Video signal processing method and device

Abstract

According to the present invention, there is provided a method of decoding an image, the method including: deriving an initial motion vector of a current block; determining a motion refinement vector of the current block; and determining a motion vector of the current block on the basis of the initial motion vector and the motion refinement vector. Herein, the initial motion vector is derived from any one of merge candidates included in a merge candidate list for the current block.

1 - 15 . (canceled) 
     
     
         16 . A method of decoding an image, the method comprising:
 generating a merge candidate list of a current block, the merge candidate list including a plurality of merge candidates;   determining an initial motion vector of the current block based on one among the plurality of merge candidates;   determining a motion refinement vector of the current block;   obtaining a motion vector of the current block by modifying the initial motion vector based on the motion refinement vector; and   performing inter prediction on the current block based on the motion vector,   wherein whether to modify the initial motion vector based on the motion refinement vector is adaptively determined based on a size of the current block and an inter prediction mode of the current block.   
     
     
         17 . The method of  claim 16 , wherein the size of the current block is representative of a product of a height and width of the current block. 
     
     
         18 . The method of  claim 17 , wherein the initial motion vector of the current block is modified based on the motion refinement vector in response to the inter prediction mode of the current block being a merge mode. 
     
     
         19 . The method of  claim 18 , wherein determining the motion refinement vector of the current block comprises:
 calculating costs between L0 blocks in an L0 reference picture and L1 blocks in an L1 reference picture, respectively; and   selecting a minimum cost among the costs.   
     
     
         20 . The method of  claim 19 , wherein the L0 blocks belongs to a predetermined search range in the L0 reference picture, and
 wherein the predetermined search range has a size pre-defined in a decoding apparatus.   
     
     
         21 . The method of  claim 20 , wherein an L0 component of the motion refinement vector is determined based on an offset between an L0 reference block indicated by an L0 component of the initial motion vector and an L0 block with the minimum cost. 
     
     
         22 . The method of  claim 21 , wherein the current block is divided into a plurality of sub-blocks, and
 wherein the motion refinement vector is determined in units of the sub-blocks.   
     
     
         23 . The method of  claim 16 , wherein the motion refinement vector is determined based on information on the motion refinement vector signaled from a bitstream,
 wherein the information on the motion refinement vector includes magnitude information indicating one of multiple magnitude candidates and direction information indicating one of multiple direction candidates.   
     
     
         24 . The method of  claim 23 , wherein a number of merge candidates available for the current block when it is determined to modify the initial motion vector is less than when it is determined not to modify the initial motion vector. 
     
     
         25 . The method of  claim 24 , wherein when it is determined to modify the initial motion vector, the number of the merge candidates available for the current block is 2. 
     
     
         26 . The method of  claim 24 , wherein a maximum value among the multiple magnitude candidates is varied according to motion vector precision information. 
     
     
         27 . The method of  claim 26 , wherein when the motion vector precision information indicates a fractional pel, the maximum value among the multiple magnitude candidates does not exceed a pre-defined value. 
     
     
         28 . A method of encoding an image, the method comprising:
 generating a merge candidate list of a current block, the merge candidate list including a plurality of merge candidates;   determining an initial motion vector of the current block based on one among the plurality of merge candidates;   determining a motion refinement vector of the current block;   obtaining a motion vector of the current block by modifying the initial motion vector based on the motion refinement vector; and   performing inter prediction on the current block based on the motion vector,   wherein whether to modify the initial motion vector based on the motion refinement vector is adaptively determined based on a size of the current block and an inter prediction mode of the current block.   
     
     
         29 . A transmission method of a video signal, comprising:
 generating a merge candidate list of a current block, the merge candidate list including a plurality of merge candidates;   determining an initial motion vector of the current block based on one among the plurality of merge candidates;   determining a motion refinement vector of the current block;   obtaining a motion vector of the current block by modifying the initial motion vector based on the motion refinement vector;   generating a bitstream by encoding the current block based on the motion vector; and   transmitting the video signal including the bitstream,   wherein whether to modify the initial motion vector based on the motion refinement vector is adaptively determined based on a size of the current block and an inter prediction mode of the current block.