Create this code :
Qt Code: 
  1. class JMediaPlayer : public QWidget
  2. {
  3. Q_OBJECT
  4. public:
  5. 	JMediaPlayer(QWidget *parent = 0, bool initVideo = true);
  6. 	~JMediaPlayer();
  7. private:
  8. 	Phonon::MediaObject * mediaObject;
  9. 	Phonon::AudioOutput * audioOutput;
  10. 	Phonon::VideoWidget * videoWidget;
  11. 	Phonon::Path audioOutputPath;
  12.  
  13. 	Phonon::Effect * audiopanorama;
  14. 	Phonon::Effect * equalizer;
  15. ...
  16. ...
  17. ...
  18. ...
  19.  
  20. JMediaPlayer::JMediaPlayer(QWidget *parent, bool initVideo)
  21.  : QWidget(parent), video(initVideo)
  22. {	mediaObject = new Phonon::MediaObject(this);
  23. 	videoWidget = new Phonon::VideoWidget(this);
  24.  
  25. 	if (video) Phonon::createPath(mediaObject, videoWidget);
  26.  
  27. 	audioOutput = new Phonon::AudioOutput(Phonon::MusicCategory, this);
  28.      	audioOutputPath = Phonon::createPath(mediaObject, audioOutput);
  29. }
  30. void JMediaPlayer::audiopanoramaEnable( bool state )
  31. {
  32. 	if ( state ) {
  33. 		QList<Phonon::EffectDescription> availableEffects = Phonon::BackendCapabilities::availableAudioEffects();
  34. 		for (int i=0; i<availableEffects.size(); i++){
  35. 			if ( availableEffects[i].name() == "audiopanorama") {
  36. 				audioOutputPath.insertEffect(availableEffects[i]);
  37. 				audiopanorama = new Phonon::Effect(availableEffects[i]);
  38. 			}
  39. 		}
  40. 		QList<Phonon::Effect *> currEffects = audioOutputPath.effects();
  41. 		qDebug() << "effects in path - " << currEffects.size();
  42. 		foreach (Phonon::Effect * effect, currEffects){
  43. 			qDebug() << "name - " << effect->description().name();
  44. 		}
  45. 	}
  46. }
  47.  
  48. void JMediaPlayer::balanceLeft()
  49. {
  50. 	for (int k=0 ; k < audiopanorama->parameters().size() ; ++k) {
  51. 		Phonon::EffectParameter param = audiopanorama->parameters()[k];
  52. 		QVariant currentValue = audiopanorama->parameterValue(param);
  53. 		audiopanorama->setParameterValue(param, currentValue.toDouble() + 0.1);
  54. 	}
  55. }
  56.  
  57. void JMediaPlayer::balanceRight()
  58. {
  59. 	for (int k=0 ; k < audiopanorama->parameters().size() ; ++k) {
  60. 		Phonon::EffectParameter param = audiopanorama->parameters()[k];
  61. 		QVariant currentValue = audiopanorama->parameterValue(param);
  62. 		audiopanorama->setParameterValue(param, currentValue.toDouble() - 0.1);
  63. 	}
  64. }
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audioOutputPath.effects() (in 40) include effect AUDIOPANORAMA ... but no worked .
In '/usr/local/Trolltech/Qt-4.4.0/demo/mediaplayer' all work.
Why ?