An image decoding method according to embodiments of the present document may comprise the steps of: acquiring, via a bitstream, image information including residual information; generating reconstruction samples on the basis of the residual information; and performing an in-loop filtering procedure for the reconstruction samples so as to generate modified reconstruction samples. The step of generating of the modified reconstruction samples may comprise a step of determining whether the in-loop filtering procedure is performed across virtual boundaries. In an example, wherein the image information includes an SPS, and on the basis of whether reference picture resampling is available, whether the SPS includes additional virtual boundary-related information may be determined.

A method, computer program, and computer system is provided for coding video data. Video data including one or more subpictures is received. A network abstraction layer (NAL) unit type associated with each of the one or more subpictures is identified based on checking a flag corresponding to mixed NAL units in the one or more subpictures. The video data is decoded based on the identified NAL unit types.

A method for image decoding, according to the present invention, includes the following steps: receiving image information including a plurality of filter coefficients; generating a restored block for a current block on the basis of the image information; and applying an adaptive loop filter to the restored block on the basis of the plurality of filter coefficients. According to the present invention, image encoding efficiency may be improved, and complexity may be reduced.

A method for image decoding, according to the present invention, includes the following steps: receiving image information including a plurality of filter coefficients; generating a restored block for a current block on the basis of the image information; and applying an adaptive loop filter to the restored block on the basis of the plurality of filter coefficients. According to the present invention, image encoding efficiency may be improved, and complexity may be reduced.

A decoder includes a memory and processing circuitry. The processing circuitry, in operation, changes values of pixels in a first block and a second block to filter a boundary therebetween, using clipping such that change amounts of the respective values are within respective clip widths. The clip widths for the pixels in the first block and the second block are selected based on block sizes of the first block and the second block. The pixels in the first block include a first pixel located at a first position, and the pixels in the second block include a second pixel located at a second position corresponding to the first position with respect to the boundary. The clip widths include a first clip width and a second clip width corresponding to the first pixel and the second pixel, respectively, and the first clip width is different from the second width.

A decoder includes a memory and processing circuitry. The processing circuitry, in operation, changes values of pixels in a first block and a second block to filter a boundary therebetween, using clipping such that change amounts of the respective values are within respective clip widths. The clip widths for the pixels in the first block and the second block are selected based on block sizes of the first block and the second block. The pixels in the first block include a first pixel located at a first position, and the pixels in the second block include a second pixel located at a second position corresponding to the first position with respect to the boundary. The clip widths include a first clip width and a second clip width corresponding to the first pixel and the second pixel, respectively, and the first clip width is different from the second width.

A video signal processing method and apparatus for encoding or decoding a video signal is disclosed. More particularly, a video signal processing method and a video signal processing apparatus using the same are disclosed, wherein a method for processing a video signal comprises the steps of: obtaining a set of control point motion vectors for prediction of a current block; obtaining the motion vector of each sub-block of the current block using control point motion vectors of the set of control point motion vectors; obtaining a predictor of the each sub-block of the current block using the motion vectors of the each sub-block; obtaining a predictor of the current block by combining predictors of the each sub-block; and restoring the current block using the predictor of the current block.

In prediction, one of a first mode for deriving, using pixels in an image including a target block, predicted pixels in the target block, a second mode for deriving the predicted pixels in the target block using pixels in an image different from the image including the target block, a third mode for generating the predicted pixels in the target block using both the pixels in the image including the target block and pixels in the different image can be used. If the third mode is used in at least one of the first and second blocks, the intensity of deblocking filter to be performed for the boundary between the first and second blocks is set to the same intensity as in a case in which the first mode is used in at least one of the first and second blocks.

In prediction, one of a first mode for deriving, using pixels in an image including a target block, predicted pixels in the target block, a second mode for deriving the predicted pixels in the target block using pixels in an image different from the image including the target block, a third mode for generating the predicted pixels in the target block using both the pixels in the image including the target block and pixels in the different image can be used. If the third mode is used in at least one of the first and second blocks, the intensity of deblocking filter to be performed for the boundary between the first and second blocks is set to the same intensity as in a case in which the first mode is used in at least one of the first and second blocks.

An encoder includes circuitry and memory coupled to the circuitry. In operation, the circuitry: encodes information for deriving a parameter into a header of a bitstream; filters reconstructed samples in a first image using a filtering process, to generate a second image; determines whether the parameter has a predefined value; encodes a third image using the second image when the parameter has the predefined value; and encodes the third image using the first image when the parameter does not have the predefined value.