Lg Electronics Inc.

Guangdong Oppo Mobile Telecommunications Corp., Ltd.

Beijing Xiaomi Mobile Software Co., Ltd.

University of Southern California

Xiaomi Inc.

Industry-academic Cooperation Foundation, Chosun University

Moonmo Koo

Jaehyun Lim

Seunghwan Kim

Mehdi Salehifar

Junghak Nam

Eunyong Son

Sehoon Yea

Jin Seong Heo

Jaewon Sung

Taesup Kim

Hyeongmoon Jang

Jiwook Jung

Bumshik Lee

Yongjoon Jeon

Seungwook Park

Kyuwoon Kim

Seethal Paluri

Jie Zhao

Medhi Salehifar

Sunmi Yoo Yoo

Ling Li

Jung Hak Nam

Jungah Choi

Amir Said

Onur Gonen Guleryuz

Jungdong Seo

Antonio Ortega

Hilmi Enes Egilmez

Seoungwook Park

An image decoding method according to the present document comprises a step of deriving a corrected transform coefficient by applying low-frequency non-separable transform (LFNST) to a transform coefficient, wherein an LFNST set for applying the LFNST may be derived on the basis of an intra-prediction mode applied to the current block, and an LFNST matrix may be derived on the basis of the size of the current block and the LFNST set, the LFNST matrix derived as a 16×16 dimensional matrix if the width or the height of the current block is 4 and the width and the height are both 4 or greater, and the LFNST matrix derived as a 64×32 dimensional matrix if the width or the height of the current block is 8 and the width and the height are both 8 or greater. Therefore, coding performance capable of being brought by the LFNST can be maximized within the implementation complexity permitted in forthcoming standards.

Method and device for designing low-frequency non-separable transform

An image decoding method according to the present document comprises the steps of: deriving transform coefficients through inverse quantization on the basis of quantized transform coefficients for a target block; deriving modified transform coefficients on the basis of an inverse reduced secondary transform (RST) for the transform coefficients; and generating, on the basis of an inverse primary transform for the modified transform coefficients, a restoration picture based on residual samples for the target block, wherein the modified transform coefficients derived according to the inverse RST are two-dimensionally arranged according to the order of a row priority direction or a column priority direction according to an intra prediction mode to be applied to the target block.

Image coding method based on secondary transform, and device therefor

Embodiments of the present disclosure provide a method and apparatus for processing a video signal. A method for decoding a video signal according to an embodiment of the present disclosure includes obtaining a sub-block transform (SBT) flag indicating whether an SBT is applied, wherein the SBT represents a transform applied to one of sub-blocks split from a coding unit, determining a transform unit from the coding unit based on the SBT flag, determining a size value of the transform unit as a first reference value if DST-7 (Discrete Sine Transform type 7) or DCT-8 (Discrete Cosine Transform type 8) is applied and the size value of the transform unit is greater than the first reference value and less than a third reference value and determining the size value as a second reference value if DCT-2 (Discrete Cosine Transform type 2) is applied and the size value is equal to or greater than the third reference value, wherein the third reference value is greater than the second reference value and the second reference value is greater than the first reference value, obtaining transform coefficients based on the size value, and performing an inverse transform on the transform coefficients. A data processing time and the amount of data necessary for a transform can be reduced by performing coding in consideration of a region reduced according to a block size.

Method for processing image on basis of transform and device therefor

An image decoding method according to the present document may comprise the steps of: receiving image information including residual information and an LFNST index from a bitstream; deriving a transform coefficient on the basis of the residual information; deriving a flag variable related to whether LFNST is applied to a current block on the basis of the LFNST index; and performing the LFNST on the basis of the flag variable and the transform coefficient, wherein the flag variable is derived for each color component of the current block.

Image coding method and device therefor

A video decoding method performed by a decoding apparatus includes the steps of: deriving control points (CP) for a current block; acquiring movement vectors for the CPs; deriving a sample unit movement vector in the current block on the basis of the acquired movement vectors; and deriving a prediction sample for the current block on the basis of the sample unit movement vector. According to the present invention, it is possible to effectively perform, through sample unit motion vectors, inter-prediction not only in a case where an image in the current block is plane-shifted but also in a case where there are various image distortions.

Inter prediction method and apparatus in video coding system

A video decoding method according to the present document comprises a step of deriving a modified transform coefficient, and the step of deriving the transform coefficient may comprise the steps of: determining whether an LFNST can be applied to the height and width of a current block on the basis of the tree type and color format of the current block; parsing an LFNST index if the LFNST can be applied; and deriving the modified transform coefficient on the basis of the LFNST index and an LFNST matrix.

Transform-based video coding method, and device therefor

A video decoding method according to the present document is characterized by comprising: a step for deriving transform coefficients through inverse quantization on the basis of quantized transform coefficients for a target block; a step for deriving modified transform coefficients on the basis of an inverse reduced secondary transform (RST) of the transform coefficients; and a step for generating a reconstructed picture on the basis of residual samples for the target block on the basis of an inverse primary transform of the modified transform coefficients, wherein the inverse RST using a transform kernel matrix is performed on transform coefficients of the upper-left 4×4 region of an 8×8 region of the target block, and the modified transform coefficients of the upper-left 4×4 region, upper-right 4×4 region, and lower-left 4×4 region of the 8×8 region are derived through the inverse RST.

Video coding method on basis of secondary transform, and device for same

An image decoding method according to the present document comprises a step for performing inverse first-order transform and inverse non-separable transform on a residual sample. The inverse non-separable transform is performed on the basis of a transform index indicating a predetermined transform kernel matrix, the inverse first-order transform is performed on the basis of a multiple transform selection (MTS) index indicating MTS for a horizontal transform kernel and a vertical transform kernel, and a syntax element bin string for the transform index is derived on the basis of first context information when a tree type for a split structure of a target block is not a single tree type and is derived on the basis of second context information when the tree type is the single tree type.

Transform-based image coding method and device therefor

Techniques and systems for reconstructing a video signal, which include: obtaining a transform coefficient block by performing an entropy decoding and a dequantization for a current block; deriving a secondary transform corresponding to a specific area in the transform coefficient block, wherein the specific area represents an area including a top-left block of the transform coefficient block; performing an inverse secondary transform for each of subblocks within the specific area using the secondary transform; performing an inverse primary transform for a block which the inverse secondary transform is applied to; and reconstructing the current block using a block which the primary inverse transform is applied to.

Method and apparatus for processing video signal by applying secondary transform to partitioned block

An image decoding method according to the present document may comprise the steps of: deriving residual samples by applying at least one of LFNST and MTS to transform coefficients; and generating a reconstructed picture on the basis of the residual samples, wherein the LFNST is performed on the basis of an LFNST transform set, an LFNST kernel included in the LFNST transform set, and an LFNST index indicating the LFNST kernel, a first bin of a syntax element bin string for the LFNST index is derived on the basis of different context information according to a tree type of a current block, and a second bin of the syntax element bin string is derived on the basis of preconfigured context information.

Method and device for transform-based image coding

The present disclosure, in a method of decoding a video signal, provides a method including checking whether a transform skip is applied to a current block; acquiring a transform index indicating transform types applied to a horizontal direction and a vertical direction of the current block from among a plurality of predefined transform types from the video signal when the transform skip is not applied to the current block; and performing an inverse primary transform on the current block using the transform types indicated by the transform index, wherein the transform types applied to the horizontal direction and the vertical direction of the current block are determined from among transform types defined according to an intra prediction mode of the current block based on the transform index.

Method for performing transform index coding on basis of intra prediction mode, and device therefor

An image decoding method according to the present document comprises the steps of: deriving a transform coefficient for a current block on the basis of residual information; when LFNST is applied to the current block, receiving an LFNST index related to an LFNST matrix; and deriving a modified transform coefficient for the current block on the basis of the LFNST matrix, wherein the LFNST index may be signaled for a luma component of the current block.

Transform-based image coding method and apparatus therefor

An image decoding method according to the present document comprises the steps of: receiving residual information in a bitstream, wherein the residual information includes a transform skip flag for each individual component of the current block; deriving corrected transform coefficients, wherein the step for deriving includes a step for setting a variable indicating whether effective coefficients exist at positions other than that of a DC component of the current block to 0 when even one of the values of the transform skip flags for the individual components is 0, and a step for parsing an LFNST index on the basis of the variable being 0; and deriving an LFNST kernel for applying LFNST on the basis of the LFNST index, wherein the variable being 0 may indicate that effective coefficients exist at positions other than that of the DC component.

Transform-based image coding method and device for same

A video transform method includes: receiving a quantized transform coefficient for a target block and a transform index for a non-separated secondary transform; inverse-quantizing the quantized transform coefficient; deriving an input transform coefficient size indicating the length of the inverse-quantized transform coefficient to which the non-separated secondary transform has been applied, an output transform coefficient size indicating the length of a modified transform coefficient to which the non-separated secondary transform has been applied, and a transform set mapped to the intra mode of the target block, when the transform index does not indicate that the non-separated secondary transform is not performed; and deriving the modified transform coefficient on the basis of a matrix operation on a transform kernel matrix in the transform set indicated by the transform index, and a transform coefficient list corresponding to the input transform coefficient size.

Video coding method on basis of secondary transform, and device therefor

An image decoding method includes: acquiring a multiple transform selection (MTS) index and residual information from a bitstream; deriving transform coefficients for the current block on the basis of the residual information; and generating residual samples of the current block on the basis of the MTS index and the transform coefficients, wherein the MTS index indicates a transform kernel set to be applied to the current block among transform kernel set candidates, at least one bin among bins of a bin string of the MTS index is derived on the basis of context coding, the context coding is performed on the basis of values of increase and decrease in a context index pertaining to the MTS index, and a single value of increase and decrease in the context index can be used for the context coding of the first bin among the bins of the bin string.

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Seoul, South Korea

Moonmo Koo