I figured out my self : This code for QT : 1) libvlc_event_attach( em, libvlc_MediaPlayerPositionChanged,callback, this, &_vlcexcep ); 2) void MainWindow::callback( const libvlc_event_t *ev, void *param ) { MainWindow* self = reinterpret_cast<MainWindow*>( param ); switch(ev->type){ case libvlc_...