I have tried some audio m4a files that is downloaded from itunes match, itunes store, and half the cases, the mediaplayer cannot play those m4a file. MP3 has no problem playing, only that m4a is the issue where some m4a can play whereas for those it can't, it just hang and wait.

I using this code in a javafx application class,

  Media mediaFile = new Media(audioFile.toURI().toString());

 MediaPlayer mediaPlayer = new MediaPlayer(mediaFile);

  mediaPlayer.play();