Method for encoding/decoding image signal and device therefor

Abstract

A method for decoding an image according to the present invention comprises the steps of: partitioning a coding block into a plurality of sub-blocks in a horizontal direction or vertical direction; determining whether a second inverse transform is applied to the coding block; and when it is determined that the second inverse transform is applied to the coding block, applying the second inverse transform to at least one of the plurality of sub-blocks.

What is claimed is: 
     
         1 . A method of decoding a video, the method comprising:
 partitioning a coding block into a plurality of sub-blocks in a horizontal direction or in a vertical direction;   determining whether a second inverse transform is applied to the coding block or not; and   when it is determined that the second inverse transform is applied to the coding block, applying the second inverse transform to at least one among the plurality of sub-blocks,   wherein a determination of whether to apply the second inverse-transform is based on index information signaled via a bitstream, and   wherein the index information is signaled only when a size of at least one among the plurality of sub-blocks is equal to or greater than a threshold value.   
     
     
         2 . The method of  claim 1 , wherein when the size of at least one among the plurality of sub-blocks is less than the threshold value, decoding of the index information is omitted, and
 wherein when decoding of the information is omitted, a value of the index information is inferred to indicate that the second inverse transform is not applied.   
     
     
         3 . The method of  claim 1 , wherein the second inverse transform is performed based on an inverse transform matrix, and
 wherein the inverse transform matrix is determined based on an intra prediction mode of the coding block and the information.   
     
     
         4 . The method of  claim 3 , wherein, based on the intra prediction mode, an inverse transform matrix set is determined, and
 wherein, based on the index information, one among a plurality of inverse transform matrix candidates included in the determined inverse transform matrix set is selected.   
     
     
         5 . The method of  claim 4 , wherein an inverse transform matrix set selected when the intra prediction mode is a non-directional mode is different from an inverse transform matrix set selected when the intra prediction mode is a directional mode. 
     
     
         6 . The method of  claim 1 , wherein when a BDPCM scheme is applied to the coding block, decoding of the index information is omitted. 
     
     
         7 . A method of encoding a video, the method comprising:
 partitioning a coding block into a plurality of sub-blocks in a horizontal direction or in a vertical direction;   determining whether a second transform is applied to the coding block or not; and   when it is determined that the second transform is applied to the coding block, applying the second transform to at least one among the plurality of sub-blocks,   wherein whether to encode index information, specifying whether the second transform is performed, is determined by comparing a size of at least one among the plurality of sub-blocks with a threshold value.   
     
     
         8 . The method of  claim 7 , wherein the second transform is performed based on a transform matrix, and
 wherein the transform matrix is derived from a transform matrix set which is determined based on an intra prediction mode of the current block.   
     
     
         9 . The method of  claim 8 , wherein the index information is set to a value which specifying one among a plurality of transform matrix candidates included in the transform matrix set. 
     
     
         10 . The method of  claim 9 , wherein a non-separable inverse transform matrix set selected when the intra prediction mode is a non-directional mode is different from a non-separable inverse transform matrix set selected when the intra prediction mode is a directional mode. 
     
     
         11 . The method of  claim 7 , wherein when a BDPCM scheme is applied to the coding block, encoding of the index information is omitted.