使用前置摄像头记录用户在ios中的反应

Question

我正在使用此代码使用MPMoviePlayerController*mpc播放视频：

NSString *stringPath = [[NSBundle mainBundle]pathForResource:@"movie" ofType:@"mp4"];
                NSURL *url = [NSURL fileURLWithPath:stringPath];
                mpc = [[MPMoviePlayerController alloc]initWithContentURL:url];
                [mpc prepareToPlay];
                CGRect frame = self.view.frame;
                frame.origin = CGPointZero;

                mpc.view.frame = frame;
                mpc.allowsAirPlay         = NO;
                mpc.shouldAutoplay        = NO;
                mpc.movieSourceType       = MPMovieSourceTypeFile;
                mpc.scalingMode           = MPMovieScalingModeFill;
                mpc.controlStyle          = MPMovieControlStyleNone;
                mpc.view.autoresizingMask = UIViewAutoresizingFlexibleHeight | UIViewAutoresizingFlexibleWidth;

                dispatch_async(dispatch_get_main_queue(), ^{
                    [self.view addSubview:mpc.view];
                });
                [mpc play];

我想在播放视频的过程中记录用户使用前置摄像头的反应并保存。我怎么能这样做？

EDIT1： 这是我记录反应的代码。

- (void)recordReactions{
    if ([UIImagePickerController isSourceTypeAvailable:UIImagePickerControllerSourceTypeCamera]) {
        videoRecorder = [[UIImagePickerController alloc]init];
        videoRecorder.delegate = self;
        videoRecorder.sourceType = UIImagePickerControllerSourceTypeCamera;
        NSArray *sourceTypes = [UIImagePickerController availableMediaTypesForSourceType:videoRecorder.sourceType];
        NSLog(@"Available types for source as camera = %@", sourceTypes);


        videoRecorder.cameraDevice=UIImagePickerControllerCameraDeviceFront;
        videoRecorder.mediaTypes = [NSArray arrayWithObject:(NSString*)kUTTypeMovie];
        videoRecorder.videoQuality = UIImagePickerControllerQualityTypeLow;
        videoRecorder.videoMaximumDuration = 120;


        [self presentViewController:videoRecorder animated:YES completion:nil];
        [self presentViewController:videoRecorder animated:NO completion:nil];
        int64_t delayInSeconds = 2.0;
        dispatch_time_t popTime = dispatch_time(DISPATCH_TIME_NOW, delayInSeconds * NSEC_PER_SEC);
        dispatch_after(popTime, dispatch_get_main_queue(), ^(void){
            [videoRecorder startVideoCapture];
            [videoRecorder performSelector:@selector(stopVideoCapture) withObject:nil afterDelay:5];
            videoRecorder.showsCameraControls=YES;
        });
    }
    else {
        NSLog(@"Error");
    }
}

这会记录呈现视图的视频。但我想在播放主流视频时使用前置摄像头录制视频。