An image encoding/decoding method and apparatus are provided. An image decoding method performed by an image decoding apparatus may comprise determining prediction mode characteristic information based on a color format of a current block, determining a prediction mode type of a lower-layer block split from the current block based on the prediction mode characteristic information, obtaining the lower-layer block by splitting the current block based on the prediction mode type of the lower-layer block, and decoding the lower-layer block based on the prediction mode type of the lower-layer block. The prediction mode type of the lower-layer block comprises a first prediction mode type specifying that both an intra prediction mode and an inter prediction mode are available, a second prediction mode type specifying that only the intra prediction mode is available and a third prediction mode type specifying that only the inter prediction mode is available. Based on a first condition for the current block being satisfied, the prediction mode characteristic information has a first value, and the first condition comprises a case where a color format of the current block is a monochrome format or a 4:4:4 format. Based on the first condition for the current block being not satisfied, the prediction mode characteristic information has a second value or a third value based on at least one of a color format, split mode or size of the current block.

An image encoding/decoding method and apparatus are provided. An image decoding method performed by an image decoding apparatus may comprise determining prediction mode characteristic information based on a color format of a current block, determining a prediction mode type of a lower-layer block split from the current block based on the prediction mode characteristic information, obtaining the lower-layer block by splitting the current block based on the prediction mode type of the lower-layer block, and decoding the lower-layer block based on the prediction mode type of the lower-layer block. The prediction mode type of the lower-layer block comprises a first prediction mode type specifying that both an intra prediction mode and an inter prediction mode are available, a second prediction mode type specifying that only the intra prediction mode is available and a third prediction mode type specifying that only the inter prediction mode is available. Based on a first condition for the current block being satisfied, the prediction mode characteristic information has a first value, and the first condition comprises a case where a color format of the current block is a monochrome format or a 4:4:4 format. Based on the first condition for the current block being not satisfied, the prediction mode characteristic information has a second value or a third value based on at least one of a color format, split mode or size of the current block.

A method for intra prediction of a video block, comprising: padding of luminance reference samples rows for a chroma component of a current block vertically aligned with a largest coding unit (LCU) boundary; applying a filter F to reconstructed luma samples of a luma component of the current block and to luma samples in selected position neighboring to the current block, to obtain filtered reconstructed luma samples, wherein a shape of the F is same for blocks in the LCU; obtaining linear model coefficients, based on the filtered reconstructed luma samples; and performing cross-component prediction based on the obtained linear model coefficients and the filtered reconstructed luma samples of the current block, to obtain a prediction value of the chroma component of the current block.

A method for intra prediction of a video block, comprising: padding of luminance reference samples rows for a chroma component of a current block vertically aligned with a largest coding unit (LCU) boundary; applying a filter F to reconstructed luma samples of a luma component of the current block and to luma samples in selected position neighboring to the current block, to obtain filtered reconstructed luma samples, wherein a shape of the F is same for blocks in the LCU; obtaining linear model coefficients, based on the filtered reconstructed luma samples; and performing cross-component prediction based on the obtained linear model coefficients and the filtered reconstructed luma samples of the current block, to obtain a prediction value of the chroma component of the current block.

A method for decoding a data stream representative of an image split into blocks. For a current block of the image, an item of information indicating a coding mode among a first and a second coding mode of the current block is decoded from the data stream and the current block is decoded depending on this information. When the coding mode of the current block corresponds to the second coding mode, the current block is reconstructed from a prediction obtained, for each pixel, from another previously decoded pixel belonging to the current block or to a previously decoded block of the image, and from a decoded residue associated with the pixel. At least one processing method is applied to the reconstructed current block for at least one pixel of the current block depending on the coding mode of the current block and/or the coding mode of the neighbouring blocks.

A method for decoding a data stream representative of an image split into blocks. For a current block of the image, an item of information indicating a coding mode among a first and a second coding mode of the current block is decoded from the data stream and the current block is decoded depending on this information. When the coding mode of the current block corresponds to the second coding mode, the current block is reconstructed from a prediction obtained, for each pixel, from another previously decoded pixel belonging to the current block or to a previously decoded block of the image, and from a decoded residue associated with the pixel. At least one processing method is applied to the reconstructed current block for at least one pixel of the current block depending on the coding mode of the current block and/or the coding mode of the neighbouring blocks.

A picture may be divided into sub-pictures/slices/tiles. For example, the picture may be divided into sub-picture(s), and subpicture-related information may be used for coding. The sub-picture-related information may be generated by an encoding device and transmitted to a decoding device. According to embodiments of the present document, sub-picture-related information can be efficiently signaled.

A picture may be divided into sub-pictures/slices/tiles. For example, the picture may be divided into sub-picture(s), and subpicture-related information may be used for coding. The sub-picture-related information may be generated by an encoding device and transmitted to a decoding device. According to embodiments of the present document, sub-picture-related information can be efficiently signaled.

The invention relates to a method and a device for decoding an image by means of a partition unit comprising an additional region. The method of decoding an image by means of a partition unit comprising an additional region comprises the steps of: partitioning, by reference to a syntax element acquired from a received bit stream, an encoded image, which is included in the bitstream, in at least one partition unit; define an additional region for at least one partition unit; and decoding the encoded image based on the partition unit for which the additional region is defined. The invention improves the image coding efficiency.

The invention relates to a method and a device for decoding an image by means of a partition unit comprising an additional region. The method of decoding an image by means of a partition unit comprising an additional region comprises the steps of: partitioning, by reference to a syntax element acquired from a received bit stream, an encoded image, which is included in the bitstream, in at least one partition unit; define an additional region for at least one partition unit; and decoding the encoded image based on the partition unit for which the additional region is defined. The invention improves the image coding efficiency.