audiogenerationutils_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 AUDIOGENERATIONUTILS_H
#define AUDIOGENERATIONUTILS_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 <QtMultimedia/qaudioformat.h>
#include <QtMultimedia/qaudiobuffer.h>
#include <QtCore/qiodevice.h>
#include <QtCore/qmath.h>
#include <QtCore/qtemporaryfile.h>
 
#include <chrono>
#include <cmath>
#include <cstdint>
#include <limits>
#include <memory>
 
QT_BEGIN_NAMESPACE
 
class SineWaveGenerator
{
public:
    static constexpr double tau = 2 * M_PI;
 
    SineWaveGenerator(std::uint32_t phase, std::uint32_t increment)
        : m_phase(phase), m_increment(increment)
    {
    }
 
    SineWaveGenerator(double frequency, double sampleRate, double phase = 0.0)
        : SineWaveGenerator(phaseToFixedPoint(phase), incrementFromFrequency(frequency, sampleRate))
    {
    }
 
    static std::uint32_t phaseToFixedPoint(double phase)
    {
        constexpr double scale = static_cast<double>(std::numeric_limits<std::uint32_t>::max());
        double normalizedPhase = std::fmod(phase, tau);
        if (normalizedPhase < 0.0)
            normalizedPhase += tau;
        return std::uint32_t((normalizedPhase / tau) * scale);
    }
 
    static std::uint32_t incrementFromFrequency(double frequency, double sampleRate)
    {
        constexpr double scale = static_cast<double>(std::numeric_limits<std::uint32_t>::max());
        return std::uint32_t((frequency / sampleRate) * scale);
    }
 
    double getSample() const
    {
        constexpr double scale = static_cast<double>(UINT32_MAX);
        return std::sin(tau * (static_cast<double>(m_phase) / scale));
    }
 
    void advance()
    {
        m_phase += m_increment; // wraps naturally
    }
 
    double operator()()
    {
        double result = getSample();
        advance();
        return result;
    }
 
private:
    std::uint32_t m_phase;
    std::uint32_t m_increment;
};
 
class SineWaveSignal
{
    class iterator
    {
    public:
        using iterator_category = std::input_iterator_tag;
        using value_type = double;
        using difference_type = std::ptrdiff_t;
        using pointer = void;
        using reference = double;
 
        iterator(std::uint32_t phase, std::uint32_t increment) : m_generator(phase, increment) { }
 
        double operator*() const { return m_generator.getSample(); }
 
        iterator &operator++()
        {
            m_generator.advance();
            return *this;
        }
 
        bool operator!=(std::nullptr_t) const
        {
            return true; // infinite range
        }
 
    private:
        SineWaveGenerator m_generator;
    };
 
public:
    SineWaveSignal(double frequency, double sample_rate, double phase = 0.0)
        : m_phase(SineWaveGenerator::phaseToFixedPoint(phase)),
          m_increment(SineWaveGenerator::incrementFromFrequency(frequency, sample_rate))
    {
    }
 
    iterator begin() const
    {
        return iterator{
            m_phase,
            m_increment,
        };
    }
    std::nullptr_t end() const { return nullptr; }
 
private:
    std::uint32_t m_phase;
    std::uint32_t m_increment;
};
 
unsigned char *writeSineSample(unsigned char *ptr, QAudioFormat::SampleFormat sampleFormat,
                               qreal x);
 
QByteArray createSineWaveData(const QAudioFormat &format, std::chrono::microseconds duration,
                              qint32 sampleIndex = 0, qreal frequency = 500, qreal volume = 0.8);
 
// Writes a mono, 16-bit PCM WAV file containing a sine wave to a new temporary file and
// returns it (already closed, ready to be opened for reading via its fileName()).
std::unique_ptr<QTemporaryFile> makeMonoPcm16WavFile(int sampleRate,
                                                     std::chrono::microseconds duration,
                                                     qreal frequency, qreal volume = 0.8);
 
class SineWaveIODevice : public QIODevice
{
public:
    explicit SineWaveIODevice(const QAudioFormat &format, qreal frequency = 500, qreal volume = 0.8)
        : m_format(format), m_generator(frequency, format.sampleRate()), m_volume(volume)
    {
        open(QIODeviceBase::ReadOnly);
    }
 
    qint64 readData(char *data, qint64 len) override
    {
        unsigned char *ptr = reinterpret_cast<unsigned char *>(data);
        const unsigned char *const end = ptr + len - (len % m_format.bytesPerFrame());
 
        while (ptr < end) {
            const qreal x = m_generator() * m_volume;
            for (int ch = 0; ch < m_format.channelCount(); ++ch)
                ptr = writeSineSample(ptr, m_format.sampleFormat(), x);
        }
 
        return ptr - reinterpret_cast<unsigned char *>(data);
    }
 
    qint64 writeData(const char *, qint64) override { return 0; }
    bool isSequential() const override { return true; }
    qint64 bytesAvailable() const override { return std::numeric_limits<qint64>::max(); }
 
private:
    QAudioFormat m_format;
    SineWaveGenerator m_generator;
    qreal m_volume;
};
 
class AudioGenerator : public QObject
{
    Q_OBJECT
public:
    AudioGenerator()
    {
        m_format.setSampleFormat(QAudioFormat::UInt8);
        m_format.setSampleRate(8000);
        m_format.setChannelConfig(QAudioFormat::ChannelConfigMono);
    }
 
    void setFormat(const QAudioFormat &format)
    { //
        m_format = format;
    }
 
    void setBufferCount(int count)
    { //
        m_maxBufferCount = std::max(count, 1);
    }
 
    void setDuration(std::chrono::microseconds duration)
    { //
        m_duration = duration;
    }
 
    void setFrequency(qreal frequency)
    { //
        m_frequency = frequency;
    }
 
    void emitEmptyBufferOnStop()
    { //
        m_emitEmptyBufferOnStop = true;
    }
 
    QAudioBuffer createAudioBuffer()
    {
        const std::chrono::microseconds bufferDuration = m_duration * (m_bufferIndex + 1) / m_maxBufferCount
                - m_duration * m_bufferIndex / m_maxBufferCount;
        QByteArray data = createSineWaveData(m_format, bufferDuration, m_sampleIndex, m_frequency);
        Q_ASSERT(m_format.bytesPerSample());
        m_sampleIndex += data.size() / m_format.bytesPerSample();
        return QAudioBuffer(data, m_format);
    }
 
signals:
    void done();
    void audioBufferCreated(const QAudioBuffer &buffer);
 
public slots:
    void nextBuffer()
    {
        if (m_bufferIndex == m_maxBufferCount) {
            emit done();
            if (m_emitEmptyBufferOnStop)
                emit audioBufferCreated({});
            return;
        }
 
        const QAudioBuffer buffer = createAudioBuffer();
 
        emit audioBufferCreated(buffer);
        ++m_bufferIndex;
    }
 
private:
    int m_maxBufferCount = 1;
    std::chrono::microseconds m_duration{ std::chrono::seconds{ 1 } };
    int m_bufferIndex = 0;
    QAudioFormat m_format;
    bool m_emitEmptyBufferOnStop = false;
    qreal m_frequency = 500.;
    qint32 m_sampleIndex = 0;
};
 
QT_END_NAMESPACE
 
#endif // AUDIOGENERATIONUTILS_H