iOS (Objective-C) (AVFoundation): captureOutput:didOutputSampleBuffer:fromConnection is not called

[ph_user]

I have two files:

CameraViewController.h

#import <UIKit/UIKit.h>

#import <AVFoundation/AVFoundation.h>

NS_ASSUME_NONNULL_BEGIN

@interface CameraViewController : UIViewController <AVCaptureVideoDataOutputSampleBufferDelegate>

@end


NS_ASSUME_NONNULL_END

CameraViewController.m

#import "CameraViewController.h"
#import <AVFoundation/AVFoundation.h>
#import "AVCamRecorder.h"

@interface CameraViewController ()

@property (nonatomic) AVCaptureSession *captureSession;
@property (nonatomic) AVCaptureVideoDataOutput *videoDataOutput;
@property (nonatomic) AVCaptureVideoPreviewLayer *videoPreviewLayer;
@property (strong, nonatomic) UIView *previewView;

@end

@implementation CameraViewController

- (void)viewDidLoad {

  [super viewDidLoad];

  self.previewView = [[UIView alloc] initWithFrame:self.view.bounds];
  self.previewView.autoresizingMask = UIViewAutoresizingFlexibleWidth | UIViewAutoresizingFlexibleHeight;
  [self.previewView setBackgroundColor:[UIColor blackColor]];
  [self.view addSubview:self.previewView];
  [self.view bringSubviewToFront:self.previewView];

  self.captureSession = [AVCaptureSession new];
  self.captureSession.sessionPreset = AVCaptureSessionPresetHigh;

  // Create a VideoDataOutput and add it to the session
  self.videoDataOutput = [[AVCaptureVideoDataOutput alloc] init];

  dispatch_queue_t queue = dispatch_queue_create("myQueue", NULL);

  [self.videoDataOutput setSampleBufferDelegate:self queue:queue];

  // Specify the pixel format
  NSDictionary *rgbOutputSettings = [NSDictionary dictionaryWithObject:

                                     [NSNumber numberWithInt:kCMPixelFormat_32BGRA] forKey:(id)kCVPixelBufferPixelFormatTypeKey];
  [self.videoDataOutput setVideoSettings:rgbOutputSettings];

  [self.videoDataOutput setAlwaysDiscardsLateVideoFrames:YES];

  AVCaptureDevice *backCamera = [AVCaptureDevice defaultDeviceWithMediaType:AVMediaTypeVideo];

  if (!backCamera) {
      NSLog(@"Unable to access back camera!");
      return;
  }

  NSError *error;
  AVCaptureDeviceInput *input = [AVCaptureDeviceInput deviceInputWithDevice:backCamera
                                                                      error:&error];
  if (error) {
    NSLog(@"Error Unable to initialize back camera: %@", error.localizedDescription);

    return;
  }

  if ([self.captureSession canAddInput:input] && [self.captureSession canAddOutput:self.videoDataOutput]) {
      [self.captureSession addInput:input];

      [self.captureSession addOutput:self.videoDataOutput];

      [self setupLivePreview];
  }
}

- (void)captureOutput:(AVCaptureOutput *)captureOutput
didOutputSampleBuffer:(CMSampleBufferRef)sampleBuffer

       fromConnection:(AVCaptureConnection *)connection {

  NSLog(@"captureOutput");
}

- (void)setupLivePreview {
  self.videoPreviewLayer = [AVCaptureVideoPreviewLayer layerWithSession:self.captureSession];

  if (self.videoPreviewLayer) {
    self.videoPreviewLayer.videoGravity = AVLayerVideoGravityResizeAspectFill;

    self.videoPreviewLayer.connection.videoOrientation = AVCaptureVideoOrientationPortrait;

    [self.previewView.layer addSublayer:self.videoPreviewLayer];

    dispatch_queue_t globalQueue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_HIGH, 0);

    dispatch_async(globalQueue, ^{
      [self.captureSession startRunning];

      dispatch_async(dispatch_get_main_queue(), ^{
        self.videoPreviewLayer.frame = self.previewView.bounds;
      });
    });
  }
}

- (void)viewWillDisappear:(BOOL)animated {
    [super viewWillDisappear:animated];
    [self.captureSession stopRunning];
}

@end

Unfortunately, the method captureOutput:didOutputSampleBuffer:fromConnection is not called. What is wrong with my solution, have I missed something? I can see camera preview rendered in UIView so I am sure that everything except the captureOutput method works.