Why is my face detection code not working using CIDetector?

Question

I am trying to identify faces in the iOS app for the camera, but it does not work properly while it works in Camera.app . Note that:

• The first face is not found in my application, only in Camera.app.
• For a third person - an East Asian woman - Camera.app correctly draws a rectangle around her face, while my application draws a rectangle that extends well below her face.
• Obama's face is not found in my application, only in Camera.app.
• When the camera approaches Putin’s face, my application draws a rectangle over the right half of his face, cutting it in half, while Camera.app correctly draws a rectangle around his face.

Why is this happening?

My code is as follows. Do you see something wrong?

First, I create the video output as follows:

let videoOutput = AVCaptureVideoDataOutput()
videoOutput.videoSettings =
    [kCVPixelBufferPixelFormatTypeKey as AnyHashable: 
    Int(kCMPixelFormat_32BGRA)]

session.addOutput(videoOutput)

videoOutput.setSampleBufferDelegate(faceDetector, queue: faceDetectionQueue)

This is the delegate:

class FaceDetector: NSObject, AVCaptureVideoDataOutputSampleBufferDelegate {
  func captureOutput(_ captureOutput: AVCaptureOutput!,
                     didOutputSampleBuffer sampleBuffer: CMSampleBuffer!,
                     from connection: AVCaptureConnection!) {
    let imageBuffer = CMSampleBufferGetImageBuffer(sampleBuffer)!
    let features = FaceDetector.ciDetector.features(
        in: CIImage(cvPixelBuffer: imageBuffer))

    let faces = features.map { $0.bounds }
    let imageSize = CVImageBufferGetDisplaySize(imageBuffer)

    let faceBounds = faces.map { (face: CIFeature) -> CGRect in
        var ciBounds = face.bounds

        ciBounds = ciBounds.applying(
            CGAffineTransform(scaleX: 1/imageSize.width, y: -1/imageSize.height))
        CGRect(x: 0, y: 0, width: 1, height: -1).verifyContains(ciBounds)

        let bounds = ciBounds.applying(CGAffineTransform(translationX: 0, y: 1.0))
        CGRect(x: 0, y: 0, width: 1, height: 1).verifyContains(bounds)
        return bounds
    }
    DispatchQueue.main.sync {
      facesUpdated(faceBounds, imageSize)
    }
  }

  private static let ciDetector = CIDetector(ofType: CIDetectorTypeFace,
      context: nil,
      options: [CIDetectorAccuracy: CIDetectorAccuracyHigh])!
}

The faceUpdated () callback looks like this:

class PreviewView: UIView {
  private var faceRects = [UIView]()

  private static func makeFaceRect() -> UIView {
    let r = UIView()
    r.layer.borderWidth = FocusRect.borderWidth
    r.layer.borderColor = FocusRect.color.cgColor
    faceRects.append(r)
    addSubview(r)
    return r
  }

  private func removeAllFaceRects() {
    for faceRect in faceRects {
      verify(faceRect.superview == self)
      faceRect.removeFromSuperview()
    }
    faceRects.removeAll()
  }

  private func facesUpdated(_ faces: [CGRect], _ imageSize: CGSize) {
    removeAllFaceRects()

    let faceFrames = faces.map { (original: CGRect) -> CGRect in
        let face = original.applying(CGAffineTransform(scaleX: bounds.width, y: bounds.height))
        verify(self.bounds.contains(face))
        return face
    }

    for faceFrame in faceFrames {
      let faceRect = PreviewView.makeFaceRect()
      faceRect.frame = faceFrame
    }
  }
}

I also tried the following, but they did not help:

1. Set AVCaptureVideoDataOutput videoSettings to zero.
2. Explicitly setting the orientation of the CIDetector for the portrait. The phone in this test is portrait, so it should not matter.
3. Install and Uninstall CIDetectorTracking: true
4. Install and Uninstall CIDetectorAccuracy: CIDetectorAccuracyHigh
5. Trying to track only one face, looking only at the first detected function.
6. Replacing CVImageBufferGetDisplaySize () with CVImageBufferGetEncodedSize () - they are the same anyway, at 1440 x 1080.