QT audio playback upgrade (7)

1. install multimedia rely on 
# sudo apt install  libqt5multimedia5-plugins 

2. Create project code 
# mkdir qt
# cd qt

<1>.main.cpp
# emacs main.cpp
#include <QtCore/QCoreApplication>
#include <QtMultimedia/QMediaPlayer>
#include <QEventLoop>
#include "player.h"
int main(int argc, char *argv[]){
  QCoreApplication a(argc, argv);
  Player player;
  return a.exec();
}

<2>.player.h
# emacs player.h

#ifndef PLAYER_H
#define PLAYER_H

#include <QObject>
#include <QMediaPlayer>
class QMediaPlayer;

class Player : public QObject{
    Q_OBJECT
public:
    explicit Player(QObject *parent = nullptr);

signals:

public slots:
    void slotStatusChnaged(QMediaPlayer::State newState);
    void errorStatuschanged(QMediaPlayer::Error error );

private:
     QMediaPlayer * player ;
};

#endif // PLAYER_H


<3>.player.cpp
# emacs player.cpp

#include "player.h"
#include <QMediaPlayer>
#include <QCoreApplication>
#