Audio Input Example

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#include "audioinput.h"

#include <stdlib.h>
#include <math.h>

#include <QDateTime>
#include <QDebug>
#include <QPainter>
#include <QVBoxLayout>
#include <QAudioDeviceInfo>
#include <QAudioInput>
#include <qendian.h>

AudioInfo::AudioInfo(const QAudioFormat &format)
    : m_format(format)
{
    switch (m_format.sampleSize()) {
    case 8:
        switch (m_format.sampleType()) {
        case QAudioFormat::UnSignedInt:
            m_maxAmplitude = 255;
            break;
        case QAudioFormat::SignedInt:
            m_maxAmplitude = 127;
            break;
        default:
            break;
        }
        break;
    case 16:
        switch (m_format.sampleType()) {
        case QAudioFormat::UnSignedInt:
            m_maxAmplitude = 65535;
            break;
        case QAudioFormat::SignedInt:
            m_maxAmplitude = 32767;
            break;
        default:
            break;
        }
        break;

    case 32:
        switch (m_format.sampleType()) {
        case QAudioFormat::UnSignedInt:
            m_maxAmplitude = 0xffffffff;
            break;
        case QAudioFormat::SignedInt:
            m_maxAmplitude = 0x7fffffff;
            break;
        case QAudioFormat::Float:
            m_maxAmplitude = 0x7fffffff; // Kind of
        default:
            break;
        }
        break;

    default:
        break;
    }
}

void AudioInfo::start()
{
    open(QIODevice::WriteOnly);
}

void AudioInfo::stop()
{
    close();
}

qint64 AudioInfo::readData(char *data, qint64 maxlen)
{
    Q_UNUSED(data)
    Q_UNUSED(maxlen)

    return 0;
}

qint64 AudioInfo::writeData(const char *data, qint64 len)
{
    if (m_maxAmplitude) {
        Q_ASSERT(m_format.sampleSize() % 8 == 0);
        const int channelBytes = m_format.sampleSize() / 8;
        const int sampleBytes = m_format.channelCount() * channelBytes;
        Q_ASSERT(len % sampleBytes == 0);
        const int numSamples = len / sampleBytes;

        quint32 maxValue = 0;
        const unsigned char *ptr = reinterpret_cast<const unsigned char *>(data);

        for (int i = 0; i < numSamples; ++i) {
            for (int j = 0; j < m_format.channelCount(); ++j) {
                quint32 value = 0;

                if (m_format.sampleSize() == 8 && m_format.sampleType() == QAudioFormat::UnSignedInt) {
                    value = *reinterpret_cast<const quint8*>(ptr);
                } else if (m_format.sampleSize() == 8 && m_format.sampleType() == QAudioFormat::SignedInt) {
                    value = qAbs(*reinterpret_cast<const qint8*>(ptr));
                } else if (m_format.sampleSize() == 16 && m_format.sampleType() == QAudioFormat::UnSignedInt) {
                    if (m_format.byteOrder() == QAudioFormat::LittleEndian)
                        value = qFromLittleEndian<quint16>(ptr);
                    else
                        value = qFromBigEndian<quint16>(ptr);
                } else if (m_format.sampleSize() == 16 && m_format.sampleType() == QAudioFormat::SignedInt) {
                    if (m_format.byteOrder() == QAudioFormat::LittleEndian)
                        value = qAbs(qFromLittleEndian<qint16>(ptr));
                    else
                        value = qAbs(qFromBigEndian<qint16>(ptr));
                } else if (m_format.sampleSize() == 32 && m_format.sampleType() == QAudioFormat::UnSignedInt) {
                    if (m_format.byteOrder() == QAudioFormat::LittleEndian)
                        value = qFromLittleEndian<quint32>(ptr);
                    else
                        value = qFromBigEndian<quint32>(ptr);
                } else if (m_format.sampleSize() == 32 && m_format.sampleType() == QAudioFormat::SignedInt) {
                    if (m_format.byteOrder() == QAudioFormat::LittleEndian)
                        value = qAbs(qFromLittleEndian<qint32>(ptr));
                    else
                        value = qAbs(qFromBigEndian<qint32>(ptr));
                } else if (m_format.sampleSize() == 32 && m_format.sampleType() == QAudioFormat::Float) {
                    value = qAbs(*reinterpret_cast<const float*>(ptr) * 0x7fffffff); // assumes 0-1.0
                }

                maxValue = qMax(value, maxValue);
                ptr += channelBytes;
            }
        }

        maxValue = qMin(maxValue, m_maxAmplitude);
        m_level = qreal(maxValue) / m_maxAmplitude;
    }

    emit update();
    return len;
}

RenderArea::RenderArea(QWidget *parent)
    : QWidget(parent)
{
    setBackgroundRole(QPalette::Base);
    setAutoFillBackground(true);

    setMinimumHeight(30);
    setMinimumWidth(200);
}

void RenderArea::paintEvent(QPaintEvent * /* event */)
{
    QPainter painter(this);

    painter.setPen(Qt::black);
    painter.drawRect(QRect(painter.viewport().left()+10,
                           painter.viewport().top()+10,
                           painter.viewport().right()-20,
                           painter.viewport().bottom()-20));
    if (m_level == 0.0)
        return;

    int pos = ((painter.viewport().right()-20)-(painter.viewport().left()+11))*m_level;
    painter.fillRect(painter.viewport().left()+11,
                     painter.viewport().top()+10,
                     pos,
                     painter.viewport().height()-21,
                     Qt::red);
}

void RenderArea::setLevel(qreal value)
{
    m_level = value;
    update();
}

InputTest::InputTest()
{
    initializeWindow();
    initializeAudio(QAudioDeviceInfo::defaultInputDevice());
}

void InputTest::initializeWindow()
{
    QWidget *window = new QWidget;
    QVBoxLayout *layout = new QVBoxLayout;

    m_canvas = new RenderArea(this);
    layout->addWidget(m_canvas);

    m_deviceBox = new QComboBox(this);
    const QAudioDeviceInfo &defaultDeviceInfo = QAudioDeviceInfo::defaultInputDevice();
    m_deviceBox->addItem(defaultDeviceInfo.deviceName(), qVariantFromValue(defaultDeviceInfo));
    for (auto &deviceInfo: QAudioDeviceInfo::availableDevices(QAudio::AudioInput)) {
        if (deviceInfo != defaultDeviceInfo)
            m_deviceBox->addItem(deviceInfo.deviceName(), qVariantFromValue(deviceInfo));
    }

    connect(m_deviceBox, QOverload<int>::of(&QComboBox::activated), this, &InputTest::deviceChanged);
    layout->addWidget(m_deviceBox);

    m_volumeSlider = new QSlider(Qt::Horizontal, this);
    m_volumeSlider->setRange(0, 100);
    m_volumeSlider->setValue(100);
    connect(m_volumeSlider, &QSlider::valueChanged, this, &InputTest::sliderChanged);
    layout->addWidget(m_volumeSlider);

    m_modeButton = new QPushButton(this);
    connect(m_modeButton, &QPushButton::clicked, this, &InputTest::toggleMode);
    layout->addWidget(m_modeButton);

    m_suspendResumeButton = new QPushButton(this);
    connect(m_suspendResumeButton, &QPushButton::clicked, this, &InputTest::toggleSuspend);
    layout->addWidget(m_suspendResumeButton);

    window->setLayout(layout);

    setCentralWidget(window);
    window->show();
}

void InputTest::initializeAudio(const QAudioDeviceInfo &deviceInfo)
{
    QAudioFormat format;
    format.setSampleRate(8000);
    format.setChannelCount(1);
    format.setSampleSize(16);
    format.setSampleType(QAudioFormat::SignedInt);
    format.setByteOrder(QAudioFormat::LittleEndian);
    format.setCodec("audio/pcm");

    if (!deviceInfo.isFormatSupported(format)) {
        qWarning() << "Default format not supported - trying to use nearest";
        format = deviceInfo.nearestFormat(format);
    }

    m_audioInfo.reset(new AudioInfo(format));
    connect(m_audioInfo.data(), &AudioInfo::update, [this]() {
        m_canvas->setLevel(m_audioInfo->level());
    });

    m_audioInput.reset(new QAudioInput(deviceInfo, format));
    qreal initialVolume = QAudio::convertVolume(m_audioInput->volume(),
                                                QAudio::LinearVolumeScale,
                                                QAudio::LogarithmicVolumeScale);
    m_volumeSlider->setValue(qRound(initialVolume * 100));
    m_audioInfo->start();
    toggleMode();
}

void InputTest::toggleMode()
{
    m_audioInput->stop();
    toggleSuspend();

    // Change bewteen pull and push modes
    if (m_pullMode) {
        m_modeButton->setText(tr("Enable push mode"));
        m_audioInput->start(m_audioInfo.data());
    } else {
        m_modeButton->setText(tr("Enable pull mode"));
        auto io = m_audioInput->start();
        connect(io, &QIODevice::readyRead,
            [&, io]() {
                qint64 len = m_audioInput->bytesReady();
                const int BufferSize = 4096;
                if (len > BufferSize)
                    len = BufferSize;

                QByteArray buffer(len, 0);
                qint64 l = io->read(buffer.data(), len);
                if (l > 0)
                    m_audioInfo->write(buffer.constData(), l);
            });
    }

    m_pullMode = !m_pullMode;
}

void InputTest::toggleSuspend()
{
    // toggle suspend/resume
    if (m_audioInput->state() == QAudio::SuspendedState || m_audioInput->state() == QAudio::StoppedState) {
        m_audioInput->resume();
        m_suspendResumeButton->setText(tr("Suspend recording"));
    } else if (m_audioInput->state() == QAudio::ActiveState) {
        m_audioInput->suspend();
        m_suspendResumeButton->setText(tr("Resume recording"));
    } else if (m_audioInput->state() == QAudio::IdleState) {
        // no-op
    }
}

void InputTest::deviceChanged(int index)
{
    m_audioInfo->stop();
    m_audioInput->stop();
    m_audioInput->disconnect(this);

    initializeAudio(m_deviceBox->itemData(index).value<QAudioDeviceInfo>());
}

void InputTest::sliderChanged(int value)
{
    qreal linearVolume = QAudio::convertVolume(value / qreal(100),
                                               QAudio::LogarithmicVolumeScale,
                                               QAudio::LinearVolumeScale);

    m_audioInput->setVolume(linearVolume);
}