The QAudioSink class provides an interface for sending audio data to an audio output device. More...

#include <qaudiosink.h>

Inheritance diagram for QAudioSink:

Collaboration diagram for QAudioSink:

Signals
void	stateChanged (QAudio::State state)
	This signal is emitted when the device state has changed.

Signals inherited from QObject
void	destroyed (QObject *=nullptr)
	This signal is emitted immediately before the object obj is destroyed, after any instances of QPointer have been notified, and cannot be blocked.

void	objectNameChanged (const QString &objectName, QPrivateSignal)
	This signal is emitted after the object's name has been changed.

Public Member Functions
	QAudioSink (const QAudioFormat &format=QAudioFormat(), QObject *parent=nullptr)
	Construct a new audio output and attach it to parent.

	QAudioSink (const QAudioDevice &audioDeviceInfo, const QAudioFormat &format=QAudioFormat(), QObject *parent=nullptr)
	Construct a new audio output and attach it to parent.

	~QAudioSink ()
	Destroys this audio output.

bool	isNull () const
	Returns `true` is the QAudioSink instance is `null`, otherwise returns `false`.

QAudioFormat	format () const
	Returns the QAudioFormat being used.

void	start (QIODevice *device)
	Starts transferring audio data from the device to the system's audio output.

QIODevice *	start ()
	Returns a pointer to the internal QIODevice being used to transfer data to the system's audio output.

void	stop ()
	Stops the audio output, detaching from the system resource.

void	reset ()
	Drops all audio data in the buffers, resets buffers to zero.

void	suspend ()
	Stops processing audio data, preserving buffered audio data.

void	resume ()
	Resumes processing audio data after a suspend().

void	setBufferSize (qsizetype bytes)
	Sets the audio buffer size to value in bytes.

qsizetype	bufferSize () const
	Returns the audio buffer size in bytes.

qsizetype	bytesFree () const
	Returns the number of free bytes available in the audio buffer.

qint64	processedUSecs () const
	Returns the amount of audio data processed since start() was called (in microseconds).

qint64	elapsedUSecs () const
	Returns the microseconds since start() was called, including time in Idle and Suspend states.

QAudio::Error	error () const
	Returns the error state.

QAudio::State	state () const
	Returns the state of audio processing.

void	setVolume (qreal)
	Sets the output volume to volume.

qreal	volume () const
	Returns the volume between 0.0 and 1.0 inclusive.

Public Member Functions inherited from QObject
Q_INVOKABLE	QObject (QObject *parent=nullptr)
	Constructs an object with parent object parent.

virtual	~QObject ()
	Destroys the object, deleting all its child objects.

virtual bool	event (QEvent *event)
	This virtual function receives events to an object and should return true if the event e was recognized and processed.

virtual bool	eventFilter (QObject watched, QEvent event)
	Filters events if this object has been installed as an event filter for the watched object.

QString	objectName () const

Q_WEAK_OVERLOAD void	setObjectName (const QString &name)
	Sets the object's name to name.

void	setObjectName (QAnyStringView name)
	This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.

QBindable< QString >	bindableObjectName ()

bool	isWidgetType () const
	Returns `true` if the object is a widget; otherwise returns `false`.

bool	isWindowType () const
	Returns `true` if the object is a window; otherwise returns `false`.

bool	isQuickItemType () const
	Returns `true` if the object is a QQuickItem; otherwise returns `false`.

bool	signalsBlocked () const noexcept
	Returns `true` if signals are blocked; otherwise returns `false`.

bool	blockSignals (bool b) noexcept
	If block is true, signals emitted by this object are blocked (i.e., emitting a signal will not invoke anything connected to it).

QThread *	thread () const
	Returns the thread in which the object lives.

void	moveToThread (QThread *thread)
	Changes the thread affinity for this object and its children.

int	startTimer (int interval, Qt::TimerType timerType=Qt::CoarseTimer)
	This is an overloaded function that will start a timer of type timerType and a timeout of interval milliseconds.

int	startTimer (std::chrono::milliseconds time, Qt::TimerType timerType=Qt::CoarseTimer)

void	killTimer (int id)
	Kills the timer with timer identifier, id.

template<typename T >
T	findChild (const QString &aName=QString(), Qt::FindChildOptions options=Qt::FindChildrenRecursively) const
	Returns the child of this object that can be cast into type T and that is called name, or \nullptr if there is no such object.

template<typename T >
QList< T >	findChildren (const QString &aName, Qt::FindChildOptions options=Qt::FindChildrenRecursively) const
	Returns all children of this object with the given name that can be cast to type T, or an empty list if there are no such objects.

template<typename T >
QList< T >	findChildren (Qt::FindChildOptions options=Qt::FindChildrenRecursively) const
	This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.

const QObjectList &	children () const
	Returns a list of child objects.

void	setParent (QObject *parent)
	Makes the object a child of parent.

void	installEventFilter (QObject *filterObj)
	Installs an event filter filterObj on this object.

void	removeEventFilter (QObject *obj)
	Removes an event filter object obj from this object.

QMetaObject::Connection	connect (const QObject sender, const char signal, const char *member, Qt::ConnectionType type=Qt::AutoConnection) const

bool	disconnect (const char signal=nullptr, const QObject receiver=nullptr, const char *member=nullptr) const

bool	disconnect (const QObject receiver, const char member=nullptr) const

void	dumpObjectTree () const
	Dumps a tree of children to the debug output.

void	dumpObjectInfo () const
	Dumps information about signal connections, etc.

bool	setProperty (const char *name, const QVariant &value)
	Sets the value of the object's name property to value.

bool	setProperty (const char *name, QVariant &&value)

QVariant	property (const char *name) const
	Returns the value of the object's name property.

QList< QByteArray >	dynamicPropertyNames () const

QBindingStorage *	bindingStorage ()

const QBindingStorage *	bindingStorage () const

QObject *	parent () const
	Returns a pointer to the parent object.

bool	inherits (const char *classname) const
	Returns `true` if this object is an instance of a class that inherits className or a QObject subclass that inherits className; otherwise returns `false`.

Additional Inherited Members
Public Slots inherited from QObject
void	deleteLater ()
	\threadsafe

Static Public Member Functions inherited from QObject
static QMetaObject::Connection	connect (const QObject sender, const char signal, const QObject receiver, const char member, Qt::ConnectionType=Qt::AutoConnection)
	\threadsafe

static QMetaObject::Connection	connect (const QObject sender, const QMetaMethod &signal, const QObject receiver, const QMetaMethod &method, Qt::ConnectionType type=Qt::AutoConnection)

template<typename Func1 , typename Func2 >
static QMetaObject::Connection	connect (const typename QtPrivate::FunctionPointer< Func1 >::Object sender, Func1 signal, const typename QtPrivate::ContextTypeForFunctor< Func2 >::ContextType context, Func2 &&slot, Qt::ConnectionType type=Qt::AutoConnection)

template<typename Func1 , typename Func2 >
static QMetaObject::Connection	connect (const typename QtPrivate::FunctionPointer< Func1 >::Object *sender, Func1 signal, Func2 &&slot)

static bool	disconnect (const QObject sender, const char signal, const QObject receiver, const char member)
	\threadsafe

static bool	disconnect (const QObject sender, const QMetaMethod &signal, const QObject receiver, const QMetaMethod &member)

static bool	disconnect (const QMetaObject::Connection &)
	Disconnect a connection.

template<typename Func1 , typename Func2 >
static bool	disconnect (const typename QtPrivate::FunctionPointer< Func1 >::Object sender, Func1 signal, const typename QtPrivate::FunctionPointer< Func2 >::Object receiver, Func2 slot)

template<typename Func1 >
static bool	disconnect (const typename QtPrivate::FunctionPointer< Func1 >::Object sender, Func1 signal, const QObject receiver, void **zero)

Protected Member Functions inherited from QObject
QObject *	sender () const
	Returns a pointer to the object that sent the signal, if called in a slot activated by a signal; otherwise it returns \nullptr.

int	senderSignalIndex () const

int	receivers (const char *signal) const
	Returns the number of receivers connected to the signal.

bool	isSignalConnected (const QMetaMethod &signal) const

virtual void	timerEvent (QTimerEvent *event)
	This event handler can be reimplemented in a subclass to receive timer events for the object.

virtual void	childEvent (QChildEvent *event)
	This event handler can be reimplemented in a subclass to receive child events.

virtual void	customEvent (QEvent *event)
	This event handler can be reimplemented in a subclass to receive custom events.

virtual void	connectNotify (const QMetaMethod &signal)

virtual void	disconnectNotify (const QMetaMethod &signal)

	QObject (QObjectPrivate &dd, QObject *parent=nullptr)

Protected Attributes inherited from QObject
QScopedPointer< QObjectData >	d_ptr

Properties inherited from QObject
QString	objectName
	the name of this object

Related Symbols inherited from QObject
template< class T > T	qobject_cast (const QObject *object)
	Returns the given object cast to type T if the object is of type T (or of a subclass); otherwise returns \nullptr.

template< typename T > T	qFindChildqFindChildren (const QObject *obj, const QString &name)()

template< typename T > QList< T >	qFindChildrenqFindChildren (const QObject *obj, const QString &name)()

	QObjectList
	\macro Q_CLASSINFO(Name, Value)

Detailed Description

The QAudioSink class provides an interface for sending audio data to an audio output device.

\inmodule QtMultimedia

You can construct an audio output with the system's default audio output device. It is also possible to create QAudioSink with a specific QAudioDevice. When you create the audio output, you should also send in the QAudioFormat to be used for the playback (see the QAudioFormat class description for details).

To play a file:

Starting to play an audio stream is simply a matter of calling start() with a QIODevice. QAudioSink will then fetch the data it needs from the io device. So playing back an audio file is as simple as:

The file will start playing assuming that the audio system and output device support it. If you run out of luck, check what's up with the error() function.

After the file has finished playing, we need to stop the device:

At any given time, the QAudioSink will be in one of four states: active, suspended, stopped, or idle. These states are described by the QAudio::State enum. State changes are reported through the stateChanged() signal. You can use this signal to, for instance, update the GUI of the application; the mundane example here being changing the state of a { play/pause } button. You request a state change directly with suspend(), stop(), reset(), resume(), and start().

If an error occurs, you can fetch the \l{QAudio::Error}{error type} with the error() function. Please see the QAudio::Error enum for a description of the possible errors that are reported. When QAudio::UnderrunError is encountered, the state changes to QAudio::IdleState, when another error is encountered, the state changes to QAudio::StoppedState. You can check for errors by connecting to the stateChanged() signal:

See also: QAudioSource, QAudioDevice

Definition at line 23 of file qaudiosink.h.

Constructor & Destructor Documentation

◆ QAudioSink() [1/2]

QAudioSink::QAudioSink	(	const QAudioFormat &	format = `QAudioFormat()`,
		QObject *	parent = `nullptr`
	)

explicit

Construct a new audio output and attach it to parent.

The default audio output device is used with the output format parameters.

Definition at line 77 of file qaudiosink.cpp.

◆ QAudioSink() [2/2]

QAudioSink::QAudioSink	(	const QAudioDevice &	audioDevice,
		const QAudioFormat &	format = `QAudioFormat()`,
		QObject *	parent = `nullptr`
	)

explicit

Construct a new audio output and attach it to parent.

The device referenced by audioDevice is used with the output format parameters.

Definition at line 87 of file qaudiosink.cpp.

References QPlatformMediaDevices::audioOutputDevice(), QObject::connect(), emit, QPlatformMediaDevices::instance(), QObject::parent(), qWarning, state(), QPlatformAudioSink::state(), stateChanged(), and QPlatformAudioSink::stateChanged().

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◆ ~QAudioSink()

QAudioSink::~QAudioSink ( )

Destroys this audio output.

This will release any system resources used and free any buffers.

Definition at line 114 of file qaudiosink.cpp.

Member Function Documentation

◆ bufferSize()

qsizetype QAudioSink::bufferSize ( ) const

Returns the audio buffer size in bytes.

If called before start(), returns platform default value. If called before start() but setBufferSize() was called prior, returns value set by setBufferSize(). If called after start(), returns the actual buffer size being used. This may not be what was set previously by setBufferSize().

Definition at line 256 of file qaudiosink.cpp.

References QPlatformAudioSink::bufferSize().

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◆ bytesFree()

qsizetype QAudioSink::bytesFree ( ) const

Returns the number of free bytes available in the audio buffer.

Note: The returned value is only valid while in QAudio::ActiveState or QAudio::IdleState state, otherwise returns zero.

Definition at line 228 of file qaudiosink.cpp.

References QPlatformAudioSink::bytesFree().

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◆ elapsedUSecs()

qint64 QAudioSink::elapsedUSecs ( ) const

Returns the microseconds since start() was called, including time in Idle and Suspend states.

Definition at line 274 of file qaudiosink.cpp.

References QPlatformAudioSink::elapsedTime, QElapsedTimer::nsecsElapsed(), state(), and QAudio::StoppedState.

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◆ error()

QAudio::Error QAudioSink::error ( ) const

Returns the error state.

Definition at line 282 of file qaudiosink.cpp.

References QPlatformAudioSink::error(), and QAudio::OpenError.

Referenced by AudioOutputExample::handleStateChanged().

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◆ format()

QAudioFormat QAudioSink::format ( ) const

Returns the QAudioFormat being used.

Definition at line 123 of file qaudiosink.cpp.

References QPlatformAudioSink::format().

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◆ isNull()

bool QAudioSink::isNull ( ) const

inline

Returns true is the QAudioSink instance is null, otherwise returns false.

Definition at line 32 of file qaudiosink.h.

References d.

◆ processedUSecs()

qint64 QAudioSink::processedUSecs ( ) const

Returns the amount of audio data processed since start() was called (in microseconds).

Definition at line 265 of file qaudiosink.cpp.

References QPlatformAudioSink::processedUSecs().

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◆ reset()

void QAudioSink::reset ( )

Drops all audio data in the buffers, resets buffers to zero.

Definition at line 191 of file qaudiosink.cpp.

References QPlatformAudioSink::reset().

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◆ resume()

void QAudioSink::resume ( )

Resumes processing audio data after a suspend().

Sets state() to the state the sink had when suspend() was called, and sets error() to QAudioError::NoError. This function does nothing if the audio sink's state is not QAudio::SuspendedState.

Definition at line 216 of file qaudiosink.cpp.

References QPlatformAudioSink::resume().

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◆ setBufferSize()

void QAudioSink::setBufferSize ( qsizetype value )

Sets the audio buffer size to value in bytes.

Note: This function can be called anytime before start(). Calls to this are ignored after start(). It should not be assumed that the buffer size set is the actual buffer size used - call bufferSize() anytime after start() to return the actual buffer size being used.

Definition at line 241 of file qaudiosink.cpp.

References QPlatformAudioSink::setBufferSize().

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◆ setVolume()

void QAudioSink::setVolume ( qreal volume )

Sets the output volume to volume.

The volume is scaled linearly from 0.0 (silence) to 1.0 (full volume). Values outside this range will be clamped.

The default volume is 1.0.

Note: Adjustments to the volume will change the volume of this audio stream, not the global volume.

UI volume controls should usually be scaled non-linearly. For example, using a logarithmic scale will produce linear changes in perceived loudness, which is what a user would normally expect from a volume control. See QAudio::convertVolume() for more details.

Definition at line 311 of file qaudiosink.cpp.

References qBound(), QPlatformAudioSink::setVolume(), and volume().

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