CN116648907A

CN116648907A - Block partitioning structure for efficient prediction and transformation, and method and apparatus for video encoding and decoding using the same

Info

Publication number: CN116648907A
Application number: CN202180085387.3A
Authority: CN
Inventors: 边柱衡; 朴时奈; 沈东圭; 朴胜煜
Original assignee: Hyundai Motor Co; Industry Academic Collaboration Foundation of Kwangwoon University; Kia Corp
Current assignee: Hyundai Motor Co; Industry Academic Collaboration Foundation of Kwangwoon University; Kia Corp
Priority date: 2020-11-24
Filing date: 2021-11-24
Publication date: 2023-08-25

Abstract

A block partition structure for efficient prediction and transformation and a method and apparatus for video encoding and decoding using the block partition structure are disclosed. In particular, according to the present invention, there are provided methods and apparatuses for video encoding and decoding that are capable of dividing a block of video data into two areas or blocks including an L-shaped block and a rectangular block, and efficiently performing prediction on each block.

Description

Block partitioning structure for efficient prediction and transformation, and method and apparatus for video encoding and decoding using the same

Technical Field

The present invention relates to encoding and decoding of video data. More particularly, the present invention relates to a method for dividing a codec block of video data into two regions or blocks including an L-shaped block and a rectangular block and for efficiently predicting each region.

Background

The statements in this section merely provide background information related to the present disclosure and may not necessarily constitute prior art.

Since video data has a large data amount compared with audio data or still image data, the video data requires a large amount of hardware resources (including a memory) to store or transmit uncompressed video data.

Accordingly, encoders are typically used to compress and store or transmit video data. The decoder receives the compressed video data, decompresses the received compressed video data, and plays the decompressed video data. Video compression techniques include h.264/AVC, high efficiency video coding (High Efficiency Video Coding, HEVC), and Versatile Video Coding (VVC) that improves the coding efficiency of HEVC by about 30% or more.

However, as the image size, resolution, and frame rate of video data gradually increase, the amount of data to be encoded also increases. Accordingly, a new compression technique capable of providing higher coding efficiency and improved image enhancement effect as compared to the existing compression technique is required.

Disclosure of Invention

An aspect of the present invention is to provide a method and apparatus for video encoding and decoding that can divide a codec block of video data into two areas or blocks including an L-shaped block and a rectangular block and efficiently perform prediction for each area.

Another aspect of the invention provides a method for encoding a block of video data. The method comprises the following steps: the method includes determining that a block of video data is partitioned into an L-shaped block and a rectangular block, determining a partition type based on a relative position of the rectangular block within the block of video data, and determining a pair of prediction techniques to be applied to the L-shaped block and the rectangular block based on the partition type. The pair of prediction techniques includes a first prediction technique for an L-shaped block and a second prediction technique for a rectangular block. The method further comprises the steps of: a first predictor of samples within the L-shaped block is generated by applying a first prediction technique to the L-shaped block and a second predictor of samples within the rectangular block is generated by applying a second prediction technique to the rectangular block.

Another aspect of the present invention provides a method for decoding a block of video data. The method comprises the following steps: the method includes determining that a block of video data is partitioned into an L-shaped block and a rectangular block, determining a partition type based on a relative position of the rectangular block within the block of video data, and determining a pair of prediction techniques to be applied to the L-shaped block and the rectangular block based on the partition type. The pair of prediction techniques includes a first prediction technique for an L-shaped block and a second prediction technique for a rectangular block. The method further comprises the steps of: a first predictor of samples within the L-shaped block is generated by applying a first prediction technique to the L-shaped block and a second predictor of samples within the rectangular block is generated by applying a second prediction technique to the rectangular block.

One aspect of the present invention provides a video encoding device comprising a memory and at least one processor coupled to the memory to perform each step of the method for encoding blocks of video data. One aspect of the present invention provides a video decoding device comprising a memory and at least one processor connected to the memory to perform each step of the method for decoding blocks of video data.

An aspect of the present invention provides a computer-readable recording medium having instructions recorded therein, wherein the instructions, when executed by a processor of a video encoding apparatus, cause the video encoding apparatus to perform each step of a method of encoding a block of video data. An aspect of the present invention provides a computer-readable recording medium having instructions recorded therein, wherein the instructions, when executed by a processor of a video decoding apparatus, cause the video decoding apparatus to perform each step of a method of decoding a block of video data.

Drawings

Fig. 1 is a block diagram of a video encoding device capable of implementing the techniques of the present invention.

Fig. 2 shows block segmentation using a quadtree plus binary tree trigeminal tree (QTBTTT) structure.

Fig. 3a and 3b illustrate a plurality of intra prediction modes including a wide-angle intra prediction mode.

Fig. 4 shows neighboring blocks of the current block.

Fig. 5 is a block diagram of a video decoding apparatus capable of implementing the techniques of this disclosure.

Fig. 6 illustrates geometric block segmentation of shapes other than rectangles (including squares) supplied to a prediction unit according to an embodiment of the present invention.

Fig. 7a shows reference samples that can be used for intra prediction of rectangular blocks under split_right_down according to an embodiment of the present invention.

Fig. 7b shows reference samples that can be used for intra prediction of L-shaped blocks under SPLIT LEFT UP according to an embodiment of the present invention.

Fig. 8a is a conceptual diagram illustrating bilinear interpolation performed on an L-shaped block of a codec block under split_right_down according to an embodiment of the present invention.

Fig. 8b is a conceptual diagram illustrating bilinear interpolation performed on a rectangular block of a codec block under split_left_up according to an embodiment of the present invention.

Fig. 9a to 9d show transform units that may be considered for a codec block using geometric block segmentation according to an embodiment of the present invention.

Fig. 10 is a flowchart illustrating a method of encoding and decoding a block of video data according to an embodiment of the present invention.

Detailed Description

Hereinafter, some embodiments of the present invention are described in detail with reference to the accompanying illustrative drawings. In the following description, like reference numerals denote like elements, although the elements are shown in different drawings. Furthermore, in the following description of some embodiments, a detailed description of related known components and functions has been omitted for clarity and conciseness when it may be considered that the subject matter of the present invention is obscured.

Fig. 1 is a block diagram of a video encoding device in which the techniques of the present invention may be implemented. Hereinafter, a video encoding apparatus and sub-components of the apparatus are described with reference to the illustration of fig. 1.

The encoding apparatus may include: an image divider 110, a predictor 120, a subtractor 130, a transformer 140, a quantizer 145, a reordering unit 150, an entropy encoder 155, an inverse quantizer 160, an inverse transformer 165, an adder 170, a loop filtering unit 180, and a memory 190.

Each component of the encoding apparatus may be implemented as hardware or software, or as a combination of hardware and software. In addition, the function of each component may be implemented as software, and the microprocessor may also be implemented to execute the function of the software corresponding to each component.

A video is made up of one or more sequences comprising a plurality of images. Each image is divided into a plurality of regions, and encoding is performed on each region. For example, an image is segmented into one or more tiles (tiles) or/and slices (slices). Here, one or more tiles may be defined as a tile set. Each tile or/and slice is partitioned into one or more Coding Tree Units (CTUs). In addition, each CTU is partitioned into one or more Coding Units (CUs) by a tree structure. Information applied to each CU is encoded as a syntax of the CU, and information commonly applied to CUs included in one CTU is encoded as a syntax of the CTU. In addition, information commonly applied to all blocks in one slice is encoded as syntax of a slice header, and information applied to all blocks constituting one or more pictures is encoded as a picture parameter set (Picture Parameter Set, PPS) or a picture header. Furthermore, information commonly referred to by the plurality of images is encoded as a sequence parameter set (Sequence Parameter Set, SPS). In addition, information commonly referenced by the one or more SPS is encoded as a set of video parameters (Video Parameter Set, VPS). Furthermore, information commonly applied to one tile or group of tiles may also be encoded as syntax of the tile or group of tiles header. The syntax included in the SPS, PPS, slice header, tile, or tile set header may be referred to as a high level syntax.

The image divider 110 determines the size of the CTU. Information about the size of the CTU (CTU size) is encoded as a syntax of the SPS or PPS and transmitted to the video decoding apparatus.

The image divider 110 divides each image constituting a video into a plurality of CTUs having a predetermined size, and then recursively divides the CTUs by using a tree structure. Leaf nodes in the tree structure become CUs, which are the basic units of coding.

The tree structure may be a Quadtree (QT) in which a higher node (or parent node) is partitioned into four lower nodes (or child nodes) of the same size. The tree structure may be a Binary Tree (BT) in which a higher node is split into two lower nodes. The tree structure may be a Trigeminal Tree (TT), where the higher nodes are split into three lower nodes at a ratio of 1:2:1. The tree structure may be a structure in which two or more of a QT structure, a BT structure, and a TT structure are mixed. For example, a quadtree plus binary tree (quadtree plus binarytree, QTBT) structure may be utilized, or a quadtree plus binary tree trigeminal tree (quadtree plus binarytree ternarytree, QTBTTT) structure may be utilized. Here, BTTT is added to the tree structure to be called multiple-type tree (MTT).

Fig. 2 is a schematic diagram for describing a method of dividing a block by using the QTBTTT structure.

As shown in fig. 2, the CTU may be first partitioned into QT structures. Quadtree partitioning may be recursive until the size of the partitioned block reaches the minimum block size (MinQTSize) of leaf nodes allowed in QT. A first flag (qt_split_flag) indicating whether each node of the QT structure is partitioned into four lower-layer nodes is encoded by the entropy encoder 155 and signaled to the video decoding apparatus. When the leaf node of QT is not greater than the maximum block size (MaxBTSize) of the root node allowed in BT, the leaf node may be further divided into at least one of BT structure or TT structure. There may be multiple directions of segmentation in the BT structure and/or the TT structure. For example, there may be two directions, i.e., a direction of dividing the block of the corresponding node horizontally and a direction of dividing the block of the corresponding node vertically. As shown in fig. 2, when the MTT division starts, a second flag (MTT _split_flag) indicating whether a node is divided, and a flag additionally indicating a division direction (vertical or horizontal) and/or a flag indicating a division type (binary or trigeminal) in the case that a node is divided are encoded by the entropy encoder 155 and signaled to the video decoding apparatus.

Alternatively, a CU partition flag (split_cu_flag) indicating whether a node is partitioned may be further encoded before encoding a first flag (qt_split_flag) indicating whether each node is partitioned into four nodes of a lower layer. When the value of the CU partition flag (split_cu_flag) indicates that each node is not partitioned, the block of the corresponding node becomes a leaf node in the partition tree structure and becomes a CU, which is a basic unit of encoding. When the value of the CU partition flag (split_cu_flag) indicates that each node is partitioned, the video encoding apparatus first starts encoding the first flag in the above scheme.

When QTBT is used as another example of the tree structure, there may be two types, i.e., a type of horizontally dividing a block of a corresponding node into two blocks having the same size (i.e., symmetrical horizontal division) and a type of vertically dividing a block of a corresponding node into two blocks having the same size (i.e., symmetrical vertical division). A partition flag (split_flag) indicating whether each node of the BT structure is partitioned into lower-layer blocks and partition type information indicating a partition type are encoded by the entropy encoder 155 and transmitted to the video decoding apparatus. On the other hand, there may additionally be a type in which a block of a corresponding node is divided into two blocks in an asymmetric form to each other. The asymmetric form may include a form in which a block of a corresponding node is divided into two rectangular blocks having a size ratio of 1:3, or may further include a form in which a block of a corresponding node is divided in a diagonal direction.

A CU may have various sizes according to QTBT or QTBTTT divided from CTUs. Hereinafter, a block corresponding to a CU to be encoded or decoded (i.e., a leaf node of QTBTTT) is referred to as a "current block". When QTBTTT segmentation is employed, the shape of the current block may also be rectangular in shape, in addition to square shape.

The predictor 120 predicts the current block to generate a predicted block. Predictor 120 includes an intra predictor 122 and an inter predictor 124.

In general, each of the current blocks in the image may be predictively encoded. In general, prediction of a current block may be performed by using an intra prediction technique using data from an image including the current block or an inter prediction technique using data from an image encoded before the image including the current block. Inter prediction includes both unidirectional prediction and bi-directional prediction.

The intra predictor 122 predicts pixels in the current block by using pixels (reference pixels) located adjacent to the current block in the current image including the current block. Depending on the prediction direction, there are multiple intra prediction modes. For example, as shown in fig. 3a, the plurality of intra prediction modes may include two non-directional modes including a planar (planar) mode and a DC mode, and may include 65 directional modes. The neighboring pixels and algorithm equations to be used are defined differently according to each prediction mode.

For efficient direction prediction of a current block having a rectangular shape, direction modes (# 67 to # 80) indicated by dotted arrows in fig. 3b, intra prediction modes # -1 to # -14) may be additionally utilized. The direction mode may be referred to as a "wide angle intra-prediction mode". In fig. 3b, the arrows indicate the respective reference samples for prediction, rather than representing the prediction direction. The prediction direction is opposite to the direction indicated by the arrow. When the current block has a rectangular shape, the wide-angle intra prediction mode is a mode in which prediction is performed in a direction opposite to a specific direction mode without additional bit transmission. In this case, in the wide-angle intra prediction mode, some of the wide-angle intra prediction modes available for the current block may be determined by a ratio of a width to a height of the current block having a rectangular shape. For example, when the current block has a rectangular shape having a height smaller than a width, wide-angle intra prediction modes (intra prediction modes #67 to # 80) having angles smaller than 45 degrees are available. When the current block has a rectangular shape with a width greater than a height, a wide-angle intra prediction mode having an angle greater than-135 degrees is available.

The intra predictor 122 may determine intra prediction to be used for encoding the current block. In some examples, intra predictor 122 may encode the current block by utilizing a plurality of intra prediction modes, and may also select an appropriate intra prediction mode to use from among the test modes. For example, the intra predictor 122 may calculate a rate distortion value by using rate-distortion (rate-distortion) analysis of a plurality of tested intra prediction modes, and may also select an intra prediction mode having the best rate distortion characteristics among the test modes.

The intra predictor 122 selects one intra prediction mode among a plurality of intra prediction modes, and predicts the current block by using neighboring pixels (reference pixels) determined according to the selected intra prediction mode and an algorithm equation. Information about the selected intra prediction mode is encoded by the entropy encoder 155 and transmitted to a video decoding device.

The inter predictor 124 generates a prediction block of the current block by using a motion compensation process. The inter predictor 124 searches for a block most similar to the current block in a reference picture encoded and decoded earlier than the current picture, and generates a predicted block of the current block by using the searched block. In addition, a Motion Vector (MV) is generated, which corresponds to a displacement (displacement) between a current block in the current image and a predicted block in the reference image. In general, motion estimation is performed on a luminance (luma) component, and a motion vector calculated based on the luminance component is used for both the luminance component and the chrominance component. Motion information including information of the reference picture and information on a motion vector for predicting the current block is encoded by the entropy encoder 155 and transmitted to a video decoding device.

The inter predictor 124 may also perform interpolation of reference pictures or reference blocks to increase the accuracy of prediction. In other words, the sub-samples are interpolated between two consecutive integer samples by applying the filter coefficients to a plurality of consecutive integer samples comprising the two integer samples. When the search processing of the block most similar to the current block is performed on the interpolated reference image, the decimal-unit precision may be represented for the motion vector instead of the integer-sample-unit precision. The precision or resolution of the motion vector may be set differently for each target region to be encoded, e.g., a unit such as a slice, tile, CTU, CU, etc. When such adaptive motion vector resolution (adaptive motion vector resolution, AMVR) is applied, information on the motion vector resolution to be applied to each target area should be signaled for each target area. For example, when the target area is a CU, information on the motion vector resolution applied for each CU is signaled. The information on the resolution of the motion vector may be information representing the accuracy of a motion vector difference to be described below.

On the other hand, the inter predictor 124 may perform inter prediction by using bi-directional prediction. In the case of bi-prediction, two reference pictures and two motion vectors representing block positions most similar to the current block in each reference picture are utilized. The inter predictor 124 selects a first reference picture and a second reference picture from the reference picture list0 (RefPicList 0) and the reference picture list1 (RefPicList 1), respectively. The inter predictor 124 also searches for a block most similar to the current block in the corresponding reference picture to generate a first reference block and a second reference block. Further, a prediction block of the current block is generated by averaging or weighted-averaging the first reference block and the second reference block. Further, motion information including information on two reference pictures for predicting the current block and information on two motion vectors is transmitted to the entropy encoder 155. Here, the reference image list0 may be constituted by an image preceding the current image in display order among the pre-restored images, and the reference image list1 may be constituted by an image following the current image in display order among the pre-restored images. However, although not particularly limited thereto, a pre-restored image subsequent to the current image in display order may be additionally included in the reference image list 0. Conversely, a pre-restored image preceding the current image may be additionally included in the reference image list 1.

In order to minimize the amount of bits consumed for encoding motion information, various methods may be utilized.

For example, when a reference image and a motion vector of a current block are identical to those of a neighboring block, information capable of identifying the neighboring block is encoded to transmit the motion information of the current block to a video decoding apparatus. This method is called merge mode (merge mode).

In the merge mode, the inter predictor 124 selects a predetermined number of merge candidate blocks (hereinafter, referred to as "merge candidates") from neighboring blocks of the current block.

As the neighboring blocks used to derive the merge candidates, all or some of the left block A0, the lower left block A1, the upper block B0, the upper right block B1, and the upper left block B2 adjacent to the current block in the current image may be utilized, as shown in fig. 4. In addition, in addition to the current picture in which the current block is located, a block located within a reference picture (which may be the same as or different from the reference picture used to predict the current block) may also be used as a merging candidate. For example, a co-located block (co-located block) of a current block within a reference picture or a block adjacent to the co-located block may additionally be used as a merging candidate. If the number of merging candidates selected by the above method is less than a preset number, a zero vector is added to the merging candidates.

The inter predictor 124 configures a merge list including a predetermined number of merge candidates by using neighboring blocks. A merge candidate to be used as motion information of the current block is selected from among the merge candidates included in the merge list, and merge index information for identifying the selected candidate is generated. The generated merging index information is encoded by the entropy encoder 155 and transmitted to a video decoding apparatus.

The merge skip mode is a special case of the merge mode. After quantization, when all transform coefficients used for entropy coding are near zero, only neighboring block selection information is transmitted without transmitting a residual signal. By using the merge skip mode, relatively high encoding efficiency can be achieved for images with slight motion, still images, screen content images, and the like.

Hereinafter, the merge mode and the merge skip mode are collectively referred to as a merge/skip mode.

Another method for encoding motion information is advanced motion vector prediction (advanced motion vector prediction, AMVP) mode.

In the AMVP mode, the inter predictor 124 derives a motion vector prediction candidate for a motion vector of a current block by using neighboring blocks of the current block. As the neighboring blocks used to derive the motion vector prediction candidates, all or some of the left block A0, the lower left block A1, the upper side block B0, the upper right block B1, and the upper left block B2 adjacent to the current block in the current image shown in fig. 4 may be utilized. In addition, in addition to the current picture in which the current block is located, a block located within a reference picture (which may be the same as or different from a reference picture used to predict the current block) may also be used as a neighboring block used to derive a motion vector prediction candidate. For example, a co-located block of the current block within the reference picture or a block adjacent to the co-located block may be utilized. If the number of motion vector candidates selected by the above method is less than a preset number, a zero vector is added to the motion vector candidates.

The inter predictor 124 derives a motion vector prediction candidate by using the motion vector of the neighboring block, and determines a motion vector prediction of the motion vector of the current block by using the motion vector prediction candidate. In addition, a motion vector difference is calculated by subtracting a motion vector prediction from a motion vector of the current block.

Motion vector prediction may be obtained by applying a predefined function (e.g., median and average calculations, etc.) to the motion vector prediction candidates. In this case, the video decoding device is also aware of the predefined function. Further, since the neighboring block used to derive the motion vector prediction candidates is a block for which encoding and decoding have been completed, the video decoding apparatus may also already know the motion vector of the neighboring block. Therefore, the video encoding device does not need to encode information for identifying motion vector prediction candidates. Accordingly, in this case, information on a motion vector difference and information on a reference image for predicting a current block are encoded.

On the other hand, motion vector prediction may also be determined by selecting a scheme of any one of the motion vector prediction candidates. In this case, the information for identifying the selected motion vector prediction candidates is additionally encoded together with the information about the motion vector difference and the information about the reference picture for predicting the current block.

The predictor 120 may further utilize Intra Block Copy (IBC) prediction. In IBC prediction, the predictor 120 searches for a predicted block in the same frame or image as the block encoded in intra prediction, but the predictor 120 may generally search for a wider search area and adjacent rows and columns of pixels. In IBC prediction, the predictor 120 may determine a block vector (also referred to as a motion vector) to identify a predicted block within the same frame or image as the block being predicted. The block vector contains an x component that identifies a horizontal displacement between the video block being predicted and the prediction block and a y component that identifies a vertical displacement between the video block being predicted and the prediction block. The determined block vector is signaled in the bitstream so that the video decoding apparatus can identify the prediction block selected by the video encoding apparatus.

The subtractor 130 generates a residual block by subtracting the current block from the prediction block generated by the intra predictor 122 or the inter predictor 124.

The transformer 140 transforms a residual signal in a residual block having pixel values of a spatial domain into transform coefficients of a frequency domain. The transformer 140 may transform a residual signal in a residual block by using the entire size of the residual block as a transform unit, or may divide the residual block into a plurality of sub-blocks and perform the transform by using the sub-blocks as transform units. Alternatively, the residual block is divided into two sub-blocks (i.e., a transform region and a non-transform region) to transform the residual signal by using only the transform region sub-block as a transform unit. Here, the transform region sub-block may be one of two rectangular blocks having a size ratio of 1:1 based on a horizontal axis (or a vertical axis). In this case, a flag (cu_sbt_flag) indicating that only the sub-block is transformed, and direction (vertical/horizontal) information (cu_sbt_horizontal_flag) and/or position information (cu_sbt_pos_flag) are encoded by the entropy encoder 155 and signaled to the video decoding apparatus. In addition, the size of the transform region sub-block may have a size ratio of 1:3 based on the horizontal axis (or vertical axis). In this case, a flag (cu_sbt_quad_flag) dividing the corresponding division is additionally encoded by the entropy encoder 155 and signaled to the video decoding device.

On the other hand, the transformer 140 may perform transformation of the residual block separately in the horizontal direction and the vertical direction. For this transformation, various types of transformation functions or transformation matrices may be utilized. For example, the pair-wise transformation function for horizontal and vertical transformations may be defined as a transformation set (multiple transform set, MTS). The transformer 140 may select one transform function pair having the highest transform efficiency in the MTS and transform the residual block in each of the horizontal and vertical directions. Information (mts_idx) about the transform function pairs in the MTS is encoded by the entropy encoder 155 and signaled to the video decoding means.

The quantizer 145 quantizes the transform coefficient output from the transformer 140 using a quantization parameter, and outputs the quantized transform coefficient to the entropy encoder 155. The quantizer 145 may also immediately quantize the relevant residual block without transforming any block or frame. The quantizer 145 may also apply different quantization coefficients (scaling values) according to the positions of the transform coefficients in the transform block. A quantization matrix applied to quantized transform coefficients arranged in two dimensions may be encoded and signaled to a video decoding apparatus.

The reordering unit 150 may perform the rearrangement of the coefficient values on the quantized residual values.

The rearrangement unit 150 may change the 2D coefficient array to a 1D coefficient sequence by using coefficient scanning. For example, the rearrangement unit 150 may scan the DC coefficient to the high frequency region coefficient using zigzag scanning (zig-zag scan) or diagonal scanning (diagonal scan) to output a 1D coefficient sequence. Instead of the zig-zag scan, a vertical scan that scans the 2D coefficient array in the column direction and a horizontal scan that scans the 2D block type coefficients in the row direction may also be utilized, depending on the size of the transform unit and the intra prediction mode. In other words, the scanning method to be used may be determined in zigzag scanning, diagonal scanning, vertical scanning, and horizontal scanning according to the size of the transform unit and the intra prediction mode.

The entropy encoder 155 encodes the sequence of the 1D quantized transform coefficients output from the rearrangement unit 150 by using various encoding schemes including Context-based adaptive binary arithmetic coding (Context-based Adaptive Binary Arithmetic Code, CABAC), exponential golomb (Exponential Golomb), and the like to generate a bitstream.

Further, the entropy encoder 155 encodes information related to block division (e.g., CTU size, CTU division flag, QT division flag, MTT division type, MTT division direction, etc.) so that the video decoding apparatus can divide blocks equally to the video encoding apparatus. Further, the entropy encoder 155 encodes information on a prediction type indicating whether the current block is encoded by intra prediction or inter prediction. The entropy encoder 155 encodes intra prediction information (i.e., information about an intra prediction mode) or inter prediction information (a merge index in the case of a merge mode, and information about a reference picture index and a motion vector difference in the case of an AMVP mode) according to a prediction type. Further, the entropy encoder 155 encodes information related to quantization (i.e., information about quantization parameters and information about quantization matrices).

The inverse quantizer 160 dequantizes the quantized transform coefficients output from the quantizer 145 to generate transform coefficients. The inverse transformer 165 transforms the transform coefficients output from the inverse quantizer 160 from the frequency domain to the spatial domain to restore a residual block.

The adder 170 adds the restored residual block and the prediction block generated by the predictor 120 to restore the current block. The pixels in the restored current block are used as reference pixels when intra-predicting the next block.

The loop filtering unit 180 performs filtering on the restored pixels to reduce block artifacts (blocking artifacts), ringing artifacts (ringing artifacts), blurring artifacts (blurring artifacts), etc., which occur due to block-based prediction and transform/quantization. The loop filtering unit 180 as an in-loop filter may include all or some of a deblocking filter 182, a sample adaptive offset (sample adaptive offset, SAO) filter 184, and an adaptive loop filter (adaptive loop filter, ALF) 186.

Deblocking filter 182 filters boundaries between restored blocks to remove block artifacts (blocking artifacts) that occur due to block unit encoding/decoding, and SAO filter 184 and ALF 186 additionally filter the deblock filtered video. The SAO filter 184 and ALF 186 are filters for compensating for differences between restored pixels and original pixels that occur due to lossy coding (loss coding). The SAO filter 184 applies an offset as a CTU unit to enhance subjective image quality and coding efficiency. In contrast, the ALF 186 performs block unit filtering, and applies different filters to compensate for distortion by dividing boundaries of respective blocks and the degree of variation. Information about filter coefficients to be used for ALF may be encoded and signaled to the video decoding apparatus.

The restored blocks filtered by the deblocking filter 182, the SAO filter 184, and the ALF 186 are stored in the memory 190. When all blocks in one image are restored, the restored image may be used as a reference image for inter-predicting blocks within a picture to be subsequently encoded.

Fig. 5 is a functional block diagram of a video decoding apparatus in which the techniques of the present invention may be implemented. Hereinafter, with reference to fig. 5, a video decoding apparatus and sub-components of the apparatus are described.

The video decoding apparatus may be configured to include an entropy decoder 510, a reordering unit 515, an inverse quantizer 520, an inverse transformer 530, a predictor 540, an adder 550, a loop filtering unit 560, and a memory 570.

Similar to the video encoding apparatus of fig. 1, each component of the video decoding apparatus may be implemented as hardware or software, or as a combination of hardware and software. In addition, the function of each component may be implemented as software, and the microprocessor may also be implemented to execute the function of the software corresponding to each component.

The entropy decoder 510 extracts information related to block segmentation by decoding a bitstream generated by a video encoding apparatus to determine a current block to be decoded, and extracts prediction information required to restore the current block and information on a residual signal.

The entropy decoder 510 determines the size of CTUs by extracting information about the CTU size from a Sequence Parameter Set (SPS) or a Picture Parameter Set (PPS), and partitions a picture into CTUs having the determined size. Further, the CTU is determined as the highest layer (i.e., root node) of the tree structure, and the partition information of the CTU is extracted to partition the CTU by using the tree structure.

For example, when dividing a CTU by using the QTBTTT structure, first a first flag (qt_split_flag) related to the division of QT is extracted to divide each node into four nodes of the lower layer. In addition, a second flag (mtt_split_flag), a split direction (vertical/horizontal), and/or a split type (binary/trigeminal) related to the split of the MTT are extracted with respect to a node corresponding to the leaf node of the QT to split the corresponding leaf node into an MTT structure. As a result, each node below the leaf node of QT is recursively partitioned into BT or TT structures.

As another example, when a CTU is divided by using the QTBTTT structure, a CU division flag (split_cu_flag) indicating whether to divide the CU is extracted. When the corresponding block is partitioned, a first flag (qt_split_flag) may also be extracted. During the segmentation process, recursive MTT segmentation of 0 or more times may occur after recursive QT segmentation of 0 or more times for each node. For example, for CTUs, MTT partitioning may occur immediately, or conversely, QT partitioning may occur only multiple times.

As another example, when dividing the CTU by using the QTBT structure, a first flag (qt_split_flag) related to the division of QT is extracted to divide each node into four nodes of the lower layer. In addition, a split flag (split_flag) indicating whether or not a node corresponding to a leaf node of QT is further split into BT and split direction information are extracted.

On the other hand, when the entropy decoder 510 determines the current block to be decoded by using the partition of the tree structure, the entropy decoder 510 extracts information on a prediction type indicating whether the current block is intra-predicted or inter-predicted. When the prediction type information indicates intra prediction, the entropy decoder 510 extracts syntax elements for intra prediction information (intra prediction mode) of the current block. When the prediction type information indicates inter prediction, the entropy decoder 510 extracts information representing syntax elements of the inter prediction information, i.e., a motion vector and a reference picture to which the motion vector refers.

Further, the entropy decoder 510 extracts quantization-related information and information on transform coefficients of the quantized current block as information on a residual signal.

The reordering unit 515 may change the sequence of the 1D quantized transform coefficients entropy decoded by the entropy decoder 510 into a 2D coefficient array (i.e., block) again in the reverse order of the coefficient scan order performed by the video encoding device.

The inverse quantizer 520 dequantizes the quantized transform coefficients, and dequantizes the quantized transform coefficients by using quantization parameters. The inverse quantizer 520 may also apply different quantization coefficients (scaling values) to the quantized transform coefficients arranged in 2D. The inverse quantizer 520 may perform inverse quantization by applying a matrix of quantized coefficients (scaled values) from the video encoding device to a 2D array of quantized transform coefficients.

The inverse transformer 530 restores a residual signal by inversely transforming the inversely quantized transform coefficients from the frequency domain to the spatial domain to generate a residual block of the current block.

Further, when the inverse transformer 530 inversely transforms a partial region (sub-block) of the transform block, the inverse transformer 530 extracts a flag (cu_sbt_flag) transforming only the sub-block of the transform block, direction (vertical/horizontal) information (cu_sbt_horizontal_flag) of the sub-block, and/or position information (cu_sbt_pos_flag) of the sub-block. The inverse transformer 530 also inversely transforms transform coefficients of the corresponding sub-block from the frequency domain to the spatial domain to restore a residual signal, and fills the region that is not inversely transformed with a value of "0" as the residual signal to generate a final residual block of the current block.

Further, when applying MTS, the inverse transformer 530 determines a transform index or a transform matrix to be applied in each of the horizontal direction and the vertical direction by using MTS information (mts_idx) signaled from the video encoding apparatus. The inverse transformer 530 also performs inverse transformation on the transform coefficients in the transform block in the horizontal direction and the vertical direction by using the determined transform function.

The predictor 540 may include an intra predictor 542 and an inter predictor 544. The intra predictor 542 is activated when the prediction type of the current block is intra prediction, and the inter predictor 544 is activated when the prediction type of the current block is inter prediction.

The intra predictor 542 determines an intra prediction mode of the current block among the plurality of intra prediction modes according to syntax elements of the intra prediction mode extracted from the entropy decoder 510. The intra predictor 542 also predicts the current block by using neighboring reference pixels of the current block according to an intra prediction mode.

The inter predictor 544 determines a motion vector of the current block and a reference picture to which the motion vector refers by using syntax elements of the inter prediction mode extracted from the entropy decoder 510.

The predictor 540 may further utilize an Intra Block Copy (IBC) mode. In IBC mode, the predictor 540 may identify a prediction block selected by the video encoding device using a block vector decoded from the bitstream by the entropy decoder 410.

The adder 550 restores the current block by adding the residual block output from the inverse transformer to the predicted block output from the inter predictor or the intra predictor. In intra prediction of a block to be decoded later, pixels within the restored current block are used as reference pixels.

The loop filtering unit 560, which is an in-loop filter, may include a deblocking filter 562, an SAO filter 564, and an ALF 566. Deblocking filter 562 performs deblocking filtering on boundaries between restored blocks to remove block artifacts occurring due to block unit decoding. The SAO filter 564 and ALF 566 perform additional filtering on the restored block after deblocking filtering to compensate for differences between restored pixels and original pixels that occur due to lossy encoding. The filter coefficients of the ALF are determined by using information on the filter coefficients decoded from the bitstream.

The restored blocks filtered by the deblocking filter 562, the SAO filter 564, and the ALF 566 are stored in the memory 570. When all blocks in one image are restored, the restored image may be used as a reference image for inter-predicting blocks within a picture to be subsequently encoded.

The present invention relates to encoding and decoding of video data. More particularly, the present invention relates to a codec block for efficiently predicting video data by dividing the codec block into two areas or (sub) blocks including an L-shaped block and a rectangular block and performing prediction on each (sub) block. The prediction technique suitable for each (sub) block may be selected by the video encoder or may be predefined for increasing the prediction accuracy depending on the relative position of each (sub) block within the codec block.

The block 600 of video data may be divided into rectangular blocks 610 adjacent to corners of the block 600 and L-shaped blocks 620 defined by the rectangular blocks 610. For example, block 600 of video data may correspond to a CTU or CU, and rectangular block 610 and L-shaped block 620 may correspond to a PU.

As shown in fig. 6 (a) to (b), a rectangular block 610 may abut one of a lower right corner, an upper left corner, an upper right corner, and a lower left corner within a block 600 of video data. In the following description, these partition types may be referred to as split_right_down, split_left_up, split_right_up, and split_left_down, respectively. In an embodiment, the split_right_down and split_left_up of the four partition types illustrated may be used for blocks of video data. In another embodiment, only split_right_down may be used for blocks of video data in the four illustrated SPLIT types. In yet another embodiment, all four partition types illustrated may be used for blocks of video data.

The size (i.e., width M and height N) of the rectangular block 610 in the block 600 of video data may be determined by the size (i.e., a specific ratio between width W and height H) of the block 600 of video data. Here, the specific ratio may be 1/4, 1/2, or 3/4, or may be selected from them. Alternatively, the size of the rectangular block 610 may be a predefined fixed size.

The video encoder may determine whether to apply such geometric block partitioning to a given block 600 of video data. The video encoder may signal a 1-bit flag (e.g., new_split_flag) indicating whether such geometric block partitioning applies to a given block 600 and an index indicating one of a plurality of partition types to the video decoder. The video encoder may determine that geometric block partitioning is not applied to the block 600 of video data, in which case the block 600 of video data may be predicted as a single prediction unit without being partitioned.

Whether geometric block partitioning is applied to a given block 600 may depend on the size of the given block 600. In an embodiment, a minimum size and/or a maximum size of the block 600 may be defined that allows for geometric block segmentation. For example, if the width W and height H of the block 600 satisfy "Wmin < W < Wmax, hmin < H < Hmax", geometric block segmentation may be applied to the block 600. Accordingly, signaling a 1-bit flag (e.g., new_split_flag) may be omitted if the size of a given block 600 is less than the minimum size or greater than the maximum size.

In an embodiment, the geometric block partition shown in fig. 6 may be integrated into the block partition of the CTU shown in fig. 2. For example, the geometric partitioning shown in fig. 6, quadtree (QT) partitioning, binary Tree (BT) partitioning, and Trigeminal Tree (TT) partitioning may be used for block partitioning of CTUs. In the case where geometric division is applied to a block corresponding to a given node and the block is divided into an L-shaped block and a rectangular block corresponding to two child nodes, quadtree (QT) division, binary Tree (BT) division, and Trigeminal Tree (TT) division may be applied to the rectangular block, but division may no longer be applied to the L-shaped block. That is, the child nodes corresponding to the L-shaped blocks may be leaf nodes in a tree structure.

In the case where the codec block 600 of video data is divided into two sub-blocks 610 and 620 including a rectangular block 610 and an L-shaped block 620, a prediction technique suitable for each of the sub-blocks 610 and 620 may be selected by a video encoder, or the prediction technique may be predefined according to the relative position of each of the sub-blocks 610 and 620 within the codec block 600 to improve the prediction technique.

For example, a video encoder may select one of the available prediction techniques (e.g., intra-prediction, inter-prediction, and intra-block copy (IBC)) for each sub-block 610 and 620 of a given codec block 600. Intra prediction techniques may be applied to both sub-blocks 610 and 620, or different prediction techniques may be applied to both sub-blocks 610 and 620. For example, a pair of prediction techniques selected by a video encoder may be applied to sub-blocks 610 and 620 of a given codec block 600. The video encoder may signal syntax elements indicating two prediction techniques to be applied to the rectangular block 610 and the L-shaped block 620 to the video decoder.

In an embodiment, a pair of prediction techniques to be applied to each partition type of the geometric block partition shown in fig. 6 may be predefined. Accordingly, when geometric block partitioning is applied to a given codec block 600, syntax elements indicating two prediction techniques to be applied to the rectangular block 610 and the L-shaped block 620 may not need to be signaled.

For example, in the case of SPLIT RIGHT DOWN, the video encoder and video decoder may determine (or infer) to apply intra prediction to L-shaped block 620 and inter prediction to rectangular block 610. In the case of SPLIT LEFT UP, the video encoder and video decoder may determine (or infer) to apply inter prediction to L-shaped block 620 and intra prediction to rectangular block 610. In the case of split_right_up and split_left_down, the video encoder and video decoder may determine (or infer) to apply intra prediction to L-shaped block 620 and inter prediction to rectangular block 610.

In the case of applying geometric block partitioning to a codec block 600 within an I slice of video data, different prediction techniques, intra prediction, and intra block copying may be applied to the two sub-blocks 610 and 620. For example, in the case of SPLIT RIGHT DOWN, the video encoder and video decoder may determine (or infer) that intra prediction is to be applied to L-shaped block 620 and that intra block copy is to be applied to rectangular block 610. Also, in the case of split_left_up, the video encoder and video decoder may determine (or infer) to apply intra prediction to rectangular block 610 and intra block copy to L-shaped block 620.

In the case where different prediction techniques are applied to the two sub-blocks 610 and 620 of the codec block 600, when intra prediction is applied to any one of the reconstructed samples (serving as reference pixels for intra prediction) located near the left block and the upper block adjacent to the codec block 600 of the two sub-blocks 610 and 620, the prediction can be performed more efficiently. In addition, when inter prediction (or intra block copy) is applied to any one of the two sub-blocks 610 and 620, instead of intra prediction, reconstructed samples (serving as reference pixels for intra prediction) located far from the left block and the upper block adjacent to the codec block 600 may be more efficiently performed. In this way, by geometrically dividing a given codec block into a region suitable for intra prediction and a region unsuitable for intra prediction, and applying inter prediction (or intra block copy) to the region unsuitable for intra prediction, prediction accuracy of the codec block 600 can be improved, and residual signal amount can be reduced, thereby improving overall coding efficiency.

Within the codec block 600 of video data, the rectangular block 610 and the L-shaped block 620 may be sequentially encoded and decoded in a predefined order. That is, the video decoder may decode the rectangular block 610 or the L-shaped block 620 and then start encoding the other block.

In an embodiment, in the case where the codec block 600 of video data is divided into two blocks including a rectangular block 610 and an L-shaped block 620, intra prediction may be applied to the rectangular block 610 and the L-shaped block 620, respectively. In addition, other blocks (e.g., blocks including [0,0] samples of the codec block 600) may have been reconstructed before intra prediction is performed on the rectangular block 610 or the L-shaped block 620.

For example, in the case of SPLIT RIGHT DOWN, the L-shaped block 620 in the upper left corner may have been reconstructed prior to predicting the rectangular block 610 within the codec block 600. That is, when intra prediction is performed on the rectangular block 610 within the codec block 600, reconstructed samples of the L-shaped block 620 within the codec block 600 may be utilized. Accordingly, the L-shaped block 620 may be intra-predicted from reference samples adjacent to the codec block 600, and the rectangular block 610 may be intra-predicted from reconstructed samples of the L-shaped block 620. Fig. 7a shows reference samples that can be used for intra prediction of rectangular blocks under SPLIT RIGHT DOWN. In the reference samples shown in fig. 7a, the values of the left side reference samples located below the codec block 600 are copied from the reconstructed values of the lower boundary samples of the L-shaped block 620, and the values of the upper reference samples located to the right of the codec block 600 are copied from the reconstructed values of the right side boundary samples of the L-shaped block 620. The left reference samples may be samples located in one or more columns and the right reference samples may be samples located in one or more rows.

Similarly, in the case of split_left_up, the upper LEFT rectangular block 610 may have been reconstructed prior to predicting the L-shaped block 620 within the codec block 600. That is, when intra prediction is performed on the L-shaped blocks 620 within the codec block 600, reconstructed samples of the rectangular blocks 610 within the codec block 600 and reconstructed samples of left and upper blocks adjacent to the codec block 600 may be utilized. Accordingly, the rectangular block 610 may be intra-predicted from the reference samples adjacent to the codec block 600, and then the L-shaped block 620 may be intra-predicted from the reference samples adjacent to the codec block 600 and the reconstructed samples of the rectangular block 610. Fig. 7b shows reference samples that may be used for intra prediction of L-shaped block 620 in SPLIT LEFT UP.

In the case of split_right_up and split_left_down, L-shaped block 620 may be intra-predicted from reference samples adjacent to codec block 600, and rectangular block 610 may be intra-predicted from reconstructed samples of L-shaped block 620, or vice versa.

In another embodiment, the codec block 600 of video data is divided into two blocks including a rectangular block 610 and an L-shaped block 620. In this case, before intra prediction is performed on any one of the rectangular block 610 and the L-shaped block 620 (e.g., a block including [0,0] samples of the codec block 600), the other block may have been copied by inter prediction or intra block copy.

For example, in the case of SPLIT RIGHT DOWN, the rectangular block 610 located in the lower RIGHT corner may have been reconstructed by inter prediction or intra block copy before the L-shaped block 620 within the codec block 600 is predicted. That is, when intra prediction is performed on the L-shaped blocks 620 within the codec block 600, reconstructed samples of the rectangular blocks 610 within the codec block 600 and reconstructed samples of left and upper blocks adjacent to the codec block 600 may be utilized. Accordingly, the L-shaped block 620 may be intra-predicted from reference samples of neighboring blocks adjacent to the codec block 600 and reconstructed samples of the rectangular block 610 within the codec block 600.

Similarly, in the case of the split_left_up, the L-shaped block 620 located in the lower right corner may have been reconstructed by inter prediction or intra block copy before the prediction of the rectangular block 610 within the codec block 600. That is, when intra prediction is performed on the rectangular block 610 within the codec block 600, reconstructed samples of the L-shaped block 620 within the codec block 600 and reconstructed samples of the left block and the upper block adjacent to the codec block 600 may be utilized. Accordingly, the rectangular block 610 may be intra-predicted from reference samples of neighboring blocks adjacent to the codec block 600 and reconstructed samples of the L-shaped block 620 within the codec block 600.

In this embodiment, the video encoder and video decoder may be configured to perform bilinear interpolation based on reconstructed samples of neighboring blocks that are contiguous with the codec block 600 and reconstructed samples of the rectangular block 610 within the codec block 600 in order to determine the predicted value of the L-shaped block 620 at split_right_down. Further, the video encoder and video decoder may be configured to perform bilinear interpolation based on reconstructed samples of neighboring blocks adjacent to the codec block 600 and reconstructed samples of the L-shaped block 620 within the codec block 600 in order to determine a prediction value of the rectangular block 610 under the split_left_up.

Similarly, in the case of split_right_up and split_left_down, rectangular block 610 may have been reconstructed by inter prediction or intra block copy before predicting L-shaped block 620 within codec block 600. The L-shaped block 620 may be intra-predicted from reconstructed samples of neighboring blocks adjacent to the codec block 600 and reconstructed samples of the rectangular block 610 within the codec block 600.

Fig. 8a is a conceptual diagram illustrating bilinear interpolation performed on an L-shaped block of a codec block under split_right_down. Fig. 8b is a conceptual diagram illustrating bilinear interpolation performed on rectangular blocks of a codec block under split_left_up. As shown in fig. 8a and 8b, the size of the codec block is 8×8, and the size of the rectangular block is 4×4.

Referring to fig. 8a, under split_right_down, a predicted value for a given position within an L-shaped block in a codec block may be determined by performing bilinear interpolation using values of four corresponding boundary samples, including: (1) reconstructed values of boundary samples within a left block that adjoins the codec block, (2) reconstructed values of boundary samples within an upper block that adjoins the codec block, (3) predicted values of boundary samples (bottom or right) within an L-shaped block in the codec block, and (4) reconstructed values of boundary samples (left or upper) within a rectangular block in the codec block. Two of the four corresponding boundary samples are located in the same column as the predicted samples of the L-shaped block and the other two are located in the same row as the predicted samples of the L-shaped block.

Here, the predicted value of the bottom boundary sample within the codec block may be copied from the reconstructed value of the boundary sample L within the left block adjacent to the codec block or the left boundary sample L' within the rectangular block. The predicted value of the right side edge sample within the codec block may be copied from the reconstructed value of whichever of the boundary sample T within the block above the codec block or the upper boundary sample T' within the rectangular block in the codec block is closer. Alternatively, the predicted value of the right side boundary sample within the codec block may be generated by linear interpolation of the reconstructed value of the boundary sample L and the reconstructed value of the boundary sample L ', and the predicted value of the right side boundary sample within the codec block may be generated by linear interpolation of the reconstructed value of the boundary sample T and the reconstructed value of the boundary sample T'.

Referring to fig. 8b, in the split_left_up, a predicted value of a given position within a rectangular block in a codec block can be determined by performing bilinear interpolation using values of four corresponding boundary samples including: (1) reconstructed values of boundary samples within a left block that adjoins the codec block, (2) reconstructed values of boundary samples within an upper block that adjoins the codec block, (3) reconstructed values of boundary samples within an L-shaped block that adjoins a lower boundary of a rectangular block in the codec block, and (4) reconstructed values of boundary samples within an L-shaped block that adjoins a right boundary of a rectangular block in the codec block. Two of the four corresponding boundary samples are located in the same column as the predicted samples of the rectangular block and the other two are located in the same row as the predicted samples of the rectangular block.

Here, instead of the reconstructed values of a pair of boundary samples within an L-shaped block, the predicted value (3-1) of the bottom boundary sample within a rectangular block and the predicted value (4-1) of the right side boundary sample within a rectangular block in a codec block may be utilized. The predicted values of the bottom boundary samples within the rectangular block may be copied from the reconstructed values of the contiguous boundary samples within the L-shaped block, and the predicted values of the right boundary samples within the rectangular block may be copied from the reconstructed values of the contiguous samples within the L-shaped block. The predicted value of the right edge samples within a rectangular block may be determined as an average of the reconstructed values of two contiguous boundary samples within an L-shaped block, or may be copied from any of these reconstructed values.

Under the partition type split_up, the prediction value PredSamples [ x ] [ y ] for the mxn rectangular block in the w×h codec block can be derived by bilinear interpolation, and as shown in equation 1:

[ equation 1]

PredSamples[x][y]＝(P _V [x][y]+P _H [x][y]+M*N)＞＞(Log ₂ (M)+Log ₂ (N)+1)

P _V [x][y]＝((N-1-y)*P[x][-1]+(y+1)*P[x][G-N])＜＜Log2(M)

P _H [x][y]＝((M-1-x)*P[-1][y]+(x+1)*P[W-M][y])＜＜Log2(N)

It should be appreciated that in the case of split_right_up and split_left_down, bilinear interpolation may be performed in a manner that is virtually identical or equivalent to split_right_down or split_left_up.

Fig. 9a to 9d show transform units that may be considered for a codec block partitioned with geometric blocks according to an embodiment of the present invention.

The transformation or inverse transformation of the residual signal of the codec block 600 may be performed in the same transform unit as the size of the codec block 600, regardless of the geometric block partition used to predict the codec block 600. For example, as in (a) of fig. 9a to 9d, prediction may be performed on the rectangular block 610 and the L-shaped block 620 divided by the w×h-sized codec block 600, and then, as in (b) of fig. 9a to 9d, transformation and inverse transformation of the residual block of the codec block 600 may be performed in a w×h-sized transformation unit.

However, prediction accuracy and residual signal characteristics may be different between two sub-blocks 610 and 620 in a codec block to which different prediction techniques are respectively applied. Therefore, when the geometric block division is applied to the codec blocks of the video data, it may be more advantageous to perform the transformation and inverse transformation of the two residual blocks corresponding to the two sub-blocks 610 and 620 separately.

As described above, within the codec block of video data, the L-shaped block 620 and the rectangular block 610 may be sequentially encoded and decoded in a predefined order. That is, the video decoder may start decoding of another block after decoding the L-shaped block 620 or the rectangular block 610. In this case, it is necessary to perform transformation and inverse transformation separately on residual blocks corresponding to the rectangular block 610 and the L-shaped block 620, into which the codec block is divided. In a configuration in which transformation and inverse transformation are separately performed on residual blocks corresponding to the rectangular block 610 and the L-shaped block 620, into which the codec block is divided, transformation units of the residual blocks of the L-shaped block should be further considered.

Fig. 9a shows a transform unit of a codec block 600 that can be considered for video data in the case of a partition type split_right_up, wherein the codec block is partitioned into a rectangular block 610 and an L-shaped block 620 adjacent to the lower RIGHT corner for prediction. Here, the size of the codec block is w×h, and the size of the rectangular block is m×n. The L-shaped block 620 is made up of samples located in the "H-N" column starting from the top of the codec block 600 and samples located in the "W-M" row starting from the left side of the codec block 600.

In an embodiment, as shown in (c) of fig. 9a, in order to transform a residual block corresponding to an L-shaped block 620 within a codec block 600, three transform units may be utilized, including a first transform unit having a width (W-M) and a height (N), a second transform unit having a width (M) and a height (H-W), and a third transform unit having a width (W-M) and a height (H-W). In another embodiment, as shown in (d) of fig. 9a, in order to transform a residual block corresponding to the L-shaped block 620 within the codec block 600, two transform units may be utilized, including a first transform unit having a width (M) and a height (H-W) and a second transform unit having a width (W-M) and a height (H). In yet another embodiment, as shown in fig. 9a (e), in order to transform a residual block corresponding to an L-shaped block 620 within a codec block 600, two transform units may be utilized, including a first transform unit having a width (W-M) and a height (N) and a second transform unit having a width (W) and a height (H-N).

Similarly, in the case of other division types, the L-shaped block 620 may be further divided into two rectangular areas or three rectangular areas, as shown in (c), (d), and (e), and two or three transform units may be used to transform or inverse transform the residual block corresponding to the L-shaped block 620. The transform order (or the order of the inverse transforms, or the order of the reconstructions) of the plurality of transform units of the L-shaped block 620 may be a z-scan order or an inverse z-scan order, or an agreed order between the video encoder and the video decoder.

Fig. 10 is a flowchart illustrating a method of encoding and decoding a block of video data according to an embodiment of the present invention. Accordingly, the video encoder may encode the blocks of video data according to the method shown in fig. 10, and the video decoder may decode the blocks of video data according to the method shown in fig. 10.

The video encoder and the video decoder may each determine that the block of video data is divided into an L-shaped block and a rectangular block (S1010). The video encoder may determine a partition type to be applied to a block of video data among a plurality of available partition types (S1020). The available segmentation types are distinguished by the relative position of the rectangular blocks within the blocks of video data. The video encoder may calculate RD costs and determine whether to encode blocks of video data with or without geometric partitioning. The video encoder may encode a 1-bit flag (e.g., new_split_flag) indicating whether to apply geometric block partitioning to a block of video data and an index indicating one of a plurality of partition types in a bitstream. The video decoder may decode the 1-bit flag and the index from the bitstream, determine whether to divide the block of the video data into L-shaped blocks and rectangular blocks based on the 1-bit flag (S1010), and determine a division type to be applied to the block of the video data based on the index (S1020).

The video encoder and the video decoder may each determine a pair of prediction techniques to be applied to the L-shaped block and the rectangular block based on the partition type of the block of video data (S1030). The pair of prediction techniques includes a first prediction technique for an L-shaped block and a second prediction technique for a rectangular block.

The video encoder may select the corresponding prediction techniques suitable for the L-shaped blocks and rectangular blocks from available prediction techniques, such as intra prediction, inter prediction, and Intra Block Copy (IBC). The video encoder may encode syntax elements in the bitstream that indicate two prediction techniques to be applied to the rectangular block and the L-shaped block. The video decoder may decode syntax elements indicating two prediction techniques to be applied to the rectangular block and the L-shaped block from the bitstream to determine a pair of prediction techniques to be applied to the rectangular block and the L-shaped block.

Alternatively, the pair of prediction techniques may be predefined corresponding to the partition type. Both of the pair of prediction techniques may be intra prediction. The pair of prediction techniques may be inter prediction or intra block copy and intra prediction. Here, in the case where a rectangular block adjoins the upper left corner of a block of video data, the video encoder and video decoder may consider (or infer) that the first prediction technique for an L-shaped block is inter prediction or intra block copy and the second prediction technique for a rectangular block is intra prediction. In the case where a rectangular block adjoins the lower right corner of a block of video data, a first prediction technique for an L-shaped block may be inferred as intra prediction, and a second prediction technique for a rectangular block may be inferred as inter prediction or intra block copy. In the case where a rectangular block adjoins the lower left corner or upper right corner of a block of video data, a first prediction technique for an L-shaped block may be inferred as inter prediction or intra block copy, and a second prediction technique for a rectangular block may be inferred as intra prediction.

The video encoder and the video decoder may each generate a first prediction value of samples within the L-shaped block by applying a first prediction technique to the L-shaped block (S1040). The video encoder and the video decoder may each generate a second prediction value of samples within the rectangular block by applying a second prediction technique to the rectangular block (S1050).

In an embodiment, in a case where a rectangular block adjoins an upper left corner of a block of video data, the first prediction value of a sample within an L-shaped block may be intra-predicted by using a reconstructed value of a sample within a block adjacent to the block of video data and a reconstructed value of a sample within the rectangular block. Accordingly, the rectangular block may be encoded and decoded prior to prediction of the L-shaped block. In the case where the rectangular block adjoins the lower right corner of the block of video data, the second prediction value of the samples within the rectangular block may be intra-predicted by using the reconstructed values of the samples within the L-shaped block. Accordingly, the rectangular block may be encoded and decoded prior to prediction of the L-shaped block.

In another embodiment, where a rectangular block abuts the top left corner of a block of video data, a first prediction technique for an L-shaped block may be inferred as inter prediction or intra block copy, and a second prediction technique for a rectangular block may be inferred as intra prediction. In this case, the second prediction value of the sample within the rectangular block may be intra-predicted by using the reconstructed value of the sample within the block adjacent to the block of video data and the reconstructed value of the sample within the L-shaped block. Accordingly, the rectangular block may be encoded and decoded prior to prediction of the L-shaped block. In the case where the rectangular block adjoins the lower right corner of the block of video data, the second prediction value of the samples within the rectangular block may be intra-predicted by using the reconstructed values of the samples within the L-shaped block. Accordingly, the rectangular block may be encoded and decoded prior to prediction of the L-shaped block. In the case where a rectangular block adjoins the lower right corner of a block of video data, a first prediction technique for an L-shaped block may be inferred as intra prediction, and a second prediction technique for a rectangular block may be inferred as inter prediction or intra block copy. In this case, the first prediction value of the sample within the L-shaped block may be intra-predicted by using the reconstructed value of the sample within the block adjacent to the block of video data and the reconstructed value of the sample within the rectangular block. Accordingly, the rectangular block may be encoded and decoded prior to prediction of the L-shaped block.

The video encoder may use the first and second predictors to encode L-shaped blocks and rectangular blocks of the block of video data, and the video decoder may use the first and second predictors to decode L-shaped blocks and rectangular blocks of the block of video data (S1060). As described above, the encoding and decoding order of the L-shaped block and the rectangular block may be different according to the partition type.

The video encoder may generate an array of residual values for the L-shaped block by subtracting the first prediction value from the original values of the samples within the L-shaped block. The video encoder may generate an array of transform coefficients by performing a transform of the array of residual values and generate an array of quantized transform coefficients by performing quantization of the array of transform coefficients. The video encoder may entropy encode the array of quantized transform coefficients of the L-shaped block. The video encoder may entropy encode the array of quantized transform coefficients of the rectangular block in a manner equivalent to an L-shaped block.

The video decoder may entropy decode an array of quantized transform coefficients of the L-shaped blocks in the bitstream. The video decoder may generate an array of transform coefficients by inverse quantizing the array of quantized transform coefficients. An array of residual values in the pixel domain may be generated by inverse transforming an array of transform coefficients in the frequency domain. The video decoder may generate a reconstructed block of the L-shaped block by adding the first predictor to an array of residual values of the L-shaped block. The video decoder may generate a reconstructed block of rectangular blocks in a manner equivalent to an L-shaped block.

It will be appreciated that the above embodiments may be implemented in many different ways. The functions described in one or more examples may be implemented as hardware, software, firmware, or any combination thereof. The functional components described in this specification have been labeled as units, in order to more particularly emphasize their potentially independent implementation.

In another aspect, the various methods or functions described in the present invention may be implemented as instructions stored in a non-volatile recording medium, which may be read and executed by one or more processors. Non-volatile recording media include all types of recording devices that store data in a form readable by a computer system, for example. For example, nonvolatile recording media include storage media such as erasable programmable read-only memory (EPROM), electrically erasable programmable read-only memory (EEPROM), flash memory drives, optical disk drives, magnetic hard disk drives, and Solid State Drives (SSD).

Although the embodiments have been described for illustrative purposes, those of ordinary skill in the art will appreciate that various modifications and changes are possible without departing from the spirit and scope of the embodiments. For brevity and clarity, the embodiments have been described. Accordingly, it should be understood by those of ordinary skill that the scope of the embodiments is not limited by the embodiments explicitly described above, but is included within the claims and their equivalents.

Cross Reference to Related Applications

The present application claims priority from korean patent application No.10-2020-0158996, filed on 11 months 24 in 2020, and korean patent application No.10-2021-0162262, filed on 11 months 23 in 2021, the entire contents of which are incorporated herein by reference.

Claims

1. A method for encoding a block of video data, the method comprising:

determining that a block of video data is divided into an L-shaped block and a rectangular block;

determining a segmentation type based on the relative position of the rectangular block within the block of video data;

determining a pair of prediction techniques to be applied to the L-shaped block and the rectangular block based on the partition type, the pair of prediction techniques including a first prediction technique for the L-shaped block and a second prediction technique for the rectangular block;

generating a first prediction value of samples within the L-shaped block by applying a first prediction technique to the L-shaped block; and

a second prediction value for samples within the rectangular block is generated by applying a second prediction technique to the rectangular block.

2. The method of claim 1, wherein the pair of prediction techniques are predefined corresponding to a partition type.

3. The method of claim 1, wherein both of the pair of prediction techniques are intra-prediction.

4. The method of claim 3, wherein,

intra-predicting a first prediction value of a sample within an L-shaped block by using a reconstructed value of a sample within a block adjacent to the block of video data and a reconstructed value of a sample within the rectangular block in a case where the rectangular block adjoins an upper left corner of the block of video data, and

in the case where the rectangular block adjoins the lower right corner of the block of video data, the second prediction value of the samples within the rectangular block is intra-predicted by using the reconstructed values of the samples within the L-shaped block.

5. The method of claim 1, wherein the pair of prediction techniques are intra-prediction and inter-prediction or intra-block copy.

6. The method of claim 5, wherein, in the event that a rectangular block adjoins an upper left corner of a block of video data, a first prediction technique for an L-shaped block is inferred as inter prediction or intra block copy, and a second prediction technique for a rectangular block is inferred as intra prediction.

7. The method of claim 6, wherein the second prediction value of the sample within the rectangular block is intra-predicted by using a reconstructed value of the sample within a block adjacent to the block of video data and a reconstructed value of the sample within the L-shaped block.

8. The method of claim 5, wherein, in the event that a rectangular block adjoins a lower right corner of a block of video data, a first prediction technique for an L-shaped block is inferred as intra prediction and a second prediction technique for a rectangular block is inferred as inter prediction or intra block copy.

9. The method of claim 8, wherein the first prediction value of the sample within the L-shaped block is intra-predicted by using a reconstructed value of the sample within a block adjacent to the block of video data and a reconstructed value of the sample within the rectangular block.

10. The method of claim 1, wherein, in the event that a rectangular block adjoins a lower left corner and an upper right corner of a block of video data, a first prediction technique for an L-shaped block is inferred as inter prediction or intra block copy, and a second prediction technique for a rectangular block is inferred as intra prediction.

11. A method for decoding a block of video data, the method comprising:

12. The method of claim 11, wherein the pair of prediction techniques are predefined corresponding to a partition type.

13. The method of claim 11, wherein both of the pair of prediction techniques are intra-prediction.

14. The method according to claim 13, wherein:

15. The method of claim 11, wherein the pair of prediction techniques are intra-prediction and inter-prediction or intra-block copy.

16. The method of claim 15, wherein, in the event that a rectangular block adjoins an upper left corner of a block of video data, a first prediction technique for an L-shaped block is inferred as inter prediction or intra block copy, and a second prediction technique for a rectangular block is inferred as intra prediction.

17. The method of claim 16, wherein the second prediction value of the sample within the rectangular block is intra-predicted by using a reconstructed value of the sample within a block adjacent to the block of video data and a reconstructed value of the sample within the L-shaped block.

18. The method of claim 15, wherein, in the event that a rectangular block adjoins a lower right corner of a block of video data, a first prediction technique for an L-shaped block is inferred as intra prediction and a second prediction technique for a rectangular block is inferred as inter prediction or intra block copy.

19. The method of claim 18, wherein the first prediction value of the sample within the L-shaped block is intra-predicted by using a reconstructed value of the sample within a block adjacent to the block of video data and a reconstructed value of the sample within a rectangular block.

20. The method of claim 11, wherein in the case where a rectangular block adjoins a lower left corner and an upper right corner of a block of video data, a first prediction technique for an L-shaped block is inferred as inter prediction or intra block copy, and a second prediction technique for a rectangular block is inferred as intra prediction.