Video signal processing method and apparatus using multiple transform kernels

1. A video signal decoding apparatus, comprising a processor, wherein the processor is configured to: obtain at least one transform block for a residual signal of a current block from a video signal bitstream, wherein the transform block comprises a plurality of transform coefficients that are two-dimensionally arranged, determine, on the basis of length information of a first side of the transform block, a horizontal transform kernel for horizontal transformation of the transform block, regardless of a length of a second side of the transform block, which is orthogonal to the first side, determine, on the basis of length information of the second side, a vertical transform kernel for vertical transformation of the transform block, regardless of a length of the first side, obtain the residual signal of the current block by performing, on the transform block, inverse transformation using the horizontal transform kernel and the vertical transform kernel, and reconstruct the current block on the basis of the obtained residual signal, wherein the horizontal transform kernel and the vertical transform kernel are determined, respectively, among a plurality of transform kernels determined based on a basis function wherein the horizontal transform kernel and the vertical transform kernel are determined independently of each other according to the length of the first side corresponding to a horizontal direction of the transform block and the length of the second side corresponding to a vertical direction of the transform block, respectively, wherein the length of the first side is a width of the transform block, and the length of the second side is a height of the transform block, wherein, if the length of the second side has a value outside a preconfigured range, and the length of the first side has a value within the preconfigured range, the vertical transform kernel is a first transform kernel, and the horizontal transform kernel is a second transform kernel, wherein the first transform kernel is a discrete cosine transform type 2 (DCT-2)-based transform kernel, and the second transform kernel is not the DCT-2-based transform kernel.

2. The apparatus of claim 1 , wherein the second transform kernel is one of a discrete sine transform type 7 (DST-7)-based transform kernel or a discrete cosine transform type 8 (DCT-8)-based transform kernel.

3. The apparatus of claim 1 , wherein the first transform kernel is an available transform kernel indicated by an index having a smallest value from among indices indicating respective multiple available transform kernels.

4. A video signal encoding apparatus, comprising a processor, wherein the processor is configured to: obtain a bitstream to be decoded by a decoder using a decoding method, wherein the decoding method comprising: obtaining at least one transform block for a residual signal of a current block from a video signal bitstream, wherein the transform block comprises a plurality of transform coefficients that are two-dimensionally arranged, determining, on the basis of length information of a first side of the transform block, a horizontal transform kernel for horizontal transformation of the transform block, regardless of a length of a second side of the transform block, which is orthogonal to the first side, determining, on the basis of length information of the second side, a vertical transform kernel for vertical transformation of the transform block, regardless of a length of the first side, obtaining the residual signal of the current block by performing, on the transform block, inverse transformation using the horizontal transform kernel and the vertical transform kernel, and reconstructing the current block on the basis of the obtained residual signal, wherein the horizontal transform kernel and the vertical transform kernel are determined, respectively, among a plurality of transform kernels determined based on a basis function, wherein the horizontal transform kernel and the vertical transform kernel are determined independently of each other according to the length of the first side corresponding to a horizontal direction of the transform block and the length of the second side corresponding to a vertical direction of the transform block, respectively, wherein the length of the first side is a width of the transform block, and the length of the second side is a height of the transform block, wherein, if the length of the second side has a value outside a preconfigured range, and the length of the first side has a value within the preconfigured range, the vertical transform kernel is a first transform kernel, and the horizontal transform kernel is a second transform kernel, wherein the first transform kernel is a discrete cosine transform type 2 (DCT-2)-based transform kernel, and the second transform kernel is not the DCT-2-based transform.

5. The apparatus of claim 4 , wherein the second transform kernel is one of a discrete sine transform type 7 (DST-7)-based transform kernel or a discrete cosine transform type 8 (DCT-8)-based transform kernel.

6. The apparatus of claim 4 , wherein the first transform kernel is an available transform kernel indicated by an index having a smallest value from among indices indicating respective multiple available transform kernels.

7. A non-transitory computer-readable medium storing a bitstream, the bitstream being decoded by a decoding method, wherein the decoding method, comprising: obtaining at least one transform block for a residual signal of a current block from a video signal bitstream, wherein the transform block comprises a plurality of transform coefficients that are two-dimensionally arranged, determining, on the basis of length information of a first side of the transform block, a horizontal transform kernel for horizontal transformation of the transform block, regardless of a length of a second side of the transform block, which is orthogonal to the first side, determining, on the basis of length information of the second side, a vertical transform kernel for vertical transformation of the transform block, regardless of a length of the first side, obtaining the residual signal of the current block by performing, on the transform block, inverse transformation using the horizontal transform kernel and the vertical transform kernel, and reconstructing the current block on the basis of the obtained residual signal, wherein the horizontal transform kernel and the vertical transform kernel are determined, respectively, among a plurality of transform kernels determined based on a basis function, wherein the horizontal transform kernel and the vertical transform kernel are determined independently of each other according to the length of the first side corresponding to a horizontal direction of the transform block and the length of the second side corresponding to a vertical direction of the transform block, respectively, wherein the length of the first side is a width of the transform block, and the length of the second side is a height of the transform block, wherein, if the length of the second side has a value outside a preconfigured range, and the length of the first side has a value within the preconfigured range, the vertical transform kernel is a first transform kernel, and the horizontal transform kernel is a second transform kernel, wherein the first transform kernel is a discrete cosine transform type 2 (DCT-2)-based transform kernel, and the second transform kernel is not the DCT-2-based transform kernel.

8. The non-transitory computer-readable medium storing a bitstream of claim 7 ,

wherein the second transform kernel is one of a discrete sine transform type 7 (DST-7)-based transform kernel or a discrete cosine transform type 8 (DCT-8)-based transform kernel.

9. The non-transitory computer-readable medium storing a bitstream of claim 7 ,

wherein the first transform kernel is an available transform kernel indicated by an index having a smallest value from among indices indicating respective multiple available transform kernels.