Method and apparatus for performing artificial intelligence encoding and artificial intelligence decoding

An apparatus for performing artificial intelligence (AI) decoding on an image, the apparatus comprising:

• a memory storing one or more instructions;
• and
• at least one processor configured to execute the one or more instructions stored in the memory to:
• obtain AI data and image data, the image data generated as a result of first encoding of a first image, and the AI data related to AI downscaling of an original image to the first image or AI one-to-one preprocessing of the original image to the first image;
• obtain a second image corresponding to the first image by performing first decoding on the image data;
• obtain, based on the AI data, deep neural network (DNN) setting information for AI upscaling of the second image, from among a plurality of pieces of DNN setting information;
• and
• generate a third image by performing the AI upscaling on the second image via an upscaling DNN operating based on the obtained DNN setting information,
• wherein the plurality of pieces of DNN setting information are obtained via:
• first joint training of the upscaling DNN and a downscaling DNN used for the AI downscaling of the original image, and
• second joint training of a one-to-one preprocessing DNN used for the AI one-to-one preprocessing of the original image and the upscaling DNN, the second joint training being performed using DNN setting information for the AI upscaling obtained as a result of the first joint training.