audiooutput.cpp Example File

multimedia/audiooutput/audiooutput.cpp
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#include "audiooutput.h" #include <QAudioDeviceInfo> #include <QAudioOutput> #include <QDebug> #include <QVBoxLayout> #include <qmath.h> #include <qendian.h> Generator::Generator(const QAudioFormat &format , qint64 durationUs , int sampleRate) { if (format.isValid()) generateData(format, durationUs, sampleRate); } void Generator::start() { open(QIODevice::ReadOnly); } void Generator::stop() { m_pos = 0; close(); } void Generator::generateData(const QAudioFormat &format, qint64 durationUs, int sampleRate) { const int channelBytes = format.sampleSize() / 8; const int sampleBytes = format.channelCount() * channelBytes; qint64 length = (format.sampleRate() * format.channelCount() * (format.sampleSize() / 8)) * durationUs / 1000000; Q_ASSERT(length % sampleBytes == 0); Q_UNUSED(sampleBytes) // suppress warning in release builds m_buffer.resize(length); unsigned char *ptr = reinterpret_cast<unsigned char *>(m_buffer.data()); int sampleIndex = 0; while (length) { // Produces value (-1..1) const qreal x = qSin(2 * M_PI * sampleRate * qreal(sampleIndex++ % format.sampleRate()) / format.sampleRate()); for (int i=0; i<format.channelCount(); ++i) { if (format.sampleSize() == 8) { if (format.sampleType() == QAudioFormat::UnSignedInt) { const quint8 value = static_cast<quint8>((1.0 + x) / 2 * 255); *reinterpret_cast<quint8 *>(ptr) = value; } else if (format.sampleType() == QAudioFormat::SignedInt) { const qint8 value = static_cast<qint8>(x * 127); *reinterpret_cast<qint8 *>(ptr) = value; } } else if (format.sampleSize() == 16) { if (format.sampleType() == QAudioFormat::UnSignedInt) { quint16 value = static_cast<quint16>((1.0 + x) / 2 * 65535); if (format.byteOrder() == QAudioFormat::LittleEndian) qToLittleEndian<quint16>(value, ptr); else qToBigEndian<quint16>(value, ptr); } else if (format.sampleType() == QAudioFormat::SignedInt) { qint16 value = static_cast<qint16>(x * 32767); if (format.byteOrder() == QAudioFormat::LittleEndian) qToLittleEndian<qint16>(value, ptr); else qToBigEndian<qint16>(value, ptr); } } ptr += channelBytes; length -= channelBytes; } } } qint64 Generator::readData(char *data, qint64 len) { qint64 total = 0; if (!m_buffer.isEmpty()) { while (len - total > 0) { const qint64 chunk = qMin((m_buffer.size() - m_pos), len - total); memcpy(data + total, m_buffer.constData() + m_pos, chunk); m_pos = (m_pos + chunk) % m_buffer.size(); total += chunk; } } return total; } qint64 Generator::writeData(const char *data, qint64 len) { Q_UNUSED(data); Q_UNUSED(len); return 0; } qint64 Generator::bytesAvailable() const { return m_buffer.size() + QIODevice::bytesAvailable(); } AudioTest::AudioTest() : m_pushTimer(new QTimer(this)) { initializeWindow(); initializeAudio(QAudioDeviceInfo::defaultOutputDevice()); } AudioTest::~AudioTest() { m_pushTimer->stop(); } void AudioTest::initializeWindow() { QWidget *window = new QWidget; QVBoxLayout *layout = new QVBoxLayout; m_deviceBox = new QComboBox(this); const QAudioDeviceInfo &defaultDeviceInfo = QAudioDeviceInfo::defaultOutputDevice(); m_deviceBox->addItem(defaultDeviceInfo.deviceName(), qVariantFromValue(defaultDeviceInfo)); for (auto &deviceInfo: QAudioDeviceInfo::availableDevices(QAudio::AudioOutput)) { if (deviceInfo != defaultDeviceInfo) m_deviceBox->addItem(deviceInfo.deviceName(), qVariantFromValue(deviceInfo)); } connect(m_deviceBox, QOverload<int>::of(&QComboBox::activated), this, &AudioTest::deviceChanged); layout->addWidget(m_deviceBox); m_modeButton = new QPushButton(this); connect(m_modeButton, &QPushButton::clicked, this, &AudioTest::toggleMode); layout->addWidget(m_modeButton); m_suspendResumeButton = new QPushButton(this); connect(m_suspendResumeButton, &QPushButton::clicked, this, &AudioTest::toggleSuspendResume); layout->addWidget(m_suspendResumeButton); QHBoxLayout *volumeBox = new QHBoxLayout; m_volumeLabel = new QLabel; m_volumeLabel->setText(tr("Volume:")); m_volumeSlider = new QSlider(Qt::Horizontal); m_volumeSlider->setMinimum(0); m_volumeSlider->setMaximum(100); m_volumeSlider->setSingleStep(10); connect(m_volumeSlider, &QSlider::valueChanged, this, &AudioTest::volumeChanged); volumeBox->addWidget(m_volumeLabel); volumeBox->addWidget(m_volumeSlider); layout->addLayout(volumeBox); window->setLayout(layout); setCentralWidget(window); window->show(); } void AudioTest::initializeAudio(const QAudioDeviceInfo &deviceInfo) { QAudioFormat format; format.setSampleRate(44100); format.setChannelCount(1); format.setSampleSize(16); format.setCodec("audio/pcm"); format.setByteOrder(QAudioFormat::LittleEndian); format.setSampleType(QAudioFormat::SignedInt); if (!deviceInfo.isFormatSupported(format)) { qWarning() << "Default format not supported - trying to use nearest"; format = deviceInfo.nearestFormat(format); } const int durationSeconds = 1; const int toneSampleRateHz = 600; m_generator.reset(new Generator(format, durationSeconds * 1000000, toneSampleRateHz)); m_audioOutput.reset(new QAudioOutput(deviceInfo, format)); m_generator->start(); qreal initialVolume = QAudio::convertVolume(m_audioOutput->volume(), QAudio::LinearVolumeScale, QAudio::LogarithmicVolumeScale); m_volumeSlider->setValue(qRound(initialVolume * 100)); toggleMode(); } void AudioTest::deviceChanged(int index) { m_generator->stop(); m_audioOutput->stop(); m_audioOutput->disconnect(this); initializeAudio(m_deviceBox->itemData(index).value<QAudioDeviceInfo>()); } void AudioTest::volumeChanged(int value) { qreal linearVolume = QAudio::convertVolume(value / qreal(100), QAudio::LogarithmicVolumeScale, QAudio::LinearVolumeScale); m_audioOutput->setVolume(linearVolume); } void AudioTest::toggleMode() { m_pushTimer->stop(); m_audioOutput->stop(); toggleSuspendResume(); if (m_pullMode) { //switch to pull mode (QAudioOutput pulls from Generator as needed) m_modeButton->setText(tr("Enable push mode")); m_audioOutput->start(m_generator.data()); } else { //switch to push mode (periodically push to QAudioOutput using a timer) m_modeButton->setText(tr("Enable pull mode")); auto io = m_audioOutput->start(); m_pushTimer->disconnect(); connect(m_pushTimer, &QTimer::timeout, [this, io]() { if (m_audioOutput->state() == QAudio::StoppedState) return; QByteArray buffer(32768, 0); int chunks = m_audioOutput->bytesFree() / m_audioOutput->periodSize(); while (chunks) { const qint64 len = m_generator->read(buffer.data(), m_audioOutput->periodSize()); if (len) io->write(buffer.data(), len); if (len != m_audioOutput->periodSize()) break; --chunks; } }); m_pushTimer->start(20); } m_pullMode = !m_pullMode; } void AudioTest::toggleSuspendResume() { if (m_audioOutput->state() == QAudio::SuspendedState || m_audioOutput->state() == QAudio::StoppedState) { m_audioOutput->resume(); m_suspendResumeButton->setText(tr("Suspend recording")); } else if (m_audioOutput->state() == QAudio::ActiveState) { m_audioOutput->suspend(); m_suspendResumeButton->setText(tr("Resume playback")); } else if (m_audioOutput->state() == QAudio::IdleState) { // no-op } }

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