avaudioplayer - AVAudioPlayer stops

Question

I'm trying to play a mp3 file with using AVAudioPlayer:

NSString *path = NSString stringWithFormat:@"%@/%@" , 
    [NSHomeDirectory() stringByAppendingPathComponent:@"Documents"];

NSURL* url = [NSURL fileURLWithPath:path];

AVAudioPlayer* player = [[AVAudioPlayer alloc] initWithContentsOfURL:url error:nil];
    [[AVAudioSession sharedInstance] setCategory: AVAudioSessionCategoryPlayback error: nil];


[player play];
NSLog(@"%f/%f", player.currentTime, player.duration);

However, the player stops around 478.558367 every time even though its duration is 1044.437506. Why does the player stop in the middle of the track?