Image encoding / decoding method, device, and recording medium for storing bitstream

Abstract

Provided are an image encoding / decoding method, a device, a recording medium for storing a bitstream, and a transmission method. The image decoding method may comprise the steps of: determining a candidate list for intra prediction of a current block according to whether an intra prediction mode of an adjacent block of the current block is a matrix-based position-dependent intra prediction mode; determining an intra prediction mode of the current block on the basis of the candidate list of the current block; and predicting the current block according to the intra prediction mode of the current block.

Description

Video encoding / decoding method, device, and recording medium storing a bitstream

[0001] The present disclosure relates to an image encoding / decoding method, an apparatus, and a recording medium storing a bitstream. Specifically, the present disclosure relates to an image encoding / decoding method, an apparatus, and a recording medium storing a bitstream that utilizes in-frame prediction.

[0002] Recently, the demand for high-resolution, high-quality video, such as UHD (Ultra High Definition) video, has been increasing across various application fields. As video data becomes higher in resolution and quality, the relative volume of data increases compared to conventional video data; consequently, transmission and storage costs increase when video data is transmitted using existing wired or wireless broadband lines or stored using existing storage media. To address these issues arising from the increase in video data resolution and quality, high-efficiency video encoding and decoding technologies for video with higher resolution and quality are required.

[0003] Intra-frame prediction is a method that predicts samples of a block by referencing samples of the same picture. In the case of picture I, where there is no picture to reference, the block is encoded / decoded solely through intra-frame prediction; therefore, there is a strong demand to improve the accuracy of intra-frame prediction. Accordingly, various intra-frame prediction methods are being discussed to enhance the accuracy of intra-frame prediction.

[0004] The present disclosure aims to provide an image encoding / decoding method and apparatus with improved encoding / decoding efficiency.

[0005] In addition, the present disclosure aims to provide a recording medium storing a bitstream generated by an image decoding method or device according to the present disclosure.

[0006] A video decoding method according to one embodiment of the present disclosure may be characterized by comprising the steps of: determining a candidate list for in-frame prediction of the current block based on whether the in-frame prediction mode of an adjacent block of the current block is a matrix-based position-dependent in-frame prediction mode; determining an in-frame prediction mode of the current block based on the candidate list of the current block; and predicting the current block according to the in-frame prediction mode of the current block.

[0007] According to one embodiment, when the in-screen prediction mode of an adjacent block of the current block is a matrix-based position-dependent in-screen prediction mode, the in-screen prediction mode of the adjacent block is not included in the candidate list of the current block, and when the in-screen prediction mode of an adjacent block of the current block is not a matrix-based position-dependent in-screen prediction mode, the in-screen prediction mode of the adjacent block may be included in the candidate list of the current block.

[0008] According to one embodiment, when the in-screen prediction mode of the first adjacent block of the current block is a matrix-based position-dependent in-screen prediction mode, the in-screen prediction mode of the first adjacent block is not included in the candidate list of the current block, and when the in-screen prediction mode of the second adjacent block adjacent to the first adjacent block is not a matrix-based position-dependent in-screen prediction mode, the in-screen prediction mode of the second adjacent block may be included in the candidate list of the current block instead of the in-screen prediction mode of the first adjacent block.

[0009] According to one embodiment, when the in-screen prediction mode of an adjacent block of the current block is a matrix-based position-dependent in-screen prediction mode, the in-screen prediction mode of the adjacent block is not included in the candidate list of the current block, and among a plurality of blocks adjacent to the adjacent block, the in-screen prediction mode of a block whose in-screen prediction mode is not a matrix-based position-dependent in-screen prediction mode may be included in the candidate list of the current block instead of the in-screen prediction mode of the adjacent block.

[0010] According to one embodiment, when the intra-frame prediction mode of an adjacent block of the current block is a matrix-based position-dependent intra-frame prediction mode, the intra-frame prediction mode of the adjacent block is not included in the candidate list of the current block, and according to decoder-side intra-frame prediction (DIMD), a DIMD intra-frame prediction mode derived based on the adjacent block or a template of the adjacent block may be included in the candidate list of the current block instead of the intra-frame prediction mode of the adjacent block.

[0011] According to one embodiment, the in-screen prediction mode induced by the DIMD mode may be induced by the gradient of the pixels of the adjacent block, or by the gradient of the pixels of the adjacent block template or the frequency of occurrence of the prediction mode.

[0012] According to one embodiment, the candidate list includes a first candidate list and a second candidate list, wherein the first candidate list includes an in-screen prediction mode with a high probability of occurrence for the current block among the in-screen prediction mode candidates of the current block, and the second candidate list may include an in-screen prediction mode with a low probability of occurrence for the current block among the in-screen prediction mode candidates of the current block.

[0013] According to one embodiment, when the in-screen prediction mode of an adjacent block of the current block is a matrix-based position-dependent in-screen prediction mode, the in-screen prediction mode of the adjacent block is not included in the first candidate list of the current block, and according to DIMD, a DIMD in-screen prediction mode derived based on the adjacent block or the template of the adjacent block may be included in the first candidate list of the current block instead of the in-screen prediction mode of the adjacent block.

[0014] According to one embodiment, when the in-screen prediction mode of an adjacent block of the current block is a matrix-based position-dependent in-screen prediction mode, the in-screen prediction mode of the adjacent block is not included in the first candidate list of the current block, and after an in-screen prediction mode that is not a matrix-based position-dependent in-screen prediction mode of a plurality of adjacent blocks of the current block is assigned to the first candidate list, if the candidate mode slot of the first candidate list according to the in-screen prediction mode is not filled, then according to DIMD, a DIMD in-screen prediction mode derived based on the adjacent block or the template of the adjacent block may be included in the first candidate list.

[0015] According to one embodiment, if the number of prediction modes within a DIMD screen derived according to DIMD is greater than the number of empty candidate mode slots in the first candidate list, the prediction modes within the DIMD screen may be included in the first candidate list in order of smallest template cost until all empty candidate mode slots in the first candidate list are filled.

[0016] According to one embodiment, when the in-frame prediction mode of an adjacent block of the current block is a matrix-based position-dependent in-frame prediction mode, the in-frame prediction mode of the adjacent block is included in the first candidate list of the current block, and according to DIMD, a DIMD in-frame prediction mode derived based on the adjacent block or the template of the adjacent block may be included in the second candidate list.

[0017] According to one embodiment, when the in-frame prediction mode of an adjacent block of the current block is a matrix-based position-dependent in-frame prediction mode, according to DIMD, a DIMD in-frame prediction mode derived based on the adjacent block or a template of the adjacent block is included in the first candidate list, and the in-frame prediction mode of the adjacent block may be included in the second candidate list of the current block.

[0018] According to one embodiment, when a matrix-based position-dependent in-screen prediction mode is applied to the current block, the candidate list of the current block is configured to include only the matrix-based position-dependent in-screen prediction mode, and when the in-screen prediction mode of an adjacent block of the current block is a matrix-based position-dependent in-screen prediction mode, the in-screen prediction mode of the adjacent block is included in the candidate list of the current block, and when the in-screen prediction mode of an adjacent block of the current block is not a matrix-based position-dependent in-screen prediction mode, the in-screen prediction mode of the adjacent block may be included in the candidate list of the current block.

[0019] According to one embodiment, when the in-screen prediction mode of the first adjacent block of the current block is not a matrix-based position-dependent in-screen prediction mode, the in-screen prediction mode of the first adjacent block is not included in the candidate list of the current block, and when the in-screen prediction mode of the second adjacent block adjacent to the first adjacent block is a matrix-based position-dependent in-screen prediction mode, the in-screen prediction mode of the second adjacent block may be included in the candidate list of the current block instead of the in-screen prediction mode of the first adjacent block.

[0020] A video encoding method according to one embodiment of the present disclosure may include the steps of determining a candidate list for in-frame prediction of the current block based on whether the in-frame prediction mode of an adjacent block of the current block is a matrix-based position-dependent in-frame prediction mode, encoding the in-frame prediction mode of the current block based on the candidate list of the current block, and predicting the current block according to the in-frame prediction mode of the current block.

[0021] A non-transient computer-readable recording medium according to one embodiment of the present disclosure can store a bitstream generated by an image encoding method according to various embodiments of the present disclosure.

[0022] A bitstream transmission method according to one embodiment of the present disclosure includes the step of transmitting the bitstream, and can transmit a bitstream generated by an image encoding method according to various embodiments of the present disclosure.

[0023] The features briefly summarized above regarding the present disclosure are merely exemplary aspects of the detailed description of the present disclosure that follows and do not limit the scope of the present disclosure.

[0024] According to the present disclosure, an image encoding / decoding method and apparatus with improved encoding / decoding efficiency may be provided.

[0025] Additionally, according to the present disclosure, a method for determining the most probable mode (MPM) list by considering matrix-based position-dependent in-frame prediction may be provided.

[0026] In addition, according to the present disclosure, by providing an adaptive MPM list for the current block, the data required for in-frame prediction is efficiently compressed, thereby improving the efficiency of in-frame prediction.

[0027] The effects obtainable from the present disclosure are not limited to those mentioned above, and other unmentioned effects will be clearly understood by those skilled in the art to which the present disclosure belongs from the description below.

[0028] FIG. 1 is a block diagram showing the configuration according to one embodiment of an encoding device to which the present disclosure applies.

[0029] FIG. 2 is a block diagram showing the configuration according to one embodiment of a decoding device to which the present disclosure is applied.

[0030] FIG. 3 is a schematic diagram illustrating a video coding system to which the present disclosure can be applied.

[0031] Figure 4 shows a template around the current block used for matrix-based position-dependent in-frame prediction.

[0032] Figure 5 shows the surrounding blocks of the current block that are referenced in the creation of the MPM list of the current block.

[0033] FIG. 6 shows the surrounding blocks of the current block and the templates of the surrounding blocks that are referenced in the generation of the MPM list of the current block.

[0034] FIG. 7 is a flowchart illustrating an image decoding method according to one embodiment of the present disclosure.

[0035] FIG. 8 is a drawing illustrating an exemplary content streaming system to which an embodiment according to the present disclosure can be applied.

[0036] A video decoding method according to one embodiment of the present disclosure may be characterized by comprising the steps of: determining a candidate list for in-frame prediction of the current block based on whether the in-frame prediction mode of an adjacent block of the current block is a matrix-based position-dependent in-frame prediction mode; determining an in-frame prediction mode of the current block based on the candidate list of the current block; and predicting the current block according to the in-frame prediction mode of the current block.

[0037] The present disclosure is subject to various modifications and may have various embodiments, and specific embodiments are illustrated in the drawings and described in detail in the detailed description. However, this is not intended to limit the present disclosure to specific embodiments, and it should be understood that it includes all modifications, equivalents, and substitutions that fall within the spirit and scope of the present disclosure. Similar reference numerals in the drawings refer to the same or similar functions across various aspects. The shapes and sizes of elements in the drawings may be provided illustratively for clearer explanation. The detailed description of the exemplary embodiments described below refers to the accompanying drawings, which illustrate specific embodiments. These embodiments are described in sufficient detail to enable those skilled in the art to practice the embodiments. It should be understood that various embodiments are different but need not be mutually exclusive. For example, specific shapes, structures, and characteristics described herein may be implemented in other embodiments without departing from the spirit and scope of the present disclosure in relation to one embodiment. It should also be understood that the location or arrangement of individual components within each disclosed embodiment may be changed without departing from the spirit and scope of the embodiment. Accordingly, the following detailed description is not intended to be taken in a limiting sense, and the scope of exemplary embodiments is limited only by the appended claims, together with all equivalents to those claimed therein, provided they are properly described.

[0038] In this disclosure, terms such as first, second, etc. may be used to describe various components, but said components should not be limited by said terms. Such terms are used solely for the purpose of distinguishing one component from another. For example, without departing from the scope of this disclosure, the first component may be named the second component, and similarly, the second component may be named the first component. The term "and / or" includes a combination of a plurality of related described items or any of a plurality of related described items.

[0039] The components shown in the embodiments of the present disclosure are depicted independently to represent different characteristic functions and do not imply that each component consists of separate hardware or a single software unit. That is, each component is listed and included as a separate component for convenience of explanation; however, at least two of the components may be combined to form a single component, or a single component may be divided into multiple components to perform a function, and such integrated and separated embodiments of each component are included within the scope of the rights of the present disclosure as long as they do not deviate from the essence of the present disclosure.

[0040] The terms used in this disclosure are used merely to describe specific embodiments and are not intended to limit this disclosure. Singular expressions include plural expressions unless the context clearly indicates otherwise. Additionally, some components of this disclosure may not be essential components performing an essential function in this disclosure, but may be optional components merely for enhancing performance. This disclosure may be implemented by including only the components essential to embody the essence of this disclosure, excluding components used merely for performance enhancement, and a structure including only the essential components, excluding optional components used merely for performance enhancement, is also included within the scope of this disclosure.

[0041] In the embodiments, the term "at least one" may mean one of a number of 1 or more, such as 1, 2, 3, and 4. In the embodiments, the term "a plurality of" may mean one of a number of 2 or more, such as 2, 3, and 4.

[0042] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. In describing the embodiments of this specification, if it is determined that a detailed description of related known configurations or functions may obscure the gist of this specification, such detailed description is omitted, and the same reference numerals are used for identical components in the drawings, and redundant descriptions of identical components are omitted.

[0043] Glossary

[0044] In the following, “image” may refer to a single picture constituting a video, or it may refer to the video itself. For example, “encoding and / or decoding of an image” may mean “encoding and / or decoding of an image”, and may also mean “encoding and / or decoding of one of the images constituting the video”.

[0045] In the following, "video" and "video" may be used interchangeably with the same meaning. Additionally, the target image may be an image to be encoded and / or an image to be decoded. Furthermore, the target image may be an input image fed into an encoding device and an input image fed into a decoding device. Here, the target image may have the same meaning as the current image.

[0046] In the following, the encoder and the image encoding device may be used interchangeably with each other.

[0047] In the following, the decoder and the image decoder may be used interchangeably with each other.

[0048] In the following, "image," "picture," "frame," and "screen" may be used interchangeably with the same meaning.

[0049] In the following, “target block” may be an encoding target block that is the target of encoding and / or a decoding target block that is the target of decoding. Additionally, the target block may be a current block that is the target of current encoding and / or decoding. For example, “target block” and “current block” may be used interchangeably.

[0050] In the following description, "block" and "unit" may be used interchangeably. Additionally, to distinguish it from a block, "unit" may refer to a block containing a luminance (Luma) component block and a corresponding chroma (Chroma) component block. For example, a Coding Tree Unit (CTU) may consist of a single luminance component (Y) coding tree block (CTB) and two chroma component (Cb, Cr) coding tree blocks associated with it.

[0051] In the following, “sample,” “pixel,” and “pixel” may be used interchangeably with the same meaning. Here, a sample may represent a basic unit constituting a block.

[0052] In the following, “inter” and “inter-screen” may be used interchangeably with the same meaning.

[0053] In the following, “intra” and “in-screen” may be used interchangeably with the same meaning.

[0054]

[0055] FIG. 1 is a block diagram showing the configuration according to one embodiment of an encoding device to which the present disclosure applies.

[0056] The encoding device (100) may be an encoder, a video encoding device, or an image encoding device. The video may include one or more images. The encoding device (100) may sequentially encode one or more images.

[0057] Referring to FIG. 1, the encoding device (100) may include an image segmentation unit (110), an intra prediction unit (120), a motion prediction unit (121), a motion compensation unit (122), a switch (115), a subtractor (113), a converter (130), a quantization unit (140), an entropy encoding unit (150), an inverse quantization unit (160), an inverse converter (170), an adder (117), a filter unit (180), and a reference picture buffer (190).

[0058] Additionally, the encoding device (100) can generate a bitstream containing encoded information through encoding of an input image and can output the generated bitstream. The generated bitstream can be stored on a computer-readable recording medium or streamed via a wired / wireless transmission medium.

[0059] The video segmentation unit (110) can divide the input video into various forms to increase the efficiency of video encoding / decoding. That is, the input video consists of multiple pictures, and a single picture can be processed by hierarchically dividing it for compression efficiency, parallel processing, etc. For example, a single picture can be divided into one or more tiles or slices and then divided again into multiple CTUs (Coding Tree Units). Alternatively, a single picture can first be divided into multiple sub-pictures defined as groups of rectangular slices, and each sub-picture can be divided into the said tiles / slices. Here, the sub-pictures can be utilized to support the function of partially and independently encoding / decoding and transmitting the picture. Since multiple sub-pictures can each be restored individually, they have the advantage of being easy to edit in applications that configure multi-channel inputs into a single picture. In addition, the tiles can be divided horizontally to create bricks. Here, a brick can be utilized as the basic unit of parallel processing within a picture. Additionally, a single CTU can be recursively partitioned into a Quadtree (QT), and the terminal node of the partition can be defined as a Coding Unit (CU). The CU can be divided into a Prediction Unit (PU) and a Transform Unit (TU) to perform prediction and partitioning. Meanwhile, the CU can be utilized as the prediction unit and / or the transformation unit itself. Here, for flexible partitioning, each CTU can be recursively partitioned into a Multi-Type Tree (MTT) as well as a Quadtree (QT). The partitioning of the CTU into a Multi-Type Tree can begin at the terminal node of the QT, and the MTT can be composed of a Binary Tree (BT) and a Triple Tree (TT).For example, the MTT structure can be classified into vertical binary splitting mode (SPLIT_BT_VER), horizontal binary splitting mode (SPLIT_BT_HOR), vertical ternary splitting mode (SPLIT_TT_VER), and horizontal ternary splitting mode (SPLIT_TT_HOR). Additionally, when splitting, the minimum block size (MinQTSize) of the quad tree for the luminance block can be set to 16x16, the maximum block size (MaxBtSize) of the binary tree to 128x128, and the maximum block size (MaxTtSize) of the triple tree to 64x64. Furthermore, the minimum block size (MinBtSize) of the binary tree and the minimum block size (MinTtSize) of the triple tree can be set to 4x4, and the maximum depth (MaxMttDepth) of the multi-type tree can be set to 4. Additionally, to increase the encoding efficiency of the I slice, a dual tree can be applied that uses different CTU splitting structures for the luminance and chrominance components. On the other hand, in P and B slices, the luminance and color difference CTBs (Coding Tree Blocks) within the CTU can be divided into a single tree that shares a coding tree structure.

[0060] The encoding device (100) may perform encoding on an input image in an intra mode and / or inter mode. Alternatively, the encoding device (100) may perform encoding on an input image in a third mode other than the intra mode and inter mode (e.g., IBC mode, Palette mode, etc.). However, if the third mode has functional characteristics similar to the intra mode or inter mode, it may be classified as an intra mode or inter mode for convenience of explanation. In this disclosure, the third mode will be classified and described separately only when a specific description of the third mode is required.

[0061] When intra mode is used as the prediction mode, the switch (115) can be switched to intra, and when inter mode is used as the prediction mode, the switch (115) can be switched to inter. Here, intra mode may mean an intra-frame prediction mode, and inter mode may mean an inter-frame prediction mode. The encoding device (100) can generate a prediction block for an input block of an input image. Additionally, after the prediction block is generated, the encoding device (100) can encode a residual block using the residual of the input block and the prediction block. The input image may be referred to as the current image that is the subject of current encoding. The input block may be referred to as the current block that is the subject of current encoding or the encoding target block.

[0062] When the prediction mode is an intra mode, the intra prediction unit (120) may use a sample of a block that has already been encoded / decoded around the current block as a reference sample. The intra prediction unit (120) may perform spatial prediction for the current block using the reference sample and generate prediction samples for the input block through spatial prediction. Here, intra prediction may mean intra-frame prediction.

[0063] In the intra prediction method, non-directional prediction modes such as DC mode and Planar mode, and directional prediction modes (e.g., 65 directions) may be applied. Here, the intra prediction method can be expressed as an intra prediction mode or an intra-frame prediction mode.

[0064] When the prediction mode is an inter mode, the motion prediction unit (121) can search for the region that best matches the input block from the reference image during the motion prediction process and derive a motion vector using the searched region. At this time, the search region can be used as the region. The reference image can be stored in the reference picture buffer (190). Here, the reference image can be stored in the reference picture buffer (190) when encoding / decoding of the reference image is processed.

[0065] The motion compensation unit (122) can generate a prediction block for the current block by performing motion compensation using a motion vector. Here, inter-prediction may mean inter-frame prediction or motion compensation.

[0066] The motion prediction unit (121) and motion compensation unit (122) can generate a prediction block by applying an interpolation filter to a portion of the reference image when the value of the motion vector does not have an integer value. To perform inter-frame prediction or motion compensation, based on the encoding unit, it can determine whether the motion prediction and motion compensation method of the prediction unit included in the corresponding encoding unit is a Skip Mode, Merge Mode, Advanced Motion Vector Prediction (AMVP) Mode, or Intra Block Copy (IBC) Mode, and can perform inter-frame prediction or motion compensation according to each mode.

[0067] In addition, based on the above-mentioned inter-frame prediction method, the AFFINE mode of sub-PU-based prediction, the SbTMVP (Subblock-based Temporal Motion Vector Prediction) mode, and the MMVD (Merge with MVD) mode and GPM (Geometric Partitioning Mode) mode of PU-based prediction may be applied. Furthermore, to improve the performance of each mode, HMVP (History based MVP), PAMVP (Pairwise Average MVP), CIIP (Combined Intra / Inter Prediction), AMVR (Adaptive Motion Vector Resolution), BDOF (Bi-Directional Optical-Flow), BCW (Bi-predictive with CU Weights), LIC (Local Illumination Compensation), TM (Template Matching), OBMC (Overlapped Block Motion Compensation), etc. may be applied.

[0068] Among these, AFFINE mode is a technology used in both AMVP and MERGE modes and also offers high encoding efficiency. Conventional video coding standards have the disadvantage of failing to properly compensate for real-world movements, such as zoom in / out and rotation, because they perform Motion Compensation (MC) by considering only the translation of blocks. To address this, a 4-parameter affine motion model using two control point motion vectors (CPMV) and a 6-parameter affine motion model using three control point motion vectors can be applied to inter-prediction. Here, CPMV is a vector representing one of the affine motion models of the top-left, top-right, or bottom-left corners of the current block.

[0069] The subtractor (113) can generate a residual block using the difference between the input block and the prediction block. The residual block may also be referred to as a residual signal. The residual signal may represent the difference between the original signal and the prediction signal. Alternatively, the residual signal may be a signal generated by transforming, quantizing, or both transforming and quantizing the difference between the original signal and the prediction signal. The residual block may be a residual signal in block units.

[0070] The transformation unit (130) can generate a transform coefficient by performing a transform on the remaining block and output the generated transform coefficient. Here, the transform coefficient may be a coefficient value generated by performing a transform on the remaining block. When a transform skip mode is applied, the transformation unit (130) may skip the transform on the remaining block.

[0071] A quantized level can be generated by applying quantization to a conversion coefficient or a residual signal. In the following embodiments, the quantized level may also be referred to as a conversion coefficient.

[0072] For example, a 4x4 luminance residual block generated through intra prediction can be transformed using a Discrete Sine Transform (DST)-based basis vector, while the remaining residual blocks can be transformed using a Discrete Cosine Transform (DCT)-based basis vector. Additionally, the transformation blocks for a single block can be divided into a quad tree form using Residual Quad Tree (RQT) technology, and after performing transformation and quantization on each transformation block divided by RQT, a coded block flag (cbf) can be transmitted to increase coding efficiency in the case where all coefficients become zero.

[0073] As another alternative, the Multiple Transform Selection (MTS) technique can be applied to perform transformations using multiple transformation bases selectively. In other words, instead of dividing a CU into TUs via RQT, a function similar to TU division can be performed using the Sub-block Transform (SBT) technique. Specifically, SBT is applied only to inter-frame prediction blocks and, unlike RQT, divides the current block into ½ or ¼ sizes in the vertical or horizontal direction, and then performs a transformation on only one of the blocks. For example, if divided vertically, a transformation can be performed on the leftmost or rightmost block, and if divided horizontally, a transformation can be performed on the topmost or bottommost block.

[0074] In addition, Low Frequency Non-Separable Transform (LFNST), a secondary transform technique that further transforms the residual signal converted to the frequency domain through DCT or DST, can also be applied. LFNST performs additional transformation on the 4x4 or 8x8 low-frequency region in the upper left corner, thereby allowing the residual coefficients to be concentrated in the upper left corner.

[0075] The quantization unit (140) can generate a quantized level by quantizing a transformation coefficient or residual signal according to a quantization parameter (QP, Quantization parameter) and can output the generated quantized level. At this time, the quantization unit (140) can quantize the transformation coefficient using a quantization matrix.

[0076] For example, a quantizer using QP values ​​from 0 to 51 can be used. Alternatively, if the image size is larger and higher coding efficiency is required, QP values ​​from 0 to 63 can be used. Additionally, a Dependent Quantization (DQ) method using two quantizers instead of a single one can be applied. DQ performs quantization using two quantizers (e.g., Q0, Q1), but can be applied so that the quantizer to be used for the next transform coefficient is selected based on the current state through a state transition model, even without signaling information regarding the use of a specific quantizer.

[0077] The entropy encoding unit (150) can generate a bitstream and output a bitstream by performing entropy encoding according to a probability distribution on values ​​calculated by the quantization unit (140) or coding parameter values ​​calculated during the encoding process. The entropy encoding unit (150) can perform entropy encoding on information regarding a sample of an image and information for decoding an image. For example, information for decoding an image may include syntax elements, etc.

[0078] When entropy coding is applied, a small number of bits are allocated to symbols with a high probability of occurrence and a large number of bits are allocated to symbols with a low probability of occurrence, thereby representing the symbols and reducing the size of the bit sequence for the symbols to be encoded. The entropy coding unit (150) may use encoding methods such as exponential Golomb, CAVLC (Context-Adaptive Variable Length Coding), and CABAC (Context-Adaptive Binary Arithmetic Coding) for entropy coding. For example, the entropy coding unit (150) may perform entropy coding using a Variable Length Coding (VLC) table. In addition, the entropy encoding unit (150) may perform arithmetic encoding using the derived binarization method, probability model, and context model after deriving a binarization method of the target symbol and a probability model of the target symbol / bin.

[0079] In this regard, when applying CABAC, in order to reduce the size of the probability table stored in the decoder, the table probability update method may be changed to a table update method using a simple formula. In addition, two different probability models may be used to obtain more accurate symbol probability values.

[0080] The entropy encoding unit (150) can convert a 2-dimensional block form coefficient into a 1-dimensional vector form through a transform coefficient scanning method to encode a transform coefficient level (quantized level).

[0081] Coding parameters may include information (flags, indexes, etc.) that is encoded in the encoding device (100) and signaled to the decoding device (200), such as syntax elements, as well as information derived during the encoding process or decoding process, and may refer to information required when encoding or decoding images.

[0082] Here, signaling a flag or index may mean that in an encoder, the corresponding flag or index is entropy encoded and included in a bitstream, and in a decoder, the corresponding flag or index is entropy decoded from the bitstream.

[0083] The encoded current image can be used as a reference image for other images processed later. Accordingly, the encoding device (100) can restore or decode the encoded current image again, and can store the restored or decoded image as a reference image in the reference picture buffer (190).

[0084] The quantized level can be dequantized in the dequantization unit (160) and inverse transformed in the inverse transform unit (170). The dequantized and / or inverse transformed coefficients can be added to the prediction block through the adder (117). A reconstructed block can be generated by adding the dequantized and / or inverse transformed coefficients and the prediction block. Here, the dequantized and / or inverse transformed coefficients refer to coefficients for which at least one of dequantization and inverse transformation has been performed, and may refer to the reconstructed residual block. The dequantization unit (160) and the inverse transform unit (170) can be performed as the reverse process of the quantization unit (140) and the transformation unit (130).

[0085] The restoration block may pass through a filter section (180). The filter section (180) may apply a deblocking filter, Sample Adaptive Offset (SAO), Adaptive Loop Filter (ALF), Bilateral filter (BIF), LMCS (Luma Mapping with Chroma Scaling), etc., to the restoration sample, restoration block, or restoration image as a whole or part of the filtering technique. The filter section (180) may also be referred to as an in-loop filter. In this case, the term in-loop filter is also used as a name that excludes LMCS.

[0086] Deblocking filters can remove block distortion occurring at the boundaries between blocks. To determine whether to perform deblocking, the decision to apply the filter to the current block can be made based on samples contained in a few columns or rows within the block. When applying a deblocking filter to a block, different filters can be applied depending on the required deblocking filtering intensity.

[0087] To compensate for encoding errors using a sample adaptive offset, an appropriate offset value can be added to the sample value. The sample adaptive offset can correct the offset from the original image on a sample-by-sample basis for the deblocked image. One method may be to divide the samples included in the image into a certain number of regions, determine the region to be offset, and apply the offset to that region, or to apply the offset by considering the edge information of each sample.

[0088] A bilateral filter (BIF) can also correct the offset from the original image on a sample-by-sample basis for the deblocked image.

[0089] An adaptive loop filter can perform filtering based on a comparison of the reconstructed image and the original image. After dividing the samples included in the image into predetermined groups, a filter to be applied to each group can be determined, thereby performing filtering differently for each group. Information regarding whether to apply an adaptive loop filter can be signaled per coding unit (CU), and the shape and filter coefficients of the adaptive loop filter to be applied may vary depending on each block.

[0090] In LMCS (Luma Mapping with Chroma Scaling), Luma mapping (LM) refers to remapping luminance values ​​through a piece-wise linear model, and Chroma scaling (CS) refers to a technique that scales the residual values ​​of the chrominance component according to the average luminance value of the predicted signal. In particular, LMCS can be utilized as an HDR correction technique that reflects the characteristics of HDR (High Dynamic Range) video.

[0091] The restored block or restored image that has passed through the filter unit (180) can be stored in the reference picture buffer (190). The restored block that has passed through the filter unit (180) may be part of the reference image. That is to say, the reference image may be a restored image composed of the restored blocks that have passed through the filter unit (180). The stored reference image may subsequently be used for inter-frame prediction or motion compensation.

[0092] FIG. 2 is a block diagram showing the configuration according to one embodiment of a decoding device to which the present disclosure is applied.

[0093] The decoding device (200) may be a decoder, a video decoding device, or an image decoding device.

[0094] Referring to FIG. 2, the decoding device (200) may include an entropy decoding unit (210), an inverse quantization unit (220), an inverse transformation unit (230), an intra prediction unit (240), a motion compensation unit (250), an adder (201), a switch (203), a filter unit (260), and a reference picture buffer (270).

[0095] The decoding device (200) can receive a bitstream output from the encoding device (100). The decoding device (200) can receive a bitstream stored in a computer-readable recording medium or a bitstream stream streamed through a wired / wireless transmission medium. The decoding device (200) can perform decoding on the bitstream in intra mode or inter mode. Additionally, the decoding device (200) can generate a restored image or a decoded image through decoding and can output the restored image or the decoded image.

[0096] If the prediction mode used for decoding is intra mode, the switch (203) can be switched to intra. If the prediction mode used for decoding is inter mode, the switch (203) can be switched to inter.

[0097] The decoding device (200) can decode the input bitstream to obtain a reconstructed residual block and generate a prediction block. Once the reconstructed residual block and the prediction block are obtained, the decoding device (200) can generate a reconstructed block to be decoded by adding the reconstructed residual block and the prediction block. The block to be decoded may be referred to as the current block.

[0098] The entropy decoding unit (210) can generate symbols by performing entropy decoding according to the probability distribution of the bitstream. The generated symbols may include symbols in the form of quantized levels. Here, the entropy decoding method may be the inverse process of the entropy encoding method described above.

[0099] The entropy decoding unit (210) can convert a one-dimensional vector-shaped coefficient into a two-dimensional block-shaped coefficient through a conversion coefficient scanning method to decode a conversion coefficient level (quantized level).

[0100] The quantized level can be dequantized in the dequantization unit (220) and inversely transformed in the inverse transformation unit (230). The quantized level can be generated as a restored residual block as a result of performing dequantization and / or inverse transformation. At this time, the dequantization unit (220) can apply a quantization matrix to the quantized level. The dequantization unit (220) and the inverse transformation unit (230) applied to the decoding device can apply the same technology as the dequantization unit (160) and the inverse transformation unit (170) applied to the aforementioned encoding device.

[0101] When an intra mode is used, the intra prediction unit (240) can generate a prediction block by performing a spatial prediction on the current block using sample values ​​of already decoded blocks around the block to be decoded. The intra prediction unit (240) applied to the decoding device can apply the same technology as the intra prediction unit (120) applied to the aforementioned encoding device.

[0102] When an inter mode is used, the motion compensation unit (250) can generate a prediction block by performing motion compensation on the current block using a motion vector and a reference image stored in the reference picture buffer (270). The motion compensation unit (250) can generate a prediction block by applying an interpolation filter to a portion of the reference image when the value of the motion vector does not have an integer value. To perform motion compensation, it can be determined whether the motion compensation method of the prediction unit included in the corresponding encoding unit is a skip mode, merge mode, AMVP mode, or current picture reference mode based on the encoding unit, and motion compensation can be performed according to each mode. The motion compensation unit (250) applied to the decoder can apply the same technology as the motion compensation unit (122) applied to the aforementioned encoding unit.

[0103] The adder (201) can generate a restored block by adding the restored residual block and the prediction block. The filter unit (260) can apply at least one of the following to the restored block or the restored image: an inverse-LMCS, a deblocking filter, a sample adaptive offset, and an adaptive loop filter. The filter unit (260) applied to the decoder can apply the same filtering technology as the filter unit (180) applied to the aforementioned encoding device.

[0104] The filter unit (260) can output a restored image. The restored block or the restored image can be stored in a reference picture buffer (270) and used for inter-frame prediction. The restored block that has passed through the filter unit (260) may be part of the reference image. That is to say, the reference image may be a restored image composed of the restored blocks that have passed through the filter unit (260). The stored reference image may subsequently be used for inter-frame prediction or motion compensation.

[0105] FIG. 3 is a schematic diagram illustrating a video coding system to which the present disclosure can be applied.

[0106] A video coding system according to one embodiment may include an encoding device (10) and a decoding device (20). The encoding device (10) may transmit encoded video and / or image information or data to the decoding device (20) via a digital storage medium or network in the form of a file or streaming.

[0107] An encoding device (10) according to one embodiment may include a video source generation unit (11), an encoding unit (12), and a transmission unit (13). A decoding device (20) according to one embodiment may include a receiving unit (21), a decoding unit (22), and a rendering unit (23). The encoding unit (12) may be called a video / image encoding unit, and the decoding unit (22) may be called a video / image decoding unit. The transmission unit (13) may be included in the encoding unit (12). The receiving unit (21) may be included in the decoding unit (22). The rendering unit (23) may include a display unit, and the display unit may be composed of a separate device or an external component.

[0108] The video source generation unit (11) can acquire video / image through a process of capturing, synthesizing, or generating video / image. The video source generation unit (11) may include a video / image capture device and / or a video / image generation device. The video / image capture device may include, for example, one or more cameras, a video / image archive containing previously captured video / image, etc. The video / image generation device may include, for example, a computer, a tablet, and a smartphone, etc., and can generate video / image (electronically). For example, a virtual video / image may be generated through a computer, etc., in which case the video / image capture process may be replaced by a process of generating related data.

[0109] The encoding unit (12) can encode the input video / image. The encoding unit (12) can perform a series of procedures such as prediction, conversion, and quantization for compression and encoding efficiency. The encoding unit (12) can output the encoded data (encoded video / image information) in the form of a bitstream. The detailed configuration of the encoding unit (12) can also be configured in the same way as the encoding device (100) of FIG. 1 described above.

[0110] The transmission unit (13) can transmit encoded video / image information or data output in the form of a bitstream to the receiving unit (21) of the decoding device (20) via a digital storage medium or network in the form of a file or streaming. The digital storage medium may include various storage media such as USB, SD, CD, DVD, Blu-ray, HDD, SSD, etc. The transmission unit (13) may include elements for creating a media file through a predetermined file format and elements for transmission via a broadcasting / communication network. The receiving unit (21) can extract / receive the bitstream from the storage medium or network and transmit it to the decoding unit (22).

[0111] The decoding unit (22) can decode a video / image by performing a series of procedures such as inverse quantization, inverse transformation, and prediction corresponding to the operation of the encoding unit (12). The detailed configuration of the decoding unit (22) can also be configured to be identical to the decoding device (200) of FIG. 2 described above.

[0112] The rendering unit (23) can render the decoded video / image. The rendered video / image can be displayed through the display unit.

[0113]

[0114] Hereinafter, with reference to FIGS. 4 to 6, a method for generating an MPM list considering matrix-based position-dependent in-screen prediction according to various embodiments of the present disclosure is described in detail.

[0115] In the present disclosure, a non-directional in-frame prediction mode refers to an in-frame prediction mode that lacks directionality, such as a planar mode and a DC mode. In the present disclosure, a directional in-frame prediction mode refers to an in-frame prediction mode that predicts a current sample by referring to a reference sample located in the prediction direction from the current sample, such as a vertical mode, a horizontal mode, or a diagonal mode.

[0116] The Matrix-based position-dependent intra-prediction (Matrix-based PDP) mode is an intra-prediction mode generated by the prediction signal of the current block, in which a matrix of weights defined according to the current block shape and the intra-prediction mode is multiplied by the neighboring reference template of the current block. As shown in Fig. 4, the matrix of weights is applied to the reference samples of the L-shaped templates surrounding the current block.

[0117] In FIG. 4, W and H represent the width and height of the current block (400), respectively. And in the template (410), T1 and T2 represent the height of the upper template and the width of the left template, respectively. Also, r represents a reference sample within the template (410) of the current block. The prediction signal generated from matrix-based position-dependent in-frame prediction is calculated using Equation 1.

[0118] [Mathematical Formula 1]

[0119]

[0120] In Equation 1, k represents the index of a reference sample within the template, and F(x,y) and P(x,y) represent the matrix of weighted values ​​and the prediction signal, respectively. For example, for a block where both the height and width are 16 or less, the template size can be determined to be 2. In this case, matrix-based position-dependent in-frame prediction can be performed for the in-frame prediction modes of the current block, such as Mode 0, Mode 1, and Mode (2+2xk). Here, the range of k can be k = {0, 1, 2, … , 32}.

[0121] If a block has a height or width greater than 16, the template size can be determined to be 1. And matrix-based position-dependent intra-frame prediction can be performed for the current block's intra-frame prediction modes of mode 0, mode 1, and mode (2+4xl). For example, the range of l can be l = {0, 1, 2, … , 16}.

[0122] To improve the efficiency of encoding and decoding Intra-prediction mode (IPM) information, a Most Probable Mode List (MPM list) containing intra-prediction modes that are likely to be applied to the current block may be generated. Then, intra-prediction mode information may be encoded and decoded using the MPM list. According to various embodiments, the MPM list may include intra-prediction modes of neighboring blocks of the current block and intra-prediction modes derived from the intra-prediction modes of neighboring blocks of the current block. According to various embodiments, intra-prediction modes of prediction directions adjacent to the prediction directions of the intra-prediction modes of neighboring blocks may be included in the MPM list.

[0123] If matrix-based position-dependent in-frame prediction is allowed for the current block, when the height and width of the current block are both less than or equal to a predetermined size, in-frame prediction modes 0, 1, and (2+2xk) may be replaced with matrix-based position-dependent in-frame prediction modes instead of the directional prediction mode and non-directional prediction mode predefined for each index number. If matrix-based position-dependent in-frame prediction is allowed for the current block, when either the height or the width of the current block is greater than a predetermined size, in-frame prediction modes 0, 1, and (2+4xl) may be replaced with matrix-based position-dependent in-frame prediction modes instead of the directional prediction mode and non-directional prediction mode predefined for each index number.

[0124] In a matrix-based position-dependent in-frame prediction mode, a matrix of weighted values ​​according to the directionality of the in-frame prediction mode of the corresponding index number can be applied to the in-frame prediction. For example, in a matrix-based position-dependent in-frame prediction mode corresponding to the in-frame prediction mode of index 6, a matrix of weighted values ​​according to the directionality of the in-frame prediction mode of index 6 can be used.

[0125] Directionality may be weakened in matrix-based position-dependent intra-frame prediction modes. Consequently, the directional component of a matrix-based position-dependent intra-frame prediction mode may have characteristics different from the directional component of the corresponding directional intra-frame prediction mode. Therefore, if a matrix-based position-dependent intra-frame prediction mode is applied to the surrounding blocks of the current block, it may not be efficient to include the intra-frame prediction modes of the surrounding blocks in the current block's MPM list when constructing the current block's MPM list by referencing the surrounding blocks.

[0126] With reference to FIGS. 5 and 6 in the present disclosure, various embodiments are proposed for generating an MPM list of a block by considering the characteristics of a matrix-based position-dependent in-frame prediction mode. FIGS. 5 and 6 show a template area around the current block that is referenced to determine the MPM list of the current block, together with the current block.

[0127] According to one embodiment, in order to construct an MPM list of the current block, the in-screen prediction mode of the neighboring blocks of the current block may be searched in a predetermined order. The range of neighboring blocks of the current block may include not only blocks immediately adjacent to the current block but also blocks located a distance of less than or equal to a predetermined number of pixels from the current block.

[0128] According to one embodiment, if a neighboring block is predicted according to a matrix-based position-dependent in-frame prediction mode, the in-frame prediction mode of the neighboring block may not be added to the MPM list. For example, with reference to FIG. 5, neighboring blocks of the current block (500) may be searched in the order of L4, A4, L5, A5, AL of the template (510). When adding the in-frame prediction mode of the neighboring block to the MPM list, if the in-frame prediction mode of block A4 is a matrix-based position-dependent in-frame prediction mode, the in-frame prediction mode of block A4 may not be added to the MPM list.

[0129] According to one embodiment, if a neighbor block is predicted according to a matrix-based position-dependent in-frame prediction mode, the in-frame prediction mode of an adjacent block of that neighbor block may be added to the MPM list instead of the in-frame prediction mode of that neighbor block. However, the in-frame prediction mode of an adjacent block of that neighbor block may be added to the MPM list only if the adjacent block of that neighbor block is not a matrix-based position-dependent in-frame prediction mode.

[0130] For example, referring to FIG. 5, the surrounding blocks of the current block may be searched in the order of L4, A4, L5, A5, AL of the template (510). If block AL is predicted in a matrix-based position-dependent in-frame prediction mode, the in-frame prediction mode of any block A1 or L1 immediately adjacent to block AL may be added to the MPM list. In this case, block A1 or L1 must not be in a matrix-based position-dependent in-frame prediction mode. The search order of adjacent blocks may be determined arbitrarily.

[0131] According to one embodiment, if a neighbor block is predicted according to a matrix-based position-dependent intra-frame prediction mode, the intra-frame prediction mode of the neighbor block may not be added to the MPM list. Instead, a template of the neighbor block or a DIMD intra-frame prediction mode derived by applying a decoder-side intra-frame mode derivation (DIMD) method to the neighbor block may be added to the MPM list.

[0132] According to one embodiment, the MPM list may include a PMPM (Primary most probable mode) list and an SMPM (Secondary most probable mode) list. The intra-prediction modes of the PMPM list and the SMPM list are distinguished according to their probability of occurrence.

[0133] According to one embodiment, if a neighboring block is predicted according to a matrix-based position-dependent in-frame prediction mode, the in-frame prediction mode of the neighboring block may not be added to the PMPM list. Instead, a DIMD in-frame prediction mode derived by applying a decoder-side in-frame mode derivation method to the template of the neighboring block or to the neighboring block may be added to the PMPM list. For example, referring to FIG. 6, if the neighboring blocks of the current block are searched in the order of L4, A4, L5, A5, AL of the template (610) and the A4 block is predicted according to a matrix-based position-dependent in-frame prediction mode, a DIMD in-frame prediction mode derived by applying DIMD to the A4 block (620) or the template (630) of the A4 block may be added to the PMPM list. At this time, the shape and size of the template (630) of the A4 block may be determined arbitrarily.

[0134] According to one embodiment, in order to construct the PMPM list of the current block, the in-frame prediction mode of the surrounding blocks of the current block may be searched according to a predetermined order. If the block is a matrix-based position-dependent in-frame prediction mode, the in-frame prediction mode of the block may not be added to the PMPM list. If the in-frame prediction mode of the surrounding blocks is a matrix-based position-dependent in-frame prediction mode and the N candidate mode slots of the PMPM list are not all filled, the in-frame prediction mode derived by applying a decoder-side in-frame mode derivation method to the surrounding blocks or the templates of the surrounding blocks may be added to the PMPM list. If the number of in-frame prediction modes of neighboring blocks to which matrix-based position-dependent in-frame prediction modes are not applied, and the number of in-frame prediction modes derived from neighboring blocks to which matrix-based position-dependent in-frame prediction modes are applied, is greater than N, then in-frame prediction modes derived from neighboring blocks to which matrix-based position-dependent in-frame prediction modes are applied can be added to the PMPM list in order of decreasing template cost until all N candidate mode slots of the PMPM list are filled.

[0135] According to one embodiment, if the neighboring blocks of the current block are in a matrix-based position-dependent intra-frame prediction mode, the intra-frame prediction mode of the corresponding block may be added to the PMPM list. Then, when configuring the SMPM list after generating the PMPM list, the intra-frame prediction mode derived by applying a decoder-side intra-frame mode derivation method to the neighboring blocks to which the matrix-based position-dependent intra-frame prediction mode is applied, or to the template of the corresponding neighboring blocks, may be added to the SMPM list. If the M candidate mode slots allocated to the SMPM list are not filled even after adding the derived intra-frame prediction mode, the intra-frame prediction mode derived by applying DIMD to the template of the current block may be added to the SMPM list.

[0136] According to one embodiment, if the neighboring blocks of the current block are in a matrix-based position-dependent intra-frame prediction mode, the intra-frame prediction mode derived by applying a decoder-side intra-frame mode derivation method to the neighboring blocks or the template of the neighboring blocks may be added to the PMPM list. Additionally, the intra-frame prediction mode of the neighboring blocks may be added to the SMPM list.

[0137] In the above embodiment, when configuring the MPM list, the number of surrounding blocks searched by the current block and the search order may be determined arbitrarily. Alternatively, in the above embodiment, when configuring the MPM list, the number of surrounding blocks searched by the current block and the search order may be determined according to the shape and size of the current block and / or the on-screen prediction mode.

[0138] According to the above embodiment, candidate modes within the final MPM list can be rearranged within the MPM list by considering a cost value calculated based on a template. At this time, the cost value can be calculated using one of the cost functions: SAD (sum of absolute differences), SATD (sum of absolute transformed differences), SSD (sum of squared differences), and MR-SAD (mean removed sum of absolute differences).

[0139] Matrix-based position-dependent in-frame prediction modes may have weaker directionality or possess directionality with different characteristics compared to the corresponding directional in-frame prediction modes. Therefore, if a matrix-based position-dependent in-frame prediction mode is applied to the current block, the MPM list of the current block may be generated to include the matrix-based position-dependent in-frame prediction mode, rather than including directional or non-directional in-frame prediction modes.

[0140] Accordingly, if the in-screen prediction mode of the current block is a matrix-based position-dependent in-screen prediction mode, with reference to FIG. 5, the surrounding blocks of the current block (500) are searched in the order of L4, A4, L5, A5, AL in the template (510), and among the in-screen prediction modes of the surrounding blocks, the matrix-based position-dependent in-screen prediction mode can be added to the MPM list. And among the in-screen prediction modes of the surrounding blocks, modes that are not matrix-based position-dependent in-screen prediction modes may not be added to the MPM list.

[0141] According to one embodiment, if a neighbor block is predicted according to a non-directional in-frame prediction mode or a directional in-frame prediction mode, a matrix-based position-dependent in-frame prediction mode of an adjacent block of that neighbor block may be added to the MPM list instead of the in-frame prediction mode of that neighbor block. If an adjacent block of that neighbor block is in a non-directional in-frame prediction mode or a directional in-frame prediction mode, the in-frame prediction mode of an adjacent block of that neighbor block may not be added to the MPM list.

[0142] For example, referring to FIG. 5, the surrounding blocks of the current block (500) can be searched in the order L4, A4, L5, A5, AL in the template (510). If the AL block is predicted in a non-directional in-frame prediction mode or a directional in-frame prediction mode, the matrix-based position-dependent in-frame prediction mode of any block A1 or L1 immediately adjacent to the AL block can be added to the MPM list. The search order of adjacent blocks can be determined arbitrarily.

[0143] FIG. 7 is a flowchart illustrating an image decoding method according to an embodiment of the present disclosure. The image decoding method of FIG. 7 can be performed by an image decoding device.

[0144] In step 710, a candidate list for the in-frame prediction of the current block is determined based on whether the in-frame prediction mode of the adjacent blocks of the current block is a matrix-based position-dependent in-frame prediction mode. The determination of the candidate list in step 702 can be performed according to various embodiments.

[0145] According to one embodiment, when the in-screen prediction mode of an adjacent block of the current block is a matrix-based position-dependent in-screen prediction mode, the in-screen prediction mode of the adjacent block is not included in the candidate list of the current block. Conversely, when the in-screen prediction mode of an adjacent block of the current block is not a matrix-based position-dependent in-screen prediction mode, the in-screen prediction mode of the adjacent block may be included in the candidate list of the current block.

[0146] According to one embodiment, when the in-screen prediction mode of a first adjacent block of the current block is a matrix-based position-dependent in-screen prediction mode and the in-screen prediction mode of a second adjacent block adjacent to the first adjacent block is not a matrix-based position-dependent in-screen prediction mode, the in-screen prediction mode of the second adjacent block may be included in the candidate list of the current block instead of the in-screen prediction mode of the first adjacent block.

[0147] According to one embodiment, when the in-screen prediction mode of an adjacent block of the current block is a matrix-based position-dependent in-screen prediction mode, the in-screen prediction mode of a block among a plurality of blocks adjacent to the adjacent block that is not a matrix-based position-dependent in-screen prediction mode may be included in the candidate list of the current block instead of the in-screen prediction mode of the adjacent block.

[0148] According to one embodiment, when the intra-mode prediction mode of an adjacent block of the current block is a matrix-based position-dependent intra-mode prediction mode, a DIMD intra-mode prediction mode derived based on the adjacent block or the template of the adjacent block may be included in the candidate list of the current block instead of the intra-mode prediction mode of the adjacent block according to Decoder-side intra-mode derivation (DIMD). The intra-mode prediction mode derived according to the DIMD mode may be derived by the gradient of the pixels of the adjacent block, or by the gradient of the pixels of the adjacent block template or the frequency of occurrence of the prediction mode.

[0149] According to one embodiment, the candidate list includes a first candidate list and a second candidate list, the first candidate list includes an in-screen prediction mode that has a high probability of occurrence for the current block among the in-screen prediction mode candidates of the current block, and the second candidate list includes an in-screen prediction mode that has a low probability of occurrence for the current block among the in-screen prediction mode candidates of the current block.

[0150] According to one embodiment, when the in-frame prediction mode of an adjacent block of the current block is a matrix-based position-dependent in-frame prediction mode, the in-frame prediction mode of the adjacent block is not included in the first candidate list of the current block, and according to DIMD, a DIMD in-frame prediction mode derived based on the adjacent block or the template of the adjacent block may be included in the first candidate list of the current block instead of the in-frame prediction mode of the adjacent block.

[0151] According to one embodiment, when the in-screen prediction mode of an adjacent block of the current block is a matrix-based position-dependent in-screen prediction mode, the in-screen prediction mode of the adjacent block is not included in the first candidate list of the current block, and after an in-screen prediction mode that is not a matrix-based position-dependent in-screen prediction mode of a plurality of adjacent blocks of the current block is assigned to the first candidate list, if the candidate mode slot of the first candidate list according to the in-screen prediction mode is not filled, then according to DIMD, an in-screen prediction mode derived based on the adjacent block or the template of the adjacent block may be included in the first candidate list. And if the number of DIMD in-screen prediction modes derived according to DIMD is greater than the number of empty candidate mode slots in the first candidate list, then DIMD in-screen prediction modes may be included in the first candidate list in order of smallest template cost until all empty candidate mode slots in the first candidate list are filled.

[0152] According to one embodiment, when the in-frame prediction mode of an adjacent block of the current block is a matrix-based position-dependent in-frame prediction mode, the in-frame prediction mode of the adjacent block is included in a first candidate list of the current block, and according to DIMD, a DIMD in-frame prediction mode derived based on the adjacent block or the template of the adjacent block may be included in a second candidate list.

[0153] According to one embodiment, when the in-frame prediction mode of an adjacent block of the current block is a matrix-based position-dependent in-frame prediction mode, according to DIMD, an in-frame prediction mode derived based on the adjacent block or a template of the adjacent block is included in a first candidate list, and the in-frame prediction mode of the adjacent block may be included in a second candidate list of the current block.

[0154] According to one embodiment, when a matrix-based position-dependent in-screen prediction mode is applied to the current block, the candidate list of the current block is configured to include only the matrix-based position-dependent in-screen prediction mode, and when the in-screen prediction mode of an adjacent block of the current block is a matrix-based position-dependent in-screen prediction mode, the in-screen prediction mode of the adjacent block is included in the candidate list of the current block, and when the in-screen prediction mode of an adjacent block of the current block is not a matrix-based position-dependent in-screen prediction mode, the in-screen prediction mode of the adjacent block may not be included in the candidate list of the current block.

[0155] According to one embodiment, when the in-screen prediction mode of the first adjacent block of the current block is not a matrix-based position-dependent in-screen prediction mode, the in-screen prediction mode of the first adjacent block is not included in the candidate list of the current block, and when the in-screen prediction mode of the second adjacent block adjacent to the first adjacent block is a matrix-based position-dependent in-screen prediction mode, the in-screen prediction mode of the second adjacent block may be included in the candidate list of the current block instead of the in-screen prediction mode of the first adjacent block.

[0156] In step 720, the in-screen prediction mode of the current block is determined based on the above candidate list of the current block.

[0157] In step 730, the current block is predicted according to the in-screen prediction mode of the current block.

[0158] Meanwhile, the method for determining the candidate list in step 710 of FIG. 7 can be performed in the same way in the video encoding method. In the video encoding method, a bitstream can be generated by encoding the in-frame prediction mode of the current block based on the candidate list. The bitstream can be stored on a non-transient computer-readable recording medium and can also be transmitted (or streamed).

[0159] FIG. 8 is a drawing illustrating an exemplary content streaming system to which an embodiment according to the present disclosure can be applied.

[0160] As illustrated in FIG. 8, a content streaming system to which an embodiment of the present disclosure is applied may largely include an encoding server, a streaming server, a web server, a media storage, a user device, and a multimedia input device.

[0161] The encoding server described above compresses content input from multimedia input devices, such as smartphones, cameras, and CCTVs, into digital data to generate a bitstream and transmits it to the streaming server. As another example, if multimedia input devices, such as smartphones, cameras, and CCTVs, generate the bitstream directly, the encoding server may be omitted.

[0162] The bitstream may be generated by a video encoding method and / or video encoding device to which an embodiment of the present disclosure is applied, and the streaming server may temporarily store the bitstream during the process of transmitting or receiving the bitstream.

[0163] The streaming server transmits multimedia data to a user device based on a user request through a web server, and the web server can act as a medium to inform the user of available services. When a user requests a desired service from the web server, the web server transmits it to the streaming server, and the streaming server can transmit multimedia data to the user. At this time, the content streaming system may include a separate control server, and in this case, the control server can perform the role of controlling commands and responses between each device within the content streaming system.

[0164] The streaming server can receive content from a media storage and / or an encoding server. For example, when receiving content from the encoding server, the content can be received in real time. In this case, to provide a seamless streaming service, the streaming server can store the bitstream for a certain period of time.

[0165] Examples of the above user devices may include mobile phones, smartphones, laptop computers, digital broadcasting terminals, PDAs (personal digital assistants), PMPs (portable multimedia players), navigation systems, slate PCs, tablet PCs, ultrabooks, wearable devices (e.g., smartwatches, smart glasses, HMDs (head-mounted displays)), digital TVs, desktop computers, digital signage, etc.

[0166] Each server within the above-mentioned content streaming system can be operated as a distributed server, and in this case, data received from each server can be processed in a distributed manner.

[0167]

[0168] The above embodiments may be performed in the same or a corresponding way in the encoding device and the decoding device. Additionally, an image may be encoded / decoded using at least one of the above embodiments or a combination of at least one.

[0169] The order in which the above embodiments are applied may differ between the encoding device and the decoder. Alternatively, the order in which the above embodiments are applied may be the same between the encoding device and the decoder.

[0170] The above embodiments may be performed for each of the luminance and chrominance signals. Alternatively, the above embodiments for the luminance and chrominance signals may be performed in the same way.

[0171] In the above embodiments, methods are described based on flowcharts as a series of steps or units; however, the present disclosure is not limited to the order of steps, and some steps may occur in a different order or simultaneously with other steps as described above. Furthermore, those skilled in the art will understand that the steps shown in the flowcharts are not exclusive, other steps may be included, or one or more steps of the flowcharts may be omitted without affecting the scope of the present disclosure.

[0172] The above embodiments may be implemented in the form of program instructions that can be executed through various computer components and recorded on a computer-readable recording medium. The computer-readable recording medium may include program instructions, data files, data structures, etc., either alone or in combination. The program instructions recorded on the computer-readable recording medium may be those specifically designed and configured for the present disclosure, or they may be those known and available to those skilled in the art of computer software.

[0173] The bitstream generated by the encoding method according to the above embodiment may be stored in a non-transient computer-readable recording medium. Additionally, the bitstream stored in the non-transient computer-readable recording medium may be decoded by the decoding method according to the above embodiment.

[0174] Herein, examples of computer-readable recording media include magnetic media such as hard disks, floppy disks, and magnetic tapes; optical recording media such as CD-ROMs and DVDs; magneto-optical media such as floptical disks; and hardware devices specifically configured to store and execute program instructions such as ROM, RAM, and flash memory. Examples of program instructions include machine code, such as that generated by a compiler, as well as high-level language code that can be executed by a computer using an interpreter, etc. The hardware devices may be configured to operate as one or more software modules to perform processing according to the present disclosure, and vice versa.

[0175] Although the present disclosure has been described above with specific details such as specific components, limited embodiments, and drawings, this is provided only to aid in a more comprehensive understanding of the present disclosure and is not limited to the above embodiments, and a person skilled in the art to which the present disclosure belongs can make various modifications and variations from this description.

[0176] Accordingly, the scope of the present disclosure is not limited to the embodiments described above, and all things equivalent or equivalently modified to the claims set forth below, as well as the claims set forth below, shall be considered to be within the scope of the scope of the present disclosure.

[0177] The present disclosure may be used in an apparatus for encoding / decoding images and a recording medium storing a bitstream.

Claims

1. A step of determining a candidate list for in-frame prediction of the current block based on whether the in-frame prediction mode of the adjacent block of the current block is a matrix-based position-dependent in-frame prediction mode; A step of determining an in-screen prediction mode of the current block based on the candidate list of the current block; An image decoding method comprising the step of predicting the current block according to the in-frame prediction mode of the current block.

2. In Paragraph 1, When the in-screen prediction mode of an adjacent block of the above current block is a matrix-based position-dependent in-screen prediction mode, the in-screen prediction mode of the above adjacent block is not included in the candidate list of the above current block, and A video decoding method characterized in that when the in-frame prediction mode of an adjacent block of the current block is not a matrix-based position-dependent in-frame prediction mode, the in-frame prediction mode of the adjacent block is included in the candidate list of the current block.

3. In Paragraph 1, When the in-screen prediction mode of the first adjacent block of the above current block is a matrix-based position-dependent in-screen prediction mode, the in-screen prediction mode of the above first adjacent block is not included in the candidate list of the above current block, and A video decoding method characterized in that, when the in-frame prediction mode of a second adjacent block adjacent to the first adjacent block is not a matrix-based position-dependent in-frame prediction mode, the in-frame prediction mode of the second adjacent block is included in the candidate list of the current block instead of the in-frame prediction mode of the first adjacent block.

4. In Paragraph 1, When the in-screen prediction mode of an adjacent block of the above current block is a matrix-based position-dependent in-screen prediction mode, the in-screen prediction mode of the above adjacent block is not included in the candidate list of the above current block, and A video decoding method characterized in that, among a plurality of blocks adjacent to the aforementioned adjacent block, the in-frame prediction mode of a block whose in-frame prediction mode is not a matrix-based position-dependent in-frame prediction mode is included in the candidate list of the current block instead of the in-frame prediction mode of the aforementioned adjacent block.

5. In Paragraph 1, When the in-screen prediction mode of an adjacent block of the above current block is a matrix-based position-dependent in-screen prediction mode, the in-screen prediction mode of the above adjacent block is not included in the candidate list of the above current block, and A video decoding method characterized by, according to decoder-side intra-mode derivation (DIMD), an intra-mode prediction mode derived based on the adjacent block or the template of the adjacent block is included in the candidate list of the current block instead of the intra-mode prediction mode of the adjacent block.

6. In Paragraph 5, The intra-frame prediction mode derived according to the above DIMD mode is, Induced by the gradient of the pixels of the aforementioned adjacent blocks, or An image decoding method characterized by being derived by the frequency of occurrence of the gradient or prediction mode of pixels of the above-mentioned adjacent block template.

7. In Paragraph 1, The above candidate list includes a first candidate list and a second candidate list, and The above first candidate list includes an in-screen prediction mode that has a high probability of appearance for the current block among the in-screen prediction mode candidates of the current block, and An image decoding method characterized in that the second candidate list includes an in-frame prediction mode with a low probability of occurrence for the current block among the in-frame prediction mode candidates of the current block.

8. In Paragraph 7, When the in-screen prediction mode of an adjacent block of the above current block is a matrix-based position-dependent in-screen prediction mode, the in-screen prediction mode of the above adjacent block is not included in the above first candidate list of the above current block, and A video decoding method characterized in that, according to DIMD, an in-frame prediction mode derived based on the adjacent block or the template of the adjacent block is included in the first candidate list of the current block instead of the in-frame prediction mode of the adjacent block.

9. In Paragraph 7, When the in-screen prediction mode of an adjacent block of the above current block is a matrix-based position-dependent in-screen prediction mode, the in-screen prediction mode of the above adjacent block is not included in the above first candidate list of the above current block, and A video decoding method characterized in that, after an in-frame prediction mode other than a matrix-based position-dependent in-frame prediction mode of a plurality of adjacent blocks of the current block is assigned to the first candidate list, if the candidate mode slot of the first candidate list according to the in-frame prediction mode is not filled, a DIMD in-frame prediction mode derived based on the adjacent block or the template of the adjacent block is included in the first candidate list according to DIMD.

10. In Paragraph 9, If the number of prediction modes within the DIMD screen derived according to DIMD is greater than the number of empty candidate mode slots in the first candidate list, An image decoding method characterized by including prediction modes within a DIMD screen in order of smallest template cost until all empty candidate mode slots of the first candidate list are filled.

11. In Paragraph 7, When the in-screen prediction mode of an adjacent block of the above current block is a matrix-based position-dependent in-screen prediction mode, the in-screen prediction mode of the above adjacent block is included in the above first candidate list of the above current block, and A video decoding method characterized in that, according to DIMD, a prediction mode within the DIMD screen derived based on the adjacent block or the template of the adjacent block is included in the second candidate list.

12. In Paragraph 7, When the in-frame prediction mode of an adjacent block of the above current block is a matrix-based position-dependent in-frame prediction mode, according to DIMD, a DIMD in-frame prediction mode derived based on the adjacent block or a template of the above adjacent block is included in the first candidate list, and An image decoding method characterized in that the in-frame prediction mode of the adjacent block is included in the second candidate list of the current block.

13. In Paragraph 1, When a matrix-based position-dependent in-screen prediction mode is applied to the current block, the candidate list of the current block is configured to include only the matrix-based position-dependent in-screen prediction mode, and When the in-screen prediction mode of an adjacent block of the above current block is a matrix-based position-dependent in-screen prediction mode, the in-screen prediction mode of the above adjacent block is included in the candidate list of the above current block, and A video decoding method characterized in that when the in-frame prediction mode of an adjacent block of the current block is not a matrix-based position-dependent in-frame prediction mode, the in-frame prediction mode of the adjacent block is not included in the candidate list of the current block.

14. In Paragraph 13, When the in-screen prediction mode of the first adjacent block of the above current block is not a matrix-based position-dependent in-screen prediction mode, the in-screen prediction mode of the above first adjacent block is not included in the candidate list of the above current block, and A video decoding method characterized in that, when the in-frame prediction mode of a second adjacent block adjacent to the first adjacent block is a matrix-based position-dependent in-frame prediction mode, the in-frame prediction mode of the second adjacent block is included in the candidate list of the current block instead of the in-frame prediction mode of the first adjacent block.

15. A step of determining a candidate list for in-frame prediction of the current block based on whether the in-frame prediction mode of the adjacent block of the current block is a matrix-based position-dependent in-frame prediction mode; A step of encoding an in-screen prediction mode of the current block based on the candidate list of the current block; A video encoding method comprising the step of predicting the current block according to the in-frame prediction mode of the current block.

16. A bitstream transmission method for transmitting a bitstream generated by a video encoding method, A step of encoding an image based on the above image encoding method; and The method includes the step of transmitting a bitstream containing the encoded image, The above image encoding method is, A step of determining a candidate list for in-screen prediction of the current block based on whether the in-screen prediction mode of the adjacent block of the current block is a matrix-based position-dependent in-screen prediction mode; A step of encoding an in-screen prediction mode of the current block based on the candidate list of the current block; A transmission method characterized by including a step of predicting the current block according to an in-screen prediction mode of the current block.

Images