);
 
    void feedSample(float sample);
 
    float peak() const { return accumPeak; }
    float notchPeak() const;
 
private:
    float a0, a1, a2;
    float b0, b1, b2;
 
    std::array<float, 3> x{}, y{};
    int framesBeforeAnalysis = 128; // unscientific estimate, larger than the transient response
                                    // time for the IIR filter
    int pendingFramesBeforeAnalysis = framesBeforeAnalysis;
 
    float accumPeak{};
    float accumNotchPeak{};
};
 
QT_END_NAMESPACE
 
#endif // QSINEWAVEVALIDATOR_H