BR122023021072A2 - UNLOCKING METHOD, DEVICE FOR USE IN AN IMAGE ENCODER AND/OR AN IMAGE DECODER, ENCODER, DECODER, AND NON-TRAINER COMPUTER READABLE MEDIA - Google Patents

Abstract

“UNLOCKING METHOD, DEVICE FOR USE IN AN IMAGE ENCODER AND/OR AN IMAGE DECODER, ENCODER, DECODER, AND NON-TRAINER COMPUTER READABLE MEDIUM” The present invention provides an unlocking method for unlocking a transform block boundary within a coding block in an image encoding and/or an image decoding, wherein the coding block comprising transform blocks is encoded in the interprediction mode and the transform blocks comprising a first transform block and a second transform block which is adjacent to the first transform block; wherein the method comprises: determining when the boundary between the first transform block and the second transform block is a transform block boundary (such as an SBT boundary) and at least one of the first transform block and the second transform block transform has one or more non-zero transform coefficients (one or more non-zero residual transform coefficients), a value of a boundary strength (BS) parameter for the boundary between the first transform block and the second transform block transform be a first value; and performing deblocking filtering process for the boundary between the first transform block and the second transform block at least based on the value of the boundary strength parameter.

Description

CROSS REFERENCE FOR RELATED ORDERS

[001] This patent application claims the priority of US Provisional Patent Application No. 62/797,163, filed on January 25, 2019. The aforementioned patent application disclosure is incorporated herein by reference in its entirety.

TECHNICAL FIELD

[002] Embodiments of the present disclosure generally relate to the field of image processing, and particularly to an encoder, a decoder and corresponding deblocking filter adaptation methods, and more particularly to deblocking filter for block boundaries. transform caused by a sub-block transform coding tool, SBT.

BACKGROUND

[003] Video coding (video encoding and decoding) is used in a wide range of digital video applications, for example, digital TV broadcasting, video transmission over the Internet and mobile networks, real-time conversation applications such as video chat, video conferencing, DVD and Blu-ray discs, video content acquisition and editing systems, and security applications camcorders.

[004] The amount of video data required to represent even a relatively short video can be substantial, which can result in difficulties when the data must be transmitted or otherwise communicated over a bandwidth-capable communications network. limited bandwidth. Thus, video data is generally compressed before being communicated over modern-day telecommunications networks. The size of a video can also be an issue when the video is stored on a storage device because memory resources can be limited. Video compression devices often use software and/or hardware at the source to encode video data before transmission or storage, thus decreasing the amount of data required to represent digital video images. The compressed data is then received at the destination by a video decompression device that decodes the video data. With limited network resources and increasing demands for higher video quality, improved compression and decompression techniques that improve the compression ratio with little or no sacrifice in image quality are desirable.

[005] Block-based image coding schemes have in common that along block edges, edge artifacts may appear. These artifacts are due to the independent coding of the coding blocks. These edge artifacts are often easily visible to the user. One goal in block-based image coding is to reduce edge artifacts below a visibility threshold. This is done through unblocking filtering. This deblocking filtering is performed on the one hand on the decoding side in order to remove visible edge artifacts, but also on the encoding side in order to prevent edge artifacts from being encoded into the image.

[006] However, conventional approaches do not take into account that a discontinuity may arise for some cases where the edges between transform/coding blocks (such as transform/coding blocks having chroma samples or chroma components) using interprediction . Thus, unblocking filtering can be challenging or even not produce the expected results.

SUMMARY

[007] In view of the challenges mentioned above, embodiments of the present application aim to provide a deblocking filter apparatus, an encoder, a decoder and corresponding methods that can mitigate or even remove blocking artifacts across the boundaries between transform/encoding blocks ( such as, transform blocks having chroma samples) using interprediction, so as to improve coding efficiency.

[008] Particularly, in the context of interprediction, a sub-block transform (SBT) coding tool is introduced and the SBT coding tool is applied to both luma and chroma samples, embodiments of the present application also aim to provide another deblocking filter apparatus, another encoder, another decoder and corresponding methods that can mitigate or even remove blocking artifacts that would be caused by the sub-block transform (SBT) coding tool, so as to improve coding efficiency.

[009] The embodiments of the invention are defined by the features of the independent claims, and additional advantageous implementations of the embodiments by the features of the dependent claims.

[0010] Particular embodiments are described in the attached independent claims, with other embodiments in the dependent claims.

[0011] The foregoing and other objects are achieved by the subject matter of independent claims. Additional forms of implementation are evident from the dependent claims, the description and the figures.

[0012] According to a first aspect of the present disclosure, an unlocking method is provided, for unlocking a transform block boundary (inner edge) within a coding block in an image encoding and/or image decoding, wherein the coding block is coded (predicted) in the interprediction mode and the coding block includes transform blocks (such as the coding block is divided (separated) into transform blocks in/during the interprediction process, in particular , when sub-block transform is enabled, the current coding unit is divided into transform units) comprising a first transform block and a second transform block that is adjacent to the first transform block (e.g., transform blocks containing p0 and q0 are adjacent in the vertical or horizontal direction); wherein the method comprises: - determining (or defining), when the boundary between the first transform block (such as the first transform block using interprediction) and the second transform block (such as the second transform block using interprediction) is a transform block boundary and at least one of the first transform block and the second transform block has one or more non-zero transform coefficients (one or more non-zero residual transform coefficients), a value of a parameter of boundary strength (BS) for the boundary between the first transform block and the second transform block to be a first value; and - perform deblocking filtering process for the boundary between the first transform block and the second transform block at least based on the value of the boundary strength parameter.

[0013] It can be understood that the first and second transform blocks on the sides of the transform block boundary use interprediction. In one example, the coding block samples are chroma samples. In another example, the encoding block has luma samples and chroma samples. Correspondingly, in one example, the samples of the first and second transform blocks are chroma samples. In another example, the first and second transform blocks both have luma samples and chroma samples. Specifically, according to the prior art, the deblocking filter process is applied to encode sub-block edges and transform block edges of an image, but edges within the chroma components for which both sides of the edge use interprediction. are excluded. However, according to the first aspect of the present disclosure, it is permitted to unlock edges within chroma components for which both sides of the edge use interprediction.

[0014] It can be understood that, in addition to the boundary strength (BS) parameter for the boundary between the first transform block and the second transform block, other parameters can be considered for the deblocking filtering process. That is, depending on the outcome of the particular filtering decision, unblocking filtering may be performed, in some cases no samples may be modified, or in other cases, only one sample may be modified in each row or column perpendicular and adjacent to the boundary.

[0015] Note that the term "block", "coding block" or "image block" is used in the present disclosure, which can be applied to prediction units (PUs), coding units (CUs), etc. In VVC transform units and general coding units are mostly aligned, except in some scenarios when sub-block transform (SBT) is used. It can be understood that the terms "block/image block/coding block" can be interchanged in the present disclosure. The terms "sample/pixel" may be interchanged in this disclosure.

[0016] These boundaries between transform/coding blocks using interprediction within chroma components were not considered filtered in the prior art. According to the invention, however, the filtering process is improved to reduce block artifact from the boundaries between transform/encoding blocks by having chroma samples and using interprediction.

[0017] In a possible form of implementation of the method according to the first aspect as such, the first transform block has residual data, and the second transform block has no residual data, or the first transform block has no residual data , and the second transform block has residual data.

[0018] In a possible form of implementation of the method according to any previous implementation of the first aspect as such, the transform blocks are sub-block transform transform blocks, SBT.

[0019] In a possible form of implementation of the method according to any previous implementation of the first aspect or the first aspect as such, the number of transform blocks is 2 or 3 or another value.

[0020] In a possible form of implementation of the method according to any previous implementation of the first aspect or the first aspect as such, the boundary between the first transform block and the second transform block is a sub-block transform boundary , SBT.

[0021] In a possible form of implementation of the method according to any previous implementation of the first aspect or the first aspect as such, the determination, when the boundary between the first transform block and the second transform block is a block boundary of transform and at least one of the first transform block and the second transform block has one or more non-zero transform coefficients, a value of a boundary strength parameter for the boundary between the first transform block and the second block of transform to be a first value, comprises: - determining, when the boundary between the first transform block and the second transform block is a sub-block transform boundary, SBT, and at least one of the first transform block and the second transform block has one or more nonzero transform coefficients, a value of a boundary strength parameter for the boundary between the first transform block and the second transform block to be a first value.

[0022] In a possible form of implementation of the method according to any previous implementation of the first aspect or the first aspect as such, wherein the transform blocks further comprise a third transform block that is adjacent to the second transform block; the method further comprises: - determining, when the boundary between the second transform block and the third transform block is a sub-block transform boundary, SBT, and at least one of the second transform block and the third transform block has one or more non-zero transform coefficients, a value of a boundary strength parameter for the boundary between the second transform block and the third transform block to be a first value; or - determine, when the boundary between the second transform block and the third transform block is a sub-block transform, the SBT boundary and the second transform block and the third transform block have zero transform coefficients (all transform coefficients zero), a value of a boundary strength parameter for the boundary between the second transform block and the third transform block to be a second value.

[0023] In a possible form of implementation of the method according to any previous implementation or the first aspect as such, the first value is 1.

[0024] In a possible form of implementation of the method according to any previous implementation of the first aspect, the second value is zero.

[0025] In a possible form of implementation of the method according to any previous implementation of the first aspect or the first aspect as such, the transform block boundary between the first transform block and the second transform block must be unblocked (filtered ) only if the transform block boundary between the first and second transform blocks is aligned with (superimposed on) an n x n sample grid, where n is an integer.

[0026] In this way, the computational burden of the overall coding process can be further reduced.

[0027] In a possible form of implementation of the method according to any previous implementation of the first aspect or the first aspect as such, the transform block boundary between the first transform block and the second transform block must be unblocked (filtered ) even if the transform block boundary between the first and second transform blocks is not aligned with (superimposed on) an n x n sample grid, where n is an integer. It is allowed to unlock target boundaries, which are not aligned with an n x n grid.

[0028] In a possible form of implementation of the method according to any prior implementation of the first aspect, where n is 4 or 8. The prior art only considers boundaries that are superimposed on an 8 x 8 grid. If an internal SBT boundary is not aligned with the 8 x 8 grid when an asymmetric partition is applied, the internal boundary would be considered as a filtering candidate. By also filtering internal SBT boundaries, the block artifact caused by SBT is reduced.

[0029] In a possible form of implementation of the method according to any previous implementation of the first aspect or the first aspect as such, the samples of the first and second transform blocks are luma samples, or the first and second transform blocks. transform both have luma samples and chroma samples. Two-sided transform edges using interprediction on chroma components, such as that caused by SBT, can also result in block artifacts. In particular, when the main information of a video sequence is represented by chroma components (e.g., the campfire sequence used in the common test condition), such block artifacts can be serious. Therefore, this invention proposes the introduction of a deblocking filtering process for transform edges on both sides using interprediction on chroma components.

[0030] In a possible form of implementation of the method according to any previous implementation of the first aspect, wherein the n x n sample grid is 4 x 4 sample grid for the samples of the first and second transform blocks being luma samples; or, the n x n sample grid is 8 x 8 sample grid for the samples from the first and second transform blocks being chroma samples.

[0031] In a possible form of implementation of the method according to any previous implementation of the first aspect or the first aspect as such, wherein the coding block is divided in a horizontal or vertical direction.

[0032] In a possible form of implementation of the method according to any previous implementation of the first aspect or the first aspect as such, wherein, if the coding block is divided in a horizontal direction, the transform block boundary between the first transform block and the second transform block is a horizontal transform block boundary (a sub-block transform boundary, horizontal SBT); or, if the coding block is divided in a vertical direction, the transform block boundary between the first transform block and the second transform block is a vertical transform block boundary (a sub-block transform boundary, vertical SBT). The invention works for both vertical and horizontal transform block boundaries.

[0033] In a possible form of implementation of the method according to any previous implementation of the first aspect or the first aspect as such, wherein the current coding block is encoded using a sub-block transform tool, SBT, or the block boundary transform is performed by a sub-block transform tool, SBT.

[0034] According to a second aspect of the present disclosure, an unlocking method is provided, for unlocking block boundaries within a coding block (coding unit) in an image encoding and/or an image decoding, in that the coding block is coded (predicted) in interprediction mode (as such, the coding block is coded in a sub-block transform mode, SBT) and the coding block (an interpredicted coding block) includes blocks transform (the coding block is divided (separated) into transform blocks in or during the interprediction process, for example, when the sub-block transform is enabled, the current coding unit is divided into transform units) comprising a first transform block and a second transform block that is adjacent to the first transform block (e.g., transform blocks containing p0 and q0 are adjacent in the vertical or horizontal direction); wherein the method comprises: - in response to a determination that a transform block boundary between the first transform block and the second transform block is to be filtered, determining, when the boundary between the first transform block and the second transform block is a sub-block transform boundary, SBT, and at least one of the first transform block and the second transform block has one or more non-zero transform coefficients, a value of a boundary strength parameter for the boundary between the first transform block and the second transform block to be a first value; and - performing deblocking filtering process for the transform block boundary between the first transform block and the second transform block at least based on the value of the boundary strength parameter.

[0035] It can be understood that the first and second transform blocks on the sides of the transform block boundary use interprediction. In one example, the coding block samples are chroma samples. In one example, the coding block samples are luma samples. In another example, the encoding block has luma samples and chroma samples. Correspondingly, in one example, the samples of the first and second transform blocks are chroma samples; in another example, the samples from the first and second transform blocks are luma samples. In another example, the first and second transform blocks both have luma samples and chroma samples. Specifically, according to the prior art, the deblocking filter process is applied to encode sub-block edges and transform block edges of an image, but edges within the chroma components for which both sides of the edge use interprediction. are excluded, consequently internal SBT boundaries can also be excluded (because the SBT tool can be applied to luma and chroma components). However, according to the second aspect of the present disclosure, it is permitted to unlock the internal SBT boundaries that are caused by the sub-block transform (SBT) coding tool, especially, it is permitted to unlock the internal SBT boundaries within chroma components which is caused by the sub-block transform (SBT) coding tool.

[0036] It can be understood that, in addition to the boundary strength (BS) parameter for the boundary between the first transform block and the second transform block, other parameters can be considered for the deblocking filtering process. That is, depending on the outcome of the particular filtering decision, unblocking filtering may be performed, in some cases no samples may be modified, or in other cases, only one sample may be modified in each row or column perpendicular and adjacent to the boundary.

[0037] A partitioning of an interprediction block (i.e., a short intercoding block to a current coding block that is encoded in interprediction mode) into internal transform blocks is performed and the transformation is performed only for one of the blocks transform block, but not the other (because one transform block has residual data, the other has no residual data). Transform blocks can be symmetric (i.e. two sub-blocks of the same size) or asymmetric (i.e. the sub-blocks are not the same size). This partial transform can result in block artifact along the boundaries between internal transform blocks. These boundaries were not considered to be filtered in the prior art, which compromises the subjective quality when the Sub-Block Transform (SBT) is activated. According to the second aspect of the invention, however, the filtering process is improved to reduce the block artifact of the SBT boundaries caused by the SBT coding tool. When detecting the boundaries that would be considered filtered, the internal boundaries between the internal transform blocks caused by the SBT encoding tool are taken into account.

[0038] In a possible form of implementation of the method according to the second aspect as such, wherein the first transform block has residual data, and the second transform block has no residual data, or the first transform block has no residual data, and the second transform block has residual data.

[0039] In a possible form of implementation of the method according to any previous implementation of the second aspect or the second aspect as such, wherein the transform blocks are sub-block transform transform blocks, SBT.

[0040] In a possible form of implementation of the method according to any previous implementation of the second aspect or the second aspect as such, wherein the number of transform blocks is 2 or 3 or another value.

[0041] In a possible form of implementation of the method according to any previous implementation of the second aspect or the second aspect as such, the method further comprises: - determining whether the transform block boundary between the first transform block and the second Transform block should be filtered or not.

[0042] In a possible form of implementation of the method according to any prior implementation of the second aspect or the second aspect as such, wherein in response to a determination that the transform block boundary between the first transform block and the second transform block must be filtered, determine, when the boundary between the first transform block and the second transform block is a sub-block transform boundary, SBT, and at least one of the first transform block and the second transform block of transform has one or more non-zero transform coefficients, a value of a boundary strength parameter for the boundary between the first transform block and the second transform block to be a first value, comprises: - in response to a determining that the transform block boundary between the first transform block and the second transform block is aligned with (superimposed on) an n x n sample grid, determine, when the boundary between the first transform block and the second transform block transform is a transform boundary of sub-block, SBT and at least one of the first transform block and the second transform block has one or more non-zero transform coefficients, a value of a boundary strength parameter for the boundary between the first transform block and the second transform block to be a first value, where n is an integer.

[0043] In a possible form of implementation of the method according to any previous implementation of the second aspect, where n is 4 or 8.

[0044] In a possible form of implementation of the method according to any previous implementation of the second aspect or the second aspect as such, wherein the samples of the first and second transform blocks are luma samples, or the samples of the first and second transform blocks are chroma samples or the first and second transform blocks both have luma samples and chroma samples.

[0045] In a possible form of implementation of the method according to any previous implementation of the second aspect, wherein the n x n sample grid is 4 x 4 sample grid for the samples of the first and second transform blocks being luma samples; or the n x n sample grid is 8 x 8 sample grid for the samples from the first and second transform blocks being chroma samples. It has been found that two-sided transform edges using interprediction on chroma components, such as that caused by SBT, can also result in block artifacts. In particular, when the main information of a video sequence is represented by chroma components (e.g., the campfire sequence used in the common test condition), such block artifacts can be serious. Therefore, this invention proposes the introduction of a deblocking filtering process for two-sided transform edges using interprediction on chroma components.

[0046] In a possible form of implementation of the method according to any previous implementation of the second aspect or the second aspect as such, wherein the transform blocks further comprise: a third transform block that is adjacent to the second transform block; the method further comprises: - in response to a determination that a transform block boundary between the second transform block and the third transform block is aligned with (superimposed on) an n x n sample grid, determining, when the boundary between the second transform block and the third transform block is a sub-block transform boundary, SBT, and at least one of the second transform block and the third transform block has one or more non-zero transform coefficients, one value of a boundary strength parameter for the boundary between the second transform block and the third transform block to be a first value; or - in response to a determination that the transform block boundary between the second transform block and the third transform block is aligned with (superimposed on) an n x n sample grid, determine, when the boundary between the second transform block transform and the third transform block is a sub-block transform boundary, SBT, and both the second transform block and the third transform block have zero transform coefficients, a value of a boundary strength parameter for the boundary between the second transform block and the third transform block to be a second value.

[0047] In a possible form of implementation of the method according to any previous implementation of the second aspect, where n is 4 or 8. It has been found that 4 x 4 block edges occur in VVC more frequently than in HEVC. In HEVC, only quad-tree partitioning is allowed for coding blocks, i.e., the resulting coding unit is always square. While in VVC, quad-tree with multi-type tree partition is allowed, i.e., the partition can result in narrow 4 x N or flat N x 4 coding blocks. Additionally, subblock partition tools such as SBT may result in 4 x N or N x 4 transform block edges. Therefore, the grid size is set to 4 x 4 to account for filtering edges that do not were superimposed on an 8 x 8 grid.

[0048] In a possible form of implementation of the method according to any previous implementation of the second aspect or the second aspect as such, wherein samples from the second and third transform blocks are luma samples, or the samples from the second and third blocks of transform are chroma samples.

[0049] In a possible form of implementation of the method according to any previous implementation of the second aspect, wherein the n x n sample grid is 4 x 4 sample grid for the samples of the second and third transform blocks being luma samples; or the n x n sample grid is 8 x 8 sample grid for the second and third transform block samples being chroma samples.

[0050] In a possible form of implementation of the method according to any previous implementation of the second aspect or the second aspect as such, wherein the first value is 1.

[0051] In a possible form of implementing the method according to any previous implementation of the second aspect, wherein the second value is zero.

[0052] In a possible form of implementation of the method according to any previous implementation of the second aspect or the second aspect as such, wherein the coding block is divided in a horizontal or vertical direction.

[0053] In a possible form of implementation of the method according to any previous implementation of the second aspect or the second aspect as such, wherein, if the coding block is divided in a horizontal direction, the transform block boundary between the first transform block and the second transform block is a horizontal transform block boundary; or if the coding block is divided in a vertical direction, the transform block boundary between the first transform block and the second transform block is a vertical transform block boundary.

[0054] In a possible form of implementation of the method according to any previous implementation of the second aspect or the second aspect as such, wherein the current coding block is encoded using a sub-block transform tool, SBT, or the transform block boundary is caused by a sub-block transform tool, SBT.

[0055] According to a third aspect of the present disclosure, there is provided a device for use in an image encoder and/or an image decoder, to unlock a transform block boundary within a coding block, wherein the coding block is coded (predicted) in interprediction mode and the coding block is divided (separated) into transform blocks (for example, when sub-block transform is enabled, the current coding unit is divided into two units transform block) comprising a first transform block and a second transform block that is adjacent to the first transform block (for example, transform blocks containing p0 and q0 are adjacent in the vertical or horizontal direction); wherein the device comprises a deblocking filter configured to: - determine, when a boundary between the first transform block and the second transform block is a transform unit boundary and at least one of the first transform block and the second transform block of transform has one or more non-zero transform coefficients, a value of a boundary strength parameter for the boundary between the first transform block and the second transform block to be a first value; and - perform deblocking filtering process for the boundary between the first transform block and the second transform block at least based on the value of the boundary strength parameter.

[0056] In a possible form of implementation of the device according to the third aspect as such, wherein the first transform block has residual data and the second transform block has no residual data or the first transform block has no residual data and the second transform block has residual data.

[0057] In a possible form of implementation of the device according to any previous implementation of the third aspect or the third aspect as such, wherein the transform blocks are sub-block transform transform blocks, SBT.

[0058] In a possible form of implementation of the device according to any previous implementation of the third aspect or the third aspect as such, wherein the number of transform blocks is 2 or 3.

[0059] In a possible form of implementation of the device according to any prior implementation of the third aspect or the third aspect as such, wherein the boundary between the first transform block and the second transform block is a subtransform boundary -block, SBT.

[0060] In a possible form of implementation of the device according to any previous implementation of the third aspect or the third aspect as such, wherein the deblocking filter is configured to: - determine, when the boundary between a first transform block and a second transform block is a sub-block transform boundary, SBT, and at least one of the first transform block and the second transform block has one or more non-zero transform coefficients, a value of a strength parameter boundary for the boundary between the first transform block and the second transform block to be a first value.

[0061] In a possible form of implementation of the device according to any prior implementation of the third aspect or the third aspect as such, wherein the transform blocks further comprise a third transform block that is adjacent to the second transform block, and the deblocking filter is further configured to determine, when the boundary between the second transform block and the third transform block is a sub-block transform boundary, SBT, and at least one of the second transform block and the third transform block of transform has one or more non-zero transform coefficients, a value of a boundary strength parameter for the boundary between the second transform block and the third transform block to be a first value; or to determine, when the boundary between the second transform block and the third transform block is a sub-block transform, the SBT boundary and both the second transform block and the third transform block have zero transform coefficients, a value of a boundary strength parameter for the boundary between the second transform block and the third transform block to be a second value.

[0062] In a possible form of implementation of the device according to any previous implementation of the third aspect or the third aspect as such, wherein the first value is 1.

[0063] In a possible form of implementation of the device according to any previous implementation of the third aspect, wherein the second value is zero.

[0064] In a possible form of implementation of the device according to any previous implementation of the third aspect or the third aspect as such, wherein the transform block boundary between the first transform block and the second transform block is to be unblocked only if the transform block boundary between the first and second transform blocks is aligned with (superimposed on) an n x n sample grid, where n is an integer.

[0065] In a possible form of implementation of the device according to any previous implementation of the third aspect or the third aspect as such, wherein the transform block boundary between the first transform block and the second transform block is to be unblocked , even if the transform block boundary between the first and second transform blocks is not aligned with (superimposed on) an n x n sample grid, where n is an integer.

[0066] In a possible form of implementation of the device according to any previous implementation of the third aspect, where n is 4 or 8.

[0067] In a possible form of implementation of the device according to any prior implementation of the third aspect or the third aspect as such, wherein the samples of the first and second transform blocks are luma samples, or the samples of the first and second transform blocks are chroma samples.

[0068] In a possible form of implementation of the device according to any previous implementation of the third aspect, wherein the n x n sample grid is 4 x 4 sample grid for the samples of the first and second transform blocks being luma samples; or the n x n sample grid is 8 x 8 sample grid for the samples from the first and second transform blocks being chroma samples.

[0069] In a possible form of implementation of the device according to any previous implementation of the third aspect or the third aspect as such, wherein the coding block is divided in a horizontal or vertical direction.

[0070] In a possible form of implementation of the device according to any prior implementation of the third aspect or the third aspect as such, wherein, if the coding block is divided in a horizontal direction, the transform block boundary between the first transform block and the second transform block is a horizontal transform block boundary; or if the coding block is divided in a vertical direction, the transform block boundary between the first transform block and the second transform block is a vertical transform block boundary.

[0071] In a possible form of implementation of the device according to any prior implementation of the third aspect or the third aspect as such, wherein the current coding block is encoded using a sub-block transform tool, SBT, or the transform block boundary is caused by a sub-block transform tool, SBT.

[0072] According to a fourth aspect of the present disclosure, there is provided a device for use in an image encoder and/or an image decoder, to unlock block boundaries within a coding block (coding unit), in that the coding block is coded (predicted) in interprediction mode (the coding block is coded in a sub-block transform mode, SBT) and the coding block (an interpredicted coding block) is split (separated) into transform blocks (e.g., when sub-block transform is enabled, the current coding unit is divided into two transform units) comprising a first transform block and a second transform block that is adjacent to the first transform block. transformed (in the interprediction process, for example, the transform blocks containing p0 and q0 are adjacent in the vertical or horizontal direction); wherein the device comprises a deblocking filter configured to: - in response to a determination that a transform block boundary between the first transform block and the second transform block is to be filtered, determining, when the boundary between the first transform block and the second transform block is a sub-block transform boundary, SBT, and at least one of the first transform block and the second transform block has one or more non-zero transform coefficients, a value of a boundary strength parameter for the boundary between the first transform block and the second transform block to be a first value; and - performing deblocking filtering process for the transform block boundary between the first transform block and the second transform block at least based on the value of the boundary strength parameter.

[0073] In a possible form of implementation of the device according to any prior implementation of the fourth aspect, wherein the first transform block has residual data and the second transform block has no residual data or the first transform block has no residual data residuals and the second the transform block has residual data.

[0074] In a possible form of implementation of the device according to any prior implementation of the fourth aspect or the fourth aspect as such, wherein the transform blocks are sub-block transform transform blocks, SBT.

[0075] In a possible form of implementation of the device according to any previous implementation of the fourth aspect or the fourth aspect as such, wherein the number of transform blocks is 2 or 3.

[0076] In a possible form of implementation of the device according to any prior implementation of the fourth aspect or the fourth aspect as such, the method further comprises determining whether the transform block boundary between the first transform block and the second transform block transformed must be filtered or not.

[0077] In a possible form of implementation of the device according to any prior implementation of the fourth aspect or the fourth aspect as such, wherein the deblocking filter is configured to: - in response to a determination that the block boundary of transform between the first transform block and the second transform block is aligned with (superimposed on) an n x n sample grid, determine, when the boundary between the first transform block and the second transform block is a subtransform boundary -block, SBT and at least one of the first transform block and the second transform block has one or more non-zero transform coefficients, a value of a boundary strength parameter for the boundary between the first transform block and the second transform block to be a first value, where n is an integer.

[0078] In a possible form of implementation of the device according to any previous implementation of the fourth aspect or the fourth aspect as such, wherein n is 4 or 8.

[0079] In a possible form of implementation of the device according to any prior implementation of the fourth aspect or the fourth aspect as such, wherein the samples of the first and second transform blocks are luma samples, or the samples of the first and second transform blocks are chroma samples, or the first and second transform blocks both have luma samples and chroma samples. It was found that double-sided transform edges using interprediction on chroma components, such as a transform edge caused by SBT, can also result in block artifacts. In particular, when the main information of a video sequence is represented by chroma components (e.g., the campfire sequence used in the common test condition), such block artifacts can be serious. Therefore, this invention proposes the introduction of a deblocking filtering process for two-sided transform edges using interprediction on chroma components.

[0080] In a possible form of implementation of the device according to any previous implementation of the fourth aspect, wherein the n x n sample grid is 4 x 4 sample grid for the samples of the first and second transform blocks being luma samples; or the n x n sample grid is 8 x 8 sample grid for the samples from the first and second transform blocks being chroma samples.

[0081] 4 x 4 block edges have been found to occur in VVC more frequently than in HEVC. In HEVC, only quad-tree partitioning is allowed for coding blocks, i.e., the resulting coding unit is always a square. While in VVC, quad-tree with multi-type tree partition is allowed, i.e., the partition can result in narrow 4 x N or flat N x 4 coding blocks. Additionally, subblock partition tools such as SBT may result in 4 x N or N x 4 transform block edges. Therefore, the grid size is set to 4 x 4 to account for filtering edges that do not are superimposed on an 8 x 8 grid.

[0082] In a possible form of implementation of the device according to any previous implementation of the fourth aspect or the fourth aspect as such, wherein the transform blocks further comprise a third transform block that is adjacent to the second transform block; the deblocking filter is further configured to: - in response to a determination that a transform block boundary between the second transform block and the third transform block is aligned with (superimposed on) an n x n sample grid, determine, when the boundary between the second transform block and the third transform block is a sub-block transform boundary, SBT, and at least one of the second transform block and the third transform block has one or more different transform coefficients from zero, a value of a boundary strength parameter for the boundary between the second transform block and the third transform block to be a first value; or - in response to a determination that the transform block boundary between the second transform block and the third transform block is aligned with (superimposed on) an n x n sample grid, determine, when the boundary between the second transform block transform and the third transform block is a sub-block transform boundary, SBT, and both the second transform block and the third transform block have zero transform coefficients, a value of a boundary strength parameter for the boundary between the second transform block and the third transform block to be a second value.

[0083] In a possible form of implementation of the device according to any previous implementation of the fourth aspect, where n is 4 or 8.

[0084] In a possible form of implementation of the device according to any previous implementation of the fourth aspect or the fourth aspect as such, wherein samples from the second and third transform blocks are luma samples, or the samples from the second and third blocks of transform are chroma samples.

[0085] In a possible form of implementation of the device according to any previous implementation of the fourth aspect or the fourth aspect as such, wherein the n x n sample grid is 4 x 4 sample grid for the samples of the second and third blocks of transformed being luma samples; or the n x n sample grid is 8 x 8 sample grid for the second and third transform block samples being chroma samples.

[0086] In a possible form of implementation of the device according to any previous implementation of the fourth aspect or the fourth aspect as such, wherein the first value is 1.

[0087] In a possible form of implementation of the device according to any previous implementation of the fourth aspect, wherein the second value is zero.

[0088] In a possible form of implementation of the device according to any previous implementation of the fourth aspect or the fourth aspect as such, wherein the coding block is divided in a horizontal or vertical direction.

[0089] In a possible form of implementation of the device according to any prior implementation of the fourth aspect or fourth aspect as such, wherein, if the coding block is divided in a horizontal direction, the transform block boundary between the first transform block and the second transform block is a horizontal transform block boundary; or, if the coding block is divided in a vertical direction, the transform block boundary between the first transform block and the second transform block is a vertical transform block boundary.

[0090] In a possible form of implementation of the device according to any prior implementation of the fourth aspect or fourth aspect as such, wherein the current coding block is encoded using a sub-block transform tool, SBT, or the frontier block transform is caused by a sub-block transform tool, SBT.

[0091] In accordance with a fifth aspect of the present disclosure, there is provided an encoder comprising set of processing circuitry for carrying out the method according to any prior implementation of the first aspect or the first aspect as such or the method according to any previous implementation of the second aspect or the second aspect as such.

[0092] In accordance with a sixth aspect of the present disclosure, there is provided a decoder comprising set of processing circuitry for carrying out the method according to any prior implementation of the first aspect or the first aspect as such or the method according to any implementation of the second aspect or the second aspect as such.

[0093] According to a seventh aspect of the present disclosure, there is provided a computer program product comprising program code for carrying out the method according to any prior implementation of the first aspect or the first aspect as such or the method according to with any previous implementation of the second aspect or the second aspect as such.

[0094] In accordance with an eighth aspect of the present disclosure, there is provided a non-transitory computer readable medium carrying a program code which, when executed by a computer device, causes the computer device to perform the method in accordance with any implementation of the first aspect or the first aspect as such or the method according to any prior implementation of the second aspect or the second aspect as such.

[0095] According to a ninth aspect of the present disclosure, there is provided a decoder, comprising: one or more processors; and a non-transitory computer-readable storage medium coupled to the processors and storing programming for execution by the processors, wherein the programming, when executed by the processors, configures the decoder to perform the method in accordance with any prior implementation of the first aspect or the first aspect as such or the method according to any prior implementation of the second aspect or the second aspect as such.

[0096] According to a tenth aspect of the present disclosure, an encoder is provided, comprising: one or more processors; and a non-transitory computer-readable storage medium coupled to the processors and storing programming for execution by the processors, wherein the programming, when executed by the processors, configures the encoder to perform the method in accordance with any prior implementation of the first aspect or the first aspect as such or the method according to any prior implementation of the second aspect or the second aspect as such.

[0097] In accordance with an eleventh aspect of the present disclosure, an unlocking filter apparatus is provided for unlocking a transform block boundary within a coding block, wherein the coding block is encoded (predicted) in the interprediction mode and the coding block comprises transform blocks (as such, the coding block is divided (separated) into transform blocks during the interprediction process, for example, when the subblock transform is enabled, the unit current encoding is divided into two transform units) comprising a first transform block and a second transform block that is adjacent to the first transform block; wherein the deblocking filter comprises means for determining when the boundary between the first transform block and the second transform block is a transform block boundary and at least one of the first transform block and the second transform block has a or more non-zero transform coefficients, a value of a boundary strength parameter, BS, for the boundary between the first transform block and the second transform block to be a first value, and means for carrying out process filtering unlocking for the boundary between the first transform block and the second transform block at least based on the first BS parameter value.

[0098] According to a twelfth aspect of the present disclosure, an unlocking filter apparatus is provided for unlocking block boundaries within a coding block (coding unit), wherein the coding block is encoded (predicted ) in the interprediction mode (in particular, the coding block is encoded in a sub-block transform mode, SBT) and the coding block (an interpredicted coding block is divided (separated) into transform blocks in the process of interprediction, for example, when the subblock transform is enabled, the current coding unit is divided into two transform units) comprising a first transform block and a second transform block that is adjacent to the first transform block (e.g. example, transform blocks containing p0 and q0 are adjacent in the vertical or horizontal direction), the deblocking filter apparatus comprising means for in response to a determination that a transform block boundary between the first transform block and the second transform block transform must be filtered, determine, when the boundary between the first transform block and the second transform block is a sub-block transform boundary, SBT, and at least one of the first transform block and the second transform block has one or more non-zero transform coefficients, a value of a boundary strength parameter for the boundary between the first transform block and the second transform block to be a first value, and means for carrying out a process of filtering unlocking for the transform block boundary between the first transform block and the second transform block at least based on the value of the boundary strength parameter.

[0099] The method according to the first aspect of the invention, that is, determining, when the boundary between the first transform block and the second transform block is a transform block boundary and at least one of the first transform block and the second transform block has one or more non-zero transform coefficients, a value of a boundary strength parameter, BS, for the boundary between the first transform block and the second transform block to be a first value; and performing deblocking filtering process for the boundary between the first transform block and the second transform block at least based on the first value of the BS parameter can be performed by the apparatus according to the eleventh aspect of the invention. Other features and ways of implementing the apparatus according to the eleventh aspect of the invention correspond to the features and ways of implementing the method according to the first aspect of the invention.

[00100] The method according to the second aspect of the invention, that is, in response to a determination that a transform block boundary between the first transform block and the second transform block should be filtered, determining, when the boundary between the first transform block and the second transform block is a sub-block transform boundary, SBT, and at least one of the first transform block and the second transform block has one or more non-zero transform coefficients , a value of a boundary strength parameter for the boundary between the first transform block and the second transform block to be a first value, and perform deblocking filtering process for the transform block boundary between the first transform block transform and the second transform block at least based on the value of the boundary force parameter can be performed by the apparatus according to the twelfth aspect of the invention. Other features and ways of implementing the apparatus according to the twelfth aspect of the invention correspond to the features and ways of implementing the method according to the second aspect of the invention.

[00101] The apparatus according to the aspect can be extended into implementation forms corresponding to the implementation forms of a method according to any previous aspect. Therefore, an implementation form of the apparatus comprises the feature(s) of the corresponding implementation form of the method according to any foregoing aspect.

[00102] The advantages of the apparatus according to any previous aspect are the same as those for the corresponding implementation forms of the method according to any previous aspect.

[00103] According to a further aspect, the invention relates to an apparatus for decoding a video stream that includes a processor and a memory. The memory is storing instructions that make the processor perform the method according to the first aspect.

[00104] According to a further aspect, the invention relates to an apparatus for encoding a video stream that includes a processor and a memory. The memory is storing instructions that make the processor perform the method according to the first aspect.

[00105] Details of one or more embodiments are presented in the attached drawings and in the description below. Other features, objects and advantages will be apparent from the description, drawings and claims.

BRIEF DESCRIPTION OF THE DRAWINGS

[00106] In the following, embodiments of the invention are described in more detail with reference to the accompanying figures and drawings, in which: Figure 1A is a block diagram showing an example of a video coding system configured to implement embodiments of the invention; Figure 1B is a block diagram showing another example of a video coding system configured to implement embodiments of the invention; Figure 2 is a block diagram showing an example of a video encoder configured to implement embodiments of the invention; Figure 3 is a block diagram showing an example structure of a video decoder configured to implement embodiments of the invention; Figure 4 is a block diagram illustrating an example of an encoding apparatus or a decoding apparatus; Figure 5 is a block diagram illustrating another example of an encoding apparatus or a decoding apparatus; Figure 6 is a block diagram illustrating an example of unblocking subpartition edges within a coding unit (CU); Figure 7 is a block diagram illustrating another example of unblocking subpartition edges within a CU; Figure 8 is a block diagram illustrating an example of unblocking sub-block TU boundaries within a CU that overlaps an 8 x 8 sample grid; Figure 9 is a block diagram illustrating an example of unlocking all sub-block TU boundaries within a CU that overlaps a 4 x 4 sample grid; Figure 10 is a block diagram illustrating an example whereby when the sub-block size is < 8 samples orthogonally in the unblocking direction, then a weak filter that uses only 3 samples in the unblocking decision and that modifies only a sample is used; Figure 11 illustrates sub-block edges caused by TU size limitations; Figure 12 shows a coding unit divided into multiple transform units; Figure 13 illustrates unlocking of all sub-block TU boundaries within a CU that overlaps (aligned with) an 8 x 8 sample grid; Figure 14 shows a coding unit that is further divided into multiple transform units; Figure 15 shows a coding unit that is further divided into multiple transform units according to the residual quadruple tree (RQT) as subblock transform; Figure 16 shows a vertical boundary between two blocks P and Q; Figure 17 shows a flowchart for the method according to the first aspect of the invention; Figure 18 shows a flowchart for the method according to the second aspect of the invention; Figure 19 shows a schematic diagram of a device for encoding video; Figure 20 shows a schematic diagram of a device for encoding video; Figure 21 is a block diagram showing an example structure of a content delivery system that performs a content delivery service; and Figure 22 is a block diagram showing a structure of an example of a terminal device.

[00107] In the following, identical reference signals refer to identical or at least functionally equivalent resources, if not explicitly specified otherwise.

DETAILED DESCRIPTION OF MODALITIES

[00108] In the following description, reference is made to the attached figures, which form part of the disclosure and which show, by way of illustration, specific aspects of the embodiments of the invention or specific aspects in which the embodiments of the present invention can be used. It is understood that embodiments of the invention can be used in other aspects and comprise structural or logical changes not represented in the figures. The following detailed description, therefore, should not be taken in a limiting sense, and the scope of the present invention is defined by the appended claims.

[00109] For example, it is understood that a disclosure in connection with a described method may also be true for a corresponding device or system configured to carry out the method and vice versa. For example, if one or a plurality of specific method steps are described, a corresponding device may include one or a plurality of units, e.g., functional units, for carrying out the described one or plurality of method steps (e.g., a unit performing the or plurality of steps, or a plurality of units, each performing one or more of the plurality of steps), even if such one or more units are not explicitly described or illustrated in the figures. On the other hand, for example, if a specific apparatus is described based on one or a plurality of units, e.g. functional units, a corresponding method may include a step for realizing the functionality of one or a plurality of units (e.g. , a step carrying out the functionality of one or a plurality of units, or a plurality of steps, each carrying out the functionality of one or more of the plurality of units), even if such one or a plurality of steps are not explicitly described or illustrated in the figures. Furthermore, it is understood that features of the various exemplary embodiments and/or aspects described herein may be combined with each other unless specifically indicated otherwise.

[00110] Video coding typically refers to the processing of a sequence of images, which form the video or video sequence. Instead of the term “image” (“picture”), the term “frame” or “image” (“image”) can be used synonymously in the field of video coding. Video coding (or coding in general) comprises two parts, video encoding and video decoding. Video coding is performed on the source side, typically comprising processing (e.g. by compression) of the original video images to reduce the amount of data required to represent the video images (for more efficient storage and/or transmission) . Video decoding is performed on the target side and typically comprises inverse processing compared to the encoder to reconstruct the video images. Embodiments that refer to "encoding" video images (or images in general) should be understood as relating to "encoding" or "decoding" video images or respective video sequences. The combination of encoding part and decoding part is also known as CODEC (Encoding and Decoding).

[00111] In the case of lossless video coding, the original video images can be reconstructed, i.e., the reconstructed video images have the same quality as the original video images (assuming no transmission loss or other data loss during storage or transmission). In the case of lossy video coding, additional compression, for example by quantization, is performed, to reduce the amount of data representing the video images, which cannot be completely reconstructed in the decoder, i.e. the quality of the images reconstructed video images is inferior or worse compared to the quality of the original video images.

[00112] Various video coding standards belong to the group of “lossy hybrid video codecs” (i.e., they combine spatial and temporal prediction in the sample domain and 2D transform coding to apply quantization in the transform domain). Each image in a video sequence is typically partitioned into a set of non-overlapping blocks, and encoding is typically performed at a block level. In other words, in the encoder, the video is typically processed, i.e. encoded, at a block level (video block), for example by using spatial prediction (intra-picture) and/or temporal prediction (inter-picture) to generate a prediction block, subtract the prediction block from the current block (block currently processed/to be processed) to obtain a residual block, transform the residual block, and quantize the residual block in the transform domain to reduce the amount of data to be transmitted ( compression), while in decoder, inverse processing compared to encoder is applied to the encoded or compressed block to reconstruct the current block for representation. Furthermore, the encoder duplicates the decoder processing loop so that both will generate identical predictions (e.g., intra- and interpredictions) and/or reconstructions for processing, i.e., coding of subsequent blocks.

[00113] In the following embodiments of a video coding system 10, a video encoder 20 and a video decoder 30 are described based on Figures 1 to 3.

[00114] Figure 1A is a schematic block diagram illustrating an example coding system 10, for example, a video coding system 10 (or coding system 10 for short) that may utilize techniques of the present application. The video encoder 20 (or encoder 20 for short) and the video decoder 30 (or decoder 30 for short) of the video coding system 10 represent examples of devices that can be configured to perform techniques in accordance with various examples described in the present application. .

[00115] As shown in Figure 1A, the coding system 10 comprises a source device 12 configured to provide encoded image data 21, for example, to a destination device 14 to decode the encoded image data 13.

[00116] The source device 12 comprises an encoder 20 and may additionally, i.e. optionally, comprise an image source 16, a preprocessor (or preprocessing unit) 18, e.g. image 18, and a communication interface or communication unit 22.

[00117] The image source 16 may comprise or be any type of image capturing device, e.g., a camera for capturing a real-world image and/or any type of an imaging device, e.g., a computer graphics processor to generate a computer-animated image, or any type of other device to obtain and/or provide a real-world image, a computer-generated image (e.g., a screen content, a virtual reality image ( VR)) and/or any combination thereof (e.g. an augmented reality (AR) image). The image source can be any type of memory or storage storing any of the above-mentioned images.

[00118] In distinction to the preprocessor 18 and the processing performed by the preprocessing unit 18, the image or image data 17 may also be referred to as the raw image or raw image data 17.

[00119] The preprocessor 18 is configured to receive the (raw) image data 17 and to perform preprocessing on the image data 17 to obtain a preprocessed image 19 or preprocessed image data 19. Preprocessing -processing performed by preprocessor 18 may, for example, comprise cropping, color format conversion (e.g., from RGB to YCbCr), color correction, or noise elimination. It can be understood that the preprocessing unit 18 can be an optional component.

[00120] The video encoder 20 is configured to receive the preprocessed image data 19 and provide encoded image data 21 (more details will be described below, for example, based on Figure 2).

[00121] The communication interface 22 of the source device 12 may be configured to receive the encoded image data 21 and to transmit the encoded image data 21 (or any further processed version thereof) over the communication channel 13 to another device, for example, the target device 14 or any other device, for storage or direct reconstruction.

[00122] The destination device 14 comprises a decoder 30 (e.g., a video decoder 30) and may additionally, i.e. optionally, comprise a communication interface or communication unit 28, a post-processor 32 (or post-processing unit 32) and a display device 34.

[00123] The communication interface 28 of the destination device 14 is configured to receive the encoded image data 21 (or any further processed version thereof), for example, directly from the source device 12 or from any other source, e.g., a storage device, e.g., an encoded image data storage device, and providing the encoded image data 21 to the decoder 30.

[00124] The communication interface 22 and the communication interface 28 may be configured to transmit or receive the encoded image data 21 or encoded data 13 via a direct communication link between the source device 12 and the destination device 14 , for example, a direct wired or wireless connection, or through any type of network, for example, a wired or wireless network or any combination thereof, or any type of private and public network, or any type of combination thereof .

[00125] Communication interface 22 may be, for example, configured to package the encoded image data 21 into an appropriate format, e.g., packets, and/or process the encoded image data using any type of encoding or processing. transmission for transmission over a communications link or communications network.

[00126] The communication interface 28, forming the counterpart of the communication interface 22, may be, for example, configured to receive the transmitted data and process the transmission data using any type of decoding or processing and/or corresponding transmission unpacking to obtain the encoded image data 21.

[00127] Both communication interface 22 and communication interface 28 can be configured as unidirectional communication interfaces, as indicated by the arrow for communication channel 13 in Figure 1A pointing from the source device 12 to the destination device 14, or bidirectional communication interfaces, and can be configured, for example, to send and receive messages, for example, to configure a connection, to recognize and exchange any other information related to the communication link and/or data transmission, by example, transmission of encoded image data.

[00128] The decoder 30 is configured to receive the encoded image data 21 and provide decoded image data 31 or a decoded image 31 (more details will be described below, for example, based on Figure 3 or Figure 5).

[00129] The post-processor 32 of the target device 14 is configured to post-process the decoded image data 31 (also called reconstructed image data), e.g., the decoded image 31, to obtain post-process image data. processed images 33, for example, a post-processed image 33. The post-processing performed by the post-processing unit 32 may comprise, for example, color format conversion (e.g., from YCbCr to RGB), color correction, cropping, or resampling, or any other processing, for example, to prepare the decoded image data 31 for display, for example, by the display device 34.

[00130] The display device 34 of the target device 14 is configured to receive the post-processed image data 33 to display the image, for example, to a user or viewer. The display device 34 may be or comprise any type of display screen for representing the reconstructed image, for example, an integrated or external display screen or monitor. Display screens may, for example, comprise liquid crystal display screens (LCD), organic light emitting diode (OLED) display screens, plasma display screens, projectors, microLED display screens, a liquid crystal on silicon (LCoS), digital light processor (DLP) or any other type of display screen.

[00131] Although Figure 1A depicts the source device 12 and the destination device 14 as separate devices, device embodiments may also comprise both or both functionality, the source device 12 or corresponding functionality and the destination device 14 or corresponding functionality. In such embodiments, the source device 12 or corresponding functionality and the target device 14 or corresponding functionality may be implemented using the same hardware and/or software or by separate hardware and/or software or any combination thereof.

[00132] As will be apparent to the skilled person based on the description, the existence and (exact) separation of functionalities of the different units or functionalities within the source device 12 and/or target device 14, as shown in Figure 1A, may vary depending on the current device and application.

[00133] The encoder 20 (e.g., a video encoder 20) or the decoder 30 (e.g., a video decoder 30) or both, the encoder 20 and the decoder 30 can be implemented by means of a set of processing circuits. processing as shown in Figure 1B, such as one or more microprocessors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), discrete logic, hardware, dedicated video encoding, or any combination thereof. Encoder 20 may be implemented through processing circuitry 46 to incorporate the various modules as discussed in connection with encoder 20 of Figure 2 and/or any other encoder system or subsystem described herein. Decoder 30 may be implemented through processing circuitry 46 to incorporate the various modules as discussed in connection with decoder 30 of Figure 3 and/or any other decoder system or subsystem described herein. The processing circuitry may be configured to perform the various operations as discussed later. As shown in Figure 5, if the techniques are implemented partially in software, a device may store instructions for the software on a suitable non-transitory computer-readable storage medium and may execute the instructions in hardware using one or more processors to perform the techniques. of this disclosure. Any of video encoder 20 and video decoder 30 may be integrated as part of a combined encoder/decoder (CODEC) in a single device, for example, as shown in Figure 1B.

[00134] The source device 12 and the destination device 14 may comprise any of a wide range of devices, including any type of portable or stationary devices, for example, notebooks or laptops, mobile phones, smartphones, tablets or tablet computers , cameras, desktop computers, set-top boxes, televisions, display devices, digital media players, video game consoles, video streaming devices (such as content services servers or content delivery servers), broadcast receiving device, device broadcast transmitter, or similar and may use no or any type of operating system. In some cases, the source device 12 and the destination device 14 may be equipped for wireless communication. Thus, the source device 12 and the destination device 14 may be wireless communication devices.

[00135] In some cases, the video coding system 10 illustrated in Figure 1A is only an example and the techniques of the present application can be applied to video coding settings (e.g., video encoding or video decoding) that do not necessarily include any data communication between the encoding and decoding devices. In other examples, data is retrieved from local memory, transmitted over a network, or the like. A video encoding device may encode and store data to memory and/or a video decoding device may retrieve and decode data from memory. In some examples, encoding and decoding are performed by devices that do not communicate with each other, but simply encode data into memory and/or retrieve and decode data from memory.

[00136] For convenience of description, embodiments of the invention are described herein, for example, by reference to High Efficiency Video Coding (HEVC) or Versatile Video Coding (VVC) reference software, the coding standard next-generation video technology developed by the Joint Video Coding Collaboration Team (JCT-VC) of the ITU-T Video Coding Specialist Group (VCEG) and ISO/IEC Moving Picture (MPEG) Specialist Group. A person skilled in the art will understand that embodiments of the invention are not limited to HEVC or VVC.

Encoder and Coding Method

[00137] Figure 2 shows a schematic block diagram of an example video encoder 20 that is configured to implement the techniques of the present application. In the example of Figure 2, the video encoder 20 comprises an input 202 (or input interface 202), a residual calculation unit 204, a transform processing unit 206, a quantization unit 208, an inverse quantization unit 210 and inverse transform processing unit 212, a reconstruction unit 214, a loop filter unit 220, a decoded picture buffer (DPB) 230, a mode selection unit 260, an entropy coding unit 270, and a 272 output (or 272 output interface). The mode selection unit 260 may include an interprediction unit 244, an intraprediction unit 254, and a partitioning unit 262. Interprediction unit 244 may include a motion estimation unit and a motion compensation unit (not shown). . A video encoder 20, as shown in Figure 2, may also be referred to as a hybrid video encoder or a video encoder according to a hybrid video codec.

[00138] The residual calculation unit 204, the transform processing unit 206, the quantization unit 208, the mode selection unit 260 may be referred to as forming a direct signal path of the encoder 20, while the quantization unit inverse 210, the inverse transform processing unit 212, the reconstruction unit 214, the buffer 216, the loop filter 220, the decoded picture buffer (DPB) 230, the interprediction unit 244, and the intraprediction unit 254 may be referred to as forming a reverse signal path of the video encoder 20, wherein the reverse signal path of the video encoder 20 corresponds to the signal path of the decoder (see video decoder 30 in Figure 3). The inverse quantization unit 210, the inverse transform processing unit 212, the reconstruction unit 214, the loop filter 220, the decoded picture buffer (DPB) 230, the interprediction unit 244, and the intraprediction unit 254 are also referred to to form the “built-in decoder” of the video encoder 20.

Image and Image Partitioning (Images and Blocks)

[00139] The encoder 20 can be configured to receive, for example, through input 202, an image 17 (or image data 17), for example, an image of a sequence of images forming a video or video sequence. The received image or image data may also be a preprocessed image 19 (or preprocessed image data 19). For simplicity, the following description refers to image 17. Image 17 may also be referred to as the current image or image to be encoded (in particular in video coding to distinguish the current image from other images, e.g. images previously encoded and/or decoded from the same video sequence, i.e. the video sequence that also includes the current image).

[00140] A (digital) image is or can be considered as a two-dimensional array or matrix of samples with intensity values. A sample in the array may also be referred to as a pixel (short form of picture element) or pel. The number of samples in horizontal and vertical direction (or axis) of the matrix or image defines the size and/or resolution of the image. For color representation, three color components are typically employed, i.e., the image can be represented or include three sample matrices. In the RBG format or color space, an image comprises a corresponding red, green, and blue sample matrix. However, in video coding, each pixel is typically represented in a luminance and chrominance format or color space, e.g. YCbCr, which comprises a luminance component denoted by Y (sometimes also L is used instead) and two chrominance components indicated by Cb and Cr. The luminance component (or luma for short) Y represents the brightness or intensity of the gray level (e.g. as in a grayscale image), while the two chrominance components (or chroma for short) Cb and Cr represent the chromaticity or components of color information. Consequently, an image in YCbCr format comprises a luminance sample matrix of luminance sample values (Y) and two chrominance sample matrices of chrominance values (Cb and Cr). Images in RGB format can be converted or transformed into YCbCr format and vice versa, the process is also known as color transformation or conversion. If an image is monochromatic, the image may comprise only one luminance sample matrix. Consequently, an image can be, for example, an array of luma samples in monochrome format or an array of luma samples and two corresponding arrays of chroma samples in color format 4:2:0, 4:2:2 and 4:4:4.

[00141] Embodiments of the video encoder 20 may comprise an image partitioning unit (not depicted in Figure 2) configured to partition the image 17 into a plurality of image blocks 201 (typically non-overlapping). These blocks may also be referred to as root blocks, macroblocks (H.264/AVC), or coding tree blocks (CTB) or coding tree units (CTU) (H.265/HEVC and VVC). The image partitioning unit can be configured to use the same block size for all images in a video sequence and the corresponding grid defining the block size, or to change the block size between images or subsets or groups of images , and partition each image into corresponding blocks.

[00142] In other embodiments, the video encoder may be configured to directly receive a block 201 of image 17, e.g., one, several, or all of the blocks forming image 17. Image block 201 may also be referred to as current image block or image block to be encoded.

[00143] Like image 17, image block 201 again is or may be considered as a two-dimensional array or array of samples with intensity values (sample values), albeit of smaller dimension than image 17. In other words , block 201 may comprise, for example, a sample matrix (e.g., a luma matrix in the case of a monochrome image 17, or a luma or chroma matrix in the case of a color image) or three sample matrices ( for example, one luma and two chroma matrices in the case of a color image 17) or any other number and/or type of matrices depending on the applied color format. The number of samples in horizontal and vertical direction (or axis) of block 201 defines the size of block 201. Consequently, a block may, for example, comprise an MxN matrix (M column by N row) of samples, or an MxN matrix of transform coefficients.

[00144] Embodiments of video encoder 20, as shown in Figure 2, can be configured to encode image 17 block by block, for example, coding and prediction are performed per block 201.

Residual Calculation

[00145] The residual calculation unit 204 may be configured to calculate a residual block 205 (also referred to as residual 205) based on the image block 201 and a prediction block 265 (additional details about the prediction block 265 are provided later ), for example, subtracting sample values from the prediction block 265 from sample values from the image block 201, sample by sample (pixel by pixel) to obtain the residual block 205 in the sample domain.

Transformed

[00146] The transform processing unit 206 may be configured to apply a transform, e.g., a discrete cosine transform (DCT) or discrete sine transform (DST), to the sample values of the residual block 205 to obtain coefficients of transform 207 into a transform domain. Transform coefficients 207 may also be referred to as transform residual coefficients and represent the residual block 205 in the transform domain.

[00147] The transform processing unit 206 can be configured to apply integer approximations of DCT/DST, such as the transforms specified for H.265/HEVC. Compared to an orthogonal DCT transform, such integer approximations are typically scaled by a certain factor. In order to preserve the norm of the residual block that is processed by the forward and inverse transforms, additional scaling factors are applied as part of the transform process. Scaling factors are typically chosen based on certain constraints, such as scaling factors being a power of two for branch operations, bit depth of transform coefficients, tradeoff between accuracy and implementation costs, etc. Specific scaling factors are, for example, specified for the inverse transform, for example, by the inverse transform processing unit 212 (and the corresponding inverse transform, for example, by the inverse transform processing unit 312 in the video decoder 30). and corresponding scaling factors for direct transformation, for example by transform processing unit 206, in an encoder 20 may be specified accordingly.

[00148] Embodiments of the video encoder 20 (respectively, transform processing unit 206) may be configured to output transform parameters, e.g., a type of transform or transforms, e.g., directly or encoded or compressed through the unit entropy coding 270, such that, for example, video decoder 30 can receive and use the transform parameters for decoding.

Quantization

[00149] The quantization unit 208 can be configured to quantize the transform coefficients 207 to obtain quantized coefficients 209, for example, applying scalar quantization or vector quantization. Quantized coefficients 209 may also be referred to as quantized transform coefficients 209 or quantized residual coefficients 209.

[00150] The quantization process may reduce the bit depth associated with some or all of the transform coefficients 207. For example, an n-bit transform coefficient may be rounded down to an m-bit transform coefficient during quantization , where n is greater than m. The degree of quantization can be modified by adjusting a quantization parameter (QP). For example, for scalar quantization, different scaling can be applied to achieve finer or coarser quantization. Smaller quantization step sizes correspond to finer quantization, while larger quantization step sizes correspond to coarser quantization. The applicable quantization step size can be indicated by a quantization parameter (QP). The quantization parameter may, for example, be an index for a predefined set of applicable quantization step sizes. For example, small quantization parameters may correspond to fine quantization (small quantization step sizes) and large quantization parameters may correspond to coarse quantization (large quantization step sizes) or vice versa. Quantization may include division by a quantization step size and a corresponding and/or inverse dequantization, e.g., by inverse quantization unit 210, may include multiplication by the quantization step size. Embodiments according to some standards, e.g., HEVC, may be configured to use a quantization parameter to determine the quantization step size. Generally, the quantization step size can be calculated based on a quantization parameter using a fixed-point approximation of an equation including division. Additional scaling factors can be introduced for quantization and dequantization to restore the residual block norm, which can be modified because of the scaling used in the fixed-point approximation of the equation for the quantization step size and quantization parameter. In an example implementation, inverse transform scaling and dequantization can be combined. Alternatively, custom quantization tables can be used and signaled from an encoder to a decoder, for example in a bitstream. Quantization is a lossy operation, where the loss increases with increasing quantization step sizes.

[00151] Embodiments of the video encoder 20 (respectively, quantization unit 208) may be configured to output quantization parameters (QP), for example, directly or encoded via the entropy coding unit 270, such that, for example, video decoder 30 can receive and apply quantization parameters for decoding.

Inverse Quantization

[00152] The inverse quantization unit 210 is configured to apply the inverse quantization of the quantization unit 208 on the quantized coefficients to obtain dequantized coefficients 211, for example, by applying the inverse of the quantization scheme applied by the quantization unit 208 based on or using the same quantization step size as the quantization unit 208. The dequantized coefficients 211 may also be referred to as dequantized residual coefficients 211 and correspond - although normally not identical to the transform coefficients due to quantization loss - to the transform coefficients 207 .

Inverse Transform

[00153] The inverse transform processing unit 212 is configured to apply the inverse transform of the transform applied by the transform processing unit 206, e.g., an inverse discrete cosine transform (DCT) or inverse discrete sine transform (DST). or other inverse transforms, to obtain a residual block 213 (or corresponding dequantized coefficients 213) in the sample domain. The reconstructed residual block 213 may also be referred to as the (reconstructed) transform block 213.

Reconstruction

[00154] The reconstruction unit 214 (e.g., adder or adder 214) is configured to add the transform (reconstructed) block 213 (i.e., reconstructed residual block 213) to the prediction block 265 to obtain a reconstructed block 215 in the sample domain, for example, adding - sample by sample - the sample values from the reconstructed residual block 213 and the sample values from the prediction block 265.

Filtering

[00155] The loop filter unit 220 (or "loop filter" for short 220) is configured to filter the reconstructed block 215 to obtain a filtered block 221 or, in general, to filter reconstructed samples to obtain filtered samples. The loop filter unit is, for example, configured to smooth pixel transitions, or otherwise improve video quality. The loop filter unit 220 may comprise one or more loop filters, such as an unblocking filter, an adaptive sample offset (SAO) filter, or one or more other filters, e.g., a bilateral filter, a loop filter. adaptive filter (ALF), a sharpening filter, smoothing filters, or collaborative filters, or any combination thereof. Although the loop filter unit 220 is shown in Figure 2 as being a loop filter, in other configurations, the loop filter unit 220 may be implemented as a post-loop filter. The filtered block 221 may also be referred to as the filtered reconstructed block 221. In the present disclosure, the improved loop filter, particularly the improved deblocking filter apparatus is provided and will be introduced in detail later.

[00156] Embodiments of the video encoder 20 (respectively, loop filter unit 220) may be configured to output loop filter parameters (such as adaptive sample offset information), for example, directly or encoded through the unit of entropy coding 270, such that, for example, a decoder 30 may receive and apply the same loop filter parameters or respective loop filters for decoding.

Temporary Storage of Decoded Images

[00157] The decoded picture temporary store (DPB) 230 may be a memory that stores reference pictures, or in general reference picture data, for encoding video data by the video encoder 20. The DPB 230 may be formed by any of a variety of memory devices, such as dynamic random access memory (DRAM), including synchronous DRAM (SDRAM), magnetoresistive RAM (MRAM), resistive RAM (RRAM), or other types of memory devices. The decoded picture buffer (DPB) 230 may be configured to store one or more filtered blocks 221. The decoded picture buffer 230 may be further configured to store other previously filtered blocks, e.g., previously reconstructed and filtered blocks 221. from the same current image or from different images, e.g. previously reconstructed images, and can provide complete previously reconstructed, i.e. decoded, images (and corresponding reference blocks and samples) and/or a partially reconstructed current image (and reference blocks and corresponding samples), for example, for interprediction. The decoded picture buffer (DPB) 230 may also be configured to store one or more unfiltered reconstructed blocks 215 or, in general, unfiltered reconstructed samples, for example, if the reconstructed block 215 is not filtered by the image filter unit. loop 220 or any other additional processed version of the reconstructed blocks or samples.

Mode Selection (Partitioning and Prediction)

[00158] The mode selection unit 260 comprises partitioning unit 262, interprediction unit 244 and intraprediction unit 254 and is configured to receive or obtain original image data, for example, an original block 201 (current block 201 of the image current 17), and reconstructed image data, e.g. filtered and/or unfiltered reconstructed samples or blocks of the same (current) image and/or of one or a plurality of previously decoded images, e.g. from temporary storage of decoded images 230 or other temporary stores (e.g., line temporary storage, not shown). The reconstructed image data is used as reference image data for prediction, e.g., interprediction or intraprediction, to obtain a prediction block 265 or predictor 265.

[00159] The mode selection unit 260 may be configured to determine or select a partitioning for a current block prediction mode (including no partitioning) and a prediction mode (e.g., an intra- or inter-prediction mode) and generate a corresponding prediction block 265, which is used for the calculation of the residual block 205 and for the reconstruction of the reconstructed block 215.

[00160] Embodiments of the mode selection unit 260 may be configured to select the partitioning and prediction mode (e.g., from those supported by or available to the mode selection unit 260) that provide the best combination or in in other words the minimum residual (minimum residual means best compression for transmission or storage), or a minimum signaling overhead (minimum signaling overhead means best compression for transmission or storage), or which considers or balances both. The mode selection unit 260 may be configured to determine the partitioning and prediction mode based on rate distortion optimization (RDO), i.e., selecting the prediction mode that provides a minimum rate distortion. Terms such as "best", "minimum", "optimal", etc. in this context do not necessarily refer to an overall "best", "minimum", "optimal", etc., but may also refer to the fulfillment of a termination or selection criterion such as a value exceeding or falling below a threshold or other constraints potentially leading to "suboptimal selection" but reducing complexity and processing time.

[00161] In other words, the partitioning unit 262 can be configured to partition the block 201 into smaller block partitions or sub-blocks (which again form blocks), for example, iteratively using quad-tree (QT) partitioning, of binary tree (BT) or triple tree (TT) partitioning or any combination thereof, and to perform, for example, prediction for each of the block partitions or sub-blocks, wherein the mode selection comprises the selection of the tree structure of the partitioned block 201 and the prediction modes are applied to each of the block partitions or sub-blocks.

[00162] In the following, the partitioning (e.g., by partitioning unit 260) and prediction processing (by interprediction unit 244 and intraprediction unit 254) performed by an example video encoder 20 will be explained in more detail.

Partitioning

[00163] The partitioning unit 262 may partition (or separate) a current block 201 into smaller partitions, e.g., smaller blocks of square or rectangular size. These smaller blocks (which can also be called sub-blocks) can be partitioned into even smaller partitions. This is also referred to as tree partitioning or hierarchical tree partitioning, where a root block, for example at root tree level 0 (hierarchy level 0, depth 0), can be recursively partitioned, e.g. partitioned into two or more blocks of a next lower tree level, for example, nodes at tree level 1 (hierarchy level 1, depth 1), where these blocks may be further partitioned into two or more blocks of a next lower level, e.g. example, tree level 2 (hierarchy level 2, depth 2), etc. until partitioning is terminated, for example because a termination criterion is met, for example, a maximum tree depth or minimum block size is reached. Blocks that are not further partitioned are also called leaf blocks or leaf nodes of the tree. A tree that uses two-partitioning is called a binary tree (BT), a tree that uses three-partitioning is called a ternary tree (TT), and a tree that uses four-partitioning is called a quadruple tree (QT). ). In the present disclosure, during interprediction, the coding block is divided into transform blocks when SBT coding tool is applied.

[00164] As mentioned before, the term "block", as used herein, may be a portion, in particular a square or rectangular portion, of an image. With reference to, for example, HEVC and VVC, the block may be or correspond to a coding tree unit (CTU), a coding unit (CU), a prediction unit (PU), and a transform unit ( TU) and/or the corresponding blocks, for example, a coding tree block (CTB), a coding block (CB), a transform block (TB) or prediction block (PB).

[00165] For example, a coding tree unit (CTU) may be or comprise a CTB of luma samples, two corresponding CTBs of chroma samples of an image having three sample matrices, or a CTB of samples of an image monochrome or an image that is encoded using three separate color planes and syntax structures used to encode the samples. Correspondingly, a coding tree block (CTB) can be an NxN block of samples for some value of N such that dividing a component into CTBs is a partitioning. A coding unit (CU) may be or comprise a coding block of luma samples, two corresponding coding blocks of chroma samples of an image having three sample matrices, or a coding block of samples of a monochrome image or an image that is encoded using three separate color planes and syntax structures used to encode the samples. Correspondingly, a coding block (CB) can be an MxN block of samples for some values of M and N so that dividing a CTB into coding blocks is a partitioning.

[00166] In embodiments, for example, according to HEVC, a coding tree unit (CTU) can be separated into CUs using a quadruple tree structure denoted as coding tree. The decision to code an image area using inter-image (temporal) or intra-image (spatial) prediction is made at the CU level. Each CU can be separated into one, two or four PUs according to the PU separation type. Within a PU, the same prediction process is applied and relevant information is transmitted to the decoder based on the PU. After obtaining the residual block by applying the prediction process based on the PU separation type, a CU can be partitioned into transform units (TUs) according to another quad-tree structure similar to the coding tree for the CU.

[00167] In embodiments, for example, in accordance with the latest video coding standard currently under development, which is referred to as Versatile Video Coding (VVC), a quad-tree and binary tree (QTBT) partitioning is used to partition a coding block. In the QTBT block structure, a CU can have a square or rectangular shape. For example, a coding tree unit (CTU) is first partitioned by a quad-tree structure. Quad tree leaf nodes are further partitioned by a binary or ternary (or triple) tree structure. The leaf nodes of the partitioning tree are called coding units (CUs), and this segmentation is used for prediction and transform processing without any additional partitioning. This means that the CU, PU, and TU have the same block size in the QTBT coding block structure. In parallel, multiple partitions, e.g., triple-tree partition has also been proposed to be used in conjunction with the block structure of QTBT.

[00168] In one example, the mode selection unit 260 of the video encoder 20 may be configured to perform any combination of the partitioning techniques described herein.

[00169] As described above, video encoder 20 is configured to determine or select the best or optimal prediction mode from a set of (predetermined) prediction modes. The set of prediction modes may comprise, for example, intraprediction modes and/or interprediction modes.

Intraprediction

[00170] The set of intraprediction modes may comprise 35 different intraprediction modes, for example, non-directional modes such as DC (or average) mode and planar mode, or directional modes, for example, as defined in HEVC, or may comprise 67 intraprediction modes, e.g. non-directional modes such as DC (or mean) mode and planar mode, or directional modes e.g. as defined for VVC.

[00171] The intraprediction unit 254 is configured to use reconstructed samples from neighboring blocks of the same current image to generate an intraprediction block 265 according to an intraprediction mode from the set of intraprediction modes.

[00172] The intraprediction unit 254 (or, in general, the mode selection unit 260) is further configured to output intraprediction parameters (or in general information indicative of the intraprediction mode selected for the block) to the coding unit of entropy 270 in the form of syntax elements 266 for inclusion in the encoded image data 271 (corresponding to encoded image data 21 of Figure 1A), so that, for example, the video decoder 30 can receive and use the parameters of prediction for decoding.

Interpretation

[00173] The set of (or possible) interprediction modes depends on the available reference images (i.e., previous at least partially decoded images, e.g., stored in DBP 230) and other interprediction parameters, e.g., whether the image entire reference image or just a part, for example a search pane area around the current block area, of the reference image is used to search for the best matching reference block, and/or for example if interpolation of pixel is applied, for example, half/semi-pel interpolation, and/or quarter-pel interpolation, or not.

[00174] In addition to the above prediction modes, skip mode and/or direct mode may be applied.

[00175] The interprediction unit 244 may include a motion estimation unit (ME) and a motion compensation unit (MC) (both not shown in Figure 2). The motion estimation unit may be configured to receive or obtain image block 201 (current image block 201 of current image 17) and a decoded image 231, or at least one or a plurality of previously reconstructed blocks, e.g. reconstructed blocks of one or a plurality of other/different previously decoded images 231, for motion estimation. For example, a video sequence may comprise the current image and previously decoded images 231, or in other words, the current image and previously decoded images 231 may be part of or form a sequence of images forming a video sequence.

[00176] Encoder 20 may, for example, be configured to select a reference block from a plurality of reference blocks of the same or different images from the plurality of other images and provide a reference image (or image index of reference) and/or an offset (spatial offset) between the position (x, y coordinates) of the reference block and the current block position as interprediction parameters for the motion estimation unit. This displacement is also called motion vector (MV).

[00177] The motion compensation unit is configured to obtain, for example, receive, an interprediction parameter and perform the interprediction based on or using the interprediction parameter to obtain an interprediction block 265. Motion compensation, performed by the motion compensation unit, may involve fetching or generating the prediction block based on the motion/block vector determined by motion estimation, possibly performing interpolations for subpixel accuracy. Interpolation filtering can generate additional pixel samples from known pixel samples, thereby potentially increasing the number of candidate prediction blocks that can be used to encode an image block. Upon receiving the motion vector for the PU from the current image block, the motion compensation unit can locate the prediction block to which the motion vector points in one of the reference image lists.

[00178] Motion compensation unit may also generate syntax elements associated with the blocks and the video slice for use by the video decoder 30 in decoding the image blocks of the video slice. In the present disclosure, during interprediction, the coding block is divided into transform blocks when sub-block transform (SBT) is enabled (e.g., when SBT coding tool is applied).

Entropy Coding

[00179] The entropy coding unit 270 is configured to apply, for example, an entropy coding algorithm or scheme (e.g., a variable length coding scheme (VLC), a context adaptive VLC scheme (CAVLC) ), an arithmetic coding scheme, a binarization, a context-adaptive binary arithmetic coding (CABAC), syntax-based context-adaptive binary arithmetic coding (SBAC), probability interval partitioning entropy coding (PIPE), or other methodology or entropy coding technique) or offset (without compression) in quantized coefficients 209, interprediction parameters, intraprediction parameters, loop filter parameters, and/or other syntax elements to obtain encoded image data 271 (correspond to image data coded image 21) which can be output via output 272, for example in the form of a coded bit stream 21, so that, for example, video decoder 30 can receive and use the parameters for decoding. The encoded bit stream 21 may be transmitted to the video decoder 30 or stored in a memory for later transmission or retrieval by the video decoder 30. In the present disclosure, some syntax elements such as cu_sbt_flag and cu_sbt_horizontal_flag may be encoded in the encoded bit stream 21. bits 21.

[00180] Other structural variations of video encoder 20 can be used to encode the video stream. For example, a non-transform based encoder 20 may quantize the residual signal directly without the transform processing unit 206 for certain blocks or frames. In another implementation, an encoder 20 may have the quantization unit 208 and the inverse quantization unit 210 combined into a single unit.

Decoder and Decoding Method

[00181] Figure 3 shows an example of a video decoder 30 that is configured to implement the techniques of this present application. Video decoder 30 is configured to receive encoded image data 271 (corresponding to encoded image data 21) (e.g., encoded bit stream 21), e.g., encoded by encoder 20, to obtain a decoded image 331. encoded image data or bitstream comprises information for decoding the encoded image data, e.g., data representing image blocks of an encoded video slice and associated syntax elements.

[00182] In the example of Figure 3, the decoder 30 comprises an entropy decoding unit 304, an inverse quantization unit 310, an inverse transform processing unit 312, a reconstruction unit 314 (e.g., an adder 314) , a loop filter 320, a decoded picture buffer (DBP) 330, an interprediction unit 344, and an intraprediction unit 354. The interprediction unit 344 may be or include a motion compensation unit. The video decoder 30 may, in some examples, perform a decoding pass generally reciprocal to the encoding pass described with respect to the video encoder 20 of Figure 2.

[00183] As explained with respect to the encoder 20, the inverse quantization unit 210, the inverse transform processing unit 212, the reconstruction unit 214, the loop filter 220, the decoded image temporary storage (DPB) 230, the interprediction unit 344 and the intraprediction unit 354 are also referred to as forming the "built-in decoder" of the video encoder 20. Accordingly, the inverse quantization unit 310 may be identical in function to the inverse quantization unit 110, the The inverse transform processing unit 312 may be identical in function to the inverse transform processing unit 212, the reconstruction unit 314 may be identical in function to the reconstruction unit 214, the loop filter 320 may be identical in function to the loop 220 and the temporary storage of decoded images 330 may be identical in function to the temporary storage of decoded images 230. Therefore, the explanations provided for the respective units and functions of the video encoder 20 apply correspondingly to the respective units and functions of the video decoder. video 30.

Entropy Decoding

[00184] The entropy decoding unit 304 is configured to analyze the bit stream 21 (or in encoded image data 271 in general (corresponding to encoded image data 21)) and perform, for example, entropy decoding for the encoded image data 271 (corresponds to encoded image data 21) to obtain, for example, quantized coefficients 309 and/or decoded encoding parameters (not shown in Figure 3), e.g., any or all of the interprediction parameters ( e.g., reference image index and motion vector), intraprediction parameter (e.g., intraprediction mode or index), transform parameters, quantization parameters, loop filter parameters, and/or other syntax elements. The entropy decoding unit 304 may be configured to apply decoding algorithms or schemes corresponding to the encoding schemes as described with respect to the entropy coding unit 270 of the encoder 20. The entropy decoding unit 304 may be further configured to provide interprediction parameters, intraprediction parameter and/or other syntax elements to the mode selection unit 360 and other parameters to other units of the decoder 30. The video decoder 30 may receive the syntax elements at the slice level of video and/or video block level.

Inverse Quantization

[00185] The inverse quantization unit 310 may be configured to receive quantization parameters (QP) (or general information related to inverse quantization) and quantized coefficients from the encoded image data 271 (corresponds to encoded image data 21) (e.g. by analysis and/or decoding, e.g. by entropy decoding unit 304) and apply based on the quantization parameters an inverse quantization on the decoded quantized coefficients 309 to obtain dequantized coefficients 311, which may also be referred to as transform coefficients 311. The inverse quantization process may include using a quantization parameter determined by the video encoder 20 for each block of video in the video slice to determine a degree of quantization and, likewise, a degree of quantization inverse that must be applied.

Inverse Transform

[00186] The inverse transform processing unit 312 may be configured to receive dequantized coefficients 311, also referred to as transform coefficients 311, and to apply a transformation to the dequantized coefficients 311 in order to obtain reconstructed residual blocks 213 in the sample domain. The reconstructed residual blocks 213 may also be referred to as transform blocks 313. The transform may be an inverse transform, e.g., an inverse DCT, an inverse DST, an inverse integer transform, or a conceptually similar inverse transform process. The inverse transform processing unit 312 may be further configured to receive transform parameters or corresponding information from the encoded image data 271 (corresponding to encoded image data 21) (e.g., by analysis and/or decoding, e.g. , per entropy decoding unit 304) to determine the transform to be applied to the dequantized coefficients 311.

Reconstruction

[00187] The reconstruction unit 314 (e.g., adder or adder 314) may be configured to add the reconstructed residual block 313, to the prediction block 365 to obtain a reconstructed block 315 in the sample domain, e.g., by adding the values sample values from the reconstructed residual block 313 and the sample values from the prediction block 365.

Filtering

[00188] The loop filter unit 320 (either in the encoding loop or after the encoding loop) is configured to filter the reconstructed block 315 to obtain a filtered block 321, for example, to smooth pixel transitions or otherwise otherwise, improve video quality. The loop filter unit 320 may comprise one or more loop filters, such as an unblocking filter, an adaptive sample offset (SAO) filter, or one or more other filters, e.g., a bilateral filter, a loop filter. adaptive filter (ALF), a sharpening filter, smoothing filters or collaborative filters, or any combination thereof. Although the loop filter unit 320 is shown in Figure 3 as being a loop filter, in other configurations, the loop filter unit 320 may be implemented as a post-loop filter. In the present disclosure, the improved loop filter, particularly the improved deblocking filter apparatus is provided and will be described in detail later.

Temporary Storage of Decoded Images

[00189] The decoded video blocks 321 of an image are then stored in temporary decoded image storage 330, which stores the decoded images 331 as reference images for subsequent motion compensation for other images and/or for output display, respectively .

[00190] Decoder 30 is configured to output the decoded image 311, for example, through output 312, for presentation or viewing to a user.

Prediction

[00191] The interprediction unit 344 may be identical to the interprediction unit 244 (in particular the motion compensation unit) and the intraprediction unit 354 may be identical to the intraprediction unit 254 in function, and performs division or partitioning decisions and prediction based on the partitioning and/or prediction parameters or respective information received from the encoded image data 271 (corresponding to encoded image data 21) (e.g., by analysis and/or decoding, e.g., by decoding unit of entropy 304). The mode selection unit 360 can be configured to perform prediction (intra- or inter-prediction) per block based on reconstructed images, blocks or respective samples (filtered or unfiltered) to obtain the prediction block 365.

[00192] When the video slice is encoded as an intracoded (I) slice, the intraprediction unit 354 of the mode selection unit 360 is configured to generate the prediction block 365 for an image block of the current video slice with based on a signaled intraprediction mode and data from previously decoded blocks of the current image. When the video image is encoded as an intercoded slice (i.e., B or P), the interprediction unit 344 (e.g., motion compensation unit) of the mode selection unit 360 is configured to produce prediction blocks 365 for a video block of the current video slice based on the motion vectors and other syntax elements received from the entropy decoding unit 304. For interprediction, the prediction blocks can be produced from one of the reference images within one of the reference image lists. The video decoder 30 may construct the reference frame lists, List 0 and List 1, using standard construction techniques based on reference images stored in the DPB 330. The same or similar may be applied to or across modalities using groups of parts (e.g. groups of video parts) and/or parts (e.g. video parts) in addition to or alternatively to slices (e.g. video slices), e.g. a video may be encoded using groups of parts I, P or B and/or parts.

[00193] The 360 mode selection unit is configured to determine the prediction information for a video block of the current video slice by analyzing the motion vectors and other syntax elements, and uses the prediction information to produce the blocks prediction for the current video block being decoded. For example, the mode selection unit 360 uses some of the received syntax elements to determine a prediction mode (e.g., intra- or inter-prediction) used to encode the video blocks of the video slice, a type of inter-prediction slice ( for example, slice B, slice P, or slice GPB), construction information for one or more of the reference image lists for the slice, motion vectors for each block of intercoded video in the slice, interprediction status for each block of encoded video of the slice, and other information to decode the video blocks in the current video slice. The same or similar may be applied to or across embodiments using groups of parts (e.g. video part groups) and/or blocks (e.g. video parts), in addition to or alternatively to slices (e.g. video slices ), for example, a video can be encoded using I, P, or B tile groups and/or tiles.

[00194] Embodiments of the video decoder 30, as shown in Figure 3, may be configured to partition and/or decode the image using slices (also referred to as video slices), wherein an image may be partitioned into or decoded using one or more slices (typically non-overlapping), and each slice may comprise one or more blocks (e.g., CTUs).

[00195] Embodiments of the video decoder 30, as shown in Figure 3, may be configured to partition and/or decode the image using groups of parts (also referred to as video part groups) and/or parts (also referred to as video tiles), wherein an image may be partitioned into or decoded using one or more groups of (typically non-overlapping) tiles, and each group of tiles may comprise, for example, one or more blocks (e.g., CTUs) or one or more pieces, wherein each piece, for example, may be rectangular in shape and may comprise one or more blocks (e.g., CTUs), e.g., full or fractional blocks.

[00196] Other variations of video decoder 30 can be used to decode encoded image data 271 (corresponds to encoded image data 21). For example, the decoder 30 may produce the output video stream without the loop filtering unit 320. For example, a non-transform based decoder 30 may inverse quantize the residual signal directly without the inverse transform processing unit 312 to certain blocks or frames. In another implementation, the video decoder 30 may have the inverse quantization unit 310 and the inverse transform processing unit 312 combined into a single unit.

[00197] It should be understood that, in the encoder 20 and the decoder 30, a processing result of a current step may be further processed and then sent to the next step. For example, after interpolation filtering, motion vector derivation, or loop filtering, an additional operation such as Cut or offset can be performed on the processing result of interpolation filtering, motion vector derivation, or loop filtering.

[00198] It should be noted that additional operations may be applied to current block-derived motion vectors (including but not limited to affine mode control point motion vectors, sub-block motion vectors in affine modes, planar and ATMVP, temporal motion vectors, and so on). For example, the motion vector value is restricted to a predefined range according to its representation bit. If the motion vector representation bit is bitDepth, then the range is -2 A (bitDepth-1) ~ 2 A (bitDepth-1) - 1, where “A” means exponentiation. For example, if bitDepth is set equal to 16, the range is -32768 ~ 32767; if bitDepth is set equal to 18, the range is -131072 ~ 131071. For example, the value of the derived motion vector (e.g. the MVs of four 4 x 4 sub-blocks within an 8 x 8 block) is restricted such that the maximum difference between the integer parts of the four MVs of the 4 x 4 sub-block is no more than N pixels, with a maximum of 1 pixel.

[00199] Figure 4 is a schematic diagram of a video encoding device 400 in accordance with an embodiment of the disclosure. The video encoding device 400 is suitable for implementing the disclosed embodiments as described herein. In one embodiment, the video encoding device 400 may be a decoder, such as video decoder 30 of Figure 1A, or an encoder, such as video encoder 20 of Figure 1A.

[00200] The video encoding device 400 comprises ingress ports 410 (or input ports 410) and receiver units (Rx) 420 for receiving data; a processor, logical unit, or central processing unit (CPU) 430 for processing the data; transmitting units (Tx) 440 and egress ports 450 (or output ports 450) for transmitting the data; and a memory 460 for storing the data. The video encoding device 400 may also comprise optical-to-electrical (OE) components and electrical-to-optical (EO) components coupled to the ingress ports 410, the receiver units 420, the transmitter units 440, and the egress ports 450 to egress. or ingress of optical or electrical signals.

[00201] Processor 430 is implemented by hardware and software. Processor 430 may be implemented as one or more CPU chips, cores (e.g., as a multi-core processor), FPGAs, ASICs, and DSPs. The processor 430 is in communication with the ingress ports 410, the receiving units 420, the transmitting units 440, egress ports 450, and memory 460. The processor 430 comprises an encoding module 470. The encoding module 470 implements the embodiments disclosures described above. For example, the encoding module 470 implements, processes, prepares or provides the various encoding operations. The inclusion of the encoding module 470 therefore provides a substantial improvement to the functionality of the video encoding device 400 and effects a transformation of the video encoding device 400 to a different state. Alternatively, encoding module 470 is implemented as instructions stored in memory 460 and executed by processor 430.

[00202] Memory 460 may comprise one or more disks, tape drives, and solid state drives and may be used as an overflow data storage device, to store programs when such programs are selected for execution, and to store instructions and data that is read during program execution. Memory 460 may be, for example, volatile and/or non-volatile, and may be a read-only memory (ROM), random access memory (RAM), ternary content addressable memory (TCAM), and/or access memory static random (SRAM).

[00203] Figure 5 is a simplified block diagram of an apparatus 500 that can be used as either or both the source device 12 and the destination device 14 of Figure 1A according to an exemplary embodiment.

[00204] A processor 502 in apparatus 500 may be a central processing unit. Alternatively, processor 502 may be any other type of device, or multiple devices, capable of manipulating or processing information now existing or developed in the future. Although the disclosed implementations can be implemented with a single processor, as shown, for example, processor 502, advantages in speed and efficiency can be achieved by using more than one processor.

[00205] A memory 504 in apparatus 500 may be a read-only memory device (ROM) or a random access memory device (RAM) in one implementation. Any other suitable type of storage device may be used as memory 504. Memory 504 may include code and data 506 that are accessed by processor 502 using a bus 512. Memory 504 may further include an operating system 508 and application programs 510, application programs 510 including at least one program that allows processor 502 to perform the methods described herein. For example, application programs 510 may include applications 1 through N, which further include a video encoding application that performs the methods described herein.

[00206] Apparatus 500 may also include one or more output devices, such as a display screen 518. Display screen 518 may be, in one example, a touch-sensitive display screen that combines a display screen with a touch-sensitive element that is operable to detect touch inputs. Display screen 518 may be coupled to processor 502 via bus 512.

[00207] Although represented here as a single bus, bus 512 of apparatus 500 may be composed of multiple buses. Furthermore, secondary storage 514 may be directly coupled to other components of apparatus 500 or may be accessed via a network and may comprise a single integrated unit, such as a memory card, or multiple units, such as multiple memory cards. The apparatus 500 can thus be implemented in a wide variety of configurations.

Combined Interprediction-Intraprediction (CIIP)

[00208] Conventionally, a coding unit is either intrapredicted (i.e., using the reference samples in the same image) or interpredicted (i.e., using the reference samples in other images). Combined interprediction-intraprediction combines these two prediction approaches. Therefore, it is also sometimes called combined interprediction-intraprediction (CIIP). When combined interprediction-intraprediction is enabled, the intrapredicted and interpredicted samples are weighted, and the final prediction is derived as the weighted average of the samples.

[00209] A flag, CIIP flag, is used to indicate when a block is applied with combined interprediction-intraprediction.

[00210] The Sub-Block Transform (SBT) coding tool partitions (i.e., separates or divides) an interprediction block (i.e., a short intercoding block for a current coding block that is encoded in the interprediction) in two transform blocks and performs the transform only for one of the transform blocks, but not the other. The two transform blocks can be symmetric (i.e. two transform blocks of the same size) or asymmetric (i.e. two transform blocks with the same width but height of 1:3, for example, or with the same height , but with a width of 1:3, for example). This partial transform can result in block artifact along the boundaries between the two transform blocks. However, these boundaries were not considered to be filtered in the prior art, which compromises the subjective quality when SBT is enabled.

[00211] An improved filtering process is proposed to reduce the block artifact of transform block boundaries caused by SBT. When detecting boundaries that would be considered filtered, internal boundaries between transform blocks caused by SBT are taken into account. Furthermore, the prior art only considers boundaries that are superimposed on an 8 x 8 grid. In the invention, even if an internal SBT boundary is not aligned with the 8 x 8 grid when an asymmetric partitioning (i.e., separation or division ) is applied, the internal boundary would be considered as a filtering candidate. By also filtering the internal boundaries of SBT, the block artifact caused by SBT is reduced.

[00212] A block 600 applied with CIIP can be further divided into several sub-blocks, as shown in Figure 6. In Figure 6, all sub-block boundaries within a CU are applied with combined interprediction-intraprediction (CIIP) . In one example, its subblocks 601 are derived by dividing the block in the horizontal direction, with each subblock having the same width as the original block but U as high as the original block.

[00213] In one example, its sub-blocks 602 are derived by dividing the block in the vertical direction, with each sub-block having the same height as the original block, but U of the width of the original block. In the example shown in Figure 6, the subpartitions and corresponding boundaries with the vertical partition 602 are labeled. Here, intrablock 600 is divided into four subpartitions, namely sub0, sub1, sub2 and sub3. Three subpartition boundaries are labeled, i.e. subpartition A boundary between subpartition 0 and 1, subpartition B boundary between subpartition 1 and 2, subpartition C boundary between subpartition 2 and 3, similar definition can be used in horizontal partition example 601.

[00214] Blocking artifacts can be introduced due to CIIP prediction, as it involves results with intraprediction, which generally has more residual signals. Blocking artifacts not only occur at CIIP block boundaries, but also at sub-block edges within a CIIP block, such as the vertical sub-block edge A, B, C in Figure 6. The sub-block edges -horizontal blocks can be identified correspondingly.

[00215] Although block artifacts may occur at CIIP boundaries and at sub-block boundaries within CIIP blocks, the distortion caused by these two boundaries may be different, and different boundary strengths may be required.

[00216] Sub-block edges can be caused by CIIP itself, for example, if the intraprediction mode of a CIIP block is a horizontal mode, a vertical partition shown in Figure 6 is applied, resulting in three sub-blocks .

[00217] As shown in Figure 7, in order to reduce block artifacts, subblock boundaries are filtered by deblocking after horizontally partitioning a coding block 700 into subblocks 701 or after vertically partitioning a coding block 700 into subblocks 702. Figure 7 shows the deblocking of all subblock edges within a CU applied with combined interprediction-intraprediction (CIIP).

[00218] Figure 8 shows unlocking of all sub-block TU boundaries within a CU that overlaps (aligned with) an 8 x 8 sample grid that does not begin at the top left sample of the CU, in accordance with An example. As shown in Figure 8, after horizontally partitioning a coding block 800 into subblocks 801 or after vertically partitioning a coding block 800 into subblocks 802, only the subblock boundaries that overlap a 8 x 8 sample grid are unlocked and the rest of the sub-block borders are not unlocked. This has the advantage of reducing computational complexity, as only some of the edges are unlocked.

[00219] Another alternative is shown in Figure 9. Figure 9 shows unblocking of all sub-block edges within a CU that overlaps a 4 x 4 sample grid. In this case, after horizontal partitioning of a block of coding block 900 into subblocks 901 or after vertically partitioning a coding block 900 into subblocks 902, all subblock boundaries that overlap a 4 x 4 sample grid are unblocked.

[00220] Figure 10 shows the case when the sub-block size is < 8 samples orthogonally in the unblocking direction, then a weak filter that uses only 3 samples in the decision and that modifies one sample is used. An example in Figure 6 using vertical partitioning, if W has 16 samples, then each sub-block will be 4 samples wide. In this case, as shown in Figure 10, a weak filter that modifies only up to a sample 10314 or 10331 along the subblock boundaries 1032 between the subblock 1031 and the subblock 1033 can be used. In the example shown in Figure 10, filtering is performed on each row of subblocks 1031, 1033 that is perpendicular and adjacent to the subblock boundary 1032 between subblock 1031 and subblock 1033, for example. As shown in Figure 10, a weak filter that modifies only up to one sample 1108 or 10311 along the edge 1020 between the neighboring block 1010 and the current block 1030 can be used. In another example shown in Figure 10, filtering is performed on each row of subblock 1031 or neighboring block 1010 that is perpendicular to and adjacent to the edge 1020 between neighboring block 1010 and subblock 1031 of block 1030, for example.

[00221] However, sub-block edges can also be caused by TU size limitations. In VTM3.0, the largest TU size is 64 x 64 samples. If a CU 1100 has 128 x 128 samples, then it will be divided into 4 TUs 1101, resulting in 4 TU boundaries 1102, shown as in Figure 11. When the maximum TU size is 64, a CU with combined interprediction-intraprediction is 128 x 128, the CU is divided into four Tus 1101, the transform is applied at the granularity 64 x 64. TU 1102 boundaries highlighted as dashed lines need to be unblocked.

[00222] Figure 12 shows a coding unit 1200 applied with CIIP, and which is further divided into multiple transform units 1201. The TU boundaries 1202 highlighted as dashed lines need to be unlocked.

[00223] Figure 13 illustrates unlocking of all sub-block TU boundaries 1302 between TUs 1301 within a CU 1300 that overlap (are aligned with) an 8 x 8 sample grid from the top left sample of the CU1300.

TU Boundaries Within a Coding Unit

[00224] When a certain coding tool (e.g., sub-block transform, SBT) is applied, edges of TU 1402 between TUs 1401 may occur within a CU 1400, as shown in Figure 14. A coding unit 1400 is further divided into multiple transform units 1401 according to sub-block transform coding tool. In such cases, these internal TU edges 1402 within an encoding unit 1400 may also need to be unlocked.

[00225] When SBT is used for an intercoded CU 1400, the SBT type and SBT position information are signaled in the bit stream. There are two types of SBT and two positions of SBT, as shown in Figure 14. For SBT-V (or SBT-H), the width (or height) of TU can be equal to half the width (or height) of CU or 1/4 the width (or height) of CU, resulting in 2:2 separation or 1:3/3:1 separation. 2:2 separation is like a binary tree (BT) separation, while 1:3 separation /3:1 is like an asymmetric binary tree (ABT) split. In ABT separation, only the small region contains the non-zero residue. If a dimension of a CU is 8 in luma samples, 1:3/3:1 separation along that dimension is not allowed. There are a maximum of 8 SBT modes for a CU.

[00226] Position-dependent transform core selection is applied to luma transform blocks in SBT-V and SBT-H (chroma TB always using DCT-2). The two positions of SBT-H and SBT-V are associated with different kernel transforms. More specifically, the horizontal and vertical transforms for each SBT position are specified in Figure 14. For example, the horizontal and vertical transforms for SBT-V position 0 are DCT-8 and DST-7, respectively. When one side of the residual TU 1401 is greater than 32, the transform for both dimensions is defined as DCT-2. Therefore, the sub-block transform jointly specifies the separation into pieces of TU, cbf, and horizontal and vertical kernel transform type of a residual block.

[00227] A maxSbtSize variable is flagged in SPS to specify the maximum CU size to which SBT can be applied. In the VTM7 reference software, for HD and 4K sequences, maxSbtSize is set to 64 by the encoder; for other lower resolution strings, maxSbtSize is set to 32.

[00228] SBT is not applied to CU coded with combined inter-intra mode or TPM mode.

[00229] Similarly, Figure 15 shows a coding unit 1500 that is further divided into multiple transform units 1501 (A, B, C) according to the residual quadruple tree (RQT) as sub-block transform.

[00230] In the remainder of the application, the following terminology is used: CIIP blocks: the coding blocks that are predicted by applying CIIP prediction.

[00231] Intra blocks: the coding blocks that are predicted by applying intraprediction, but not CIIP prediction.

[00232] Inter blocks: the coding blocks that are predicted by the interprediction application, but not the CIIP prediction.

Unlock Filter and Boundary Force

[00233] The invention, in particular as described above in the first and second aspects, includes carrying out an unblocking filtering process for transform block boundary between a first transform block and a second transform block at least based on the value of the boundary force parameter. The boundary strength parameter is further described and defined below (see Table 1).

[00234] Video coding schemes such as HEVC and VVC are designed according to the successful principle of block-based hybrid video coding. Using this principle, an image is first partitioned into blocks and then each block is predicted using intra-image or inter-image prediction. These blocks are encoded relatively from neighboring blocks and approximate the original signal with some degree of similarity. Since the coded blocks only approximate the original signal, the difference between the approximations can cause discontinuities at the prediction and transform block boundaries. These discontinuities are smoothed out by the deblocking filter.

[00235] The decision to filter a block boundary uses bitstream information such as prediction modes and motion vectors. Some encoding conditions are more likely to create strong block artifacts, which are represented by a variable called the boundary strength (Bs or BS) that is assigned to each block boundary and is determined as in Table 1. Table 1

[00236] Unblocking is only applied to block boundaries with Bs greater than zero for a luma component and Bs greater than 1 for chroma components. Higher values of Bs allow stronger filtering using higher cutoff parameter values. The derivation conditions of Bs reflect the probability that the strongest block artifacts appear at intrapredicted block boundaries.

[00237] Typically, the two adjacent blocks 1601, 1602 of a boundary are labeled as P and Q, as shown in Figure 16. The figure represents the case of a vertical boundary. If a horizontal boundary is considered, Figure 16 should be rotated 90 degrees clockwise, where P would be at the top and Q at the bottom.

[00238] The method according to the first aspect of the invention is illustrated in the flowchart of Figure 17. The method is an unlocking method, for unlocking a transform block boundary within a coding block in an image coding and/or or image decoding, wherein the coding block is coded in interprediction mode and the coding block is divided into transform blocks comprising a first transform block and a second transform block that is adjacent to the first transform block; wherein the method comprises a step 1701 of determining when the boundary between the first transform block and the second transform block is a transform block boundary and at least one of the first transform block and the second transform block has a or more non-zero transform coefficients, a value of a boundary strength (BS) parameter for the boundary between the first transform block and the second transform block to be a first value; and other steps 1702 of performing deblocking filtering process for the boundary between the first transform block and the second transform block at least based on the value of the boundary strength parameter.

[00239] The method according to the second aspect of the invention is illustrated in the flowchart of Figure 18. The method is an unlocking method, for unlocking block boundaries within a coding block in an image encoding and/or image decoding. image, wherein the coding block is coded in interprediction mode and the coding block is divided into transform blocks comprising a first transform block and a second transform block that is adjacent to the first transform block; wherein the method comprises a step 1801 of: in response to a determination that a transform block boundary between the first transform block and the second transform block should be filtered, determining, when the boundary between the first transform block and the second transform block is a sub-block transform boundary, SBT, and at least one of the first transform block and the second transform block has one or more non-zero transform coefficients, a value of a transform parameter boundary force for the boundary between the first transform block and the second transform block to be a first value; and a step 1802 of: performing deblocking filtering process for the transform block boundary between the first transform block and the second transform block at least based on the value of the boundary strength parameter.

[00240] Figure 19 illustrates a device according to the third aspect. The device 1900 comprises an deblocking filter 1901 configured to deblock a transform block boundary within a coding block, wherein the coding block is coded (predicted) in interprediction mode and the coding block comprises transform blocks ( as such, the coding block is divided (separated) into transform blocks during the interprediction process, for example, when the sub-block transform is enabled, the current coding unit is divided into two transform units) comprising a first transform block and a second transform block that is adjacent to the first transform block. The deblocking filter 1901 comprises a determination module 1902 configured to determine when the boundary between the first transform block and the second transform block is a transform block boundary and at least one of the first transform block and the second transform block of transform has one or more non-zero transform coefficients, a value of a boundary strength parameter for the boundary between the first transform block and the second transform block to be a first value; and an unblocking filtering module 1903 configured to perform deblocking filtering process up to the boundary between the first transform block and the second transform block at least based on the first value of the boundary strength parameter.

[00241] In one example, the deblocking filter 1901 may correspond to the loop filter 220 in Figure 2. In another example, the deblocking filter 1901 may correspond to the loop filter 320 in Figure 3. Correspondingly, in one example, a An example device structure 1900 may correspond to encoder 200 in Figure 2. In another example, an example device structure 1900 may correspond to decoder 300 in Figure 3.

[00242] Figure 20 illustrates a device according to the fourth aspect. Device 2000 comprises an unlocking filter 2001 configured to unlock block boundaries within a coding block (coding unit), wherein the coding block is coded (predicted) in interprediction mode (in particular, the coding block is encoded in a sub-block transform mode, SBT) and the coding block (an interpredicted coding block is divided (separated) into transform blocks in the interprediction process, for example, when the sub-block transform is enabled, the current coding unit is divided into two or more transform units) comprising a first transform block and a second transform block that is adjacent to the first transform block (e.g., transform blocks containing p0 and q0 are adjacent in the vertical or horizontal direction). The deblocking filter 2001 comprises a determination module 2002 configured to determine, when the boundary between the first transform block and the second transform block is a sub-block transform boundary, SBT, and at least one of the first transform block transformed and the second transform block has one or more non-zero transform coefficients, a value of a boundary strength parameter for the boundary between the first transform block and the second transform block to be a first value as such, in response to a determination that a transform block boundary between the first transform block and the second transform block is to be filtered; and an unblocking module 2003 configured to perform an unblocking filtering process for the transform block boundary between the first transform block and the second transform block at least based on the value of the boundary strength parameter.

[00243] In one example, the deblocking filter 2001 may correspond to the loop filter 220 in Figure 2. In another example, the deblocking filter 2001 may correspond to the loop filter 320 in Figure 3. Correspondingly, in one example, a example device structure 2000 may correspond to encoder 200 in Figure 2. In another example, an example device structure 2000 may correspond to decoder 300 in Figure 3.

[00244] A Versatile Video Coding (Draft 3) reference document is defined as Draft VVC 3.0 and can be found at the following link: http://phenix.it-sudparis.eu/jvet/doc_end_user/documents/12_Macao/wg11 /JVET-L1001-v13.zip.

[00245] In an example, according to 8.6.2.5 of Draft VVC 3.0 v9, 8.6.2.5 Boundary Filtering Force Derivation Process the inputs to this process are: - a recPicture image sample matrix, - a location (xCb, yCb) specifying the top left sample of the current encoding block relative to the top left sample of the current image, - an nCbW variable specifying the width of the current encoding block, - an nCbH variable specifying the height of the encoding block current, - an edgeType variable specifying whether a vertical (EDGE_VER) or horizontal (EDGE_HOR) edge is filtered, - a two-dimensional (nCbW) x (nCbH) edgeFlags array.

[00246] Output of this process is a two-dimensional (nCbW) x (nCbH) bS matrix specifying the boundary filtering strength.

[00247] The variables xDi, yDj, xN and yN are derived as follows: - if edgeType is equal to EDGE_VER, xDi is set equal to (i << 3), yDj is set equal to (j << 2), xN is defined equal to Max (0, (nCbW / 8) - 1) and yN is defined equal to (nCbH / 4) — 1; - otherwise (edgeType is equal to EDGE_HOR), xDi is set equal to (i << 2), yDj is set equal to (j << 3), xN is set equal to (nCbW / 4) - 1 and yN is set equal to Max (0, (nCbH / 8) - 1).

[00248] For xDi with i = 0..xN and yDj with j = 0..yN, the following applies: - if edgeFlags [xDi] [yDj] is equal to 0, the variable bS [xDi] [yDj ] will be set equal to 0; - otherwise, the following applies: - sample values p0 and q0 are derived as follows: - if edgeType is equal to EDGE_VER, p0 is set equal to recPicture [xCb + xDi - 1] [yCb + yDj ] and q0 is set equal to recPicture [xCb + xDi] [yCb + yDj]; - otherwise (edgeType is equal to EDGE_HOR), p0 is set equal to recPicture [xCb + xDi] [yCb + yDj - 1] and q0 is set equal to recPicture [xCb + xDi] [yCb + yDj].

[00249] The variable bS [xDi] [yDj] is derived as follows: - if the sample p0 or q0 is in the coding block of a coding unit coded with intraprediction mode, bS [xDi] [yDj] is defined equal to 2; - otherwise, if the block edge is also a transform block edge and the sample p0 or q0 is in a transform block that contains one or more non-zero transform coefficient levels, bS [xDi] [yDj ] is equal to 1; - otherwise, if one or more of the following conditions are true, bS [xDi] [yDj] is set equal to 1: - for the prediction of the coding sub-block containing the sample p0, different reference images or a number different motion vectors are used for the prediction of the coding sub-block containing the sample q0.

[00250] NOTE 1 - The determination of whether the reference images used for the two coding sub-blocks are the same or different is based solely on which images are referenced, without regard to whether a prediction is formed using an index in the list of reference images 0 or an index in the list of reference images 1, and also without taking into account whether the position of the index within a list of reference images is different.

[00251] NOTE 2 - The number of motion vectors that are used for the prediction of a coding sub-block with top left sample coverage (xSb, ySb), is equal to PredFlagL0 [xSb] [ySb] + PredFlagL1 [ xSb] [ySb].

[00252] A motion vector is used to predict the coding sub-block containing sample p0, and a motion vector is used to predict the coding sub-block containing sample q0, and the absolute difference between the horizontal component or vertical of the motion vectors used is greater than or equal to 4 in quarter-luma sample units.

[00253] Two motion vectors and two different reference images are used to predict the coding sub-block containing sample p0, two motion vectors for the same two reference images are used to predict the coding sub-block containing the sample q0 and the absolute difference between the horizontal or vertical component of the two motion vectors used in the prediction of the two coding sub-blocks for the same reference image is greater than or equal to 4 in quarter luma sample units.

[00254] Two motion vectors for the same reference image are used to predict the coding sub-block containing the sample p0, two motion vectors for the same reference image are used to predict the coding sub-block containing the sample q0 and both of the following conditions are true: - the absolute difference between the horizontal or vertical component of the list 0 motion vectors used in the prediction of the two coding sub-blocks is greater than or equal to 4 in the quarter-luma samples , or the absolute difference between the horizontal or vertical component of the list 1 motion vectors used in the prediction of the two coding subblocks is greater than or equal to 4 in quarter-luma sample units; - the absolute difference between the horizontal or vertical component of the list motion vector 0 used in the prediction of the coding sub-block containing the sample p0 and the list motion vector 1 used in the prediction of the coding sub-block containing the sample q0 is greater than or equal to 4 in units of quarter luma samples, or the absolute difference between the horizontal or vertical component of the list 1 motion vector used in the prediction of the coding subblock containing sample p0 and the vector of list movement 0 used in predicting the coding sub-block containing sample q0 is greater than or equal to 4 in quarter-luma sample units.

[00255] Otherwise, the variable bS [xDi] [yDj] is set equal to 0.

[00256] Additionally, the VVC documentation refers to "coding tree semantics" and "Subblock Transform (SBT)" as follows: 7.4.9.4 Coding tree semantics cu_sbt_flag equals 1 specifies that for the current coding unit, the sub-block transform is used. cu_sbt_flag equal to 0 specifies that for the current encoding unit, the subblock transform is not used.

[00257] When cu_sbt_flag is not present, its value is considered equal to 0.

[00258] NOTE -: when sub-block transform is used, one coding unit is separated into two transform units; one transformation unit has residual data, the other has no residual data.

[00259] cu_sbt_horizontal_flag equal to 1 specifies that the current coding unit is separated horizontally into 2 transform units. cu_sbt_horizontal_flag [x0] [y0] equal to 0 specifies that the current encoding unit is separated vertically into 2 transform units.

[00260] According to an embodiment of the present application, if a CU is divided into multiple sub-blocks and the transform is applied at the sub-block granularity, then the sub-block TU boundary within a CU must be unblocked . This modality proposes to unlock the sub-block TU boundary within a CU in a suitable manner.

[00261] In this embodiment, for a boundary with two sides, as shown in Figure 16 (where the spatially adjacent blocks on each side are denoted as block P and block Q), the boundary force is derived as follows: • if both blocks P and Q are in the same CU and the boundary between block P and block Q is a sub-block TU boundary, as shown in Figure 14 or Figure 15, then the boundary strength parameter of said boundary is defined according to the following condition: ■ if at least one of the adjacent blocks P and Q has at least one non-zero transform coefficient, then the boundary strength parameter of said boundary is set equal to a non-zero value , for example, 1; ■ otherwise, if both blocks P and Q do not have non-zero transform coefficients, then the boundary strength parameter of this boundary is set equal to 0; • otherwise, the boundary force is derived as in the example above, i.e. the boundary force derivation process as defined in section 8.6.2.5 of Draft VVC 3.0 v9; • the pixel samples included in the Q block and the P block are filtered by applying an unblocking filter according to the determined boundary strength.

[00262] In an example, when sub-block TU boundaries are aligned with an N x M grid, these sub-block TU boundaries are unblocked, as defined in the above embodiment. In one example, N is 8, M is 8. In another example, N is 4 and M is 4. Otherwise (if these sub-block TU boundaries are not aligned with an N x M grid), they will not be unlocked.

[00263] In an example, for a CU whose upper left position is not aligned with an 8 x 8 grid (as shown in Figure 13), sub-block TU boundaries that are aligned with said 8 x 8 grid are unlocked, as defined in the modality above. Otherwise (these sub-block TU boundaries are not aligned with the 8 x 8 grid), they are not unblocked.

[00264] In an example, for a CU whose upper left position is aligned with an 8 x 8 grid (as shown in Figure 13), sub-block TU boundaries that are aligned with said 8 x 8 grid are unlocked , as defined in the modality above. Otherwise (these sub-block TU boundaries are not aligned with the 8 x 8 grid), they are not unblocked.

[00265] In one example, regardless of the position of sub-block TU boundaries, all sub-block TU boundaries within a CU are unlocked, as defined in the above embodiment.

[00266] The invention provides the following additional embodiments: a coding method, wherein the coding includes decoding or encoding, and the method comprises: dividing a coding unit or a coding block into at least two sub-blocks comprising a first sub-block and a second sub-block; and when a boundary between the first sub-block and the second sub-block is aligned with a sub-block transform unit boundary, setting a value of a boundary strength parameter corresponding to the boundary between the first sub-block and the second sub-block, according to one or more transform coefficients of the first sub-block or one or more transform coefficients of the second sub-block; wherein the first subblock and the second subblock are transform blocks.

[00267] The coding unit or coding block can be divided in a horizontal or vertical direction.

[00268] When a value of one or more transform coefficients of the first sub-block is not equal to zero, or when a value of one or more transform coefficients of the second sub-block is not equal to zero, the value of the parameter of boundary force can be set to a first value. The first value may not be equal to zero, in particular, the first value may be 1 or 2.

[00269] When all transform coefficient values of the first sub-block are equal to zero, and all transform coefficient values of the second sub-block are equal to zero, the value of the boundary force parameter can be set as a second value. The second value can be zero.

[00270] An encoder (20) may comprise a set of processing circuits to carry out the method described above. A decoder (30) may comprise a set of processing circuits for carrying out the method described above.

[00271] A computer program may comprise program code for carrying out the method described above.

[00272] ACCORDING TO AN ASPECT, A DECODER MAY COMPRISE: ONE OR MORE PROCESSORS; AND A NON-TRANSIENT COMPUTER READABLE STORAGE MEDIUM COUPLED TO THE PROCESSORS AND STORING PROGRAMMING FOR EXECUTION BY THE PROCESSORS, WHICH THE PROGRAMMING, WHEN EXECUTED BY THE PROCESSORS, CONFIGURES THE DECODER TO PERFORM THE METHOD DESCRIBED ABOVE.

[00273] According to one aspect, an encoder may comprise: one or more processors; and a non-transitory computer-readable storage medium coupled to the processors and storing programming for execution by the processors, wherein the programming, when executed by the processors, configures the encoder to perform the method described above.

[00274] The following is an explanation of the applications of the encoding method as well as the decoding method as shown in the above-mentioned embodiments and a system that uses them.

[00275] Figure 21 is a block diagram showing a content delivery system 3100 for performing content delivery service. This content delivery system 3100 includes capture device 3102, terminal device 3106, and optionally includes display screen 3126. Capture device 3102 communicates with terminal device 3106 via communication link 3104. The communication link may include the communication channel 13 described above. The 3104 communication link includes, but is not limited to, WIFI, Ethernet, cable, wireless (3G/4G/5G), USB, or any type of combination thereof, or the like.

[00276] The capture device 3102 generates data, and can encode the data by the encoding method as shown in the above embodiments. Alternatively, the capture device 3102 may distribute the data to a streaming server (not shown in the Figures), and the server encodes the data and transmits the encoded data to the terminal device 3106. The capture device 3102 includes, but is not limited to, limited to camera, smartphone or pad, computer or laptop, video conferencing system, PDA, vehicle-mounted device, or a combination of any of them, or the like. For example, capture device 3102 may include source device 12 as described above. When the data includes video, the video encoder 20 included in the capture device 3102 can actually perform video encoding processing. When the data includes audio (i.e., voice), an audio encoder included in the capture device 3102 may actually perform audio encoding processing. For some practical scenarios, the capture device 3102 distributes the encoded video and audio data by multiplexing them together. For other practical scenarios, for example, in video conferencing system, the encoded audio data and encoded video data are not multiplexed. The capture device 3102 distributes the encoded audio data and the encoded video data to the terminal device 3106 separately.

[00277] In the content delivery system 3100, the terminal device 310 receives and reproduces the encoded data. The terminal device 3106 may be a device capable of receiving and retrieving data, such as a smartphone or Pad 3108, computer or laptop 3110, network video recorder (NVR) / digital video recorder (DVR) 3112, TV 3114, set-top box (STB) 3116, video conferencing system 3118, video surveillance system 3120, personal digital assistant (PDA) 3122, vehicle-mounted device 3124, or a combination of any of them, or the like, capable of decoding the aforementioned encoded data. For example, terminal device 3106 may include destination device 14 as described above. When the encoded data includes video, the video decoder 30 included in the terminal device is prioritized to perform video decoding. When the encoded data includes audio, an audio decoder included in the terminal device is prioritized to perform audio decoding processing.

[00278] To a terminal device with its display screen, e.g., smartphone or Pad 3108, computer or laptop 3110, network video recorder (NVR)/digital video recorder (DVR) 3112, TV 3114, personal digital assistant (PDA) 3122 or vehicle-mounted device 3124, the terminal device can feed the decoded data to its display screen. For a terminal device equipped with no display screen, e.g., STB 3116, video conferencing system 3118, or video surveillance system 3120, an external display screen 3126 is coupled thereto for receiving and displaying the decoded data.

[00279] When each device in this system performs encoding or decoding, the image encoding device or the image decoding device as shown in the above-mentioned embodiments can be used.

[00280] Figure 22 is a diagram showing a structure of an example terminal device 3106. After the terminal device 3106 receives the stream from the capture device 3102, the protocol processing unit 3202 analyzes the stream transmission protocol . The protocol includes but is not limited to Real-Time Streaming Protocol (RTSP), Hypertext Transfer Protocol (HTTP), HTTP Live Streaming Protocol (HLS), MPEG-DASH, Real-Time Transport Protocol (RTP ), Real-Time Messaging Protocol (RTMP), or any type of combination thereof, or similar.

[00281] After the protocol procedure unit 3202 processes the stream, the stream file is generated. The file is output to a demultiplexing unit 3204. The demultiplexing unit 3204 can separate the multiplexed data into encoded audio data and encoded video data. As described above, for some practical scenarios, for example, in the video conferencing system, the encoded audio data and encoded video data are not multiplexed. In this situation, the encoded data is transmitted to the video decoder 3206 and audio decoder 3208 other than through the demultiplexing unit 3204.

[00282] Through demultiplexing processing, video elementary stream (ES), audio ES and, optionally, subtitles are generated. The video decoder 3206, which includes the video decoder 30 as explained in the above-mentioned embodiments, decodes the video ES by the decoding method as shown in the above-mentioned embodiments to generate video frame, and feeds this data to the synchronous unit 3212 The audio decoder 3208 decodes the audio IO to generate audio frame and feeds this data to the synchronous unit 3212. Alternatively, the video frame can be stored in temporary storage (not shown in Figure 22) before being fed to it. it to the synchronous unit 3212. Likewise, the audio frame can be stored in temporary storage (not shown in Figure 22) before feeding it to the synchronous unit 3212.

[00283] The synchronous unit 3212 synchronizes the video frame and the audio frame, and provides the video/audio to a video/audio display screen 3214. For example, the synchronous unit 3212 synchronizes the presentation of video information and audio. Information can be encoded in syntax using timestamps relating to the presentation of encoded audio and visual data and timestamps relating to the delivery of the data stream itself.

[00284] If the subtitle is included in the stream, the subtitle decoder 3210 decodes the subtitle, and synchronizes it with the video frame and the audio frame, and provides the video/audio/subtitle to a video/audio display screen / caption 3216.

[00285] The present invention is not limited to the above-mentioned system, and both the image encoding device and the image decoding device in the above-mentioned embodiments can be incorporated into another system, for example, a car system.

[00286] The invention has been described together with various embodiments here. However, other variations of the disclosed embodiments can be understood and carried out by those skilled in the art in the practice of the claimed invention, from a study of the drawings, the disclosure and the appended claims. In the claims, the word "comprising" does not exclude other elements or steps and the indefinite article "a" or "an" does not exclude a plurality. A single processor or other unit can fulfill the functions of several items cited in the claims. The mere fact that certain measures are cited in generally different dependent claims does not indicate that a combination of these measures cannot be used to advantage. A computer program may be stored/distributed on a suitable medium, such as an optical storage medium or a solid-state medium provided along with or as part of other hardware, but may also be distributed in other ways, such as via the Internet or other wired or wireless communication systems.

[00287] One skilled in the art will understand that the "blocks" ("units") of the various figures (method and apparatus) represent or describe the functionalities of the embodiments of the invention (rather than necessarily individual "units" in hardware or software) and thus, they equally describe functions or features of apparatus modalities as well as method modalities (unit = step).

[00288] The terminology of "units" is used solely for illustrative purposes of the functionality of encoder/decoder embodiments and is not intended to limit the disclosure.

[00289] In the various embodiments provided in the present application, it should be understood that the disclosed system, apparatus and method can be implemented in other ways. For example, the apparatus embodiment described is merely exemplary. For example, unit division is merely a logical function division and may be another division in the actual implementation. For example, a plurality of units or components may be combined or integrated into another system, or some features may be ignored or not realized. Furthermore, the mutual couplings or direct couplings or communication connections shown or discussed can be implemented using some interfaces. Indirect couplings or communication connections between devices or units can be implemented in electronic, mechanical or other forms.

[00290] The units described as separate parts may or may not be physically separate, and the parts shown as units may or may not be physical units, may be located in one position, or may be distributed across a plurality of network units. Some or all units may be selected according to current needs to achieve the modalities solution objectives.

[00291] Furthermore, functional units in embodiments of the present invention may be integrated into a processing unit, or each of the units may physically exist alone, or two or more units are integrated into one unit.

[00292] Although embodiments of the invention have been described primarily based on video coding, it should be noted that embodiments of the encoding system 10, encoder 20 and decoder 30 (and correspondingly the system 10) and the other embodiments described herein also can be configured for image processing or coding, that is, the processing or coding of an individual image independent of any preceding or consecutive image as in video coding. In general, only the interprediction units 244 (encoder) and 344 (decoder) may not be available in the event that image processing coding is limited to a single image 17. All other features (also referred to as tools or technologies) of video encoder 20 and video decoder 30 may also be used for still image processing, e.g., residual calculation 204/304, transform 206, quantization 208, inverse quantization 210/310, (inverse) transform 212/312, partitioning 262/362, intraprediction 254/354 and/or loop filtering 220, 320 and entropy coding 270 and entropy decoding 304.

[00293] Embodiments of, for example, encoder 20 and decoder 30, and functions described herein, for example, with reference to encoder 20 and decoder 30, may be implemented in hardware, software, firmware, or any combination thereof. If implemented in software, functions may be stored in a computer-readable medium or transmitted via communication as one or more instructions or code, and executed by a hardware-based processing unit. Computer-readable medium may include computer-readable storage medium, which corresponds to a tangible medium, such as a data storage medium or communication medium, including any medium that facilitates the transfer of a computer program from one place to another, for example, according to a communication protocol. In this way, computer-readable medium generally can correspond to (1) tangible computer-readable storage medium that is non-transitory or (2) a communication medium, such as a signal or carrier wave. The data storage medium may be any available medium that can be accessed by one or more computers or one or more processors to retrieve instructions, code and/or data structures for implementing the techniques described in this disclosure. A computer program product may include a computer-readable medium.

[00294] By way of example, and not limitation, such computer-readable storage medium may comprise RAM, ROM, EEPROM, CD-ROM or other optical disk storage, magnetic disk storage or other magnetic storage devices, flash memory or any other medium that can be used to store desired program code in the form of instructions or data structures and that can be accessed by a computer. Furthermore, any connection is appropriately called a computer-readable medium. For example, if instructions are transmitted from a website, server, or other remote source using coaxial cable, fiber optic cable, twisted pair, digital subscriber line (DSL), or wireless technologies such as infrared, radio, and microwave , then coaxial cable, fiber optic cable, twisted pair, DSL, or wireless technologies such as infrared, radio, and microwave are included in the definition of medium. It must be understood, however, that the computer-readable storage medium and the data storage medium do not include connections, carrier waves, signals or other transient media, but are directed to tangible non-transitory storage media. Disk and disc as used herein include compact disc (CD), laser disc, optical disc, digital versatile disc (DVD), floppy disk, and Blu-ray disc, where disks generally reproduce data magnetically, while discs reproduce data optically with lasers. Combinations of the above must also be included in the scope of the machine-readable medium.

[00295] Instructions may be executed by one or more processors, such as one or more digital signal processors (DSPs), general-purpose microprocessors, application-specific integrated circuits (ASICs), field-programmable logic arrays (FPGAs), or others set of equivalent integrated or discrete logic circuits. Accordingly, the term "processor" as used herein may refer to any of the foregoing frameworks or any other framework suitable for implementing the techniques described herein. Additionally, in some aspects, the functionality described herein may be provided in dedicated hardware and/or software modules configured for encoding and decoding, or incorporated into a combined codec. Furthermore, the techniques can be fully implemented in one or more circuits or logic elements.

[00296] The techniques of this disclosure can be implemented in a wide variety of devices or apparatus, including a wireless handset, an integrated circuit (IC), or a set of ICs (e.g., a chip set). Various components, modules or units are described in this disclosure to emphasize functional aspects of devices configured to perform the disclosed techniques, but do not necessarily require performance by different hardware units. Instead, as described above, multiple units may be combined into a codec hardware unit or provided by a collection of interoperating hardware units, including one or more processors, as described above, in conjunction with suitable software and/or firmware. .

Claims (24)

1. Unblocking method, for unlocking a transform block boundary within a coding block in an image encoding and/or an image decoding, wherein the encoding block comprising transform blocks is encoded in the interprediction mode and the transform blocks comprise a first transform block and a second transform block that is adjacent to the first transform block, wherein the transform block boundary between the first and second transform blocks is aligned with a sample grid n x n, where n is an integer; characterized by the fact that the method comprises: - determining, when the boundary between the first transform block and the second transform block is a transform block boundary and at least one of the first transform block and the second transform block has one or more non-zero transform coefficients, a value of a boundary strength parameter, BS, for the boundary between the first transform block and the second transform block being a first value. 2. Method according to claim 1, characterized by the fact that the boundary between the first transform block and the second transform block is a sub-block transform boundary, SBT. 3. Method according to any one of the preceding claims, characterized in that the transform blocks further comprise a third transform block that is adjacent to the second transform block; and wherein the method further comprises: - determining, when the boundary between the second transform block and the third transform block is a sub-block transform boundary, SBT, and at least one of the second transform block and the third transform block has one or more non-zero transform coefficients, a value of a boundary strength parameter for the boundary between the second transform block and the third transform block being a first value; or - determine, when the boundary between the second transform block and the third transform block is a sub-block transform, the SBT boundary and both the second transform block and the third transform block have zero transform coefficients, a value of a boundary strength parameter for the boundary between the second transform block and the third transform block is a second value. 4. Method according to any of the preceding claims, characterized by the fact that the first value is 1. 5. Method according to claim 3, characterized by the fact that the second value is zero. 6. Method according to claim 1, characterized by the fact that n is 4 or 8. 7. Method according to claim 1, characterized by the fact that the n x n sample grid is 4 x 4 sample grid for the samples of the first and second transform blocks being luma samples; or 5. n x n sample grid is an 8 x 8 sample grid for the samples from the first and second transform blocks being chroma samples. 8. Method according to any one of claims 1 to 7, characterized by the fact that, if the coding block is divided in a horizontal direction, the transform block boundary between the first transform block and the second transform block transform is a horizontal transform block boundary; or if the coding block is divided in a vertical direction, the transform block boundary between the first transform block and the second transform block is a vertical transform block boundary. 9. Method according to any one of claims 1 to 8, characterized by the fact that the current coding block is encoded using a sub-block transform tool, SBT, or the transform block boundary is caused by a sub-block transform tool, SBT. 10. Device for use in an image encoder and/or an image decoder, for unlocking a transform block boundary within a coding block, wherein the coding block comprising transform blocks is coded in the interprediction mode and the transform blocks comprise a first transform block and a second transform block that is adjacent to the first transform block, wherein the transform block boundary between the first and second transform blocks is aligned with a sample grid n x n, where n is an integer; characterized by the fact that the device comprises an unblocking filter configured to: - determine, when a boundary between the first transform block and the second transform block is a transform unit boundary and at least one of the first transform block and the second transform block has one or more non-zero transform coefficients, a value of a boundary strength parameter for the boundary between the first transform block and the second transform block being a first value. 11. The device of claim 10, wherein the boundary between the first transform block and the second transform block is a sub-block transform boundary, SBT. 12. Device according to claim 10 or 11, characterized in that the transform blocks further comprise a third transform block that is adjacent to the second transform block, and the deblocking filter is further configured to determine, when the boundary between the second transform block and the third transform block is a sub-block transform boundary, SBT, and at least one of the second transform block and the third transform block has one or more different transform coefficients from zero, a value of a boundary strength parameter for the boundary between the second transform block and the third transform block is a first value; or - determine, when the boundary between the second transform block and the third transform block is a sub-block transform, the SBT boundary and both the second transform block and the third transform block have zero transform coefficients, a value of a boundary strength parameter for the boundary between the second transform block and the third transform block is a second value. 13. Device according to any one of claims 10 to 12, characterized by the fact that the first value is 1. 14. Device according to claim 12, characterized by the fact that the second value is zero. 15. Device according to claim 10, characterized by the fact that n is 4 or 8. 16. Device according to claim 10, characterized by the fact that the n x n sample grid is 4 x 4 sample grid for the samples of the first and second transform blocks being luma samples; or the n x n sample grid is an 8 x 8 sample grid for the samples from the first and second transform blocks being chroma samples. 17. Device according to any one of claims 10 to 16, characterized by the fact that, if the coding block is divided in a horizontal direction, the transform block boundary between the first transform block and the second transform block transform is a horizontal transform block boundary; or if the coding block is divided in a vertical direction, the transform block boundary between the first transform block and the second transform block is a vertical transform block boundary. 18. Device according to any one of claims 10 to 17, characterized by the fact that the current coding block is encoded using a sub-block transform tool, SBT, or the transform block boundary is performed by a sub-block transform tool, SBT. 19. Encoder (20), characterized by the fact that it comprises a set of processing circuits to carry out the method as defined in any one of claims 1 to 9. 20. Decoder (30), characterized by the fact that it comprises a set of processing circuits to carry out the method as defined in any one of claims 1 to 9. 21. Non-transitory computer readable medium, characterized in that it carries instructions that, when executed by a computer device, causes the computer device to perform the method as defined in any one of claims 1 to 9. 22. Decoder, characterized by the fact that it comprises: one or more processors; and a non-transitory computer-readable storage medium coupled to the processors and storing instructions for execution by the processors, wherein the instructions, when executed by the processors, configure the decoder to perform the method as defined in any one of claims 1 to 9. 23. Encoder, characterized by the fact that it comprises: one or more processors; and a non-transitory computer-readable storage medium coupled to the processors and storing instructions for execution by the processors, wherein the instructions, when executed by the processors, configure the encoder to perform the method as defined in any one of claims 1 to 9. 24. Non-transitory computer-readable medium, characterized by the fact that it stores a bit stream and one or more instructions executable by at least one processor, to perform encoding and decoding operations of the bit stream, the operations comprising: unlocking a boundary of transform block within a coding block, in an image encoder and/or an image decoder, wherein the coding block comprising transform blocks is encoded in interprediction mode and the transform blocks comprise a first block of transform and a second transform block that is adjacent to the first transform block, wherein the transform block boundary between the first and second transform blocks is aligned with an n x n sample grid, wherein n is an integer; when at least one of the first transform block and the second transform block has one or more non-zero transform coefficients, a value of a boundary strength (BS) parameter for the boundary between the first transform block and the second transform block be a first value.