Prediction image generation device, moving image decoding device, moving image encoding device, and prediction image generation method

A prediction image generation device, the prediction image generation device using two prediction images to generate a prediction image and comprising:

• prediction image generation circuitry generating a first prediction image and a second prediction image;
• gradient image generation circuitry performing bidirectional prediction gradient change prediction processing by:
• using a difference value of the first prediction image in a horizontal direction and a first shift value to generate a first gradient image;
• using a difference value of the first prediction image in a vertical direction and the first shift value to generate a second gradient image;
• using a difference value of the second prediction image in the horizontal direction and the first shift value to generate a third gradient image;
• and
• using a difference value of the second prediction image in the vertical direction and the first shift value to generate a fourth gradient image;
• motion compensation correction value derivation circuitry that:
• uses the first prediction image, the second prediction image, the first gradient image, the second gradient image, the third gradient image, the fourth gradient image, a second shift value, and a third shift value to derive motion information;
• and
• uses the motion information, the first gradient image, the second gradient image, the third gradient image, and the fourth gradient image to derive a motion compensation correction value;
• and
• prediction image generation circuitry that uses the first prediction image, the second prediction image, and the motion compensation correction value to generate the prediction image,
• wherein:
• the first shift value is 6;
• the second shift value is 4;
• and
• the third shift value is 1.