Transform-based image coding method, and device for same

Abstract

An image decoding method according to the present document may comprise the steps of: receiving flag information, which indicates whether a scaling list is available while an LFNST is being performed, and an LFNST index and residual information for the current block; determining, on the basis of the flag information, the LFNST index, and the tree type of the current block, whether the scaling list is applicable to the current block; deriving transform coefficients for the current block from the residual information on the basis of the determination result; and applying the LFNST to the transform coefficients to derive corrected transform coefficients.

1 .- 13 . (canceled) 
     
     
         14 . A decoding apparatus for image decoding, the decoding apparatus comprising:
 a memory; and   at least one processor connected to the memory, the at least one processor configured to:   receive flag information related to whether a scaling list is available when performing an LFNST, an LFNST index for a current block, and residual information;   determine whether the scaling list is applied to the current block based on the flag information, the LFNST index, and a tree type of the current block;   derive transform coefficients for the current block from the residual information based on a determination result; and   derive modified transform coefficients by applying the LFNST to the transform coefficients,   wherein based on the tree type of the current block being a single tree and the current block being a luma component, the scaling list is not applied, and   wherein based on the tree type of the current block being the single tree and the current block being a chroma component, the scaling list is applied.   
     
     
         15 . The decoding apparatus of  claim 14 , wherein the LFNST is not applied to the chroma component of the current block. 
     
     
         16 . The decoding apparatus of  claim 14 , wherein when the flag information indicates that the scaling list is not available and the LFNST index is greater than 0, the scaling list is not applied to the luma component. 
     
     
         17 . The decoding apparatus of  claim 14 , wherein when the flag information indicates that the scaling list is not available and the LFNST index is greater than 0, if the tree type of the current block is a dual-tree chroma, the scaling list is not applied to the chroma component. 
     
     
         18 . The decoding apparatus of  claim 14 , wherein when the flag information indicates that the scaling list is not available and the LFNST index is greater than 0, if the tree type of the current block is a dual-tree luma, the scaling list is not applied to the luma component. 
     
     
         19 . The decoding apparatus of  claim 14 , wherein the current block comprises a transform block. 
     
     
         20 . An encoding apparatus for image encoding, the encoding apparatus comprising:
 a memory; and   at least one processor connected to the memory, the at least one processor configured to:   derive prediction samples for a current block;   derive residual samples for the current block based on the prediction samples;   derive transform coefficients for the current block from the residual samples based on a transformation process; and   quantize the transform coefficients based on a scaling list,   wherein whether the scaling list is applied to the current block is determined based on an LFNST is performed in the transformation process and a tree type of the current block,   wherein based on the tree type of the current block being a single tree and the current block being a luma component, the scaling list is not applied, and   wherein based on the tree type of the current block being the single tree and the current block being a chroma component, the scaling list is applied.   
     
     
         21 . The encoding apparatus of  claim 20 , further comprising:
 encoding and outputting flag information indicating whether the scaling list is available when the LFNST is performed.   
     
     
         22 . The encoding apparatus of  claim 20 , wherein the LFNST is not performed on the chroma component of the current block. 
     
     
         23 . The encoding apparatus of  claim 20 , wherein based on the tree type of the current block being a dual-tree chroma and the LFNST being performed on the current block, the scaling list is not applied to the chroma component. 
     
     
         24 . The encoding apparatus of  claim 20 , wherein based on the tree type of the current block being a dual-tree luma and the LFNST being performed on the current block, the scaling list is not applied to the luma component. 
     
     
         25 . The encoding apparatus of  claim 20 , wherein the current block comprises a transform block. 
     
     
         26 . A transmitting apparatus of data for an image, comprising:
 at least one processor configured to obtain a bitstream for the image,   wherein the bitstream is generated based on deriving prediction samples for a current block, deriving residual samples for the current block based on the prediction samples, deriving transform coefficients for the current block from the residual samples based on a transformation process, quantizing the transform coefficients based on a scaling list, and encoding residual information related to the quantizing the transform coefficients to generate the bitstream; and   a transmitter configured to transmit the data comprising the bitstream,   wherein whether the scaling list is applied to the current block is determined based on an LFNST is performed in the transformation process and a tree type of the current block,   wherein based on the tree type of the current block being a single tree and the current block being a luma component, the scaling list is not applied, and   wherein based on the tree type of the current block being the single tree and the current block being a chroma component, the scaling list is applied.