Patent ID: 8913665

Claim:
An image encoding method of encoding each block among blocks of pictures, the image encoding method comprising: deriving a bi-predictive candidate for motion vectors of a current block to be encoded, from a first motion vector of a first block included in a first picture, the first picture being different from a picture that includes the current block; adding the derived bi-predictive candidate to a list of candidates; selecting one bi-predictive candidate that includes a second motion vector and a third motion vector from the list of candidates; and encoding the current block using (i) the second motion vector and the third motion vector and (ii) a second reference picture and a third reference picture of the current block, the second reference picture and the third reference picture respectively corresponding to the second motion vector and the third motion vector, wherein the deriving includes: determining (i) whether each of the second reference picture and the third reference picture of the current block is a long-term reference picture or a short-term reference picture, and (ii) whether a first reference picture of the first block is a long-term reference picture or a short-term reference picture; deriving each of the second motion vector and the third motion vector so as to be the same as the first motion vector without scaling based on a temporal distance in the case of determining that (i) the corresponding one of the second reference picture and the third reference picture is a long-term reference picture and (ii) the first reference picture is a long-term reference picture; and deriving each of the second motion vector and the third motion vector from the first motion vector by scaling based on a temporal distance in the case of determining that (i) the corresponding one of the second reference picture and the third reference picture is a short-term reference picture and (ii) the first reference picture is a short-term reference picture.