About Auto-Mask

[QingTianNNN]

Thanks for your work，I would like to know what is the basis for Auto-Mask ? And, you mentioned in the paper that we use
the auto-mask (Ma) (Godardetal.2019)to remove stationary points on image pairs where the camera is not moving，I was wundering if Auto-Mask is only used when the camera is stationary?
Looking forward to your reply