Image encoding / decoding method and apparatus, and recording medium on which bitstream is stored

Abstract

An image encoding / decoding method and apparatus, a recording medium on which a bitstream is stored, and a transmission method are provided. The image decoding method may comprise the steps of: acquiring block vector information from a bitstream; deriving a first block vector of the current block on the basis of the block vector information; selecting any one merge candidate from among merge candidates included in a merge candidate list; deriving a second block vector of the current block on the basis of the selected merge candidate; deriving a first prediction block on the basis of the first block vector, and deriving a second prediction block on the basis of the second block vector; and generating a final prediction block by performing weighted summation of the first prediction block and the second prediction block, wherein the step of selecting the merge candidate is performed on the basis of the similarity between the first prediction block and a reference block indicated by a block vector of a merge candidate included in the merge candidate list.

Description

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

[0001] The present disclosure relates to a video encoding / decoding method, a device, and a recording medium storing a bitstream. Specifically, the present disclosure relates to a video encoding / decoding method, a device, and a recording medium storing a bitstream based on an improved binary prediction intra-block copying method.

[0002] Recently, the demand for high-resolution, high-quality images, such as Ultra High Definition (UHD) images, is increasing across various application fields. Furthermore, interest in and demand for immersive media, such as Virtual Reality (VR) content, Artificial Reality (AR) content, and holograms, is also increasing. Furthermore, broadcasting of images with characteristics different from reality, such as game images, is also on the rise. As image data increases in resolution and quality, the relative amount of data increases compared to conventional image data. Therefore, transmitting image data using existing media such as wired and wireless broadband lines or storing it using existing storage media increases transmission and storage costs. To address these issues arising from the increasing resolution and quality of data, highly efficient image encoding / decoding technologies for higher-resolution and higher-quality images are required.

[0003] In video coding and decoding methods and devices, intra-block copy (IBC) is a technique for searching for a prediction block for the current coding unit (CU) block (current block) within an already reconstructed region. Intra-block copy prediction offers high prediction accuracy for screen content with repetitive similar shapes. In particular, when there is no reference picture and only intra prediction is applicable, applying intra-block copy prediction can improve encoding efficiency. Therefore, various tools for intra-block copy prediction are being discussed to improve encoding efficiency in cases where only intra prediction is applicable.

[0004] The present disclosure aims to provide a video encoding / decoding method and device 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] Additionally, the present disclosure aims to provide an improved binary prediction intra block copying method.

[0007] A video decoding method according to one embodiment of the present disclosure includes the steps of obtaining block vector information from a bitstream, deriving a first block vector of a current block based on the block vector information, selecting one of merge candidates included in a merge candidate list, deriving a second block vector of the current block based on the selected merge candidate, deriving a first prediction block based on the first block vector and deriving a second prediction block based on the second block vector, and generating a final prediction block of the current block by weighting the first prediction block and the second prediction block, wherein the step of selecting the merge candidate may be performed based on a similarity between a reference block indicated by a block vector of a merge candidate included in the merge candidate list and the first prediction block.

[0008] In the above image decoding method, the step of rearranging the merge candidate list may further be included, and the step of selecting the merge candidate may be performed based on the rearranged merge candidate list.

[0009] In the above image decoding method, the rearranging step may be performed based on the similarity between the template of the reference block indicated by the block vector of the merge candidate included in the merge candidate list and the current template of the current block.

[0010] In the above image decoding method, the second block vector can be derived by correcting the initial block vector of the selected merge candidate.

[0011] In the above image decoding method, the initial block vector can be corrected based on the similarity between a reference block included in a predetermined area of ​​the current picture and the first prediction block.

[0012] In the above image decoding method, the initial block vector is corrected based on the similarity between the current template of the current block and the candidate template, and the candidate template can be included in a predetermined area of ​​the current picture.

[0013] In the above image decoding method, the weight of the first prediction block and the weight of the second prediction block can be determined as preset values.

[0014] In the above image decoding method, the weight of the first prediction block and the weight of the second prediction block can be determined based on the distance between the current block and the first prediction block and the distance between the current block and the second prediction block.

[0015] In the above image decoding method, the weight of the first prediction block and the weight of the second prediction block can be determined based on the quantization coefficient of the first prediction block and the quantization coefficient of the second prediction block.

[0016] In the above image decoding method, the weight of the first prediction block and the weight of the second prediction block can be determined based on the prediction mode of the surrounding blocks of the current block.

[0017] In the above image decoding method, the surrounding block may include at least one of an adjacent block or a non-adjacent block of the current block.

[0018] In the above image decoding method, the weight of the first prediction block and the weight of the second prediction block may be determined based on at least one of the similarity between the template of the first prediction block and the current template of the current block or the similarity between the template of the second prediction block and the current template of the current block.

[0019] According to one embodiment of the present disclosure, a video encoding method includes the steps of determining block vector information, deriving a first block vector of a current block based on the block vector information, selecting one of merge candidates included in a merge candidate list, deriving a second block vector of the current block based on the selected merge candidate, deriving a first prediction block based on the first block vector and deriving a second prediction block based on the second block vector, and generating a final prediction block of the current block by weighting the first prediction block and the second prediction block, wherein the step of selecting the merge candidate may be performed based on a similarity between a reference block indicated by a block vector of a merge candidate included in the merge candidate list and the first prediction block.

[0020] A non-transitory computer-readable recording medium storing a bitstream generated by an image encoding method according to one embodiment of the present disclosure can store the bitstream generated by the image encoding method.

[0021] A bitstream transmission method according to one embodiment of the present disclosure can transmit a bitstream generated by the image encoding method.

[0022] 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.

[0023] According to the present disclosure, a video encoding / decoding method and device with improved encoding / decoding efficiency can be provided.

[0024] Additionally, according to the present disclosure, an improved binary prediction intra block copy method can be provided.

[0025] Additionally, according to the present disclosure, the amount of bits transmitted can be saved and coding efficiency can be improved.

[0026] Additionally, according to the present disclosure, prediction accuracy can be improved.

[0027] The effects that can be obtained from the present disclosure are not limited to the effects mentioned above, and other effects that are not mentioned will be clearly understood by a person having ordinary skill in the art to which the present disclosure pertains from the description below.

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

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

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

[0031] FIG. 4 is a diagram for explaining a binary prediction intra block copy method according to one embodiment of the present disclosure.

[0032] FIG. 5 is a diagram illustrating an improved IBC BVP-Merge method according to one embodiment of the present disclosure.

[0033] FIG. 6 is a drawing for explaining a merge block vector correction method according to one embodiment of the present disclosure.

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

[0035] FIG. 8 is a diagram exemplifying a 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 includes the steps of obtaining block vector information from a bitstream, deriving a first block vector of a current block based on the block vector information, selecting one of merge candidates included in a merge candidate list, deriving a second block vector of the current block based on the selected merge candidate, deriving a first prediction block based on the first block vector and deriving a second prediction block based on the second block vector, and generating a final prediction block of the current block by weighting the first prediction block and the second prediction block, wherein the step of selecting the merge candidate may be performed based on a similarity between a reference block indicated by a block vector of a merge candidate included in the merge candidate list and the first prediction block.

[0037] The present disclosure is susceptible to various modifications and embodiments. Therefore, 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, but rather to encompass all modifications, equivalents, and alternatives falling within the spirit and scope of the present disclosure. In the drawings, similar reference numerals designate the same or similar functions throughout. The shapes and sizes of elements in the drawings may be provided for illustrative purposes only for clarity. The detailed description of the exemplary embodiments described below refers to the accompanying drawings, which illustrate specific embodiments by way of example. These embodiments are described in sufficient detail to enable those skilled in the art to practice the embodiments. It should be understood that the various embodiments, while different from one another, are not necessarily 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. Furthermore, it should be understood that the positions or arrangements of individual components within each disclosed embodiment may be modified without departing from the spirit and scope of the embodiment. Accordingly, the detailed description set forth below is not intended to be taken in a limiting sense, and the scope of the exemplary embodiments, if properly described, is defined only by the appended claims, along with the full scope equivalents to which such claims are entitled.

[0038] While terms such as "first" and "second" may be used herein to describe various components, these components should not be limited by these terms. These terms are used solely to distinguish one component from another. For example, without departing from the scope of the present disclosure, a first component may be referred to as a "second component," and similarly, a second component may also be referred to as a "first component." The term "and / or" includes a combination of multiple related items described herein or any of multiple related items described herein.

[0039] The components shown in the embodiments of the present disclosure are independently depicted to represent different characteristic functions, and do not imply that each component is composed of separate hardware or a single software component. That is, each component is listed and included as a separate component for convenience of explanation, and at least two components among each component 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 separate embodiments of each component are also included in the scope of the present disclosure as long as they do not deviate from the essence of the present disclosure.

[0040] The terminology used in this disclosure is merely used to describe specific embodiments and is not intended to limit the present disclosure. The singular expression includes the plural expression unless the context clearly dictates otherwise. In addition, some components of the present disclosure may not be essential components that perform essential functions in the present disclosure and may be optional components merely for performance enhancement. The present disclosure may be implemented by including only components essential to implementing the essence of the present disclosure, excluding components used solely for performance enhancement, and a structure including only essential components, excluding optional components used solely for performance enhancement, is also within the scope of the present disclosure.

[0041] In an embodiment, the term "at least one" may mean one of a number greater than or equal to 1, such as 1, 2, 3, and 4. In an embodiment, the term "a plurality of" may mean one of a number greater than or equal to 2, 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 a detailed description of a related known configuration or function is judged to obscure the gist of this specification, the detailed description will be omitted. The same reference numerals will be used for identical components in the drawings, and duplicate descriptions of the same components will be omitted.

[0043] Glossary of Terms

[0044] Hereinafter, “video” may mean a single picture constituting a video, or may refer to the video itself. For example, “encoding and / or decoding of a video” may mean “encoding and / or decoding of a video,” or may mean “encoding and / or decoding of one of the videos constituting the video.”

[0045] Hereinafter, the terms "video" and "movie" may be used interchangeably and have the same meaning. Furthermore, the target image may be an encoding target image, which is the target of encoding, and / or a decoding target image, which is the target of decoding. Furthermore, the target image may be an input image input to an encoding device, or an input image input to a decoding device. Here, the target image may have the same meaning as the current image.

[0046] Hereinafter, the terms encoder and image encoding device may be used interchangeably and have the same meaning.

[0047] Hereinafter, the terms decoder and image decoding device may be used interchangeably and have the same meaning.

[0048] Hereinafter, “image”, “picture”, “frame” and “screen” may be used with the same meaning and may be used interchangeably.

[0049] Hereinafter, the term "target block" may refer to an encoding target block, which is the target of encoding, and / or a decoding target block, which is the target of decoding. Furthermore, the target block may refer to a current block, which is the target of current encoding and / or decoding. For example, the terms "target block" and "current block" may be used interchangeably and have the same meaning.

[0050] Hereinafter, "block" and "unit" may be used with the same meaning and may be used interchangeably. In addition, "unit" may mean including a luminance component block and a corresponding chroma component block to distinguish it from a block. For example, a coding tree unit (CTU) may be composed of one luma component (Y) coding tree block (CTB) and two chroma component (Cb, Cr) coding tree blocks associated with it.

[0051] Hereinafter, the terms “sample,” “pixel,” and “pixel” may be used interchangeably and have the same meaning. Here, a sample may represent a basic unit that constitutes a block.

[0052] Hereinafter, “inter” and “between screens” may be used interchangeably and have the same meaning.

[0053] Hereinafter, “intra” and “within screen” may be used interchangeably and have the same meaning.

[0054]

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

[0056] The encoding device (100) may be an encoder, a video encoding device, or an image encoding device. A 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 transformation unit (130), a quantization unit (140), an entropy encoding unit (150), an inverse quantization unit (160), an inverse transformation unit (170), an adder (117), a filter unit (180), and a reference picture buffer (190).

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

[0059] The video segmentation unit (110) can segment the input video into various forms to increase the efficiency of video encoding / decoding. That is, the input video is composed of multiple pictures, and one picture can be hierarchically segmented and processed for compression efficiency, parallel processing, etc. For example, one picture can be segmented into one or more tiles or slices, which can then be segmented into multiple Coding Tree Units (CTUs). Alternatively, one picture can first be segmented into multiple sub-pictures defined as groups of rectangular slices, and each sub-picture can then be segmented into the tiles / slices. Here, the sub-pictures can be utilized to support the function of partially independently encoding / decoding and transmitting the picture. Since multiple sub-pictures can each be individually restored, there is an advantage of easy editing in applications that configure multi-channel input into a single picture. In addition, tiles can be segmented horizontally to generate bricks. Here, a brick can be utilized as the basic unit of intra-picture parallel processing. In addition, one CTU can be recursively split into a quadtree (QT), and the terminal node of the split can be defined as a coding unit (CU). The CU can be split into a prediction unit (PU) and a transformation unit (TU), and prediction and splitting can be performed. Meanwhile, the CU can be utilized as a prediction unit and / or a transformation unit itself. Here, for flexible splitting, each CTU can be recursively split into a multi-type tree (MTT) as well as a quadtree (QT). Splitting of a CTU into a multi-type tree can start from the terminal node of a QT, and the MTT can be composed of a binary tree (BT) and a triple tree (TT).For example, the MTT structure can be divided into vertical binary split mode (SPLIT_BT_VER), horizontal binary split mode (SPLIT_BT_HOR), vertical ternary split mode (SPLIT_TT_VER), and horizontal ternary split mode (SPLIT_TT_HOR). In addition, the minimum block size (MinQTSize) of the quad tree of the luminance block during splitting can be set to 16x16, the maximum block size (MaxBtSize) of the binary tree can be set to 128x128, and the maximum block size (MaxTtSize) of the triple tree can be set to 64x64. In addition, 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 improve the encoding efficiency of the I slice, a dual tree can be applied that uses different CTU partition structures for luminance and chrominance components. On the other hand, in the P and B slices, the luminance and chrominance CTBs (Coding Tree Blocks) within the CTU can be partitioned into a single tree that shares the coding tree structure.

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

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

[0062] When the prediction mode is intra mode, the intra prediction unit (120) can use samples of blocks already encoded / decoded around the current block as reference samples. The intra prediction unit (120) can perform spatial prediction on the current block using the reference samples, and can generate prediction samples for the input block through spatial prediction. Here, intra prediction can mean prediction within the screen.

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

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

[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-screen prediction or motion compensation.

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

[0067] In addition, based on the above inter-screen 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 the GPM (Geometric Partitioning Mode) mode of PU based prediction can be applied. In addition, in order to improve the performance of each mode, the HMVP (History based MVP), the PAMVP (Pairwise Average MVP), the CIIP (Combined Intra / Inter Prediction), the AMVR (Adaptive Motion Vector Resolution), the BDOF (Bi-Directional Optical-Flow), the BCW (Bi-predictive with CU Weights), the LIC (Local Illumination Compensation), the TM (Template Matching), and the OBMC (Overlapped Block Motion Compensation) can be applied.

[0068] Among these, AFFINE mode is a technology that is used in both AMVP and MERGE modes and also has high encoding efficiency. In the existing video coding standard, since MC (Motion Compensation) is performed by considering only the parallel translation of the block, there was a disadvantage in that it could not properly compensate for motions that occur in reality, such as zoom in / out and rotation. To supplement 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 the affine motion model of one of the upper left, upper right, and lower left of the current block.

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

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

[0071] Quantized levels can be generated by applying quantization to transform coefficients or residual signals. In the following embodiments, quantized levels may also be referred to as transform coefficients.

[0072] For example, a 4x4 luminance residual block generated through intra prediction can be transformed using a basis vector based on DST (Discrete Sine Transform), and the remaining residual blocks can be transformed using a basis vector based on DCT (Discrete Cosine Transform). In addition, through RQT (Residual Quad Tree) technology, the transform block is divided into a quad tree shape for one block, and after performing transformation and quantization on each transform block divided through RQT, a coded block flag (cbf) can be transmitted to increase encoding efficiency when all coefficients become 0.

[0073] Another alternative is to apply Multiple Transform Selection (MTS) technology, which selectively performs transformation using multiple transformation bases. That is, instead of dividing CUs into TUs via RQT, a Sub-block Transform (SBT) technology can perform a function similar to TU division. Specifically, SBT is applied only to inter-screen prediction blocks, and unlike RQT, it can divide the current block into ½ or ¼ blocks vertically or horizontally, and then perform transformation on only one of the blocks. For example, in a vertically divided block, the transformation can be performed on the leftmost or rightmost block, and in a horizontally divided block, the transformation can be performed on the topmost or bottommost block.

[0074] Additionally, LFNST (Low Frequency Non-Separable Transform), a secondary transform technique that further transforms the residual signal converted to the frequency domain through DCT or DST, can be applied. LFNST additionally performs a transform on the low-frequency region of 4x4 or 8x8 in the upper left, which allows the residual coefficients to be concentrated in the upper left.

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

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

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

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

[0079] In this regard, when applying CABAC, the table probability update method can be changed to a simple formula-based table update method to reduce the size of the probability table stored in the decryption device. Furthermore, two different probability models can be used to obtain more accurate symbol probability values.

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

[0081] Coding parameters may include not only information (flags, indexes, etc.) encoded in an encoding device (100) and signaled to a decoding device (200), such as syntax elements, but also information derived during an encoding process or a decoding process, and may mean information necessary when encoding or decoding an image.

[0082] Here, signaling a flag or index may mean that the encoder entropy encodes the flag or index and includes it in the bitstream, and that the decoder entropy decodes the flag or index from the bitstream.

[0083] The encoded current image can be used as a reference image for other images to be processed later. Accordingly, the encoding device (100) can reconstruct or decode the encoded current image again and store the reconstructed 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 inversely transformed in the inverse transformation unit (170). The dequantized and / or inversely transformed coefficients can be combined with a prediction block through an adder (117), and a reconstructed block can be generated by combining the dequantized and / or inversely transformed coefficients and the prediction block. Here, the dequantized and / or inversely transformed coefficients refer to coefficients on which at least one of dequantization and inverse transformation has been performed, and may refer to a reconstructed residual block. The dequantization unit (160) and the inverse transformation unit (170) can be performed in the reverse process of the quantization unit (140) and the transformation unit (130).

[0085] The restoration block may pass through a filter unit (180). The filter unit (180) may apply a deblocking filter, a sample adaptive offset (SAO), an adaptive loop filter (ALF), a bilateral filter (BIF), a Luma Mapping with Chroma Scaling (LMCS), etc. as a filtering technique, in whole or in part, to the restoration sample, restoration block, or restoration image. The filter unit (180) may also be referred to as an in-loop filter. In this case, the in-loop filter is also used as a name excluding LMCS.

[0086] A deblocking filter can remove block distortion that occurs at the boundaries between blocks. Whether to apply a deblocking filter to the current block can be determined based on the samples contained in several 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 strength.

[0087] Sample adaptive offset can be used to compensate for encoding errors by adding an appropriate offset value to sample values. Sample adaptive offset can compensate for the offset from the original image on a sample-by-sample basis for deblocked images. This can be done by dividing the samples contained in the image into a fixed number of regions, determining the regions to be offset, and applying the offset to those regions. Alternatively, the offset can be applied by considering the edge information of each sample.

[0088] Bilateral filter (BIF) can also compensate for 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 between a reconstructed image and the original image. By dividing the samples contained in the image into predetermined groups and determining the filter to be applied to each group, filtering can be performed differentially for each group. Information regarding whether to apply an adaptive loop filter can be signaled for each coding unit (CU), and the shape and filter coefficients of the adaptive loop filter applied to each block can vary.

[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 chrominance components according to the average luminance value of the prediction signal. In particular, LMCS can be utilized as an HDR correction technique that reflects the characteristics of HDR (High Dynamic Range) images.

[0091] The restored block or restored image that has passed through the filter unit (180) may be stored in the reference picture buffer (190). The restored block that has passed through the filter unit (180) may be a part of the reference image. In other words, the reference image may be a restored image composed of restored blocks that have passed through the filter unit (180). The stored reference image may be used for inter-screen prediction or motion compensation thereafter.

[0092] FIG. 2 is a block diagram showing a configuration according to one embodiment of a decryption 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 streamed through a wired / wireless transmission medium. The decoding device (200) can perform decoding on the bitstream in intra mode or inter mode. In addition, 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 decryption is intra mode, the switch (203) can be switched to intra. If the prediction mode used for decryption 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 a current block.

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

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

[0100] The quantized level can be inversely quantized in the inverse quantization 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 inverse quantization and / or inverse transformation. At this time, the inverse quantization unit (220) can apply a quantization matrix to the quantized level. The inverse quantization unit (220) and inverse transformation unit (230) applied to the decoding device can apply the same technology as the inverse quantization unit (160) and inverse transformation unit (170) applied to the encoding device described above.

[0101] When intra mode is used, the intra prediction unit (240) can generate a predicted block by performing spatial prediction on the current block using sample values ​​of already decoded blocks surrounding 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 encoding device described above.

[0102] When the inter mode is used, the motion compensation unit (250) can generate a prediction block by performing motion compensation using a motion vector and a reference image stored in the reference picture buffer (270) on the current block. 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. In order to perform motion compensation, it is possible to determine whether the motion compensation method of the prediction unit included in the corresponding encoding unit is 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 decoding device can apply the same technology as the motion compensation unit (122) applied to the encoding device described above.

[0103] The adder (201) can add the restored residual block and the predicted block to generate a restored block. The filter unit (260) can apply at least one of an Inverse-LMCS, a deblocking filter, a sample adaptive offset, and an adaptive loop filter to the restored block or restored image. The filter unit (260) applied to the decoding device can apply the same filtering technology as that applied to the filter unit (180) applied to the encoding device described above.

[0104] The filter unit (260) can output a restored image. The restored block or restored image can be stored in the reference picture buffer (270) and used for inter prediction. The restored block that has passed through the filter unit (260) can be a part of the reference image. In other words, the reference image can be a restored image composed of restored blocks that have passed through the filter unit (260). The stored reference image can be used for inter-screen prediction or motion compensation thereafter.

[0105] FIG. 3 is a diagram schematically 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) in the form of a file or streaming through a digital storage medium or a network.

[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 reception unit (21), a decoding unit (22), and a rendering unit (23). The encoding unit (12) may be referred to as a video / image encoding unit, and the decoding unit (22) may be referred to as a video / image decoding unit. The transmission unit (13) may be included in the encoding unit (12). The reception 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 configured as a separate device or an external component.

[0108] The video source generation unit (11) can obtain video / images through a process of capturing, synthesizing, or generating video / images. The video source generation unit (11) can include a video / image capture device and / or a video / image generation device. The video / image capture device can include, for example, one or more cameras, a video / image archive including previously captured video / images, etc. The video / image generation device can include, for example, a computer, a tablet, a smartphone, etc., and can (electronically) generate video / images. For example, a virtual video / image can be generated through a computer, etc., in which case the video / image capture process can be replaced with 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, transformation, and quantization for compression and encoding efficiency. The encoding unit (12) can output 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 manner 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 reception unit (21) of the decoding device (20) via a digital storage medium or a network in the form of a file or streaming. The digital storage medium can include various storage media such as USB, SD, CD, DVD, Blu-ray, HDD, SSD, etc. The transmission unit (13) can include an element for generating a media file through a predetermined file format and can include an element for transmission via a broadcasting / communication network. The reception 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 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 in the same manner as the decoding device (200) of FIG. 2 described above.

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

[0113]

[0114] Uni-predictive IBC is a method for generating prediction values ​​based on a single block vector. In contrast, bi-predictive IBC, according to an embodiment of the present disclosure, derives two prediction values ​​based on two block vectors, respectively, and then derives a final prediction value based on these prediction values. Here, the two prediction values ​​can be derived in various ways.

[0115] Hereinafter, with reference to FIGS. 4 to 6, a binary prediction intra block copy method according to an embodiment of the present disclosure will be described.

[0116]

[0117] FIG. 4 is a diagram for explaining a binary prediction intra block copy method according to one embodiment of the present disclosure. Specifically, FIG. 4 is a diagram for explaining a block vector prediction-merge method (hereinafter, referred to as the IBC BVP-Merge method) among the binary prediction intra block copy methods.

[0118] The IBC BVP-Merge method is a combination of the block vector prediction (BVP) mode and the merge mode, and may refer to a method of generating a prediction value based on a block vector according to the BVP mode, generating a prediction value based on a block vector according to the merge mode, and generating a final prediction value based on the prediction values.

[0119] Meanwhile, the block vector according to the merge mode refers to a block vector derived based on the merge candidate list. At this time, the merge candidate list is a list that stores block vector information of the reference block of the current block, and can be referred to as an intra-block copy merge candidate list.

[0120] Referring to FIG. 4, the first matching block (Matching block1, 411) most similar to the current block (401) can be searched within a predefined search range (R1, R2, R3, R4) of a reconstructed area (402) of a current picture (400) of a current block (401).

[0121] And the block vector indicating the first matching block (411) can be referred to as the first block vector (BV1, 410). Here, the first block vector is a block vector according to the BVP mode.

[0122] Therefore, when the IBC BVP-Merge method is applied to the current block (401), the encoder can transmit motion information according to the BVP mode. Meanwhile, the motion information according to the BVP mode can include information regarding an intra block copy-based prediction method and information related to the first block vector (410). In the decoder, the first block vector (410) can be derived based on the motion information according to the BVP mode, and the first matching block (411) can be derived based on the block vector (410). Here, the first matching block can be referred to as a matching block according to the BVP mode.

[0123] And, the first prediction block of the current block (401) can be derived based on the first matching block (411). Here, the first prediction block can be referred to as a prediction block according to the BVP mode. For example, the first prediction block can be derived from the first matching block.

[0124] And, based on the second block vector (BV2, 420), the second matching block 2, 421) can be searched. Here, the second block vector (420) may be a block vector of a merge candidate selected from among the merge candidates included in the merge candidate list.

[0125] When the IBC BVP-Merge method is applied to the current block (401), the encoder can transmit motion information according to the merge mode to the decoder. The decoder can select a merge candidate from among the merge candidates included in the merge candidate list based on the merge candidate index information, and can derive a matching block based on the block vector of the selected merge candidate. Here, the derived matching block can be referred to as a matching block according to the merge mode.

[0126] Meanwhile, movement information according to merge mode may include merge candidate index information, etc.

[0127] In addition, the second prediction block of the current block can be derived based on the second matching block (421). For example, the second prediction block of the current block can be derived from the second matching block. Here, the second prediction block can be referred to as a prediction block according to the merge mode.

[0128] And, the final prediction block of the current block (401) can be generated based on the first prediction block and the second prediction block. For example, a final prediction block having an average value of the values ​​of the first prediction block and the values ​​of the second prediction block can be generated.

[0129] Therefore, in the IBC BVP-Merge method, motion information according to the BVP mode and motion information according to the merge mode can be signaled in the encoder / decoder. Here, in the encoder, motion information according to the BVP mode and motion information according to the merge mode can be determined, and in the decoder, a block vector based on the motion information according to the BVP mode can be derived, and a matching block according to the BVP mode can be derived based on the block vector. Then, a merge candidate based on the motion information according to the merge mode can be derived, and a matching block according to the merge mode can be derived based on the candidate. Then, a prediction signal of the current block can be generated based on the matching blocks.

[0130]

[0131] Hereinafter, an improved IBC BVP-Merge method according to one embodiment of the present disclosure will be described with reference to FIGS. 5 and 6.

[0132] FIG. 5 is a diagram illustrating an improved IBC BVP-Merge method according to one embodiment of the present disclosure. In the improved IBC-Merge method, motion information according to BVP mode is signaled in the encoder / decoder, but motion information according to merge mode may not be signaled. This can save signaled bits and improve coding efficiency.

[0133] Referring to FIG. 5, a first matching block (Matching block1, 511) most similar to the current block (501) can be searched within a predefined search range (R1, R2, R3, R4) of a reconstructed area (502) of a current picture (500) of a current block (501). In addition, a block vector indicating the first matching block (511) can be referred to as a first block vector (BV1, 510).

[0134] In the improved IBC BVP-Merge method, when the encoder transmits motion information according to the BVP mode, the decoder can derive a block vector (510) based on the motion information according to the BVP mode, and a first matching block (511) according to the BVP mode can be derived based on the block vector (510).

[0135] Meanwhile, motion information according to BVP mode may include information about block vectors, etc.

[0136] And, the first prediction block according to the BVP mode of the current block (501) can be derived based on the first matching block (511). For example, the first prediction block can be derived from the first matching block.

[0137] Then, a merge candidate can be selected from the merge candidate list. Then, a second matching block can be derived based on the block vector of the merge candidate. Here, the second matching block can be referred to as a matching block according to the merge mode.

[0138] Meanwhile, according to one embodiment, a merge candidate may be selected from a merge candidate list using a bilateral matching (BM) method. Here, the BM method may refer to a method of selecting a reference block most similar to a matching block according to the BVP mode as a matching block according to the merge mode. In this case, a merge candidate that indicates the corresponding reference block using a block vector may be selected as the optimal merge candidate from the merge candidate list.

[0139] Specifically, in the BM method, among the reference blocks indicated by the block vector of each merge candidate in the merge candidate list, the reference block most similar to the matching block according to the BVP mode can be selected. Here, the most similar may mean that the distortion with respect to the matching block according to the BVP mode is the smallest. At this time, the distortion measurement method may be any one of the distortion measurement methods such as the sum of absolute difference (SAD) measurement method, the sum of square error (SSE) measurement method, the sum of squared differences (SSD) measurement method, the mean-removal SAD (MRSAD) measurement method, and the sum of absolute transformed differences (SATD) measurement method.

[0140] Meanwhile, the reference blocks and candidate blocks indicated by the block vectors of each merge candidate may have the same meaning, and the selected reference block and the final matching block may have the same meaning.

[0141] Referring to Fig. 5, candidate block 1 (Candidate block1, 520), candidate block 2 (Candidate block2, 521), and candidate block 3 (Candidate block3, 522) are reference blocks indicated by the block vectors of each merge candidate in the merge candidate list. Therefore, Fig. 5 assumes a case where there are three merge candidates in the merge candidate list.

[0142] Meanwhile, for each candidate block, the distortion relative to the first matching block (511), which is a matching block according to the BVP mode, can be measured. Then, among the candidate blocks, the candidate block with the smallest distortion relative to the first matching block (511) can be determined as the matching block according to the merge mode. Furthermore, among the candidate blocks, the candidate block with the smallest distortion relative to the first prediction block can be determined as the matching block according to the merge mode.

[0143] Additionally, the second prediction block according to the merge mode of the current block can be derived based on the second matching block. For example, the second prediction block of the current block can be derived from the second matching block.

[0144] In addition, the final prediction block of the current block (501) can be generated based on the first prediction block and the second prediction block. For example, a final prediction block having an average value of the values ​​of the first prediction block and the second prediction block can be generated. In another example, the final prediction block of the current block can be generated by weighting the first prediction block and the second prediction block.

[0145]

[0146] According to another embodiment of the present disclosure, the merge candidate list may be reordered, and a merge candidate may be selected based on the reordered merge candidate list.

[0147] Specifically, the merge candidates in the merge candidate list can be reordered from highest priority to lowest, and a merge candidate can be selected based on the reordered merge candidate list. In this case, a higher priority can mean matching a lower index in the merge candidate list.

[0148] Meanwhile, the merge candidates in the merge candidate list can be rearranged so that the smaller the cost value, the higher the priority.

[0149] Meanwhile, the cost value can be calculated using a predefined cost function. Furthermore, the cost value calculation method can be any one of the SAD method, the SSE method, the SSD method, the MR-SAD method, and the SATD method.

[0150] Alternatively, the method for reordering merge candidates in the merge candidate list may be an adaptive reordering of merge candidates with template matching (ARMC-TM). The adaptive reordering of merge candidates with template matching may refer to a method for reordering merge candidates in the merge candidate list based on the similarity between the template of the reference block indicated by the block vector of each merge candidate and the template of the current block.

[0151] For example, merge candidates can be reordered so that a merge candidate corresponding to a template of a reference block with a high degree of similarity to the template of the current block has a high priority in the merge candidate list. In this case, a high degree of similarity may indicate a small distortion between the template of the current block and the template of the reference block indicated by the block vector of the merge candidate. Meanwhile, the distortion measurement method may be any one of the distortion measurement methods, such as the SAD measurement method, the SSD measurement method, the SSE measurement method, the MRSA measurement method, and the SATD measurement method.

[0152] Meanwhile, when the merge candidate list is reordered, N merge candidates with high priorities can be selected from the merge candidate list. Any one of the N merge candidates can be selected. Here, N is an arbitrary positive integer less than or equal to the total number of merge candidates included in the reordered merge candidate list.

[0153] For example, if N is 1, the merge candidate with the highest priority in the merge candidate list can always be selected.

[0154] Meanwhile, N can be determined by a convention in the encoder / decoder, or can be explicitly signaled at a higher or lower level in the encoder / decoder.

[0155] Then, a matching block according to the merge mode can be derived based on the block vector of the selected merge candidate. Then, a prediction block according to the merge mode can be generated based on the matching block.

[0156]

[0157] According to one embodiment of the present disclosure, in an improved IBC BVP-merge method, a block vector according to a merge mode can be corrected.

[0158] In the improved IBC-Merge method, motion information according to BVP mode is signaled at the encoder / decoder, but motion information according to merge mode may not be signaled. Therefore, block vector correction according to merge mode can improve prediction accuracy and enhance coding efficiency.

[0159] Meanwhile, the block vector before correction can be called the initial block vector, and the block vector after correction can be called the final block vector.

[0160] For example, starting from the position indicated by the initial block vector, a search for a reference block most similar to the matching block according to the BVP mode can be performed. Here, similarity may mean having the least distortion. At this time, the distortion measurement method may be any one of the SAD measurement method, the SSE measurement method, the SSD measurement method, the MRSAD measurement method, and the SATD measurement method.

[0161] And, the initial block vector can be corrected so that the block vector representing the searched reference block becomes a block vector according to the merge mode.

[0162] In addition, a matching block according to the merge mode can be derived as a matching block indicated by a corrected block vector. In addition, a prediction block according to the merge mode can be generated based on the matching block according to the merge mode.

[0163] Meanwhile, the search range can be set to a value preset in the encoder / decoder.

[0164] Meanwhile, the search may be performed based on the position indicated by the block vector of any one of the merge candidates included in the merge candidate list, rather than the position indicated by the initial block vector.

[0165]

[0166] FIG. 6 is a diagram for explaining a merge block vector correction method according to one embodiment of the present disclosure. Specifically, FIG. 6 is a diagram for explaining a merge block vector correction method using template matching (TM).

[0167] Specifically, template matching is performed to search for a reference template most similar to the current template of the current block in the current picture, and to derive a matching block based on the searched reference template, and an initial block vector may be corrected to point to the matching block.

[0168] In Fig. 6, the first matching block (Matching block1, 621) is a matching block according to the BVP mode, and the block vector (BV1, 620) indicates the corresponding matching block.

[0169] In Fig. 6, the neighboring areas (i.e., the left, top, and upper-left areas) of the current block (601) can be defined as the current template (603). The size of the template can be expressed as (w x L2) + (L1 xh) + (L1 x L2). Here, w and h represent the width and height of the block, and the values ​​of L1 and L2 can be any positive integers.

[0170] First, a merge candidate can be selected from among the candidates included in the merge candidate list.

[0171] And, the template most similar to the current template can be searched in the current picture.

[0172] Specifically, for matching blocks included within a predetermined search range, the similarity between the template of each matching block and the current template can be compared to search for a template most similar to the current template.

[0173] Here, the template of each matching block may mean the neighboring region (i.e., the left, top, and upper-left region) of the matching block.

[0174] Referring to Fig. 6, the reference template (611), which is a neighboring region of the second matching block (Matching block2, 610), refers to the template most similar to the current template within a given search range. Accordingly, the block corresponding to the current block (601) of the searched reference template (611) can be derived as the second matching block (610) according to the merge mode.

[0175] Meanwhile, "most similar" may mean the least distortion compared to the current template. Various methods can be used to measure distortion, including the SAD measurement method, the SSE measurement method, the SSD measurement method, the MRSAD measurement method, and the SATD measurement method.

[0176] And, the block vector of the selected merge candidate can be corrected to become a block vector (BV2, 612) representing the second matching block (610). Here, the second block vector (612) is the final block vector according to the correction.

[0177] And, based on the final block vector, a matching block according to the merge mode can be derived.

[0178] Meanwhile, information regarding the size and shape of the current template can be determined by the encoder and transmitted to the decoder. Furthermore, the size and shape of the current template can be set to preset values ​​in the encoder / decoder.

[0179] With respect to the template shape, in the example of FIG. 6, one template is used to search for a reference template most similar to the current template, but this can also be done using, for example, an L-shaped template, a template using only the top region, a template using only the left region, or a template of any shape to search for a reference template most similar to the current template.

[0180] Meanwhile, in FIG. 6, the template (603, 611) is a set of pixels adjacent to the current block (601) or the neighboring area of ​​the matching block (610), or, as an example, a set of pixels not adjacent to the block can also be a template.

[0181]

[0182] Below, we describe how to generate the final prediction block of the current block in the improved IBC BVP-Merge method.

[0183] The existing IBC BVP-Merge method can generate a prediction block of the current block by averaging the prediction block according to the BVP mode and the prediction block according to the merge mode.

[0184] In the improved IBC BVP-Merge method, a prediction block for the current block can be generated by weighting the predicted block according to BVP mode and the predicted block according to merge mode. This can improve prediction accuracy.

[0185] Meanwhile, the prediction block of the current block generated by weighting the prediction block according to the BVP mode and the prediction block according to the merge mode can be called the final prediction block.

[0186] Meanwhile, weighted sum can be performed by applying a first weight value and a second weight value to a prediction block according to the BVP mode and a prediction block according to the merge mode, respectively.

[0187] Meanwhile, in this specification, the weight value of the prediction block according to the BVP mode and the weight value of the prediction block according to the merge mode can be referred to as the weight value according to the IBC BVP-Merge method.

[0188] Meanwhile, the prediction block of the current block can be generated as in mathematical expression 1.

[0189]

[0190]

[0191] In mathematical expression 1, P denotes a prediction block of the current block. In addition, P1 denotes a prediction block according to BVP mode, and P2 denotes a prediction block according to merge mode.

[0192] In addition, in mathematical expression 1, W1 and W2 represent the weight values ​​of the prediction block according to the BVP mode and the weight values ​​of the prediction block according to the merge mode, respectively. Here, W1 and W2 are each real numbers greater than or equal to 0, and the sum of W1 and W2 is 1.

[0193] In one embodiment, the weight values ​​W1 and W2 may be determined based on arbitrary values ​​agreed upon by the encoder / decoder. In this case, W1 and W2 may not be signaled separately. Here, the sum of the weight values ​​W1 and W2 is 1, and each of the weight values ​​W1 and W2 is a real number greater than or equal to 0.

[0194] Meanwhile, the weight value (W1) of the prediction block according to the BVP mode may be greater than the weight value (W2) of the prediction block according to the merge mode. This is because the prediction accuracy of the prediction block according to the BVP mode is high.

[0195] In another embodiment, the weight values ​​according to the IBC BVP-MERGE method may be determined based on the distance between the current block and the matching block. For example, the first weight value and the second weight value may be calculated as in Equation 2.

[0196]

[0197]

[0198] In mathematical expression 2, W1 and W2 represent the weight values ​​of the prediction block according to the BVP mode and the weight values ​​of the prediction block according to the merge mode, respectively.

[0199] Additionally, in Equation 2, D1 represents the distance between the current block and the matching block according to the BVP mode. And D2 represents the distance between the current block and the matching block according to the merge mode.

[0200] According to Equation 2, W1 is proportional to D2, and W2 is proportional to D1. Therefore, if D1 and D2 are identical, the final prediction block is generated as the average value of the prediction block according to the BVP mode and the prediction block according to the merge mode. In addition, if D1 and D2 are different, a larger weight value may be assigned to a prediction block based on a matching block that is closer to the current block, and a smaller weight value may be assigned to a prediction block based on a matching block that is further away.

[0201] Meanwhile, the distance between the current block and the matching block or the distance between the current block and the predicted block can be calculated as in mathematical expressions 3 to 5.

[0202]

[0203]

[0204]

[0205]

[0206] In mathematical expressions 3 to 5, the reference position of the current block is (x c, y c ) can be said to be the reference position of the matching block (x m, y m ) can be said to be 1 or 2. i can be 1 or 2.

[0207] When i is 1 (D1), the distance between the current block and the matching block according to the BVP mode is calculated. Here, (x m, y m) corresponds to the reference position of the matching block according to the BVP mode.

[0208] When i is 2 (D2), the distance between the current block and the matching block according to the merge mode is calculated. Here, (x m, y m ) corresponds to the reference position of the matching block according to the merge mode.

[0209] Meanwhile, the reference positions of the current block and the matching block can be predefined in the encoder / decoder as the top-left coordinates, center coordinates, etc. of the corresponding block.

[0210] In another embodiment, the weighting value according to the IBC BVP-Merge method may be determined based on the quantization parameter (QP) of the matching block or prediction block. For example, a higher weighting value may be assigned to a prediction block with a lower quantization parameter. In another example, an arbitrary weighting value based on the quantization parameter may be determined by a contract between the encoder and decoder.

[0211] According to another embodiment, if the prediction mode of a neighboring block of the current block is the IBC BVP-Merge mode, the weight value according to the IBC BVP-Merge method may be inherited based on information of the neighboring block. That is, the weight value may be determined to be the same as the weight value of the neighboring block. Meanwhile, the neighboring block may include adjacent blocks and non-adjacent blocks of the current block.

[0212]

[0213] According to another embodiment, if there are multiple neighboring blocks with the IBC BVP-Merge mode as the prediction mode for the current block, the weight value according to the IBC BVP-Merge method may be inherited by information of a neighboring block with a higher priority among the neighboring blocks. That is, the weight value according to the IBC BVP-Merge method may be determined to be the same as the weight value of the neighboring block with a higher priority among the neighboring blocks. Meanwhile, the neighboring blocks may include adjacent blocks and non-adjacent blocks of the current block.

[0214] According to another embodiment, if there are multiple neighboring blocks with the prediction mode set to IBC BVP-Merge mode for the current block, the weight value according to the IBC BVP-Merge method may be determined based on information of the neighboring blocks. For example, the weight value according to the IBC BVP-Merge method may be calculated as the average of the weight values ​​of the neighboring blocks. Meanwhile, the neighboring blocks may include adjacent blocks and non-adjacent blocks of the current block.

[0215] According to another embodiment, the weight value according to the IBC BVP-Merge method can be determined based on information of surrounding blocks.

[0216] For example, if there are more neighboring blocks whose prediction mode is IBC-BVP mode than neighboring blocks whose prediction mode is IBC-Merge mode, the weight value of the prediction block according to the BVP mode may be determined to be greater than the weight value of the prediction block according to the merge mode. Conversely, if there are more neighboring blocks whose prediction mode is IBC-Merge mode than neighboring blocks whose prediction mode is IBC-BVP mode, the weight value of the prediction block according to the merge mode may be determined to be greater than the weight value of the prediction block according to the BVP mode.

[0217] As another example, if the number of neighboring blocks whose prediction mode is IBC-BVP mode is greater than a predetermined threshold, the weight value of the prediction block according to BVP mode may be determined to be greater than the weight value of the prediction block according to merge mode. Conversely, if the number of neighboring blocks whose prediction mode is IBC-MERGE mode is greater than a predetermined threshold, the weight value of the prediction block according to merge mode may be determined to be greater than the weight value of the prediction block according to BVP mode.

[0218] As another example, a weight value according to the IBC BVP-Merge method can be determined based on the occurrence frequency of a neighboring block whose prediction mode is IBC-BVP mode and a neighboring block whose prediction mode is IBC-MERGE mode in the neighboring block.

[0219] According to another embodiment, the weight values ​​according to the IBC BVP-Merge method may be determined based on the distortion between templates. For example, the first weight value and the second weight value may be calculated as in Equation 6.

[0220]

[0221]

[0222] In Equation 6, Cost1 may represent the distortion between the template of the current block and the template of the matching block according to the BVP mode. And Cost2 may represent the distortion between the template of the current block and the template of the matching block according to the merge mode.

[0223] Meanwhile, the distortion measurement method may be any one of the SAD measurement method, the SSE measurement method, the SSD measurement method, the MRSAD measurement method, and the SATD measurement method.

[0224] Meanwhile, information regarding the size and shape of the template can be determined by the encoder and transmitted to the decoder. Furthermore, the size and shape of the template can be set to preset values ​​in the encoder / decoder.

[0225]

[0226] FIG. 7 is a flowchart illustrating a decryption method according to one embodiment of the present disclosure. The decryption method of FIG. 7 can be performed by an image decryption device.

[0227] The video decoding device can obtain block vector information from a bitstream (S700).

[0228] The image decoding device can derive a first block vector of the current block based on the block vector information (S710).

[0229] And, the video decoding device can select any one of the merge candidates included in the merge candidate list (S720).

[0230] The step of selecting the above merge candidate may be performed based on the similarity between the reference block indicated by the block vector of the merge candidate included in the merge candidate list and the first prediction block.

[0231] Meanwhile, the step of rearranging the merge candidate list may be further included, and the step of selecting the merge candidate may be performed based on the rearranged merge candidate list.

[0232] Meanwhile, the reordering step may be performed based on the similarity between the template of the reference block indicated by the block vector of the merge candidate included in the merge candidate list and the current template of the current block.

[0233] And, the image decoding device can derive a second block vector of the current block based on the selected merge candidate (S730).

[0234] Meanwhile, the second block vector can be derived by correcting the initial block vector of the selected merge candidate.

[0235] Meanwhile, the initial block vector can be corrected based on the similarity between the reference block included in a predetermined area of ​​the current picture and the first prediction block.

[0236] Meanwhile, the initial block vector is corrected based on the similarity between the current template of the current block and the candidate template, and the candidate template can be included in a predetermined area of ​​the current picture.

[0237] And, the image decoding device can derive a first prediction block based on the first block vector and derive a second prediction block based on the second block vector (S740).

[0238] And, the image decoding device can generate a final prediction block of the current block by weighting the first prediction block and the second prediction block (S750).

[0239] Meanwhile, the weight of the first prediction block and the weight of the second prediction block can be determined as preset values.

[0240] Meanwhile, the weight of the first prediction block and the weight of the second prediction block can be determined based on the distance between the current block and the first prediction block and the distance between the current block and the second prediction block.

[0241] Meanwhile, the weight of the first prediction block and the weight of the second prediction block can be determined based on the quantization coefficient of the first prediction block and the quantization coefficient of the second prediction block.

[0242] Meanwhile, the weight of the first prediction block and the weight of the second prediction block can be determined based on the prediction mode of the surrounding blocks of the current block.

[0243] Meanwhile, the surrounding block may include at least one of an adjacent block or a non-adjacent block of the current block.

[0244] Meanwhile, the weight of the first prediction block and the weight of the second prediction block may be determined based on at least one of the similarity between the template of the first prediction block and the current template of the current block or the similarity between the template of the second prediction block and the current template of the current block.

[0245] Meanwhile, the steps described in FIG. 7 can be performed in the same manner in an image encoding method. Furthermore, a bitstream can be generated by an image encoding method including the steps described in FIG. 7. The bitstream can be stored on a non-transitory computer-readable recording medium and can also be transmitted (or streamed).

[0246]

[0247] FIG. 8 is a diagram exemplifying a content streaming system to which an embodiment according to the present disclosure can be applied.

[0248] 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.

[0249] The encoding server compresses content input from multimedia input devices such as smartphones, cameras, and CCTVs into digital data, generates a bitstream, and transmits it to the streaming server. Alternatively, if multimedia input devices such as smartphones, cameras, and CCTVs directly generate bitstreams, the encoding server may be omitted.

[0250] The above bitstream can be generated by an image encoding method and / or an image encoding device to which an embodiment of the present disclosure is applied, and the streaming server can temporarily store the bitstream during the process of transmitting or receiving the bitstream.

[0251] The streaming server transmits multimedia data to a user device based on a user request via a web server, and the web server can act as an intermediary to inform the user of available services. When a user requests a desired service from the web server, the web server transmits the request 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 may play a role in controlling commands / responses between each device within the content streaming system.

[0252] The streaming server can receive content from a media repository and / or 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 smooth streaming service, the streaming server can store the bitstream for a certain period of time.

[0253] Examples of the user devices may include mobile phones, smart phones, laptop computers, digital broadcasting terminals, personal digital assistants (PDAs), portable multimedia players (PMPs), navigation devices, slate PCs, tablet PCs, ultrabooks, wearable devices (e.g., smartwatches, smart glasses, HMDs), digital TVs, desktop computers, digital signage, etc.

[0254] Each server within the above content streaming system can be operated as a distributed server, in which case data received from each server can be processed in a distributed manner.

[0255]

[0256] The above embodiments can be performed in the same or corresponding manner in an encoding device and a decoding device. In addition, an image can be encoded / decoded using at least one or a combination of at least one of the above embodiments.

[0257] The order in which the above embodiments are applied may be different in the encoding device and the decoding device. Alternatively, the order in which the above embodiments are applied may be the same in the encoding device and the decoding device.

[0258] The above embodiments can be performed for each of the luminance and chrominance signals. Alternatively, the above embodiments can be performed identically for the luminance and chrominance signals.

[0259] In the above embodiments, the methods are described based on a flowchart as a series of steps or units. However, the present disclosure is not limited to the order of the steps, and some steps may occur in a different order or simultaneously with other steps described above. Furthermore, those skilled in the art will understand that the steps depicted in the flowchart are not exclusive, and that other steps may be included, or one or more steps in the flowchart may be deleted without affecting the scope of the present disclosure.

[0260] The above embodiments may be implemented in the form of program commands that can be executed by various computer components and recorded on a computer-readable recording medium. The computer-readable recording medium may include program commands, data files, data structures, etc., either singly or in combination. The program commands recorded on the computer-readable recording medium may be those specifically designed and configured for the present disclosure, or may be known and usable by those skilled in the art of computer software.

[0261] The bitstream generated by the encoding method according to the above embodiment can be stored in a non-transitory computer-readable recording medium. In addition, the bitstream stored in the non-transitory computer-readable recording medium can be decoded by the decoding method according to the above embodiment.

[0262] Here, 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 ROMs, RAMs, and flash memories. Examples of program instructions include not only machine language codes such as those generated by a compiler, but also high-level language codes that can be executed by a computer using an interpreter or the like. 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.

[0263] Although the present disclosure has been described above with specific details such as specific components and limited examples and drawings, these are provided only to help a more general understanding of the present disclosure, and the present disclosure is not limited to the above examples, and a person having ordinary knowledge in the technical field to which the present disclosure belongs can make various modifications and variations from this description.

[0264] Therefore, the spirit of the present disclosure should not be limited to the embodiments described above, and all modifications that are equivalent or equivalent to the following claims as well as the claims are considered to fall within the scope of the spirit of the present disclosure.

[0265] The present invention can be used in a device for encoding / decoding an image and a recording medium storing a bitstream.

Claims

1. A step of obtaining block vector information from a bitstream; A step of deriving a first block vector of a current block based on the above block vector information; A step of selecting one of the merge candidates included in the merge candidate list; A step of deriving a second block vector of the current block based on the selected merge candidate; A step of deriving a first prediction block based on the first block vector and deriving a second prediction block based on the second block vector; and A step of generating a final prediction block of the current block by weighting the first prediction block and the second prediction block, A video decoding method, characterized in that the step of selecting the merge candidate is performed based on the similarity between the reference block indicated by the block vector of the merge candidate included in the merge candidate list and the first prediction block.

2. In paragraph 1, Further comprising a step of reordering the above merge candidate list, A method for decoding an image, characterized in that the step of selecting the merge candidate is performed based on the rearranged merge candidate list.

3. In paragraph 2, A video decoding method, characterized in that the above-mentioned rearranging step is performed based on the similarity between the template of the reference block indicated by the block vector of the merge candidate included in the merge candidate list and the current template of the current block.

4. In paragraph 1, An image decoding method, characterized in that the second block vector is derived by correcting the initial block vector of the selected merge candidate.

5. In paragraph 4, An image decoding method, characterized in that the initial block vector is corrected based on the similarity between a reference block included in a predetermined area of ​​the current picture and the first prediction block.

6. In paragraph 4, The above initial block vector is corrected based on the similarity between the current template of the current block and the candidate template, A video decoding method, characterized in that the above candidate template is included in a predetermined area of ​​the current picture.

7. In paragraph 1, An image decoding method, characterized in that the weight of the first prediction block and the weight of the second prediction block are determined as preset values.

8. In paragraph 1, An image decoding method, characterized in that the weight of the first prediction block and the weight of the second prediction block are determined based on the distance between the current block and the first prediction block and the distance between the current block and the second prediction block.

9. In paragraph 1, An image decoding method, characterized in that the weight of the first prediction block and the weight of the second prediction block are determined based on the quantization coefficient of the first prediction block and the quantization coefficient of the second prediction block.

10. In paragraph 1, An image decoding method, characterized in that the weight of the first prediction block and the weight of the second prediction block are determined based on the prediction mode of the surrounding blocks of the current block.

11. In paragraph 10, An image decoding method, characterized in that the surrounding block includes at least one of an adjacent block or a non-adjacent block of the current block.

12. In paragraph 1, A video decoding method, characterized in that the weight of the first prediction block and the weight of the second prediction block are determined based on at least one of the similarity between the template of the first prediction block and the current template of the current block or the similarity between the template of the second prediction block and the current template of the current block.

13. Step of determining block vector information; A step of deriving a first block vector of a current block based on the above block vector information; A step of selecting one of the merge candidates included in the merge candidate list; A step of deriving a second block vector of the current block based on the selected merge candidate; A step of deriving a first prediction block based on the first block vector and deriving a second prediction block based on the second block vector; and A step of generating a final prediction block of the current block by weighting the first prediction block and the second prediction block, A video encoding method, characterized in that the step of selecting the merge candidate is performed based on the similarity between the reference block indicated by the block vector of the merge candidate included in the merge candidate list and the first prediction block.

14. In a non-transitory computer-readable recording medium storing a bitstream generated by an image encoding method, The above image encoding method is, Step of determining block vector information; A step of deriving a first block vector of a current block based on the above block vector information; A step of selecting one of the merge candidates included in the merge candidate list; A step of deriving a second block vector of the current block based on the selected merge candidate; A step of deriving a first prediction block based on the first block vector and deriving a second prediction block based on the second block vector; and A step of generating a final prediction block of the current block by weighting the first prediction block and the second prediction block, A recording medium, characterized in that the step of selecting the merge candidate is performed based on the similarity between the reference block indicated by the block vector of the merge candidate included in the merge candidate list and the first prediction block.

15. In a method for transmitting a bitstream generated by a video encoding method, The above transmission method includes a step of transmitting the bitstream, The above image encoding method is, Step of determining block vector information; A step of deriving a first block vector of a current block based on the above block vector information; A step of selecting one of the merge candidates included in the merge candidate list; A step of deriving a second block vector of the current block based on the selected merge candidate; A step of deriving a first prediction block based on the first block vector and deriving a second prediction block based on the second block vector; and A step of generating a final prediction block of the current block by weighting the first prediction block and the second prediction block, A transmission method, characterized in that the step of selecting the merge candidate is performed based on the similarity between the reference block indicated by the block vector of the merge candidate included in the merge candidate list and the first prediction block.

Images