An image decoding method including obtaining, from a bitstream, feature data of a preliminary optical flow and filtering information, the filtering information including at least one of type information of a filter or parameter information of a filter. The method including obtaining the preliminary optical flow by applying the feature data of the preliminary optical flow to a neural network based first decoder. The method including generating an optical flow by applying the preliminary optical flow to a filter corresponding to the filtering information. The method including generating a current reconstructed image by using previous data and the optical flow.