KR102435675B1 - Method and apparatus for encoding/decoding image, recording medium for stroing bitstream - Google Patents

Abstract

The present invention relates to an image encoding/decoding method and apparatus. An image decoding method for performing intra prediction on a current block according to the present invention includes decoding first information indicating whether residual signal prediction for predicting a residual block of the current block is performed, the first information The method may include performing prediction of the residual signal when α indicates the first value.

Description

Image encoding/decoding method, apparatus, and recording medium storing bitstream

The present invention relates to an image encoding/decoding method and apparatus. Specifically, the present invention relates to a video encoding/decoding method and apparatus using intra prediction, and a recording medium storing a bitstream generated by the video encoding method/apparatus of the present invention.

Recently, the demand for high-resolution and high-quality images such as HD (High Definition) images and UHD (Ultra High Definition) images is increasing in various application fields. As the image data becomes higher resolution and higher quality, the amount of data increases relatively compared to the existing image data. The storage cost will increase. In order to solve these problems that occur as the image data becomes high-resolution and high-quality, high-efficiency image encoding/decoding technology for images having higher resolution and image quality is required.

Inter-screen prediction technology that predicts pixel values included in the current picture from pictures before or after the current picture with image compression technology, intra-picture prediction technology that predicts pixel values included in the current picture using pixel information in the current picture, Various techniques exist, such as transformation and quantization techniques for compressing the energy of the residual signal, and entropy coding techniques that assign short codes to values with high frequency of occurrence and long codes to values with low frequency of occurrence. Image data can be effectively compressed and transmitted or stored.

An object of the present invention is to provide an image encoding/decoding method and apparatus with improved compression efficiency, and a recording medium storing a bitstream generated by the image encoding method/apparatus of the present invention.

Another object of the present invention is to provide a method and apparatus for encoding/decoding an image using intra prediction with improved compression efficiency, and a recording medium storing a bitstream generated by the method/apparatus for encoding an image of the present invention.

Another object of the present invention is to provide an image image encoding/decoding method and apparatus for performing intra prediction using residual signal prediction, and a recording medium storing a bitstream generated by the image encoding method/ apparatus of the present invention. do.

An image decoding method for performing intra prediction on a current block according to the present invention comprises: decoding first information indicating whether residual signal prediction for predicting a residual block of the current block is performed; The method may include performing prediction of the residual signal when 1 information indicates the first value.

In the image decoding method of the present invention, the prediction of the residual signal may be performed based on a previously decoded reconstructed block.

The video decoding method of the present invention further includes decoding an Inta Displacement Vector (IDV), and the previously decoded reconstructed block may be specified by the decoded IDV.

The image decoding method of the present invention may further include decoding an intra prediction mode used for predicting the residual signal, and generating a prediction block of the reconstructed block based on the decoded intra prediction mode. can

The image decoding method of the present invention further includes generating a residual block of the reconstructed block based on the reconstructed block and a prediction block of the reconstructed block, wherein the residual block of the reconstructed block is a residual block of the current block may be a prediction block of

The image decoding method of the present invention includes decoding a secondary residual block of the current block, and generating a residual block of the current block based on a prediction block of the residual block of the current block and the secondary residual block It may include further steps.

In the video decoding method of the present invention, when the information on the IDV is not included in the bitstream, the decoding of the IDV includes using a predetermined search method from among a plurality of IDVs included within a predetermined search range. This can be done by selecting one.

In the video decoding method of the present invention, the predetermined search method may be the same search method used in the video encoding method.

An image decoding apparatus including an intra prediction unit for performing intra prediction on a current block according to the present invention decodes first information indicating whether residual signal prediction for predicting a residual block of the current block is performed and an intra prediction unit for predicting the residual signal when the first information indicates the first value.

An image encoding method for performing intra prediction on a current block according to the present invention includes: performing residual signal prediction for predicting a residual block of the current block, and a first indicating whether the residual signal prediction is performed 1 It may include the step of encoding the information.

In the image encoding method of the present invention, the prediction of the residual signal may be performed based on a pre-decoded reconstructed block.

The video encoding method of the present invention may further include encoding an Inta Displacement Vector (IDV) specifying the pre-decoded reconstructed block.

The video encoding method of the present invention includes determining an intra prediction mode used for predicting the residual signal, generating a prediction block of the reconstructed block based on the determined intra prediction mode, and within the determined intra prediction mode. The method may further include encoding the prediction mode.

In the image encoding method of the present invention, the predetermined search method may include comparing a cost function value of a residual block of the current block with a cost function value of a secondary residual block of the current block.

An image encoding apparatus including an intra prediction unit for performing intra prediction on a current block according to the present invention performs residual signal prediction for predicting a residual block of the current block, and whether the residual signal prediction is performed It may include an intra prediction unit that encodes the first information indicating

A recording medium storing a bitstream generated by an image encoding method for performing intra prediction on a current block according to the present invention includes: performing residual signal prediction for predicting a residual block of the current block; A bitstream generated by an image encoding method including encoding first information indicating whether residual signal prediction is performed may be stored.

According to the present invention, an image encoding/decoding method and apparatus with improved compression efficiency, and a recording medium storing a bitstream generated by the image encoding method/apparatus of the present invention can be provided.

Also, according to the present invention, a method and apparatus for encoding/decoding an image using intra prediction with improved compression efficiency and a recording medium storing a bitstream generated by the method/apparatus for encoding an image of the present invention can be provided.

Further, according to the present invention, there may be provided a video image encoding/decoding method and apparatus for performing intra prediction using residual signal prediction, and a recording medium storing a bitstream generated by the image encoding method/ apparatus of the present invention. have.

1 is a block diagram illustrating a configuration of an encoding apparatus to which the present invention is applied according to an embodiment.
2 is a block diagram illustrating a configuration of a decoding apparatus to which the present invention is applied according to an embodiment.
FIG. 3 is a diagram schematically illustrating a split structure of an image when encoding and decoding an image.
4 is a diagram illustrating a form of a prediction unit (PU) that the encoding unit (CU) may include.
5 is a diagram illustrating a form of a transform unit (TU) that the encoding unit (CU) may include.
6 is a diagram for explaining an embodiment of an intra prediction process.
7 is a diagram for explaining a method of performing intra prediction on a current block according to an embodiment of the present invention.
8 is a diagram for explaining a method of deriving an intra prediction mode of a current block from a neighboring block.
9 is an exemplary diagram for describing a current block, an upper block, and an adjacent block.
10 is a diagram illustrating a syntax structure including information on an intra prediction mode.
11 is a diagram exemplarily illustrating neighboring reconstructed sample lines that can be used for intra prediction of a current block.
12 is a diagram for explaining an embodiment of configuring a reference sample with respect to a sub-block included in a current block.
13 is an exemplary diagram for explaining intra prediction according to the shape of a current block.
14 is a diagram for explaining an embodiment of predicting a residual signal.
15 is a diagram for explaining prediction of a residual signal using a secondary residual signal block.
16 is a diagram for explaining an embodiment of residual signal prediction.
17 is a diagram for explaining an embodiment in which an encoder performs residual signal prediction.
18 is a diagram for explaining an embodiment in which a decoder performs residual signal prediction.

Since the present invention can have various changes and can have various embodiments, specific embodiments are illustrated in the drawings and described in detail in the detailed description. However, this is not intended to limit the present invention to specific embodiments, and should be understood to include all modifications, equivalents and substitutes included in the spirit and scope of the present invention. Like reference numerals in the drawings refer to the same or similar functions throughout the various aspects. The shapes and sizes of elements in the drawings may be exaggerated for clearer description. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS [0014] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS [0010] Reference is made 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 various embodiments are different but need not be mutually exclusive. For example, certain shapes, structures, and characteristics described herein with respect to one embodiment may be implemented in other embodiments without departing from the spirit and scope of the invention. In addition, it should be understood that the location or arrangement of individual components within each disclosed embodiment may be changed without departing from the spirit and scope of the embodiment. Accordingly, the detailed description set forth below is not intended to be taken in a limiting sense, and the scope of exemplary embodiments, if properly described, is limited only by the appended claims, along with all scope equivalents to those as claimed.

In the present invention, terms such as first, second, etc. may be used to describe various elements, but the elements should not be limited by the terms. The above terms are used only for the purpose of distinguishing one component from another. For example, without departing from the scope of the present invention, 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. and/or includes a combination of a plurality of related listed items or any of a plurality of related listed items.

When a component of the present invention is referred to as being “connected” or “connected” to another component, it may be directly connected or connected to the other component, but other components may exist in between. It should be understood that there may be On the other hand, when it is mentioned that a certain element is "directly connected" or "directly connected" to another element, it should be understood that no other element is present in the middle.

Components shown in the embodiment of the present invention are shown independently to represent different characteristic functions, and it does not mean that each component is composed of separate hardware or a single software component. That is, each component is listed as each component for convenience of description, and at least two components of each component are combined to form one component, or one component can be divided into a plurality of components to perform a function, and each Integrated embodiments and separate embodiments of the components are also included in the scope of the present invention without departing from the essence of the present invention.

The terms used in the present invention are only used to describe specific embodiments, and are not intended to limit the present invention. The singular expression includes the plural expression unless the context clearly dictates otherwise. In the present invention, terms such as "comprises" or "have" are intended to designate that the features, numbers, steps, operations, components, parts, or combinations thereof described in the specification exist, but one or more other features It is to be understood that this does not preclude the possibility of the presence or addition of numbers, steps, operations, components, parts, or combinations thereof. That is, the content described as “including” a specific configuration in the present invention does not exclude configurations other than the corresponding configuration, and it means that additional configurations may be included in the practice of the present invention or the scope of the technical spirit of the present invention.

Some components of the present invention are not essential components for performing essential functions in the present invention, but may be optional components for merely improving performance. The present invention can be implemented by including only essential components to implement the essence of the present invention except for components used for improving performance, and only having a structure including essential components excluding optional components used for improving performance Also included in the scope of the present invention.

EMBODIMENT OF THE INVENTION Hereinafter, embodiment of this invention is described concretely with reference to drawings. In describing the embodiments of the present specification, if it is determined that a detailed description of a related known configuration or function may obscure the gist of the present specification, the detailed description is omitted, and the same reference numerals are used for the same components in the drawings. and repeated descriptions of the same components will be omitted.

Also, hereinafter, an image may mean one picture constituting a video, or may indicate a moving picture itself. For example, "encoding and/or decoding of an image" may mean "encoding and/or decoding of a video", and may mean "encoding and/or decoding of one image among images constituting a video". may be Here, a picture may have the same meaning as an image.

Glossary of terms

Encoder: may refer to a device that performs encoding.

Decoder: may refer to a device that performs decoding.

Parsing: may mean determining a value of a syntax element by performing entropy decoding, or may mean entropy decoding itself.

Block: An MxN array of samples, where M and N mean positive integer values, and a block can often mean a two-dimensional sample array.

Sample: A basic unit constituting a block, and values ranging from 0 to 2 ^Bd - 1 can be expressed according to the bit depth (B _d ). In the present invention, a pixel and a pixel may be used interchangeably with a sample.

Unit: may mean a unit of image encoding and decoding. In encoding and decoding of an image, a unit may be a region generated by segmentation of one image. Also, the unit may refer to the divided unit when encoding or decoding an image by dividing it into subdivided units. In encoding and decoding of an image, a process predefined for each unit may be performed. One unit may be further divided into sub-units having a smaller size compared to the unit. According to a function, a unit is a block, a macroblock, a coding tree unit, a coding tree block, a coding unit, a coding unit, a coding block, and a prediction. It may mean a unit (Prediction Unit), a prediction block (Prediction Block), a transform unit (Transform Unit), a transform block (Transform Block), and the like. Also, a unit may mean including a luminance (Luma) component block, a chroma component block corresponding thereto, and a syntax element for each block in order to be distinguished from the block. The unit may have various sizes and shapes, and in particular, the shape of the unit may include not only a rectangle, but also a geometric figure that can be expressed in two dimensions, such as a square, a trapezoid, a triangle, and a pentagon. In addition, the unit information may include at least one of a type of a unit indicating a coding unit, a prediction unit, a transform unit, etc., a size of a unit, a depth of a unit, an encoding and decoding order of the unit, and the like.

Reconstructed Neighbor Unit: may refer to a reconstructed unit that has already been encoded or decoded in a spatial/temporal manner around an encoding/decoding target unit. In this case, the restored neighboring unit may mean a restored neighboring block.

Neighbor block: may refer to a block adjacent to an encoding/decoding target block. A block adjacent to the encoding/decoding object block may mean a block in which a boundary is in contact with the encoding/decoding object block. The neighboring block may refer to a block located at an adjacent vertex of an encoding/decoding target block. The neighboring block may mean a reconstructed neighboring block.

Unit Depth: It means the degree to which a unit is divided. In a tree structure, a root node has the shallowest depth and a leaf node has the deepest depth.

Symbol: may mean an encoding/decoding target unit syntax element, a coding parameter, and a value of a transform coefficient.

Parameter set: may correspond to header information among structures in the bitstream, and may include a video parameter set, a sequence parameter set, a picture parameter set, and an adaptation parameter set. At least one of (adaptation parameter sets) may be included in the parameter set. In addition, the parameter set may have a meaning including slice header and tile header information.

Bitstream: may mean a string of bits including encoded image information.

Transform unit: may refer to a basic unit when performing residual signal encoding/decoding such as transform, inverse transform, quantization, inverse quantization, and transform coefficient encoding/decoding, and one transform unit is It may be divided into a plurality of conversion units having a small size. The transformation unit may have various sizes and shapes, and in particular, the shape of the transformation unit may include not only a rectangle, but also a geometric figure that can be expressed in two dimensions, such as a square, a trapezoid, a triangle, and a pentagon.

Scaling: may refer to a process of multiplying a transform coefficient level by a factor, and may generate a transform coefficient as a result. Scaling may also be referred to as dequantization.

Quantization parameter: may mean a value used when scaling a transform coefficient level in quantization and inverse quantization. In this case, the quantization parameter may be a value mapped to a quantization step size.

Residual quantization parameter (Delta Quantization Parameter): may mean a difference value between a predicted quantization parameter and a quantization parameter of an encoding/decoding target unit.

Scan: It can refer to a method of arranging the order of coefficients in a block or matrix. For example, arranging a 2D array in a 1D array form is called a scan, and a 1D array is converted into a 2D array form. Sorting can also be called a scan or inverse scan.

Transform Coefficient: A coefficient value generated after performing transformation. In the present invention, a quantized transform coefficient level obtained by applying quantization to a transform coefficient may also be included in the meaning of the transform coefficient.

Non-zero transform coefficient: It may mean a transform coefficient having a value of a transform coefficient value of which is not 0 or a level of a transform coefficient having a value of which a value of the value is not 0.

Quantization matrix: may refer to a matrix used in a quantization or inverse quantization process to improve subjective or objective image quality of an image. The quantization matrix may also be referred to as a scaling list.

Quantization matrix coefficient: may mean each element in a quantization matrix. The quantization matrix coefficient may also be referred to as a matrix coefficient.

Default matrix: may mean a predetermined quantization matrix predefined in the encoder and the decoder.

Non-default matrix: It may mean a quantization matrix that is not predefined in an encoder and a decoder and is signaled by a user.

Coding Tree Unit: may be composed of two chrominance component (Cb, Cr) coding tree blocks related to one luminance component (Y) coding tree block. Each coding tree unit may be split using one or more splitting methods such as a quad tree and a binary tree to configure subunits such as a coding unit, a prediction unit, and a transform unit. Like segmentation of an input image, it may be used as a term to refer to a pixel block that becomes a processing unit in an image decoding/encoding process.

Coding tree block: may be used as a term to refer to any one of a Y coding tree block, a Cb coding tree block, and a Cr coding tree block.

1 is a block diagram illustrating a configuration of an encoding apparatus to which the present invention is applied according to an embodiment.

The encoding apparatus 100 may be a video encoding apparatus or an image encoding apparatus. A video may include one or more images. The encoding apparatus 100 may sequentially encode one or more images of a video according to time.

Referring to FIG. 1 , the encoding apparatus 100 includes a motion prediction unit 111 , a motion compensation unit 112 , an intra prediction unit 120 , a switch 115 , a subtractor 125 , a transform unit 130 , and a quantization unit. It may include a unit 140 , an entropy encoder 150 , an inverse quantizer 160 , an inverse transform unit 170 , an adder 175 , a filter unit 180 , and a reference picture buffer 190 .

The encoding apparatus 100 may encode an input image in an intra mode and/or an inter mode. Also, the encoding apparatus 100 may generate a bitstream by encoding an input image, and may output the generated bitstream. When the intra mode is used as the prediction mode, the switch 115 may be switched to the intra mode, and when the inter mode is used as the prediction mode, the switch 115 may be switched to the inter mode. Here, the intra mode may mean an intra prediction mode, and the inter mode may mean an inter prediction mode. The encoding apparatus 100 may generate a prediction block for the input block of the input image. Also, after the prediction block is generated, the encoding apparatus 100 may encode a residual between the input block and the prediction block. The input image may be referred to as a current image that is a target of current encoding. The input block may be referred to as a current block that is a current encoding target or a current encoding target block.

When the prediction mode is the intra mode, the intra prediction unit 120 may use a pixel value of a block already encoded around the current block as a reference pixel. The intra prediction unit 120 may perform spatial prediction using a reference pixel, and may generate prediction samples for an input block through spatial prediction. Here, intra prediction may mean intra prediction.

When the prediction mode is the inter mode, the motion prediction unit 111 may search for a region that best matches the input block from the reference image in the motion prediction process, and may derive a motion vector using the searched region. . The reference image may be stored in the reference picture buffer 190 .

The motion compensator 112 may generate a prediction block by performing motion compensation using a motion vector. Here, the motion vector may be a two-dimensional vector used for inter prediction. Also, the motion vector may indicate an offset between the current image and the reference image. Here, inter prediction may mean inter prediction.

The subtractor 125 may generate a residual block by using the difference between the input block and the prediction block. The residual block may be referred to as a residual signal.

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

A quantized transform coefficient level may be generated by applying quantization to the transform coefficient. Hereinafter, in embodiments, a quantized transform coefficient level may also be referred to as a transform coefficient.

The quantization unit 140 may generate a quantized transform coefficient level by quantizing the transform coefficient according to the quantization parameter, and may output the quantized transform coefficient level. In this case, the quantization unit 140 may quantize the transform coefficients using a quantization matrix.

The entropy encoding unit 150 may generate a bitstream by performing entropy encoding according to a probability distribution on the values calculated by the quantization unit 140 or coding parameter values calculated during the encoding process. and can output a bitstream. The entropy encoding unit 150 may perform entropy encoding on information for decoding an image in addition to information on pixels of the image. For example, information for decoding an image may include a syntax element or the like.

When entropy encoding is applied, a small number of bits are allocated to a symbol having a high probability of occurrence and a large number of bits are allocated to a symbol having a low probability of occurrence to express the symbol, so that bits for symbols to be encoded The size of the column may be reduced. Accordingly, compression efficiency of image encoding may be increased through entropy encoding. The entropy encoder 150 may 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 may perform entropy encoding using a Variable Length Coding/Code (VLC) table. In addition, the entropy encoder 150 derives a binarization method of a target symbol and a probability model of a target symbol/bin, and then performs arithmetic encoding using the derived binarization method or probability model. You may.

The entropy encoder 150 may change the two-dimensional block form coefficient into a one-dimensional vector form through a transform coefficient scanning method in order to encode the transform coefficient level. For example, by scanning the coefficients of a block using up-right scanning, it can be changed into a one-dimensional vector form. A vertical scan for scanning a two-dimensional block shape coefficient in a column direction and a horizontal scan for scanning a two-dimensional block shape coefficient in a row direction may be used instead of the upright scan according to the size of the transform unit and the intra prediction mode. That is, it is possible to determine which scanning method among upright scan, vertical scan, and horizontal scan is to be used according to the size of the transform unit and the intra prediction mode.

Coding parameters, such as syntax elements, may include not only information encoded by an encoder and signaled to a decoder, but also information derived from an encoding or decoding process, and may mean information necessary for encoding or decoding an image. have. For example, block size, block depth, block division information, unit size, unit depth, unit division information, quad tree type division flag, binary tree type division flag, binary tree type division direction, intra prediction mode, Intra prediction direction, reference sample filtering method, prediction block boundary filtering method, filter tap, filter coefficient, inter prediction mode, motion information, motion vector, reference image index, inter prediction direction, inter prediction indicator, reference image list , motion vector predictor, motion vector candidate list, motion merge mode usage, motion merge candidate, motion merge candidate list, skip mode usage, interpolation filter type, motion vector size, motion vector expression accuracy , transform type, transform size, information on whether to use additional (secondary) transform, presence or absence of residual signal information, coded block pattern, coded block flag, quantization parameter, quantization matrix, in-loop filter Information, In-loop filter application information, In-loop filter coefficients, binarization/inverse binarization method, context model, context bin, bypass bin, transform coefficient, transform coefficient level, transform coefficient level scanning method, image display/output order, slice At least one value or a combination of identification information, slice type, slice division information, tile identification information, tile type, tile division information, picture type, bit depth, and information on a luminance signal or a chrominance signal may be included in the encoding parameter. have.

The residual signal may mean a difference between the original signal and the predicted signal. Alternatively, the residual signal may be a signal generated by transforming a difference between the original signal and the predicted signal. Alternatively, the residual signal may be a signal generated by transforming and quantizing the difference between the original signal and the predicted signal. The residual block may be a residual signal in block units.

When the encoding apparatus 100 performs encoding through inter prediction, the encoded current image may be used as a reference image for other image(s) to be processed later. Accordingly, the encoding apparatus 100 may decode the encoded current image again and store the decoded image as a reference image. Inverse quantization and inverse transformation of the current image encoded for decoding may be processed.

The quantized coefficient may be dequantized by the dequantization unit 160 . An inverse transform may be performed in the inverse transform unit 170 . The inverse-quantized and inverse-transformed coefficients may be summed with the prediction block through the adder 175. A reconstructed block may be generated by summing the inverse-quantized and inverse-transformed coefficients and the prediction block.

The reconstruction block may pass through the filter unit 180 . The filter unit 180 applies at least one of a deblocking filter, a sample adaptive offset (SAO), and an adaptive loop filter (ALF) to a reconstructed block or a reconstructed image. can The filter unit 180 may be referred to as an in-loop filter.

The deblocking filter may remove block distortion generated at the boundary between blocks. In order to determine whether to perform the deblocking filter, it may be determined whether to apply the deblocking filter to the current block based on pixels included in several columns or rows included in the block. When a deblocking filter is applied to a block, a strong filter or a weak filter can be applied according to the required deblocking filtering strength. In addition, in applying the deblocking filter, horizontal filtering and vertical filtering may be concurrently processed when performing vertical filtering and horizontal filtering.

In the sample adaptive offset, an appropriate offset value may be added to a pixel value to compensate for an encoding error. The sample adaptive offset may correct an offset from the original image in units of pixels with respect to the image on which the deblocking has been performed. In order to perform offset correction on a specific picture, a method of dividing pixels included in an image into a certain number of regions, determining the region to be offset and applying the offset to the region, or taking edge information of each pixel into account can be used to apply

The adaptive loop filter may perform filtering based on a value obtained by comparing the reconstructed image and the original image. After dividing pixels included in an image into a predetermined group, one filter to be applied to the corresponding group is determined, and filtering can be performed differentially for each group. As for information on whether to apply the adaptive loop filter, the luminance signal may be signaled for each coding unit (CU), and the shape and filter coefficients of the adaptive loop filter to be applied may vary according to each block. In addition, the adaptive loop filter of the same shape (fixed shape) may be applied regardless of the characteristics of the target block.

The reconstructed block that has passed through the filter unit 180 may be stored in the reference picture buffer 190 .

2 is a block diagram illustrating a configuration of a decoding apparatus to which the present invention is applied according to an embodiment.

The decoding apparatus 200 may be a video decoding apparatus or an image decoding apparatus.

Referring to FIG. 2 , the decoding apparatus 200 includes an entropy decoding unit 210 , an inverse quantization unit 220 , an inverse transform unit 230 , an intra prediction unit 240 , a motion compensator 250 , and an adder 255 . , a filter unit 260 and a reference picture buffer 270 may be included.

The decoding apparatus 200 may receive the bitstream output from the encoding apparatus 100 . The decoding apparatus 200 may perform decoding on the bitstream in an intra mode or an inter mode. Also, the decoding apparatus 200 may generate a reconstructed image through decoding and may output the reconstructed image.

When the prediction mode used for decoding is the intra mode, the switch may be switched to the intra mode. When the prediction mode used for decoding is the inter mode, the switch may be switched to the inter mode.

The decoding apparatus 200 may obtain a reconstructed residual block from the input bitstream and generate a prediction block. When the reconstructed residual block and the prediction block are obtained, the decoding apparatus 200 may generate a reconstructed block that is a decoding object block by adding the reconstructed residual block and the prediction block. The decoding object block may be referred to as a current block.

The entropy decoding unit 210 may generate symbols by performing entropy decoding according to a probability distribution on the bitstream. The generated symbols may include symbols in the form of quantized transform coefficient levels. Here, the entropy decoding method may be similar to the entropy encoding method described above. For example, the entropy decoding method may be a reverse process of the above-described entropy encoding method.

The entropy decoding unit 210 may change the one-dimensional vector form coefficient into a two-dimensional block form through a transform coefficient scanning method in order to decode the transform coefficient level. For example, by scanning the coefficients of the block using up-right scanning, it can be changed into a two-dimensional block form. A vertical scan or a horizontal scan may be used instead of the upright scan according to the size of the transform unit and the intra prediction mode. That is, it is possible to determine which scanning method among upright scan, vertical scan, and horizontal scan is to be used according to the size of the transform unit and the intra prediction mode.

The quantized transform coefficient level may be inverse quantized by the inverse quantizer 220 and inversely transformed by the inverse transform unit 230 . As a result of inverse quantization and inverse transformation of the quantized transform coefficient level, a reconstructed residual block may be generated. In this case, the inverse quantizer 220 may apply a quantization matrix to the quantized transform coefficient level.

When the intra mode is used, the intra prediction unit 240 may generate a prediction block by performing spatial prediction using pixel values of an already decoded block around the decoding object block.

When the inter mode is used, the motion compensator 250 may generate a prediction block by performing motion compensation using a motion vector and a reference image stored in the reference picture buffer 270 .

The reconstructed residual block and the prediction block may be added through an adder 255 . A block generated by adding the reconstructed residual block and the prediction block may pass through the filter unit 260 . The filter unit 260 may apply at least one of a deblocking filter, a sample adaptive offset, and an adaptive loop filter to a reconstructed block or a reconstructed image. The filter unit 260 may output a reconstructed image. The reconstructed image may be stored in the reference picture buffer 270 and used for inter prediction.

FIG. 3 is a diagram schematically illustrating a split structure of an image when encoding and decoding an image. 3 schematically shows an embodiment in which one unit is divided into a plurality of sub-units.

In order to efficiently segment an image, a coding unit (CU) may be used in encoding and decoding. Here, the coding unit may mean a coding unit. A unit may be a term that collectively refers to a block including 1) a syntax element and 2) image samples. For example, "division of a unit" may mean "division of a block corresponding to a unit". The block division information may include information about the depth of the unit. The depth information may indicate the number and/or degree to which a unit is divided.

Referring to FIG. 3 , an image 300 is sequentially divided in units of a Largest Coding Unit (LCU), and a division structure is determined in units of LCUs. Here, LCU may be used in the same meaning as a Coding Tree Unit (CTU). One unit may be hierarchically divided with depth information based on a tree structure. Each divided sub-unit may have depth information. Since the depth information indicates the number and/or degree of division of the unit, it may include information on the size of the sub-unit.

The split structure may mean a distribution of coding units (CUs) within the LCU 310 . A CU may be a unit for efficiently encoding/decoding an image. Such a distribution may be determined according to whether one CU is divided into a plurality of CUs (a positive integer of 2 or more including 2, 4, 8, 16, etc.). The horizontal size and vertical size of the CU created by division are half the horizontal size and half the vertical size of the CU before division, respectively, or a size smaller than the horizontal size and vertical size of the CU before division according to the number of divisions. can have The divided CU may be recursively divided into a plurality of CUs having reduced horizontal and vertical sizes in the same manner.

In this case, the division of the CU may be performed recursively to a predefined depth. The depth information may be information indicating the size of a CU, and may be stored for each CU. For example, the depth of the LCU may be 0, and the depth of a Smallest Coding Unit (SCU) may be a predefined maximum depth. Here, the LCU may be a coding unit having the largest coding unit size as described above, and the SCU may be a coding unit having the smallest coding unit size.

The division starts from the LCU 310, and the depth of the CU increases by 1 whenever the horizontal size and the vertical size of the CU are reduced by the division. For each depth, an undivided CU may have a size of 2Nx2N. In the case of a divided CU, a CU having a size of 2Nx2N may be divided into a plurality of CUs having a size of NxN. The size of N is halved for every 1 increase in depth.

For example, when one coding unit is divided into 4 coding units, the horizontal and vertical sizes of the divided 4 coding units may have half sizes compared to the horizontal and vertical sizes of the coding units before splitting. have. For example, when a 32x32 coding unit is divided into 4 coding units, each of the divided 4 coding units may have a size of 16x16. When one coding unit is divided into four coding units, it can be said that the coding unit is divided into a quad-tree.

For example, when one coding unit is split into two coding units, the horizontal or vertical size of the two split coding units may have a half size compared to the horizontal or vertical size of the coding unit before splitting. . For example, when a 32x32 coding unit is vertically split into two coding units, each of the two split coding units may have a size of 16x32. For example, when a 32x32 coding unit is horizontally split into two coding units, the two split coding units may each have a size of 32x16. When one coding unit is split into two coding units, it can be said that the coding unit is split in the form of a binary-tree.

Referring to FIG. 3 , an LCU having a depth of 0 may be 64x64 pixels. 0 may be the minimum depth. An SCU of depth 3 may be 8x8 pixels. 3 may be the maximum depth. In this case, a CU of 64x64 pixels, which is an LCU, may be expressed as depth 0. A CU of 32x32 pixels may be expressed as depth 1. A CU of 16x16 pixels may be expressed as depth 2. A CU of 8x8 pixels, which is an SCU, may be expressed as depth 3 .

Also, information on whether a CU is split may be expressed through split information of the CU. The division information may be 1-bit information. All CUs except for the SCU may include partition information. For example, if the value of the split information is 0, the CU may not be split, and if the value of the split information is 1, the CU may be split.

4 is a diagram illustrating a form of a prediction unit (PU) that the encoding unit (CU) may include.

A CU that is no longer split among CUs split from an LCU may be divided into one or more prediction units (PUs). This treatment may also be referred to as segmentation.

A PU may be a basic unit for prediction. The PU may be encoded and decoded in any one of a skip mode, an inter-picture mode, and an intra-picture mode. The PU may be divided into various forms according to modes.

Also, the coding unit is not divided into prediction units, and the coding unit and the prediction unit may have the same size.

As shown in FIG. 4 , in the skip mode, there may not be a partition in the CU. In the skip mode, a 2Nx2N mode 410 having the same size as a CU without division may be supported.

In the inter-screen mode, 8 types of divided types within a CU may be supported. For example, in the inter-screen mode, 2Nx2N mode 410, 2NxN mode 415, Nx2N mode 420, NxN mode 425, 2NxnU mode 430, 2NxnD mode 435, nLx2N mode 440 and An nRx2N mode 445 may be supported. In the in-screen mode, the 2Nx2N mode 410 and the NxN mode 425 may be supported.

One coding unit may be divided into one or more prediction units, and one prediction unit may also be divided into one or more prediction units.

For example, when one prediction unit is divided into 4 prediction units, the horizontal and vertical sizes of the divided 4 prediction units may have half sizes compared to the horizontal and vertical sizes of the prediction units before division. have. For example, when a 32x32 prediction unit is divided into 4 prediction units, each of the divided 4 prediction units may have a size of 16x16. When one prediction unit is divided into four prediction units, it can be said that the prediction unit is divided into a quad-tree.

For example, when one prediction unit is divided into two prediction units, the horizontal or vertical size of the two divided prediction units may have a half size compared to the horizontal or vertical size of the prediction unit before division. . For example, when a 32×32 prediction unit is vertically split into two prediction units, the two split prediction units may each have a size of 16×32. For example, when a 32x32 prediction unit is horizontally divided into two prediction units, the two divided prediction units may each have a size of 32x16. When one prediction unit is divided into two prediction units, it can be said that the prediction unit is divided in the form of a binary-tree.

5 is a diagram illustrating a form of a transform unit (TU) that the encoding unit (CU) may include.

A transform unit (TU) may be a basic unit used for processes of transform, quantization, inverse transform, and inverse quantization within a CU. The TU may have a shape such as a square shape or a rectangular shape. The TU may be determined depending on the size and/or shape of the CU.

Among CUs split from an LCU, a CU that is no longer split into CUs may be split into one or more TUs. In this case, the partition structure of the TU may be a quad-tree structure. For example, as shown in FIG. 5 , one CU 510 may be divided one or more times according to the quadtree structure. When one CU is split more than once, it can be said to be split recursively. Through division, one CU 510 may be composed of TUs of various sizes. Alternatively, it may be divided into one or more TUs based on the number of vertical and/or horizontal lines dividing the CU. A CU may be divided into symmetric TUs or may be divided into asymmetric TUs. For splitting into an asymmetric TU, information about the size/shape of a TU may be signaled, and may be derived from information about the size/shape of a CU.

Also, the coding unit is not divided into transform units, and the coding unit and the transform unit may have the same size.

One coding unit may be split into one or more transform units, and one transform unit may also be split into one or more transform units.

For example, when one transformation unit is divided into 4 transformation units, the horizontal and vertical sizes of the divided 4 transformation units can have half sizes compared to the horizontal and vertical sizes of the transformation units before being divided. have. For example, when a 32x32 transform unit is divided into 4 transform units, each of the divided 4 transform units may have a size of 16x16. When one transform unit is divided into four transform units, it can be said that the transform unit is divided in a quad-tree form.

For example, when one transformation unit is divided into two transformation units, the horizontal or vertical size of the divided two transformation units may have a half size compared to the horizontal or vertical size of the transformation unit before division. . For example, when a 32x32 transform unit is vertically divided into two transform units, the two divided transform units may each have a size of 16x32. For example, when a transform unit having a size of 32x32 is horizontally divided into two transform units, the two divided transform units may each have a size of 32x16. When one transform unit is divided into two transform units, it can be said that the transform unit is divided into a binary-tree form.

When performing transformation, the residual block may be transformed using at least one of a plurality of pre-defined transformation methods. For example, a Discrete Cosine Transform (DCT), a Discrete Sine Transform (DST), or a KLT may be used as a plurality of pre-defined transform methods. Which transform method is applied to transform the residual block may be determined using at least one of inter-prediction mode information of the prediction unit, intra-prediction mode information, and the size/form of the transform block, and in certain cases indicates the transform method information may be signaled.

6 is a diagram for explaining an embodiment of an intra prediction process.

The intra prediction mode may be a non-directional mode or a directional mode. The non-directional mode may be a DC mode or a planar mode, and the directional mode may be a prediction mode having a specific direction or angle, and the number may be one or more M. The directional mode may be expressed by at least one of a mode number, a mode value, a mode number, and a mode angle.

The number of intra prediction modes may be one or more N including the non-directional mode and the directional mode.

The number of prediction modes in the picture may vary according to the size of the block. For example, the block size may be 67 in case of 4x4 or 8x8, 35 in case of 16x16, 19 in case of 32x32, and 7 in case of 64x64.

The number of intra prediction modes may be fixed to N regardless of the size of the block. For example, at least one of 35 or 67 blocks may be fixed regardless of the size of the block.

The number of prediction modes in the screen may be different depending on the type of color component. For example, the number of prediction modes may be different depending on whether the color component is a luma signal or a chroma signal.

Intra-picture encoding and/or decoding may be performed using sample values or encoding parameters included in neighboring reconstructed blocks.

In order to encode/decode the current block using intra prediction, an operation of checking whether samples included in a neighboring reconstructed block are available as reference samples of the encoding/decoding target block may be performed. When there are samples that cannot be used as reference samples of the encoding/decoding target block, the sample values are copied to samples that cannot be used as reference samples by using at least one or more of samples included in the neighboring reconstructed blocks and/or It can be used as a reference sample of an encoding/decoding target block by interpolation.

During intra prediction, a filter may be applied to at least one of a reference sample and a prediction sample based on at least one of an intra prediction mode and a size of an encoding/decoding target block. In this case, the encoding/decoding target block may mean a current block, and may mean at least one of a coding block, a prediction block, and a transform block. The type of filter applied to the reference sample or the prediction sample may be different according to at least one of an intra prediction mode and a size/shape of the current block. The type of the filter may vary according to at least one of the number of filter taps, a filter coefficient value, and a filter strength.

Among the intra-prediction modes, the non-directional planar mode, when generating the prediction block of the target encoding/decoding block, sets the sample values in the prediction block according to the sample position to the upper reference sample of the current sample, the left reference sample of the current sample, The upper-right reference sample of the current block may be generated as a weighted sum of the lower-left reference samples of the current block.

Among the intra prediction modes, the non-directional DC mode may be generated as an average value of the upper reference samples of the current block and the left reference samples of the current block when the prediction block of the target encoding/decoding block is generated. In addition, filtering may be performed using reference sample values on one or more upper rows and one or more left columns adjacent to the reference sample in the encoding/decoding block.

In the case of a plurality of angular modes among intra prediction modes, a prediction block may be generated using upper right and/or lower left reference samples, and the directional modes may have different directions. In order to generate a predicted sample value, interpolation in real units may be performed.

In order to perform the intra prediction method, the intra prediction mode of the current prediction block may be predicted from the intra prediction mode of the prediction block existing around the current prediction block. When the intra prediction mode of the current prediction block is predicted using the mode information predicted from the neighboring intra prediction mode, if the intra prediction mode of the current prediction block and the neighboring prediction block are the same, the current prediction is made using predetermined flag information It can signal information that the intra prediction modes of the block and the neighboring prediction block are the same, and if the intra prediction modes of the current prediction block and the neighboring prediction block are different from each other, entropy encoding is performed to intra prediction of the encoding/decoding target block. Mode information can be encoded.

7 is a diagram for explaining a method of performing intra prediction on a current block according to an embodiment of the present invention.

As shown in FIG. 7 , intra prediction may include an intra prediction mode induction step ( S1210 ), a reference sample configuration step ( S1220 ), and/or an intra prediction performing step ( S1230 ).

In the intra prediction mode derivation step S1210, the intra prediction mode of the neighboring block is used, the intra prediction mode of the current block is decoded from the bitstream (eg, entropy decoding), or the intra prediction mode of the color component is determined and/or the intra prediction mode of the current block may be derived using the intra prediction mode using the transform model. Alternatively, in the intra prediction mode derivation step ( S1210 ), the current block using the intra prediction mode of the neighboring block, the combination of one or more intra prediction modes of the neighboring block, and/or the intra prediction mode derived using the MPM of the in-screen prediction mode can be induced.

The reference sample configuration step S1220 may configure the reference sample by performing the reference sample selection step and/or the reference sample filtering step.

In the intra prediction operation step S1230 , intra prediction of the current block may be performed using non-directional prediction, directional prediction, location information-based prediction, inter-color prediction, and/or residual signal prediction. In the intra-screen prediction operation ( S1230 ), filtering may be additionally performed on the prediction sample. When directional prediction is performed, another directional prediction may be performed according to one or more sample units. For example, one or more sample units may be a single sample, a sample group, a line, and/or a sub-block.

Hereinafter, the intra prediction mode induction step ( S1210 ) will be described in more detail.

As described above, in order to derive the intra prediction mode for the current block, a method of using an intra prediction mode of one or more neighboring blocks, a method of decoding an intra prediction mode of the current block from a bitstream, and encoding of a neighboring block At least one of a method using a parameter and a method using an intra prediction mode between color components may be used. In this case, the neighboring block may be one or more blocks reconstructed before encoding/decoding of the current block.

When the neighboring block is located outside the boundary of at least one predetermined unit among pictures, slices, tiles, and coding tree units (CTUs), or when PCM mode or inter-picture prediction is applied, the neighboring block may be determined to be unavailable. have. The intra prediction mode corresponding to the unavailable neighboring block may be replaced with a DC mode, a planar mode, or a predetermined intra prediction mode.

The size of the current block may be W x H. W and H are each positive integers and may be the same or different. W and/or H may be, for example, at least one of 2, 4, 8, 16, 32, 64, 128, 256, 512.

8 is a diagram for explaining a method of deriving an intra prediction mode of a current block from a neighboring block.

In FIG. 8 , a to k indicated in a neighboring block may mean an intra prediction mode or a mode number of the corresponding neighboring block. The position of the neighboring block used to derive the intra prediction mode of the current block may be a predefined fixed position. Alternatively, information on the location of the neighboring block may be derived through encoding/decoding. In this specification, encoding/decoding may be used in a sense including entropy encoding and decoding.

When the intra prediction mode of the neighboring block is used, a predetermined mode of the neighboring block may be induced as the intra prediction mode of the current block. For example, the intra prediction mode i, f, b, g, k, j, l, or e of a neighboring block adjacent to a predetermined position of the current block may be induced as the intra prediction mode of the current block. The predetermined position may be encoded/decoded from a bitstream or derived based on an encoding parameter.

Alternatively, one or more neighboring blocks among neighboring blocks of the current block may be selected. The selection may be performed based on information explicitly signaled through a bitstream. Alternatively, the selection may be performed according to criteria preset in the encoder and the decoder. An intra prediction mode of the current block may be derived from intra prediction modes of one or more selected neighboring blocks. For example, the intra prediction mode of the current block may be derived using statistical values of intra prediction modes of the selected neighboring blocks. For example, the statistical value may include a minimum value, a maximum value, an average value, a weighted average value, a mode value, and/or a median value.

For example, statistical values of some or all of the intra prediction modes b, f, g, i, and j of neighboring blocks may be derived as the intra prediction mode of the current block.

Alternatively, the intra prediction mode of the current block may be derived by combining the intra prediction modes of one or more neighboring blocks. The intra prediction mode may be expressed by at least one of a mode number, a mode value, and a mode angle. For example, the average of one or more intra prediction modes of the neighboring block may be derived as the intra prediction mode of the current block. The average of the prediction modes within two screens may mean at least one of an intermediate number of two mode numbers, an intermediate value of two mode values, and an intermediate angle of two mode angles.

For example, a mode corresponding to the average of the mode values of i and f, which is the intra prediction mode of the neighboring block to which the sample adjacent to the left and top of the (0, 0) sample of the current block belongs, is the intra prediction mode of the current block. can be induced by For example, the intra prediction mode Pred_mode of the current block may be derived by at least one of (1) to (3) of Equation 1 below.

Alternatively, when the intra prediction mode i of the neighboring block is the non-directional mode, the intra prediction mode i of the current block may be induced. Alternatively, when the intra-prediction mode f of the neighboring block is the directional mode, the intra-prediction mode of the current block may be induced as f.

Alternatively, the intra prediction mode of the current block may be induced to be a mode corresponding to an average of at least one or more of mode values of b, f, g, i, j, which are intra prediction modes of neighboring blocks. For example, the intra prediction mode Pred_mode of the current block may be derived by at least one of (1) to (4) of Equation 2 below.

Alternatively, a mode corresponding to the average of the available intra prediction modes of adjacent neighboring blocks may be derived as the intra prediction mode of the current block. For example, when the left neighboring block of the current block is located outside the boundary of a picture, tile, slice and/or CTU, or is not available due to at least one of PCM mode or inter-screen mode, within the screen of upper neighboring blocks A mode corresponding to statistical values of prediction modes (eg, f and g) may be induced as an intra prediction mode of the current block.

For example, as a statistical value of intra prediction modes of neighboring blocks, a weighted average or weighted sum may be used. In this case, the weight may be assigned based on the directionality of the intra prediction mode of the neighboring block. For example, modes to which a relatively large weight is given may be predefined or signaled. For example, the modes to which a relatively large weight is given may be at least one of a vertical mode, a horizontal mode, and a non-directional mode. These modes may be given the same weight or may be given different weights. For example, the intra prediction mode Pred_mode of the current block may be derived as a weighted sum of modes i and f using Equation 3 below. In Equation 3 below, the mode f may be a mode to which a relatively large weight is given (eg, a vertical mode).

Alternatively, a weight to be used for weighted summation may be determined based on the size of a neighboring block. For example, when the size of the block adjacent to the top of the current block is larger than the size of the block adjacent to the left, a greater weight may be given to the intra prediction mode of the block adjacent to the top. Alternatively, a greater weight may be given to the intra prediction mode of a neighboring block having a small size.

Alternatively, when one or more intra prediction modes of the neighboring block are the non-directional modes, the non-directional mode may be induced as the intra prediction mode of the current block. Alternatively, the intra prediction mode of the current block may be derived by using the intra prediction mode of the neighboring block except for the non-directional mode. When the intra prediction modes of the neighboring blocks are all non-directional modes, the intra prediction mode of the current block may be induced as at least one of the DC mode and the planar mode.

Alternatively, the intra prediction mode of the current block may be derived using a Most Probable Mode (MPM) based on the intra prediction mode of a neighboring block. When the MPM is used, one or more pieces of information about the intra prediction mode of the current block may be encoded/decoded.

When using MPM, an MPM list may be configured. The MPM list may include an intra prediction mode derived based on an intra prediction mode of a neighboring block. The MPM list may include N candidate modes. N is a positive integer, and a value may vary depending on the size and/or shape of the current block. Alternatively, information about N may be signaled through a bitstream.

For example, the intra prediction mode of the current block derived using the intra prediction mode of the one or more neighboring blocks may be a candidate mode included in the MPM list.

In the example shown in FIG. 8, (-1, H-1), (W-1, -1), (W, -1), (-1, H), (-1, -1) adjacent to the current block ) may use intra prediction modes of blocks adjacent to the sample location, for example, the MPM list may be configured in the order of j, g, Planar, DC, l, k, b. Alternatively, the MPM list may be configured in the order of i, f, Planar, DC, l, k, b. In this case, the overlapping mode may be included only once in the MPM list. When the MPM list is not completely filled because overlapping modes exist, additional candidate modes may be included in the list based on the modes included in the list. For example, a mode corresponding to +N or -N (N is a positive integer, for example, 1) of the modes included in the list may be added to the list. Alternatively, at least one mode not included in the list among horizontal mode, vertical mode, 45 degree mode, 135 degree mode, and 225 degree mode may be added to the list. Alternatively, the MPM list may be constructed using a combination of one or more intra prediction modes of neighboring blocks and/or statistical values.

A plurality of MPM lists may exist, and methods of configuring each MPM list may be different. For example, three MPM lists (MPM list 1, MPM list 2 and MPM list 3) may be configured. In this case, the intra prediction modes included in each MPM list may not overlap.

An indicator (eg, prev_intra_luma_pred_flag) indicating whether the same mode as the intra prediction mode of the current block exists in the derived MPM list may be encoded in the bitstream or may be decoded from the bitstream.

When the indicator indicates that the same mode as the intra prediction mode of the current block exists in the MPM list, index information (eg, mpm_idx) indicating which mode is included in the MPM list is encoded in the bitstream or the bitstream can be decrypted from An intra prediction mode of the current block may be derived based on the decoded index information.

When the indicator indicates that the same mode as the intra prediction mode of the current block does not exist in the MPM list, information about the intra prediction mode of the current block may be encoded in or decoded from the bitstream. The intra prediction mode of the current block may be derived based on the decoded information on the intra prediction mode of the current block. In this case, intra prediction modes not included in the MPM list may be sorted in at least one of an ascending order or a descending order. Alternatively, one or more groups may be configured by selecting one or more among prediction modes not included in the MPM list. For example, one group may be configured using a mode corresponding to +N or -N (N is a positive integer, for example, 1, 2, 3) of the intra prediction mode included in the MPM list. . In this case, the group may be configured in a screen mode corresponding to a predetermined number (eg, 8, 16), and the mode included in the group may be a mode not included in the MPM list.

Alternatively, as described above, when a plurality of MPM lists exist, the indicator (eg, prev_intra_luma_pred_flag) may indicate whether the same mode as the intra prediction mode of the current block exists in the MPM list 1. When the indicator indicates that the same mode does not exist in the MPM list 1, it may be determined whether the same mode exists in the MPM list 2 or not. When the same mode exists in the MPM list 2, the corresponding mode may be induced as an intra prediction mode of the current block. If the same mode does not exist in the MPM list 2, determination may be performed on the MPM list 3 as well. In this way, determination of a plurality of MPM lists may be sequentially performed.

Alternatively, separate information indicating one of a plurality of MPM lists may be transmitted. In this case, the intra prediction mode of the current block may be derived using the MPM list indicated by the separate information and the indicator (eg, prev_intra_luma_pred_flag).

Alternatively, a predetermined candidate of the derived MPM list may be derived as an intra prediction mode of the current block. For example, the intra prediction mode of the current block may be induced as a mode corresponding to the first list 0 of the MPM list. Alternatively, by encoding/decoding an index corresponding to a predetermined mode in the list, the corresponding mode may be induced as an intra prediction mode of the current block.

In configuring the MPM list, one MPM list may be configured for a block of a predetermined size. When the block of the predetermined size is again divided into a plurality of sub-blocks, each of the plurality of sub-blocks may use the configured MPM list.

For example, when the current block corresponds to the block of the predetermined size, an MPM list for the current block may be configured. When the current block is divided into one or more sub-blocks, each of the sub-blocks may derive an intra prediction mode for each of the sub-blocks using the configured MPM list.

In configuring the MPM list, the MPM list for sub-blocks generated by dividing a block of a predetermined size may be configured based on the block of the predetermined size.

For example, when the current block corresponds to the block of the predetermined size, an MPM list for each sub-block in the current block may be constructed by using the intra prediction mode of a block adjacent to the current block.

Alternatively, the intra prediction mode of the current block may be derived using at least one of an intra prediction mode of the current block derived using the MPM and an intra prediction mode of a neighboring block.

For example, when the intra prediction mode of the current block derived using the MPM is Pred_mpm, the intra prediction mode of the current block is changed by changing the Pred_mpm to a predetermined mode using one or more intra prediction modes of the neighboring block. can induce

For example, Pred_mpm may be increased or decreased by N by comparing the intra prediction mode and size of the neighboring block. In this case, N may be a predetermined integer such as +1, +2, +3, 0, -1, -2, or -3. For example, when Pred_mpm is smaller than the statistical values of the intra prediction modes of the neighboring block and/or the intra prediction modes of one or more neighboring blocks, Pred_mpm may be increased. Alternatively, when Pred_mpm is greater than the intra prediction mode of the neighboring block, Pred_mpm may be decreased. Alternatively, it may be derived based on a value compared with Pred_mpm and/or Pred_mpm.

In the example shown in FIG. 8 , for example, when the Pred_mpm is smaller than the mode value of f, Pred_mpm+1 may be induced as the intra prediction mode of the current block. Alternatively, when the Pred_mpm is smaller than the average value of f and i, Pred_mpm + 1 may be induced as the intra prediction mode of the current block. Alternatively, when the Pred_mpm is smaller than the average value of f and i, 1/2 of the difference between the Pred_mpm and the average value may be increased. For example, Pred_mpm + {((f + i + 1) >> 1 - Pred_mpm + 1)>> 1} may be induced as the intra prediction mode of the current block.

Alternatively, when one of the modes of the Pred_mpm and the neighboring block is the non-directional mode and the other is the directional mode, the non-directional mode is induced as the intra prediction mode of the current block or the directional mode is the intra prediction mode of the current block. can be induced by

When the intra prediction mode of the current block is derived using the Most Probable Mode (MPM) list, for example, at least one or more of the following MPM lists may be used. Alternatively, the intra prediction mode of the current block may be entropy encoded/decoded.

- MPM list of current block

- At least one or more of the MPM list of upper blocks for the current block

- At least one or more of the MPM list of adjacent blocks to the current block

In this case, information necessary to configure the MPM list, such as whether the MPM list of the current block is used, whether at least one of the MPM lists of upper blocks for the current block is used, and whether at least one or more of the MPM lists of adjacent blocks for the current block are used VPS (video parameter set), SPS (sequence parameter set), PPS (picture parameter set), APS (adaptation parameter set), slice (slice) header, tile (tile) header, CTU unit, CU unit, PU unit, Entropy encoding/decoding may be performed through at least one of TU units.

The upper block may be a block having a depth value smaller than the depth value of the current block. Also, the upper block may mean at least one or more of the blocks including the current block among the blocks having the small depth value. Here, the depth value may mean a value that increases by 1 whenever a block is divided. For example, the depth value of the unsplit coding tree unit (CTU) may be 0.

In addition, the upper block may mean the following embodiment or a combination of at least one or more of the following embodiments. When the first block is the upper block and the second block is the current block, the first block may include the second block.

Information indicating at least one of a size or a depth of the first block may be signaled from an encoder. The information may be signaled at at least one of a VPS, SPS, picture, slice, tile, and block level.

At least one of the size and depth of the first block may be derived based on at least one of the size and depth of the second block. For example, at least one of the size and depth of the first block may be derived based on a value obtained by adding or subtracting a predetermined constant to a size (or depth) value of the second block (current block). Alternatively, at least one of a size or a depth of the first block may have a fixed value pre-promised by the encoder/decoder.

The adjacent block may be at least one of blocks spatially and/or temporally adjacent to the current block. The adjacent blocks may be already encoded/decoded blocks. Also, the adjacent block may have a depth (or size) value that is the same as or different from that of the current block. The adjacent block may mean a block located at a predetermined position with respect to the current block. Here, the predetermined position may be at least one of upper left, upper, upper right, left, and lower left with respect to the current block.

Alternatively, the predetermined position may be a position in a picture different from the picture to which the current block belongs. The block at the predetermined location may mean at least one of a block co-located with the current block and/or a block adjacent to the co-located block in the other picture. Alternatively, the block at the predetermined position may be a block having the same prediction mode as the current block in a specific region in the other picture corresponding to the current block.

Also, the adjacent block may mean the following embodiment or a combination of at least one or more of the following embodiments. When the first block is an adjacent block and the second block is a current block, the first block may be an coded/decoded block adjacent to the second block.

The first block and the second block may belong to the same coding block (CTU, CU, etc.) or may belong to different coding blocks. The depth and/or size of the first block may be the same as or different from the depth and/or size of the second block.

Here, the MPM list of the upper block or the adjacent block may mean an MPM list configured based on the upper block or the adjacent block. In this case, the intra prediction mode of the encoded/decoded block adjacent to the upper block or the adjacent block may be added to the MPM list of the upper block or the adjacent block.

9 is an exemplary diagram for describing a current block, an upper block, and an adjacent block.

For example, block U (bold solid line block) may be an upper block of blocks F, G, H, I, and J. Alternatively, block V (thick dotted line block) may be an upper block of blocks G, H, I, and J. Alternatively, the block W (dot pattern block) may be an upper block of blocks G, H, and I. Alternatively, block X (rhombus pattern block) may be an upper block of blocks H and I. At least one block included in at least one of the upper blocks may be a current block.

For example, in FIG. 9 , an adjacent block of the current block D may be at least one of B, C, and K. Alternatively, an adjacent block of the current block L may be at least one of C, D, E, H, and K. Alternatively, an adjacent block of the current block P may be at least one of E, H, I, J, L, N, and O. Alternatively, an adjacent block of the current block S may be at least one of I, J, P, Q, and R.

Using the N MPM list, an intra prediction mode of the current block may be derived, or an intra prediction mode of the current block may be entropy encoded/decoded. In this case, N may mean 0 or a positive integer. That is, by using the plurality of MPM lists, the intra prediction mode of the current block may be derived or the intra prediction mode of the current block may be entropy-encoded/decoded. In this case, the N MPM list for the current block may include at least one of the MPM list of the current block, the MPM list of the upper block, and the MPM list of the adjacent block.

Also, the N MPM list may be generated using at least one or more of the encoding parameters of the current block.

Also, at least one of the sub-blocks in the specific block may be the current block, and in this case, the upper block of the sub-block may be the specific block. The sub-block may be a block divided from the specific block. Also, at least one of the sub-blocks that do not correspond to the current block among the sub-blocks divided from the specific block may be adjacent to the current block. Here, the sub-block has the opposite meaning to the upper block and may mean a lower block.

For example, when the current block is referred to as H in FIG. 9 , a plurality of MPM lists for the current block may be configured by at least one of the methods described below.

For example, in FIG. 9 , at least one or more of the MPM lists configured based on at least one of the upper blocks X, W, V, and U may be used to derive the intra prediction mode of the current block H.

For example, in FIG. 9 , when the current block is H, the current block may be configured by at least one of a plurality of MPM lists to be described later.

For example, in FIG. 9 , at least one or more of the MPM lists configured based on at least one or more of the adjacent blocks E and G may be used for the current block H.

The intra prediction mode of the current block may be derived using the configured MPM list or entropy encoded/decoded.

Using the MPM list of the upper block or the adjacent block for the current block H means that the MPM of the upper block or the adjacent block is used for derivation of the intra prediction mode of the current block or encoding/decoding of the intra prediction mode of the current block. It can mean that a list is used.

The plurality of MPM lists for the current block may include MPM lists for N upper blocks. In this case, N may be 0 or a positive integer.

In this case, information such as the number N of the included upper blocks, a depth value, a range of depth values, and/or a difference between a depth value between the current block and an upper block may be required to construct the MPM list of the upper block. Information necessary to configure the MPM list of the upper block is a video parameter set (VPS), a sequence parameter set (SPS), a picture parameter set (PPS), an adaptation parameter set (APS), a slice header, and a tile. Entropy encoding/decoding may be performed in at least one of a header, a CTU unit, a CU unit, a PU unit, and a TU unit.

For example, an MPM list of upper blocks having a depth value of D-K, a depth value of D-1 to D-K, or a depth value of D-K to D-1 may be used for the current block. Here, K and l may be positive integers less than or equal to D. Also, K may be less than l.

For example, when using K upper blocks, the MPM list of at least K upper blocks among upper blocks having depth values from D-1 to D-K and depth values from 0 to K-1 can be used for the current block. have. Here, K may be a positive integer less than or equal to D.

For example, when using K upper blocks, an MPM list of K upper blocks based on the current block may be used. Here, K may be a positive integer less than or equal to D.

When the MPM list of upper blocks is included in the plurality of MPM lists for the current block, the number and/or depth value of the upper blocks used may be derived using size and/or depth information of the current block.

For example, when the current block is a WxH block having a depth value of D, the size of the current block may be expressed by the number of WxH pixels. When the number of pixels in the current block is greater than or equal to a predetermined threshold, the MPM list of at least one upper block among upper blocks having depth values from D-1 to D-K may be used for the current block. Here, K may be a positive integer less than D.

Also, for example, when the number of pixels in the current block is less than a predetermined threshold, the MPM list of at least one upper block among upper blocks having depth values from D-1 to D-L may be used for the current block. . Here, L may be a positive integer greater than K.

For example, when the depth value of the current block is D and D is less than or equal to the predetermined depth value T, the MPM list of at least one upper block among upper blocks having depth values from D-1 to D-K is obtained. Available for the current block. Here, K may be a positive integer less than D.

Also, for example, when the depth value D of the current block is greater than T, the MPM list of at least one upper block among upper blocks having depth values from D-1 to D-L may be used for the current block. Here, L may be a positive integer greater than K.

The plurality of MPM lists for the current block may include MPM lists for N adjacent blocks. The N adjacent blocks may include adjacent blocks at predetermined positions. N may be 0 or a positive integer.

Information such as the number N of the included adjacent blocks, a depth value, a size, and/or a location may be required to construct the MPM list of the adjacent blocks. Information necessary to configure the MPM list of the adjacent block is a video parameter set (VPS), a sequence parameter set (SPS), a picture parameter set (PPS), an adaptation parameter set (APS), a slice header, and a tile. Entropy encoding/decoding may be performed in at least one of a header, a CTU unit, a CU unit, a PU unit, and a TU unit. The number and/or positions of adjacent blocks may be variably determined according to the size, shape, and/or position of the current block. The MPM list of the adjacent block may be configured when the depth value of the adjacent block is a preset value or is included in a predetermined range. In this case, the predetermined range may be defined as at least one of a minimum value and a maximum value. Information about at least one of the minimum value and the maximum value may be entropy-encoded/decoded in the above-described predetermined unit.

For example, in FIG. 9 , when the current block is P and the depth value is D, the plurality of MPM lists for the current block may be configured by at least one of the methods described below. Here, the plurality of MPM lists may include at least one of an MPM list configured based on the current block and an MPM list configured based on an adjacent block of the current block.

For example, at least one MPM list configured based on at least one of the upper-left, upper, upper-right, left, and lower-left adjacent blocks of the current block may be used for the current block P.

Also, the intra prediction mode derived based on at least one of the current block, the upper block, and the adjacent block may be included in one MPM list for the current block. That is, when the current block does not use a plurality of MPM lists and uses one MPM list, at least one of intra prediction modes derived based on at least one of the current block, the upper block, and the adjacent block is used. Thus, the MPM list can be configured.

When the N MPM list for the current block includes the MPM list of at least one or more blocks among upper blocks and adjacent blocks, the order of configuring the N MPM list may be determined. In this case, N may be 0 or a positive integer.

The order constituting the MPM list may be a predetermined order in the encoder and the decoder. Alternatively, the order constituting the MPM list may be determined based on the encoding parameters of each corresponding block (the current block, the upper block, and/or the adjacent block). Alternatively, the information on the order constituting the MPM list may be entropy-encoded/decoded.

For example, in FIG. 9 , the current block may be H, and the MPM list of the current block may be referred to as MPM_LIST_CUR.

In addition, the MPM lists of X, W, V, and U constructed based on the upper block of the current block may be referred to as MPM_LIST_X, MPM_LIST_W, MPM_LIST_V, and MPM_LIST_U, respectively.

In addition, the MPM lists of L, E, and G constructed based on the adjacent blocks of the current block may be referred to as MPM_LIST_L, MPM_LIST_E, and MPM_LIST_G, respectively.

The order of configuring the N MPM list for the current block may be determined by at least one or more of the methods described below. The number of higher-order blocks and/or adjacent blocks used in a method to be described below is only an example, and a different number of blocks may be used.

The MPM list for the current block H may be configured using K MPM lists among MPM_LIST_CUR, the MPM list of at least one upper block, and the MPM list of at least one adjacent block. Here, K may be a positive integer.

The K MPM lists may be used according to a predetermined order. For example, an ascending order or a descending order based on the depth may be used. For example, at least two or more of the MPM list of the current block, the adjacent block, and the upper block may be sorted according to a predetermined order.

In this case, the MPM list with the later order may not include the intra prediction mode included in the MPM list with the earlier order.

In addition, a variable length code of an indicator for the earlier-ordered MPM list may be shorter than a variable-length code of an indicator for the lower-ordered MPM list.

In addition, the earlier MPM list may include a smaller number of candidates than the slower MPM list.

In addition, an indicator for the MPM list may be allocated according to the order of the configured MPM list.

The N MPM lists used for the current block may be expressed as MPM_LIST_1, MPM_LIST_2, ... MPM_LIST_N. At least one of MPM_LIST_CUR, MPM_LIST_X, MPM_LIST_W, MPM_LIST_V, MPM_LIST_U, MPM_LIST_L, MPM_LIST_E, and MPM_LIST_G may correspond to at least one of MPM_LIST_1, MPM_LIST_2, ... MPM_LIST_N.

Here, the number of intra prediction modes that each MPM list can include may be expressed as C1, C2, ... CN. Here, N, C1, C2, ..., CN may be 0 or a positive integer. Some or all of C1 to CN may have the same value or different values. Also, at least one of C1, C2, ... CN may be a predetermined value in the encoder and the decoder. In addition, at least one of C1, C2, ... CN may be determined based on the encoding parameter of each corresponding block. Also, at least one of C1, C2, ... CN may be entropy-encoded/decoded.

Also, for example, intra prediction modes included in the MPM_LIST_1 list may be expressed as MPM_LIST_1_MODE_1, MPM_LIST_1_MODE_2, ..., MPM_LIST_1_MODE_C1.

In order not to include the intra-prediction mode that overlaps between the MPM lists, the intra-prediction mode included in the later MPM list can be used to check the overlap with the intra-prediction mode included in the earlier MPM list. have. If there is an overlapping intra prediction mode after redundancy check, the corresponding intra prediction mode may be excluded from the MPM list. In addition, after the overlapping mode is excluded, a predetermined intra prediction mode may be added to the corresponding MPM list.

Redundancy check for the modes included in the MPM lists may be performed in the step of configuring a plurality of MPM lists. Alternatively, the redundancy check may be performed after configuring all the used MPM lists. Alternatively, the redundancy check may be performed whenever an intra prediction mode is included in the MPM list.

Prediction modes added to supplement the overlapping intra prediction modes are, for example, INTRA_PLANAR, INTRA_DC, horizontal mode, vertical mode, 45 degree mode, 135 degree mode, 225 degree mode MPM_LIST_2_MODE_X±delta, INTRA_DM, At least one of intra prediction modes including INTRA_LM and the like may be included. Here, INTRA_DM may mean an intra prediction mode in which the chrominance intra prediction mode is determined to be the same as the corresponding luminance intra prediction mode. In addition, INTRA_LM may mean an intra prediction mode in which at least one of chrominance prediction/residual/reconstruction blocks is generated based on at least one of luminance prediction/residual/reconstruction blocks. Also, delta may be a positive integer.

For example, when MPM_LIST_K of the current block includes CK intra prediction modes that do not overlap with each other, each intra prediction mode included in MPM_LIST_K is within the picture of MPM_LIST_1, MPM_LIST_2, ... MPM_LIST_(K-1). It may be checked whether the prediction mode overlaps with at least one of the prediction modes. Here, K may be a positive integer less than or equal to N, which is the maximum number of MPM lists that the current block can have.

If MPM_LIST_K_MODE_X, an intra prediction mode included in MPM_LIST_K, overlaps with a mode included in at least one of MPM_LIST_1, MPM_LIST_2, ... MPM_LIST_(K-1), the overlapping intra prediction mode MPM_LIST_K_MODE_X will be excluded from MPM_LIST_K can Here, MPM_LIST_K_MODE_X may be at least one of MPM_LIST_K_MODE_1, MPM_LIST_K_MODE_2, ..., MPM_LIST_K_MODE_CK.

For example, when at least one intra prediction mode is excluded from MPM_LIST_K, at least one of the predetermined intra prediction modes may be included in MPM_LIST_K. In this case, at least one of the predetermined intra prediction modes included in MPM_LIST_K may not overlap with at least one of the intra prediction modes included in MPM_LIST_1, MPM_LIST_2, ..., and MPM_LIST_(K-1). have. Alternatively, at least one of the predetermined intra prediction modes included in MPM_LIST_K may not overlap with all of the intra prediction modes included in MPM_LIST_1, MPM_LIST_2, ..., and MPM_LIST_(K-1).

For example, to supplement intra prediction modes excluded from MPM_LIST_K, intra prediction included in MPM_LIST_1, MPM_LIST_2, ... and MPM_LIST_(K-1) for at least one or more of predetermined intra prediction modes. If there is a predetermined intra prediction mode that does not overlap with at least one or all of the modes, the predetermined intra prediction mode may be added as an intra prediction mode of MPM_LIST_K.

For example, MPM_LIST_K_MODE_X±delta, which is a predetermined intra prediction mode, may be included in MPM_LIST_K while continuously increasing the delta value from 1 to 1 until the number of intra prediction modes included in MPM_LIST_K becomes CK. Alternatively, the predetermined intra prediction modes are arranged in a certain order, and at least one or more of the predetermined intra prediction modes are added to MPM_LIST_K in the order until the number of intra prediction modes included in MPM_LIST_K is CK. can be included

When the intra prediction mode of the current block is derived using the N MPM list or when the intra prediction mode of the current block is entropy-encoded/decoded, among the intra prediction modes included in each of the N MPM lists. An indicator (MPM flag) indicating whether an intra prediction mode identical to the intra prediction mode of the current block exists may be entropy-encoded/decoded for each of the N MPM lists.

For example, when N MPM lists are used, a maximum of N indicators may be encoded/decoded, such as MPM_FLAG_1, MPM_FLAG_2, ... MPM_FLAG_N, for each MPM list. Alternatively, a maximum of (N-1) indicators may be coded/decoded. In this case, the indicator for one MPM list in which the indicator is not coded/decoded is a value of some or all of the (N-1) indicators. can be derived based on For example, the indicator may not be encoded/decoded for any MPM list (eg, the last MPM list according to a predetermined order) among the N MPM lists. Among the intra prediction modes in the specific MPM list, when the same mode as the intra prediction mode of the current block exists, the indicator for the specific MPM list may have a first value, and when the same mode does not exist, the second can have a value. In this case, the first value may be 1, and the second value may be 0. That is, the indicator may be flag information.

In addition, when the indicator for a specific MPM list among the N indicators has a first value, all indicators for the remaining MPM lists except for the indicator for the specific MPM list may have a second value.

Also, when the indicator for the K-th MPM list among the N indicators has a first value, the indicator for the K+1-th MPM list to the N-th MPM list may not be entropy-encoded/decoded. In this case, K may be a positive integer of 1 or more and N or less.

Among the intra prediction modes included in the specific MPM list among the N MPM lists, when the same intra prediction mode as the intra prediction mode of the current block exists, the position or order of the intra prediction mode in the specific MPM list It is possible to entropy-encode index information (MPM index) for . In addition, by entropy-decoding the index information, it is possible to identify the same intra prediction mode as the intra prediction mode of the current block among the intra prediction modes included in the specific MPM list. The index information may be entropy-encoded/decoded into a fixed-length code or a variable-length code. Also, an intra prediction mode of the current block may be derived using the index information.

If the same intra prediction mode as the intra prediction mode of the current block does not exist among the intra prediction modes included in the N MPM list, the encoder selects the remaining intra prediction mode of the current block. Entropy encoding is possible. In this case, the residual intra prediction mode may be used to identify the intra prediction mode of the current block that is not included in at least one of the MPM lists. Alternatively, the residual intra prediction mode may be used to identify an intra prediction mode of the current block that is not included in all candidate intra prediction modes of the MPM lists.

In this case, when the total number of intra prediction modes is Y and the sum of the number of intra prediction modes included in the N MPM lists for the current block is X, Y-X intra predictions by subtracting X from Y Among the modes, a residual intra prediction mode indicating the same intra prediction mode as the intra prediction mode of the current block may be entropy-encoded. In this case, a total of X intra prediction modes included in the N MPM lists may be sorted based on at least one of the size, angle, order, and identification number of the intra prediction mode. The sorting may be an ascending sort or a descending sort. The sorted X intra prediction modes may be compared with the intra prediction mode of the current block. As a result of the comparison, when the intra prediction mode of the current block is greater, a specific value may be subtracted from the intra prediction mode value of the current block. The specific value may be 1.

Or, for example, the mode having the largest reference value (eg, at least one of the size, angle, order, and identification number of the intra prediction mode) among the sorted X intra prediction modes and intra prediction of the current block Modes can be compared. As a result of the comparison, when the value of the intra prediction mode of the current block is greater, a specific value may be subtracted from the intra prediction mode value of the current block.

In addition, the mode having the second largest reference value among the sorted X intra prediction modes may be compared with the intra prediction mode of the current block subtracted by the specific value. As a result of the comparison, when the subtracted intra prediction mode of the current block is greater, the specific value may be additionally subtracted from the subtracted intra prediction mode value of the current block.

Subtraction based on the comparison may be repeatedly performed up to a mode having the smallest reference value among the sorted X intra prediction modes. The finally subtracted intra prediction mode value of the current block may be entropy-encoded as the residual intra prediction mode.

The residual intra prediction mode of the current block is entropy-decoded, and may be used to identify the same intra prediction mode as the intra prediction mode of the current block among intra prediction modes not included in the N MPM list. At this time, when the total number of intra prediction modes is Y and the sum of the total number of intra prediction modes of the N MPM lists for the current block is X, Among the Y-X intra prediction modes, a residual intra prediction mode indicating the same intra prediction mode as the intra prediction mode of the current block may be entropy-decoded.

After entropy-decoding the residual intra prediction modes, the X intra prediction modes may be sorted based on at least one of a size, an angle, an order, and an identification number of the intra prediction modes. The sorting may be an ascending sort or a descending sort. The entropy-decoded residual intra prediction mode may be compared with the X prediction mode values. As a result of the comparison, when the prediction mode value in the entropy-decoded residual picture is greater than or equal to the prediction mode value, the prediction mode value in the entropy-decoded residual picture may be increased to a specific value. The specific value may be 1.

Or, for example, the mode having the smallest reference value (eg, at least one of the size, angle, order, and identification number of the intra prediction mode) among the sorted X intra prediction modes and the decoded residual intra prediction Modes can be compared. As a result of the comparison, if the value of the prediction mode in the residual picture is greater than or equal to the value of the prediction mode in the residual picture, a specific value may be added to the prediction mode value in the residual picture.

Also, among the sorted X intra prediction modes, the mode having the second smallest reference value may be compared with the residual intra prediction mode added to the specific value. As a result of the comparison, if the added residual intra prediction mode is greater than or equal to the same, the specific value may be additionally added from the added residual intra prediction mode value.

The addition based on the comparison may be repeatedly performed up to a mode having the largest reference value among the sorted X intra prediction modes. It is possible to entropy-decode the finally added residual intra prediction mode value to the intra prediction mode of the current block.

A method of entropy encoding/decoding the intra prediction mode of the current block using the N MPM list may be performed as in the following embodiment.

The encoder is MPM_LIST_1, MPM_LIST_2, ... , and when the same intra prediction mode as the intra prediction mode of the current block exists among the intra prediction modes included in MPM_LIST_N, the same intra prediction mode as the intra prediction mode of the current block is MPM_LIST_1, MPM_LIST_2, ... , and MPM_LIST_N, indicators indicating whether it exists in any MPM list MPM_FLAG_1, MPM_FLAG_2, ... , and MPM_FLAG_N may be entropy-encoded. If the intra prediction mode of the current block exists in MPM_LIST_1, MPM_FLAG_1 is the first value, and MPM_FLAG_2, ... except for MPM_FLAG_1, ... , and MPM_FLAG_N may be a second value. In this case, MPM_IDX_1, which is index information for the MPM_LIST_1, may be additionally entropy-encoded.

Alternatively, if the intra prediction mode of the current block exists in MPM_LIST_2, MPM_FLAG_2 is the first value, and MPM_FLAG_1, ... except for MPM_FLAG_2, ... , and MPM_FLAG_N may be a second value. In this case, MPM_IDX_2, which is index information for the MPM_LIST_2, may be additionally entropy-encoded.

Alternatively, if the intra prediction mode of the current block is present in MPM_LIST_N, MPM_FLAG_N is a first value, and MPM_FLAG_1, ... except for MPM_FLAG_N, ... , and MPM_FLAG_(N-1) may be a second value. In this case, MPM_IDX_N, which is index information for the MPM_LIST_N, may be additionally entropy-encoded.

The encoder is MPM_LIST_1, MPM_LIST_2, ... , and when there is no intra prediction mode identical to the intra prediction mode of the current block among the intra prediction modes included in MPM_LIST_N, the same intra prediction mode as the intra prediction mode of the current block is MPM_LIST_1, MPM_LIST_2, ... , and MPM_LIST_N, indicators indicating whether it exists in any MPM list MPM_FLAG_1, MPM_FLAG_2, ... , and MPM_FLAG_N may be entropy-encoded as the second value. MPM_FLAG_1, MPM_FLAG_2, … When , and MPM_FLAG_N are the second values, REM_MODE, which is the residual intra prediction mode, may be additionally entropy-encoded.

In the decoder, the same intra prediction mode as the intra prediction mode of the current block is MPM_LIST_1, MPM_LIST_2, ... , and MPM_LIST_N, indicators indicating whether it exists in any MPM list MPM_FLAG_1, MPM_FLAG_2, ... , and MPM_FLAG_N may be entropy-decoded. MPM_FLAG_1 is the first value, MPM_FLAG_2 excluding MPM_FLAG_1, ... When , and MPM_FLAG_N are the second values, the intra prediction mode of the current block may exist in MPM_LIST_1. In this case, MPM_IDX_1, which is index information for the MPM_LIST_1, is additionally entropy-decoded to induce an intra prediction mode of the current block.

Or, MPM_FLAG_2 is the first value and MPM_FLAG_1, ... except for MPM_FLAG_2. When , and MPM_FLAG_N are the second values, the intra prediction mode of the current block may exist in MPM_LIST_2. In this case, MPM_IDX_2, which is index information for the MPM_LIST_2, is additionally entropy-decoded to induce an intra prediction mode of the current block.

Or, MPM_FLAG_N is the first value and MPM_FLAG_1 excluding MPM_FLAG_N, ... , and MPM_FLAG_(N-1) are the second value, the intra prediction mode of the current block may exist in MPM_LIST_N. In this case, MPM_IDX_N, which is index information for the MPM_LIST_N, is additionally entropy-decoded to induce an intra prediction mode of the current block.

Or, MPM_FLAG_1, MPM_FLAG_2, ... When , and MPM_FLAG_N are the second values, REM_MODE, which is the residual intra prediction mode, is additionally entropy-decoded to induce the intra prediction mode of the current block. At this time, MPM_FLAG_1, MPM_FLAG_2, ... , and MPM_FLAG_N may not all be the first values.

Hereinafter, another embodiment using the N MPM list for the current block will be described.

As in the example of Table 1, the encoder determines MPM_LIST_1, MPM_LIST_2, . , MPM_LIST_N, the intra prediction mode of the current block may be entropy-encoded by sequentially checking whether the same intra prediction mode as the intra prediction mode of the current block exists among the intra prediction modes included in each of MPM_LIST_N.

For example, when the same intra prediction mode as the intra prediction mode of the current block exists in MPM_LIST_1, MPM_FLAG_1 may be entropy-encoded as a first value. In this case, MPM_IDX_1, which is index information for the MPM_LIST_1, may be additionally entropy-encoded.

For example, when the same intra prediction mode as the intra prediction mode of the current block does not exist in MPM_LIST_1, MPM_FLAG_1 may be entropy-encoded as a second value. In this case, when the same intra prediction mode as the intra prediction mode of the current block exists in MPM_LIST_2 (when MPM_FLAG_1 is the second value), MPM_FLAG_2 may be entropy-encoded as the first value. In this case, MPM_IDX_2, which is index information for the MPM_LIST_2, may be additionally entropy-encoded.

For example, the same intra prediction mode as the intra prediction mode of the current block is MPM_LIST_1, MPM_LIST_2, ... , if it does not exist in MPM_LIST_(N-1), MPM_FLAG_1, MPM_FLAG_2, ... , MPM_FLAG_(N-1) may be entropy-encoded as the second value. In this case, if the same intra prediction mode as the intra prediction mode of the current block exists in MPM_LIST_N (MPM_FLAG_1, MPM_FLAG_2, ..., MPM_FLAG_(N-1) is the second value), the MPM_FLAG_N is entropy-encoded as the first value. can In this case, MPM_IDX_N, which is index information for the MPM_LIST_N, may be additionally entropy-encoded.

For example, the same intra prediction mode as the intra prediction mode of the current block is MPM_LIST_1, MPM_LIST_2, ... , if not present in MPM_LIST_N, MPM_FLAG_1, MPM_FLAG_2, ... , MPM_FLAG_N may be entropy-encoded as a second value. In this case, REM_MODE, which is the prediction mode in the residual picture, may be additionally entropy-encoded.

As in the example of Table 1, in the decoder, the same intra prediction mode as the intra prediction mode of the current block is MPM_LIST_1, MPM_LIST_2, ... , MPM_LIST_N, an indicator indicating whether it exists in any MPM list MPM_FLAG_1, MPM_FLAG_2, ... , MPM_FLAG_N may be sequentially entropy-decoded according to at least one method of an order of configuring the plurality of MPM lists.

For example, when MPM_FLAG_1 is entropy-decoded as a first value, the intra-prediction mode of the current block is present in MPM_LIST_1, and MPM_IDX_1, which is index information for the MPM_LIST_1, is additionally entropy-decoded to induce the intra-prediction mode of the current block. can do.

For example, MPM_FLAG_1, MPM_FLAG_2, ... , MPM_FLAG_(N-1) may be entropy-decoded to the second value, MPM_FLAG_N may be entropy-decoded. When the decoded MPM_FLAG_N is the first value, the intra prediction mode of the current block exists in MPM_LIST_N, and MPM_IDX_N, which is index information for the MPM_LIST_N, is additionally entropy-decoded to induce the intra prediction mode of the current block.

For example, MPM_FLAG_1, MPM_FLAG_2, ... , MPM_FLAG_N is entropy-decoded as the second value, REM_MODE, which is the residual intra-prediction mode, is additionally entropy-decoded to induce the intra-prediction mode of the current block. At this time, MPM_FLAG_1, MPM_FLAG_2, ... , determining whether MPM_FLAG_N is the first value or the second value may be sequentially performed.

Like the aforementioned MPM_FLAG_N, the MPM list may be specified in the form of a flag, or may be encoded/decoded in the form of an index specifying any one MPM list among a plurality of MPM lists. Information on whether the MPM-based intra prediction mode derivation method is used in the current block (or the current slice, the current picture, the current sequence, etc.) may be encoded/decoded. The index may be encoded/decoded when an MPM-based intra prediction mode derivation method is used according to the information. At least one of the number or type of the MPM list belonging to the plurality of MPM lists may be a fixed one predefined in the encoder/decoder, or variable based on parameters related to the size, depth, shape, position, etc. of the current block/neighboring block. may be determined as For example, the number of pre-defined MPM lists in the encoder/decoder may be 1, 2, 3 or more values. The maximum number of intra prediction modes belonging to each MPM list may be forced to be equal to each other. In this case, the maximum number may be a fixed one that is pre-promised to the encoder/decoder, or may be signaled in a predetermined unit (eg, sequence, picture, slice, block, etc.). When the number of prediction modes in a screen belonging to a specific MPM list is less than the maximum number, a predetermined mode may be added. In this case, the added mode may be a pre-promised default mode or an intra-screen prediction mode belonging to another MPM list. However, a mode that is not the same as the pre-included intra-screen prediction mode of the specific MPM list may be added. Redundancy check may be omitted between each MPM list. Any one of the MPM lists may share at least one same intra prediction mode with the other MPM list.

Hereinafter, another embodiment using N MPM lists for the current block will be described.

The encoder may configure a plurality of MPM lists from MPM_LIST_1 to MPM_LIST_N according to at least one method among the orders of configuring the plurality of MPM lists. The number of prediction modes in the total candidate picture of the N MPM lists may be K. Here, N and K may be positive integers.

For example, MPM_LIST_combined including prediction modes less than or equal to K among candidate intra prediction modes of the N MPM lists may be configured.

For example, if the same intra prediction mode as the intra prediction mode of the current block exists in MPM_LIST_combined, the indicator MPM_FLAG_combined indicating whether the same intra prediction mode as the intra prediction mode of the current block exists in MPM_LIST_combined is the first Values can be entropy-encoded. In this case, MPM_IDX_combined, which is index information for the MPM_LIST_combined, may be additionally entropy-encoded.

When the same intra prediction mode as the intra prediction mode of the current block does not exist in MPM_LIST_combined, MPM_FLAG_combined may be entropy-encoded as a second value. When MPM_FLAG_combined is the second value, REM_MODE, which is the residual intra prediction mode, may be additionally entropy-encoded.

The decoder may entropy-decode an indicator MPM_FLAG_combined indicating whether an intra prediction mode identical to the intra prediction mode of the current block exists in MPM_LIST_combined. When MPM_FLAG_combined is the first value, MPM_IDX_combined, which is the index information, is additionally entropy-decoded to induce an intra prediction mode of the current block. When MPM_FLAG_combined is the second value, REM_MODE, which is the residual intra prediction mode, is additionally entropy-decoded to induce the intra prediction mode of the current block.

According to the present invention, the intra prediction mode of the current block can be derived by encoding/decoding. In this case, the intra prediction mode of the current block can be entropy encoded/decoded without using the intra prediction mode of the neighboring block. have.

According to the present invention, in order to derive the intra prediction mode of the current block, an intra prediction mode of a different color component may be used. For example, when the current block is a chrominance block, an intra prediction mode of one or more luminance-corresponding blocks corresponding to the chrominance object block may be used to derive an intra prediction mode for the chrominance block. In this case, the luminance-corresponding block may be determined based on at least one of a size, a shape, and an encoding parameter of the chrominance block. Alternatively, the luminance-corresponding block may be determined based on at least one of a size, a shape, and an encoding parameter of the luminance block.

Information on intra prediction may be entropy-encoded/decoded from a bitstream. 10 is a diagram illustrating a syntax structure including information on an intra prediction mode. As shown in FIG. 10 , the information about intra prediction may include at least one or more of the following information. In this case, the information on the intra prediction is a video parameter set (VPS), a sequence parameter set (SPS), a picture parameter set (PPS), an adaptation parameter set (APS), a slice header, and a tile header. It may be signaled through at least one.

A flag indicating whether to perform residual signal prediction: ex) SRP_flag

The information on the intra prediction may be entropy-encoded/decoded from the bitstream based on at least one of the encoding parameters.

At least one or more of the information on the intra prediction may not be signaled based on at least one of a size and a shape of a block.

For example, when the size of the current block corresponds to a predetermined size, at least one piece of information about intra prediction for the current block is not signaled, and intra prediction corresponding to the previously encoded/decoded upper block size is not signaled. One or more pieces of information about

For example, when the shape of the current block is rectangular, one or more pieces of information about intra prediction for the current block are not signaled, and one or more pieces of information about intra prediction corresponding to a previously encoded/decoded upper block size. can be used

When the SRP_flag is 1, prediction of the residual signal may be performed using the intra-picture mode determined for the current block or sub-block.

At least one of the following binarization methods may be used when entropy encoding/decoding at least one or more of the intra prediction information.

- The method of binarization of truncated rice

- K-th order Exp_Golomb binarization method

- Limited K-th order Exp_Golomb binarization method

- Fixed-length binarization method

- Unary binarization method

- Truncated Unary binarization method

Hereinafter, the reference sample configuration step (S1220) will be described in more detail.

When intra prediction is performed on the current block or a subblock having a smaller size and/or shape than the current block based on the derived intra prediction mode, a reference sample used for prediction may be configured. Hereinafter, description will be made based on the current block, and the current block may mean a sub-block. The reference sample may be constructed using one or more reconstructed samples or sample combinations around the current block. Additionally, filtering may be applied in configuring the reference sample. In this case, the reference sample may be configured by using each of the reconstructed samples on the plurality of reconstructed sample lines as they are. Alternatively, a reference sample may be configured after filtering between samples on the same reconstructed sample line. Alternatively, a reference sample may be configured after filtering between samples on different reconstructed sample lines. The configured reference sample may be represented by ref[m, n], and a neighboring reconstructed sample or a filtered sample may be represented by rec[m, n]. In this case, m or n may be a predetermined integer value. When the size of the current block is W (horizontal) x H (vertical), when the upper left sample position in the current block is (0, 0), the relative position of the closest upper left reference sample based on the sample position It can be set to (-1, -1).

11 is a diagram exemplarily illustrating neighboring reconstructed sample lines that can be used for intra prediction of a current block.

11 , a reference sample may be constructed using one or more reconstructed sample lines adjacent to the current block.

For example, one line may be selected from among the plurality of reconstructed sample lines illustrated in FIG. 11 , and a reference sample may be constructed using the selected reconstructed sample line. The selected reconstructed sample line may be fixedly selected as a specific line from among a plurality of reconstructed sample lines. Alternatively, the selected reconstructed sample line may be adaptively selected as a specific line among a plurality of reconstructed sample lines. In this case, an indicator for the selected reconstructed sample line may be signaled.

For example, a reference sample may be configured using a combination of one or more reconstructed sample lines among the plurality of reconstructed sample lines illustrated in FIG. 11 . As an example, the reference sample may be composed of a weighted sum (or weighted average) of one or more reconstructed samples. The weight used for the weighted sum may be assigned based on the distance from the current block. In this case, the closer to the current block, the greater the weight may be given, for example, Equation 4 below may be used.

Alternatively, the reference sample may be constructed using at least one of an average value, a maximum value, a minimum value, a median value, and a mode value of a plurality of reconstructed samples based on at least one of a distance from the current block or an intra prediction mode.

Alternatively, a reference sample may be configured based on a change (amount of change) of values of a plurality of consecutive reconstructed samples. For example, the reference sample may be configured based on at least one or more, such as whether values of two consecutive reconstructed samples differ by more than a threshold or whether values of a plurality of consecutive reconstructed samples change continuously or discontinuously. For example, if rec[-1, -1] differs from rec[-2, -1] by more than a threshold, ref[-1, -1] is determined as rec[-1, -1] or rec[- 1, -1] may be determined as a value obtained by applying a weighted average to which a predetermined weight is assigned. For example, when values of a plurality of consecutive reconstructed samples change by n as they approach the current block, reference samples ref[-1, -1] = rec[-1, -1]-n may be determined.

At least one of the number, position, and construction method of the reconstructed sample lines used for constructing the reference sample is that the upper or left boundary of the current block corresponds to the boundary of at least one of a picture, a slice, a tile, and a coding tree block (CTB). In some cases, it may be determined differently.

For example, in constructing a reference sample using reconstructed sample lines 1 and 2, if the upper boundary of the current block corresponds to the CTB boundary, reconstructed sample line 1 is used for the upper side, and the reconstructed sample line is used for the left side. 1 and 2 are available.

For example, in configuring reference samples using reconstructed sample lines 1 to 4, if the upper boundary of the current block corresponds to the CTB boundary, reconstructed sample lines 1 and 2 are used for the upper side and reconstructed samples are used for the left side. Lines 1 to 4 may be used.

For example, in constructing a reference sample using reconstructed sample line 2, if the upper boundary of the current block corresponds to the CTB boundary, reconstructed sample line 1 is used for the upper side, and reconstructed sample line 2 is used for the left side. Available.

One or more lines of the reference sample constructed through the above process may be plural.

A method of constructing a reference sample at the top of the current block may be different from a method of constructing a reference sample at the left side of the current block.

Information indicating that the reference sample is constructed by at least one of the above methods may be encoded/decoded. For example, information indicating whether a plurality of reconstructed sample lines is used may be encoded/decoded.

When the current block is divided into a plurality of sub-blocks and each sub-block has an independent intra prediction mode, a reference sample may be configured for each sub-block.

12 is a diagram for explaining an embodiment of configuring a reference sample with respect to a sub-block included in a current block.

As shown in FIG. 12 , when the current block is 16x16 and 16 4x4 subblocks have independent intra prediction modes, the reference sample of each subblock is at least one of the following according to a scanning method for performing prediction of the subblock. can be configured in this way.

For example, a reference sample of each sub-block may be constructed using N reconstructed sample lines adjacent to the current block. The example shown in FIG. 12 is a case where N is 1.

For example, when predicting a plurality of sub-blocks according to a raster scan order (1->2->3->….15->16), in configuring the reference sample of the K-th sub-block A reference sample may be constructed using samples of at least one or more of the encoded/decoded left, upper, upper right, and lower left sub-blocks.

When predicting a plurality of sub-blocks according to a scan order other than the raster scan order, in constructing the reference sample of the K-th sub-block, pre-encoded/decoded samples of the left, upper, upper right, and lower left sub-blocks are used. A reference sample may be constructed.

The scan order other than the above raster scan order is Z-scan order (1->2->5->6->3->4->7->…12->15->16), zigzag scan (zigzag- scan order (1->2->5->9->6->3->4->…12->15->16) or vertical scan order (1->5-> 9->13->2->6->… 8->12->16) and the like.

In selecting the reference sample, determination of availability and/or padding of a block including the reference sample may be performed. For example, when a block including a reference sample is available, the corresponding reference sample may be used. Meanwhile, when the block including the reference sample is not available, the unavailable reference sample may be padded and replaced by using one or more possible reference samples nearby.

When the reference sample is outside at least one of a picture, a tile, a slice, a coding tree block (CTB), and a predetermined boundary, it may be determined that the reference sample is not available.

In the case of encoding the current block by constrained intra prediction (CIP), if the block including the reference sample is encoded/decoded in the inter-picture mode, it may be determined that the reference sample is not available.

13 is an exemplary diagram for explaining intra prediction according to the shape of a current block.

For example, as shown in (a) of FIG. 13 , when the shape of the current block is a square, prediction may be performed using the average value of the reference samples at the top and the left side of the current block.

For example, as shown in (b) of FIG. 13 , when the shape of the current block is a rectangle, prediction may be performed using an average value of reference samples adjacent to the longer side among the width and length of the current block. .

For example, when the size of the current block falls within a predetermined range, predetermined samples may be selected from among reference samples at the top or left side of the current block, and prediction may be performed using an average value of the selected samples.

For example, intra prediction in the DC mode may be performed using an average value of one or more reference samples among the configured reference samples. In this case, for example, Equation 5 below may be used.

In this case, filtering may be applied to one or more prediction samples located at the boundary of the current block. For example, filtering may be performed on a plurality of N columns and/or rows on the left and/or top of the current block. In this case, N may be a positive integer greater than 1.

14 is a diagram for explaining an embodiment of predicting a residual signal.

Residual signal prediction may be additionally performed on a residual signal constructed from intra prediction.

In the intra prediction, the current block is predicted by using samples of pre-encoded/decoded adjacent blocks as reference samples. Accordingly, as the distance between the sample of the current block and the reference sample increases, the residual signal tends to increase, which may decrease encoding efficiency.

For the purpose of further reducing the residual signal, prediction of the residual signal may be additionally performed in units of current blocks or sub-blocks.

A search range may be set for reconstructed blocks that have been pre-encoded/decoded before the current block and reconstructed. The search range may be set differently according to the size, shape, division depth, and/or intra prediction mode of the current block.

For example, all blocks reconstructed before the current block may be set as a search range. When a block located to the left of the current block, a block located to the upper left, a block located to the top, and/or a block located to the upper right of the current block are included in the search range, a partial area of the reconstructed block is the current block or a block that has not yet been encoded. Blocks after the current block may be included. In this case, the corresponding sample value may be filled by padding using available sample values in the reconstruction block, or the blocks may be excluded from the search range.

For example, N blocks among blocks reconstructed before the current block may be set as a search range. In this case, N may be a positive integer of 1 or more.

For example, as shown in FIG. 14 , when the horizontal length of the current block (CUR_BLK) is W and the vertical length is H, and the position of the upper left pixel of the current block is defined as (0, 0), (-2 *W, -2*H), (-W, -2*H), (0, -2*H), (W, -2*H), (-2*W, -H), (-W , -H), (0, -H), (W, -H), (-2*W, 0), (-W, 0) 10 reconstruction blocks containing pixels at positions can

For example, when the current block is a non-square block having different horizontal (W) and vertical (H) lengths, the search range may be set depending on W and/or H values. For example, in the case of a WxH non-square block, the search range may be set to (K*W)x(L*H) in the area of reconstructed adjacent blocks. In this case, each of K and L may be a positive integer of 1 or more.

A prediction block of the current block may be configured using an intra prediction mode (predModeIntra) of the current block determined by performing intra prediction among the various intra prediction modes described above.

For example, in FIG. 14 , a prediction block constructed using predModeIntra may be expressed as PRD_BLK_best.

In addition to the prediction block (PRD_BLK_best) configured through predModeIntra, one or more prediction blocks of the current block may be additionally configured.

For example, at least one additional prediction block may be configured using at least one of all directional/non-directional intra prediction modes.

For example, an additional prediction block may be configured using N intra prediction modes adjacent to predModeIntra based on predModeIntra. In this case, N may be a positive integer of 1 or more. For example, as shown in FIG. 14 , when N=2, two additional prediction blocks PRD_BLK_plus_one and PRD_BLK_minus_one may be configured. For example, when predModeIntra is a directional mode, an additional prediction block (PRD_BLK_plus_one) may be configured using predModeIntra+1, and another additional prediction block may be configured using predModeIntra-1. The number added to or subtracted from the predModeIntra may be a positive integer of 1 or more.

For example, an additional prediction block may be configured using N adjacent intra prediction modes based on an angle formed with predModeIntra. In this case, N may be a positive integer of 1 or more. In this case, when the angle is θ, an additional prediction block may be configured using an intra prediction mode included in the angle range from -θ to +θ based on predModeIntra.

For example, by combining N additional prediction blocks constructed using N intra-picture modes, M additional prediction blocks may be configured. In this case, M and N may be positive integers. For example, when predModeIntra is PLANAR_MODE, which is a non-directional mode, an additional prediction block (PRD_BLK_plus_one) may be configured using DC_MODE, and another additional prediction block (PRD_BLK_minus_one) may be configured by a weighted sum of PRD_BLK_best and PRD_BLK_plus_one. Alternatively, when predModeIntra is DC_MODE, which is a non-directional mode, an additional prediction block (PRD_BLK_plus_one) may be configured using PLANAR_MODE, and another additional prediction block (PRD_BLK_minus_one) may be configured by a weighted sum of PRD_BLK_best and PRD_BLK_plus_one. Alternatively, when predModeIntra is ANGULAR_MODE, which is a directional mode, an additional prediction block (PRD_BLK_plus_one) may be configured using ANGULAR_MODE, and another additional prediction block (PRD_BLK_minus_one) may be configured by a weighted sum of PRD_BLK_best and PRD_BLK_plus_one.

A plurality of residual blocks may be obtained by using the current block and at least one of the plurality of configured prediction blocks. For example, residual blocks between prediction blocks constructed using all directional/non-directional modes and the current block may be configured. For example, N+1 prediction blocks configured using predModeIntra and N intra prediction modes adjacent to predModeIntra based on angle or intra prediction mode and residual blocks between the current block may be configured. In this case, N may be a positive integer of 1 or more. For example, as shown in FIG. 14 , when N=2, three residual blocks may be configured as follows.

For example, the residual block RES_BLK_best between the current block and PRD_BLK_best may be obtained. For example, the residual block RES_BLK_plusone between the current block and PRD_BLK_plus_one may be obtained. For example, a differential block RES_BLK_minusone between the current block and PRD_BLK_minus_one may be obtained.

For example, after configuring N additional prediction blocks using N intra-picture modes, and configuring M additional prediction blocks by combining the N prediction blocks configured (provided that M and N are positive integers), this It is possible to configure residual blocks between the prediction blocks and the current block.

A process of obtaining an optimal IDV (Intra Displacement Vector) for all samples within a search range may be performed. In this case, the IDV may be defined as a vector (x, y) from the upper-left sample position of the current block to the sample position within the search range, as shown in FIG. 14 .

For each IDV, a restoration block REC_BLK having the same size as the current block can be configured by setting the sample position indicated by the IDV to (0,0).

One or more residual signal blocks RES_BLK_IDV with respect to the reconstruction block REC_BLK configured at the position indicated by the IDV may be configured by using at least one of PRD_BLK_best and the additionally configured prediction blocks.

For example, when using N additional prediction blocks, N+1 residual signal blocks may be constructed using Equation 6 below for the reconstruction block REC_BLK constructed at the position indicated by IDV.

For example, when two additional prediction blocks are used as shown in FIG. 14 , three residual signal blocks may be constructed using Equation 7 below for the reconstruction block REC_BLK constructed at the position indicated by IDV.

As many as the number of prediction blocks applied to the reconstructed blocks in the search region at the position indicated by each IDV, a second order residual block may be configured.

15 is a diagram for explaining prediction of a residual signal using a secondary residual signal block.

As shown in FIG. 15 , the secondary residual signal block RES_BLK_SEC may be obtained through the difference between RES_BLK_'MODE' and RES_BLK_IDV_'MODE'. In this case, 'MODE' may be a prediction mode within a specific screen.

For example, when N prediction blocks are applied to the reconstructed block, N secondary residual signal blocks for the reconstructed block RES_BLK may be configured using Equation 8 below.

For example, as shown in FIG. 15 , when a prediction mode generated using predModeIntra and two additional prediction blocks are used, three secondary residual signal blocks are configured for the reconstruction block REC_BLK using Equation 9 below. can

In the reconstruction block at the position indicated by each IDV in the search region, the cost in the residual signal block and RES_BLK_best in which the cost function value according to rate-distortion optimization among the secondary residual signal blocks (RES_BLK_SEC) is minimized By comparing the function values, it is possible to determine whether to perform residual signal prediction. Whether to perform residual signal prediction may be indicated using, for example, an indicator SRP_flag (Second order Residual Prediction). For example, when residual signal prediction is performed, a first value may be allocated to SRP_flag, and a second value may be allocated if not performed. In this case, the first value may be 1 and the second value may be 0.

For example, when a minimum cost function value among the secondary residual signal blocks is smaller than a cost function value generated in RES_BLK_best, a first value may be assigned to SRP_flag. In addition, at least one or more of SRP_flag, IDV, an intra prediction mode used for generating a secondary residual signal block having a minimum cost function value, and a secondary residual signal of RES_BLK_SEC may be encoded or decoded in or from the bitstream. have.

For example, when the minimum cost function value among the secondary residual signal blocks is greater than or equal to the cost function value generated in RES_BLK_best, the second value may be assigned to SRP_flag. In addition, at least one or more of the residual signals of SRP_flag, predModeIntra, and RES_BLK_best may be encoded or decoded in or from the bitstream.

All IDVs pointing to the secondary residual signal block having a cost function smaller than the cost function value of RES_BLK_best may be determined while repeating the above process for all IDVs pointing to all samples in the search region. An IDV having the smallest cost function value among all the determined IDVs may be finally selected.

16 is a diagram for explaining an embodiment of residual signal prediction.

CUR_BLK represents a current block to be encoded/decoded. RES_BLK may be a first residual signal and indicates a residual signal block between the prediction block for the current block and CUR_BLK. The prediction block may be any one of a plurality of prediction blocks configured in an encoder/decoder for the current block.

IDV_REC_BLK indicates a recovery block constructed from IDV. RES_BLK_IDV indicates a residual signal block between the prediction block for the current block and IDV_REC_BLK. The prediction block may be any one of a plurality of prediction blocks configured in an encoder/decoder for the current block.

RES_BLK_SEC represents the secondary residual signal block between RES_BLK and RES_BLK_IDV.

In FIG. 16 , when the cost function value of RES_BLK_SEC is smaller than the cost function value of RES_BLK, a first value may be assigned to SRP_flag. In addition, at least one or more of SRP_flag, IDV, an intra prediction mode used for generating a secondary residual signal block having a minimum cost function value, and a secondary residual signal of RES_BLK_SEC may be encoded or decoded in or from the bitstream. have. The first value may be 0 or 1.

In FIG. 16 , when the cost function value of RES_BLK_SEC is greater than or equal to the cost function value of RES_BLK, a second value may be assigned to SRP_flag. In addition, at least one or more of the primary residual signals of SRP_flag, predModeIntra, and RES_BLK may be encoded or decoded in or from the bitstream. The second value may be 0 or 1.

The residual signal of the current block may be derived using at least one of the first residual signal and the second residual signal. The neighboring block IDV_REC_BLK may be a block indicated by the above-described IDV or may be a block adjacent to the current block (eg, a previously reconstructed block of the current block such as the left side, the top, etc.). The IDV may be coded as it is, or it may be coded by differential coding with the IDV of another block in the current picture. The RES_BLK_IDV may be derived by subtracting a predetermined prediction block from the reconstructed neighboring block. In this case, the intra prediction mode for generating the prediction block may be the neighboring block IDV_REC_BLK or the intra prediction mode of the current block, or may be a mode pre-promised to the encoder/decoder. Alternatively, the predetermined prediction block may be set to be the same as the prediction block for the current block. Alternatively, an upper block including the current block may be defined, and a residual signal shared by blocks belonging to the corresponding upper block may be defined as the second residual signal. The residual prediction technique based on the above-described second residual signal may be selectively performed based on a predetermined flag SRP_flag. The flag may be signaled from at least one of a sequence, a picture, a slice, and a block unit. Alternatively, in certain cases, the flag may be derived as a fixed value pre-promised to the encoder/decoder according to the size, shape, and/or depth of the current block.

An indicator (flag, flag) indicating whether residual signal prediction is performed in the current block may be encoded/decoded. For example, the indicator may be SRP_flag, and may be encoded/decoded for each unit of at least one of a current block or a sub-block.

At least one of IDV, the intra prediction mode (mode_x in FIG. 16, mode_x in FIG. 16) selected in the residual signal prediction of the current block, and other encoding parameter information, which is information necessary for prediction of the residual signal, may be encoded or decoded in or from the bitstream. have.

IDV information of the current block may be prediction encoded/decoded using the IDV of an adjacent block. For example, it is possible to encode/decode the difference value between the minimum value, the maximum value, the median value, the average value, the mode, or the weighted sum of IDVs of adjacent blocks and the IDV of the current block.

Alternatively, when at least one of the IDVs of the adjacent block is the same as the IDV of the current block, the encoder may construct and use an IDV list using the IDVs of the adjacent block according to a predefined method. The encoder may include, as IDV information of the current block, information indicating that at least one of the IDVs of the adjacent block is the same as the IDV of the current block (eg, a flag) and/or information indicating the same IDV in the IDV list ( For example, index) may be encoded. When the flag information indicates that at least one of the IDVs of the adjacent block is the same as the IDV of the current block, the decoder may construct the IDV list according to the predefined method. The decoder may derive the IDV of the current block by using the configured IDV list and the index information.

17 is a diagram for explaining an embodiment in which an encoder performs residual signal prediction.

Intra prediction is performed on the current block (S6201), and an optimal intra prediction mode (predModeIntra) may be determined (S6202). In operation S6202, a prediction block PRD_BLK_best using the optimal intra prediction mode may be generated. A residual block RES_BLK_bset between the prediction block PRD_BLK_best and the current block generated using predModeIntra may be obtained (S6203).

Based on the predModeIntra determined in step S6202, N additional intra prediction modes may be determined (S6204). In operation S6205, N+1 prediction blocks PRD_BLK_'mode' may be generated from N+1 intra prediction modes including predModeIntra and N additional intra prediction modes. In operation S6206, N+1 residual blocks RES_BLK_'mode' may be obtained using the current block and the N+1 prediction blocks PRD_BLK_'mode'.

In step S6207, it is determined by moving the IDV within a search range using a pixel unit search or a specific search method. A recovery block REC_BLK_IDV may be obtained from the determined IDV position (S6208). In operation S6209, N+1 IDV residual blocks RES_BLK_IDV_'mode' may be obtained using REC_BLK_IDV and the N+1 prediction blocks PRD_BLK_'mode'.

In operation S6210, N+1 secondary residual blocks RES_BLK_SEC_'mode' may be obtained using RES_BLK_'mode' and the corresponding RES_BLK_IDV_'mode'.

In step S6211, each of RES_BLK_SEC_'mode' and the RD cost of RES_BLK_best may be compared. When the RD cost of at least one RES_BLK_SEC_'mode' is smaller than the RD cost of RES_BLK_best (Yes in S6211), the process may move to step S6212. If not (No in S6211), the process may move to step S6213.

In step S6212, a first value (eg, 1) is assigned to SRP_flag, and the optimal cost may be determined as the RD cost of the at least one RES_BLK_SEC_'mode'.

In step S6213, it may be determined whether the current IDV is the last IDV within the search range. If the current IDV is not the last IDV (N0 in S6213), the flow moves to step S6207, and the above operation for the next IDV may be repeated. If the current IDV is the last IDV (Yes in S6213), the process may move to step S6214.

In step S6214, it may be determined whether the SRP_flag is a first value (eg, 1). If SRP_flag is the first value (Yes in S6214), the process may go to step S6215. If SRP_flag is not the first value (No in S6214), the process may move to step S6216.

In step S6215, among the secondary residual signals of SRP_flag, IDV, and the intra prediction mode ('mode' used in PRED_BLK_'mode') used for generating the secondary residual signal block having the minimum cost function value, RES_BLK_SEC_'mode' At least one or more is determined as an encoding target, and may be encoded in step S6217.

In operation S6216, at least one of SRP_flag, predModeIntra, and a primary residual signal of RES_BLK (eg, RES_BLK_best) is determined to be an encoding target, and may be encoded in operation S6217.

When the IDV is not signaled, the decoder may derive the IDV by performing the same search process performed by the encoder.

18 is a diagram for explaining an embodiment in which a decoder performs residual signal prediction.

In step S6301, related information included in the bitstream may be decoded.

When SRP_flag is not the first value (eg, 1) (No in S6302), step S6303 may be performed.

In operation S6303, a prediction block PRD_BLK_best corresponding to predModeIntra may be generated. Also, the residual block RES_BLK_best may be decoded.

In operation S6304, a reconstructed block may be generated using PRD_BLK_best and RES_BLK_best.

When SRP_flag is the first value (eg, 1) (Yes in S6302), steps S6305, S6306, and S6307 may be performed.

In step S6305, the secondary residual block RES_BLK_SEC_'mode' may be decoded.

In operation S6306, a recovery block REC_BLK_IDV corresponding to the decoded IDV may be generated.

In operation S6307, a prediction block PRD_BLK_'mode' corresponding to the decoded 'mode' may be generated.

In operation S6308, an IDV residual block RES_BLK_IDV_'mode' may be generated using the generated REC_BLK_IDV and PRD_BLK_'mode'.

In operation S6309, a residual block RES_BLK may be generated using the generated RES_BLK_SEC_'mode' and RES_BLK_IDV_'mode'.

In step S6310, a reconstructed block may be generated using the generated RES_BLK and PRD_BLK_'mode'.

As described above, when the IDV is not signaled, the decoder may derive the IDV by performing the same search process performed by the encoder.

The in-screen/decoding process may be performed for each of the luminance and chrominance signals. For example, in the intra/decoding process, at least one method of inducing an intra prediction mode, dividing a block, configuring a reference sample, and performing intra prediction may be differently applied to the luminance signal and the chrominance signal.

The same in-screen/decoding process for the luminance and chrominance signals may be performed. For example, at least one of inducing an intra prediction mode, dividing a block, composing a reference sample, and performing intra prediction may be equally applied to the color difference signal during the intra/decoding process applied to the luminance signal.

The above methods can be performed by the encoder and the decoder in the same way. For example, in the intra/decoding process, at least one method of inducing an intra prediction mode, dividing a block, constructing a reference sample, and performing intra prediction may be equally applied to the encoder and the decoder. Also, the order of applying the methods may be different in the encoder and the decoder. For example, in performing intra/decoding of the current block, the encoder may configure a reference sample and then perform one or more intra prediction to encode the determined intra prediction mode.

The above embodiments of the present invention may be applied according to the size of at least one of a coding block, a prediction block, a block, and a unit. Here, the size may be defined as a minimum size and/or a maximum size to which the embodiments are applied, or may be defined as a fixed size to which the embodiments are applied. Also, in the above embodiments, the first embodiment may be applied to the first size, and the second embodiment may be applied to the second size. That is, the regular embodiments may be complexly applied according to the size. In addition, the above embodiments of the present invention can be applied only when the minimum size or more and the maximum size or less. That is, the above embodiments can be applied only when the block size is included within a certain range.

For example, the above embodiments can be applied only when the size of the encoding/decoding target block is 8x8 or more. For example, the above embodiments can be applied only when the size of the encoding/decoding target block is 16x16 or more. For example, the above embodiments can be applied only when the size of the encoding/decoding target block is 32x32 or more. For example, the above embodiments may be applied only when the size of the encoding/decoding target block is 64x64 or more. For example, the above embodiments can be applied only when the size of the encoding/decoding target block is 128x128 or more. For example, the above embodiments can be applied only when the size of the encoding/decoding target block is 4x4. For example, the above embodiments may be applied only when the size of the encoding/decoding target block is 8x8 or less. For example, the above embodiments may be applied only when the size of the encoding/decoding target block is 16x16 or less. For example, the above embodiments can be applied only when the size of the encoding/decoding target block is 8x8 or more and 16x16 or less. For example, the above embodiments may be applied only when the size of the encoding/decoding target block is 16x16 or more and 64x64 or less.

The above embodiments of the present invention may be applied according to a temporal layer. A separate identifier is signaled to identify a temporal layer to which the embodiments are applicable, and the embodiments may be applied to a temporal layer specified by the corresponding identifier. The identifier herein may be defined as a minimum layer and/or a maximum layer to which the embodiment is applicable, or may be defined as indicating a specific layer to which the embodiment is applied.

For example, the above embodiments may be applied only when the temporal layer of the current image is the lowest layer. For example, the above embodiments may be applied only when the temporal layer identifier of the current image is 0. For example, the above embodiments may be applied only when the temporal layer identifier of the current image is 1 or more. For example, the above embodiments may be applied only when the temporal layer of the current image is the highest layer.

As in the above embodiment of the present invention, the reference picture set used in the process of reference picture list construction and reference picture list modification is one of L0, L1, L2, and L3. At least one reference image list may be used.

When calculating boundary strength in a deblocking filter according to the embodiment of the present invention, one or more and up to N motion vectors of a block to be encoded/decoded may be used. Here, N represents a positive integer of 1 or more, and may be 2, 3, 4, or the like.

When predicting a motion vector, the motion vector is 16-pel unit, 8-pel unit, 4-pel unit, integer-pel unit, 1/2 -pixel (1/2-pel) unit, 1/4-pixel (1/4-pel) unit, 1/8-pixel (1/8-pel) unit, 1/16-pixel (1/16-pel) unit ) unit, 1/32-pixel (1/32-pel) unit, and 1/64-pixel (1/64-pel) unit, the above embodiments of the present invention can also be applied. Also, when performing motion vector prediction, a motion vector may be selectively used for each pixel.

A slice type to which the embodiments of the present invention are applied is defined, and the embodiments of the present invention can be applied according to the slice type.

For example, when the slice type is T (Tri-predictive)-slice, a prediction block is generated using at least three or more motion vectors, and a weighted sum of the at least three or more prediction blocks is calculated to obtain an encoding/decoding target block. can be used as the final prediction block of For example, when the slice type is Q (Quad-predictive)-slice, a prediction block is generated using at least four or more motion vectors, and a weighted sum of at least four or more prediction blocks is calculated to obtain an encoding/decoding target block. can be used as the final prediction block of

The above embodiments of the present invention can be applied to inter prediction and motion compensation methods using motion vector prediction, as well as inter prediction and motion compensation methods using skip mode and merge mode.

The shape of the block to which the embodiments of the present invention are applied may have a square shape or a non-square shape.

In the above-described embodiments, the methods are described on the basis of a flowchart as a series of steps or units, but the present invention is not limited to the order of steps, and some steps may occur in a different order or at the same time as other steps as described above. can In addition, those of ordinary skill in the art will recognize that the steps shown in the flowchart are not exclusive, other steps may be included, or that one or more steps of the flowchart may be deleted without affecting the scope of the present invention. you will understand

The above-described embodiments include examples of various aspects. It is not possible to describe every possible combination for representing the various aspects, but one of ordinary skill in the art will recognize that other combinations are possible. Accordingly, it is intended that the present invention cover all other substitutions, modifications and variations falling within the scope of the following claims.

The embodiments according to the present invention described above may be implemented in the form of program instructions that can be executed through various computer components and recorded in a computer-readable recording medium. The computer-readable recording medium may include program instructions, data files, data structures, etc. alone or in combination. The program instructions recorded on the computer-readable recording medium may be specially designed and configured for the present invention, or may be known and available to those skilled in the computer software field. Examples of the computer-readable recording medium include a hard disk, a magnetic medium such as a floppy disk and a magnetic tape, an optical recording medium such as a CD-ROM and DVD, and a magneto-optical medium such as a floppy disk. media), and hardware devices specially configured to store and execute program instructions such as ROM, RAM, flash memory, and the like. 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 device may be configured to operate as one or more software modules to perform processing according to the present invention, and vice versa.

In the above, the present invention has been described with specific matters such as specific components and limited embodiments and drawings, but these are provided to help a more general understanding of the present invention, and the present invention is not limited to the above embodiments. , those of ordinary skill in the art to which the present invention pertains can devise various modifications and variations from these descriptions.

Therefore, the spirit of the present invention should not be limited to the above-described embodiments, and not only the claims described below, but also all modifications equivalently or equivalently to the claims described below belong to the scope of the spirit of the present invention. will do it

Claims (20)

obtaining a first MPM flag indicating whether a current block is predicted according to an intra prediction mode included in a first MPM list;
When the first MPM flag indicates that the current block is not predicted according to the intra prediction mode included in the first MPM list, whether the current block is predicted according to the intra prediction mode included in the second MPM list obtaining a second MPM flag indicating
When the second MPM flag indicates that the current block is predicted according to the intra prediction mode included in the second MPM list, the intra prediction mode of the current block among the intra prediction modes included in the second MPM list is selected. obtaining an MPM index indicating, and deriving an intra prediction mode of the current block from the second MPM list according to the MPM index;
deriving reference samples of intra prediction for the current block from a plurality of reference sample lines;
generating a prediction block by performing intra prediction on the current block based on the intra prediction mode and the reference sample; and
reconstructing the current block based on the prediction block of the current block;
The intra prediction mode of the second MPM list is determined according to the maximum and minimum values of the intra prediction mode of the left neighboring block of the current block and the intra prediction mode of the upper neighboring block,
Restoring the current block comprises:
obtaining residual block information indicating whether residual block prediction of the current block is performed;
obtaining an intra displacement vector used for the residual block prediction when the residual block information indicates that residual block prediction of the current block is performed;
obtaining a second residual block of the current block;
obtaining a first residual block of the current block from the second residual block by performing residual block prediction based on the intra-picture displacement vector; and
and reconstructing the current block based on the first residual block of the current block and the prediction block of the current block. delete delete According to claim 1,
If the current block is a color difference block,
The intra prediction mode of the current block is derived using the intra prediction mode of the luminance-corresponding block,
The luminance-corresponding block is determined based on the size of the luminance block corresponding to the current block. According to claim 1,
A reference sample line for deriving the reference sample from among the plurality of reference sample lines is determined based on information reconstructed from a bitstream. According to claim 1,
Among the plurality of reference sample lines, a reference sample line for deriving the reference sample is determined based on whether an upper boundary of the current block corresponds to a boundary of an encoding tree block. According to claim 1,
When the current block is a rectangle and the intra prediction mode is a DC mode,
The intra prediction of the current block is performed using an average value of reference samples adjacent to a longer side of a horizontal or vertical side of the current block. delete delete determining an intra prediction mode of the current block;
determining, according to the intra prediction mode of the current block, a first MPM flag indicating whether the current block is predicted according to the intra prediction mode included in a first MPM list;
When the first MPM flag indicates that the current block is not predicted according to the intra prediction mode included in the first MPM list, the current block is added to the second MPM list according to the intra prediction mode of the current block. determining a second MPM flag indicating whether prediction is performed according to an included intra prediction mode;
When the second MPM flag indicates that the current block is predicted according to the intra prediction mode included in the second MPM list, intra prediction included in the second MPM list according to the intra prediction mode of the current block determining an MPM index indicating an intra prediction mode of the current block among modes;
deriving reference samples of intra prediction for the current block from a plurality of reference sample lines;
generating a prediction block by performing intra prediction on the current block based on the intra prediction mode and the reference sample; and
encoding the current block based on the prediction block of the current block;
The intra prediction mode of the second MPM list is determined according to the maximum and minimum values of the intra prediction mode of the left neighboring block of the current block and the intra prediction mode of the upper neighboring block,
The encoding of the current block comprises:
encoding residual block information indicating whether residual block prediction of the current block is performed;
encoding an intra-displacement vector used for the residual block prediction when the residual block information indicates that the residual block prediction of the current block is performed;
obtaining a first residual block of the current block based on the prediction block of the current block;
obtaining a second residual block of the current block from the first residual block by performing residual block prediction based on the intra-picture displacement vector; and
and encoding the second residual block of the current block. delete delete 11. The method of claim 10,
If the current block is a color difference block,
The intra prediction mode of the current block is encoded using the intra prediction mode of the luminance-corresponding block,
The luminance-corresponding block is determined based on the size of the luminance block corresponding to the current block. 11. The method of claim 10,
Information for determining a reference sample line for deriving the reference sample from among the plurality of reference sample lines is encoded in a bitstream. 11. The method of claim 10,
Among the plurality of reference sample lines, a reference sample line for deriving the reference sample is determined based on whether an upper boundary of the current block corresponds to a boundary of an encoding tree block. 11. The method of claim 10,
When the current block is a rectangle and the intra prediction mode is a DC mode,
The intra prediction of the current block is performed using an average value of reference samples adjacent to a longer side of a horizontal or vertical side of the current block. delete delete delete A computer-readable recording medium storing a bitstream encoded by an image encoding method, comprising:
The video encoding method comprises:
determining an intra prediction mode of the current block;
determining, according to the intra prediction mode of the current block, a first MPM flag indicating whether the current block is predicted according to the intra prediction mode included in a first MPM list;
When the first MPM flag indicates that the current block is not predicted according to the intra prediction mode included in the first MPM list, the current block is added to the second MPM list according to the intra prediction mode of the current block. determining a second MPM flag indicating whether prediction is performed according to an included intra prediction mode;
When the second MPM flag indicates that the current block is predicted according to the intra prediction mode included in the second MPM list, intra prediction included in the second MPM list according to the intra prediction mode of the current block determining an MPM index indicating an intra prediction mode of the current block among modes;
deriving reference samples of intra prediction for the current block from a plurality of reference sample lines;
generating a prediction block by performing intra prediction on the current block based on the intra prediction mode and the reference sample; and
encoding the current block based on the prediction block of the current block;
The intra prediction mode of the second MPM list is determined according to the maximum and minimum values of the intra prediction mode of the left neighboring block of the current block and the intra prediction mode of the upper neighboring block,
The encoding of the current block comprises:
encoding residual block information indicating whether residual block prediction of the current block is performed;
encoding an intra displacement vector used for the residual block prediction when the residual block information indicates that the residual block prediction of the current block is performed;
obtaining a first residual block of the current block based on the prediction block of the current block;
obtaining a second residual block of the current block from the first residual block by performing residual block prediction based on the intra-picture displacement vector; and
and encoding the second residual block of the current block.

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