In relation to an in-loop filtering procedure described in the present document, a virtual boundary is defined so as to further increase the subjective/objective visual quality of a restored picture and the in-loop filtering procedure can be applied across the virtual boundary. The virtual boundary can include, for example, a discontinuous edge such as a 360-degree image, a VR image, or picture in picture (PIP). For example, the virtual boundary can be at a predetermined appointed position, and the existence and/or the position thereof can be signaled. Embodiments of the present document present a method for efficiently signaling virtual boundary-related information.