Patent ID: 9538196
Date: 2017-01-03
CPC Classifications: G06F,H04N

Claim:
1. An image coding method for coding a current block in a current picture, the method comprising: obtaining a reference motion vector of a reference block, the reference motion vector being used for deriving a motion vector of the current block to be coded; calculating a first parameter corresponding to a difference between a display order of a picture including a reference block and a display order of a reference picture of the reference block, wherein said reference block is motion-compensated using the reference motion vector, and said reference picture is referred to by the reference motion vector; calculating a second parameter corresponding to a difference between a display order of a current picture and a display order of the reference picture, wherein said current picture includes the current block; judging if (i) the reference motion vector of the reference block refers to a picture having a display order located after a display order of a picture including the reference block and (ii) the first parameter is a negative value within a predetermined range; deriving the motion vector of the current block by scaling the reference motion vector based on a predetermined negative value and the second parameter, when the first parameter is a negative value out of the predetermined range as a result of said judging, and by scaling the reference motion vector based on the first parameter and the second parameter, when the first parameter is a negative value within the predetermined range as a result of said judging; generating a motion compensated image of the current block using the derived motion vector and a reference picture corresponding to the derived motion vector; and coding a difference image between the current block and the motion compensated image of the current block.