An inter prediction method, performed by a decoding apparatus, the method comprising: receiving picture order count information, wherein the picture order count information specifies picture order count differences for reference pictures; deriving picture order count values for the reference pictures based on the picture order count differences; constructing a reference picture list based on the picture order count values of the reference pictures; and performing an inter prediction on a current block based on the reference picture list, to derive a predicted sample of the current block, wherein a picture order count value of an i-th reference picture is derived based on a picture order count difference derived from the POC information, wherein for the reference pictures previous to the current picture in picture order count order, the picture order count difference is a difference between the picture order count value of the current picture and the picture order count value of the i-th reference picture when i is equal to 0, and the picture order count difference is a difference between the picture order count value of the i-th reference picture and the picture order count value of an (i-1)-th reference picture when i is greater than 0, wherein for the reference pictures subsequent to the current picture in picture order count order, the picture order count difference is a difference between the picture order count value of the current picture and the picture order count value of the i-th reference picture when i is equal to 0, and the picture order count difference is a difference between the picture order count value of the i-th reference picture and the picture order count value of the (i-1)-th reference picture when i is greater than 0. receiving picture order count information, wherein the picture order count information specifies picture order count differences for reference pictures; deriving picture order count values for the reference pictures based on the picture order count differences; constructing a reference picture list based on the picture order count values of the reference pictures; and performing an inter prediction on a current block based on the reference picture list, to derive a predicted sample of the current block, wherein a picture order count value of an i-th reference picture is derived based on a picture order count difference derived from the POC information, wherein for the reference pictures previous to the current picture in picture order count order, the picture order count difference is a difference between the picture order count value of the current picture and the picture order count value of the i-th reference picture when i is equal to 0, and the picture order count difference is a difference between the picture order count value of the i-th reference picture and the picture order count value of an (i-1)-th reference picture when i is greater than 0, wherein for the reference pictures subsequent to the current picture in picture order count order, the picture order count difference is a difference between the picture order count value of the current picture and the picture order count value of the i-th reference picture when i is equal to 0, and the picture order count difference is a difference between the picture order count value of the i-th reference picture and the picture order count value of the (i-1)-th reference picture when i is greater than 0.