Image encoding / decoding method, apparatus, and recording medium having bitstream stored therein

Abstract

Provided are an image encoding / decoding method, an apparatus, a recording medium having a bitstream stored therein, and a transmission method. The image decoding method may comprise the steps of: deriving an AMVP motion vector of the current block; generating an AMVP prediction block of the current block on the basis of the AMVP motion vector; generating an intra prediction block of the current block; and generating a prediction block of the current block by performing weighted sum on the AMVP prediction block and the intra prediction block.

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 using a prediction method that combines intra-prediction and inter-prediction.

[0002] Recently, the demand for high-resolution, high-quality images, such as UHD (Ultra High Definition) images, is increasing across various application fields. As image data becomes higher 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 or wireless broadband lines or storing it using existing storage media leads to increased transmission and storage costs. To address these issues arising from the increasing resolution and quality of image data, high-efficiency image encoding / decoding technologies for higher-resolution and higher-quality images are required.

[0003] Specifically, a method of combining intra prediction and inter prediction can be used in a video encoding / decoding method. The method of combining intra prediction and inter prediction is a technology for generating a prediction signal by weighting an intra prediction signal derived from intra prediction and an inter prediction signal derived from inter prediction.

[0004] According to a method of combining intra-prediction and inter-prediction, instead of transmitting intra-prediction mode information, intra-prediction mode information can be derived using a predetermined method to generate an intra-prediction signal. Furthermore, according to a method of combining intra-prediction and inter-prediction, motion information can be derived and an inter-prediction signal can be generated by transmitting a merge index instead of transmitting motion vector (MV) information. Therefore, the method of combining intra-prediction and inter-prediction can reduce the encoding bits required to generate each prediction signal.

[0005] However, since both intra prediction mode information and motion information are derived and used to generate intra prediction signals and inter prediction signals, the accuracy of the prediction signal may be reduced.

[0006] The present disclosure aims to provide a video encoding / decoding method and device with improved encoding / decoding efficiency.

[0007] 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.

[0008] In addition, the present disclosure aims to provide a prediction method that combines intra prediction and inter prediction with improved prediction accuracy.

[0009] A video decoding method according to one embodiment of the present disclosure may include a step of deriving an AMVP motion vector of a current block, a step of generating an AMVP prediction block of the current block based on the AMVP motion vector, a step of generating an intra prediction block of the current block, and a step of generating a prediction block of the current block by weighting the AMVP prediction block and the intra prediction block.

[0010] In the above image decoding method, the AMVP motion vector of the current block may be derived in units of sub blocks, and the AMVP prediction block of the current block may be generated based on the AMVP motion vector derived in units of sub blocks.

[0011] In the above image decoding method, the intra prediction block of the current block may be generated based on an intra prediction mode derived based on TIMD.

[0012] In the above image decoding method, the intra prediction block of the current block may be generated based on an intra prediction mode derived based on DIMD.

[0013] In the above image decoding method, the intra prediction block of the current block may be generated by performing matrix-based intra prediction.

[0014] In the above image decoding method, the intra prediction block of the current block may be generated by performing intra prediction based on an extrapolation filter.

[0015] In the above image decoding method, the intra prediction block of the current block may be characterized in that it is generated based on a preset intra prediction mode.

[0016] In the above image decoding method, the intra prediction block of the current block may be generated based on the block vector of the current block.

[0017] In the above image decoding method, the intra prediction block of the current block may be generated based on a matching block adjacent to a reference template corresponding to a current template adjacent to the current block.

[0018] In the above image decoding method, the intra prediction block of the current block may be generated based on a matching block indicated by the block vector.

[0019] In the above image decoding method, the weighted sum may be performed by applying a first weight value and a second weight value to the AMVP prediction block and the intra prediction block, respectively, and the first weight value and the second weight value may be determined based on a magnitude value of the motion vector and a magnitude value of the block vector.

[0020] In the above image decoding method, the weighted sum may be performed by applying a first weight value and a second weight value to the AMVP prediction block and the intra prediction block, respectively, and the first weight value may be determined based on a picture of count distance (POC distance) between a current picture including the current block and a reference picture including a reference block of the current block.

[0021] In the above image decoding method, the weighted sum may be performed by applying a first weight value and a second weight value to the AMVP prediction block and the intra prediction block, respectively, and the second weight value may be determined based on a distortion value between a current template adjacent to the current block and a matching template adjacent to a matching block indicated by the block vector.

[0022] A video encoding method according to one embodiment of the present disclosure may include a step of deriving an AMVP motion vector of a current block, a step of generating an AMVP prediction block of the current block based on the AMVP motion vector, a step of generating an intra prediction block of the current block, and a step of generating a prediction block of the current block by weighting the AMVP prediction block and the intra prediction block.

[0023] A non-transitory computer-readable recording medium according to one embodiment of the present disclosure can store a bitstream generated by a video encoding method, the method including the steps of deriving an AMVP motion vector of a current block, generating an AMVP prediction block of the current block based on the AMVP motion vector, generating an intra-prediction block of the current block, and generating a prediction block of the current block by weighting the AMVP prediction block and the intra-prediction block.

[0024] A bitstream transmission method according to one embodiment of the present disclosure can transmit a bitstream generated by a video encoding method, including the steps of deriving an AMVP motion vector of a current block, generating an AMVP prediction block of the current block based on the AMVP motion vector, generating an intra-prediction block of the current block, and generating a prediction block of the current block by weighting the AMVP prediction block and the intra-prediction block.

[0025] 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.

[0026] According to the present disclosure, a video encoding / decoding method and device with improved encoding / decoding efficiency can be provided.

[0027] In addition, according to the present disclosure, it is an object to provide a prediction method that combines intra prediction and inter prediction with improved prediction accuracy.

[0028] 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.

[0029] FIG. 1 is a block diagram showing a configuration according to one embodiment of an encoding device to which the present disclosure is applied.

[0030] FIG. 2 is a block diagram showing a configuration according to one embodiment of a decryption device to which the present disclosure is applied.

[0031] FIG. 3 is a diagram schematically illustrating a video coding system to which the present disclosure can be applied.

[0032] Figure 4 illustrates a method for generating a final prediction signal by combining intra prediction samples and inter prediction samples generated based on the AMVP mode.

[0033] Figure 5 illustrates a method for generating a final prediction signal by combining intra prediction samples and inter prediction samples generated based on a sub-block-based AMVP mode.

[0034] FIG. 6 is a diagram for explaining a matrix-based intra prediction method according to an embodiment of the present disclosure.

[0035] FIG. 7 is a diagram for explaining an intra prediction method based on an extrapolation filter according to one embodiment of the present disclosure.

[0036] FIG. 8 is a diagram for explaining an intra template matching mode prediction method according to an embodiment of the present disclosure.

[0037] FIG. 9 is a diagram for explaining an intra block copy mode prediction method according to one embodiment of the present disclosure.

[0038] FIG. 10 is a flowchart illustrating an image decoding method according to an embodiment of the present disclosure.

[0039] FIG. 11 is a diagram exemplifying a content streaming system to which an embodiment according to the present disclosure can be applied.

[0040] The present invention is susceptible to various modifications and embodiments, and thus 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 substitutes 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 by way of example 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 illustrative embodiments, if properly described, is defined only by the appended claims, along with the full scope equivalents to which such claims are entitled.

[0041] 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.

[0042] 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.

[0043] 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.

[0044] In embodiments, 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 embodiments, the term "a plurality of" may mean one of a number greater than or equal to 2, such as 2, 3, and 4.

[0045] 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.

[0046] Glossary of Terms

[0047] 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.”

[0048] 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.

[0049] Hereinafter, the terms encoder and image encoding device may be used interchangeably and have the same meaning.

[0050] Hereinafter, the terms decoder and image decoding device may be used interchangeably and have the same meaning.

[0051] Hereinafter, “image”, “picture”, “frame” and “screen” may be used with the same meaning and may be used interchangeably.

[0052] 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.

[0053] 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.

[0054] Hereinafter, “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.

[0055] Hereinafter, “inter” and “between screens” may be used interchangeably and have the same meaning.

[0056] Hereinafter, “intra” and “within screen” may be used interchangeably and have the same meaning.

[0057]

[0058] FIG. 1 is a block diagram showing a configuration according to one embodiment of an encoding device to which the present disclosure is applied.

[0059] 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.

[0060] 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).

[0061] 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.

[0062] 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.

[0063] 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.

[0064] 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.

[0065] 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.

[0066] 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.

[0067] 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).

[0068] 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.

[0069] 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 the 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.

[0070] 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.

[0071] 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.

[0072] 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.

[0073] 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.

[0074] 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.

[0075] For example, a 4x4 luminance residual block generated through within-screen 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.

[0076] 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.

[0077] 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.

[0078] 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.

[0079] 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.

[0080] 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.

[0081] 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.

[0082] 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.

[0083] 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).

[0084] 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 or decoding process, and may mean information necessary when encoding or decoding an image.

[0085] 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.

[0086] 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).

[0087] 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).

[0088] 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.

[0089] 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.

[0090] 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.

[0091] Bilateral filter (BIF) can also compensate for the offset from the original image on a sample-by-sample basis for the deblocked image.

[0092] 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.

[0093] 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.

[0094] 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.

[0095] FIG. 2 is a block diagram showing a configuration according to one embodiment of a decryption device to which the present disclosure is applied.

[0096] The decoding device (200) may be a decoder, a video decoding device, or an image decoding device.

[0097] 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).

[0098] 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.

[0099] 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.

[0100] 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.

[0101] 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.

[0102] 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).

[0103] 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.

[0104] 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.

[0105] 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.

[0106] 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.

[0107] 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.

[0108] FIG. 3 is a diagram schematically illustrating a video coding system to which the present disclosure can be applied.

[0109] 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.

[0110] 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.

[0111] 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.

[0112] 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.

[0113] 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).

[0114] 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.

[0115] The rendering unit (23) can render the decrypted video / image. The rendered video / image can be displayed through the display unit.

[0116]

[0117] To explain the prediction method proposed in this disclosure, a combined mode of intra prediction and inter prediction is described.

[0118] In a video encoding method and a video decoding method, a method of combining intra prediction and inter prediction may be a method of generating a prediction sample by weighting intra prediction samples generated by performing intra prediction and inter prediction samples generated by performing inter prediction.

[0119] According to an example of a method for combining intra-prediction and inter-prediction, the intra-prediction mode and inter-prediction mode may be restricted to reduce the encoding bits required to generate intra-prediction samples and inter-prediction samples. For example, the intra-prediction samples may be generated using a template-based intra-mode derivation (TIMD) method, and the inter-prediction samples may be generated using a regular merge mode.

[0120] A template-based intra prediction mode derivation method may be a method of deriving an intra prediction mode for a current block using neighboring templates surrounding the current block, and generating an intra prediction sample using the derived intra prediction mode.

[0121] And, the general merge mode may be a method of generating inter prediction samples by transmitting a merge index indicating one candidate in the generated merge candidate list.

[0122] That is, according to the existing method of combining intra prediction and inter prediction, instead of transmitting intra prediction mode (IPM) information, intra prediction mode information can be derived using the TIMD method, and intra prediction can be performed based on the derived intra prediction mode. In addition, instead of transmitting motion vector (MV) information, motion information can be derived by transmitting a merge index, and inter prediction can be performed using the derived motion information. Therefore, the encoding bits required to generate each prediction sample can be reduced. However, since the intra prediction mode information and motion information used to generate intra prediction samples and inter prediction samples are derived, the accuracy of intra prediction and inter prediction may be lowered.

[0123] Therefore, the present disclosure can propose a method for improving the accuracy of a prediction signal by using a method for transmitting intra prediction mode information and / or a method for transmitting motion information in a combined method of intra prediction and inter prediction.

[0124]

[0125] A method for combining intra prediction and inter prediction according to one embodiment of the present disclosure can generate a prediction sample by combining an intra prediction sample generated by performing intra prediction and an inter prediction sample generated by performing advanced motion vector prediction (AMVP) mode-based inter prediction.

[0126] Specifically, a method for combining intra prediction and inter prediction according to one embodiment of the present disclosure can generate a prediction sample by weighting an intra prediction sample generated based on an intra prediction mode derived based on TIMD and an inter prediction sample generated based on an AMVP mode.

[0127] The method of generating a final prediction signal by combining intra prediction samples and inter prediction samples generated based on AMVP mode can be as described below.

[0128]

[0129] Figure 4 illustrates a method for generating a final prediction signal by combining intra prediction samples and inter prediction samples generated based on the AMVP mode.

[0130] Referring to FIG. 4, in a combined method of intra-prediction and inter-prediction, inter-prediction samples can be generated by performing inter-prediction based on the AMVP mode. In addition, intra-prediction samples can be generated by performing intra-prediction based on the template-based intra-mode derivation (TIMD) method.

[0131] The prediction block generated by performing inter prediction based on the AMVP mode for the current block (410) in the current picture (401) can be referred to as an AMVP prediction block (411). The AMVP prediction block is an AMVP motion vector (MV AMVP , 412) may be a prediction block generated based on the current block. Specifically, the inter prediction of the current block may be performed based on the motion information of the AMVP mode. The AMVP mode motion information may include information about a reference picture (Reference picture, 402) (e.g., Reference index), motion vector candidate information, and motion vector difference information. The encoder may signal the AMVP mode motion information to the decoder.

[0132] According to the AMVP mode-based inter prediction, an AMVP motion vector (412) can be derived. That is, the AMVP motion vector (412) can be derived based on the AMVP mode motion information. Specifically, the motion vector of a surrounding block can be derived as a predicted motion vector based on the motion vector candidate information, and the AMVP motion vector (412) can be derived by adding the predicted motion vector and the differential vector based on the motion vector differential information. Then, an AMVP predicted block (411) of the current block (410) can be generated based on the AMVP motion vector (412).

[0133] A method for deriving a template-based intra prediction mode may be a method for deriving an intra prediction mode based on a predicted value of a current template predicted using a current template, which is a template of a current block (Current block, 410), and reference samples of the template, which are samples adjacent to the current template. Here, the current template and the reference samples of the template may be samples of a reconstructed area (Reconstructed Area, 420) of a current picture (401).

[0134] Specifically, a prediction sample of the current template can be generated by applying arbitrary candidate intra prediction modes to reference samples of the template, which are samples adjacent to the current template. Here, the arbitrary candidate intra prediction mode can be an angular mode and / or a non-angular mode. According to one embodiment, the arbitrary candidate intra prediction modes used in TIMD can include most probable mode (MPM) and / or wide angle intra prediction (WAIP) modes. In addition, the size of the current template can be L1xN and / or L2xM, and L1, L2, N, and M can all be positive integers.

[0135] A similarity between prediction samples of the current template and samples of the reconstructed current template can be derived. The similarity can be derived based on the cost value of the prediction sample of the current template calculated using an arbitrary cost function. Here, among any candidate intra prediction modes, the intra prediction mode with the lowest cost value can be the intra prediction mode derived by TIMD. In addition, prediction samples of the current block (410) can be generated using the intra prediction mode derived by TIMD and reference samples (Reference samples, 421) adjacent to the current block (410).

[0136] When there are multiple intra prediction modes induced by TIMD, prediction samples of the current block (410) generated using the multiple TIMD modes can be weighted summed using a specific weight value.

[0137] That is, the method of combining intra prediction and inter prediction according to one embodiment of the present disclosure can weight and combine intra prediction samples generated based on TIMD and inter prediction samples derived from the AMVP method that transmits motion vector difference (MVD) information, which is a difference value between a motion vector prediction value and a final motion vector value.

[0138] Therefore, the method of combining intra prediction and inter prediction according to one embodiment of the present disclosure can improve the prediction accuracy of the final prediction signal.

[0139]

[0140] Figure 5 illustrates a method for generating a final prediction signal by combining intra prediction samples and inter prediction samples generated based on a sub-block-based AMVP mode.

[0141] Referring to FIG. 5, in a combined method of intra prediction and inter prediction, inter prediction samples may be derived based on a subblock-based advance motion vector prediction (SbAMVP) mode, and intra prediction samples may be derived based on a template-based intra mode derivation (TIMD) method.

[0142] The sub-block-based AMVP method may be a method of dividing the current block into sub-blocks of size MxN and generating a prediction signal by inducing different motion vectors for each sub-block. Here, M and N are arbitrary positive integers smaller than the horizontal length (w) and vertical length (h) of the current block, respectively.

[0143] According to the sub-block-based AMVP method, the AMVP motion vector (MV) of the current block (510) in the current picture (501) AMVP , 512) can be determined based on the reference block (511). Then, in order to derive a motion vector for each of the sub-blocks of the current block (510), the motion vector of the sub-block of the current block (510) can be derived using the motion information corresponding to the center position of each sub-block of the reference block (511).

[0144] Based on the motion vector of each of the sub-blocks of the current block (510), prediction samples of the sub-blocks of the current block (510) can be generated. Then, inter prediction samples of the current block (510) can be generated based on the prediction samples of the sub-blocks.

[0145] In addition, the intra prediction sample of the current block (510) may be a prediction sample derived using an intra prediction mode derived by the TIMD method and a reference sample (Reference sample, 521) adjacent to the current block. Here, the reference sample adjacent to the current block may be a sample of a reconstructed area (Reconstructed Area, 520) of the current picture (501).

[0146] That is, according to the embodiment illustrated by FIG. 5, the method for combining intra-prediction and inter-prediction can weight and combine intra-prediction samples based on a prediction mode derived through the TIMD method and inter-prediction samples derived from a sub-block-based AMVP method. Therefore, the accuracy of the prediction block generated by the method for combining intra-prediction and inter-prediction can be improved.

[0147]

[0148] According to another embodiment of the present disclosure, a method for combining intra-prediction and inter-prediction can generate prediction samples by weighting inter-prediction samples and intra-prediction samples generated based on a method other than TIMD. According to the present disclosure, to improve the accuracy of intra-prediction samples used in the method for combining intra-prediction and inter-prediction, an intra-prediction mode can be derived or intra-prediction mode information can be signaled.

[0149] Accordingly, according to the method proposed in the present disclosure, any of the various intra prediction techniques described below can be selectively used to generate intra prediction samples. Additionally, any intra prediction method not described below can also be used to generate intra prediction samples.

[0150]

[0151] According to one embodiment of the present disclosure, in a prediction method according to a combined method of intra prediction and inter prediction, an intra prediction block for generating a prediction block for a current block can be generated based on a decoder side intra prediction mode derivation (DIMD) method.

[0152] Here, the DIMD method can be performed based on a gradient histogram of neighboring samples adjacent to the current block. According to the DIMD method, an edge detection filter, such as a Sobel filter, a Roberts cross filter, a Prewitt filter, a Schar filter, or a Laplacian filter, can be applied to neighboring samples adjacent to the current block. As a result of applying the edge detection filter to the neighboring samples of the current block, the gradient of the reconstructed sample can be calculated. Then, a gradient histogram can be generated based on the calculated gradient.

[0153] According to one embodiment, the intra prediction mode information may be determined as an intra prediction mode that is mapped to a gradient having a largest value among a histogram of gradients.

[0154] Accordingly, the intra prediction sample of the current block can be generated using the intra prediction mode derived based on the histogram of the gradient and the reference sample of the current block. Then, the prediction sample of the current block can be generated by combining the intra prediction sample of the current block and the inter prediction sample of the current block.

[0155]

[0156] According to one embodiment of the present disclosure, in a prediction method according to a combined method of intra prediction and inter prediction, an intra prediction block for generating a prediction block for a current block can be generated based on a predetermined intra prediction mode.

[0157] For example, a given intra prediction mode may be a given directional mode and / or a given non-directional mode.

[0158] Accordingly, the intra prediction sample of the current block can be generated using a predetermined intra prediction mode and the reference sample of the current block. Then, the prediction sample of the current block can be generated by combining the intra prediction sample of the current block and the inter prediction sample of the current block.

[0159]

[0160] According to one embodiment of the present disclosure, in a prediction method according to a combined method of intra prediction and inter prediction, an intra prediction block can be generated based on a matrix-based intra prediction method.

[0161] A matrix weighted intra prediction (MIP) method for generating intra prediction blocks may be as described below.

[0162]

[0163] FIG. 6 is a diagram for explaining a matrix-based intra prediction method according to an embodiment of the present disclosure.

[0164] Referring to FIG. 6, a previously restored area within a current picture based on a current block (601) may include reference pixels (603) adjacent to the current block (601). Here, the reference pixels (603) may include a left reference pixel and an upper reference pixel. In addition, a set of reference pixels adjacent to the current block (601) may be defined as a reference template. The horizontal and vertical lengths of the reference template may be determined according to the intra prediction mode of the current block (601). For example, when the intra prediction mode of the current block (601) is within a predetermined range, the horizontal length of the reference template may be twice the horizontal length of the current block (601), and the vertical length of the reference template may be twice the vertical length of the current block (601).

[0165] A MIP prediction block for the current block (601) can be generated by multiplying pixels of the reference template by a weight matrix. Here, the matrix weights can be determined based on the size and intra prediction mode of the current block (601).

[0166] Accordingly, the intra prediction sample of the current block (601) can be generated using the pixel and matrix weights of the reference template. Then, the prediction sample of the current block (601) can be generated by combining the intra prediction sample of the current block (601) and the inter prediction sample of the current block (601).

[0167]

[0168] According to one embodiment of the present disclosure, in a prediction method according to a combined method of intra prediction and inter prediction, an intra prediction block for generating a prediction block for a current block can be generated based on an intra prediction method based on an extrapolation filter.

[0169] An intra prediction method based on an extrapolation filter for generating intra prediction blocks may be as described below.

[0170]

[0171] FIG. 7 is a diagram for explaining an intra prediction method based on an extrapolation filter according to one embodiment of the present disclosure.

[0172] Referring to Fig. 7, in the intra-screen prediction method based on an extrapolation filter, prediction can be performed sequentially in a diagonal order from the pixel located at the upper left to the pixel located at the lower right of the current block (Current block, 700). In Fig. 7, in the prediction of each pixel, the pixel in the white area means the pixel of the current block (700) for which prediction is performed as the current pixel (Current pixel, 702), and the pixel in the black area means the reference pixel (Reference pixel, 703). At this time, the reference pixel (703) is a pixel at a predetermined position adjacent to the pixel of the current block (700) for which prediction is performed among the pixels included in the current block (700) and the pixels included in the neighboring reconstructed area (Neighboring reconstructed area, 701).

[0173] Meanwhile, the pixels of the current block (700) can be predicted based on the reference pixels (703) and the filter coefficients of the extrapolation filter.

[0174] For example, the predicted value of the current block (700) pixel can be derived according to mathematical expression 1.

[0175]

[0176] In mathematical expression 1, pred (x,y) refers to a pixel of the current block (700) where prediction is performed. Here, (x, y) refers to the position of the pixel where prediction is performed within the current block (700).

[0177] And, t(x-offsetXi,y-offsetYi) means the value of the reference pixel (703) that is the basis of prediction. Here, (x-offsetX i ,y-offsetY i ) means the position of the reference pixel (703) and offsetX i and offsetY imeans the position offset in the x direction and the y direction, respectively, for the pixels of the current block (700) for which prediction is performed.

[0178] And, c i refers to the filter coefficient of the extrapolation filter. Specifically, c i refers to the (i+1)th filter coefficient derived from the extrapolation filter.

[0179]

[0180] According to one embodiment of the present disclosure, in a prediction method according to a combined method of intra prediction and inter prediction, an intra prediction block for generating a prediction block for a current block can be generated based on an intra template matching prediction method (IntraTMP). The intra template matching mode prediction method means a method of searching for an optimal prediction block in a reconstructed area of ​​a current picture using template matching when the intra prediction mode of the current block is an intra template matching mode, and copying the optimal prediction block to generate a prediction block of the current block.

[0181]

[0182] FIG. 8 is a diagram for explaining an intra template matching mode prediction method according to an embodiment of the present disclosure.

[0183] Referring to FIG. 8, the neighboring L-shaped areas (i.e., the left, top, and upper left areas) of the current block (810) can be defined as the current template (820). Then, a reference template (840) most similar to the current template (820) can be searched within a predefined search range (R1, R2, R3, R4) of the reconstructed area (830) of the current picture (800).

[0184] The prediction block of the current block (810) can be derived based on the corresponding matching block (Matching block, 850) of the determined reference template (840). In addition, the block vector (Block vector, 860) is a vector indicating the matching block (850) of the current block in intra template matching prediction.

[0185] The predefined search ranges R1, R2, R3, and R4 in Fig. 8 can be defined as the current CTU (Coding Tree Unit) including the current block, the upper left CTU, the upper CTU, and the left CTU, respectively.

[0186] Additionally, the predefined search range may be searched for reference templates based on a predefined search order. For example, the reference templates may be searched in a zigzag order of R1, R4, R3, R2.

[0187] Meanwhile, information regarding the search range and the size and shape of the current template can be determined by the encoder and transmitted to the decoder. Furthermore, the search range and the size and shape of the current template can be set to preset values ​​in the encoder / decoder.

[0188] Accordingly, the intra prediction sample of the current block can be generated based on the intra template matching prediction result and the matching block indicated by the block vector. In addition, the prediction sample of the current block can be generated by combining the intra prediction sample of the current block and the inter prediction sample of the current block.

[0189]

[0190] According to one embodiment of the present disclosure, in a prediction method based on a combined method of intra prediction and inter prediction, an intra prediction block for generating a prediction block for a current block can be generated based on an intra block copy (IBC) method. The intra block copy prediction method means a method of searching for an optimal prediction block in a reconstructed area of ​​a current picture using a block vector when the intra prediction mode of the current block is an intra block copy mode, and copying the optimal prediction block to generate a prediction block of the current block.

[0191]

[0192] FIG. 9 is a diagram for explaining an intra block copy mode prediction method according to one embodiment of the present disclosure.

[0193] The intra block copy prediction method means a method of searching for an optimal prediction block in a restored area of ​​the current picture and copying it to generate a prediction block of the current block.

[0194] Referring to FIG. 9, a matching block (Matching Block, 940) corresponding to the current block (910) can be derived within a predefined search range (R1, R2, R3, R4) of a reconstructed area (930) of a current picture (900). Then, a prediction block of the current block (910) can be derived based on the matching block (940). Meanwhile, a block vector (920) is a vector indicating a matching block (940) of the current block (910) in intra block copy prediction.

[0195] The predefined search ranges R1, R2, R3, and R4 in Fig. 9 can be defined as the current CTU (Coding Tree Unit) including the current block, the upper left CTU, the upper CTU, and the left CTU, respectively.

[0196] Additionally, matching blocks may be searched based on a predefined search order within a predefined search range. For example, matching blocks may be searched in a zigzag order of R1, R4, R3, R2.

[0197] Meanwhile, information about the search range can be determined by the encoder and transmitted to the decoder. Furthermore, the search range can be set to a preset value in the encoder / decoder.

[0198] Accordingly, the intra prediction sample of the current block can be generated based on the intra block copy prediction result and the matching block indicated by the block vector. In addition, the prediction sample of the current block can be generated by combining the intra prediction sample of the current block and the inter prediction sample of the current block.

[0199]

[0200] A method for combining intra prediction and inter prediction according to another embodiment of the present disclosure can generate a prediction sample by weighting inter prediction samples generated based on AMVP and intra prediction samples generated based on various intra prediction modes.

[0201] The prediction method according to the present disclosure can generate a final prediction sample by weighting an inter-prediction block generated through inter-prediction using AMVP or sub-block-based AMVP and an intra-prediction block generated through intra-prediction using TIMD or another intra-prediction mode. Here, the intra-prediction block can be generated based on a DIMD method, a MIP method, an EIP method, an intra-template matching method, an intra-block copy prediction method, or can be generated based on a predetermined intra-prediction mode.

[0202]

[0203] According to the method of combining intra prediction and inter prediction of the present disclosure, weight values ​​can be assigned to each of the intra prediction block and the inter prediction block as follows.

[0204] According to one embodiment of the present disclosure, weight values ​​assigned to each of the intra prediction block and the inter prediction block can be assigned in consideration of the characteristics of the intra prediction and the inter prediction.

[0205] In general, the accuracy of prediction samples in an intra prediction block can be inversely proportional to the distance from the reference sample. That is, prediction samples located close to the reference sample can be predicted with high accuracy, while prediction samples located far from the reference sample can be predicted with low accuracy.

[0206] Accordingly, according to one embodiment, for prediction samples located at a close distance from a reference sample, a high weight value may be assigned to a prediction sample of an intra prediction block, and for prediction samples located at a far distance from a reference sample, a high weight value may be assigned to a prediction sample of an inter prediction block.

[0207]

[0208] According to another embodiment, the weight values ​​assigned to each of the intra-prediction block and the inter-prediction block may be assigned based on the size of the motion information used to derive the intra-prediction block and the inter-prediction block. That is, the weight values ​​may be assigned to each of the intra-prediction block and the inter-prediction block by comparing the size of the block vector, which is the motion information for the intra-prediction, with the size of the motion vector, which is the motion information for the inter-prediction.

[0209] For example, if the size of the block vector is larger than the size of the motion vector, larger weight values ​​may be assigned to samples of the inter-prediction block. Conversely, if the size of the motion vector is larger than the size of the block vector, larger weight values ​​may be assigned to prediction samples of the intra-prediction block.

[0210] Conversely, if the size of the block vector is greater than the size of the motion vector, a larger weight value may be assigned to the prediction sample of the intra-prediction block, and if the size of the motion vector is greater than the size of the block vector, a larger weight value may be assigned to the prediction sample of the inter-prediction sample. Here, the sizes of the motion vector and the block vector, respectively, may be calculated by the following mathematical equations 2 and 3.

[0211]

[0212]

[0213] Here, |MV x |Wow |MV y | can indicate the absolute value of the x-axis component and the absolute value of the y-axis component of the motion vector, respectively. And, |BV x |and |BV y | can indicate the absolute value of the x-axis component and the absolute value of the y-axis component of the block vector, respectively.

[0214] According to Equations 2 and 3, both the magnitudes of the x-axis component and the y-axis component can be considered to calculate the magnitude of the motion vector and the magnitude of the block vector. However, according to another example, the magnitude of the motion vector and the magnitude of the block vector can be calculated using only the x-axis component or only the y-axis component. Or, MV x or / and MV y , BV x or / and BV y The magnitude of the motion vector and block vector can be calculated using various methods (e.g., squaring, etc.) based on the values.

[0215] The encoder and decoder may use one of the preset weight assignment methods described above.

[0216] Alternatively, the encoder may selectively use one weight assignment method that can provide high prediction accuracy among the weight assignment methods, and explicitly signal information indicating the selected one weight assignment method to the decoder. Then, the decoder may selectively use the weight assignment method based on the signaled information. Here, the signaled information may indicate a weight assignment method for a specific unit (e.g., a video, a sequence, a group of pictures (GOP), a picture, a slice, a fixed number of coding tree units (CTUs), a coding unit (CU), a picture unit (PU), etc.).

[0217]

[0218] According to another embodiment, the weight values ​​assigned to each of the intra-prediction block and the inter-prediction block may be assigned based on a distortion cost value of a template of each of the intra-prediction block and the inter-prediction block.

[0219] The distortion cost (CostIntraTemplate) value of the intra prediction template can be calculated based on the current template including neighboring samples of the current block and the reference template including neighboring samples of the matching block indicated by the block vector. In addition, the distortion cost (CostIntraTemplate) value of the inter prediction template can be calculated based on the current template including neighboring samples of the current block and the reference template including neighboring samples of the reference block indicated by the motion vector.

[0220] The weight values ​​assigned to the intra prediction samples and inter prediction samples based on the distortion cost values ​​of the intra prediction template and the distortion cost values ​​of the inter prediction template can be calculated as in the following mathematical expressions 4 and 5.

[0221]

[0222]

[0223] Here, WInter and WIntra can indicate the weight value of the inter prediction sample and the weight value of the intra prediction sample, respectively.

[0224]

[0225] According to another embodiment, in order to weight the intra prediction block and the inter prediction block, the weight value assigned to the inter prediction block can be determined as follows.

[0226] Intra-prediction samples, used to generate prediction blocks for the current block, can be generated using information from the current picture. Conversely, inter-prediction samples can be generated using information from reference pictures other than the current picture. As a result, a distance difference (POC distance) exists between the reference picture and the current picture.

[0227] Therefore, considering the characteristics of inter prediction for the current block, the weight value assigned to the inter prediction sample can be determined based on the distance difference between the reference picture and the current picture. That is, if the distance between the current picture and the reference picture is close, a large weight value can be assigned to the inter prediction sample, and conversely, if the distance between the current picture and the reference picture is far, a large weight value can be assigned to the intra prediction sample.

[0228]

[0229] FIG. 10 is a flowchart illustrating an image decoding method according to an embodiment of the present disclosure. The image decoding method of FIG. 10 can be performed by an image decoding device.

[0230] Referring to FIG. 10, the image decoding device can derive the AMVP motion vector of the current block (S1010).

[0231] The video decoding device can generate an AMVP prediction block of the current block based on the AMVP motion vector (S1020). Here, the AMVP motion vector of the current block may be a motion vector derived on a block-by-block basis. Alternatively, the AMVP motion vector of the current block may be derived on a sub-block-by-sub-block basis, and the AMVP prediction block of the current block may be generated based on the AMVP motion vector derived on a sub-block-by-sub-block basis.

[0232] The video decoding device can generate an intra prediction block of the current block (S1030).

[0233] Here, the intra prediction block of the current block can be generated based on the intra prediction mode derived based on TIMD.

[0234] Here, the intra prediction block of the current block can be generated based on the intra prediction mode derived based on DIMD.

[0235] Here, the intra prediction block of the current block can be generated by performing matrix-based intra prediction.

[0236] Here, the intra prediction block of the current block can be generated by performing intra prediction based on an extrapolation filter.

[0237] Here, the intra prediction block of the current block can be generated based on a preset intra prediction mode.

[0238] Here, the intra prediction block of the current block can be generated based on the block vector of the current block.

[0239] Here, the intra prediction block of the current block can be generated based on a matching block adjacent to a reference template corresponding to a current template adjacent to the current block.

[0240] Here, the intra prediction block of the current block can be generated based on the matching block indicated by the block vector.

[0241] The video decoding device can generate a prediction block of the current block by weighting the AMVP prediction block and the intra prediction block (S1040). The weighting can be performed by applying a first weight value and a second weight value to the AMVP prediction block and the intra prediction block, respectively.

[0242] Here, the first weight value and the second weight value can be determined based on the magnitude value of the motion vector and the magnitude value of the block vector.

[0243] Alternatively, the first weight value may be determined based on the picture of count distance (POC distance) between the current picture containing the current block and the reference picture containing the reference block of the current block.

[0244] Alternatively, the second weight value may be determined based on a distortion value between the current template adjacent to the current block and the matching template adjacent to the matching block indicated by the block vector.

[0245] Meanwhile, the steps described in FIG. 10 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. 10. The bitstream can be stored on a non-transitory computer-readable recording medium and can also be transmitted (or streamed).

[0246]

[0247] FIG. 11 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. 11, 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 control 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. In the video decryption method, A step of deriving an AMVP (advanced motion vector prediction) motion vector of the current block; A step of generating an AMVP prediction block of the current block based on the AMVP motion vector; A step of generating an intra prediction block of the current block; and An image decoding method comprising a step of generating a prediction block of the current block by weighting the AMVP prediction block and the intra prediction block.

2. In paragraph 1, The AMVP motion vector of the current block is derived in sub-block units, An image decoding method, characterized in that the AMVP prediction block of the current block is generated based on the AMVP motion vector derived in units of the sub-blocks.

3. In paragraph 1, The intra prediction block of the current block above is, An image decoding method characterized in that it is generated based on an intra prediction mode derived based on TIMD (template based intra mode derivation).

4. In paragraph 1, The intra prediction block of the current block above is, An image decoding method characterized in that it is generated based on an intra prediction mode derived based on DIMD (decoder side intra prediction mode derivation).

5. In paragraph 1, The intra prediction block of the current block above is, An image decoding method characterized in that it is generated by performing matrix-based intra prediction.

6. In paragraph 1, The intra prediction block of the current block above is, An image decoding method characterized in that it is generated by performing intra prediction based on an extrapolation filter.

7. In paragraph 1, The intra prediction block of the current block above is, A video decoding method characterized in that it is generated based on a preset intra prediction mode.

8. In paragraph 1, The intra prediction block of the current block above is, An image decoding method characterized in that it is generated based on a block vector of the current block.

9. In paragraph 8, The intra prediction block of the current block above is, An image decoding method characterized in that a matching block adjacent to a reference template corresponding to a current template adjacent to the current block is generated based on the same.

10. In paragraph 8, The intra prediction block of the current block above is, An image decoding method characterized in that it is generated based on a matching block indicated by the above block vector.

11. In paragraph 8, The above weighted sum is performed by applying a first weight value and a second weight value to the AMVP prediction block and the intra prediction block, respectively, An image decoding method, characterized in that the first weight value and the second weight value are determined based on the magnitude value of the motion vector and the magnitude value of the block vector.

12. In paragraph 8, The above weighted sum is performed by applying a first weight value and a second weight value to the AMVP prediction block and the intra prediction block, respectively, A video decoding method, characterized in that the first weight value is determined based on a picture of count distance (POC distance) between a current picture including the current block and a reference picture including a reference block of the current block.

13. In paragraph 8, The above weighted sum is performed by applying a first weight value and a second weight value to the AMVP prediction block and the intra prediction block, respectively, An image decoding method, characterized in that the second weight value is determined based on a distortion value between a current template adjacent to the current block and a reference template adjacent to a matching block indicated by the block vector.

14. In the video encoding method, A step of deriving the AMVP motion vector of the current block; A step of generating an AMVP prediction block of the current block based on the AMVP motion vector; A step of generating an intra prediction block of the current block; and A video encoding method comprising a step of generating a prediction block of the current block by weighting the AMVP prediction block and the intra prediction block.

15. In a non-transitory computer-readable recording medium storing a bitstream generated by an image encoding method, The above image encoding method is, A step of deriving the AMVP motion vector of the current block; A step of generating an AMVP prediction block of the current block based on the AMVP motion vector; A step of generating an intra prediction block of the current block; and A non-transitory computer-readable recording medium comprising a step of generating a prediction block of the current block by weighting the AMVP prediction block and the intra prediction block.

16. 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, A step of deriving the AMVP motion vector of the current block; A step of generating an AMVP prediction block of the current block based on the AMVP motion vector; A step of generating an intra prediction block of the current block; and A transmission method comprising a step of generating a prediction block of the current block by weighting the AMVP prediction block and the intra prediction block.

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