Image data encoding/decoding method and apparatus

Abstract

A method for decoding a 360-degree image includes: receiving a bitstream obtained by encoding a 360-degree image; generating a prediction image by making reference to syntax information obtained from the received bitstream; combining the generated prediction image with a residual image obtained by dequantizing and inverse-transforming the bitstream to obtain a decoded image; and reconstructing the decoded image into a 360-degree image according to a projection format. Generating the prediction image includes: obtaining, from motion information in the syntax information, a motion vector candidate group including a motion vector of a block adjacent to a current block to be decoded; deriving a prediction motion vector from the motion vector candidate group based on selection information extracted from the motion information; and determining a prediction block for the current block to be decoded, using a final motion vector derived by adding the prediction motion vector to a differential motion vector extracted from the motion information.

What is claimed is: 
     
         1 . A method of decoding a 360-degree image, the method comprising:
 receiving a bitstream in which the 360-degree image is encoded;   generating a predicted image with reference to syntax information acquired from the received bitstream;   acquiring a decoded image by combining the generated predicted image with a residual image acquired by inversely quantizing and inversely transforming the bitstream; and   reconstructing the decoded image into the 360-degree image according to a projection format,   wherein the generating of the predicted image comprises:
 acquiring, from motion information included in the syntax information, a motion vector candidate group that includes a motion vector of a block adjacent to a current block to be decoded; 
 deriving, on the basis of selection information extracted from the motion information, a prediction motion vector from the motion vector candidate group; and 
 determining a prediction block of the current block to be decoded by using a final motion vector that is derived by adding the prediction motion vector and a difference motion vector extracted from the motion information. 
   
     
     
         2 . The method of  claim 1 , wherein the motion vector candidate group is, when blocks adjacent to the current block are different from a face to which the current block belongs, composed of only a motion vector for a block, among the adjacent blocks, which belongs to a face having image continuity with the face to which the current block belongs. 
     
     
         3 . The method of  claim 1 , wherein the block adjacent to the current blocks means a block adjacent to the current block in at least one direction selected from upper left, up, upper right, down, and lower left.