Disclosed herein are a video processing method, apparatus and storage medium using the resolution of a reference picture. Filtering is performed based on resolutions of reference pictures of blocks forming a boundary. The resolutions of the reference pictures may define filtering. Depending on whether the resolutions of the reference pictures are different from each other, one or more filter selection parameters for filtering may be determined or updated. Further, based on whether the resolutions of the reference pictures are different from each other, the boundary strength of the filter may be determined. Because filtering is defined using the resolutions of reference pictures, performance of encoding and/or decoding may be improved.