Patent ID: 7852945

Claim:
A video decoding method for 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, (A) a quantized orthogonal transform coefficient of a prediction error signal concerning the luminance component and first and second color difference components and (B) an index indicating (1) a reference image and (2) 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, (e) a second offset for the first color difference component, and (f) a third offset for the second color difference component; determining whether a decoding unit of the to-be-decoded block is a frame or a field; deriving, for the to-be-decoded block, the weighting factors and the offsets from the index; generating a prediction image by multiplying the luminance component and first and second color difference components of the reference image respectively by the weighting factors and adding the offsets, respectively, to results of the multiplying; generating a prediction error signal by subjecting the quantized orthogonal transform coefficient to inverse quantization and inverse orthogonal transform; and generating a decoded image signal by calculating a sum of the prediction error signal and the prediction image; wherein the weighting factors and the offsets derived from the index when the decoding unit is the field are identical to the weighting factors and the offsets derived from the index when the decoding unit is the frame, which has a value obtained by performing a right arithmetic shift of one bit on a value of the index when the decoding unit is the field.