I've some problems making this work. I wanna use playlist to play audio files. here is my code:

```
playlist = QMediaPlaylist()
url = QUrl.fromLocalFile("/home/user/Downloads/ss.mp3")
playlist.addMedia(QMediaContent(url))

player.setPlaylist(playlist)
player.playlist().setCurrentIndex(0)
player.play()

```

The problem is that when I feed the file as unique media source (player.serMedia()) it works, but when I run the code above, the music doesn't play!

What's the problem here?