The present specification discloses a method of decoding an image. The method includes performing dequantization on a current block to obtain a transform coefficient of the current block; performing at least one inverse transform of primary inverse transform and secondary inverse transform on the transform coefficient of the current block to obtain a residual block of the current block; and adding the residual block of the current block and a prediction block of the current block to obtain a reconstructed block of the current block, wherein the secondary inverse transform is performed only when the current block is in an intra prediction mode.

A method for video decoding in a decoder includes deriving for a block encoded under an intra prediction mode, a candidate list that includes a first candidate intra prediction mode value (Mode.sub.1) that corresponds to an intra prediction mode of a neighbor block that neighbors the encoded block as a first one of the plurality of intra prediction modes, and a second candidate intra prediction mode value (Mode.sub.2) and a third candidate intra prediction mode value (Mode.sub.3) that are determined in accordance with a predetermined offset from the first candidate intra prediction mode value and a modulo M operation. The method further includes determining an intra prediction mode value for the encoded block in accordance with the derived candidate list.

The present specification discloses a method of decoding an image. The method of decoding an image according to the method includes: obtaining transform skip information of a current block from a bitstream; obtaining multiple transform selection information of the current block on the basis of the transform skip information from the bitstream; and performing inverse transform on the current block on the basis of the multiple transform selection information, wherein the multiple transform selection information is used to set each of a horizontal transform type and a vertical transform type.

An image decoding method may include determining whether at least one of a height and a width of a current coding unit is greater than a predetermined size, obtaining, based on whether the current coding unit is to be split into transform units, a second coded block flag from the bitstream, the second coded block flag indicating whether a block of a luma component included in the at least one transform unit includes at least one transform coefficient in the bitstream, obtaining a residual signal of the block of the luma component included in the at least one transform unit, based on the second coded block flag, reconstructing the current coding unit based on the residual signal, and reconstructing the current image including the current coding unit, based on the reconstructed current coding unit. The split shape mode may indicate at least one of whether to perform splitting, a split direction, and a split type, and the split type may correspond to binary splitting, tri splitting, and quad splitting.

A method for video decoding in a decoder includes deriving for a block encoded under an intra prediction mode, a candidate list that includes a first candidate intra prediction mode value (Mode.sub.1) that corresponds to an intra prediction mode of a neighbor block that neighbors the encoded block as a first one of the plurality of intra prediction modes, and a second candidate intra prediction mode value (Mode.sub.2) and a third candidate intra prediction mode value (Mode.sub.3) that are determined in accordance with a predetermined offset from the first candidate intra prediction mode value and a modulo M operation, in which M is a power of 2 and not equal to 32. The method further includes determining an intra prediction mode value for the encoded block in accordance with the derived candidate list.

An apparatus for decoding video data includes memory and one or more processors implemented in circuitry. The one or more processors are configured to receive a bitstream including encoded video data, decode, from the bitstream, values for one or more syntax elements to generate a residual block for a current block, prediction information for the current block, and transform domain filtering information. The one or more processors are further configured to reconstruct the current block using the prediction information and the residual block to generate a reconstructed block. In response to determining that the transform domain filtering information indicates that transform domain filtering is enabled for the current block, the one or more processors are configured to perform transform domain filtering on the reconstructed block to generate a filtered block.

A method for decoding a video according to the present invention may comprise: determining an intra prediction mode of a current block, deriving reference samples from neighboring samples of the current block, obtaining a first prediction sample for the current block, based on the intra prediction mode and the reference samples, determining an offset for the first prediction sample, and obtaining a second prediction sample by applying the offset to the first prediction sample.

Techniques are described for improving transform coding. For example, an encoded block of video data can be obtained, and a width and/or a height of the block can be determined. The width can be compared to a first threshold and/or the height can be compared to a second threshold. A horizontal transform and a vertical transform can be determined for the block based on comparing the width of the block to the first threshold and/or the height of the block to the second threshold. The horizontal transform and the vertical transform are determined without decoding a syntax element that indicates the horizontal transform and the vertical transform (e.g., the syntax element is not in an encoded video bitstream processed by a decoding device). In some cases, residual data is determined using the horizontal and vertical transforms, and a video block is determined using the residual data and a predictive block.

An image decoding method performed by a decoding apparatus according to the present disclosure includes receiving a bitstream including residual information; deriving quantized transform coefficients for a current block based on the residual information included in the bitstream; deriving residual samples for the current block based on the quantized transform coefficients; and generating a reconstructed picture based on the residual samples for the current block.

A method for decoding a video according to the present invention may comprise: determining an intra prediction mode of a current block, deriving reference samples from neighboring samples of the current block, obtaining a first prediction sample for the current block, based on the intra prediction mode and the reference samples, determining an offset for the first prediction sample, and obtaining a second prediction sample by applying the offset to the first prediction sample.