title: iOS xcode4 AVQueuePlayer not playing sound
body: <p>I'm trying to play a .m4a sound file using AVQueuePlayer, on iPhone4, but there is no sound.
  If I try AudioServicesPlaySystemSound with the same file, all works okay.</p>
  
  <p>Here's the code.</p>
  
  <pre><code>(AVFoundation framework is installed.)
  
      #import &lt;AVFoundation/AVFoundation.h&gt; 
  
  -(void) play_sound_file: (NSString *) sound_file_m4a
  {
      printf("\n play_sound_file 1: '%s' ", [sound_file_m4a UTF8String] );
  
  
          AVPlayerItem *sound_file = [[AVPlayerItem alloc] initWithURL:[NSURL URLWithString:[[NSBundle mainBundle] pathForResource:sound_file_m4a ofType:@"m4a"]]]; 
          AVQueuePlayer *player = [AVQueuePlayer queuePlayerWithItems:[NSArray arrayWithObjects:sound_file, nil]];  
  
          [player play]; 
  
          return;
  }
  </code></pre>
  
  <p>LATEST CODE AS OF 8/28/12...........
  (Note: both sound files work with AudioServicesPlaySystemSound)</p>
  
  <pre><code>AVPlayerItem *sound_file1 = [[AVPlayerItem alloc] initWithURL:[NSURL fileURLWithPath:[[NSBundle mainBundle] pathForResource:[[NSString alloc] initWithFormat:@"Hold still"] ofType:@"m4a"]]]; 
  
  AVPlayerItem *sound_file2 = [[AVPlayerItem alloc] initWithURL:[NSURL fileURLWithPath:[[NSBundle mainBundle] pathForResource:[[NSString alloc] initWithFormat:@"Press go"] ofType:@"m4a"]]];     
  
  AVQueuePlayer *player = [AVQueuePlayer queuePlayerWithItems: [NSArray arrayWithObjects:sound_file1, sound_file2,  nil]];  
  
  [player play]; 
  </code></pre>