Android camera2 face detection

There is not enough info about camera2 face detection mechanism. I used the Camera2 sample from Google: https://github.com/android/camera-samples

I set face detection mode to FULL.

mPreviewRequestBuilder.set(CaptureRequest.STATISTICS_FACE_DETECT_MODE,
                                    CameraMetadata.STATISTICS_FACE_DETECT_MODE_FULL);

Also, I checked

STATISTICS_INFO_MAX_FACE_COUNT and STATISTICS_INFO_AVAILABLE_FACE_DETECT_MODES:

int max_count = characteristics.get(
CameraCharacteristics.STATISTICS_INFO_MAX_FACE_COUNT);
int modes [] = characteristics.get(
CameraCharacteristics.STATISTICS_INFO_AVAILABLE_FACE_DETECT_MODES);

Output: maxCount : 5 , modes : [0, 2]

My CaptureCallback:

 private CameraCaptureSession.CaptureCallback mCaptureCallback
 = new CameraCaptureSession.CaptureCallback() {

    private void process(CaptureResult result) {
                Integer mode = result.get(CaptureResult.STATISTICS_FACE_DETECT_MODE);
                Face [] faces = result.get(CaptureResult.STATISTICS_FACES);
                if(faces != null && mode != null)
                    Log.e("tag", "faces : " + faces.length + " , mode : " + mode ); 
    }

    @Override
    public void onCaptureProgressed(CameraCaptureSession session, CaptureRequest request,
                                    CaptureResult partialResult) {
        process(partialResult);
    }

    @Override
    public void onCaptureCompleted(CameraCaptureSession session, CaptureRequest request,
                                   TotalCaptureResult result) {
        process(result);
    }

Output: faces : 0 , mode : 2

 public static final int STATISTICS_FACE_DETECT_MODE_FULL = 2;

Faces length is constantly 0. Looks like it doesn't detect a face properly or I missed something.

I know the approach with FaceDetector. I just wanted to check how it works with the new camera2 Face.

You can check the ML-KIT from Google:

Detect faces with ML Kit on Android

And there is a related sample app: vision-quickstart

or if you are using the camera2 there is a working example: Camera2Vision