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Qt 4.8
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Qt 4.8
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The QAudioOutput class provides an interface for sending audio data to an audio output device. More...
#include <qaudiooutput.h>
Signals | |
| void | notify () |
| This signal is emitted when x ms of audio data has been processed the interval set by setNotifyInterval(x). More... | |
| void | stateChanged (QAudio::State) |
| This signal is emitted when the device state has changed. More... | |
 Signals inherited from QObject | |
| void | destroyed (QObject *=0) |
| This signal is emitted immediately before the object obj is destroyed, and can not be blocked. More... | |
Public Functions | |
| int | bufferSize () const |
| Returns the audio buffer size in bytes. More... | |
| int | bytesFree () const |
| Returns the free space available in bytes in the audio buffer. More... | |
| qint64 | elapsedUSecs () const |
| Returns the microseconds since start() was called, including time in Idle and Suspend states. More... | |
| QAudio::Error | error () const |
| Returns the error state. More... | |
| QAudioFormat | format () const |
| Returns the QAudioFormat being used. More... | |
| int | notifyInterval () const |
| Returns the notify interval in milliseconds. More... | |
| int | periodSize () const |
| Returns the period size in bytes. More... | |
| qint64 | processedUSecs () const |
| Returns the amount of audio data processed by the class since start() was called in microseconds. More... | |
| QAudioOutput (const QAudioFormat &format=QAudioFormat(), QObject *parent=0) | |
| Construct a new audio output and attach it to parent. More... | |
| QAudioOutput (const QAudioDeviceInfo &audioDeviceInfo, const QAudioFormat &format=QAudioFormat(), QObject *parent=0) | |
| Construct a new audio output and attach it to parent. More... | |
| void | reset () |
| Drops all audio data in the buffers, resets buffers to zero. More... | |
| void | resume () |
| Resumes processing audio data after a suspend(). More... | |
| void | setBufferSize (int bytes) |
| Sets the audio buffer size to value in bytes. More... | |
| void | setNotifyInterval (int milliSeconds) |
| Sets the interval for notify() signal to be emitted. More... | |
| void | start (QIODevice *device) |
| Uses the device as the QIODevice to transfer data. More... | |
| QIODevice * | start () |
| Returns a pointer to the QIODevice being used to handle the data transfer. More... | |
| QAudio::State | state () const |
| Returns the state of audio processing. More... | |
| void | stop () |
| Stops the audio output, detaching from the system resource. More... | |
| void | suspend () |
| Stops processing audio data, preserving buffered audio data. More... | |
| ~QAudioOutput () | |
| Destroys this audio output. More... | |
| Public Functions inherited from QObject | |
| bool | blockSignals (bool b) |
| If block is true, signals emitted by this object are blocked (i.e., emitting a signal will not invoke anything connected to it). More... | |
| const QObjectList & | children () const |
| Returns a list of child objects. More... | |
| bool | connect (const QObject *sender, const char *signal, const char *member, Qt::ConnectionType type=Qt::AutoConnection) const |
| bool | disconnect (const char *signal=0, const QObject *receiver=0, const char *member=0) |
| bool | disconnect (const QObject *receiver, const char *member=0) |
| void | dumpObjectInfo () |
| Dumps information about signal connections, etc. More... | |
| void | dumpObjectTree () |
| Dumps a tree of children to the debug output. More... | |
| QList< QByteArray > | dynamicPropertyNames () const |
| Returns the names of all properties that were dynamically added to the object using setProperty(). More... | |
| virtual bool | event (QEvent *) |
| This virtual function receives events to an object and should return true if the event e was recognized and processed. More... | |
| virtual bool | eventFilter (QObject *, QEvent *) |
| Filters events if this object has been installed as an event filter for the watched object. More... | |
| template<typename T > | |
| T | findChild (const QString &aName=QString()) const |
| Returns the child of this object that can be cast into type T and that is called name, or 0 if there is no such object. More... | |
| template<typename T > | |
| QList< T > | findChildren (const QString &aName=QString()) 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. More... | |
| template<typename T > | |
| QList< T > | findChildren (const QRegExp &re) const |
| 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. More... | |
| void | installEventFilter (QObject *) |
| Installs an event filter filterObj on this object. More... | |
| bool | isWidgetType () const |
| Returns true if the object is a widget; otherwise returns false. More... | |
| void | killTimer (int id) |
| Kills the timer with timer identifier, id. More... | |
| virtual const QMetaObject * | metaObject () const |
| Returns a pointer to the meta-object of this object. More... | |
| void | moveToThread (QThread *thread) |
| Changes the thread affinity for this object and its children. More... | |
| QString | objectName () const |
| QObject * | parent () const |
| Returns a pointer to the parent object. More... | |
| QVariant | property (const char *name) const |
| Returns the value of the object's name property. More... | |
| Q_INVOKABLE | QObject (QObject *parent=0) |
| Constructs an object with parent object parent. More... | |
| void | removeEventFilter (QObject *) |
| Removes an event filter object obj from this object. More... | |
| void | setObjectName (const QString &name) |
| void | setParent (QObject *) |
| Makes the object a child of parent. More... | |
| bool | setProperty (const char *name, const QVariant &value) |
| Sets the value of the object's name property to value. More... | |
| void | setUserData (uint id, QObjectUserData *data) |
| bool | signalsBlocked () const |
| Returns true if signals are blocked; otherwise returns false. More... | |
| int | startTimer (int interval) |
| Starts a timer and returns a timer identifier, or returns zero if it could not start a timer. More... | |
| QThread * | thread () const |
| Returns the thread in which the object lives. More... | |
| QObjectUserData * | userData (uint id) const |
| virtual | ~QObject () |
| Destroys the object, deleting all its child objects. More... | |
Properties | |
| QAbstractAudioOutput * | d |
Additional Inherited Members | |
| Public Slots inherited from QObject | |
| void | deleteLater () |
| Schedules this object for deletion. More... | |
| Static Public Functions inherited from QObject | |
| static bool | connect (const QObject *sender, const char *signal, const QObject *receiver, const char *member, Qt::ConnectionType=Qt::AutoConnection) |
| Creates a connection of the given type from the signal in the sender object to the method in the receiver object. More... | |
| static bool | connect (const QObject *sender, const QMetaMethod &signal, const QObject *receiver, const QMetaMethod &method, Qt::ConnectionType type=Qt::AutoConnection) |
| static bool | disconnect (const QObject *sender, const char *signal, const QObject *receiver, const char *member) |
| Disconnects signal in object sender from method in object receiver. More... | |
| static bool | disconnect (const QObject *sender, const QMetaMethod &signal, const QObject *receiver, const QMetaMethod &member) |
| static uint | registerUserData () |
| static QString | tr (const char *sourceText, const char *comment=0, int n=-1) |
| static QString | trUtf8 (const char *sourceText, const char *comment=0, int n=-1) |
| Static Public Variables inherited from QObject | |
| static const QMetaObject | staticMetaObject |
| This variable stores the meta-object for the class. More... | |
| Protected Functions inherited from QObject | |
| virtual void | childEvent (QChildEvent *) |
| This event handler can be reimplemented in a subclass to receive child events. More... | |
| virtual void | connectNotify (const char *signal) |
| This virtual function is called when something has been connected to signal in this object. More... | |
| virtual void | customEvent (QEvent *) |
| This event handler can be reimplemented in a subclass to receive custom events. More... | |
| virtual void | disconnectNotify (const char *signal) |
| This virtual function is called when something has been disconnected from signal in this object. More... | |
| QObject (QObjectPrivate &dd, QObject *parent=0) | |
| int | receivers (const char *signal) const |
| Returns the number of receivers connected to the signal. More... | |
| 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 0. More... | |
| int | senderSignalIndex () const |
| virtual void | timerEvent (QTimerEvent *) |
| This event handler can be reimplemented in a subclass to receive timer events for the object. More... | |
| Protected Variables inherited from QObject | |
| QScopedPointer< QObjectData > | d_ptr |
| Static Protected Variables inherited from QObject | |
| static const QMetaObject | staticQtMetaObject |
| Related Functions inherited from QObject | |
| T | qFindChildqFindChildren (const QObject *obj, const QString &name)() |
| QList< T > | qFindChildrenqFindChildren (const QObject *obj, const QString &name)() |
| QList< T > | qFindChildrenqFindChildren (const QObject *obj, const QRegExp ®Exp)() |
| T * | qobject_cast (QObject *object) |
| QObjectList | |
| void * | qt_find_obj_child (QObject *parent, const char *type, const QString &name) |
| Returns a pointer to the object named name that inherits type and with a given parent. More... | |
The QAudioOutput class provides an interface for sending audio data to an audio output device.
You can construct an audio output with the system's default audio output device. It is also possible to create QAudioOutput with a specific QAudioDeviceInfo. 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. QAudioOutput will then fetch the data it needs from the io device. So playing back an audio file is as simple as:
... 4
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 QAudioOutput 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().
While the stream is playing, you can set a notify interval in milliseconds with setNotifyInterval(). This interval specifies the time between two emissions of the notify() signal. This is relative to the position in the stream, i.e., if the QAudioOutput is in the SuspendedState or the IdleState, the notify() signal is not emitted. A typical use-case would be to update a slider that allows seeking in the stream. If you want the time since playback started regardless of which states the audio output has been in, elapsedUSecs() is the function for you.
If an error occurs, you can fetch the error type with the error() function. Please see the QAudio::Error enum for a description of the possible errors that are reported. When an error is encountered, the state changes to QAudio::StoppedState. You can check for errors by connecting to the stateChanged() signal:
Definition at line 63 of file qaudiooutput.h.
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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 125 of file qaudiooutput.cpp.
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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 139 of file qaudiooutput.cpp.
| QAudioOutput::~QAudioOutput | ( | ) |
Destroys this audio output.
Definition at line 151 of file qaudiooutput.cpp.
| int QAudioOutput::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 309 of file qaudiooutput.cpp.
| int QAudioOutput::bytesFree | ( | ) | const |
Returns the free space available in bytes in the audio buffer.
NOTE: returned value is only valid while in QAudio::ActiveState or QAudio::IdleState state, otherwise returns zero.
Definition at line 269 of file qaudiooutput.cpp.
| qint64 QAudioOutput::elapsedUSecs | ( | ) | const |
Returns the microseconds since start() was called, including time in Idle and Suspend states.
Definition at line 361 of file qaudiooutput.cpp.
| QAudio::Error QAudioOutput::error | ( | ) | const |
| QAudioFormat QAudioOutput::format | ( | ) | const |
Returns the QAudioFormat being used.
Definition at line 161 of file qaudiooutput.cpp.
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signal |
This signal is emitted when x ms of audio data has been processed the interval set by setNotifyInterval(x).
Referenced by QAudioOutput().
| int QAudioOutput::notifyInterval | ( | ) | const |
Returns the notify interval in milliseconds.
Definition at line 332 of file qaudiooutput.cpp.
| int QAudioOutput::periodSize | ( | ) | const |
Returns the period size in bytes.
Note: This is the recommended write size in bytes.
Definition at line 280 of file qaudiooutput.cpp.
| qint64 QAudioOutput::processedUSecs | ( | ) | const |
Returns the amount of audio data processed by the class since start() was called in microseconds.
Note: The amount of audio data played can be determined by subtracting the microseconds of audio data still in the systems audio buffer.
Definition at line 351 of file qaudiooutput.cpp.
| void QAudioOutput::reset | ( | ) |
Drops all audio data in the buffers, resets buffers to zero.
Definition at line 229 of file qaudiooutput.cpp.
| void QAudioOutput::resume | ( | ) |
Resumes processing audio data after a suspend().
Sets error() to QAudio::NoError. Sets state() to QAudio::ActiveState if you previously called start(QIODevice*). Sets state() to QAudio::IdleState if you previously called start(). emits stateChanged() signal.
Note: signal will always be emitted during execution of the resume() function.
Definition at line 257 of file qaudiooutput.cpp.
| void QAudioOutput::setBufferSize | ( | int | 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, calling bufferSize() anytime after start() will return the actual buffer size being used.
Definition at line 294 of file qaudiooutput.cpp.
| void QAudioOutput::setNotifyInterval | ( | int | ms | ) |
Sets the interval for notify() signal to be emitted.
This is based on the ms of audio data processed not on actual real-time. The minimum resolution of the timer is platform specific and values should be checked with notifyInterval() to confirm actual value being used.
Definition at line 323 of file qaudiooutput.cpp.
| void QAudioOutput::start | ( | QIODevice * | device | ) |
Uses the device as the QIODevice to transfer data.
Passing a QIODevice allows the data to be transferred without any extra code. All that is required is to open the QIODevice.
If able to successfully output audio data to the systems audio device the state() is set to QAudio::ActiveState, error() is set to QAudio::NoError and the stateChanged() signal is emitted.
If a problem occurs during this process the error() is set to QAudio::OpenError, state() is set to QAudio::StoppedState and stateChanged() signal is emitted.
In either case, the stateChanged() signal may be emitted either synchronously during execution of the start() function or asynchronously after start() has returned to the caller.
Definition at line 185 of file qaudiooutput.cpp.
| QIODevice * QAudioOutput::start | ( | ) |
Returns a pointer to the QIODevice being used to handle the data transfer.
This QIODevice can be used to write() audio data directly.
If able to access the systems audio device the state() is set to QAudio::IdleState, error() is set to QAudio::NoError and the stateChanged() signal is emitted.
If a problem occurs during this process the error() is set to QAudio::OpenError, state() is set to QAudio::StoppedState and stateChanged() signal is emitted.
In either case, the stateChanged() signal may be emitted either synchronously during execution of the start() function or asynchronously after start() has returned to the caller.
Definition at line 208 of file qaudiooutput.cpp.
| QAudio::State QAudioOutput::state | ( | ) | const |
Returns the state of audio processing.
Definition at line 379 of file qaudiooutput.cpp.
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signal |
This signal is emitted when the device state has changed.
This is the current state of the audio output.
Referenced by QAudioOutput().
| void QAudioOutput::stop | ( | ) |
Stops the audio output, detaching from the system resource.
Sets error() to QAudio::NoError, state() to QAudio::StoppedState and emit stateChanged() signal.
Definition at line 220 of file qaudiooutput.cpp.
| void QAudioOutput::suspend | ( | ) |
Stops processing audio data, preserving buffered audio data.
Sets error() to QAudio::NoError, state() to QAudio::SuspendedState and emit stateChanged() signal.
Definition at line 241 of file qaudiooutput.cpp.
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private |
Definition at line 104 of file qaudiooutput.h.
Referenced by bufferSize(), bytesFree(), elapsedUSecs(), error(), format(), notifyInterval(), periodSize(), processedUSecs(), QAudioOutput(), reset(), resume(), setBufferSize(), setNotifyInterval(), start(), state(), stop(), suspend(), and ~QAudioOutput().