How to make MLKIT not detect people in the background movement?

I could not find any function to count different people faces in 1 video real time. I want to detect head rotation but if there are 2 people, the getHeadEulerAngleY will detect the person in the background whose head is moving.

This is my detector option code:

        FaceDetectorOptions detectorOptions = new FaceDetectorOptions
            .Builder()
            .setPerformanceMode(FaceDetectorOptions.PERFORMANCE_MODE_FAST)
            .setLandmarkMode(FaceDetectorOptions.LANDMARK_MODE_ALL)
            .build();

Also, Is it possible to count how many people in live detection?

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