- Qt 5.5
- Qt Multimedia
- Audio Input Example
- audioinput.cpp Example File
- Qt 5.5.1 Reference Documentation

# audioinput.cpp Example File

audioinput/audioinput.cpp

    /****************************************************************************
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    **
    ** This file is part of the examples of the Qt Toolkit.
    **
    ** $QT_BEGIN_LICENSE:BSD$
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    #include <stdlib.h>
    #include <math.h>

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

    #include "audioinput.h"

    #define PUSH_MODE_LABEL "Enable push mode"
    #define PULL_MODE_LABEL "Enable pull mode"
    #define SUSPEND_LABEL   "Suspend recording"
    #define RESUME_LABEL    "Resume recording"

    const int BufferSize = 4096;

    AudioInfo::AudioInfo(const QAudioFormat &format, QObject *parent)
        :   QIODevice(parent)
        ,   m_format(format)
        ,   m_maxAmplitude(0)
        ,   m_level(0.0)

    {
        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;
        }
    }

    AudioInfo::~AudioInfo()
    {
    }

    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);

        m_level = 0;
        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()
        :   m_canvas(0)
        ,   m_modeButton(0)
        ,   m_suspendResumeButton(0)
        ,   m_deviceBox(0)
        ,   m_device(QAudioDeviceInfo::defaultInputDevice())
        ,   m_audioInfo(0)
        ,   m_audioInput(0)
        ,   m_input(0)
        ,   m_pullMode(false)
        ,   m_buffer(BufferSize, 0)
    {
        initializeWindow();
        initializeAudio();
    }

    InputTest::~InputTest() {}

    void InputTest::initializeWindow()
    {
        QScopedPointer<QWidget> window(new QWidget);
        QScopedPointer<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));
        foreach (const QAudioDeviceInfo &deviceInfo, QAudioDeviceInfo::availableDevices(QAudio::AudioInput)) {
            if (deviceInfo != defaultDeviceInfo)
                m_deviceBox->addItem(deviceInfo.deviceName(), qVariantFromValue(deviceInfo));
        }

        connect(m_deviceBox, SIGNAL(activated(int)), SLOT(deviceChanged(int)));
        layout->addWidget(m_deviceBox);

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

        m_modeButton = new QPushButton(this);
        m_modeButton->setText(tr(PUSH_MODE_LABEL));
        connect(m_modeButton, SIGNAL(clicked()), SLOT(toggleMode()));
        layout->addWidget(m_modeButton);

        m_suspendResumeButton = new QPushButton(this);
        m_suspendResumeButton->setText(tr(SUSPEND_LABEL));
        connect(m_suspendResumeButton, SIGNAL(clicked()), SLOT(toggleSuspend()));
        layout->addWidget(m_suspendResumeButton);

        window->setLayout(layout.data());
        layout.take(); // ownership transferred

        setCentralWidget(window.data());
        QWidget *const windowPtr = window.take(); // ownership transferred
        windowPtr->show();
    }

    void InputTest::initializeAudio()
    {
        m_pullMode = true;

        m_format.setSampleRate(8000);
        m_format.setChannelCount(1);
        m_format.setSampleSize(16);
        m_format.setSampleType(QAudioFormat::SignedInt);
        m_format.setByteOrder(QAudioFormat::LittleEndian);
        m_format.setCodec("audio/pcm");

        QAudioDeviceInfo info(QAudioDeviceInfo::defaultInputDevice());
        if (!info.isFormatSupported(m_format)) {
            qWarning() << "Default format not supported - trying to use nearest";
            m_format = info.nearestFormat(m_format);
        }

        m_audioInfo  = new AudioInfo(m_format, this);
        connect(m_audioInfo, SIGNAL(update()), SLOT(refreshDisplay()));

        createAudioInput();
    }

    void InputTest::createAudioInput()
    {
        m_audioInput = new QAudioInput(m_device, m_format, this);
        m_volumeSlider->setValue(m_audioInput->volume() * 100);
        m_audioInfo->start();
        m_audioInput->start(m_audioInfo);
    }

    void InputTest::readMore()
    {
        if (!m_audioInput)
            return;
        qint64 len = m_audioInput->bytesReady();
        if (len > BufferSize)
            len = BufferSize;
        qint64 l = m_input->read(m_buffer.data(), len);
        if (l > 0)
            m_audioInfo->write(m_buffer.constData(), l);
    }

    void InputTest::toggleMode()
    {
        // Change bewteen pull and push modes
        m_audioInput->stop();

        if (m_pullMode) {
            m_modeButton->setText(tr(PULL_MODE_LABEL));
            m_input = m_audioInput->start();
            connect(m_input, SIGNAL(readyRead()), SLOT(readMore()));
            m_pullMode = false;
        } else {
            m_modeButton->setText(tr(PUSH_MODE_LABEL));
            m_pullMode = true;
            m_audioInput->start(m_audioInfo);
        }

        m_suspendResumeButton->setText(tr(SUSPEND_LABEL));
    }

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

    void InputTest::refreshDisplay()
    {
        m_canvas->setLevel(m_audioInfo->level());
    }

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

        m_device = m_deviceBox->itemData(index).value<QAudioDeviceInfo>();
        createAudioInput();
    }

    void InputTest::sliderChanged(int value)
    {
        if (m_audioInput)
            m_audioInput->setVolume(qreal(value) / 100);
    }