phonon not work on raspberry

I write a basic Qt video player with Qt 4.8.6. In my labtop there is no problem but video did not play in raspberry. I tried omxplayer and it played video. But phonon did not work. I installed phonon, phonon-backend-gstreamer and phonon-backend-vlc packages on raspberry.

How can I play video on raspberry ?
I use raspbian.

my code:

Code:

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QString url = QApplication::applicationDirPath()+"/video.mp4";
    ui->videoPlayer->play(Phonon::MediaSource(url));

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