To provide an encoding method for reducing deterioration in encoding efficiency when encoding a video/an image by selecting one operation mode out of a number of operation modes. The encoding method includes: extracting one or more features from one or more reconstructed pixel groups; categorizing the one or more reconstructed pixel groups using the extracted one or more features and a first machine learning model; and performing an encoding process on a current block of image samples included in a current picture using a parameter set corresponding to a result of the categorizing, the parameter set being one of a plurality of predefined parameter sets.