qsinewavevalidator.cpp

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// Copyright (C) 2024 The Qt Company Ltd.

// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR GPL-3.0-only

#include "qsinewavevalidator_p.h"

#include <QtCore/qmath.h>

#include <QtCore/QDebug>

QT_BEGIN_NAMESPACE

QSineWaveValidator::QSineWaveValidator(float notchFrequency, float sampleRate)

    using namespace std;

    float pi = static_cast<float>(M_PI);

    float f0 = notchFrequency;

    float Fs = sampleRate;

    float Q = 1 / sqrt(2.f); // higher Q gives narrow bandwidth, but requires a larger number of

    // frames during the transient

    // compare https://webaudio.github.io/Audio-EQ-Cookbook/Audio-EQ-Cookbook.txt

    float w0 = 2 * pi * f0 / Fs;

    float alpha = sin(w0) / (2 * Q);

    b0 = 1;

    b1 = -2 * cos(w0);

    b2 = 1;

    a0 = 1 + alpha;

    a1 = -2 * cos(w0);

    a2 = 1 - alpha;

void QSineWaveValidator::feedSample(float sample)

    if (pendingFramesBeforeAnalysis == framesBeforeAnalysis) {

        x.fill(sample);

        y.fill(b0 / a0 * sample);

    x[2] = x[1];

    x[1] = x[0];

    x[0] = sample;

    y[2] = y[1];

    y[1] = y[0];

    y[0] = (b0 / a0) * x[0] + (b1 / a0) * x[1] + (b2 / a0) * x[2] - (a1 / a0) * y[1]

            - (a2 / a0) * y[2];

    accumPeak = std::max(std::abs(sample), accumPeak);

    if (pendingFramesBeforeAnalysis) {

        pendingFramesBeforeAnalysis -= 1;

        return;

    accumNotchPeak = std::max(std::abs(y[0]), accumNotchPeak);

float QSineWaveValidator::notchPeak() const

    if (pendingFramesBeforeAnalysis)

        qWarning() << "notchPeak during initial frames. Result will not be accurate";

    return accumNotchPeak;

QT_END_NAMESPACE