A video decoding method according to the present invention may comprise: a step for determining whether to divide a current block into a plurality of sub-blocks; a step for determining an intra prediction mode for the current block; and a step for performing intra prediction for each sub-block on the basis of the intra prediction mode, when the current block is divided into the plurality of sub-blocks.

An intra-prediction method includes: determining, by an intra-prediction apparatus, a directional intra-prediction mode for a rectangular video coding block from an extended set of directional intra-prediction modes, wherein the extended set of directional intra-prediction modes includes extended directional intra-prediction modes and conventional directional intra-prediction modes and determining, by the intra-prediction apparatus, a plurality of available reference samples based on a direction of the directional intra-prediction mode. The method further includes: intra-predicting, by the intra-prediction apparatus, pixel values of pixels of the rectangular video coding block based on the plurality of available reference samples.

An intra-prediction method includes: determining, by an intra-prediction apparatus, a directional intra-prediction mode for a rectangular video coding block from an extended set of directional intra-prediction modes, wherein the extended set of directional intra-prediction modes includes extended directional intra-prediction modes and conventional directional intra-prediction modes and determining, by the intra-prediction apparatus, a plurality of available reference samples based on a direction of the directional intra-prediction mode. The method further includes: intra-predicting, by the intra-prediction apparatus, pixel values of pixels of the rectangular video coding block based on the plurality of available reference samples.

A method for decoding a video according to the present invention may comprise: determining a first prediction mode for a first sub-block in a current block and a second intra prediction mode for a second sub-block, performing a first prediction for the first sub-block based on the first intra prediction mode, performing a second prediction for the second sub-block based on the second intra prediction mode, and obtaining a prediction sample of the current block according to a result of the first prediction and the second prediction.

A method for decoding a video according to the present invention may comprise: determining a first prediction mode for a first sub-block in a current block and a second intra prediction mode for a second sub-block, performing a first prediction for the first sub-block based on the first intra prediction mode, performing a second prediction for the second sub-block based on the second intra prediction mode, and obtaining a prediction sample of the current block according to a result of the first prediction and the second prediction.

In an encoding apparatus or a decoding apparatus, an encoding method or decoding method combines various coding tools with intra sub partitioning mode in which a coding unit is split in multiple sub partitions. At least one embodiment particularly aims at the selection of primary transforms among a set of multiple transforms for video encoding or decoding of intra sub block partitions. At least one embodiment particularly aims at intra coding using Ma-trix-Based Intra Prediction mode combined with Intra Sub Partition mode. At least one embodiment particularly aims at intra coding using Multi-Reference-Line intra prediction mode combined with Intra Sub Partition mode.

An image encoding method for encoding an image includes: a prediction image generation step of generating a prediction image of a synthesis prediction by performing synthesis processing of synthesizing a prediction image of an in-screen block copy prediction and a prediction image of an intra prediction different from the in-screen block copy prediction, to an encoding-target block; and an encoding step of encoding a difference between the prediction image generated in the prediction image generation step and a pixel value of an image of the encoding-target block, the synthesis processing includes weighting processing performed to the prediction image of the in-screen block copy prediction and the prediction image of the intra prediction that is different from the in-screen block copy prediction, and a weighting parameter of the prediction image of the intra prediction in the weighting processing is determined by information of an adjacent block adjacent to the encoding-target block.

An image encoding method for encoding an image includes: a prediction image generation step of generating a prediction image of a synthesis prediction by performing synthesis processing of synthesizing a prediction image of an in-screen block copy prediction and a prediction image of an intra prediction different from the in-screen block copy prediction, to an encoding-target block; and an encoding step of encoding a difference between the prediction image generated in the prediction image generation step and a pixel value of an image of the encoding-target block, the synthesis processing includes weighting processing performed to the prediction image of the in-screen block copy prediction and the prediction image of the intra prediction that is different from the in-screen block copy prediction, and a weighting parameter of the prediction image of the intra prediction in the weighting processing is determined by information of an adjacent block adjacent to the encoding-target block.

An image decoding method performed by a decoding apparatus according to the present document comprises the steps of: obtaining a Block-based Delta Pulse Code Modulation (BDPCM) available flag indicating whether or not BDPCM is available for a chroma block and a luma block; obtaining BDPCM-related information for a current luma block and current chroma blocks on the basis of the BDPCM available flag; and generating reconstructed samples for the current luma block and the current chroma blocks on the basis of the BDPCM-related information.

An image decoding method performed by a decoding apparatus according to the present document comprises the steps of: obtaining a Block-based Delta Pulse Code Modulation (BDPCM) available flag indicating whether or not BDPCM is available for a chroma block and a luma block; obtaining BDPCM-related information for a current luma block and current chroma blocks on the basis of the BDPCM available flag; and generating reconstructed samples for the current luma block and the current chroma blocks on the basis of the BDPCM-related information.