Qt 4.8: Effect Class Reference

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# Effect Class Reference

(Phonon::Effect)

The Effect class is used to transform audio streams. More...

     #include <Phonon/Effect>

Inherits: QObject and MediaNode.

This class was introduced in Qt 4.4.

- List of all members, including inherited members

## Public Functions

| Effect ( const EffectDescription & description, QObject * parent = 0 )
EffectDescription | description () const
QVariant | parameterValue ( const EffectParameter & parameter ) const
QList<EffectParameter> | parameters () const
void | setParameterValue ( const EffectParameter & parameter, const QVariant & value )

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

### Additional Inherited Members

- 1 property inherited from QObject
- 1 public slot inherited from QObject
- 1 signal inherited from QObject
- 7 static public members inherited from QObject
- 8 protected functions inherited from QObject

## Detailed Description

The Effect class is used to transform audio streams.

An effect is a media node which is inserted into a path between a MediaObject and an audio output node, for instance, an AudioOutput. The Effect transforms the media stream on that path.

Examples may include simple modifiers, such as fading or pitch shifting, and more complex mathematical transformations. You can query the backend for available effects with BackendCapabilities::availableAudioEffects(). Note that the effects available is dependent on the underlying system (DirectDraw, GStreamer, or QuickTime).

In order to use an effect, insert it into the path as follows:

     Path path = Phonon::createPath(...);
     Effect *effect = new Effect(this);
     path.insertEffect(effect);

The effect will immediately begin applying it's transformations on the path. To stop it, remove the Effect from the path.

To create an effect, you use the EffectDescription class, which you get from availableAudioEffects(). We give a code example below.

         QList<Phonon::EffectDescription> effectDescriptions =
                 Phonon::BackendCapabilities::availableAudioEffects();
         Phonon::EffectDescription effectDescription = effectDescriptions.at(4);

         Phonon::Path path = Phonon::createPath(mediaObject, audioOutput);

         Phonon::Effect *effect = new Phonon::Effect(effectDescription);
         path.insertEffect(effect);

An effect can have one or more parameters, which let you alter how the effect works, for instance, by specifying the depth of a reverb effect. See the EffectParameter class description for details.

Phonon also provides EffectWidget, which lets the user modify the parameters of an effect an the fly; e.g., with combo boxes.

See also Phonon Module and EffectWidget.

## Member Function Documentation

### Effect::Effect ( const EffectDescription & description, QObject * parent = 0 )

Constructs a new effect object with the given description and parent object.

The EffectDescription object determines the type of the effect.

See also Phonon::BackendCapabilities::availableAudioEffects().

### EffectDescription Effect::description () const

Returns the description of this effect. This is the same description that was passed to the constructor.

### QVariant Effect::parameterValue ( const EffectParameter & parameter ) const

Returns the value of the given effect parameter. You can fetch the available parameters for an effect with parameters().

See also setParameterValue() and EffectParameter.

### QList<EffectParameter> Effect::parameters () const

Returns a list of parameters that this effect provides to control its behavior.

See also EffectParameter and EffectWidget.

### void Effect::setParameterValue ( const EffectParameter & parameter, const QVariant & value )

Sets the given effect parameter to the specified value.

Parameters for an effect are returned by parameters(). You can check which QVariant::Type an EffectParameter takes with the EffectParameter::type() function.

See also parameterValue() and EffectParameter.