Qt Reference Documentation
Search index:

audiooutput.cpp Example File

multimedia/audiooutput/audiooutput.cpp 
 /****************************************************************************
 **
 ** Copyright (C) 2010 Nokia Corporation and/or its subsidiary(-ies).
 ** All rights reserved.
 ** Contact: Nokia Corporation ([email protected])
 **
 ** This file is part of the examples of the Qt Toolkit.
 **
 ** $QT_BEGIN_LICENSE:BSD$
 ** You may use this file under the terms of the BSD license as follows:
 **
 ** "Redistribution and use in source and binary forms, with or without
 ** modification, are permitted provided that the following conditions are
 ** met:
 **   * Redistributions of source code must retain the above copyright
 **     notice, this list of conditions and the following disclaimer.
 **   * Redistributions in binary form must reproduce the above copyright
 **     notice, this list of conditions and the following disclaimer in
 **     the documentation and/or other materials provided with the
 **     distribution.
 **   * Neither the name of Nokia Corporation and its Subsidiary(-ies) nor
 **     the names of its contributors may be used to endorse or promote
 **     products derived from this software without specific prior written
 **     permission.
 **
 ** THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 ** "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 ** LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
 ** A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
 ** OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 ** SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 ** LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 ** DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 ** THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 ** (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 ** OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE."
 ** $QT_END_LICENSE$
 **
 ****************************************************************************/

 #include <QDebug>
 #include <QVBoxLayout>

 #include <QAudioOutput>
 #include <QAudioDeviceInfo>
 #include <QtCore/qmath.h>
 #include <QtCore/qendian.h>
 #include "audiooutput.h"

 const QString AudioTest::PushModeLabel(tr("Enable push mode"));
 const QString AudioTest::PullModeLabel(tr("Enable pull mode"));
 const QString AudioTest::SuspendLabel(tr("Suspend playback"));
 const QString AudioTest::ResumeLabel(tr("Resume playback"));

 const int DurationSeconds = 1;
 const int ToneFrequencyHz = 600;
 const int DataFrequencyHz = 44100;
 const int BufferSize      = 32768;

 Generator::Generator(const QAudioFormat &format,
                      qint64 durationUs,
                      int frequency,
                      QObject *parent)
     :   QIODevice(parent)
     ,   m_pos(0)
 {
     generateData(format, durationUs, frequency);
 }

 Generator::~Generator()
 {

 }

 void Generator::start()
 {
     open(QIODevice::ReadOnly);
 }

 void Generator::stop()
 {
     m_pos = 0;
     close();
 }

 void Generator::generateData(const QAudioFormat &format, qint64 durationUs, int frequency)
 {
     const int channelBytes = format.sampleSize() / 8;
     const int sampleBytes = format.channels() * channelBytes;

     qint64 length = (format.frequency() * format.channels() * (format.sampleSize() / 8))
                         * durationUs / 100000;

     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) {
         const qreal x = qSin(2 * M_PI * frequency * qreal(sampleIndex % format.frequency()) / format.frequency());
         for (int i=0; i<format.channels(); ++i) {
             if (format.sampleSize() == 8 && format.sampleType() == QAudioFormat::UnSignedInt) {
                 const quint8 value = static_cast<quint8>((1.0 + x) / 2 * 255);
                 *reinterpret_cast<quint8*>(ptr) = value;
             } else if (format.sampleSize() == 8 && format.sampleType() == QAudioFormat::SignedInt) {
                 const qint8 value = static_cast<qint8>(x * 127);
                 *reinterpret_cast<quint8*>(ptr) = value;
             } else if (format.sampleSize() == 16 && 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.sampleSize() == 16 && 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;
         }
         ++sampleIndex;
     }
 }

 qint64 Generator::readData(char *data, qint64 len)
 {
     qint64 total = 0;
     while (len - total) {
         const qint64 chunk = qMin((m_buffer.size() - m_pos), len - total);
         memcpy(data, 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_pullTimer(new QTimer(this))
     ,   m_modeButton(0)
     ,   m_suspendResumeButton(0)
     ,   m_deviceBox(0)
     ,   m_device(QAudioDeviceInfo::defaultOutputDevice())
     ,   m_generator(0)
     ,   m_audioOutput(0)
     ,   m_output(0)
     ,   m_buffer(BufferSize, 0)
 {
     initializeWindow();
     initializeAudio();
 }

 void AudioTest::initializeWindow()
 {
     QScopedPointer<QWidget> window(new QWidget);
     QScopedPointer<QVBoxLayout> layout(new QVBoxLayout);

     m_deviceBox = new QComboBox(this);
     foreach (const QAudioDeviceInfo &deviceInfo, QAudioDeviceInfo::availableDevices(QAudio::AudioOutput))
         m_deviceBox->addItem(deviceInfo.deviceName(), qVariantFromValue(deviceInfo));
     connect(m_deviceBox,SIGNAL(activated(int)),SLOT(deviceChanged(int)));
     layout->addWidget(m_deviceBox);

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

     m_suspendResumeButton = new QPushButton(this);
     m_suspendResumeButton->setText(SuspendLabel);
     connect(m_suspendResumeButton, SIGNAL(clicked()), SLOT(toggleSuspendResume()));
     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 AudioTest::initializeAudio()
 {
     connect(m_pullTimer, SIGNAL(timeout()), SLOT(pullTimerExpired()));

     m_pullMode = true;

     m_format.setFrequency(DataFrequencyHz);
     m_format.setChannels(1);
     m_format.setSampleSize(16);
     m_format.setCodec("audio/pcm");
     m_format.setByteOrder(QAudioFormat::LittleEndian);
     m_format.setSampleType(QAudioFormat::SignedInt);

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

     m_generator = new Generator(m_format, DurationSeconds*1000000, ToneFrequencyHz, this);

     createAudioOutput();
 }

 void AudioTest::createAudioOutput()
 {
     delete m_audioOutput;
     m_audioOutput = 0;
     m_audioOutput = new QAudioOutput(m_device, m_format, this);
     connect(m_audioOutput, SIGNAL(notify()), SLOT(notified()));
     connect(m_audioOutput, SIGNAL(stateChanged(QAudio::State)), SLOT(stateChanged(QAudio::State)));
     m_generator->start();
     m_audioOutput->start(m_generator);
 }

 AudioTest::~AudioTest()
 {

 }

 void AudioTest::deviceChanged(int index)
 {
     m_pullTimer->stop();
     m_generator->stop();
     m_audioOutput->stop();
     m_audioOutput->disconnect(this);
     m_device = m_deviceBox->itemData(index).value<QAudioDeviceInfo>();
     createAudioOutput();
 }

 void AudioTest::notified()
 {
     qWarning() << "bytesFree = " << m_audioOutput->bytesFree()
                << ", " << "elapsedUSecs = " << m_audioOutput->elapsedUSecs()
                << ", " << "processedUSecs = " << m_audioOutput->processedUSecs();
 }

 void AudioTest::pullTimerExpired()
 {
     if (m_audioOutput && m_audioOutput->state() != QAudio::StoppedState) {
         int chunks = m_audioOutput->bytesFree()/m_audioOutput->periodSize();
         while (chunks) {
            const qint64 len = m_generator->read(m_buffer.data(), m_audioOutput->periodSize());
            if (len)
                m_output->write(m_buffer.data(), len);
            if (len != m_audioOutput->periodSize())
                break;
            --chunks;
         }
     }
 }

 void AudioTest::toggleMode()
 {
     m_pullTimer->stop();
     m_audioOutput->stop();

     if (m_pullMode) {
         m_modeButton->setText(PullModeLabel);
         m_output = m_audioOutput->start();
         m_pullMode = false;
         m_pullTimer->start(20);
     } else {
         m_modeButton->setText(PushModeLabel);
         m_pullMode = true;
         m_audioOutput->start(m_generator);
     }

     m_suspendResumeButton->setText(SuspendLabel);
 }

 void AudioTest::toggleSuspendResume()
 {
     if (m_audioOutput->state() == QAudio::SuspendedState) {
         qWarning() << "status: Suspended, resume()";
         m_audioOutput->resume();
         m_suspendResumeButton->setText(SuspendLabel);
     } else if (m_audioOutput->state() == QAudio::ActiveState) {
         qWarning() << "status: Active, suspend()";
         m_audioOutput->suspend();
         m_suspendResumeButton->setText(ResumeLabel);
     } else if (m_audioOutput->state() == QAudio::StoppedState) {
         qWarning() << "status: Stopped, resume()";
         m_audioOutput->resume();
         m_suspendResumeButton->setText(SuspendLabel);
     } else if (m_audioOutput->state() == QAudio::IdleState) {
         qWarning() << "status: IdleState";
     }
 }

 void AudioTest::stateChanged(QAudio::State state)
 {
     qWarning() << "state = " << state;
 }

© 2008-2010 Nokia Corporation and/or its subsidiaries. Nokia, Qt and their respective logos are trademarks of Nokia Corporation in Finland and/or other countries worldwide.

All other trademarks are property of their respective owners. Privacy Policy


Licensees holding valid Qt Commercial licenses may use this document in accordance with the Qt Commercial License Agreement provided with the Software or, alternatively, in accordance with the terms contained in a written agreement between you and Nokia.

Alternatively, this document may be used under the terms of the GNU Free Documentation License version 1.3 as published by the Free Software Foundation.

X

Thank you for giving your feedback.

Make sure it is related to this specific page. For more general bugs and requests, please use the Qt Bug Tracker.