Video signal processing method and device using secondary transform
A video signal processor is configured to obtain a secondary transform kernel for a current block based on an intra prediction mode of the current block to which a secondary transform is applied, to obtain a secondary inverse transformed block by performing a secondary inverse transform on a top-left specific region of the current block using the secondary transform kernel, wherein the secondary inverse transform is an inverse transform of the secondary transform, and the secondary transform is a low frequency non-separable transform, to obtain a residual block of the current block by performing a primary inverse transform on the secondary inverse transformed block, wherein one or more coefficients of the top-left specific region of the current block are derived in a preset scan order and the preset scan order is a 4×4 up-right diagonal scan order regardless of a size of the current block.
1. A video signal decoding device comprising a processor,
wherein the processor is configured to:
obtain a secondary transform matrix in a secondary transform matrix set based on an intra prediction mode of a current block,
obtain a secondary inverse transformed block by performing a secondary inverse transform on a specific region of the current block using the secondary transform matrix,
wherein the secondary inverse transform is an inverse transform of a secondary transform, and the secondary transform is a low frequency non-separable transform,
obtain a residual block of the current block by performing a primary inverse transform on the secondary inverse transformed block,
wherein one or more coefficients of the specific region of the current block are derived in a preset scan order,
wherein the preset scan order is a 4×4 up-right diagonal scan order regardless of a size of the current block.
2. The decoding device of claim 1 ,
wherein the processor is configured to:
determine whether the current block is a block to which the secondary transform is applied.
3. The decoding device of claim 2 ,
wherein whether the current block is the block to which the secondary transform is applied is determined by a parsing result of a syntax element,
wherein the syntax element is parsed when a width and a height of a coding block related to the current block are less than or equal to a maximum transform size.
4. The decoding device of claim 3 ,
wherein the secondary transform matrix is determined based on a value of the syntax element.
5. The decoding device of claim 3 ,
wherein when the width or the height of the coding block is greater than the maximum transform size, the coding block is split into a plurality of transform blocks.
6. The decoding device of claim 3 ,
wherein when at least one of the width and the height of the coding block is greater than the maximum transform size, the syntax element is not parsed.
7. The decoding device of claim 6 ,
wherein when the syntax element is not parsed, the current block is a block to which the secondary transform is not applied.
8. A video signal encoding device comprising a processor,
wherein the processor is configured to:
obtain a bitstream to be decoded by a decoder using a decoding method,
the decoding method comprising:
obtaining a secondary transform matrix in a secondary transform matrix set based on an intra prediction mode of a current block,
obtaining a secondary inverse transformed block by performing a secondary inverse transform on a specific region of the current block using the secondary transform matrix,
wherein the secondary inverse transform is an inverse transform of a secondary transform, and the secondary transform is a low frequency non-separable transform,
obtaining a residual block of the current block by performing a primary inverse transform on the secondary inverse transformed block,
wherein one or more coefficients of the specific region of the current block are derived in a preset scan order,
wherein the preset scan order is a 4×4 up-right diagonal scan order regardless of a size of the current block.
9. The encoding device of claim 8 ,
the decoding method further comprising:
determining whether the current block is a block to which the secondary transform is applied.
10. The encoding device of claim 9 ,
wherein whether the current block is the block to which the secondary transform is applied is determined by a parsing result of a syntax element,
wherein the syntax element is parsed when a width and a height of a coding block related to the current block are less than or equal to a maximum transform size.
11. The encoding device of claim 10 ,
wherein the secondary transform matrix is determined based on a value of the syntax element.
12. The encoding device of claim 10 ,
wherein when the width or the height of the coding block is greater than the maximum transform size, the coding block is split into a plurality of transform blocks.
13. The encoding device of claim 10 ,
wherein when at least one of the width and the height of the coding block is greater than the maximum transform size, the syntax element is not parsed.
14. The encoding device of claim 13 ,
wherein when the syntax element is not parsed, the current block is a block to which the secondary transform is not applied.
15. A method of obtaining a bitstream, the method comprising:
obtaining a secondary transform matrix in a secondary transform matrix set based on an intra prediction mode of a current block,
obtaining a secondary inverse transformed block by performing a secondary inverse transform on a specific region of the current block using the secondary transform matrix,
wherein the secondary inverse transform is an inverse transform of a secondary transform, and the secondary transform is a low frequency non-separable transform,
obtaining the bitstream including information related to obtain a residual block of the current block by performing a primary inverse transform on the secondary inverse transformed block,
wherein one or more coefficients of the specific region of the current block are derived in a preset scan order,
wherein the preset scan order is a 4×4 up-right diagonal scan order regardless of a size of the current block.
16. The method of claim 15 , further comprising:
determining whether the current block is a block to which the secondary transform is applied.
17. The method of claim 16 , further comprising:
obtaining a syntax element indicating whether the current block is the block to which the secondary transform is applied, when a width and a height of a coding block related to the current block are less than or equal to a maximum transform size.
18. The method of claim 17 ,
wherein the syntax element is used to determine the secondary transform matrix.
19. The method of claim 17 ,
wherein when the width or the height of the coding block is greater than the maximum transform size, the coding block is split into a plurality of transform blocks.