audiolevelmeter.h - mozsearch

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// Copyright (C) 2025 The Qt Company Ltd.

// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR BSD-3-Clause

#ifndef AUDIOLEVELMETER_H

#define AUDIOLEVELMETER_H

#include <QWidget>

#include <QThread>

#include <queue>

#include <chrono>

#include <QTimer>

#include <QAudioBuffer>

QT_BEGIN_NAMESPACE

class QToolButton;

class QLabel;

QT_END_NAMESPACE

using namespace std::chrono_literals;

using std::chrono::milliseconds;

// Constants used by AudioLevelMeter and MeterChannel

static constexpr int WIDGET_WIDTH = 34;

static constexpr int MAX_CHANNELS = 8;

static constexpr auto PEAK_COLOR = "#1F9B5D";

static constexpr auto RMS_COLOR = "#28C878";

static constexpr milliseconds RMS_WINDOW = 400ms;

static constexpr milliseconds PEAK_LABEL_HOLD_TIME = 2000ms;

static constexpr milliseconds DECAY_EASE_IN_TIME = 160ms;

static constexpr milliseconds UPDATE_INTERVAL = 16ms; // Assuming 60 Hz refresh rate.

static constexpr float DB_DECAY_PER_SECOND = 20.0f;

static constexpr float DB_DECAY_PER_UPDATE =

        DB_DECAY_PER_SECOND / (1000 / UPDATE_INTERVAL.count());

static constexpr float DB_MAX = 0.0f;

static constexpr float DB_SILENCE = -60.0f;

static constexpr float DB_MIN = -90.0f;

// A struct used by BufferAnalyzer to emit its results back to AudioLevelMeter

struct BufferValues {

    BufferValues(int nChannels) : peaks(nChannels, 0.0f), squares(nChannels, 0.0f) {}

    std::vector<float> peaks;

    std::vector<float> squares;

};

// A worker class analyzing incoming buffers on a separate worker thread

class BufferAnalyzer : public QObject

    Q_OBJECT

public:

    void requestStop() { m_stopRequested.store(true); }

public slots:

    void analyzeBuffer(const QAudioBuffer &buffer, int maxChannelsToAnalyze);

signals:

    void valuesReady(const BufferValues &values);

private:

    std::atomic<bool> m_stopRequested = false;

};

// A custom QWidget representing an audio channel in the audio level meter. It serves

// both as a model for the channels's peak and RMS values and as a view using the overrided

// paintEvent()

class MeterChannel : public QWidget

    Q_OBJECT

    friend class AudioLevelMeter;

private:

    explicit MeterChannel(QWidget *parent = nullptr);

    void paintEvent(QPaintEvent *event) override;

    void activate();

    void deactivate();

    void updatePeak(float peak);

    void updateRms(float sumOfSquaresForOneBuffer, milliseconds duration, int frameCount);

    void clearRmsData();

    void decayPeak();

    void decayRms();

    float normalize(float dB);

    float m_peakDecayRate = 0.0f;

    float m_rmsDecayRate = 0.0f;

    float m_peak = DB_MIN;

    float m_rms = DB_MIN;

    float m_sumOfSquares = 0.0f;

    std::queue<float> m_sumOfSquaresQueue{};

    QBrush m_peakBrush{PEAK_COLOR};

    QBrush m_rmsBrush{RMS_COLOR};

};

// The audio level meter´s parent widget class. It acts as a controller

// for the MeterChannel widgets and the BufferAnalyzer worker.

class AudioLevelMeter : public QWidget

    Q_OBJECT

public:

    explicit AudioLevelMeter(QWidget *parent = nullptr);

    ~AudioLevelMeter() {

        m_analyzerThread.requestInterruption();

        m_bufferAnalyzer->requestStop();

        m_analyzerThread.quit();

        m_analyzerThread.wait();

};

signals:

    void newBuffer(const QAudioBuffer &buffer, int nChannels);

public slots:

    void onAudioBufferReceived(const QAudioBuffer &buffer);

    void deactivate();

private slots:

    void toggleOnOff();

    void updateValues(const BufferValues &values);

    void updateBars();

    void resetPeakLabel();

private:

    void activate();

    void updateChannelCount(int nCh);

    void updatePeakLabel(float peak);

    void clearAllRmsData();

    bool m_isOn = true;

    bool m_isActive = false;

    QList<MeterChannel *> m_channels{MAX_CHANNELS};

    int m_channelCount = 0;

    milliseconds m_bufferDurationMs = 0ms;

    int m_frameCount = 0;

    float m_highestPeak = 0.0f;

    QTimer m_updateTimer;

    QTimer m_deactivationTimer;

    QTimer m_peakLabelHoldTimer;

    QLabel *m_peakLabel = nullptr;

    QToolButton *m_onOffButton = nullptr;

    BufferAnalyzer *m_bufferAnalyzer = nullptr;

    QThread m_analyzerThread;

};

#endif // AUDIOLEVELMETER_H