Video coding method and apparatus based on conversion

Abstract

To provide a method and a device to increase the efficiency of image coding.SOLUTION: An image decoding method comprises: a residual coding step for parsing residual information received in a residual coding level and arranging transform coefficients for a current block according to a predetermined scanning order; a step for deriving residual samples by applying at least one of LFNST or MTS to the transform coefficients; and a step for generating a reconstructed picture on the basis of the residual samples. The LFNST is performed on the basis of an LFNST index indicating an LFNST kernel, the MTS is performed on the basis of an MTS index indicating an MTS kernel, the LFNST index and the MTS index are signaled in a coding unit level, and the MTS index is signaled immediately after the signaling of the LFNST index.SELECTED DRAWING: Figure 19

Claims

1. A decoding device relating to video decoding, Memory and The system comprises at least one processor connected to the memory, The aforementioned at least one processor is Obtain residual information at the residual coding level, Based on the aforementioned residual information, a conversion coefficient for the current block is derived. Residual samples are derived by applying at least one of the LFNST kernel derived from the LFNST (low frequency non-separable transform) index or the linear transformation kernel derived from the MTS (multiple transform selection) index to the transformation coefficients. It is configured to generate a restored picture based on the said residual sample, The LFNST index and the MTS index are obtained at the coding unit level. The MTS index is obtained immediately after the LFNST index is obtained. A decoding device in which the MTS index is obtained based on the fact that at least the value of the LFNST index is equal to 0.

2. The decoding apparatus according to claim 1, wherein, if the tree type of the current block is a single-tree type, the LFNST index is parsed after residual coding has been performed on the luma block and chroma block of the current block.

3. The decoding apparatus according to claim 1, wherein, if the tree type of the current block is a dual tree type and a chroma component is coded, the LFNST index is parsed after residual coding is performed on the Cb and Cr components of the chroma block.

4. The decoding apparatus according to claim 1, wherein, if the current block is divided into a plurality of subpartition blocks, the LFNST index is parsed after residual coding is performed on the plurality of subpartition blocks.

5. The decoding apparatus according to claim 4, wherein, when the current block is divided into a plurality of subpartition blocks, the LFNST index is parsed regardless of whether the conversion coefficient exists in the region excluding the DC position of each of the plurality of subpartition blocks.

6. The execution of the aforementioned residual coding is To derive a first variable related to whether the conversion coefficient exists in the region excluding the DC position of the current block, This includes deriving a second variable related to whether the conversion coefficient exists in a second region excluding the first region at the upper left of the current block or the subpartition block from which the current block is divided, The decoding device according to claim 4, wherein the LFNST index is parsed if the conversion coefficient exists in the region excluding the DC position and the conversion coefficient does not exist in the second region.

7. The execution of residual coding includes deriving a third variable relating to whether the conversion coefficient exists in the region excluding the upper left 16x16 region of the current block, The decoding device according to claim 1, wherein if the conversion coefficient does not exist in the region excluding the 16x16 region, the MTS index is parsed.

8. In an encoding device relating to video encoding, Memory and The system comprises at least one processor connected to the memory, The aforementioned at least one processor is Currently, we derive the predicted sample for the block. Based on the predicted sample, a residual sample is derived for the current block. A conversion coefficient derivation operation is performed to derive conversion coefficients for the current block by applying at least one of the LFNST (low frequency non-separable transform) kernel or a linear transformation kernel to the residual sample, Encode at least one of the LFNST index associated with the LFNST kernel or the MTS index associated with the primary transformation kernel, Video information, The LFNST index and the MTS index are signaled at the coding unit level. The MTS index is signaled immediately after the LFNST index is signaled, and An encoding device configured to signal and output the MTS index based on at least the value of the LFNST index being equal to 0.

9. The encoding device according to claim 8, wherein, when the tree type of the current block is a single-tree type, the LFNST index is encoded after the conversion coefficient derivation operation for the luma block and chroma block of the current block has been performed.

10. The encoding device according to claim 8, wherein, when the tree type of the current block is a dual tree type and a chroma component is coded, the LFNST index is encoded after the conversion coefficient derivation operation for the Cb and Cr components of the chroma block is performed.

11. The encoding device according to claim 8, wherein, when the current block is divided into a plurality of subpartition blocks, the LFNST index is encoded after the conversion coefficient derivation operation is performed for the plurality of subpartition blocks.

12. The encoding device according to claim 11, wherein when the current block is divided into a plurality of subpartition blocks, the LFNST index is encoded regardless of whether the conversion coefficient exists in the region excluding each DC position of the subpartition block.

13. The execution of the conversion coefficient derivation operation is: To derive a first variable related to whether the conversion coefficient exists in the region excluding the DC position of the current block, This includes deriving a second variable related to whether the conversion coefficient exists in a second region excluding the first region at the upper left of the current block or the subpartition block from which the current block is divided, The encoding device according to claim 11, wherein the conversion coefficient exists in the region excluding the DC position and the conversion coefficient does not exist in the second region, and the LFNST index is encoded.

14. The execution of the conversion coefficient derivation operation includes deriving a third variable relating to whether the conversion coefficient exists in the region excluding the upper left 16x16 region of the current block, The encoding device according to claim 8, wherein if the conversion coefficient does not exist in the region excluding the 16x16 region, the MTS index is encoded.

15. In a device for transmitting video data, At least one processor configured to acquire a bitstream, wherein the bitstream is The current step is to derive a predicted sample for the block, The steps include: deriving a residual sample for the current block based on the predicted sample; The steps include performing a transformation coefficient derivation operation to derive transformation coefficients for the current block by applying at least one of an LFNST (low frequency non-separable transform) kernel or a linear transformation kernel to the residual sample, A step of encoding at least one of the LFNST index associated with the LFNST kernel or the MTS index associated with the primary transformation kernel, Video information, The LFNST index and the MTS index are signaled at the coding unit level. The MTS index is signaled immediately after the LFNST index is signaled, and A processor generated by the steps of: configuring and outputting such that the MTS index is signaled based on at least the value of the LFNST index being equal to 0; A device comprising: a transmitting unit configured to transmit the data including the bitstream of the video information.

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