thebo Thanks for the reply.
There is a reset view button in the UI, this never reflecting my lying-on-side position, it always assumes the left and right eyes on the same level.
If I turned my head so the focus is outside of the video, there is a "click to reset view" notice, if I click the remote then I get the view reflecting my lying-on-side position. However, this works only for videos that's splitted left/right. For videos splitted top/bottom, this notice never shows up.