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 di agonal 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:
determine whether a secondary transform was applied to a current block,
when the secondary transform was applied to the current block, obtain a secondary transform matrix in a secondary transform matrix set based on an intra prediction mode of the current block,
obtain a secondary inverse transformed block by performing a secondary inverse transform on coefficients of a specific region of the current block using the secondary transform matrix,
wherein the secondary inverse transform is an inverse transform of the 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 the coefficients of the specific region of the current block are derived from the specific region in a preset scan order, and
wherein the preset scan order is fixed as a 4×4 up-right diagonal scan order for a plurality of sizes of the current block.
2 . The video signal decoding device of claim 1 ,
wherein whether the secondary transform was applied to the current block 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.
3 . The video signal decoding device of claim 2 ,
wherein the secondary transform matrix is determined based on a value of the syntax element.
4 . The video signal decoding device of claim 2 ,
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.
5 . The video signal decoding device of claim 2 ,
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.
6 . The video signal decoding device of claim 5 ,
wherein when the syntax element is not parsed, the secondary transform is not applied to the current block.
7 . 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:
determining whether a secondary transform was applied to a current block;
when the secondary transform was applied to the current block, obtaining a secondary transform matrix in a secondary transform matrix set based on an intra prediction mode of the current block;
obtaining a secondary inverse transformed block by performing a secondary inverse transform on coefficients of a specific region of the current block using the secondary transform matrix,
wherein the secondary inverse transform is an inverse transform of the secondary transform, and the secondary transform is a low frequency non-separable transform; and
obtaining a residual block of the current block by performing a primary inverse transform on the secondary inverse transformed block,
wherein the coefficients of the specific region of the current block are derived from the specific region in a preset scan order, and
wherein the preset scan order is fixed as a 4×4 up-right diagonal scan order for a plurality of sizes of the current block.
8 . The video signal encoding device of claim 7 ,
wherein whether the secondary transform was applied to the current block 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.
9 . The video signal encoding device of claim 8 ,
wherein the secondary transform matrix is determined based on a value of the syntax element.
10 . The video signal encoding device of claim 8 ,
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.
11 . The video signal encoding device of claim 8 ,
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.
12 . The video signal encoding device of claim 11 ,
wherein when the syntax element is not parsed, the secondary transform is not applied to the current block.
13 . A method of obtaining a bitstream, the method comprising:
determining whether a secondary transform was applied to a current block;
when the secondary transform was applied to the current block, obtaining a secondary transform matrix in a secondary transform matrix set based on an intra prediction mode of the current block;
obtaining a secondary inverse transformed block by performing a secondary inverse transform on coefficients of a specific region of the current block using the secondary transform matrix;
wherein the secondary inverse transform is an inverse transform of the secondary transform, and the secondary transform is a low frequency non-separable transform,
obtaining the bitstream including information related to obtaining a residual block of the current block by performing a primary inverse transform on the secondary inverse transformed block,
wherein the coefficients of the specific region of the current block are derived from the specific region in a preset scan order,
wherein the preset scan order is fixed as a 4×4 up-right diagonal scan order for a plurality of sizes of the current block.
14 . The method of claim 13 , further comprising:
obtaining a syntax element indicating whether the secondary transform was applied to the current block, 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.
15 . The method of claim 14 , wherein the syntax element is used to determine the secondary transform matrix.
16 . The method of claim 14 ,
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.
17 . The method of claim 14 ,
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 obtained.
18 . The method of claim 17 ,
wherein when the syntax element is not obtained, the secondary transform is not applied to the current block.