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