Improve QAudioDeviceInfo::defaultDevice().

The previous implementation of QAudioDeviceInfo::defaultXDevice() would
always report the first available device as the "default" one, making
the order, in which devices were listed, a hidden requirement when
implementing audio plugins. To make it easier and more reliable to
retrieve the default device, all new plugins should implement the new
QAudioSystemPluginExtension interface as well as the QAudioSystemPlugin.

Devices will be chosen in the following order (first match wins):
default plugin -> default device
               -> first available device
plugins -> default device
        -> first available device

Task-number: QTBUG-51292
Change-Id: I8ace78858976fe7c60a2c4a117ef15c4e1bb177f
Reviewed-by: Yoann Lopes <yoann.lopes@qt.io>

32 files changed, 264 insertions, 161 deletions

diff --git a/src/multimedia/audio/audio.pri b/src/multimedia/audio/audio.pri
index 96cfb1ce4..4706fd23e 100644
--- a/src/multimedia/audio/audio.pri
+++ b/src/multimedia/audio/audio.pri
@@ -19,7 +19,8 @@ PRIVATE_HEADERS += \
            audio/qaudiodevicefactory_p.h \
            audio/qwavedecoder_p.h \
            audio/qsamplecache_p.h \
-           audio/qaudiohelpers_p.h
+           audio/qaudiohelpers_p.h \
+           audio/qaudiosystempluginext_p.h
 
 SOURCES += \
            audio/qaudio.cpp \
diff --git a/src/multimedia/audio/qaudiodevicefactory.cpp b/src/multimedia/audio/qaudiodevicefactory.cpp
index 83e1a6c0b..c3e4929b3 100644
--- a/src/multimedia/audio/qaudiodevicefactory.cpp
+++ b/src/multimedia/audio/qaudiodevicefactory.cpp
@@ -41,6 +41,7 @@
 
 #include "qaudiosystem.h"
 #include "qaudiosystemplugin.h"
+#include "qaudiosystempluginext_p.h"
 
 #include "qmediapluginloader_p.h"
 #include "qaudiodevicefactory_p.h"
@@ -139,41 +140,53 @@ QList<QAudioDeviceInfo> QAudioDeviceFactory::availableDevices(QAudio::Mode mode)
     return devices;
 }
 
-QAudioDeviceInfo QAudioDeviceFactory::defaultInputDevice()
+QAudioDeviceInfo QAudioDeviceFactory::defaultDevice(QAudio::Mode mode)
 {
 #if !defined (QT_NO_LIBRARY) && !defined(QT_NO_SETTINGS)
-    QAudioSystemFactoryInterface* plugin = qobject_cast<QAudioSystemFactoryInterface*>(audioLoader()->instance(defaultKey()));
-    if (plugin) {
-        QList<QByteArray> list = plugin->availableDevices(QAudio::AudioInput);
-        if (list.size() > 0)
-            return QAudioDeviceInfo(defaultKey(), list.at(0), QAudio::AudioInput);
-    }
+    QMediaPluginLoader* l = audioLoader();
 
-    // if no plugin is marked as default or if the default plugin doesn't have any input device,
-    // return the first input available from other plugins.
-    QList<QAudioDeviceInfo> inputDevices = availableDevices(QAudio::AudioInput);
-    if (!inputDevices.isEmpty())
-        return inputDevices.first();
-#endif
+    // Check if there is a default plugin.
+    QAudioSystemFactoryInterface *plugin = qobject_cast<QAudioSystemFactoryInterface *>(l->instance(defaultKey()));
+    if (plugin) {
+        // Check if the plugin has the extension interface.
+        QAudioSystemPluginExtension *pluginExt = qobject_cast<QAudioSystemPluginExtension *>(l->instance(defaultKey()));
+        // Ask for the default device.
+        if (pluginExt) {
+            const QByteArray &device = pluginExt->defaultDevice(mode);
+            if (!device.isEmpty())
+                return QAudioDeviceInfo(defaultKey(), device, mode);
+        }
 
-    return QAudioDeviceInfo();
-}
+        // If there were no default devices, e.g., if the plugin did not implement the extent-ion interface,
+        // then just pick the first device that's available.
+        const auto &devices = plugin->availableDevices(mode);
+        if (!devices.isEmpty())
+            return QAudioDeviceInfo(defaultKey(), devices.first(), mode);
+    }
 
-QAudioDeviceInfo QAudioDeviceFactory::defaultOutputDevice()
-{
-#if !defined (QT_NO_LIBRARY) && !defined(QT_NO_SETTINGS)
-    QAudioSystemFactoryInterface* plugin = qobject_cast<QAudioSystemFactoryInterface*>(audioLoader()->instance(defaultKey()));
-    if (plugin) {
-        QList<QByteArray> list = plugin->availableDevices(QAudio::AudioOutput);
-        if (list.size() > 0)
-            return QAudioDeviceInfo(defaultKey(), list.at(0), QAudio::AudioOutput);
+    // If no plugin is marked as default, check the other plugins.
+    // Note: We're going to prioritize plugins that report a default device.
+    const auto &keys = l->keys();
+    QAudioDeviceInfo fallbackDevice;
+    for (const auto &key : keys) {
+        if (key == defaultKey())
+            continue;
+        QAudioSystemFactoryInterface* plugin = qobject_cast<QAudioSystemFactoryInterface*>(l->instance(key));
+        if (plugin) {
+            // Check if the plugin has the extent-ion interface.
+            QAudioSystemPluginExtension *pluginExt = qobject_cast<QAudioSystemPluginExtension *>(l->instance(key));
+            if (pluginExt) {
+                const QByteArray &device = pluginExt->defaultDevice(mode);
+                if (!device.isEmpty())
+                    return QAudioDeviceInfo(key, device, mode);
+            } else if (fallbackDevice.isNull()) {
+                const auto &devices = plugin->availableDevices(mode);
+                if (!devices.isEmpty())
+                    fallbackDevice = QAudioDeviceInfo(key, devices.first(), mode);
+            }
+        }
     }
 
-    // if no plugin is marked as default or if the default plugin doesn't have any output device,
-    // return the first output available from other plugins.
-    QList<QAudioDeviceInfo> outputDevices = availableDevices(QAudio::AudioOutput);
-    if (!outputDevices.isEmpty())
-        return outputDevices.first();
 #endif
 
     return QAudioDeviceInfo();
@@ -196,12 +209,12 @@ QAbstractAudioDeviceInfo* QAudioDeviceFactory::audioDeviceInfo(const QString &re
 
 QAbstractAudioInput* QAudioDeviceFactory::createDefaultInputDevice(QAudioFormat const &format)
 {
-    return createInputDevice(defaultInputDevice(), format);
+    return createInputDevice(defaultDevice(QAudio::AudioInput), format);
 }
 
 QAbstractAudioOutput* QAudioDeviceFactory::createDefaultOutputDevice(QAudioFormat const &format)
 {
-    return createOutputDevice(defaultOutputDevice(), format);
+    return createOutputDevice(defaultDevice(QAudio::AudioOutput), format);
 }
 
 QAbstractAudioInput* QAudioDeviceFactory::createInputDevice(QAudioDeviceInfo const& deviceInfo, QAudioFormat const &format)
diff --git a/src/multimedia/audio/qaudiodevicefactory_p.h b/src/multimedia/audio/qaudiodevicefactory_p.h
index 833184075..7ad5e4e78 100644
--- a/src/multimedia/audio/qaudiodevicefactory_p.h
+++ b/src/multimedia/audio/qaudiodevicefactory_p.h
@@ -71,8 +71,7 @@ class QAudioDeviceFactory
 public:
     static QList<QAudioDeviceInfo> availableDevices(QAudio::Mode mode);
 
-    static QAudioDeviceInfo defaultInputDevice();
-    static QAudioDeviceInfo defaultOutputDevice();
+    static QAudioDeviceInfo defaultDevice(QAudio::Mode mode);
 
     static QAbstractAudioDeviceInfo* audioDeviceInfo(const QString &realm, const QByteArray &handle, QAudio::Mode mode);
 
diff --git a/src/multimedia/audio/qaudiodeviceinfo.cpp b/src/multimedia/audio/qaudiodeviceinfo.cpp
index 945b415e8..f4f548017 100644
--- a/src/multimedia/audio/qaudiodeviceinfo.cpp
+++ b/src/multimedia/audio/qaudiodeviceinfo.cpp
@@ -419,7 +419,7 @@ QList<QAudioFormat::SampleType> QAudioDeviceInfo::supportedSampleTypes() const
 */
 QAudioDeviceInfo QAudioDeviceInfo::defaultInputDevice()
 {
-    return QAudioDeviceFactory::defaultInputDevice();
+    return QAudioDeviceFactory::defaultDevice(QAudio::AudioInput);
 }
 
 /*!
@@ -428,7 +428,7 @@ QAudioDeviceInfo QAudioDeviceInfo::defaultInputDevice()
 */
 QAudioDeviceInfo QAudioDeviceInfo::defaultOutputDevice()
 {
-    return QAudioDeviceFactory::defaultOutputDevice();
+    return QAudioDeviceFactory::defaultDevice(QAudio::AudioOutput);
 }
 
 /*!
diff --git a/src/multimedia/audio/qaudiosystemplugin.cpp b/src/multimedia/audio/qaudiosystemplugin.cpp
index b4fc0dbca..018392939 100644
--- a/src/multimedia/audio/qaudiosystemplugin.cpp
+++ b/src/multimedia/audio/qaudiosystemplugin.cpp
@@ -39,6 +39,7 @@
 
 
 #include "qaudiosystemplugin.h"
+#include "qaudiosystempluginext_p.h"
 
 QT_BEGIN_NAMESPACE
 
@@ -46,6 +47,10 @@ QAudioSystemFactoryInterface::~QAudioSystemFactoryInterface()
 {
 }
 
+QAudioSystemPluginExtension::~QAudioSystemPluginExtension()
+{
+}
+
 /*!
     \class QAudioSystemPlugin
     \brief The QAudioSystemPlugin class provides an abstract base for audio plugins.
diff --git a/src/multimedia/audio/qaudiosystempluginext_p.h b/src/multimedia/audio/qaudiosystempluginext_p.h
new file mode 100644
index 000000000..380bc5afa
--- /dev/null
+++ b/src/multimedia/audio/qaudiosystempluginext_p.h
@@ -0,0 +1,71 @@
+/****************************************************************************
+**
+** Copyright (C) 2016 The Qt Company Ltd.
+** Contact: https://www.qt.io/licensing/
+**
+** This file is part of the Qt Toolkit.
+**
+** $QT_BEGIN_LICENSE:LGPL$
+** Commercial License Usage
+** Licensees holding valid commercial Qt licenses may use this file in
+** accordance with the commercial license agreement provided with the
+** Software or, alternatively, in accordance with the terms contained in
+** a written agreement between you and The Qt Company. For licensing terms
+** and conditions see https://www.qt.io/terms-conditions. For further
+** information use the contact form at https://www.qt.io/contact-us.
+**
+** GNU Lesser General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU Lesser
+** General Public License version 3 as published by the Free Software
+** Foundation and appearing in the file LICENSE.LGPL3 included in the
+** packaging of this file. Please review the following information to
+** ensure the GNU Lesser General Public License version 3 requirements
+** will be met: https://www.gnu.org/licenses/lgpl-3.0.html.
+**
+** GNU General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU
+** General Public License version 2.0 or (at your option) the GNU General
+** Public license version 3 or any later version approved by the KDE Free
+** Qt Foundation. The licenses are as published by the Free Software
+** Foundation and appearing in the file LICENSE.GPL2 and LICENSE.GPL3
+** included in the packaging of this file. Please review the following
+** information to ensure the GNU General Public License requirements will
+** be met: https://www.gnu.org/licenses/gpl-2.0.html and
+** https://www.gnu.org/licenses/gpl-3.0.html.
+**
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+#ifndef QAUDIOSYSTEMPLUGINEXT_P_H
+#define QAUDIOSYSTEMPLUGINEXT_P_H
+
+#include <QtMultimedia/qtmultimediadefs.h>
+#include <QtMultimedia/qaudio.h>
+#include <QtCore/qplugin.h>
+
+QT_BEGIN_NAMESPACE
+
+//
+//  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.
+//
+
+struct Q_MULTIMEDIA_EXPORT QAudioSystemPluginExtension
+{
+    virtual QByteArray defaultDevice(QAudio::Mode) const = 0;
+    virtual ~QAudioSystemPluginExtension();
+};
+
+#define QAudioSystemPluginExtension_iid "org.qt-project.qt.audiosystempluginextension"
+Q_DECLARE_INTERFACE(QAudioSystemPluginExtension, QAudioSystemPluginExtension_iid)
+
+QT_END_NAMESPACE
+
+#endif // QAUDIOSYSTEMPLUGINEXT_P_H
diff --git a/src/plugins/alsa/qalsaaudiodeviceinfo.cpp b/src/plugins/alsa/qalsaaudiodeviceinfo.cpp
index 0342ca546..d0f772d5e 100644
--- a/src/plugins/alsa/qalsaaudiodeviceinfo.cpp
+++ b/src/plugins/alsa/qalsaaudiodeviceinfo.cpp
@@ -140,6 +140,15 @@ QList<QAudioFormat::SampleType> QAlsaAudioDeviceInfo::supportedSampleTypes()
     return typez;
 }
 
+QByteArray QAlsaAudioDeviceInfo::defaultDevice(QAudio::Mode mode)
+{
+    const auto &devices = availableDevices(mode);
+    if (devices.size() == 0)
+        return QByteArray();
+
+    return devices.first();
+}
+
 bool QAlsaAudioDeviceInfo::open()
 {
     int err = 0;
@@ -396,24 +405,6 @@ QList<QByteArray> QAlsaAudioDeviceInfo::availableDevices(QAudio::Mode mode)
     return devices;
 }
 
-QByteArray QAlsaAudioDeviceInfo::defaultInputDevice()
-{
-    QList<QByteArray> devices = availableDevices(QAudio::AudioInput);
-    if(devices.size() == 0)
-        return QByteArray();
-
-    return devices.first();
-}
-
-QByteArray QAlsaAudioDeviceInfo::defaultOutputDevice()
-{
-    QList<QByteArray> devices = availableDevices(QAudio::AudioOutput);
-    if(devices.size() == 0)
-        return QByteArray();
-
-    return devices.first();
-}
-
 void QAlsaAudioDeviceInfo::checkSurround()
 {
     surround40 = false;
diff --git a/src/plugins/alsa/qalsaaudiodeviceinfo.h b/src/plugins/alsa/qalsaaudiodeviceinfo.h
index 0147a2cf9..3b14bd489 100644
--- a/src/plugins/alsa/qalsaaudiodeviceinfo.h
+++ b/src/plugins/alsa/qalsaaudiodeviceinfo.h
@@ -88,8 +88,7 @@ public:
     QList<int> supportedSampleSizes();
     QList<QAudioFormat::Endian> supportedByteOrders();
     QList<QAudioFormat::SampleType> supportedSampleTypes();
-    static QByteArray defaultInputDevice();
-    static QByteArray defaultOutputDevice();
+    static QByteArray defaultDevice(QAudio::Mode mode);
     static QList<QByteArray> availableDevices(QAudio::Mode);
 
 private:
diff --git a/src/plugins/alsa/qalsaplugin.cpp b/src/plugins/alsa/qalsaplugin.cpp
index 79adbae59..e52e9ee83 100644
--- a/src/plugins/alsa/qalsaplugin.cpp
+++ b/src/plugins/alsa/qalsaplugin.cpp
@@ -49,6 +49,11 @@ QAlsaPlugin::QAlsaPlugin(QObject *parent)
 {
 }
 
+QByteArray QAlsaPlugin::defaultDevice(QAudio::Mode mode) const
+{
+    return QAlsaAudioDeviceInfo::defaultDevice(mode);
+}
+
 QList<QByteArray> QAlsaPlugin::availableDevices(QAudio::Mode mode) const
 {
     return QAlsaAudioDeviceInfo::availableDevices(mode);
diff --git a/src/plugins/alsa/qalsaplugin.h b/src/plugins/alsa/qalsaplugin.h
index 74e3475b7..b3c530f88 100644
--- a/src/plugins/alsa/qalsaplugin.h
+++ b/src/plugins/alsa/qalsaplugin.h
@@ -41,19 +41,22 @@
 #define QALSAPLUGIN_H
 
 #include <QtMultimedia/qaudiosystemplugin.h>
+#include <QtMultimedia/private/qaudiosystempluginext_p.h>
 
 QT_BEGIN_NAMESPACE
 
-class QAlsaPlugin : public QAudioSystemPlugin
+class QAlsaPlugin : public QAudioSystemPlugin, public QAudioSystemPluginExtension
 {
     Q_OBJECT
 
     Q_PLUGIN_METADATA(IID "org.qt-project.qt.audiosystemfactory/5.0" FILE "alsa.json")
+    Q_INTERFACES(QAudioSystemPluginExtension)
 
 public:
     QAlsaPlugin(QObject *parent = 0);
     ~QAlsaPlugin() {}
 
+    QByteArray defaultDevice(QAudio::Mode mode) const Q_DECL_OVERRIDE;
     QList<QByteArray> availableDevices(QAudio::Mode mode) const Q_DECL_OVERRIDE;
     QAbstractAudioInput *createInput(const QByteArray &device) Q_DECL_OVERRIDE;
     QAbstractAudioOutput *createOutput(const QByteArray &device) Q_DECL_OVERRIDE;
diff --git a/src/plugins/coreaudio/coreaudiodeviceinfo.h b/src/plugins/coreaudio/coreaudiodeviceinfo.h
index fc8999850..08c3961e6 100644
--- a/src/plugins/coreaudio/coreaudiodeviceinfo.h
+++ b/src/plugins/coreaudio/coreaudiodeviceinfo.h
@@ -65,9 +65,7 @@ public:
     QList<QAudioFormat::Endian> supportedByteOrders();
     QList<QAudioFormat::SampleType> supportedSampleTypes();
 
-    static QByteArray defaultInputDevice();
-    static QByteArray defaultOutputDevice();
-
+    static QByteArray defaultDevice(QAudio::Mode mode);
     static QList<QByteArray> availableDevices(QAudio::Mode mode);
 
 private:
diff --git a/src/plugins/coreaudio/coreaudiodeviceinfo.mm b/src/plugins/coreaudio/coreaudiodeviceinfo.mm
index 66e8ed4d7..1a79438cb 100644
--- a/src/plugins/coreaudio/coreaudiodeviceinfo.mm
+++ b/src/plugins/coreaudio/coreaudiodeviceinfo.mm
@@ -280,47 +280,29 @@ static QByteArray get_device_info(AudioDeviceID audioDevice, QAudio::Mode mode)
 }
 #endif
 
-QByteArray CoreAudioDeviceInfo::defaultInputDevice()
+QByteArray CoreAudioDeviceInfo::defaultDevice(QAudio::Mode mode)
 {
 #if defined(Q_OS_OSX)
     AudioDeviceID audioDevice;
     UInt32 size = sizeof(audioDevice);
-    AudioObjectPropertyAddress defaultInputDevicePropertyAddress = { kAudioHardwarePropertyDefaultInputDevice,
-                                                                     kAudioObjectPropertyScopeGlobal,
-                                                                     kAudioObjectPropertyElementMaster };
-
-    if (AudioObjectGetPropertyData(kAudioObjectSystemObject,
-                                   &defaultInputDevicePropertyAddress,
-                                   0, NULL, &size, &audioDevice) != noErr) {
-        qWarning() << "QAudioDeviceInfo: Unable to find default input device";
-        return QByteArray();
-    }
-
-    return get_device_info(audioDevice, QAudio::AudioInput);
-#else //iOS
-    return CoreAudioSessionManager::instance().inputDevices().first();
-#endif
-}
-
-QByteArray CoreAudioDeviceInfo::defaultOutputDevice()
-{
-#if defined(Q_OS_OSX)
-    AudioDeviceID audioDevice;
-    UInt32        size = sizeof(audioDevice);
-    AudioObjectPropertyAddress defaultOutputDevicePropertyAddress = { kAudioHardwarePropertyDefaultOutputDevice,
-                                                                     kAudioObjectPropertyScopeGlobal,
-                                                                     kAudioObjectPropertyElementMaster };
+    const AudioObjectPropertySelector selector = (mode == QAudio::AudioOutput) ? kAudioHardwarePropertyDefaultOutputDevice
+                                                                               : kAudioHardwarePropertyDefaultInputDevice;
+    AudioObjectPropertyAddress defaultDevicePropertyAddress = { selector,
+                                                                kAudioObjectPropertyScopeGlobal,
+                                                                kAudioObjectPropertyElementMaster };
 
     if (AudioObjectGetPropertyData(kAudioObjectSystemObject,
-                                   &defaultOutputDevicePropertyAddress,
+                                   &defaultDevicePropertyAddress,
                                    0, NULL, &size, &audioDevice) != noErr) {
-        qWarning() << "QAudioDeviceInfo: Unable to find default output device";
+        qWarning("QAudioDeviceInfo: Unable to find default %s device",  (mode == QAudio::AudioOutput) ? "output" : "input");
         return QByteArray();
     }
 
-    return get_device_info(audioDevice, QAudio::AudioOutput);
+    return get_device_info(audioDevice, mode);
 #else //iOS
-    return CoreAudioSessionManager::instance().outputDevices().first();
+    const auto &devices = (mode == QAudio::AudioOutput) ? CoreAudioSessionManager::instance().outputDevices()
+                                                        : CoreAudioSessionManager::instance().inputDevices();
+    return !devices.isEmpty() ? devices.first() : QByteArray();
 #endif
 }
 
@@ -343,15 +325,10 @@ QList<QByteArray> CoreAudioDeviceInfo::availableDevices(QAudio::Mode mode)
             AudioDeviceID*  audioDevices = new AudioDeviceID[dc];
 
             if (AudioObjectGetPropertyData(kAudioObjectSystemObject, &audioDevicesPropertyAddress, 0, NULL, &propSize, audioDevices) == noErr) {
-                QByteArray defaultDevice = (mode == QAudio::AudioOutput) ? defaultOutputDevice() : defaultInputDevice();
                 for (int i = 0; i < dc; ++i) {
-                    QByteArray info = get_device_info(audioDevices[i], mode);
-                    if (!info.isNull()) {
-                        if (info == defaultDevice)
-                            devices.prepend(info);
-                        else
-                            devices << info;
-                    }
+                    const QByteArray &info = get_device_info(audioDevices[i], mode);
+                    if (!info.isNull())
+                        devices << info;
                 }
             }
 
diff --git a/src/plugins/coreaudio/coreaudioplugin.h b/src/plugins/coreaudio/coreaudioplugin.h
index 5868508d2..da18d8cfe 100644
--- a/src/plugins/coreaudio/coreaudioplugin.h
+++ b/src/plugins/coreaudio/coreaudioplugin.h
@@ -39,19 +39,22 @@
 #ifndef IOSAUDIOPLUGIN_H
 #define IOSAUDIOPLUGIN_H
 
-#include <qaudiosystemplugin.h>
+#include <QtMultimedia/qaudiosystemplugin.h>
+#include <QtMultimedia/private/qaudiosystempluginext_p.h>
 
 QT_BEGIN_NAMESPACE
 
-class CoreAudioPlugin : public QAudioSystemPlugin
+class CoreAudioPlugin : public QAudioSystemPlugin, public QAudioSystemPluginExtension
 {
     Q_OBJECT
     Q_PLUGIN_METADATA(IID "org.qt-project.qt.audiosystemfactory/5.0" FILE "coreaudio.json")
+    Q_INTERFACES(QAudioSystemPluginExtension)
 
 public:
     explicit CoreAudioPlugin(QObject *parent = 0);
     ~CoreAudioPlugin() {}
 
+    QByteArray defaultDevice(QAudio::Mode mode) const Q_DECL_OVERRIDE;
     QList<QByteArray> availableDevices(QAudio::Mode mode) const Q_DECL_OVERRIDE;
     QAbstractAudioInput *createInput(const QByteArray &device) Q_DECL_OVERRIDE;
     QAbstractAudioOutput *createOutput(const QByteArray &device) Q_DECL_OVERRIDE;
diff --git a/src/plugins/coreaudio/coreaudioplugin.mm b/src/plugins/coreaudio/coreaudioplugin.mm
index 6d899fb67..ac51b9cd0 100644
--- a/src/plugins/coreaudio/coreaudioplugin.mm
+++ b/src/plugins/coreaudio/coreaudioplugin.mm
@@ -49,6 +49,10 @@ CoreAudioPlugin::CoreAudioPlugin(QObject *parent)
 {
 }
 
+QByteArray CoreAudioPlugin::defaultDevice(QAudio::Mode mode) const
+{
+    return CoreAudioDeviceInfo::defaultDevice(mode);
+}
 
 QList<QByteArray> CoreAudioPlugin::availableDevices(QAudio::Mode mode) const
 {
diff --git a/src/plugins/opensles/qopenslesengine.cpp b/src/plugins/opensles/qopenslesengine.cpp
index 0cbd10887..1a16cc2a3 100644
--- a/src/plugins/opensles/qopenslesengine.cpp
+++ b/src/plugins/opensles/qopenslesengine.cpp
@@ -101,6 +101,12 @@ SLDataFormat_PCM QOpenSLESEngine::audioFormatToSLFormatPCM(const QAudioFormat &f
 
 }
 
+QByteArray QOpenSLESEngine::defaultDevice(QAudio::Mode mode) const
+{
+    const auto &devices = availableDevices(mode);
+    return !devices.isEmpty() ? devices.first() : QByteArray();
+}
+
 QList<QByteArray> QOpenSLESEngine::availableDevices(QAudio::Mode mode) const
 {
     QList<QByteArray> devices;
diff --git a/src/plugins/opensles/qopenslesengine.h b/src/plugins/opensles/qopenslesengine.h
index 364b3ef60..c36b21488 100644
--- a/src/plugins/opensles/qopenslesengine.h
+++ b/src/plugins/opensles/qopenslesengine.h
@@ -62,6 +62,7 @@ public:
 
     static SLDataFormat_PCM audioFormatToSLFormatPCM(const QAudioFormat &format);
 
+    QByteArray defaultDevice(QAudio::Mode mode) const;
     QList<QByteArray> availableDevices(QAudio::Mode mode) const;
     QList<int> supportedChannelCounts(QAudio::Mode mode) const;
     QList<int> supportedSampleRates(QAudio::Mode mode) const;
diff --git a/src/plugins/opensles/qopenslesplugin.cpp b/src/plugins/opensles/qopenslesplugin.cpp
index 8f89d044d..9a2fbbf79 100644
--- a/src/plugins/opensles/qopenslesplugin.cpp
+++ b/src/plugins/opensles/qopenslesplugin.cpp
@@ -52,6 +52,11 @@ QOpenSLESPlugin::QOpenSLESPlugin(QObject *parent)
 {
 }
 
+QByteArray QOpenSLESPlugin::defaultDevice(QAudio::Mode mode) const
+{
+    return m_engine->defaultDevice(mode);
+}
+
 QList<QByteArray> QOpenSLESPlugin::availableDevices(QAudio::Mode mode) const
 {
     return m_engine->availableDevices(mode);
diff --git a/src/plugins/opensles/qopenslesplugin.h b/src/plugins/opensles/qopenslesplugin.h
index 2a967b27e..d45a47923 100644
--- a/src/plugins/opensles/qopenslesplugin.h
+++ b/src/plugins/opensles/qopenslesplugin.h
@@ -40,22 +40,25 @@
 #ifndef QOPENSLESPLUGIN_H
 #define QOPENSLESPLUGIN_H
 
-#include <qaudiosystemplugin.h>
+#include <QtMultimedia/qaudiosystemplugin.h>
+#include <QtMultimedia/private/qaudiosystempluginext_p.h>
 
 QT_BEGIN_NAMESPACE
 
 class QOpenSLESEngine;
 
-class QOpenSLESPlugin : public QAudioSystemPlugin
+class QOpenSLESPlugin : public QAudioSystemPlugin, public QAudioSystemPluginExtension
 {
     Q_OBJECT
 
     Q_PLUGIN_METADATA(IID "org.qt-project.qt.audiosystemfactory/5.0" FILE "opensles.json")
+    Q_INTERFACES(QAudioSystemPluginExtension)
 
 public:
     QOpenSLESPlugin(QObject *parent = 0);
     ~QOpenSLESPlugin() {}
 
+    QByteArray defaultDevice(QAudio::Mode mode) const;
     QList<QByteArray> availableDevices(QAudio::Mode mode) const;
     QAbstractAudioInput *createInput(const QByteArray &device);
     QAbstractAudioOutput *createOutput(const QByteArray &device);
diff --git a/src/plugins/pulseaudio/qpulseaudioengine.cpp b/src/plugins/pulseaudio/qpulseaudioengine.cpp
index 19ba7472f..eb8e2bf9d 100644
--- a/src/plugins/pulseaudio/qpulseaudioengine.cpp
+++ b/src/plugins/pulseaudio/qpulseaudioengine.cpp
@@ -338,14 +338,6 @@ void QPulseAudioEngine::updateDevices()
     pa_operation_unref(operation);
 
     unlock();
-
-    // Swap the default output to index 0
-    m_sinks.removeOne(m_defaultSink);
-    m_sinks.prepend(m_defaultSink);
-
-    // Swap the default input to index 0
-    m_sources.removeOne(m_defaultSource);
-    m_sources.prepend(m_defaultSource);
 }
 
 void QPulseAudioEngine::onContextFailed()
@@ -369,4 +361,9 @@ QList<QByteArray> QPulseAudioEngine::availableDevices(QAudio::Mode mode) const
     return mode == QAudio::AudioOutput ? m_sinks : m_sources;
 }
 
+QByteArray QPulseAudioEngine::defaultDevice(QAudio::Mode mode) const
+{
+    return (mode == QAudio::AudioOutput) ? m_defaultSink : m_defaultSource;
+}
+
 QT_END_NAMESPACE
diff --git a/src/plugins/pulseaudio/qpulseaudioengine.h b/src/plugins/pulseaudio/qpulseaudioengine.h
index 5eb96bf00..912df5242 100644
--- a/src/plugins/pulseaudio/qpulseaudioengine.h
+++ b/src/plugins/pulseaudio/qpulseaudioengine.h
@@ -53,7 +53,7 @@
 
 #include <QtCore/qmap.h>
 #include <QtCore/qbytearray.h>
-#include <qaudiosystemplugin.h>
+#include <QtMultimedia/qaudiosystemplugin.h>
 #include <pulse/pulseaudio.h>
 #include "qpulsehelpers.h"
 #include <qaudioformat.h>
@@ -91,6 +91,7 @@ public:
     }
 
     QList<QByteArray> availableDevices(QAudio::Mode mode) const;
+    QByteArray defaultDevice(QAudio::Mode mode) const;
 
 Q_SIGNALS:
     void contextFailed();
diff --git a/src/plugins/pulseaudio/qpulseaudioplugin.cpp b/src/plugins/pulseaudio/qpulseaudioplugin.cpp
index 2b7b22089..6b3019279 100644
--- a/src/plugins/pulseaudio/qpulseaudioplugin.cpp
+++ b/src/plugins/pulseaudio/qpulseaudioplugin.cpp
@@ -53,6 +53,11 @@ QPulseAudioPlugin::QPulseAudioPlugin(QObject *parent)
 {
 }
 
+QByteArray QPulseAudioPlugin::defaultDevice(QAudio::Mode mode) const
+{
+    return m_pulseEngine->defaultDevice(mode);
+}
+
 QList<QByteArray> QPulseAudioPlugin::availableDevices(QAudio::Mode mode) const
 {
     return m_pulseEngine->availableDevices(mode);
diff --git a/src/plugins/pulseaudio/qpulseaudioplugin.h b/src/plugins/pulseaudio/qpulseaudioplugin.h
index 4bad509e9..120d57df5 100644
--- a/src/plugins/pulseaudio/qpulseaudioplugin.h
+++ b/src/plugins/pulseaudio/qpulseaudioplugin.h
@@ -40,22 +40,25 @@
 #ifndef QPULSEAUDIOPLUGIN_H
 #define QPULSEAUDIOPLUGIN_H
 
-#include <qaudiosystemplugin.h>
+#include <QtMultimedia/qaudiosystemplugin.h>
+#include <QtMultimedia/private/qaudiosystempluginext_p.h>
 
 QT_BEGIN_NAMESPACE
 
 class QPulseAudioEngine;
 
-class QPulseAudioPlugin : public QAudioSystemPlugin
+class QPulseAudioPlugin : public QAudioSystemPlugin, public QAudioSystemPluginExtension
 {
     Q_OBJECT
 
     Q_PLUGIN_METADATA(IID "org.qt-project.qt.audiosystemfactory/5.0" FILE "pulseaudio.json")
+    Q_INTERFACES(QAudioSystemPluginExtension)
 
 public:
     QPulseAudioPlugin(QObject *parent = 0);
     ~QPulseAudioPlugin() {}
 
+    QByteArray defaultDevice(QAudio::Mode mode) const;
     QList<QByteArray> availableDevices(QAudio::Mode mode) const;
     QAbstractAudioInput *createInput(const QByteArray &device);
     QAbstractAudioOutput *createOutput(const QByteArray &device);
diff --git a/src/plugins/qnx-audio/audio/qnxaudioplugin.cpp b/src/plugins/qnx-audio/audio/qnxaudioplugin.cpp
index a3793fc3c..5d26c8954 100644
--- a/src/plugins/qnx-audio/audio/qnxaudioplugin.cpp
+++ b/src/plugins/qnx-audio/audio/qnxaudioplugin.cpp
@@ -55,6 +55,11 @@ QnxAudioPlugin::QnxAudioPlugin(QObject *parent)
 {
 }
 
+QByteArray QnxAudioPlugin::defaultDevice(QAudio::Mode mode) const
+{
+    return (mode == QAudio::AudioOutput) ? OUTPUT_ID : INPUT_ID;
+}
+
 QList<QByteArray> QnxAudioPlugin::availableDevices(QAudio::Mode mode) const
 {
     if (mode == QAudio::AudioOutput)
diff --git a/src/plugins/qnx-audio/audio/qnxaudioplugin.h b/src/plugins/qnx-audio/audio/qnxaudioplugin.h
index 5e2410619..1d8b8a74b 100644
--- a/src/plugins/qnx-audio/audio/qnxaudioplugin.h
+++ b/src/plugins/qnx-audio/audio/qnxaudioplugin.h
@@ -40,19 +40,22 @@
 #ifndef QNXAUDIOPLUGIN_H
 #define QNXAUDIOPLUGIN_H
 
-#include <qaudiosystemplugin.h>
+#include <QtMultimedia/qaudiosystemplugin.h>
+#include <QtMultimedia/private/qaudiosystempluginext_p.h>
 
 QT_BEGIN_NAMESPACE
 
-class QnxAudioPlugin : public QAudioSystemPlugin
+class QnxAudioPlugin : public QAudioSystemPlugin, public QAudioSystemPluginExtension
 {
     Q_OBJECT
     Q_PLUGIN_METADATA(IID "org.qt-project.qt.audiosystemfactory/5.0" FILE "qnx_audio.json")
+    Q_INTERFACES(QAudioSystemPluginExtension)
 
 public:
     explicit QnxAudioPlugin(QObject *parent = 0);
     ~QnxAudioPlugin() {}
 
+    QByteArray defaultDevice(QAudio::Mode mode) const Q_DECL_OVERRIDE;
     QList<QByteArray> availableDevices(QAudio::Mode mode) const Q_DECL_OVERRIDE;
     QAbstractAudioInput *createInput(const QByteArray &device) Q_DECL_OVERRIDE;
     QAbstractAudioOutput *createOutput(const QByteArray &device) Q_DECL_OVERRIDE;
diff --git a/src/plugins/wasapi/qwasapiplugin.cpp b/src/plugins/wasapi/qwasapiplugin.cpp
index 7b64a101d..39660b9c1 100644
--- a/src/plugins/wasapi/qwasapiplugin.cpp
+++ b/src/plugins/wasapi/qwasapiplugin.cpp
@@ -50,6 +50,11 @@ QWasapiPlugin::QWasapiPlugin(QObject *parent)
     qCDebug(lcMmPlugin) << __FUNCTION__;
 }
 
+QByteArray QWasapiPlugin::defaultDevice(QAudio::Mode mode) const
+{
+    return QWasapiUtils::defaultDevice(mode);
+}
+
 QList<QByteArray> QWasapiPlugin::availableDevices(QAudio::Mode mode) const
 {
     qCDebug(lcMmPlugin) << __FUNCTION__ << mode;
diff --git a/src/plugins/wasapi/qwasapiplugin.h b/src/plugins/wasapi/qwasapiplugin.h
index 18c2e9575..697e9bd78 100644
--- a/src/plugins/wasapi/qwasapiplugin.h
+++ b/src/plugins/wasapi/qwasapiplugin.h
@@ -39,22 +39,25 @@
 
 #include <QtCore/QLoggingCategory>
 #include <QtCore/QList>
-#include <QtMultimedia/QAudioSystemPlugin>
+#include <QtMultimedia/qaudiosystemplugin.h>
+#include <QtMultimedia/private/qaudiosystempluginext_p.h>
 
 QT_BEGIN_NAMESPACE
 
 Q_DECLARE_LOGGING_CATEGORY(lcMmPlugin)
 
-class QWasapiPlugin : public QAudioSystemPlugin
+class QWasapiPlugin : public QAudioSystemPlugin, public QAudioSystemPluginExtension
 {
     Q_OBJECT
 
     Q_PLUGIN_METADATA(IID "org.qt-project.qt.audiosystemfactory/5.0" FILE "wasapi.json")
+    Q_INTERFACES(QAudioSystemPluginExtension)
 
 public:
     explicit QWasapiPlugin(QObject *parent = 0);
     ~QWasapiPlugin() {}
 
+    QByteArray defaultDevice(QAudio::Mode mode) const Q_DECL_OVERRIDE;
     QList<QByteArray> availableDevices(QAudio::Mode mode) const Q_DECL_OVERRIDE;
     QAbstractAudioInput *createInput(const QByteArray &device) Q_DECL_OVERRIDE;
     QAbstractAudioOutput *createOutput(const QByteArray &device) Q_DECL_OVERRIDE;
diff --git a/src/plugins/wasapi/qwasapiutils.cpp b/src/plugins/wasapi/qwasapiutils.cpp
index 87daa4e45..0e39ee32b 100644
--- a/src/plugins/wasapi/qwasapiutils.cpp
+++ b/src/plugins/wasapi/qwasapiutils.cpp
@@ -175,6 +175,29 @@ bool QWasapiUtils::convertFromNativeFormat(const WAVEFORMATEX *native, QAudioFor
     return true;
 }
 
+QByteArray QWasapiUtils::defaultDevice(QAudio::Mode mode)
+{
+    qCDebug(lcMmUtils) << __FUNCTION__ << mode;
+
+    ComPtr<IMediaDeviceStatics> mediaDeviceStatics;
+    HRESULT hr;
+
+    hr = GetActivationFactory(HString::MakeReference(RuntimeClass_Windows_Media_Devices_MediaDevice).Get(), &mediaDeviceStatics);
+    Q_ASSERT_SUCCEEDED(hr);
+
+    HString defaultAudioDevice;
+    quint32 dADSize = 0;
+
+    if (mode == QAudio::AudioOutput)
+        hr = mediaDeviceStatics->GetDefaultAudioRenderId(AudioDeviceRole_Default, defaultAudioDevice.GetAddressOf());
+    else
+        hr = mediaDeviceStatics->GetDefaultAudioCaptureId(AudioDeviceRole_Default, defaultAudioDevice.GetAddressOf());
+
+    const wchar_t *dadWStr = defaultAudioDevice.GetRawBuffer(&dADSize);
+    const QString defaultAudioDeviceId = QString::fromWCharArray(dadWStr, dADSize);
+    return defaultAudioDeviceId.toLocal8Bit();
+}
+
 QList<QByteArray> QWasapiUtils::availableDevices(QAudio::Mode mode)
 {
     qCDebug(lcMmUtils) << __FUNCTION__ << mode;
@@ -186,16 +209,6 @@ QList<QByteArray> QWasapiUtils::availableDevices(QAudio::Mode mode)
                               &statics);
     Q_ASSERT_SUCCEEDED(hr);
 
-    ComPtr<IMediaDeviceStatics> mediaDeviceStatics;
-    hr = GetActivationFactory(HString::MakeReference(RuntimeClass_Windows_Media_Devices_MediaDevice).Get(), &mediaDeviceStatics);
-    Q_ASSERT_SUCCEEDED(hr);
-
-    HString defaultAudioRender;
-    quint32 dARSize = 0;
-    hr = mediaDeviceStatics->GetDefaultAudioRenderId(AudioDeviceRole_Default, defaultAudioRender.GetAddressOf());
-    const wchar_t *darWStr = defaultAudioRender.GetRawBuffer(&dARSize);
-    const QString defaultAudioDeviceId = QString::fromWCharArray(darWStr, dARSize);
-
     DeviceClass dc = mode == QAudio::AudioInput ? DeviceClass_AudioCapture : DeviceClass_AudioRender;
 
     QList<QByteArray> &deviceNames = mode == QAudio::AudioInput ? gMapping->inputDeviceNames : gMapping->outputDeviceNames;
@@ -245,18 +258,6 @@ QList<QByteArray> QWasapiUtils::availableDevices(QAudio::Mode mode)
         const wchar_t *idWStr = hString.GetRawBuffer(&size);
         const QString deviceId = QString::fromWCharArray(idWStr, size);
 
-        boolean def;
-        hr = item->get_IsDefault(&def);
-        if (FAILED(hr)) {
-            qErrnoWarning(hr, "Could not access audio device default.");
-            continue;
-        }
-
-        // At least on desktop no device is marked as default
-        // Hence use the default audio device string from above
-        if (!def && !defaultAudioDeviceId.isEmpty())
-            def = defaultAudioDeviceId == deviceId;
-
         boolean enabled;
         hr = item->get_IsEnabled(&enabled);
         if (FAILED(hr)) {
@@ -265,14 +266,10 @@ QList<QByteArray> QWasapiUtils::availableDevices(QAudio::Mode mode)
         }
 
         qCDebug(lcMmUtils) << "Audio Device:" << deviceName << " ID:" << deviceId
-                            << " Enabled:" << enabled << " Default:" << def;
-        if (def) {
-            deviceNames.prepend(deviceName.toLocal8Bit());
-            deviceIds.prepend(deviceId);
-        } else {
-            deviceNames.append(deviceName.toLocal8Bit());
-            deviceIds.append(deviceId);
-        }
+                            << " Enabled:" << enabled;
+
+        deviceNames.append(deviceName.toLocal8Bit());
+        deviceIds.append(deviceId);
     }
     return deviceNames;
 }
diff --git a/src/plugins/wasapi/qwasapiutils.h b/src/plugins/wasapi/qwasapiutils.h
index 21eff3583..3dda0e1a5 100644
--- a/src/plugins/wasapi/qwasapiutils.h
+++ b/src/plugins/wasapi/qwasapiutils.h
@@ -134,6 +134,7 @@ namespace QWasapiUtils
     bool convertToNativeFormat(const QAudioFormat &qt, WAVEFORMATEX *native);
     bool convertFromNativeFormat(const WAVEFORMATEX *native, QAudioFormat *qt);
 
+    QByteArray defaultDevice(QAudio::Mode mode);
     QList<QByteArray> availableDevices(QAudio::Mode mode);
     Microsoft::WRL::ComPtr<AudioInterface> createOrGetInterface(const QByteArray &dev, QAudio::Mode mode);
 }
diff --git a/src/plugins/windowsaudio/qwindowsaudiodeviceinfo.cpp b/src/plugins/windowsaudio/qwindowsaudiodeviceinfo.cpp
index ca79ebbec..83e9ccfc8 100644
--- a/src/plugins/windowsaudio/qwindowsaudiodeviceinfo.cpp
+++ b/src/plugins/windowsaudio/qwindowsaudiodeviceinfo.cpp
@@ -457,22 +457,14 @@ QList<QByteArray> QWindowsAudioDeviceInfo::availableDevices(QAudio::Mode mode)
     return devices;
 }
 
-QByteArray QWindowsAudioDeviceInfo::defaultOutputDevice()
+QByteArray QWindowsAudioDeviceInfo::defaultDevice(QAudio::Mode mode)
 {
+    const QString &name = (mode == QAudio::AudioOutput) ? QStringLiteral("Default Output Device")
+                                                        : QStringLiteral("Default Input Device");
     QByteArray defaultDevice;
     QDataStream ds(&defaultDevice, QIODevice::WriteOnly);
     ds << quint32(WAVE_MAPPER) // device ID for default device
-       << QStringLiteral("Default Output Device");
-
-    return defaultDevice;
-}
-
-QByteArray QWindowsAudioDeviceInfo::defaultInputDevice()
-{
-    QByteArray defaultDevice;
-    QDataStream ds(&defaultDevice, QIODevice::WriteOnly);
-    ds << quint32(WAVE_MAPPER) // device ID for default device
-       << QStringLiteral("Default Input Device");
+       << name;
 
     return defaultDevice;
 }
diff --git a/src/plugins/windowsaudio/qwindowsaudiodeviceinfo.h b/src/plugins/windowsaudio/qwindowsaudiodeviceinfo.h
index d4833d3fc..d84eb8acf 100644
--- a/src/plugins/windowsaudio/qwindowsaudiodeviceinfo.h
+++ b/src/plugins/windowsaudio/qwindowsaudiodeviceinfo.h
@@ -88,8 +88,7 @@ public:
     QList<int> supportedSampleSizes();
     QList<QAudioFormat::Endian> supportedByteOrders();
     QList<QAudioFormat::SampleType> supportedSampleTypes();
-    static QByteArray defaultInputDevice();
-    static QByteArray defaultOutputDevice();
+    static QByteArray defaultDevice(QAudio::Mode mode);
     static QList<QByteArray> availableDevices(QAudio::Mode);
 
 private:
diff --git a/src/plugins/windowsaudio/qwindowsaudioplugin.cpp b/src/plugins/windowsaudio/qwindowsaudioplugin.cpp
index ba1dba4c2..8f532fa70 100644
--- a/src/plugins/windowsaudio/qwindowsaudioplugin.cpp
+++ b/src/plugins/windowsaudio/qwindowsaudioplugin.cpp
@@ -49,6 +49,11 @@ QWindowsAudioPlugin::QWindowsAudioPlugin(QObject *parent)
 {
 }
 
+QByteArray QWindowsAudioPlugin::defaultDevice(QAudio::Mode mode) const
+{
+    return QWindowsAudioDeviceInfo::defaultDevice(mode);
+}
+
 QList<QByteArray> QWindowsAudioPlugin::availableDevices(QAudio::Mode mode) const
 {
     return QWindowsAudioDeviceInfo::availableDevices(mode);
diff --git a/src/plugins/windowsaudio/qwindowsaudioplugin.h b/src/plugins/windowsaudio/qwindowsaudioplugin.h
index fb4749e0d..7b500a39c 100644
--- a/src/plugins/windowsaudio/qwindowsaudioplugin.h
+++ b/src/plugins/windowsaudio/qwindowsaudioplugin.h
@@ -41,19 +41,22 @@
 #define QWINDOWSAUDIOPLUGIN_H
 
 #include <QtMultimedia/qaudiosystemplugin.h>
+#include <QtMultimedia/private/qaudiosystempluginext_p.h>
 
 QT_BEGIN_NAMESPACE
 
-class QWindowsAudioPlugin : public QAudioSystemPlugin
+class QWindowsAudioPlugin : public QAudioSystemPlugin, public QAudioSystemPluginExtension
 {
     Q_OBJECT
 
     Q_PLUGIN_METADATA(IID "org.qt-project.qt.audiosystemfactory/5.0" FILE "windowsaudio.json")
+    Q_INTERFACES(QAudioSystemPluginExtension)
 
 public:
     QWindowsAudioPlugin(QObject *parent = 0);
     ~QWindowsAudioPlugin() {}
 
+    QByteArray defaultDevice(QAudio::Mode mode) const Q_DECL_OVERRIDE;
     QList<QByteArray> availableDevices(QAudio::Mode mode) const Q_DECL_OVERRIDE;
     QAbstractAudioInput *createInput(const QByteArray &device) Q_DECL_OVERRIDE;
     QAbstractAudioOutput *createOutput(const QByteArray &device) Q_DECL_OVERRIDE;