ENCODER, DECODER, ENCODING METHOD, AND DECODING METHOD

原文（中国語）

A decoder includes circuitry and memory. Using the memory, the circuity, in a first operating mode, derives first motion vectors for a first block obtained by splitting a picture, using a first inter prediction scheme, and generates a prediction image corresponding to the first block, by referring to spatial gradients of luminance generated based on the first motion vectors. Using the memory, the circuitry, in a second operating mode, derives second motion vectors for a sub-block obtained by splitting a second block, using a second inter prediction scheme different from the first inter prediction scheme, the second block being obtained by splitting the picture, and generates a prediction image corresponding to the sub-block without referring to spatial gradients of luminance.