Qt 4.8: AudioOutput Class Reference

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# AudioOutput Class Reference

(Phonon::AudioOutput)

The AudioOutput class is used to send data to audio output devices. More...

     #include <Phonon/AudioOutput>

Inherits: QObject and MediaNode.

This class was introduced in Qt 4.4.

- List of all members, including inherited members

## Properties

muted : bool name : QString outputDevice : AudioOutputDevice | volume : qreal volumeDecibel : qreal

- 1 property inherited from QObject

## Public Functions

| AudioOutput ( Phonon::Category category, QObject * parent = 0 )
| AudioOutput ( QObject * parent = 0 )
Phonon::Category | category () const
bool | isMuted () const
QString | name () const
AudioOutputDevice | outputDevice () const
qreal | volume () const
qreal | volumeDecibel () const

- 29 public functions inherited from QObject
- 3 public functions inherited from Phonon::MediaNode

## Public Slots

void | setMuted ( bool mute )
void | setName ( const QString & newName )
bool | setOutputDevice ( const Phonon::AudioOutputDevice & newAudioOutputDevice )
void | setVolume ( qreal newVolume )
void | setVolumeDecibel ( qreal newVolumeDecibel )

- 1 public slot inherited from QObject

## Signals

void | mutedChanged ( bool muted )
void | outputDeviceChanged ( const Phonon::AudioOutputDevice & newAudioOutputDevice )
void | volumeChanged ( qreal newVolume )

- 1 signal inherited from QObject

### Additional Inherited Members

- 7 static public members inherited from QObject
- 8 protected functions inherited from QObject

## Detailed Description

The AudioOutput class is used to send data to audio output devices.

The AudioOutput class plays sound over a sound device. The audio output needs to be connected to a MediaObject using createPath(). To start playback, you call play() on the media object.

         Phonon::MediaObject *mediaObject = new Phonon::MediaObject(this);
         mediaObject->setCurrentSource(Phonon::MediaSource("/mymusic/barbiegirl.wav"));
         Phonon::AudioOutput *audioOutput =
             new Phonon::AudioOutput(Phonon::MusicCategory, this);
         Phonon::Path path = Phonon::createPath(mediaObject, audioOutput);

The class supports changing the volume(). It is also possible to mute the sound.

To find out what AudioOutputDevices are available for AudioOutput, you can call BackendCapabilities::availableAudioOutputDevices(). A default device is selected by the backend, but it is possible to set the device to be used with setOutputDevice(). The outputDeviceChanged() signal will be emitted if the device changes.

If an error occurs with the playback, for instance, if no valid output device is found, the media object will receive a stateChanged() signal with the ErrorState.

Note that the default values of properties are dependent on the backend.

See also Phonon::VolumeSlider, Music Player Example, BackendCapabilities, and Phonon Module.

## Property Documentation

### muted : bool

This property tells whether the output is muted.

Muting the output has the same effect as calling setVolume(0.0).

Access functions:

bool | isMuted () const
void | setMuted ( bool mute )

Notifier signal:

void | mutedChanged ( bool muted )

### name : QString

This is the name that appears in Mixer applications that control the volume of this output.

Access functions:

QString | name () const
void | setName ( const QString & newName )

### outputDevice : AudioOutputDevice

This property holds the (hardware) destination for the output.

The default device is determined by the Category and the global configuration for that category. Normally you don't need to override this setting - letting the user change the global configuration is the right choice. You can still override the device though, if you have good reasons to do so.

Access functions:

AudioOutputDevice | outputDevice () const
bool | setOutputDevice ( const Phonon::AudioOutputDevice & newAudioOutputDevice )

See also outputDeviceChanged().

### volume : qreal

This is the current loudness of the output.

(it is using Stevens' law to calculate the change in voltage internally).

Access functions:

qreal | volume () const
void | setVolume ( qreal newVolume )

Notifier signal:

void | volumeChanged ( qreal newVolume )

See also volumeDecibel.

### volumeDecibel : qreal

This is the current volume of the output in decibel.

0 dB means no change in volume, -6dB means an attenuation of the voltage to 50% and an attenuation of the power to 25%, -inf dB means silence.

Access functions:

qreal | volumeDecibel () const
void | setVolumeDecibel ( qreal newVolumeDecibel )

See also volume.

## Member Function Documentation

### AudioOutput::AudioOutput ( Phonon::Category category, QObject * parent = 0 )

Creates a new AudioOutput with the given parent that defines output to a physical device.

The category can be used by mixer applications to group volume controls of applications into categories. That makes it easier for the user to identify the programs. The category is also used for the default output device that is configured centrally. As an example: often users want to have the audio signal of a VoIP application go to their USB headset while all other sounds should go to the internal soundcard.

See also Phonon::categoryToString() and outputDevice.

### AudioOutput::AudioOutput ( QObject * parent = 0 )

Creates a new AudioOutput that defines output to the system default device with the {Phonon::Category::}{NoCategory} category

See also Phonon::categoryToString() and outputDevice.

### Phonon::Category AudioOutput::category () const

Returns the category of this output.

See also Phonon::AudioOutput::AudioOutput().

### void AudioOutput::mutedChanged ( bool muted )`[signal]`

This signal is emitted when the muted property has changed. The muted value passed by the signal indicates the state of the muted property. As this property can change by IPC (DBus) calls a UI element showing the muted property should listen to this signal.

### void AudioOutput::outputDeviceChanged ( const Phonon::AudioOutputDevice & newAudioOutputDevice )`[signal]`

This signal is emitted when the (hardware) device for the output has changed. newAudioOutputDevice is the new device.

The change can happen either through setOutputDevice or if the global configuration for the used category has changed.

See also outputDevice.

### void AudioOutput::volumeChanged ( qreal newVolume )`[signal]`

This signal is emitted whenever the volume has changed. As the volume can change without a call to setVolume (calls over dbus) this is important to keep a widget showing the current volume up to date.

newVolume is the new volume level.

See also setVolume() and volume().