Video encoding/ decoding method and apparatus

Abstract

A video encoding method comprises selecting one combination, for each block of an input video signal, from a plurality of combinations each including a predictive parameter and at least one reference picture number determined in advance for the reference picture, generating a prediction picture signal in accordance with the reference picture number and predictive parameter of the selected combination, generating a predictive error signal representing an error between the input video signal and the prediction picture signal, and encoding the predictive error signal, information of the motion vector, and index information indicating the selected combination.

1 . A prediction image generating method for generating a prediction image by decoding encoded data obtained by subjecting a video image having luminance and two color differences to prediction encoding, comprising:
 receiving an input of encoded data obtained by encoding, for a to-be-decoded block, (A) information of a motion vector and (B) an index indicating (1) a combination comprising (a) a weighting factor for every luminance and two color differences and (b) an offset for every luminance and two color differences and (2) a reference image;   deriving the weighting factor and the offset from the index; and   generating a prediction image by multiplying the reference image by the weighting factor and adding the offset, based on the motion vector;   wherein two values of indexes corresponding to different reference images indicate an identical combination of the weighting factor and the offset, and a value obtained by arithmetic-shifting right one of the two values by one bit is identical to a value obtained by arithmetic-shifting right the other value by one bit.   
     
     
         2 . A prediction image generating apparatus of generating a prediction image by decoding encoded data obtained by subjecting a video image having luminance and two color differences to prediction encoding, comprising:
 a receiver configured to receive an input of encoded data obtained by encoding, for a to-be-decoded block, (A) information of a motion vector and (B) an index indicating (1) a combination comprising (a) a weighting factor for every luminance and two color differences and (b) an offset for every luminance and two color differences and (2) a reference image;   a deriving module configured to derive the weighting factor and the offset from the index; and   a first generator configured to generate a prediction image by multiplying the reference image by the weighting factor and adding the offset, based on the motion vector;   wherein two values of indexes corresponding to different reference images indicate an identical combination of the weighting factor and the offset, and a value obtained by arithmetic-shifting right one of the two values by one bit is identical to a value obtained by arithmetic-shifting right the other value by one bit.