问AVPlayer音频无声

EN

 AVAudioSession *session = [AVAudioSession sharedInstance];
[session setCategory:AVAudioSessionCategoryPlayback error:nil];


UIView *myView = previewView;

videoController  = [[MPMoviePlayerViewController alloc]initWithContentURL:videoPlayUrl];
videoController.view.frame = myView.bounds;

[videoController.view setBounds:previewView.bounds];
videoController.moviePlayer.controlStyle = MPMovieControlStyleNone;
videoController.moviePlayer.scalingMode = MPMovieScalingModeFill;
videoController.moviePlayer.shouldAutoplay = NO;
videoController.view.clipsToBounds = YES;
[previewView.layer addSublayer:videoController.view.layer];

[videoController.moviePlayer prepareToPlay];