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.

According to embodiments described herein, sub-pictures and/or virtual boundaries can be used for coding an image. For example, sub-pictures in the current picture can be used for predicting, reconstructing, and/or filtering the current picture. Virtual boundaries can be used for filtering reconstructed samples of the current picture. Through image coding based on the subpictures and/or virtual boundaries according to embodiments described herein, the subjective/objective quality of an image can be improved, and the consumption of hardware resources necessary for the coding can be reduced.

A method for decoding an image is provided. The method includes obtaining a first sample value associated with the image. The method further includes employing an ALF to filter the first sample value, the ALF being operable to filter the first sample value using any set of N coefficient values in which each one of the N coefficient values is included in a set of M unique coefficient values, wherein N is greater than 1 and M is greater than or equal to N and further wherein i) the set of M unique coefficient values consists of the following unique values or consists of a subset of the following unique values: +/−0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 12, 14, 15, 16, 17, 18, 20, 24, 28, 30, 31, 32, 33, 34, 36, 40, 48, 56, 60, 62, 63, 64, 65, 66, 68, 72, 80, 96, 112, 120, 124, 126, 127, or 128 and ii) the set of M unique coefficient values includes at least one of the following values: +/−3, 5, 6, 7, 9, 10, 12, 14, 15, 17, 18, 20, 24, 28, 30, 31, 33, 34, 36, 40, 48, 56, 60, 62, 63, 65, 66, 68, 72, 80, 96, 112, 120, 124, 126, 127.

A method for decoding an image is provided. The method includes obtaining a first sample value associated with the image. The method further includes employing an ALF to filter the first sample value, the ALF being operable to filter the first sample value using any set of N coefficient values in which each one of the N coefficient values is included in a set of M unique coefficient values, wherein N is greater than 1 and M is greater than or equal to N and further wherein i) the set of M unique coefficient values consists of the following unique values or consists of a subset of the following unique values: +/−0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 12, 14, 15, 16, 17, 18, 20, 24, 28, 30, 31, 32, 33, 34, 36, 40, 48, 56, 60, 62, 63, 64, 65, 66, 68, 72, 80, 96, 112, 120, 124, 126, 127, or 128 and ii) the set of M unique coefficient values includes at least one of the following values: +/−3, 5, 6, 7, 9, 10, 12, 14, 15, 17, 18, 20, 24, 28, 30, 31, 33, 34, 36, 40, 48, 56, 60, 62, 63, 65, 66, 68, 72, 80, 96, 112, 120, 124, 126, 127.

There is provided a method for encoding or decoding an image. The method comprises obtaining a first luma sample value, L1, associated with the image. The method comprises obtaining a second luma sample value, L2, associated with the image. The method further comprises obtaining a first luma delta value, ΔL1, wherein ΔL1=L2−L1. The method comprises obtaining a first product, P1, using ΔL1 and a first coefficient value, C1, wherein P1=(C1)(ΔL1). The method comprises calculating a first residual correction value, ΔI1 using P1 and a set of other products. The method comprises filtering an unfiltered chroma value, R.sub.C, associated with the image using the first residual correction value, ΔI1, thereby producing a filtered chroma value R.sup.F.sub.C associated with the image.

Methods, apparatuses, and non-transitory computer-readable storage mediums are provided for decoding a video signal. A decoder obtains a reference picture I associated with a video block within the video signal. The decoder may further obtain reference samples I(i,j) of the video block from a reference block in the reference picture I. The decoder may also obtain a first down-sampling filter and a second down-sampling filter to respectively generate luma and chroma inter prediction samples of the video block. The decoder may further obtain a third down-sampling filter and a fourth down-sampling filter to respectively generate the luma and chroma inter prediction samples of the video block when the video block is coded by affine mode. The decoder may also obtain inter prediction samples of the video block based on the third and fourth down-sampling filters being applied to the reference samples I(i,j).

A method by which a decoding device decodes an image, according to the present document, comprises the steps of: obtaining image information from a bitstream; generating a reconstructed picture of the current picture; deriving deblocking filter parameter information related to deblocking filter parameters on the basis of the image information; and performing deblocking filtering on the reconstructed picture on the basis of the deblocking filter parameters so as to generate a modified reconstructed picture.

A method by which a decoding device decodes an image, according to the present document, comprises the steps of: obtaining image information from a bitstream; generating a reconstructed picture of the current picture; deriving deblocking filter parameter information related to deblocking filter parameters on the basis of the image information; and performing deblocking filtering on the reconstructed picture on the basis of the deblocking filter parameters so as to generate a modified reconstructed picture.

In an image decoding device 200 according to the present invention, a decoding unit 210 is configured to decode a flag indicating whether chroma-related syntax is included in a picture parameter set, and in a case where the flag indicates that chroma-related syntax is included in the picture parameter set, the decoding unit 210 is configured to decode syntax for controlling deblocking filter processing of a Cb signal and a Cr signal.

A method implemented by a video coding apparatus includes applying a neural network (NN) filter to an unfiltered sample of a video unit to generate a filtered sample, where the NN filter is based on a first NN filter model having a first depth, or a second NN filter model having a second depth, where the depth comprises a number of residual blocks of the respective NN filter model, and where the second depth is different than the first depth. The method also includes performing a conversion between a video media file and a bitstream based on the filtered sample.