Android Camera2 API Cropping Video

I'm trying to record a video using Android Camera2 API. I'm trying to crop video as a square by setting the SCALER_CROP_REGION in the request builder. I'm using the following code but it doesn't seem to work

mCameraDevice.createCaptureSession(surfaces, new CameraCaptureSession.StateCallback() {

    @Override
    public void onConfigured( CameraCaptureSession cameraCaptureSession) {
        mCaptureSession = cameraCaptureSession;
        try {
            mIsRecording = true;

            /////****** this where i'm setting the coping 
            mZoom = getZoomRect();
            mPreviewRequestBuilder.set(CaptureRequest.SCALER_CROP_REGION, mZoom);
            /////////******************
            mPreviewRequestBuilder.set(CaptureRequest.CONTROL_MODE, CameraMetadata.CONTROL_MODE_AUTO);
            HandlerThread thread = new HandlerThread("CameraPreview");
            thread.start();
            mCaptureSession.setRepeatingRequest(mPreviewRequestBuilder.build(), null, mBackgroundHandler);
        } catch (CameraAccessException e) {
            e.printStackTrace();
        }
    }

    @Override
    public void onConfigureFailed( CameraCaptureSession cameraCaptureSession) {
        Log.d(TAG, "onConfigureFailed");
    }}, mBackgroundHandler);

this is the code that should get the region to crop

public int zoom_level = 1;
public Rect mZoom = null;

public Rect getZoomRect(){
    try {
        CameraManager manager = (CameraManager) getApplicationContext().getSystemService(Context.CAMERA_SERVICE);
        CameraCharacteristics characteristics = manager.getCameraCharacteristics(mCameraId);
        float maxzoom = (characteristics.get(CameraCharacteristics.SCALER_AVAILABLE_MAX_DIGITAL_ZOOM))*10;
        Rect m = characteristics.get(CameraCharacteristics.SENSOR_INFO_ACTIVE_ARRAY_SIZE);

        int minW = (int) (m.width() / maxzoom);
        int minH = (int) (m.height() / maxzoom);
        int difW = m.width() - minW;
        int difH = m.height() - minH;
        int cropW = difW /100 *(int)zoom_level;
        int cropH = difH /100 *(int)zoom_level;
        cropW -= cropW & 3;
        cropH -= cropH & 3;
        mZoom = new Rect(cropW, cropH, m.width() - cropW, m.height() - cropH);
        ///// if recording video make it square 
        if (mIsRecording) {
            mZoom = new Rect(cropW, cropH, m.width() - cropW, m.width() - cropW);
        }


    } catch (CameraAccessException e) {
        Log.e(TAG, "can not access camera",e);
        throw new RuntimeException("can not access camera.", e);
    } catch (NullPointerException ex) {
        Log.e(TAG, "touch logic",ex);
    }

    return mZoom;
}

Assuming zoom_level=1, and SCALER_AVAILABLE_MAX_DIGITAL_ZOOM is 4, then you end up with

minW = m.width/40
minH = m.height/40
difW = m.width*39/40
difH = m.height*39/40
cropW = m.width*39/40/100 * 1
cropH = m.height*39/40/100 * 1
(floor cropW/cropH down to nearest multiple of 4)

if m.width = 3000, m.width=2000, then cropW = 28, cropH = 16.

so mZoom for recording is

Rect(28, 16, 2972, 2972).

Which isn't centered, and many devices only support center-zoom. But it is a square region at least.

The real issue is that you can't change the aspect ratio of an output by cropping - the aspect ratio is fixed by the resolution of the output Surface when you create a capture session. See these diagrams for how the cropping works.