Provide an option to return un-mirrored depth image?

Hi all,
It seems the depth image read from libfreenect2 is a mirrored one... Is this a normal behavior?
The formula which used to calculate the coordinate in world coordination system:

``` C++
Point3d(
    (target.x - ir_params.cx) * depth / ir_params.fx,
    (target.y - ir_params.cy) * depth / ir_params.fy,
    depth
    )
```

is applied to the mirrored image, or a normal image?
