Patent ID: 7864853

Claim:
A prediction image generation method for generating a prediction image by decoding encoded data obtained by subjecting a video image to prediction encoding, the video image having a luminance component and first and second color difference components, the method comprising: receiving an input of encoded data obtained by encoding, for a to-be-decoded block, (1) an index indicating (A) a reference image and (B) a combination comprising (a) a first weighting factor for the luminance component, (b) a second weighting factor for the first color difference component, (c) a third weighting factor for the second color difference component, (d) a first offset for the luminance component, (r) a second offset for the first color difference component, and (f) a third offset for the second color difference component, and (2) information of a motion vector; selecting either a frame unit or a field unit as a decoding unit; deriving, for the to-be-decoded block, the reference image, the weighting factors and the offsets from the index based on the decoding unit; and generating a prediction image by multiplying the luminance component and the first and second color difference components of the reference image by the weighting factors, respectively, and adding the offsets, respectively, to results of the multiplying, based on the motion vector, wherein each value of the index indicates respective different combinations of the weighting factors and the offsets when the decoding unit is a frame unit, and two values of the index corresponding to the different reference images indicate an identical combination of the weighting factors and the offsets when the decoding unit is a field unit.