Image processing method, and device for same

A method of encoding a video signal, comprising:

• generating residual samples of a current block;
• generating a first transform skip flag specifying whether a transform is applied to the residual samples of the current block based on a size of the current block being smaller than a predetermined first size;
• performing a transform to the residual samples of the current block based on one among transform kernel combinations to obtain transform coefficients of the current block, each transform kernel combination comprising a transform kernel in a horizontal direction and a transform kernel in a vertical direction;
• and
• generating an index specifying the one among a plurality of transform kernel combinations, based on the size of the current block being smaller than a predetermined second size and the first transform skip flag being 0,
• wherein the generating of the index further comprises checking whether a non-zero transform coefficient exists in the current block, and
• wherein the index is generated further based on a determination from the checking result that the non-zero transform coefficient exists in the current block.

An apparatus for decoding a video signal, comprising:

• a memory configured to store the video signal;
• and
• a processor coupled with the memory, wherein the processor is configured to:
• parse a first transform skip flag specifying whether a transform is applied to coefficients of a current block based on a size of the current block being smaller than a first predetermined size;
• obtain an index specifying one of a plurality of transform kernel combinations to be applied to the coefficients of the current block based on the size of the current block being smaller than a predetermined second size and the first transform skip flag being 0, each transform kernel combination comprising a transform kernel in a horizontal direction and a transform kernel in a vertical direction;
• and
• perform an inverse transform on the coefficients of the current block based on the transform kernel combination specified by the index to generate residual samples of the current block,
• wherein the obtaining of the index further comprises checking whether a non-zero transform coefficient exists in the current block, and
• wherein the index is obtained further based on a determination from the checking result that the non-zero transform coefficient exists in the current block.

An apparatus for encoding a video signal, comprising:

• a memory configured to store the video signal;
• and
• a processor coupled with the memory, wherein the processor is configured to:
• generate residual samples of a current block;
• generate a first transform skip flag specifying whether a transform is applied to the residual samples of the current block based on a size of the current block being smaller than a predetermined first size;
• perform a transform to the residual samples of the current block based on one among transform kernel combinations to obtain transform coefficients of the current block, each transform kernel combination comprising a transform kernel in a horizontal direction and a transform kernel in a vertical direction;
• and
• generate an index specifying the one among a plurality of transform kernel combinations, based on the size of the current block being smaller than a predetermined second size and the first transform skip flag being 0,
• wherein the generating of the index further comprises checking whether a non-zero transform coefficient exists in the current block, and
• wherein the index is generated further based on a determination from the checking result that the non-zero transform coefficient exists in the current block.