RU2788967C2 - Method and device for video encoding and method and device for video decoding - Google Patents

Abstract

FIELD: digital video technologies.

SUBSTANCE: invention relates to the field of digital video compression and decompression technologies, and more particularly to encoding and decoding the intra-prediction mode of a current block using intra-prediction mode information of an adjacent block. A video encoding method and apparatus is provided that determines whether to use a Most Likely Mode List (MPM), based on encoding information of a current block, obtains, from a bitstream, intra-prediction mode index information indicating one of the candidate intra-prediction modes, included in the MPM list, and determining the intra prediction mode of the current block using the obtained intra prediction mode index information, wherein the list of intra prediction mode candidates is obtained by using at least one of the intra prediction mode of the left block adjacent to the left side the current block, and the intra-prediction mode of the top block adjacent to the top side of the current block.

EFFECT: reducing the amount of information required to represent intra-prediction modes.

1 cl, 39 dwg

Description

Technical field

[0001] The disclosure relates to a video decoding method and apparatus and a video encoding method and apparatus, and more specifically to encoding and decoding the intra prediction mode of a current block using intra prediction mode information of an adjacent block.

Prior Art

[0002] The image data is encoded with a predetermined codec conforming to a data compression standard such as the Moving Picture Experts Group (MPEG) standard, and then stored in a recording medium or transmitted via a communication channel in the form of a bitstream. Recently, due to the development of wired/wireless communication infrastructures, including the 5th generation (5G), there is an increasing need for technology to efficiently compress next generation media such as 4K/8K ultra-high-definition (UHD) video, 360-degree video, virtual reality (VR) images and the like, in addition to existing image media.

Description of Embodiments

Technical problem

[0003] As the number of intra prediction modes to be used in intra prediction increases, the amount of information required to represent the intra prediction modes may increase.

Solution

[0004] According to various embodiments, candidate intra prediction modes having a high probability of being the intra prediction mode of the current block are determined using prediction mode information of adjacent blocks of the current block, and the intra prediction mode of the current block is encoded and decoded using candidate intra-prediction modes.

Beneficial disclosure results

[0005] According to various embodiments, the number of bits required to represent the intra prediction mode information of the current block can be reduced.

Brief description of the drawings

[0006] FIG. 1A is a block diagram of an image decoding apparatus, in accordance with various embodiments.

[0007] FIG. 1B illustrates a flowchart of an image decoding method according to an embodiment.

[0008] FIG. 1C illustrates a flowchart of an image decoding method according to another embodiment.

[0009] FIG. 1D is a block diagram of an image decoder according to various embodiments.

[0010] FIG. 1E is a block diagram of an image decoding apparatus according to various embodiments.

[0011] FIG. 2A is a block diagram of an image encoding apparatus, in accordance with various embodiments.

[0012] FIG. 2B illustrates a flowchart of an image encoding method according to an embodiment.

[0013] FIG. 2C illustrates a flowchart of an image encoding method according to another embodiment.

[0014] FIG. 2D is a block diagram of an image encoder in accordance with various embodiments.

[0015] FIG. 2E is a block diagram of an image encoding apparatus according to an embodiment.

[0016] FIG. 3 illustrates a process performed by an image decoding apparatus to determine at least one coding unit by dividing the current coding unit, according to an embodiment.

[0017] FIG. 4 illustrates a process performed by an image decoding apparatus to determine at least one coding unit by dividing a non-square coding unit, according to an embodiment.

[0018] FIG. 5 illustrates a process of splitting a coding unit based on at least one of the block shape information and split shape mode information performed by the image decoding apparatus, according to an embodiment.

[0019] FIG. 6 illustrates a process performed by an image decoding apparatus for determining a predetermined coding unit from an odd number of coding units, according to an embodiment.

[0020] FIG. 7 illustrates a processing order of a plurality of coding units when an image decoding apparatus determines a plurality of coding units by dividing the current coding unit, according to an embodiment.

[0021] FIG. 8 illustrates a process performed by the image decoding apparatus for determining that the current coding unit is to be divided into an odd number of coding units when the coding units cannot be processed in a predetermined order, according to an embodiment.

[0022] FIG. 9 illustrates a process performed by an image decoding apparatus to determine at least one coding unit by dividing the first coding unit, according to an embodiment.

[0023] FIG. 10 illustrates that the shape into which the second coding unit can be divided is limited when the second coding unit having a non-square shape, which is determined as the image decoding apparatus divides the first coding unit, satisfies a predetermined condition, according to an embodiment.

[0024] FIG. 11 illustrates a process performed by an image decoding apparatus of splitting a square coding unit when split mode information indicates that a square coding unit is not to be divided into four square coding units, according to an embodiment.

[0025] FIG. 12 illustrates that the processing order between multiple coding units may change depending on the coding unit splitting process, according to an embodiment.

[0026] FIG. 13 illustrates a process for determining a coding unit depth as the shape and size of a coding unit change when a coding unit is recursively divided so that a plurality of coding units is determined, according to an embodiment.

[0027] FIG. 14 illustrates depths that can be determined based on shapes and sizes of coding units, and part indices (PIDs) that serve to distinguish coding units, according to an embodiment.

[0028] FIG. 15 illustrates that a plurality of coding units are determined based on a plurality of predefined data units included in a picture, according to an embodiment.

[0029] FIG. 16 illustrates a processing unit serving as a criterion for determining a determination order of coding reference units included in a picture, according to an embodiment.

[0030] FIG. 17 illustrates intra prediction modes according to an embodiment.

[0031] FIG. 18 illustrates intra prediction modes according to another embodiment.

[0032] FIG. 19 is a diagram for describing intra prediction modes to be applied to a non-square shape, according to various embodiments.

[0033] FIG. 20 is a reference diagram for describing a process of obtaining a Most Likely Mode List (MPM) using adjacent block prediction mode information, in accordance with various embodiments.

[0034] FIG. 21 is a flowchart of an MPM list generation process according to an embodiment.

[0035] FIG. 22 is a reference sample diagram according to the embodiment.

[0036] FIG. 23 is a reference diagram for describing a method for representing the intra prediction mode as a vector, according to another embodiment.

[0037] FIG. 24A-24C are reference diagrams for describing the priority order of intra prediction modes of adjacent blocks included in the MPM list, given the sizes of the current block and adjacent blocks.

[0038] FIG. 25 is a diagram illustrating adjacent blocks of the current block that are used in the MPM list, according to another embodiment.

[0039] FIG. 26 is a reference diagram illustrating an MPM list generation scheme in parallel processing, according to an embodiment.

[0040] FIG. 27 illustrates a lookup table showing mapping relationships between indices (predModeIntra) of intra prediction modes and angle parameters (IntraPredAngle) according to intra prediction modes, according to an embodiment.

[0041] FIG. 28 illustrates a lookup table showing mapping relationships between indices (predModeIntra) of intra prediction modes and angle parameters (IntraPredAngle) according to intra prediction modes, according to another embodiment.

[0042] FIG. 29 is a reference diagram for describing IntraPredAngle angular parameters related to intra prediction mode directions according to embodiments.

Best Mode for Carrying Out the Invention

[0043] According to an embodiment, a video decoding method includes: determining, based on the encoding information of the current block, whether the intra prediction mode of the current block is to be determined from an intra prediction mode candidate list obtained using a plurality of prediction mode information pieces adjacent blocks adjacent to the current block; when the intra prediction mode of the current block is to be determined from the intra prediction mode candidate list, obtaining, from the bitstream, intra prediction mode index information indicating one of the intra prediction modes of candidates included in the intra prediction mode candidate list; determining an intra prediction mode of the current block using the obtained intra prediction mode index information; and performing intra-prediction on the current block using the intra-prediction mode of the current block.

[0044] According to an embodiment, the encoding information may include reference sample information to be used in intra-prediction regarding the current block, and sub-split information indicating whether the current block is to be divided into sub-splits when the reference sample information sample indicates that an adjacent pixel that is not directly adjacent to the current block is to be used as a reference sample of the current block, or the sub-slice information indicates that the current block is to be sub-sliced, the intra-prediction mode of the current block is determined from of the intra-prediction mode candidate list, when the reference sample information indicates that an adjacent pixel that is directly adjacent to the current block is to be used as the reference sample of the current block, and the sub-division information indicates that the current block is not to be divided into sub- splitting, candidate list flag information re The intra prediction mode candidate list is obtained from the bitstream, wherein the intra prediction mode candidate list flag information indicates whether the intra prediction mode of the current block is to be determined from the intra prediction mode candidate list obtained using a plurality of pieces of adjacent block prediction mode information adjacent to the current block.

[0045] According to an embodiment, obtaining intra-prediction mode index information from the bitstream may include obtaining non-angular intra-prediction mode information indicating whether the intra-prediction mode of the current block is a particular non-angular intra-prediction mode. prediction, and when the non-angular intra prediction mode information does not indicate a specific non-angular intra prediction mode, obtaining intra prediction mode index information from the bitstream.

[0046] According to an embodiment, the specific non-angular intra-prediction mode may be one of DC mode and planar mode.

[0047] According to an embodiment, when the non-angular intra prediction mode information indicates a specific non-angular intra prediction mode, the intra prediction mode of the current block may be determined as the specific non-angular intra prediction mode.

[0048] According to an embodiment, when the intra prediction mode of the current block is not determined from the intra prediction mode candidate list, the intra prediction mode information of the current block can be obtained from the bitstream.

[0049] According to an embodiment, the intra prediction mode candidate list may include a predetermined number of candidate intra prediction modes determined using an adjacent block prediction mode adjacent on the right side of the current block and an adjacent block prediction mode adjacent on top side of the current block.

[0050] According to an embodiment, a video decoding apparatus includes: a memory and at least one processor coupled to the memory and configured to

[0051] determining, based on the coding information of the current block, whether the intra prediction mode of the current block is to be determined from an intra prediction mode candidate list obtained using a plurality of pieces of adjacent block prediction mode information adjacent to the current block; when the intra prediction mode of the current block is to be determined from the intra prediction mode candidate list, obtain, from the bitstream, intra prediction mode index information indicating one of the intra prediction modes of candidates included in the intra prediction mode candidate list; determine the intra prediction mode of the current block using the obtained intra prediction mode index information; and perform intra-prediction on the current block using the intra-prediction mode of the current block.

[0052] According to an embodiment, a video encoding method includes: determining an intra prediction mode of a current block; determining, based on the encoding information of the current block, whether the intra prediction mode of the current block is to be determined from an intra prediction mode candidate list obtained using a plurality of pieces of adjacent block prediction mode information adjacent to the current block; and when the intra prediction mode of the current block is to be determined from the intra prediction mode candidate list, generating a bitstream including intra prediction mode index information indicating one of the intra prediction modes of candidates included in the intra prediction mode candidate list.

Opening mode

[0053] The advantages and properties of the embodiments and methods for their implementation may become more clear with reference to the embodiments and the accompanying drawings. In this respect, the disclosure may take many forms and should not be construed as being limited to the embodiments set forth herein. On the contrary, these embodiments are provided such that the present disclosure will be thorough and complete, and will be fully consistent with the concept of the disclosure to those skilled in the art.

[0054] The terms used in the specification will be defined briefly and the embodiments will be described in detail.

[0055] All terms, including descriptive or technical terms, that are used in the specification should be understood to have meanings that are obvious to a person skilled in the art. However, the terms may have different meanings according to the intent of a person skilled in the art, previous occurrences, or the advent of new technologies. Also, some terms may be arbitrarily chosen by the applicant, in which case, the meanings of the chosen terms will be described in detail in the detailed description of the disclosure. Therefore, terms used in the disclosure should not be interpreted based on their names alone, but should be defined based on the meaning of the terms, together with descriptions throughout the specification.

[0056] In the following specification, singular forms include plural forms unless the context clearly indicates otherwise.

[0057] When a part "includes" or "comprises" an element, unless specifically described to the contrary, the part may further include other elements without excluding other elements.

[0058] In the following descriptions, terms such as "module" indicate a software or hardware component, and "module" performs certain functions. However, the "module" is not limited to software or hardware. The "module" may be configured to reside in an available storage medium, or may be configured to use one or more processors. Thus, for example, the term "module" may refer to components such as software components, object-oriented software components, class components, and task components, and may include processes, functions, attributes, procedures, subroutines, software segments. code, drivers, firmware, microcode, circuits, data, databases, data structures, tables, arrays, or variables. The functionality provided by components and "modules" may be associated with a smaller number of components and "modules", or may be subdivided into additional components and "modules".

[0059] In accordance with an embodiment of the disclosure, a "module" may be implemented as a processor and memory. The term "processor" is to be interpreted broadly to include a general purpose processor, central processing unit (CPU), microprocessor, digital signal processor (DSP), controller, microcontroller, state machine, and the like. In some environments, "processor" may refer to an application specific integrated circuit (ASIC), a programmable logic device (PLD), a field-programmable gate array (FPGA), or the like. The term "processor" may refer to a combination of processing devices such as, for example, a combination of a DSP and a microprocessor, a combination of multiple microprocessors, a combination of one or more microprocessors in conjunction with a DSP core, or a combination of any other such configuration.

[0060] The term "memory" should be interpreted broadly to include any electronic component capable of storing electronic information. The term "memory" can refer to various types of processor-readable media such as random access memory (RAM), read only memory (ROM), non-volatile random access memory (NVRAM), programmable read only memory (PROM), erasable programmable read only memory ( EPROM), electrically erasable PROM (EEPROM), flash memory, magnetic or optical storage device, registers, and the like. When the processor can read information from the memory and/or write information to the memory, the memory must be in a state of electronic communication with the processor. The memory integrated into the processor is in electronic communication with the processor.

[0061] Further, the "image" may be a static image, such as a still image of a video, or may be a dynamic image, such as a moving image, that is, the video itself.

[0062] Hereinafter, "sample" refers to data assigned to a sampling position of an image, i.e., data to be processed. For example, the pixel values of an image in the spatial domain and the transform coefficients on the transform region may be samples. A unit including at least one such sample may be defined as a block.

[0063] Hereinafter, the disclosure will now be described more fully with reference to the accompanying drawings so that a person skilled in the art can perform the embodiments without any difficulty. In addition, parts that are not relevant to the description will be omitted from the drawings for a clear description of the disclosure.

[0064] Hereinafter, an image encoding apparatus and an image decoding apparatus, and an image encoding method and an image decoding method according to the embodiments will be described with reference to FIG. 1A-29. With reference to FIG. 3-16, a method for determining an image data unit according to the embodiment will be described, and with reference to FIG. 1A-2E and 17-29, methods for encoding and decoding the intra prediction mode will be described.

[0065] Next, a method and apparatus for encoding or decoding an image for adaptively performing intra prediction based on various forms of a coding unit, according to an embodiment of the disclosure, will now be described with reference to FIG. 1A-2E.

[0066] FIG. 1A is a block diagram of an image decoding apparatus, in accordance with various embodiments.

[0067] Image decoding apparatus 100 may include a receiver 110 and decoder 120. Receiver 110 and decoder 120 may include at least one processor. Also, receiver 110 and decoder 120 may include a memory storing instructions to be executed by at least one processor.

[0068] Receiver 110 may receive a bitstream. The bitstream includes image information encoded by the image encoding apparatus 150, which will be described later. Also, the bit stream may be transmitted from the image encoding device 150 . The image encoding device 150 and the image decoding device 100 may be wired or wirelessly connected, and the receiver 110 may receive the bitstream in a wired or wireless manner. The receiver 110 may receive a bit stream from a storage medium such as an optical media or a hard drive. Decoder 120 may reconstruct the image based on the information obtained from the received bitstream. Decoder 120 may obtain, from the bitstream, a syntax element for image reconstruction. Decoder 120 may reconstruct the image based on the syntax element.

[0069] The receiver 110 may obtain, from the bitstream, prediction mode information about the current block and intra prediction mode information about the current block.

[0070] The prediction mode information about the current block that is included in the bitstream may include information about a skip mode, an intra prediction mode, or an inter prediction mode. When the current block does not match the skip mode, which prediction mode from the intra-prediction mode or the inter-prediction mode was used to encode the current block can be signaled.

[0071] The intra prediction mode information about the current block may be information about the intra prediction mode to be applied to the current block, the intra prediction mode being one of a plurality of intra prediction modes. For example, the intra-prediction mode may be one of non-angular modes, including DC mode, planar mode, flat mode, and bilinear mode, and a plurality of angle modes having prediction directions. The angle modes may include a horizontal mode, a vertical mode, and a diagonal mode, and may also include modes having predetermined directions except for the horizontal direction, the vertical direction, and the diagonal direction. For example, the number of angle modes can be 65 or 33.

[0072] Decoder 120 may obtain a prediction block of the current block based on the prediction mode of the current block. The decoder 120 may obtain, from the bitstream, transform coefficient information about the current block, may perform inverse quantization and inverse transformation using the obtained transform coefficient information, and thus may obtain a residual block residual sample relative to the current block.

[0073] As will be described below, according to an embodiment, the decoder 120 determines, based on the coding information of the current block, whether the intra prediction mode of the current block is to be determined from the intra prediction mode candidate list obtained using the plurality of prediction mode information pieces adjacent blocks adjacent to the current block. When the intra prediction mode of the current block is to be determined from the intra prediction mode candidate list, the decoder 120 obtains, from the bitstream, intra prediction mode index information indicating one of the intra prediction modes of candidates included in the intra prediction mode candidate list, and determines the intra prediction mode of the current block using the obtained intra prediction mode index information. Thereafter, the decoder 120 performs intra prediction using the intra prediction mode of the current block. According to an embodiment, decoder 120 obtains non-angular intra prediction mode information indicating whether the intra prediction mode of the current block is a specific non-angular intra prediction mode. The particular non-angular intra-prediction mode may be one of the DC mode and the planar mode. When the non-angular intra prediction mode information indicates a specific non-angular intra prediction mode, the decoder 120 determines the intra prediction mode of the current block as the specific non-angular intra prediction mode, and when the non-angular intra prediction mode information does not indicate specific non-angular intra prediction mode, the decoder 120 obtains, from the bitstream, intra prediction mode index information indicating one in the intra prediction mode candidate list obtained based on the prediction mode information of an adjacent block adjacent to the current block. Thereafter, the decoder 120 may determine the intra prediction mode of the current block using the obtained intra prediction mode index (MPM idx) information, and may perform intra prediction on the current block using the intra prediction mode of the current block. Decoder 120 may reconstruct the current block based on the prediction block of the current block and the residual block of the current block. Decoder 120 may generate a reconstructed sample in the current block using a sample value for the prediction sample in the prediction block of the current block and a residual sample value in the residual block of the current block, and may generate a reconstructed block of the current block based on the reconstructed sample.

[0074] FIG. 1B illustrates a flowchart of an image decoding method according to an embodiment.

[0075] In operation 150, the decoder 120 determines, based on the encoding information of the current block, whether the intra prediction mode of the current block is to be determined from an intra prediction mode candidate list obtained using a plurality of pieces of adjacent block prediction mode information adjacent to the current block. .

[0076] In operation 151, when the intra prediction mode of the current block is to be determined from the list of intra prediction mode candidates, the decoder 120 obtains, from the bitstream, intra prediction mode index information indicating one of the intra prediction modes of the candidates included in an intra prediction mode candidate list, and in operation 152, the decoder 120 determines the intra prediction mode of the current block using the obtained intra prediction mode index information.

[0077] In operation 153, the decoder 120 performs intra prediction using the intra prediction mode of the current block.

[0078] FIG. 1C illustrates a flowchart of an image decoding method according to another embodiment.

[0079] In operation 160, decoder 120 obtains non-angular intra prediction mode information indicating whether the intra prediction mode of the current block is a specific non-angular intra prediction mode. The specific non-angular intra-prediction mode may be one of DC mode and planar mode.

[0080] In operation 161, the decoder 120 determines whether the non-angular intra-prediction mode information is a specific non-angular intra-prediction mode. As a result of determining in operation 161 when the non-angular intra prediction mode information indicates a specific non-angular intra prediction mode, in operation 162, the decoder 120 determines the intra prediction mode of the current block as the specific non-angular intra prediction mode, and when the non-angular intra prediction mode information does not indicate a specific non-angular intra prediction mode, in operation 163, the decoder 120 obtains, from the bitstream, intra prediction mode index information indicating such in the list of intra prediction mode candidates obtained based on prediction mode information of an adjacent block adjacent to the current block. In operation 164, the decoder 120 may determine the intra prediction mode of the current block using the obtained intra prediction mode index (MPM idx) information, and in operation 165, the decoder 120 may perform intra prediction on the current block using the intra prediction mode of the current block. block.

[0081] FIG. 1D is a block diagram of an image decoder 6000 in accordance with various embodiments.

[0082] An image decoder 6000 according to various embodiments performs operations necessary for the decoder 120 of the image decoding apparatus 100 to decode image data.

[0083] With reference to FIG. 1D, the entropy decoder 6150 parses, from the bitstream 6050, the encoded image data to be decoded and the encoding information necessary for decoding. The encoded image data is the quantized transform coefficient, and the dequantizer 6200 and the inverse transform 6250 recover the residual data from the quantized transform coefficient.

[0084] The intra predictor 6400 performs intra prediction on each of the blocks. As will be described below, according to an embodiment, the intra predictor 6400 determines, based on the coding information of the current block, whether the intra prediction mode of the current block is to be determined from an intra prediction mode candidate list obtained using a plurality of pieces of adjacent prediction mode information. blocks adjacent to the current block, and when the intra prediction mode of the current block is to be determined from the list of intra prediction mode candidates, the intra predictor 6400 obtains, from the bitstream, intra prediction mode index information indicating one of the intra prediction modes of candidates included in the intra prediction mode candidate list, and determines the intra prediction mode of the current block using the obtained intra prediction mode index information.

[0085] The inter-predictor 6350 performs inter-prediction on each block using the reference image obtained from the reconstructed picture buffer 6300. The spatial domain data for a block of the current image may be recovered by summing the residual data and the prediction data of each block, which are generated by the intra predictor 6400 or the inter predictor 6350, and the deblocking unit 6450 and the adaptive sample offset (SAO) execution unit 6500 may perform loop filtering. on the reconstructed spatial domain data so that a filtered reconstructed image can be output. The restored images stored in the restored picture buffer 6300 may be output as a reference image.

[0086] In order for the decoder 120 of the image decoding apparatus 100 to encode image data, the image decoder 6000 according to various embodiments may perform operations of each stage on each block.

[0087] FIG. 1E is a block diagram of an image decoding apparatus 100 according to the embodiment.

[0088] The image decoding apparatus 100 according to an embodiment may include a memory 130 and at least one processor 125 coupled to the memory 130. The operations of the image decoding apparatus 100 according to an embodiment may be performed by separate processors or may be performed by control central processor. Also, the memory 130 of the image decoding apparatus 100 may store data received from an external source and data generated by the processor. The processor 125 of the image decoding apparatus 100 can determine, based on the encoding information of the current block, whether the intra prediction mode of the current block is to be determined from an intra prediction mode candidate list obtained using a plurality of pieces of adjacent block prediction mode information adjacent to the current block, and when the intra prediction mode of the current block is to be determined from the intra prediction mode candidate list, the processor 125 may obtain, from the bitstream, intra prediction mode index information indicating one of the intra prediction modes of candidates included in the intra prediction mode candidate list , and may determine the intra prediction mode of the current block using the obtained intra prediction mode index information.

[0089] FIG. 2A is a block diagram of an image encoding apparatus, in accordance with various embodiments.

[0090] The image encoding device 150 according to various embodiments may include an encoder 155 and an output unit 160.

[0091] Encoder 155 and output module 160 may include at least one processor. Also, encoder 155 and output module 160 may include a memory storing instructions to be executed by at least one processor. Encoder 155 and output module 160 may be implemented as separate hardware components, or encoder 155 and output module 160 may be included in a single hardware component.

[0092] The encoder 155 determines the prediction mode of the current block by applying various prediction modes, including skip mode, intra-prediction mode, inter-prediction mode, or the like. When the current block does not match the skip mode, which prediction mode from the intra-prediction mode or the inter-prediction mode was used to encode the current block can be signalled.

[0093] Encoder 155 may obtain a prediction block of the current block based on the prediction mode of the current block, and then may encode a residual by transforming and quantizing the residual, which is a difference value between the current block and the prediction block. Encoder 155 may determine an intra prediction mode candidate to be applied to the current block using the width and height of the current block. Encoder 155 may encode information about the intra-prediction mode of the current block. The encoder 155 determines the intra-prediction mode in which the rate-distortion (RD) cost is optimal by applying the intra-prediction modes in accordance with various embodiments. When the prediction mode of the current block is finally determined to be the intra prediction mode, the encoder 155 may add, to the bitstream, a plurality of pieces of information about which prediction mode of skip mode, inter prediction mode, and intra prediction mode is used to predict the current block. , and intra-prediction mode information of the intra-predicted current block, and may transmit the bitstream to the image decoding apparatus 100 .

[0094] The output unit 160 may generate a bitstream including intra-prediction mode information of the current block and structure information to determine data units having hierarchically separated forms, and may output the bitstream.

[0095] FIG. 2B illustrates a flowchart of an image encoding method according to an embodiment.

[0096] In operation 250, the encoder 155 applies the intra-prediction modes available for the current block and determines the intra-prediction mode having the optimal RD cost.

[0097] In operation 251, the encoder 155 determines, based on the coding information of the current block, whether the intra prediction mode of the current block is to be determined from the list of intra prediction mode candidates obtained using a plurality of pieces of adjacent block prediction mode information adjacent to the current block .

[0098] In operation 252, when the intra prediction mode of the current block is to be determined from the list of intra prediction mode candidates, the encoder 155 generates a bitstream including intra prediction mode index information indicating one of the intra prediction modes of candidates included to the list of intra-prediction mode candidates.

[0099] FIG. 2C illustrates a flowchart of an image encoding method according to another embodiment.

[00100] In operation 271, the encoder 155 applies the intra-prediction modes available for the current block and determines the intra-prediction mode having the optimal RD cost.

[00101] In operation 272, the encoder 155 determines whether the intra-prediction mode of the current block is a particular non-angular intra-prediction mode. As a result of determining in operation 272 when the intra-prediction mode of the current block is a specific non-angular intra-prediction mode, in operation 273, the encoder 155 adds the specific non-angular intra-prediction mode information as the current block's intra-prediction mode information. to the bitstream. When the intra prediction mode of the current block is not a specific non-angular intra prediction mode, in operation 274, the encoder 155 sets an intra prediction mode candidate list (MPM list) based on the prediction mode information of an adjacent block adjacent to the current block, and in step 275, the encoder 155 generates a bitstream including intra prediction mode index (MPM idx) information indicating one in the intra prediction mode candidate list.

[00102] FIG. 2D is a block diagram of an image encoder in accordance with various embodiments.

[00103] An image encoder 7000 according to various embodiments performs operations necessary for the encoder 155 of the image encoding apparatus 150 to encode image data.

[00104] That is, the intra predictor 7200 performs intra prediction on each of the blocks of the current picture 7050, and the inter predictor 7150 performs inter prediction on each of the blocks using the current picture 7050 and the reference picture obtained from the reconstructed picture buffer 7100 .

[00105] The residual data is obtained by subtracting the prediction data from the block data to be encoded in the current picture 7050, wherein the prediction data is related to each block and output from the intra predictor 7200 or inter predictor 7150, and the transformer 7250 and quantizer 7300 may output the quantized the transformation coefficient of each block by performing transformation and quantization on the residual data.

[00106] The dequantizer 7450 and inverse transform 7500 can recover residual spatial domain data by performing inverse quantization and inverse transform on the quantized transform coefficient. The reconstructed residual spatial domain data may be added to the prediction data that is related to each block and output from the intra predictor 7200 or inter predictor 7150, and thus may be recovered as spatial domain data relative to the block of the current image 7050. Deblocking module 7550 and the SAO execution unit 7600 generates a filtered reconstructed image by performing contour filtering on the reconstructed spatial domain data. The generated reconstructed image is stored in the restored picture buffer 7100 . The reconstructed images stored in the reconstructed picture buffer 7100 may be used as a reference image for inter prediction with respect to another image. Entropy encoder 7350 may entropy encode the quantized transform coefficient, and the entropy encoded coefficient may be output as bitstream 7400.

[00107] In order for the image encoder 7000 according to various embodiments to be applied to the image encoding apparatus 150, the image encoder 7000 according to various embodiments may perform the operations of each stage on each block.

[00108] FIG. 2E is a block diagram of an image encoding apparatus 150 according to an embodiment.

[00109] The image encoding apparatus 150 according to an embodiment may include a memory 165 and at least one processor 170 coupled to the memory 165. The operations of the image encoding apparatus 150 according to an embodiment may be performed by separate processors or may be controlled by central processor. Also, the memory 165 of the image encoding apparatus 150 may store data received from an external source and data generated by the processor.

[00110] The processor 170 of the image encoding apparatus 150 may apply the intra prediction modes available for the current block and determine the intra prediction mode having the optimal RD cost, may determine, based on the encoding information of the current block, whether the intra prediction mode of the current of a block is to be determined from an intra prediction mode candidate list obtained using a plurality of pieces of adjacent block prediction mode information adjacent to the current block, and when the intra prediction mode of the current block is to be determined from the intra prediction mode candidate list, the processor 170 may generate a bitstream , including intra prediction mode index information indicating one of the intra prediction modes of candidates included in the intra prediction mode candidate list.

[00111] Next, the division of the coding unit will be described in detail in accordance with an embodiment of the disclosure.

[00112] First, one picture may be divided into one or more slices or one or more tiles. One slice or one tile may be a sequence of one or more largest coding units (coding tree units (CTU)). There is a largest coding unit (a coding tree block (CTB)), conceptually comparable to a largest coding unit (CTU).

[00113] The largest coding unit (CTB) refers to an NxN block including NxN samples (where N is an integer). Each color component may be divided into one or more larger coding units.

[00114] When a picture has three sample arrays (sample arrays for the Y, Cr, and Cb components, respectively), the largest coding unit (CTU) includes the largest luminance sample coding unit, the two corresponding largest chrominance sample coding units, and the syntax elements used to encode the luma sample and the chrominance sample. When the picture is a monochrome picture, the largest coding unit includes the largest monochrome sample coding unit and the syntax elements used to encode the monochrome samples. When a picture is a picture encoded in color planes separate according to color components, the largest coding unit includes the syntax elements used to encode the picture and the picture samples.

[00115] One largest coding block (CTB) may be divided into MxN coding blocks including MxN samples (where M and N are integers).

[00116] When a picture has sample arrays for respective Y, Cr, and Cb components, a coding unit (CU) includes a luma sample coding block, two corresponding chrominance sample coding blocks, and syntax elements used to encode a luma sample and a chrominance sample. When the picture is a monochrome picture, the coding unit includes a monochrome sample coding block and syntax elements used to encode monochrome samples. When a picture is a picture encoded in color planes separate according to the color components, the coding unit includes the syntax elements used to encode the picture and the picture samples.

[00117] As described above, the largest coding unit and the largest coding unit are conceptually distinct from each other, and the coding unit and coding unit are conceptually distinct from each other. That is, the (largest) coding unit refers to a data structure including a (largest) coding unit including a corresponding sample and a syntax element corresponding to the (largest) coding unit. However, as one skilled in the art can understand that the (largest) coding unit or (largest) coding unit refers to a predetermined size unit including a predetermined number of samples, a largest coding unit, and a largest coding unit, or a coding unit and a coding unit are referred to in the following specification without distinction, unless otherwise stated.

[00118] An image may be divided into largest coding units (CTUs). The size of each largest coding unit may be determined based on information obtained from the bitstream. The shape of each largest coding unit may be a square shape of the same size. However, disclosure is not limited to this.

[00119] For example, information about the maximum luminance coding block size can be obtained from the bitstream. For example, the maximum luminance coding block size indicated by the maximum luminance coding block size information may be one of 16x16, 32x32, 64x64, 128x128, and 256x256.

[00120] For example, information about the difference between the luminance block size and the maximum luminance coding block size that can be divided by 2 can be obtained from the bitstream. The luminance block size difference information may refer to the size difference between the largest luminance coding unit and the largest luminance coding block that can be divided by 2. Accordingly, when the maximum luminance coding block size information that can be divided by 2 and the size difference information luminance block obtained from the bitstream are combined with each other, the size of the largest luminance coding unit may be determined. The size of the largest chroma coding unit may be determined using the size of the largest luminance coding unit. For example, when the Y:Cb:Cr ratio is 4:2:0 according to the color format, the chrominance block size may be half the size of the luminance block, and the size of the largest chroma coding unit may be half the size of the largest luminance coding unit.

[00121] According to an embodiment, since information about the maximum size of a luminance coding block that is binary separable is obtained from a bitstream, the maximum size of a luminance coding block that is binary separable can be determined in a variable manner. In contrast, the maximum size of a luminance coding block that is ternary separable may be fixed. For example, the maximum size of a luminance coding block that is ternarily separable in an I-picture may be 32×32, and the maximum size of a luminance coding block that is ternarily separable in a P-picture or a B-picture may be 64×64.

[00122] Also, the largest coding unit may be hierarchically divided into coding units based on the divided form mode information obtained from the bitstream. At least one of information indicating whether quad splitting should be performed, information indicating whether multiple splitting should be performed, splitting direction information, and splitting type information can be obtained as split mode mode information from the bitstream.

[00123] For example, information indicating whether a quad split should be performed may indicate whether the current coding unit should be quad split (QUAD_SPLIT) or not.

[00124] When the current coding unit is not to be quadruple splitted, information indicating whether multiple splitting is to be performed may indicate whether the current coding unit is no longer to be split (NO_SPLIT) or it is to be binary/ternary splitted.

[00125] When the current coding unit is binary split or ternary split, the split direction information indicates that the current coding unit is to be split in one of the horizontal direction or the vertical direction.

[00126] When the current coding unit is split in the horizontal direction or the vertical direction, the split type information indicates that the current coding unit is to be binary split or ternary split.

[00127] The split mode of the current coding unit may be determined according to split direction information and split type information. Split mode when the current coding unit is binary split in the horizontal direction may be defined as horizontal binary split mode (SPLIT_BT_HOR), split mode when the current coding unit is ternary split in the horizontal direction, may be defined as horizontal ternary split mode (SPLIT_TT_HOR), split mode , when the current coding unit is binary split in the vertical direction, may be defined as vertical binary split mode (SPLIT_BT_VER), and the split mode, when the current coding unit is ternary split in the vertical direction, can be defined as vertical ternary split mode SPLIT_TT_VER.

[00128] The image decoding apparatus 100 can obtain, from the bitstream, split-form mode information from one bin row. The kind of bit stream received by the image decoding apparatus 100 may include a fixed length binary code, a unary code, a truncated unary code, a predefined binary code, or the like. A bin string represents information in a binary number. The bin string may include at least one bit. The image decoding apparatus 100 can obtain split form mode information corresponding to the bin row based on the split rule. The image decoding apparatus 100 can determine whether to subject a coding unit to a quad division, whether to subject a coding unit to a non-quad division, a division direction, and a division type, based on one bin row.

[00129] The coding unit may be less than or equal to the largest coding unit. For example, since the largest coding unit is a coding unit having a maximum size, the largest coding unit is one of the coding units. When the split form mode information of the largest coding unit indicates that splitting should not be performed, the coding unit specified in the largest coding unit has the same size as the largest coding unit. When the split form code information of the largest coding unit indicates that splitting is to be performed, the largest coding unit may be divided into coding units. Also, when the split form mode information of a coding unit indicates that splitting is to be performed, the coding unit may be divided into smaller coding units. However, the division of an image is not limited to this, and a distinction between the largest coding unit and the coding unit may not be made. The division of a coding unit will be described in detail with reference to FIG. 3-16.

[00130] Also, one or more prediction blocks for prediction may be determined from a coding unit. The prediction block may be equal to or less than the coding unit. Also, one or more transform units for transform may be determined from a coding unit. The transform unit may be equal to or less than the coding unit.

[00131] The shapes and sizes of the transform block and the prediction block may not be related to each other.

[00132] In another embodiment, prediction may be performed using the coding unit as the prediction unit. Also, the transformation may be performed using the coding unit as the transformation block.

[00133] The division of the coding unit will be described in detail with reference to FIG. 3-16. The current block and the adjacent expansion block may indicate one of the largest coding unit, coding unit, prediction block, and transform block. Also, the current block of the current coding unit is a block that is currently being decoded or encoded, or a block that is currently being divided. The adjacent block may be a block restored before the current block. A neighboring block may be spatially or temporally adjacent to the current block. The neighboring block can be located in one of the positions bottom left, left, top left, top, top right, right, bottom right of the current block.

[00134] FIG. 3 illustrates a process performed by the image decoding apparatus 100 to determine at least one coding unit by dividing the current coding unit, according to an embodiment.

[00135] The block shape may include 4Nx4N, 4Nx2N, 2Nx4N, 4NxN, Nx4N, 32NxN, Nx32N, 16NxN, Nx16N, 8NxN or N ×8N. Here, N can be a positive integer. The block shape information is information indicating at least one of a shape, a direction, a width-to-height ratio, or a width-to-height dimension.

[00136] The shape of the coding unit may include square and non-square. When the width and height lengths of the coding unit are equal (ie, when the shape of the coding unit block is 4N×4N), the picture decoding apparatus 100 may determine the shape information of the coding unit block as a square. The image decoding apparatus 100 may determine the shape of the coding unit as non-square.

[00137] When the width and height lengths of the coding unit are different from each other (i.e., when the shape of the coding unit block is 4N×2N, 2N×4N, 4N×N, N×4N, 32N×N, N×32N, 16N×N, N×16N, 8N×N, or N×8N), the image decoding apparatus 100 may determine the shape information of the coding unit block as a non-square shape. When the shape of the coding unit is non-square, the image decoding apparatus 100 may determine the width-to-height ratio in the shape information of the coding unit block as at least one of 1:2, 2:1, 1:4, 4:1, 1:8, 8 :1, 1:16, 16:1, 1:32 and 32:1. Also, the image decoding apparatus 100 can determine whether the coding unit is in the horizontal direction or the vertical direction based on the width length and the height length of the coding unit. Also, the image decoding apparatus 100 may determine the size of the coding unit based on at least one of the length of the width, the length of the height, or the area of the coding unit.

[00138] According to an embodiment, the image decoding apparatus 100 can determine the shape of the coding unit using the block shape information, and can determine the division method of the coding unit using the divided shape mode information. That is, the coding unit division method indicated by the divided form mode information may be determined based on the block shape indicated by the block form information used by the image decoding apparatus 100 .

[00139] The image decoding apparatus 100 can obtain split mode information from the bitstream. However, the embodiment is not limited to this, and the image decoding apparatus 100 and the image encoding apparatus 150 may determine pre-negotiated split-form mode information based on the block shape information. The image decoding apparatus 100 may determine the pre-negotiated split-form mode information with respect to the largest coding unit or the smallest coding unit. For example, the image decoding apparatus 100 may determine split-form mode information with respect to the largest coding unit to be quad split. Also, the image decoding apparatus 100 may determine the split form mode information with respect to the smallest coding unit as "do not split". In particular, the image decoding apparatus 100 may determine the size of the largest coding unit as 256×256. The image decoding apparatus 100 may determine the split-form pre-negotiated mode information to be quad-separated. Quad split is a split shape mode in which both the width and height of a coding unit are split in half. The image decoding apparatus 100 can obtain a 128x128 coding unit from a 256x256 largest coding unit based on split-form mode information. Also, the image decoding apparatus 100 may determine the size of the smallest coding unit as 4×4. The image decoding apparatus 100 can obtain split-form mode information indicating "do not split" with respect to the smallest coding unit.

[00140] According to an embodiment, the image decoding apparatus 100 may use block shape information indicating that the current coding unit is square. For example, the image decoding apparatus 100 can determine whether a square coding unit should not be divided, whether a square coding unit should be vertically divided, whether a square coding unit should be horizontally divided, or whether a square coding unit should be divided into four coding units, based on split-form mode information. . With reference to FIG. 3, when the block shape information of the current coding unit 300 indicates a square shape, the decoder 120 may determine that the coding unit 310a has the same size as the current coding unit 300 based on the divided shape mode information indicating not to perform division, or may determine coding units 310b, 310c, 310d, 310e, or 310f divided based on the split form mode information indicating a predetermined split method.

[00141] With reference to FIG. 3, according to an embodiment, the image decoding apparatus 100 can determine two coding units 310b obtained by dividing the current coding unit 300 in the vertical direction based on split-form mode information indicating to perform split in the vertical direction. The image decoding apparatus 100 can determine the two coding units 310c obtained by dividing the current coding unit 300 in the horizontal direction based on the split shape mode information indicating to perform the split in the horizontal direction. The image decoding apparatus 100 can determine the four coding units 310d obtained by dividing the current coding unit 300 in the vertical and horizontal directions based on the split-form mode information indicating to perform the split in the vertical and horizontal directions. According to an embodiment, the image decoding apparatus 100 can determine three coding units 310e obtained by dividing the current coding unit 300 in the vertical direction, based on split-form mode information indicating to perform ternary split in the vertical direction. The image decoding apparatus 100 may determine the three coding units 310f obtained by dividing the current coding unit 300 in the horizontal direction based on the divided shape mode information indicating to perform ternary separation in the horizontal direction. However, methods for dividing a square coding unit are not limited to the above methods, and may include various methods, which may be indicated by the split-form mode information. Predefined splitting methods for splitting a square coding unit will be described in detail below with respect to various embodiments.

[00142] FIG. 4 illustrates a process performed by the image decoding apparatus 100 for determining at least one coding unit by dividing a non-square coding unit, according to an embodiment.

[00143] According to an embodiment, the image decoding apparatus 100 may use block shape information indicating that the current coding unit is non-square. The picture decoding apparatus 100 can determine whether the non-square current coding unit should not be divided or whether the non-square current coding unit should be divided using a predetermined division method based on the divided shape mode information. With reference to FIG. 4, when the block shape information of the current coding unit 400 or 450 indicates a non-square shape, the picture decoding apparatus 100 may determine that the coding unit 410 or 460 has the same size as the current coding unit 400 or 450 based on the divided shape mode information. indicating not to perform splitting, or may determine encoding units 420a and 420b, 430a, 430b and 430c, 470a and 470b, or 480a, 480b and 480c, which are split based on split form mode information indicating a predetermined splitting method. Predefined splitting methods for splitting a non-square coding unit will be described in detail below with respect to various embodiments.

[00144] According to an embodiment, the image decoding apparatus 100 may determine a coding unit division method using the divided form mode information, and, in this case, the divided form mode information may indicate the number of one or more coding units generated by dividing the coding unit . With reference to FIG. 4, when the split mode information indicates to divide the current coding unit 400 or 450 into two coding units, the picture decoding apparatus 100 may determine two coding units 420a and 420b or 470a and 470b included in the current coding unit 400 or 450, by dividing the current coding unit 400 or 450 based on the split form mode information.

[00145] According to an embodiment, when the image decoding apparatus 100 divides the non-square current coding unit 400 or 450 based on split-shape mode information, the image decoding apparatus 100 may separate the current coding unit considering the location of the long side of the non-square current coding unit 400 or 450 coding. For example, the image decoding apparatus 100 may determine a plurality of coding units by dividing the current coding unit 400 or 450 by splitting the long side of the current coding unit 400 or 450, considering the shape of the current coding unit 400 or 450.

[00146] According to an embodiment, when the split-form mode information indicates to divide (ternary divide) a coding unit into an odd number of blocks, the image decoding apparatus 100 may determine an odd number of coding units included in the current coding unit 400 or 450 . For example, when the split-form mode information indicates to divide the current coding unit 400 or 450 into three coding units, the picture decoding apparatus 100 may divide the current coding unit 400 or 450 into three units 430a, 430b, and 430c or 480a, 480b, and 480c. coding.

[00147] According to an embodiment, the width to height ratio of the current coding unit 400 or 450 may be 4:1 or 1:4. When the width-to-height ratio is 4:1, the block shape information may indicate a horizontal direction because the width length is longer than the height length. When the width-to-height ratio is 1:4, the block shape information may indicate a vertical direction because the width length is shorter than the height length. The image decoding apparatus 100 may determine to divide the current coding unit into an odd number of blocks based on the divided form mode information. Also, the image decoding apparatus 100 may determine the dividing direction of the current coding unit 400 or 450 based on the block shape information of the current coding unit 400 or 450. For example, when the current coding unit 400 is in the vertical direction in which the height is greater than its width, the image decoding apparatus 100 can determine the coding units 430a, 430b, and 430c by dividing the current coding unit 400 in the horizontal direction. Also, when the current coding unit 450 is in the horizontal direction in which the width is larger than its height, the image decoding apparatus 100 can determine the coding units 480a, 480b, and 480c by dividing the current coding unit 450 in the vertical direction.

[00148] According to an embodiment, the image decoding apparatus 100 may determine an odd number of coding units included in the current coding unit 400 or 450, and not all of the determined coding units may have the same size. For example, a predetermined coding unit 430b or 480b of a certain odd number of coding units 430a, 430b and 430c or 480a, 480b and 480c may have a size different from that of other coding units 430a and 430c or 480a and 480c. That is, the coding units, which may be determined by dividing the current coding unit 400 or 450, may have multiple sizes, and, in some cases, an odd number of coding units 430a, 430b, and 430c or 480a, 480b, and 480c may all have different sizes. .

[00149] According to an embodiment, when the split-form mode information indicates to divide a coding unit into an odd number of blocks, the image decoding apparatus 100 may determine an odd number of coding units included in the current coding unit 400 or 450, and furthermore on the other hand, may impose a predetermined restriction on at least one coding unit from an odd number of coding units generated by dividing the current coding unit 400 or 450. With reference to FIG. 4, the image decoding apparatus 100 may allow the decoding process of the coding unit 430b or 480b to be different from the decoding process of the other coding unit 430a and 430c or 480a or 480c, with the coding unit 430b or 480b located at the central location of the three 430a, 430b and 430c or 480a. , 480b and 480c encoding generated by dividing the current unit 400 or 450 coding. For example, the image decoding apparatus 100 may restrict the coding unit 430b or 480b at a central location so that it is no longer split or only split a predetermined number of times, unlike other coding units 430a and 430c or 480a and 480c.

[00150] FIG. 5 illustrates a process performed by the image decoding apparatus 100 of separating a coding unit based on at least one of the block shape information and the divided shape mode information, according to an embodiment.

[00151] According to an embodiment, the image decoding apparatus 100 may determine whether or not to divide the square first coding unit 500 into coding units based on at least one of the block shape information and the divided shape mode information. According to an embodiment, when the divided form mode information indicates to divide the first coding unit 500 in the horizontal direction, the image decoding apparatus 100 may determine the second coding unit 510 by dividing the first coding unit 500 in the horizontal direction. The first coding unit, the second coding unit, and the third coding unit used according to the embodiment are terms used to understand the relationship before and after division of the coding unit. For example, the second coding unit may be determined by dividing the first coding unit, and the third coding unit may be determined by dividing the second coding unit. It will be understood that the structure of the first coding unit, the second coding unit and the third coding unit follows the descriptions above.

[00152] According to an embodiment, the image decoding apparatus 100 may determine to divide the determined second coding unit 510 into coding units based on the divided form mode information, or may determine not to divide the determined second coding unit 510. With reference to FIG. 5, the image decoding apparatus 100 may divide the non-square second coding unit 510, which is determined by dividing the first coding unit 500, into one or more third coding units 520a or 520b, 520c, and 520d based on the split-form mode information, or may not separate the non-square second unit 510 coding. The image decoding apparatus 100 may acquire split-form mode information and may determine a plurality of second coding units (for example, 510) with different shapes by separating the first coding unit 500 based on the obtained split-form mode information, and the second coding unit 510 may be separated using a method separating the first coding unit 500 based on the split form mode information. According to an embodiment, when the first coding unit 500 is divided into second coding units 510 based on the split form mode information of the first coding unit 500, the second coding unit 510 may also be divided into third coding units 520a or 520b, 520c, and 520d based on the mode information split form of the second coding unit 510 . That is, a coding unit can be recursively divided based on the split form mode information of each coding unit. Therefore, a square coding unit may be determined by dividing a non-square coding unit, and a non-square coding unit may be determined by recursively dividing a square coding unit.

[00153] With reference to FIG. 5, a predetermined coding unit (eg, a coding unit located at a central location or a square coding unit) from an odd number of third coding units 520b, 520c, and 520d determined by dividing the non-square second coding unit 510 can be recursively split. According to an embodiment, the non-square third coding unit 520b of an odd number of third coding units 520b, 520c, and 520d may be horizontally divided into a plurality of fourth coding units. The non-square fourth coding unit 530b or 530d of the plurality of fourth coding units 530a, 530b, 530c, and 530d may be re-partitioned into a plurality of coding units. For example, a non-square fourth coding unit 530b or 530d may be re-divided into an odd number of coding units. A method that can be used to recursively split a coding unit will be described below with respect to various embodiments.

[00154] According to an embodiment, the image decoding apparatus 100 may divide each of the third coding units 520a or 520b, 520c, and 520d into coding units based on split-form mode information. Also, the image decoding apparatus 100 may determine not to split the second coding unit 510 based on the split mode mode information. According to an embodiment, the image decoding apparatus 100 may divide the non-square second coding unit 510 into an odd number of third coding units 520b, 520c, and 520d. The image decoding apparatus 100 may impose a predetermined restriction on a predetermined third coding unit from an odd number of third coding units 520b, 520c, and 520d. For example, the image decoding apparatus 100 may limit the third coding unit 520c at a central location from an odd number of third coding units 520b, 520c, and 520d so that it is no longer divided or is divided a set number of times.

[00155] With reference to FIG. 5, the image decoding apparatus 100 may restrict the third coding unit 520c that is at the center location of an odd number of third coding units 520b, 520c, and 520d included in the non-square second coding unit 510 to no longer be split, to be split using a predetermined splitting method (eg, only split into four coding units, or split using the splitting method of the second coding unit 510) or that it is split only a predetermined number of times (eg, split only n times (where n>0)). However, restrictions on the third coding unit 520c at the center location are not limited to the above examples, and it should be understood that the restrictions may include various restrictions for decoding the third coding unit 520c at the center location other than other third coding units 520b and 520d.

[00156] According to an embodiment, the image decoding apparatus 100 can obtain split mode information, which is used to separate the current coding unit, from a predetermined location in the current coding unit.

[00157] FIG. 6 illustrates a method performed by the image decoding apparatus 100 for determining a predetermined coding unit from an odd number of coding units, according to an embodiment.

[00158] With reference to FIG. 6, the split form mode information of the current coding unit 600 or 650 may be obtained from a sample of a predetermined location (eg, a central location sample 640 or 690) from a plurality of samples included in the current coding unit 600 or 650. However, the predetermined location in the current coding unit 600 from which at least one piece of split-form mode information can be obtained is not limited to the center location in FIG. 6 and may include various locations included in the current coding unit 600 (eg, top, bottom, left, right, top left, bottom left, top right, and bottom right locations). The image decoding apparatus 100 may acquire split-form mode information from a predetermined location, and may determine whether or not to split the current coding unit into coding units with different shapes and different sizes.

[00159] According to an embodiment, when the current coding unit is divided into a predetermined number of coding units, the image decoding apparatus 100 may select one of the coding units. Various methods may be used to select one of a plurality of coding units, as will be described below with respect to various embodiments.

[00160] According to an embodiment, the image decoding apparatus 100 may divide the current coding unit into a plurality of coding units, and may determine the coding unit at a predetermined location.

[00161] According to an embodiment, the image decoding apparatus 100 may use information indicating locations of an odd number of coding units to determine a coding unit at a central location from an odd number of coding units. With reference to FIG. 6, the image decoding apparatus 100 may determine an odd number of coding units 620a, 620b, and 620c or an odd number of coding units 660a, 660b, and 660c by dividing the current coding unit 600 or the current coding unit 650. The image decoding apparatus 100 may determine the average coding unit 620b or the average coding unit 660b using the location information of an odd number of coding units 620a, 620b, and 620c or an odd number of coding units 660a, 660b, and 660c. For example, the image decoding apparatus 100 may determine the central location coding unit 620b by determining the locations of the coding units 620a, 620b, and 620c based on information indicative of the locations of the predefined samples included in the coding units 620a, 620b, and 620c. In detail, the image decoding apparatus 100 can determine the coding unit 620b at the center location by determining the locations of the coding units 620a, 620b, and 620c based on information indicative of the locations of the top left samples 630a, 630b, and 630c of the coding units 620a, 620b, and 620c.

[00162] According to an embodiment, information indicating the locations of the top left samples 630a, 630b, and 630c that are included in the coding units 620a, 620b, and 620c, respectively, may include information about the locations or coordinates of the units 620a, 620b, and 620c picture coding. According to an embodiment, information indicative of the locations of the top left samples 630a, 630b, and 630c that are included in coding units 620a, 620b, and 620c, respectively, may include information indicative of widths or heights of coding units 620a, 620b, and 620c, included in the current coding unit 600, and the width or height may correspond to information indicating differences between the coordinates of the coding units 620a, 620b, and 620c in the picture. That is, the image decoding apparatus 100 can determine the coding unit 620b at the central location by directly using information about the locations or coordinates of the coding units 620a, 620b, and 620c in the picture, or using information about the widths or heights of the coding units that correspond to the difference values between the coordinates.

[00163] According to an embodiment, information indicating the location of the upper left sample 630a of the upper coding unit 620a may include coordinates (xa, ya), information indicating the location of the upper left sample 630b of the middle coding unit 620b may include coordinates (xb, yb), and information indicating the location of the upper left sample 630c of the lower coding unit 620c may include coordinates (xc, yc). The image decoding apparatus 100 may determine the middle coding unit 620b using the coordinates of the top left samples 630a, 630b, and 630c that are included in the coding units 620a, 620b, and 620c, respectively. For example, when the coordinates of the top left samples 630a, 630b, and 630c are sorted in ascending or descending order, the coding unit 620b including the coordinates (xb, yb) of the sample 630b at the center location may be determined as the coding unit at the center location of the units 620a, 620b and 620c encoding, determined by dividing the current unit 600 coding. However, coordinates indicating the locations of the top left samples 630a, 630b, and 630c may include coordinates indicating absolute locations in the picture, or may use coordinates (dxb, dyb) indicating the relative location of the top left sample 630b of middle coding unit 620b, and coordinates (dxc, dyc) indicating the relative location of the upper left sample 630c of the lower coding unit 620c with reference to the location of the upper left sample 630a of the upper coding unit 620a. Also, the method of determining the coding unit at a predetermined location using the sample coordinates included in the coding unit as information indicating the location of the sample is not to be understood as limited to the above method, and may include various arithmetic methods capable of using the sample coordinates.

[00164] According to an embodiment, the image decoding apparatus 100 may divide the current coding unit 600 into a plurality of coding units 620a, 620b, and 620c, and may select one of the coding units 620a, 620b, and 620c based on a predetermined criterion. For example, the image decoding apparatus 100 may select a coding unit 620b that has a different size than the others of the coding units 620a, 620b, and 620c.

[00165] According to an embodiment, the image decoding apparatus 100 may determine the width or height of each of the coding units 620a, 620b, and 620c using coordinates (xa, ya), which are information indicating the location of the upper left sample 630a of the upper coding unit 620a , coordinates (xb, yb) which are information indicating the location of the upper left sample 630b of the middle coding unit 620b, and coordinates (xc, yc) which are information indicating the location of the upper left sample 630c of the lower coding unit 620c. The image decoding apparatus 100 may determine the respective sizes of the coding units 620a, 620b, and 620c using the coordinates (xa, ya), (xb, yb), and (xc, yc) indicating the locations of the coding units 620a, 620b, and 620c. According to an embodiment, the image decoding apparatus 100 may determine the width of the upper coding unit 620a as the width of the current coding unit 600. The image decoding apparatus 100 may determine the height of the upper encoding unit 620a as yb-ya. According to an embodiment, the image decoding apparatus 100 may determine the width of the middle coding unit 620b as the width of the current coding unit 600 . The image decoding apparatus 100 may determine the height of the middle coding unit 620b as yc-yb. According to an embodiment, the image decoding apparatus 100 may determine the width or height of the lower coding unit 620c using the width or height of the current coding unit 600 or the widths or heights of the upper and middle coding units 620a and 620b. The image decoding apparatus 100 may determine a coding unit that has a different size than others based on the determined widths and heights of the coding units 620a, 620b, and 620c. With reference to FIG. 6, the image decoding apparatus 100 may determine the middle coding unit 620b, which has a size different from that of the upper and lower coding units 620a and 620c, as the coding unit of the predetermined location. However, by the image decoding apparatus 100, the aforementioned method of determining a coding unit having a size different from that of other coding units only corresponds to an example of determining a coding unit at a predetermined location using coding unit sizes that are determined based on sample coordinates, and thus may various methods of determining a coding unit at a predetermined location are used by comparing sizes of coding units that are determined based on coordinates of predefined samples.

[00166] The image decoding apparatus 100 may determine the width or height of each of the encoding units 660a, 660b, and 660c using coordinates (xd, yd), which are information indicating the location of the upper left sample 670a of the left encoding unit 660a, coordinates (xe, ye ) which are information indicating the location of the upper left sample 670b of the middle coding unit 660b, and coordinates (xf, yf) which are information indicating the location of the upper left sample 670c of the right coding unit 660c. The image decoding apparatus 100 may determine the respective sizes of the coding units 660a, 660b, and 660c using the coordinates (xd, yd), (xe, ye), and (xf, yf) indicating the locations of the coding units 660a, 660b, and 660c.

[00167] According to an embodiment, the image decoding apparatus 100 may determine the width of the left encoding unit 660a as xe-xd. The image decoding apparatus 100 may determine the height of the left coding unit 660a as the height of the current coding unit 650 . According to an embodiment, the image decoding apparatus 100 may determine the width of the middle coding unit 660b as xf-xe. The image decoding device 100 may determine the height of the middle coding unit 660b as the height of the current coding unit 650 . According to an embodiment, the image decoding apparatus 100 may determine the width or height of the right coding unit 660c using the width or height of the current coding unit 650 or the widths or heights of the left and middle coding units 660a and 660b. The image decoding apparatus 100 may determine a coding unit that has a different size than the others based on the determined widths and heights of the coding units 660a, 660b, and 660c. With reference to FIG. 6, the image decoding apparatus 100 may determine the middle coding unit 660b, which has a size different from the sizes of the left and right coding units 660a and 660c, as the coding unit of the predetermined location. However, by the image decoding apparatus 100, the aforementioned method of determining a coding unit having a size different from that of other coding units simply corresponds to an example of determining a coding unit at a predetermined location using coding unit sizes that are determined based on sample coordinates, and thus can various methods of determining a coding unit at a predetermined location are used by comparing sizes of coding units that are determined based on coordinates of predefined samples.

[00168] However, the locations of the samples taken into account to determine the locations of the coding units are not limited to the aforementioned upper left locations, and information about arbitrary locations of the samples included in the coding units can be used.

[00169] According to an embodiment, the image decoding apparatus 100 may select a coding unit at a predetermined location from an odd number of coding units determined by dividing the current coding unit based on the shape of the current coding unit. For example, when the current coding unit has a non-square shape whose width is longer than its height, the image decoding apparatus 100 can determine the coding unit at a predetermined location in the horizontal direction. That is, the image decoding apparatus 100 may determine one of the coding units at different locations in the horizontal direction, and may impose a restriction on the coding unit. When the current coding unit has a non-square shape whose height is longer than its width, the image decoding apparatus 100 may determine the coding unit at a predetermined location in the vertical direction. That is, the image decoding apparatus 100 may determine one of the coding units at different locations in the vertical direction, and may impose a restriction on the coding unit.

[00170] According to an embodiment, the image decoding apparatus 100 may use information indicating respective locations of an even number of coding units to determine a coding unit at a predetermined location from an even number of coding units. The image decoding apparatus 100 may determine an even number of coding units by dividing (binary division) the current coding unit, and may determine the coding unit at a predetermined location using the location information of the even number of coding units. The operation related to this may correspond to the operation of determining a coding unit at a predetermined location (eg, a central location) from an odd number of coding units, as described in detail above with reference to FIG. 6, and thus detailed descriptions thereof are omitted here.

[00171] According to an embodiment, when a non-square current coding unit is divided into a plurality of coding units, predetermined information about a coding unit at a predetermined location may be used in a partitioning process to determine a coding unit at a predetermined location from among the plurality of coding units. For example, the image decoding apparatus 100 may use at least one of the block shape information and the divided form mode information that is stored in the sample included in the middle coding unit in the splitting process to determine the coding unit at the center location from the plurality of coding units determined by by splitting the current coding unit.

[00172] With reference to FIG. 6, the image decoding apparatus 100 may divide the current coding unit 600 into a plurality of coding units 620a, 620b, and 620c based on split-form mode information, and may determine a coding unit 620b at a central location from the plurality of coding units 620a, 620b, and 620c. Moreover, the image decoding apparatus 100 can determine the coding unit 620b at the central location, considering the location from which split mode information is obtained. That is, the split-form mode information of the current coding unit 600 can be obtained from the sample 640 at the center location of the current coding unit 600, and when the current coding unit 600 is divided into a plurality of coding units 620a, 620b, and 620c based on the split-form mode information, the unit An encoding 620b including sample 640 may be defined as an encoding unit at a central location. However, the information used to determine the coding unit at the central location is not limited to split-form mode information, and various types of information may be used to determine the coding unit at the central location.

[00173] According to an embodiment, predefined information for identifying a coding unit at a predefined location can be obtained from a predefined sample included in the coding unit to be determined. With reference to FIG. 6, the image decoding apparatus 100 may use split-form mode information that is obtained from a sample at a predetermined location in the current coding unit 600 (for example, a sample at the center location of the current coding unit 600) to determine a coding unit at a predetermined location from the plurality of units 620a, 620b and 620c of the coding determined by dividing the current coding unit 600 (eg, the coding unit at the central location from the plurality of divided coding units). That is, the image decoding apparatus 100 may determine a sample at a predetermined location considering the block shape of the current coding unit 600, may determine a coding unit 620b including a sample from which predetermined information (e.g., split-form mode information) is obtained, from a plurality of units 620a, 620b, and 620c coding determined by dividing the current coding unit 600 and may impose a predetermined constraint on the coding unit 620b. With reference to FIG. 6, according to an embodiment, the image decoding apparatus 100 may determine the sample 640 at the center location of the current coding unit 600 as the sample from which predetermined information is obtained, and may impose a predetermined constraint on the coding unit 620b including the sample 640 in operation decoding. However, the location of the sample from which the predetermined information is obtained is not limited to the above location, and may include arbitrary locations of the samples included in the coding unit 620b to be determined for restriction.

[00174] According to an embodiment, the location of the sample from which the predetermined information is obtained may be determined based on the shape of the current coding unit 600. According to an embodiment, the block shape information may indicate whether the current coding unit is square or non-square, and the location of the sample from which the predetermined information is obtained may be determined based on the shape. For example, the image decoding apparatus 100 may determine a sample located at the boundary for dividing at least one of the width and height of the current coding unit in half as a sample from which predetermined information is obtained using at least one of the width information of the current coding unit and information about the height of the current coding unit. As another example, when the block shape information of the current coding unit indicates a non-square shape, the picture decoding apparatus 100 may determine one of the samples adjacent to the boundary for halving the long side of the current coding unit as a sample from which predetermined information is obtained.

[00175] According to an embodiment, when the current coding unit is divided into a plurality of coding units, the image decoding apparatus 100 can use split-form mode information to determine a coding unit at a predetermined location from the plurality of coding units. According to an embodiment, the image decoding apparatus 100 can obtain split-form mode information from a sample at a predetermined location in a coding unit, and can split a plurality of coding units that are generated by splitting the current coding unit using split-form mode information that is obtained from the sample a predetermined location in each of the plurality of coding units. That is, a coding unit can be recursively divided based on the split form mode information that is obtained from a sample at a predetermined location in each coding unit. The operation of recursively dividing a coding unit is described above with reference to FIG. 5, and thus detailed descriptions thereof are omitted here.

[00176] According to an embodiment, the image decoding apparatus 100 may determine one or more coding units by separating the current coding unit, and may determine the decoding order of one or more coding units based on a predetermined block (eg, the current coding unit).

[00177] FIG. 7 illustrates a processing order of a plurality of coding units when the image decoding apparatus 100 determines a plurality of coding units by dividing the current coding unit, according to an embodiment.

[00178] According to an embodiment, the image decoding apparatus 100 may determine the second coding units 710a and 710b by splitting the first coding unit 700 in the vertical direction, may determine the second coding units 730a and 730b by splitting the first coding unit 700 in the horizontal direction, or may determine the second coding units 750a, 750b, 750c, and 750d by dividing the first coding unit 700 in the vertical and horizontal directions based on the split-form mode information.

[00179] With reference to FIG. 7, the image decoding apparatus 100 may determine to process the second coding units 710a and 710b in the horizontal direction order 710c, the second coding units 710a and 710b being determined by dividing the first coding unit 700 in the vertical direction. The image decoding apparatus 100 may determine that the second coding units 730a and 730b should be processed in the vertical direction order 730c, the second coding units 730a and 730b being determined by dividing the first coding unit 700 in the horizontal direction. The image decoding apparatus 100 may determine the second coding units 750a, 750b, 750c, and 750d, which are determined by dividing the first coding unit 700 in the vertical and horizontal directions, according to a predetermined order (e.g., raster scan order or Z-scan order 750e), whereby the coding units in the line are processed, and then the coding units in the next line are processed.

[00180] According to an embodiment, the image decoding apparatus 100 may recursively separate coding units. With reference to FIG. 7, the image decoding apparatus 100 may determine a plurality of coding units 710a and 710b, 730a and 730b or 750a, 750b, 750c and 750d by separating the first coding unit 700, and may recursively separate each of the determined plurality of 710a and 710b, 730a and 730b or 750a. , 750b, 750c and 750d encoding. The method of separating the plurality of coding units 710a and 710b, 730a and 730b or 750a, 750b, 750c and 750d may correspond to the method of separating the first coding unit 700. Accordingly, each of the plurality of coding units 710a and 710b, 730a and 730b or 750a, 750b, 750c and 750d can be independently divided into a plurality of coding units. With reference to FIG. 7, the image decoding apparatus 100 may determine the second coding units 710a and 710b by separating the first coding unit 700 in the vertical direction, and may determine whether to independently separate each of the second coding units 710a and 710b or not to separate the second coding units 710a and 710b.

[00181] According to an embodiment, the image decoding apparatus 100 may determine the third coding units 720a and 720b by separating the left second coding unit 710a in the horizontal direction, and may not separate the right second coding unit 710b.

[00182] According to an embodiment, the processing order of coding units may be determined based on a coding unit split operation. In other words, the processing order of the split coding units may be determined based on the processing order of the coding units immediately prior to splitting. The image decoding apparatus 100 may determine the processing order of the third coding units 720a and 720b determined by dividing the left second coding unit 710a independently of the right second coding unit 710b. Since the third coding units 720a and 720b are determined by dividing the left second coding unit 710a in the horizontal direction, the third coding units 720a and 720b can be processed in the order 720c of the vertical direction. Since the left and right second coding units 710a and 710b are processed in the horizontal direction order 710c, the right second coding unit 710b can be processed after the third coding units 720a and 720b included in the left second coding unit 710a are processed in the vertical direction order 720c. It should be understood that the operation of determining the processing order of coding units based on the coding unit before splitting is not limited to the above example, and various methods can be used to independently process coding units that are separated and defined with different shapes in a predetermined order.

[00183] FIG. 8 illustrates a process performed by the image decoding apparatus 100 for determining that the current coding unit is to be divided into an odd number of coding units when the coding units cannot be processed in a predetermined order, according to an embodiment.

[00184] According to an embodiment, the image decoding apparatus 100 may determine that the current coding unit is to be divided into an odd number of coding units based on the received divided mode information. With reference to FIG. 8, the square first coding unit 800 may be partitioned into non-square second coding units 810a and 810b, and the second coding units 810a and 810b may be independently partitioned into third coding units 820a and 820b, and 820c, 820d and 820e. According to an embodiment, the image decoding apparatus 100 may determine a plurality of third coding units 820a and 820b by separating the left second coding unit 810a in the horizontal direction, and may divide the right second coding unit 810b into an odd number of third coding units 820c, 820d, and 820e.

[00185] According to an embodiment, the image decoding apparatus 100 can determine whether there is an odd number of divided coding units by determining whether it is possible to process the third coding units 820a and 820b and 820c, 820d and 820e in a predetermined order. With reference to FIG. 8, the image decoding apparatus 100 may determine the third coding units 820a and 820b and 820c, 820d, and 820e by recursively dividing the first coding unit 800. The image decoding apparatus 100 can determine whether any of the first coding unit 800, the second coding units 810a and 810b, or the third coding units 820a and 820b and 820c, 820d and 820e coding is to be divided into an odd number of coding units, based on at least one of block shape information; and split shape mode information. For example, the second coding unit 810b located on the right among the second coding units 810a and 810b may be divided into an odd number of third coding units 820c, 820d and 820e. The processing order of the plurality of coding units included in the first coding unit 800 may be a predetermined order (for example, the Z-scan order 830), and the image decoding apparatus 100 may determine whether the third coding units 820c, 820d, and 820e are satisfied, which are determined by dividing the right second coding unit 810b into an odd number of coding units, a condition for processing in a predetermined order.

[00186] According to an embodiment, the image decoding apparatus 100 can determine whether the third coding units 820a and 820b, and 820c, 820d, and 820e coding included in the first coding unit 800 satisfy a condition for processing in a predetermined order, and the condition refers to whether at least one of the width and height of the second coding units 810a and 810b is to be split in half along the border of the third coding units 820a and 820b and 820c, 820d and 820e. For example, the third coding units 820a and 820b determined when the height of the left second non-square coding unit 810a is halved may satisfy the condition. It may be determined that the third coding units 820c, 820d, and 820e do not satisfy the condition because the boundaries of the third coding units 820c, 820d, and 820e determined when the right second coding unit 810b is divided into three coding units are not able to divide the width or height of the right second unit 810b coding in half. When the condition is not satisfied as described above, the image decoding apparatus 100 may determine the scan order disjointness and may determine that the right second coding unit 810b is to be divided into an odd number of coding units based on the determination result. According to an embodiment, when a coding unit is divided into an odd number of coding units, the image decoding apparatus 100 may impose a predetermined limit on the coding unit at a predetermined location of the divided coding units. The limitation or predetermined location has been described above with respect to the various embodiments, and thus their detailed descriptions are omitted here.

[00187] FIG. 9 illustrates a process performed by the image decoding apparatus 100 to determine at least one coding unit by dividing the first coding unit 900, according to an embodiment.

[00188] According to an embodiment, the image decoding apparatus 100 may separate the first coding unit 900 based on the split mode mode information that is obtained by a receiver (not shown). The square first coding unit 900 may be divided into four square coding units, or may be divided into multiple non-square coding units. For example, with reference to FIG. 9, when the first coding unit 900 is a square and the split-form mode information indicates to divide the first coding unit 900 into non-square coding units, the picture decoding apparatus 100 may divide the first coding unit 900 into a plurality of non-square coding units. In detail, when the split mode information indicates to determine an odd number of coding units by dividing the first coding unit 900 in the horizontal direction or the vertical direction, the picture decoding apparatus 100 may divide the square first coding unit 900 into an odd number of coding units, such as second coding units 910a, 910b, and 910c determined by dividing the square first coding unit 900 in the vertical direction, or second coding units 920a, 920b, and 920c determined by dividing the square first coding unit 900 in the horizontal direction.

[00189] According to an embodiment, the image decoding apparatus 100 can determine whether the second coding units 910a, 910b, 910c, 920a, 920b, and 920c included in the first coding unit 900 satisfy a condition for processing in a predetermined order, and the condition refers to whether at least one of the width and height of the first coding unit 900 is to be split in half along the boundary of the second coding units 910a, 910b, 910c, 920a, 920b, and 920c. With reference to FIG. 9, since the boundaries of the second coding units 910a, 910b, and 910c determined by dividing the square first coding unit 900 in the vertical direction do not bisect the width of the first coding unit 900, it may be determined that the first coding unit 900 does not satisfy the condition for processing in a predetermined order. . Also, since the boundaries of the second coding units 920a, 920b, and 920c determined by dividing the square first coding unit 900 in the horizontal direction do not bisect the height of the first coding unit 900, it can be determined that the first coding unit 900 does not satisfy the condition for processing in predefined order. When the condition is not satisfied as described above, the image decoding apparatus 100 may determine the scan order disjointness and may determine that the first coding unit 900 is to be divided into an odd number of coding units based on the determination result. According to an embodiment, when a coding unit is divided into an odd number of coding units, the image decoding apparatus 100 may impose a predetermined limit on the coding unit at a predetermined location of the divided coding units. The limitation or predetermined location has been described above with respect to various embodiments, and thus its detailed descriptions are omitted here.

[00190] According to an embodiment, the image decoding apparatus 100 can determine coding units with different shapes by separating the first coding unit.

[00191] With reference to FIG. 9, the image decoding apparatus 100 may divide the square first coding unit 900 or the non-square first coding unit 930 or 950 into coding units with different shapes.

[00192] FIG. 10 illustrates that the shape into which the second coding unit can be divided is limited when the second coding unit having a non-square shape, which is determined when the image decoding apparatus 100 divides the first coding unit 1000, satisfies a predetermined condition, according to an embodiment.

[00193] According to an embodiment, the image decoding apparatus 100 may determine to divide the square first coding unit 1000 into non-square second coding units 1010a and 1010b or 1020a and 1020b coding, based on split-form mode information that is obtained by a receiver (not shown). The second coding units 1010a and 1010b or 1020a and 1020b may be independently separated. Accordingly, the image decoding apparatus 100 may determine whether or not to divide each of the second coding units 1010a and 1010b or 1020a and 1020b into a plurality of coding units based on the divided form mode information of each of the second coding units 1010a and 1010b or 1020a and 1020b. According to an embodiment, the image decoding apparatus 100 may determine the third coding units 1012a and 1012b by dividing the non-square left second coding unit 1010a, which is determined by dividing the first coding unit 1000 in the vertical direction, in the horizontal direction. However, when the left second coding unit 1010a is split in the horizontal direction, the picture decoding apparatus 100 may restrict the right second coding unit 1010b not to be split in the horizontal direction in which the left second coding unit 1010a is split. When the third coding units 1014a and 1014b are determined by separating the right second coding unit 1010b in the same direction, since the left second coding unit 1010a and the right second coding unit 1010b are separated independently in the horizontal direction, the third units 1012a and 1012b or 1014a may be determined and 1014b encoding. However, this case serves the same as the case in which the image decoding apparatus 100 divides the first coding unit 1000 into four square second coding units 1030a, 1030b, 1030c, and 1030d based on split-form mode information, and may be inefficient in terms of image decoding. .

[00194] According to an embodiment, the image decoding apparatus 100 may determine the third coding units 1022a and 1022b or 1024a and 1024b by dividing the non-square second coding unit 1020a or 1020b, which is determined by dividing the first coding unit 1000 in the horizontal direction, in the vertical direction . However, when the second coding unit (for example, the upper second coding unit 1020a) is split in the vertical direction, for the above reason, the picture decoding apparatus 100 may restrict the other second coding unit (for example, the lower second coding unit 1020b) not to be split in the vertical direction. the direction in which the upper second coding unit 1020a is split.

[00195] FIG. 11 illustrates the process of dividing a square coding unit by the image decoding apparatus 100 when split mode information indicates that a square coding unit is not to be divided into four square coding units, according to an embodiment.

[00196] According to an embodiment, the image decoding apparatus 100 may determine the second units 1110a and 1110b or 1120a and 1120b, etc. encoding by dividing the first encoding unit 1100 based on the split form mode information. The split-form mode information may include information on various division methods of a coding unit, but information on various division methods may not include information for dividing a coding unit into four square coding units. Based on the divided mode information, the image decoding apparatus 100 does not divide the square first coding unit 1100 into four square second coding units 1130a, 1130b, 1130c, and 1130d. Image decoding apparatus 100 may determine non-square second units 1110a and 1110b or 1120a and 1120b, and so on. coding, based on the split-form mode information.

[00197] According to an embodiment, the image decoding apparatus 100 can independently separate non-square second units 1110a and 1110b or 1120a and 1120b, etc. coding. Each of the second units 1110a and 1110b or 1120a and 1120b, etc. coding may be recursively split in a predetermined order, and this splitting method may correspond to the splitting method of the first coding unit 1100 based on split form mode information.

[00198] For example, the image decoding apparatus 100 may determine the square third coding units 1112a and 1112b by splitting the left second coding unit 1110a in the horizontal direction, and may determine the square third coding units 1114a and 1114b by splitting the right second coding unit 1110b in the horizontal direction. Moreover, the image decoding apparatus 100 can determine the square third coding units 1116a, 1116b, 1116c, and 1116d by separating both the left second coding unit 1110a and the right second coding unit 1110b in the horizontal direction. In this case, coding units having the same shape as the four square second coding units 1130a, 1130b, 1130c, and 1130d divided from the first coding unit 1100 can be determined.

[00199] As another example, the image decoding apparatus 100 may determine the square third coding units 1122a and 1122b by splitting the upper second coding unit 1120a in the vertical direction, and may determine the square third coding units 1124a and 1124b by splitting the lower second coding unit 1120b in the vertical direction. direction. Moreover, the image decoding apparatus 100 can determine the square third coding units 1126a, 1126b, 1126c, and 1126d by separating both the upper second coding unit 1120a and the lower second coding unit 1120b in the vertical direction. In this case, coding units having the same shape as the four square second coding units 1130a, 1130b, 1130c, and 1130d divided from the first coding unit 1100 can be determined.

[00200] FIG. 12 illustrates that the processing order between multiple coding units may change depending on the coding unit splitting process, according to an embodiment.

[00201] According to an embodiment, the image decoding apparatus 100 can separate the first coding unit 1200 based on the divided form mode information. When the block shape indicates a square shape and the divided shape mode information indicates to divide the first coding unit 1200 in at least one of the horizontal and vertical directions, the picture decoding apparatus 100 may determine the second units 1210a and 1210b or 1220a and 1220b, etc. d. encoding by dividing the first unit 1200 encoding. With reference to FIG. 12, non-square second coding units 1210a and 1210b or 1220a and 1220b determined by dividing the first coding unit 1200 only in the horizontal direction or the vertical direction can be independently separated based on the split form mode information of each coding unit. For example, the image decoding apparatus 100 may determine the third coding units 1216a, 1216b, 1216c, and 1216d by dividing the second coding units 1210a and 1210b, which are generated by dividing the first coding unit 1200 in the vertical direction, in the horizontal direction, and may determine the third coding units 1226a, 1226b, 1226c and 1226d coding by splitting the second coding units 1220a and 1220b, which are generated by splitting the first coding unit 1200 in the horizontal direction, in the vertical direction. The operation of separating the second coding units 1210a and 1210b or 1220a and 1220b has been described above with reference to FIG. 11, and thus detailed descriptions thereof are omitted here.

[00202] According to an embodiment, the image decoding apparatus 100 may process coding units in a predetermined order. The operation of processing coding units in a predetermined order has been described above with reference to FIG. 7, and thus detailed descriptions thereof are omitted here. With reference to FIG. 12, the image decoding apparatus 100 may determine four square third coding units 1216a, 1216b, 1216c, and 1216d or 1226a, 1226b, 1226c, and 1226d by dividing the square first coding unit 1200. According to an embodiment, the image decoding apparatus 100 may determine the processing orders of the third coding units 1216a, 1216b, 1216c, and 1216d or 1226a, 1226b, 1226c, and 1226d based on the divided form into which the first coding unit 1200 is divided.

[00203] According to an embodiment, the image decoding apparatus 100 may determine the third coding units 1216a, 1216b, 1216c, and 1216d by dividing the second coding units 1210a and 1210b generated by dividing the first coding unit 1200 in the vertical direction, in the horizontal direction, and can process the third coding units 1216a, 1216b, 1216c, and 1216d in the processing order 1217 to process first the third coding units 1216a and 1216c that are included in the left second coding unit 1210a in the vertical direction, and then process the third coding units 1216b and 1216d that are included to the right second coding unit 1210b, in the vertical direction.

[00204] According to an embodiment, the image decoding apparatus 100 may determine the third coding units 1226a, 1226b, 1226c, and 1226d by dividing the second coding units 1220a and 1220b generated by dividing the first coding unit 1200 in the horizontal direction, in the vertical direction, and can process the third coding units 1226a, 1226b, 1226c, and 1226d in the processing order 1227 to process first the third coding units 1226a and 1226b that are included in the upper second coding unit 1220a in the horizontal direction, and then process the third coding units 1226c and 1226d that are included to the lower second coding unit 1220b, in the horizontal direction.

[00205] With reference to FIG. 12, square third coding units 1216a, 1216b, 1216c, and 1216d, and 1226a, 1226b, 1226c, and 1226d may be determined by dividing second coding units 1210a and 1210b, and 1220a and 1220b, respectively. Although the second coding units 1210a and 1210b are determined by dividing the first coding unit 1200 in the vertical direction differently from the second coding units 1220a and 1220b, which are determined by dividing the first coding unit 1200 in the horizontal direction, the third units 1216a, 1216b, 1216c and 1216d, and 1226a , 1226b, 1226c and 1226d coding separated from them, in the end show the coding units of the same form, divided from the first coding unit 1200. Accordingly, by recursively dividing a coding unit differently based on the split-form mode information, the picture decoding apparatus 100 can process a plurality of coding units in different orders even when it is finally determined that the coding units have the same shape.

[00206] FIG. 13 illustrates a process for determining the depth of a coding unit as the shape and size of a coding unit change when a coding unit is recursively divided so that a plurality of coding units are determined, according to an embodiment.

[00207] According to an embodiment, the image decoding apparatus 100 may determine the depth of a coding unit based on a predetermined criterion. For example, the predefined criterion may be the length of the long side of the coding unit. When the length of the long side of the coding unit before splitting is 2n times (n>0) the length of the long side of the splitted current coding unit, the picture decoding apparatus 100 may determine that the depth of the current coding unit increases from the depth of the coding unit to split by n. In the following descriptions, a coding unit having an increased depth is expressed as a coding unit of a deeper depth.

[00208] With reference to FIG. 13, according to an embodiment, the image decoding apparatus 100 may determine the second coding unit 1302 and the third deeper-depth coding unit 1304 by dividing the square first coding unit 1300 based on block shape information indicating a square shape (for example, the block shape information may be expressed as '0: SQUARE'). Assuming that the size of the square first coding unit 1300 is 2N×2N, the second coding unit 1302, determined by dividing the width and height of the first coding unit 1300 by 1/2, may have a size of N×N. Moreover, the third coding unit 1304, determined by dividing the width and height of the second coding unit 1302 by 1/2, may have a size of N/2×N/2. In this case, the width and height of the third coding unit 1304 is 1/4 of the width and height of the first coding unit 1300. When the depth of the first coding unit 1300 is D, the depth of the second coding unit 1302, whose width and height are 1/2 of the width and height of the first coding unit 1300, may be D+1, and the depth of the third coding unit 1304, whose width and height are 1 /4 width and height of the first unit 1300 coding may be D+2.

[00209] According to an embodiment, the image decoding apparatus 100 may determine the second coding unit 1312 or 1322 and the third deeper-depth coding unit 1314 or 1324 by dividing the non-square first coding unit 1310 or 1320 based on the block shape information indicating the non-square shape ( for example, the block shape information may be expressed as '1: NS_VER' indicating a non-square shape whose height is longer than its width, or as '2: NS_HOR' indicating a non-square shape whose width is longer than its height).

[00210] The image decoding device 100 may determine the second coding unit 1302, 1312, or 1322 by separating at least one of the width and height of the first coding unit 1310 having a size of N×2N. That is, the image decoding apparatus 100 may determine a second coding unit 1302 having a size of N×N or a second coding unit 1322 having a size of N×N/2 by dividing the first coding unit 1310 in a horizontal direction, or may determine a second coding unit 1312 , having a size of N/2×N, by separating the first coding unit 1310 in the horizontal and vertical directions.

[00211] According to an embodiment, the image decoding apparatus 100 may determine the second coding unit 1302, 1312 or 1322 by dividing at least one of the width and height of the first coding unit 1320 having a size of 2N×N. That is, the image decoding apparatus 100 may determine a second coding unit 1302 having a size of N×N or a second coding unit 1312 having a size of N/2×N by dividing the first coding unit 1320 in the vertical direction, or may determine a second coding unit 1322 , having a size of N×N/2, by dividing the first coding unit 1320 in the horizontal and vertical directions.

[00212] According to an embodiment, the image decoding apparatus 100 may determine the third coding unit 1304, 1314, or 1324 by separating at least one of the width and height of the second coding unit 1302 having a size of N×N. That is, the image decoding apparatus 100 may determine a third coding unit 1304 having a size of N/2×N/2, a third coding unit 1314 having a size of N/4×N/2, or a third coding unit 1324 having a size of N/2 ×N/4, by separating the second coding unit 1302 in the vertical and horizontal directions.

[00213] According to an embodiment, the image decoding apparatus 100 may determine the third coding unit 1304, 1314, or 1324 by separating at least one of the width and height of the second coding unit 1312 having a size of N/2×N. That is, the image decoding apparatus 100 can determine a third coding unit 1304 having a size of N/2×N/2 or a third coding unit 1324 having a size of N/2×N/4 by dividing the second coding unit 1312 in the horizontal direction, or may determine a third coding unit 1314 having a size of N/4×N/2 by dividing the second coding unit 1312 in the vertical and horizontal directions.

[00214] According to an embodiment, the image decoding apparatus 100 may determine the third coding unit 1304, 1314, or 1324 by dividing at least one of the width and height of the second coding unit 1322 having a size of N×N/2. That is, the image decoding apparatus 100 can determine a third coding unit 1304 having a size of N/2×N/2 or a third coding unit 1314 having a size of N/4×N/2 by dividing the second coding unit 1322 in the vertical direction, or may determine a third coding unit 1324 having a size of N/2×N/4 by separating the second coding unit 1322 in the vertical and horizontal directions.

[00215] According to an embodiment, the image decoding apparatus 100 may divide a square coding unit 1300, 1302, or 1304 in a horizontal or vertical direction. For example, the image decoding apparatus 100 may determine the first coding unit 1310 having a size of N×2N by dividing the first coding unit 1300 having a size of 2N×2N in the vertical direction, or may determine the first coding unit 1320 having a size of 2N×N by separating the first coding unit 1300 in the horizontal direction. According to an embodiment, when the depth is determined based on the length of the longest side of the coding unit, the depth of the coding unit determined by dividing the first coding unit 1300 having a size of 2N×2N in the horizontal or vertical direction may be the same as the depth the first unit 1300 coding.

[00216] According to an embodiment, the width and height of the third coding unit 1314 or 1324 may be 1/4 of the width and height of the first coding unit 1310 or 1320. When the depth of the first coding unit 1310 or 1320 is D, the depth of the second coding unit 1312 or 1322, whose width and height are 1/2 of the width and height of the first coding unit 1310 or 1320, may be D+1, and the depth of the third coding unit 1314 or 1324 an encoding whose width and height are 1/4 of the width and height of the first encoding unit 1310 or 1320 may be D+2.

[00217] FIG. 14 illustrates depths that are available to be determined based on shapes and sizes of coding units, and part indices (PIDs) that serve to distinguish coding units, according to an embodiment.

[00218] According to an embodiment, the image decoding apparatus 100 can determine second coding units with different shapes by dividing the square of the first coding unit 1400. With reference to FIG. 14, the image decoding apparatus 100 may determine the second coding units 1402a and 1402b, 1404a and 1404b, and 1406a, 1406b, 1406c, and 1406d by dividing the first coding unit 1400 in at least one of the vertical and horizontal directions based on split-form mode information. That is, the image decoding apparatus 100 can determine the second coding units 1402a and 1402b, 1404a and 1404b, and 1406a, 1406b, 1406c, and 1406d, based on the split form mode information of the first coding unit 1400.

[00219] According to an embodiment, the depths of the second coding units 1402a and 1402b, 1404a and 1404b, and 1406a, 1406b, 1406c, and 1406d, which are determined based on the divided shape mode information of the square first coding unit 1400, may be determined based on the length of its long side. For example, since the length of a side of the square first coding unit 1400 is equal to the length of the long side of the non-square second coding unit 1402a and 1402b and 1404a and 1404b, the first coding unit 1400 and the non-square second coding units 1402a and 1402b and 1404a and 1404b may have the same depth, such as D. However, when the image decoding apparatus 100 divides the first coding unit 1400 into four square second coding units 1406a, 1406b, 1406c, and 1406d based on the divided shape mode information, since the side length of the square second coding units 1406a, 1406b, 1406c, and 1406d is 1/2 the side length of the first coding unit 1400, the depth of the second coding units 1406a, 1406b, 1406c, and 1406d may be D+1, which is deeper than the D depth of the first coding unit 1400 by 1.

[00220] According to an embodiment, the image decoding apparatus 100 may determine a plurality of second coding units 1412a and 1412b, and 1414a, 1414b, and 1414c coding by dividing the first coding unit 1410 whose height is longer than its width in the horizontal direction based on the information split mode. According to an embodiment, the image decoding apparatus 100 may determine a plurality of second coding units 1422a and 1422b, and 1424a, 1424b, and 1424c coding by splitting the first coding unit 1420 whose width is longer than its height in the vertical direction based on split-form mode information .

[00221] According to an embodiment, the depth of the second encoding units 1412a and 1412b, and 1414a, 1414b and 1414c, or 1422a and 1422b, and 1424a, 1424b and 1424c, which are determined based on the divided shape mode information of the non-square first unit 1410 or 1420 coding may be determined based on the length of its long side. For example, since the side length of the square second coding units 1412a and 1412b is 1/2 the length of the long side of the first non-square coding unit 1410 whose height is longer than its width, the depth of the square second coding units 1412a and 1412b is D+1, which deeper than the depth D of the non-square first coding unit 1410 by 1.

[00222] Moreover, the image decoding apparatus 100 can divide the non-square first coding unit 1410 into an odd number of second coding units 1414a, 1414b, and 1414c based on the split-form mode information. An odd number of second coding units 1414a, 1414b, and 1414c may include non-square second coding units 1414a and 1414c and a square second coding unit 1414b. In this case, since the length of the long side of the non-square second coding units 1414a and 1414c and the length of the side of the square second coding unit 1414b are 1/2 the length of the long side of the first coding unit 1410, the depth of the second coding units 1414a, 1414b and 1414c may be D+1, which is deeper than the depth D of the non-square first coding unit 1410 by 1. The image decoding apparatus 100 can determine the depths of the coding units separated from the first coding unit 1420 having a non-square shape whose width is longer than its height using the above-mentioned depth determination method coding units separated from the first coding unit 1410.

[00223] According to an embodiment, the image decoding apparatus 100 can determine a PID for identifying divided coding units based on a size ratio between coding units when an odd number of divided coding units do not have equal sizes. With reference to FIG. 14, a center location coding unit 1414b of an odd number of divided coding units 1414a, 1414b, and 1414c may have a width equal to the width of the other coding units 1414a and 1414c and a height twice the height of the other coding units 1414a and 1414c. That is, in this case, the coding unit 1414b at the central location may include two of the other coding units 1414a or 1414c. Therefore, when the PID of the coding unit 1414b at the central location is 1 based on the scan order, the PID of the coding unit 1414c adjacent to the coding unit 1414b may increase by 2 and thus may be 3. That is, there may be discontinuity in the values PID. According to an embodiment, the image decoding apparatus 100 can determine whether an odd number of divided coding units have equal sizes based on whether there is a discontinuity in the PID to identify the divided coding units.

[00224] According to an embodiment, the image decoding apparatus 100 can determine whether to use a particular partitioning method based on PID values for identifying a plurality of coding units determined by splitting the current coding unit. With reference to FIG. 14, the image decoding apparatus 100 may determine an even number of coding units 1412a and 1412b or an odd number of coding units 1414a, 1414b and 1414c by dividing the first coding unit 1410 having a rectangular shape whose height is longer than its width. The image decoding apparatus 100 may use PIDs indicating respective coding units to identify respective coding units. According to an embodiment, the PID may be obtained from a sample at a predefined location of each coding unit (eg, top left sample).

[00225] According to an embodiment, the image decoding apparatus 100 can determine a coding unit at a predetermined location from the separated coding units, using a PID to distinguish between coding units. According to an embodiment, when the divided shape mode information of the first coding unit 1410 having a rectangular shape whose height is longer than its width indicates that the coding unit is divided into three coding units, the picture decoding apparatus 100 may divide the first coding unit 1410 into three units 1414a, 1414b and 1414c coding. The image decoding device 100 may assign a PID to each of the three coding units 1414a, 1414b, and 1414c. The image decoding apparatus 100 may compare the PIDs of an odd number of divided coding units to determine a coding unit at a central location among the coding units. The image decoding apparatus 100 may determine a coding unit 1414b having a PID corresponding to an average value among the PIDs of coding units as a coding unit at a central location among the coding units determined by dividing the first coding unit 1410. According to an embodiment, the image decoding apparatus 100 may determine a PID for distinguishing between divided coding units based on a size ratio between coding units when the divided coding units do not have equal sizes. With reference to FIG. 14, a coding unit 1414b generated by dividing the first coding unit 1410 may have a width equal to the width of the other coding units 1414a and 1414c and a height twice the height of the other coding units 1414a and 1414c. In this case, when the PID of the coding unit 1414b at the central location is 1, the PID of the coding unit 1414c adjacent to the coding unit 1414b may increase by 2, and thus may be 3. When the PID does not increase evenly as described above, the image decoding apparatus 100 may determine that a coding unit is divided into a plurality of coding units, including a coding unit having a size different from that of other coding units. According to an embodiment, when the split-form mode information indicates to divide a coding unit into an odd number of coding units, the picture decoding apparatus 100 can split the current coding unit such that the coding unit of a predetermined location among the odd number of coding units (for example, central location coding unit) has a different size than other coding units. In this case, the image decoding apparatus 100 may determine the central location coding unit that has a different size using the PID of the coding units. However, the PID and the size or location of the coding unit of the predetermined location are not limited to the above examples, and different PIDs and different locations and sizes of the coding units may be used.

[00226] According to an embodiment, the image decoding apparatus 100 may use a predetermined unit of data, where the coding unit starts to be divided recursively.

[00227] FIG. 15 illustrates that a plurality of coding units are determined based on a plurality of predefined data units included in a picture, according to an embodiment.

[00228] According to an embodiment, a predetermined data unit may be defined as a data unit where the coding unit starts to be recursively divided using split form mode information. That is, the predetermined data unit may correspond to the uppermost depth coding unit, which is used to determine the plurality of coding units separated from the current picture. In the following descriptions, for convenience of explanation, the predefined data unit is referred to as the reference data unit.

[00229] In accordance with an embodiment, a reference data unit may have a predefined size and a predefined shape. According to an embodiment, a reference data unit may include M×N samples. Here, M and N may be equal to each other and may be integers expressed as powers of 2. That is, the reference data unit may have a square or non-square shape and may then be divided into an integer number of coding units.

[00230] According to an embodiment, the image decoding apparatus 100 may divide the current picture into a plurality of reference data units. According to an embodiment, the picture decoding apparatus 100 can separate a plurality of reference data units that are separated from the current picture using the split form mode information of each reference data unit. The split operation of the reference data unit may correspond to a split operation using a quadtree structure.

[00231] According to an embodiment, the image decoding apparatus 100 may previously determine the minimum size allowed for the reference data units included in the current picture. Accordingly, the image decoding apparatus 100 can determine different reference data units having sizes equal to or larger than the minimum size, and can determine one or more coding units using split-form mode information with reference to the specific reference data unit.

[00232] With reference to FIG. 15, the image decoding apparatus 100 may use a square coding reference unit 1500 or a non-square coding reference unit 1502. According to an embodiment, the shape and size of coding reference units may be determined based on various data units, which may include one or more coding reference units (e.g., sequences, pictures, slices, slice segments, tiles, groups of tiles, largest coding units or the like).

[00233] According to an embodiment, a receiver (not shown) of the image decoding apparatus 100 can obtain, from the bitstream, at least one of the coding reference unit shape information and the coding reference unit size information regarding each of the different data units. The operation of dividing the square reference coding unit 1500 into one or more coding units has been described above with respect to the operation of dividing the current coding unit 300 in FIG. 3, and the operation of dividing the non-square reference coding unit 1502 into one or more coding units has been described above with respect to the operation of dividing the current coding unit 400 or 450 of FIG. 4. Thus, their detailed descriptions are omitted here.

[00234] According to an embodiment, the image decoding apparatus 100 may use the PID to identify the size and shape of the coding reference units to determine the size and shape of the coding reference units according to some data units previously determined based on a predetermined condition. That is, a receiver (not shown) can obtain, from the bitstream, only a PID to identify the size and shape of the reference coding units regarding each slice, slice segment, tile, tile group, or largest coding unit, which is a data unit satisfying a predetermined condition (eg, a data unit having a size equal to or smaller than a slice), from various data units (eg, sequences, pictures, slices, slice segments, tiles, tile groups, largest coding units, or the like). The image decoding apparatus 100 may determine the size and shape of the reference data units regarding each data unit that satisfies a predetermined condition using the PID. When the shape information of the reference coding unit and the size information of the reference coding unit are obtained and used from the bitstream corresponding to each data unit having a relatively small size, the utilization efficiency of the bitstream cannot be high, and therefore only the PID can be obtained and used instead of directly obtaining reference coding unit shape information; and reference coding unit size information. In this case, at least one of the size and shape of the reference coding units corresponding to the PID for identifying the size and shape of the reference coding units may have been previously determined. That is, the image decoding apparatus 100 can determine at least one of the size and shape of the coding reference units included in the data unit serving as the unit for obtaining the PID by selecting at least one of the size and shape of the coding reference units previously determined on PID basis.

[00235] According to an embodiment, the image decoding apparatus 100 may use one or more reference coding units included in the largest coding unit. That is, the largest coding unit divided from an image may include one or more reference coding units, and the coding units may be determined by recursively dividing each reference coding unit. According to an embodiment, at least one of the width and height of the largest coding unit may be an integer times larger than at least one of the width and height of the reference coding units. According to an embodiment, the size of the reference coding units can be obtained by dividing the largest coding unit n times based on a quadtree structure. That is, the image decoding apparatus 100 can determine the reference coding units by dividing the largest coding unit n times based on the quadtree structure, and can separate the reference coding unit based on at least one of the block shape information and the divided shape mode information according to various embodiments. .

[00236] FIG. 16 illustrates a processing unit serving as a criterion for determining the determination order of coding reference units included in picture 1600, according to an embodiment.

[00237] According to an embodiment, the image decoding apparatus 100 may determine one or more processing units separated from the picture. A processing unit is a unit of data including one or more reference coding units separated from a picture, and one or more reference coding units included in the processing unit may be determined according to a specific order. That is, the order of determining one or more reference coding units defined in each of the processing units may correspond to one of various types of orders for determining the reference coding units, and may vary depending on the processing unit. The order of determining the reference coding units, which is determined with respect to each processing block, may be one of various orders, such as, but not limited to, raster scan order, Z-scan, N-scan, top-right diagonal scan, horizontal scan, and vertical scan. scan orders.

[00238] According to an embodiment, the image decoding apparatus 100 can obtain processing block size information and can determine the size of one or more processing blocks included in a picture. The image decoding apparatus 100 may obtain processing unit size information from the bitstream, and may determine the size of one or more processing units included in a picture. The processing unit size may be a predetermined data unit size, which is indicated by the processing unit size information.

[00239] According to an embodiment, a receiver (not shown) of the image decoding apparatus 100 can obtain processing block size information from a bitstream in accordance with each particular data unit. For example, the processing unit size information may be obtained from a bitstream in a data unit such as an image, a sequence, a picture, a slice, a slice segment, a tile, a tile group, or the like. That is, a receiver (not shown) can obtain processing block size information from the bitstream according to each of the various data units, and the picture decoding apparatus 100 can determine the size of one or more processing blocks that are separated from the picture using the obtained size information. processing block. The size of the processing blocks may be an integer number of times larger than the size of the coding reference units.

[00240] According to an embodiment, the image decoding apparatus 100 may determine the size of the processing units 1602 and 1612 included in the picture 1600. For example, the image decoding apparatus 100 may determine the size of the processing units based on the size information of the processing unit obtained from the bitstream. With reference to FIG. 16, according to an embodiment, the image decoding apparatus 100 may determine the width of the processing units 1602 and 1612 to be four times the width of the coding reference units, and may determine the height of the processing units 1602 and 1612 to be four times the height of the coding reference units. . The image decoding apparatus 100 may determine the order in which one or more reference coding units are determined in one or more processing units.

[00241] According to an embodiment, image decoding apparatus 100 may determine processing blocks 1602 and 1612 that are included in picture 1600 based on the size of processing blocks, and may determine the order in which one or more reference coding units are determined in processing blocks 1602 and 1612. According to an embodiment, determining the coding reference units may include determining the size of the coding reference units.

[00242] According to an embodiment, the image decoding apparatus 100 may obtain, from the bitstream, determination order information of one or more reference coding units included in one or more processing units, and may determine the determination order with respect to one or more reference coding units on the basis of the received information of the order of determination. The determination order information may be defined as an order or a direction for determining the reference coding units in the processing unit. That is, the order of determining the reference coding units can be independently determined with respect to each processing unit.

[00243] According to an embodiment, the image decoding apparatus 100 can obtain, from the bitstream, information on the determination order of coding reference units according to each particular data unit. For example, a receiver (not shown) can obtain reference coding unit determination order information from a bitstream according to each data unit such as a picture, a sequence, a picture, a slice, a slice segment, a tile, a tile group, a processing unit, or the like. . Because the reference coding unit determination order information indicates an order for determining the reference coding units in a processing unit, determination order information can be obtained with respect to each specific data unit including an integer number of processing units.

[00244] According to an embodiment, the image decoding apparatus 100 may determine one or more reference coding units based on a certain determination order.

[00245] According to an embodiment, a receiver (not shown) may obtain coding reference unit determination order information from the bitstream as information related to processing units 1602 and 1612, and the image decoding apparatus 100 may determine the determination order of one or more reference units coding units included in processing blocks 1602 and 1612 and may determine one or more coding reference units that are included in picture 1600 based on the order of determination. With reference to FIG. 16, image decoder 100 may determine determination orders 1604 and 1614 of one or more reference coding units in processing blocks 1602 and 1612, respectively. For example, when reference coding unit determination order information is obtained with respect to each processing unit, different types of reference coding unit determination order information may be obtained for processing units 1602 and 1612. When the reference coding unit determination order 1604 in the processing block 1602 is a raster scan order, the reference coding units included in the processing block 1602 may be determined according to the raster scan order. In contrast, when the reference coding unit determination order 1614 in the other processing block 1612 is an inverse bitmap scan order, the reference coding units included in the processing block 1612 may be determined according to the inverse bitmap scan order.

[00246] According to an embodiment, the image decoding apparatus 100 may decode certain one or more coding reference units. The image decoding apparatus 100 may decode the image based on the coding reference units determined as described above. The coding reference unit decoding method may include various image decoding methods.

[00247] According to an embodiment, the image decoding apparatus 100 may obtain, from the bitstream, block shape information indicating the shape of the current coding unit, or split mode information indicating the division method of the current coding unit, and may use the obtained information. Split-form mode information may be included in a bitstream related to different data units. For example, the image decoding apparatus 100 may use split-form mode information included in a sequence parameter set, a picture parameter set, a video parameter set, a slice header, a slice segment header, a tile header, or a tile group header. Moreover, the image decoding apparatus 100 can obtain, from the bitstream, a syntax element corresponding to the block shape information or split form mode information according to each largest coding unit, each reference coding unit, or each processing unit, and can use the obtained syntax element.

[00248] Next, a method for determining a split rule according to an embodiment of the disclosure will be described in detail.

[00249] The image decoding device 100 may determine the image division rule. The division rule may be predetermined between the image decoding apparatus 100 and the image encoding apparatus 150 . The image decoding apparatus 100 may determine an image division rule based on information obtained from the bitstream. The image decoding apparatus 100 may determine a separation rule based on information obtained from at least one of a sequence parameter set, a picture parameter set, a video parameter set, a slice header, a slice segment header, a tile header, and a tile group header. The image decoding apparatus 100 may determine the division rule differently according to frames, slices, temporal levels, largest coding units, or coding units.

[00250] The image decoding apparatus 100 may determine the separation rule based on the shape of the coding unit block. The block shape may include the size, shape, width-to-height ratio, and direction of the coding unit. The image encoding apparatus 150 and the image decoding apparatus 100 may predetermine that a separation rule should be determined based on the shape of the coding unit block. However, disclosure is not limited to this. The image decoding apparatus 100 may determine a separation rule based on information obtained from the bitstream received from the image encoding apparatus 150 .

[00251] The shape of the coding unit may include square and non-square. When the width and height lengths of the coding unit are equal, the image decoding apparatus 100 may determine the shape of the coding unit as a square. Also, when the width and height lengths of the coding unit are not equal, the image decoding apparatus 100 may determine the shape of the coding unit as non-square.

[00252] The coding unit size may include various sizes such as 4x4, 8x4, 4x8, 8x8, 16x4, 16x8, and up to 256x256. The size of a coding unit may be classified based on the length of the long side of the coding unit, the length of the short side, or the area. The image decoding apparatus 100 may apply the same separation rule to coding units classified as the same group. For example, the image decoding apparatus 100 may classify coding units having the same long side lengths as having the same size. Also, the image decoding apparatus 100 may apply the same division rule to coding units having the same long side lengths.

[00253] The width-to-height ratio of the coding unit may include 1:2, 2:1, 1:4, 4:1, 1:8, 8:1, 1:16, 16:1, or the like. Also, the direction of the coding unit may include a horizontal direction and a vertical direction. The horizontal direction may indicate the case in which the length of the width of the coding unit is longer than the length of its height. The vertical direction may indicate the case in which the length of the width of the coding unit is shorter than the length of its height.

[00254] The image decoding apparatus 100 can adaptively determine the division rule based on the size of the coding unit. The image decoding apparatus 100 may determine the allowed split-form mode differently based on the size of the coding unit. For example, the image decoding apparatus 100 may determine whether splitting is allowed based on the size of the coding unit. The image decoding apparatus 100 may determine the division direction according to the size of the coding unit. The image decoding apparatus 100 may determine the allowed split type based on the coding unit size.

[00255] The division rule determined based on the size of the coding unit may be a division rule predetermined between the image encoding apparatus 150 and the image decoding apparatus 100. Also, the image decoding apparatus 100 may determine the separation rule based on the information obtained from the bitstream.

[00256] The image decoding device 100 can adaptively determine the separation rule based on the location of the coding unit. The image decoding apparatus 100 can adaptively determine the split rule based on the location of the coding unit in the image.

[00257] Also, the image decoding apparatus 100 may determine a division rule such that coding units generated by different division paths do not have the same block shape. However, the disclosure is not limited to this, and coding units generated by different split paths may have the same block shape. Encoding units generated by different split paths may have different decoding processing orders. Since the decoding processing orders are described above with reference to FIG. 12, their details are omitted here.

[00258] Next, with reference to FIG. 17-29, according to various embodiments provided in the present specification, the process of performing intra prediction, and the encoding and decoding of the specific intra prediction mode of each block will be described in detail. The intra-prediction process according to various embodiments may be performed by the decoder 120 of the image decoding apparatus 100 of FIG. 1A and the encoder 155 of the image encoding apparatus 150 of FIG. 2A. In particular, the intra prediction process according to various embodiments may be performed by the intra predictor 6400 of the image decoder 6000 of FIG. 1D and the intra predictor 7200 of the image encoder 7000 of FIG. 2D.

[00259] FIG. 17 illustrates intra prediction modes according to an embodiment, and FIG. 18 illustrates intra prediction modes according to another embodiment.

[00260] The intra-prediction modes according to various embodiments may include a non-angular intra-prediction mode including a planar mode and a DC mode that are non-directional, and an angular intra-prediction mode that is directional. The non-angular mode may include planar mode and bilinear mode, as well as planar mode and DC mode.

[00261] With reference to FIG. 17 and 18, the intra-prediction angular mode includes intra-prediction modes indicating specific directions in a range between -135 degrees and -180 degrees and a range between 45 degrees and 180 degrees with respect to the 45 degrees and -135 degrees directions.

[00262] In the descriptions below, prediction direction angles in the range between 0 degrees and 180 degrees, which indicate directions in quadrants I and II, can be represented as +, and prediction direction angles in the range between -180 degrees and 0 degrees, which indicate directions in quadrants III and IV can be represented as -. The predefined angle -a (where "a" is a positive real number) indicating the direction in quadrants III and IV corresponds to the angle (360-a) degrees. For example, a direction of -135 degrees corresponds to a direction of 225 degrees, and a direction of -180 degrees corresponds to a direction of 180 degrees.

[00263] Prediction directions, represented as arrows shown in FIG. 17 and 18 indicate directions of adjacent pixels to be used in intra-prediction with respect to the current pixel of the current block to be intra-prediction. The numbers marked in Fig. 17 and 18 are examples of intra-prediction mode indices according to intra-prediction directions. Further, the intra prediction mode index may be referred to as predModeIntra. Planar mode PredModeIntra and DC mode predModeIntra, which are non-angular intra prediction modes, can be set to 0 and 1, respectively.

[00264] With reference to FIG. 17, the intra prediction angle modes according to the embodiment may include 33 intra prediction modes obtained by dividing the interval between 45 degrees and -135 degrees by 33. The 33 intra prediction angle modes may sequentially have predModeIntra values from 2 to 34 in a clockwise direction from the direction of -135 degrees. For example, in FIG. 17, an intra prediction mode for which predModeIntra is 2 may indicate an intra prediction mode indicating a diagonal direction in the -135 degree direction, an intra prediction mode for which predModeIntra is 10 may indicate an intra prediction mode indicating a horizontal direction direction -180 (180) degrees, an intra-prediction mode for which predModeIntra is 26 may indicate an intra-prediction mode indicating a vertical direction in the direction of 90 degrees, and an intra-prediction mode for which predModeIntra is 34 may indicate a mode intra-prediction indicating a diagonal direction in the direction of 45 degrees.

[00265] With reference to FIG. 18, the intra-prediction angular modes according to another embodiment may include 65 intra-prediction modes obtained by dividing the interval between -135 degrees and -180 degrees and the interval between 45 degrees and 180 degrees with respect to the directions 45 degrees and -135 degrees by 65. The 65 intra-prediction angular modes can sequentially have predModeIntra values from 2 to 66 in a clockwise direction from the -135 degree direction. For example, in FIG. 18, an intra prediction mode for which predModeIntra is 2 may indicate an intra prediction mode indicating a diagonal direction in the -135 degree direction, an intra prediction mode for which predModeIntra is 18 may indicate an intra prediction mode indicating a horizontal direction direction -180 (180) degrees, an intra-prediction mode for which predModeIntra is 50 may indicate an intra-prediction mode indicating a vertical direction in a direction of 90 degrees, and an intra-prediction mode for which predModeIntra is 66 may indicate a mode intra-prediction indicating a diagonal direction in the direction of 45 degrees.

[00266] However, the predModeIntra values of the intra prediction modes are not limited to the values shown in FIG. 17 and 18 and are subject to change. For example, the number of intra prediction angle modes in the clockwise direction from the 45 degree direction may not be limited to 33 or 65 and may be changed, the values of predModeIntra intra prediction angle modes may be successively set in the counterclockwise direction from the 45 degree direction, and set predModeIntra values can also change. The intra-prediction angular modes are not limited to this, and may include a predefined number of intra-prediction modes indicating specific directions in the range between an arbitrary value of A degrees (where "A" is a real number) and B degrees (where "B" is a real number ).

[00267] The intra prediction modes described with reference to FIG. 17 and 18, are installed taking into account the square shape. However, as described above with reference to FIG. 3-5, according to an embodiment, the data units including a coding unit, a prediction unit, and a transformation unit may each have a square shape or a non-square shape. Also, according to the 4:2:2 format, even when a luma component block is square, a chrominance component block corresponding to it may be non-square. Also, according to an embodiment, the data unit to be used in intra-prediction may not have a fixed size as a macroblock data unit according to the related art, but may have different sizes.

[00268] In accordance with an embodiment, an intra prediction mode candidate to be used in the intra prediction of the current block may adaptively change based on at least one of the size and shape of the current block.

[00269] In detail, according to an embodiment, the directions and the number of intra-prediction modes applicable to the current block may be adaptively set proportional to the size of the current block to be intra-prediction. The number of intra-prediction modes that are applicable to the current block may increase in proportion to the size of the current block. Also, according to an embodiment, blocks can be grouped according to their sizes, and the number of intra prediction modes applicable to a group of large blocks can be increased. For example, when the current block size is equal to or less than 8×8, the minimum number a (where a is a positive integer) of intra-prediction modes, the number b (where a is a positive integer, b>a) of intra-prediction modes can be applied. prediction may be applied to blocks of 16×16 and 32×32, and the number c (where a is a positive integer, c>b) of intra-prediction modes may be applied to blocks equal to or greater than 64×64.

[00270] On the other hand, according to another embodiment, the directions and the number of intra-prediction modes applicable to the current block can be adaptively set inversely proportional to the size of the current block to be intra-prediction. That is, the number of intra-prediction modes applicable to the current block may decrease in proportion to the size of the current block. Also, according to an embodiment, blocks can be grouped according to their sizes, and the number of intra prediction modes applicable to a group of large blocks can be reduced. For example, when the current block size is equal to or less than 8×8, the maximum number c of intra prediction modes may be applied, the number b of intra prediction modes may be applied to blocks of 16×16 and 32×32, and the number a of intra prediction modes can be applied to blocks equal to or greater than 64x64.

[00271] In accordance with another embodiment, the number of intra-prediction modes to be applied to blocks of all sizes may be equal, regardless of block sizes.

[00272] Also, according to another embodiment, the directions and number of intra prediction modes to be applied to the current block may be adaptively set based on the shape of the current block or the height and width of the current block. In detail, when the current block has a square shape as described above with reference to FIG. 17 and 18, predefined intra-prediction modes may be used, and when the current block is non-square, the intra-prediction modes may be set to accurately indicate one of the height direction and the width direction.

[00273] FIG. 19 is a diagram for describing intra prediction modes to be applied to a non-square shape, according to various embodiments.

[00274] With reference to FIG. 19, the intra prediction modes to be applied to the non-square block 1900 include vertical portion intra prediction modes configured by dividing the angles between the direction indicated by the first intra prediction mode 1910 and the direction indicated by the second intra prediction mode 1920 , and horizontal part intra-prediction modes configured by dividing the angles between the direction indicated by the first intra-prediction mode 1910 and the direction indicated by the third intra-prediction mode 1930, based on the first intra-prediction mode 1910 in the direction indicating the upper left vertex from the block center C, a second intra-prediction mode 1920 in a direction indicating the upper right vertex from the block center C, and a third intra prediction mode 1930 in a direction indicating the lower left vertex from the block center C. The number of intra-prediction modes of the horizontal portion and the number of intra-prediction modes of the vertical portion may be set based on the width and height of the block 1900. For a block having a non-square shape, the number of intra prediction modes indicating the longer side may be set larger than the number of intra-prediction modes indicating the shorter side. For example, as illustrated in FIG. 19, for a non-square block 1900 whose width is larger than its height, the number of vertical part intra-prediction modes can be set to be larger than the number of horizontal part intra-prediction modes.

[00275] When determining the number of vertical part intra-prediction modes, the first intra-prediction mode 1910 and the second intra-prediction mode 1920 may be included or excluded from the vertical part intra-prediction modes. Similarly, when determining the number of horizontal part intra-prediction modes, the first intra-prediction mode 1910 and the third intra-prediction mode 1930 may be included or excluded from the horizontal part intra-prediction modes. For example, for a 32×16 block whose width is 32 and whose height is 16, it is assumed that the number of vertical part intra-prediction modes in the width direction is 16, and the number of horizontal part intra-prediction modes in the height direction is 8. In this case, all 25 intra-prediction modes, including 16 vertical part intra-prediction modes between the first intra-prediction mode 1910 and the second intra-prediction mode 1920, and 8 horizontal part intra-prediction modes between the second intra-prediction mode 1920 and the third mode 1930 intra-prediction, in addition to the first intra-prediction mode 1910, may be defined as the intra-prediction modes applicable to the current block 1900. Alternatively, all 27 intra-prediction modes, including 16 vertical part intra-prediction modes and 8 intra-prediction modes prediction of the horizontal part, in addition to the first intra-prediction mode 1910, the second intra-prediction mode 1920, and the third re The intra prediction mode 1930 may be defined as the intra prediction modes applicable to the current block 1900. The specific number of intra prediction modes may vary.

[00276] On the other hand, for a block having a non-square shape, the number of intra-prediction modes indicating the longer side can be set to be less than the number of intra-prediction modes indicating the shorter side. For example, in a manner opposite to the descriptions above, in FIG. 19, the number of horizontal part intra-prediction modes can be set larger than the number of vertical part intra-prediction modes.

[00277] According to various embodiments, the horizontal intra-prediction mode in the 180-degree direction and the vertical intra-prediction mode in the 90-degree direction are generally defined as intra-prediction modes, so that the intra-prediction modes can be set to compactly indicate horizontal direction in the direction of 180 degrees or vertical direction in the direction of 90 degrees.

[00278] Next, a process for encoding and decoding intra prediction mode information according to various embodiments will be described.

[00279] The encoder 155 of the image encoding apparatus 150 of FIG. 2A and the intra predictor 7200 of the image encoder 7000 of FIG. 2D determine the intra-prediction mode in which the RD cost is optimal by applying the intra-prediction modes in accordance with various embodiments. When the prediction mode of the current block is finally determined to be the intra prediction mode, a plurality of pieces of information about which prediction mode of skip mode, inter prediction mode, and intra prediction mode is used to predict the current block, and intra prediction mode information of the predicted current block are included in the bitstream and then transmitted to the image decoding apparatus 100 . The decoder 120 of the image decoding apparatus 100 according to FIG. 1A and the intra predictor 6400 of the image decoder 6000 of FIG. 1D may determine the intra-prediction mode of the current block using information about the intra-prediction mode of the current block, the information is included in the bitstream.

[00280] As described above, all of the 35 or 67 intra-prediction modes included in the two non-angular modes for DC mode and planar mode, and 33 or 65 angular prediction modes can be used. As the number of intra prediction modes increases, the amount of information for indicating the intra prediction mode of the current block may increase. In general, when an image is processed by block division, the current block and its adjacent block have a high probability of similar image characteristics. Therefore, there is a high probability that the intra-prediction mode of the intra-predicted current block is equal to or similar to the intra-prediction mode of the adjacent block. According to various embodiments, based on the fact that adjacent blocks have a high probability of similar characteristics between them, an intra prediction mode candidate list including candidate intra prediction modes can be obtained using the adjacent block prediction mode information of the current block. block, wherein the intra-prediction modes of the candidate have a high probability of being the intra-prediction mode of the current block. Further, the intra prediction mode candidate list obtained using adjacent block prediction mode information may be referred to as a most likely mode list (MPM).

[00281] When the intra prediction mode of the current block is in the MPM list, the number of bits required to signal the intra prediction mode of the current block can be reduced. For example, when the number of all intra prediction modes is 67, at least 7 bits are required to signal one of the 67 intra prediction modes. However, when 5 or 6 MPM lists are used, there is a high possibility that the intra prediction mode of the current block is determined to be in the MPM lists, and even when the intra prediction mode of the current block is not included in the MPM lists, the remaining intra prediction modes may be signaled with using only 6 bits except for 5 or 6 MPM lists. Therefore, when the MPM list is used, the number of all bits required to signal the intra-prediction mode of an intra-predicted block of blocks constituting a picture can be reduced.

[00282] FIG. 20 is a reference diagram for describing a process for obtaining an MPM list using adjacent block prediction mode information, according to various embodiments.

[00283] With reference to FIG. 20, the MPM list may be obtained using the left adjacent block prediction mode A 2020 and the upper adjacent block prediction mode B 2030, which are processed prior to the current block 2010. The left adjacent block 2020 may be a block including a pixel 2021 located to the left of the bottom left pixel located at the bottom left vertex of the current block 2010. It is assumed that the location of the top left pixel of the current block is (0,0), the x coordinate value increases in the right direction, and the y coordinate value increases in the downward direction, and the size of the current block 2010 is defined as width × height. In this case, the location of the pixel at the bottom right vertex of the current block 2010 is (width-1, height-1). When the location of the bottom left pixel located at the bottom left vertex of the current block 2010 is (0, height-1), the block including the pixel 2021 at location (-1, height -1) may be determined as the left adjacent block 2020. The top adjacent block 2030 is a block including a pixel 2031 located above the top right pixel located at the top right vertex of the current block 2010. When the location of the top right pixel located at the top right vertex of the current block 2010 is (width-1, 0 ), a block including a pixel at a location (width -1, -1) may be defined as an upper adjacent block 2030. Further, it is assumed that 67 intra-prediction modes are used, including two non-angular intra-prediction modes (planar and DC) and 65 intra-prediction angular modes as shown in FIG. 18, and planar mode predModeIntra is 0, DC mode predModeIntra is 1, and predModeIntra 2-66 are set in the clockwise direction to intra prediction angular modes. As described above, predModeIntra of the intra prediction mode indicating the horizontal direction (H) may be set to 18, and predModeIntra of the intra prediction mode indicating the vertical direction (V) may be set to 50. Also, it is assumed that 6 candidates of the intra prediction mode -predictions are included in the MPM list.

[00284] According to an embodiment, first, the availability of the left adjacent block 2020 and the top adjacent block 2030 is checked. , the adjacent block intra-prediction mode determined to be unavailable is set to planar mode, for which predModeIntra is 0, by default. When an adjacent block is included in the same tile or slice as the current block 2010 and is intra-predictable, the intra-prediction mode of the adjacent block is permanently set to the intra-prediction mode of the adjacent block. When the intra-prediction modes of the left adjacent block 2020 and the upper adjacent block 2030 are all non-angular intra-prediction modes, i.e., planar mode or DC mode, the MPM list may include {planar, DC, H, V, V+4, V-4} or may include {planar, DC, H, V, H+4, H-4}. H denotes a horizontal intra-prediction mode, and V denotes a vertical intra-prediction mode. For example, in the case where the intra-prediction mode of the left adjacent block 2020 is the intra-prediction DC mode (predModeI tiles ntra=1) and the top adjacent block 2030 is planar mode (predModeInta=0), the MPM list may include itself {0, 1, 50, 18, 46, 54} or {0, 1, 50, 18, 14, 22}.

[00285] In the case where one of the intra-prediction modes of the left adjacent block 2020 and the upper adjacent block 2030 is the non-angular intra-prediction mode and the other mode is the angular intra-prediction mode, the larger index of the intra-prediction mode of the indices A and B intra-prediction modes of the left adjacent block 2020 and the upper adjacent block 2030 are set to maxAB. That is, when the predModeIntra of the intra prediction mode of the left adjacent block 2020 is assumed to be A and the predModeIntra of the intra prediction mode of the upper adjacent block 2030 is B, maxAB=Max(A, B). In this case, the MPM list may include {planar, maxAB, DC, maxAB-1, maxAB+1, maxAB-2}. For example, in the case where the intra prediction mode of the left adjacent block 2020 has an intra prediction mode index of 60 (predModeIntra=60) and the upper adjacent block 2030 is DC mode (predModeInta=1), maxAB=Max(60, 1) =60 and the MPM list includes {0, 60, 1, 59, 61, 58}.

[00286] When the intra prediction modes of the left adjacent block 2020 and the upper adjacent block 2030 are all intra prediction angular modes and are not the same intra prediction modes, the MPM list may be set based on the angular difference between the intra prediction modes the left adjacent block 2020 and the upper adjacent block 2030. When the value of the difference (OK?) between predModeIntra (A) of the left adjacent block 2020 and predModeIntra (B) of the upper adjacent block 2030 is within a predefined range, such as between 2 and 62, the MPM list may include {planar, A, B, DC, maxAB-1, maxAB+1}. For example, in the case where the intra-prediction mode of the left adjacent block 2020 has predModeIntra 60 and the upper adjacent block 2030 has predModeIntra 50, the difference value between predModeIntra (A) of the left adjacent block 2020 and predModeIntra (B) of the upper adjacent block 2030 is included in the range 2 to 60, and thus the MPM list includes {0, 60, 50, 1, 59, 61}.

[00287] In the case where the difference value between predModeIntra (A) of the left adjacent block 2020 and predModeIntra (B) of the upper adjacent block 2030 is less than 2 or greater than 62, the MPM list may include {planar, A, B, DC, maxAB- 2,maxAB+2}. For example, in the case where the intra prediction mode of the left adjacent block 2020 has predModeIntra 3 and the top adjacent block 2030 has predModeIntra 4, the MPM list includes {0, 3, 4, 1, 2, 6}.

[00288] When the intra prediction modes of the left adjacent block 2020 and the upper adjacent block 2030 are all angular intra prediction modes and the same intra prediction modes, the MPM list may include {planar, A, A-1, A +1, DC mode, A-2} or {planar, B, B-1, B+1, DC mode, B-2}. For example, when the intra prediction modes of left adjacent block 2020 and top adjacent block 2030 all have predModeIntra 60, the MPM list may include {0, 60, 59, 61, 1, 58}.

[00289] Various tools, including a multi-reference row extension that selectively uses not only adjacent samples adjacent to the current block but also adjacent samples removed from the current block by a predetermined distance, intra- a sub-partition in which a block to be intra-prediction is divided into sub-partitions, a hybrid prediction method where inter-prediction and intra-prediction are combined, or the like can be used in the encoding/decoding process of the current block. To reduce complexity, the MPM list may be selectively set according to the tool used in the encoding process of the current block. For example, when multi-reference line expansion is used in the current block encoding process, the planar mode and the DC mode may be excluded from the MPM list, and when intra-subdivision is used, the DC mode may be excluded from the MPM list. For a block for which neither multi-reference row expansion nor intra-subdivision is used, the planar mode and the DC mode are included in the MPM list, so that the difficulty of establishing the MPM list can be reduced. However, when the MPM list generation scheme is changed according to whether or not a specific tool is used, the possibility that an intra-prediction mode biased towards a specific tool should be selected may increase.

[00290] According to an embodiment, the MPM list may be selectively used based on the encoding information of the intra-predicted current block. In other words, according to an embodiment, it is not the case that the MPM list is used for the entire intra-predicted current block, or the intra-prediction mode of the current block is determined from candidate intra-prediction modes included in the MPM list. Only when the encoding information of the current block satisfies a specific condition, the MPM list may be used, or the intra prediction mode of the current block may be determined from the candidate intra prediction modes included in the MPM list.

[00291] According to an embodiment, when encoding information related to an intra-predicted block satisfies a predetermined condition, an MPM list may be generated without special flag information. When the encoding information related to the intra-predicted block does not satisfy a predetermined condition, special flag information regarding whether to generate an MPM list for the intra-predicted block may be signaled. Also, according to an embodiment, before generating the MPM list, it may first be determined whether the intra prediction mode of the current block is a particular intra prediction mode (e.g., non-angular mode), and then if the intra prediction mode of the current block is not is a specific intra prediction mode, an MPM list may be generated, and the intra prediction mode of the current block may be determined using an MPM index (MPM idx) indicating one of the candidate intra prediction modes included in the MPM list. Also, whether or not to apply the coding tool to be used for the current block may be determined from the intra prediction mode candidates included in the MPM list. According to another embodiment, the MPM list of the current block may equally be generated regardless of the encoding information related to the current block. The encoding information may include information on whether to apply a predetermined encoding tool applied to the current block, reference sample information to be used in intra-prediction with respect to the current block, and sub-split information indicating whether the current block is to be divided into sub-partitions.

[00292] FIG. 21 is a flowchart of an MPM list generation process according to the embodiment, and FIG. 22 is a reference sample diagram according to the embodiment.

[00293] With reference to FIG. 21, at operation 2110, it is determined, based on the encoding information of the current block, whether the intra prediction mode of the current block is to be determined from the intra prediction mode candidate list obtained using a plurality of pieces of adjacent block prediction mode information adjacent to the current block. That is, whether or not to use the MPM list may be determined based on encoding information related to the current block. The encoding information may include reference sample information to be used in intra-prediction about the current block and sub-split information indicating whether the current block is to be sub-splitted. According to various embodiments, not only a pixel adjacent to the current block, but also a pixel remote from the current block by a predetermined distance can be used as a reference sample in intra-prediction. With reference to FIG. 22, not only pixels 2210 immediately adjacent to the current block 2200, but also pixels 2220 and 2230 a predetermined distance from the top border and left border of the current block 2200 can be used as a reference sample in intra-prediction. Reference sample information indicating a reference sample of adjacent pixels 2210, 2220, and 2230 of the current block 2200 may be signaled from an encoder to a decoder.

[00294] The predetermined condition for determining whether the intra-prediction mode of the current block should be determined using the MPM list may be set differently. For example, the image decoding apparatus 100 may obtain reference sample information and sub-splitting information from the bitstream, may determine, based on the reference sample information, (a) whether an adjacent pixel immediately adjacent to the current block is to be used as the reference sample of the current block. , and may determine, based on the sub-split information, (b) whether the current block is to be sub-splitted. Thereafter, the image decoding apparatus 100 may determine, based on the results of determinations (a) and (b), whether one of the candidate intra prediction modes included in the MPM list is to be used as the intra prediction mode of the current block. Also, according to the embodiment, specific flag information indicating whether one of the candidate intra prediction modes included in the MPM list is to be used in the intra prediction mode of the current block can be set. Even when the specific flag is set, in the case where the specific non-angular prediction mode flag is set indicating whether the intra prediction mode of the current block is the specific non-angular prediction mode and the intra prediction mode of the current block is the specific non-angular mode prediction, the intra-prediction mode of the current block can be determined without using the MPM list.

[00295] As a result of determining in operation 2110 when (a') an adjacent pixel immediately adjacent to the current block is not to be used as a reference sample of the current block, or (b') the current block is to be sub-divided, it is determined, that the MPM list is to be used, and in operation 2120, the image decoding apparatus 100 generates MPM candidates to be included in the MPM list. That is, at least one of the condition (a') or condition (b') is satisfied, the image decoding apparatus 100 determines to use the MPM list.

[00296] As a result of determining in operation 2110 when (a'') an adjacent pixel immediately adjacent to the current block is to be used as a reference sample of the current block, and (b'') the current block is not to be sub-divided, in operation 2150, the image decoding apparatus 100 obtains, from the bitstream, intra prediction mode candidate list flag information (intra_luma_mpm_flag) indicating whether to use the MPM list. In operation 2160, the image decoding apparatus 100 may determine whether to use the MPM list based on the obtained intra prediction mode candidate list flag information (intra_luma_mpm_flag). For example, when the intra prediction mode candidate list flag information (intra_luma_mpm_flag) corresponds to 1, the image decoding apparatus 100 can generate MPM candidates to be included in the MPM list. When the intra-prediction mode candidate list flag information (intra_luma_mpm_flag) is 0, in operation 2170, the picture decoding apparatus 100 obtains, from the bitstream, intra-prediction residual mode (intra_luma_mpm_remainder) information of the current block, and determines the intra-prediction mode of the current block using residual mode information of intra-prediction. The intra prediction mode residual information indicates one of the intra prediction modes, which are not included in the MPM list, from the intra prediction modes applicable to the current block. According to an embodiment, if the predetermined condition is satisfied, the image decoding apparatus 100 may decide to unconditionally use the MPM list, and even if the predetermined condition is not satisfied, the image decoding apparatus 100 may determine whether to use the MPM list based on a flag specifically indicating whether to use the MPM list.

[00297] When at least one of the conditions of (a') or (b') described above is satisfied, or the intra prediction mode candidate list flag information (intra_luma_mpm_flag) indicates that the MPM list is to be used, in operation 2120 described above, the image decoding apparatus 100 generates an MPM list including MPM candidates. In operation 2130, the image decoding apparatus 100 obtains MPM index information (MPM idx) indicating one of the intra prediction mode candidates included in the MPM list.

[00298] According to an embodiment, the image decoding apparatus 100 obtains non-angular intra prediction mode information indicating whether the intra prediction mode of the current block is a specific non-angular intra prediction mode. The specific non-angular intra prediction mode may be one of the non-angular intra prediction modes, including DC mode, planar mode, flat mode, bilinear mode, or the like. When the non-angular intra prediction mode information indicates a specific non-angular intra prediction mode, the image decoding apparatus 100 determines the intra prediction mode of the current block as the specific non-angular intra prediction mode, and when the non-angular intra prediction mode information does not indicate a specific non-angular intra prediction mode, the image decoding apparatus 100 obtains, from the bitstream, intra prediction mode index information indicating such in the intra prediction mode candidate list obtained based on the prediction mode information of an adjacent block adjacent to the current block. Thereafter, the image decoding apparatus 100 may determine the intra prediction mode of the current block using the obtained intra prediction mode index (MPM idx) information, and may perform intra prediction on the current block using the intra prediction mode of the current block. The reason why it is determined whether the mode is planar before obtaining the MPM index information is that, in many cases, the planar mode is determined as the intra-prediction mode.

[00299] The number of intra prediction mode candidates included in the MPM list may vary. For example, the number of intra prediction mode candidates to be included in the MPM list may be determined to be proportional to or inversely proportional to the size of the current block. According to another embodiment, the intra prediction mode information may include i) information indicating the portion to which the intra prediction mode of the current block belongs, from a horizontal portion and a vertical portion, and ii) information indicating one of the intra prediction modes. predictions included in this part. Returning to FIG. 19, the image encoding device 150 may add, to the bitstream, information about which part the intra prediction mode of the current block belongs to, among the vertical part intra prediction modes and the horizontal part intra prediction modes. For example, which part the intra prediction mode of the current block belongs to, among vertical part intra prediction modes and horizontal part intra prediction modes, can be represented using flag information of 1 bit. The first intra-prediction mode 1910 with a direction of 135 degrees may be included in a predefined part of a horizontal part and a vertical part. Information indicating one of the intra-prediction modes included in the part may be represented using MPM, or may be represented as a value from 0 to (n-1), where this value indicates one of n intra-prediction modes (where n is a positive integer) included in this part. The image decoding apparatus 100 may first obtain information indicating the part to which the intra prediction mode of the current block belongs from the horizontal portion and the vertical portion, and then may determine the intra prediction mode of the current block using information indicating one of the intra prediction modes, included in this part.

[00300] When the image encoding apparatus 150 sets the MPM list according to various embodiments and adds the intra prediction mode of the current block to the bitstream using the MPM list, the image encoding apparatus 150 may separately include information indicating the portion to which the mode belongs. intra-predictions of the current block, from the horizontal part and the vertical part.

[00301] Also, according to another embodiment, information indicating the part to which the intra-prediction mode of the current block belongs, from the horizontal part and the vertical part, may not be separately included in the bitstream, and the intra-prediction mode of the current block may be determined using the width and height information and the size information of the current block, and the intra-prediction mode information of the adjacent block. For example, when the height of the current box is larger than its width, the intra-prediction mode of the current box may be defined as one of the intra-prediction modes of the vertical part, and when the width of the current box is larger than its height, the intra-prediction mode of the current box may be defined as one of the intra-prediction modes of the horizontal part.

[00302] According to another embodiment, the intra-prediction mode of the current block may be represented using a two-dimensional vector (vx, vy) (where vx, vy are each a real number) indicating the direction of a reference pixel from the current pixel to be intra-prediction.

[00303] FIG. 23 is a reference diagram for describing a method for representing the intra prediction mode as a vector, according to another embodiment. With reference to FIG. 23, it is assumed that the current pixel is predicted using a reference pixel spaced apart along the horizontal W axis and the vertical H axis. Since all pixels in the block have the same intra prediction direction, the prediction direction indicated by the intra prediction mode can be represented as a two-dimensional vector 2320 (W, H). Instead of a 2D vector (W, H) indicating the intra prediction mode, the vector (vx, vy) 2310 can be used as a representative vector whose value is 1 and which points in the same direction as the 2D vector (W, H). That is, the 2D vector (W, H) can be normalized so that vx ² +vy ² is 1, so that the 2D vector (vx, vy) 2310 indicating the intra-prediction mode of the current block can be obtained. Thus, when a two-dimensional vector (vx, vy) is used as the intra prediction mode information, different prediction directions can be indicated, compared to the intra prediction modes in the predetermined direction that is set before.

[00304] According to an embodiment, the number and type of intra prediction modes may change according to the MPM index or intra prediction modes included in the MPM list. For example, when the MPM list includes an intra-prediction mode for which the value of predModeIntra is 50, intra-prediction modes in the same direction as the intra-prediction mode for which the value of predModeIntra is 50 may be further included in candidate intra-prediction modes. Also, the MPM list may be divided into a predetermined number of groups according to predModeIntra values included in the MPM list, and preset intra prediction modes may be determined according to the groups of the MPM list.

[00305] According to an embodiment, the number of intra prediction modes may be determined based on a quantization parameter (QP) value. For example, the number of available intra-prediction modes may be determined as inversely proportional to the QP value of the current block. Also, when the QP value of the current block is less than a predetermined threshold, the number of available intra prediction modes can be set to M (where M is a positive integer), and when the QP value of the current block is equal to or greater than the predetermined threshold, the number of available intra-prediction modes can be set to N (where M>N, N is a positive integer).

[00306] According to an embodiment, intra prediction modes may be included in the MPM list according to a predefined priority order. It is assumed that when N intra-prediction modes are included in the MPM list, the MPM index (MPM idx) indicating one of the N candidates may have an integer value from 0 to (N-1), and when the value of the MPM index (MPM idx) reduced, the intra-prediction mode for it is the mode having the higher priority. According to an embodiment, the order of priorities of the intra prediction modes included in the MPM list may be determined based on the frequencies of the intra prediction modes of adjacent blocks. For example, higher MPM list priorities, ie, smaller MPM indices, may be set in order of higher frequencies of adjacent block intra-prediction modes.

[00307] In accordance with another embodiment, the order of priorities of intra-prediction modes of adjacent blocks included in the MPM list may be determined, taking into account the sizes and shapes of the current block and adjacent blocks.

[00308] FIG. 24A-24C are reference diagrams for describing the priority order of intra prediction modes of adjacent blocks included in the MPM list, given the sizes of the current block and adjacent blocks.

[00309] In accordance with another embodiment, the intra-prediction mode of an adjacent block having a size similar to that of the current block may be prioritized in the MPM list. With reference to FIG. 24A, from the left adjacent block 2410 and the upper adjacent block 2420 of the current block 2400, the intra-prediction mode of the left adjacent block 2410 having the same size as the current block 2400 can be set to be higher priority in the MPM list, compared to the intra-prediction mode of the upper adjacent block 2420.

[00310] Also, the intra-prediction mode of an adjacent block having a shape similar to the current block can be set to higher priority in the MPM list. With reference to FIG. 24B, when the current block 2400 has a non-square shape whose width is greater than its height, the intra-prediction mode of the left adjacent block 2430 having a non-square shape whose width is greater than its height, which is similar to the current block 2400, from the left adjacent block 2430 and the upper adjacent block 2440 may be set to be higher priority in the MPM list, compared to the intra prediction mode of the upper adjacent block 2440.

[00311] Also, when the current block has a non-square shape, the intra-prediction mode of the adjacent block in the direction along the long side of the current block can be set to higher priority in the MPM list. With reference to FIG. 24C, when the current block 2400 has a non-square shape whose width is larger than its height, the intra-prediction mode of the upper adjacent block 2460 adjacent to the width direction of the current block 2400, from adjacent blocks 2450 and 2460 having equal size, can be set to located with a higher priority in the MPM list, compared to the intra-prediction mode of the left adjacent block 2450.

[00312] FIG. 25 is a diagram illustrating adjacent blocks of the current block that are used in the MPM list according to another embodiment.

[00313] According to another embodiment, instead of an intra-prediction mode of an adjacent block directly adjacent to the current block, an intra-prediction mode of an adjacent block that is not adjacent to the current block and spaced apart by a predetermined distance may be included in the MPM list. With reference to FIG. 25, instead of adjacent blocks 2510 and 2520 that are directly adjacent to the current block 2500, intra-prediction modes of adjacent blocks 2530 and 2540 spaced apart by a predetermined distance may be used when setting the MPM list. As an exception, instead of the intra-prediction mode having the highest probability among the intra-prediction modes of adjacent blocks of the current block, the least probable mode having the lowest probability may be included in the MPM list.

[00314] According to various embodiments, the MPM list may be set using the left block and top block intra prediction modes, and then the additional MPM list may be set using the intra prediction modes included in the MPM list. Hereinafter, the first installed MPM list is called the default MPM list. The reason why an additional MPM list is set in addition to the default MPM list is to cover the case where the intra prediction mode, which is not included in the first set default MPM list, is determined to be the intra prediction mode of the current block. The optional MPM list may include intra prediction modes having a predModeIntra obtained by logarithmic addition or subtraction of a predefined value to or from predModeIntra values of the intra prediction modes included in the default MPM list. For example, when the predModeIntra value of the arbitrary intra-prediction modes included in the existing MPM list is a default value, the additional MPM list may include intra-prediction modes having the values predModeIntra default±1, default±2, default±4, default ±8, default±16 and default±32. First, the number of residual intra prediction modes not to be included in the default MPM list and the optional MPM list may be determined, and the number of intra prediction modes to be included in the default MPM list and the number of intra prediction modes to be inclusion in the supplementary MPM list. The default MPM list and optional MPM list can be applied according to the stages. That is, it is first determined whether the intra-prediction mode of the current block is included in the default MPM list, and then, when the intra-prediction mode of the current block is not included in the default MPM list, an optional MPM list can be set. The optional MPM list may be encoded using a truncated unary (TU) binarization coding based on the number of intra-prediction modes included therein.

[00315] When the intra prediction mode of the current block is not included in the MPM list, the picture encoding apparatus 150 separately signals the intra prediction mode information of the current block. Hereinafter, the intra prediction mode of the current block, which is not included in the MPM list and transmitted separately, is referred to as intra prediction mode residual information (intra_mpm_remainder). As residual intra prediction mode information, a difference value between the intra prediction mode index (predModeIntra_current) of the current block and the reference intra prediction mode index (predModeIntra_MPM) of the intra prediction modes of the MPM list can be used. For example, when the intra prediction mode index (predModeIntra_current) of the current block is 30 and the intra prediction mode index (predModeIntra_MPM) of the reference intra prediction mode determined from the MPM list is 20, only the value 10 corresponding to (30-20) can be used as the residual information of the intra-prediction mode. The image encoding apparatus 150 may add, to the bitstream, a difference value of 10 as residual intra prediction mode information and transmit the bitstream, and the image decoding apparatus 100 may determine the intra prediction mode of the current block by adding a difference value of 10 obtained from the bitstream, to the intra prediction mode index 20 of the reference intra prediction mode.

[00316] In accordance with an embodiment, the MPM list may be generated considering at least one of the size and shape of the current block and the size of the picture.

[00317] Returning to FIG. 20, according to another embodiment, when the current block has a non-square shape, instead of the intra-prediction modes included in the MPM list using maxAB, the intra-prediction mode of the adjacent block, which is similar to the direction in which the current block has a large length of width and height of the current block, can be included in the MPM list. In detail, when the current block has a non-square shape whose height is larger than its width, the intra-prediction mode of the adjacent block, which is relatively close to the vertical direction, which is the height direction from the prediction mode A of the left adjacent block 2020 and the upper adjacent prediction mode B block 2030 may be replaced by maxAB. On the other hand, when the current block has a non-square shape whose width is larger than its height, the intra-prediction mode of the adjacent block, which is relatively close to the horizontal direction, which is the width direction, from the prediction mode A of the left adjacent block 2020 and mode B upper adjacent block prediction 2030 may be replaced by maxAB. For example, returning to FIG. 18, when it is assumed that the current block has a non-square shape with a size of 16×32, where the height is larger than the width, and the intra-prediction mode A index of the left adjacent block 2020 is 22, close to the horizontal direction, and the intra-prediction mode B index of the upper adjacent block 2030 is 54, close to the vertical direction, 54, which is the value of the intra prediction mode B index value of the upper adjacent block 2030, which is close to the vertical direction, can be used as the maxAB value used when the MPM list is set.

[00318] According to another embodiment, as the block size increases, the probability that the DC mode or the planar mode is to be selected increases, and thus, for a block with a size equal to or greater than the predetermined size, the planar mode and DC mode can be set in a higher priority order of the MPM list. For example, the planar mode may be set to MPM[0], which is the top priority order, and the DC mode may be set to MPM[1], which is the second top priority order. When the block size is small, the similarity with intra-prediction modes of adjacent blocks is large, and thus the intra-prediction modes of the upper adjacent block and the left adjacent block can be set with a high priority of the MPM list.

[00319] According to another embodiment, when the resolution of a picture is increased, the probability that the flat area is increased is large, and thus the priority order of the non-angular intra prediction modes can be set to a high priority of the MPM list. For example, when the resolution is equal to or greater than 4K, which is a predetermined threshold, the DC mode and the planar mode can be set to a higher priority order of the MPM list.

[00320] According to another embodiment, when the MPM list generated in the prediction of an intra prediction block that has been previously processed is stored as a lookup table, and the intra prediction block to be processed thereafter is processed, the MPM list can be used, saved as a lookup table. Also, the MPM list may be updated each time each intra-prediction block is processed. The non-angular intra-prediction modes can be set in the higher priority order of mpm[0] and mpm[1], and the angular intra-prediction modes can be set in the lower priority order of mpm[2~5]. After the MPM list is generated, the intra-prediction modes and priority order included in the MPM list can be changed using the MPM ordering table. For example, the MPM list is assumed to be set to {DC, planar, H, V, A, B, A+n, A-n, B+n, B-n}. In this regard, H refers to the intra-prediction mode in the horizontal direction, V refers to the intra-prediction mode in the vertical direction, A refers to the intra-prediction mode of the left adjacent block, B refers to the intra-prediction mode of the upper adjacent block, and n refers to a predefined integer (for example, n is 1 or 2). Also, the number included in the MPM ordering table refers to the address of the MPM list array. When the MPM ordering table matches {0, 1, 4, 5, 6, 7}, the intra-prediction modes mpm[0], mpm[1], mpm[4], mpm[5], mpm[6], and mpm are selected [7] of the MPM list, and thus the MPM list {DC, Planar, V, A, B, A+n, A-n} can be reacquired.

[00321] Also, the MPM lists that were previously generated are stored, given the types of tools applied to the previously processed intra prediction blocks, or the size and shape of the previous block, and then the MPM list of the previously processed intra block with the same condition may be used for the intra-block to be processed afterwards.

[00322] According to another embodiment, when the current block does not use a reference pixel that is directly adjacent, an MPM list that excludes DC mode and planar mode and is in the MPM list obtained using adjacent block intra-prediction modes can be used. current block. Also, as described above, instead of maxAB used when the intra-prediction mode of the left adjacent block and the intra-prediction mode of the upper adjacent block are different, minAB, which is the smaller index of the intra-prediction mode of the indices A and B of the intra-prediction mode, can be used. the left adjacent block and the top adjacent block. That is, when the intra prediction mode index (predModeIntra) of the left adjacent block is A and the intra prediction mode index (predModeIntra) of the right adjacent block is B, minAB which is obtained by minAB=Min(A, B) can be used instead of maxAB.

[00323] According to another embodiment, the MPM list may include {V, H, 34, 2, 66} by default, and then the average of the horizontal part intra-prediction modes and the average of the vertical part intra-prediction modes from intra-prediction modes obtained from the left adjacent block intra-prediction mode and the upper adjacent block intra-prediction mode may be included in the optional MPM list. According to another embodiment, an intra-prediction mode corresponding to the intra-prediction mode index of a value obtained by adding or subtracting a predetermined offset (e.g., the offset is an integer equal to or greater than 1) with or from the intra-prediction mode index of an adjacent block , which is excluded when the MPM list is generated, may be included in the optional MPM list. As described above, when the adjacent block is not available when the MPM list is generated, the intra-prediction mode of the adjacent block can be set as the default planar mode.

[00324] FIG. 26 is a reference diagram illustrating an MPM list generation scheme in parallel processing, according to an embodiment.

[00325] According to an embodiment, the top adjacent block and the left adjacent block, which are used in generating the MPM list of the plurality of blocks to be processed in parallel, may be equal. With reference to FIG. 26, in order to process blocks 2710, 2720, 2730 and 2740 in parallel, it is necessary to independently parse or decode blocks 2710, 2720, 2730 and 2740. In particular, when blocks 2710, 2720, 2730 and 2740 are all intra-predicted blocks, the common list The MPM may be applied to blocks 2710, 2720, 2730, and 2740 to enable parallel processing with respect to blocks 2710, 2720, 2730, and 2740. That is, the MPM list used in determining the intra-prediction mode of blocks 2710, 2720, 2730, and 2740 is obtained using the intra-prediction modes of the upper adjacent block A 2750 and the left adjacent block L 2760 of the parallel processing data unit, where blocks 2710, 2720, 2730, and 2740 are combined.

[00326] FIG. 27 illustrates a lookup table showing mapping relationships between indices of intra prediction modes (predModeIntra) and angle parameters (IntraPredAngle) according to intra prediction modes, according to an embodiment, and FIG. 28 illustrates a lookup table showing mapping relationships between indices of intra prediction modes (predModeIntra) and angle parameters (IntraPredAngle) according to intra prediction modes, according to another embodiment.

[00327] The specific direction of the intra prediction modes according to the various embodiments described above can be represented using the angular parameter IntraPredAngle about the specific direction based on the intra prediction mode index (predModeIntra), except for the 90 degree vertical direction and the horizontal direction 180 degrees. For example, the direction of the intra-prediction modes of the horizontal part may be in the direction of tan-1(intraPredAngle/fixed number) using a fixed number in the horizontal direction and the angular parameter IntraPredAngle in the vertical direction, and the direction of the intra-prediction modes of the vertical part may be in the direction of tan ^-1 (fixed number/intraPredAngle) using the angle parameter IntraPredAngle in the horizontal direction and a fixed number in the vertical direction. In this regard, the fixed number may be a power of 2. For example, the fixed number may be one of 32, 64, and 128.

[00328] FIG. 29 is a reference diagram for describing IntraPredAngle angular parameters related to directions of intra prediction modes, according to embodiments.

[00329] A prediction direction based on the intra prediction mode may be indicated using a fixed number in the horizontal direction and an IntraPredAngle angle parameter in the vertical direction, or may be indicated using an IntraPredAngle angular parameter in the horizontal direction and a fixed number in the vertical direction. For example, with reference to FIG. 29, a particular direction 2912 relative to the current pixel 2910 has an angle of tan ^-1 (32/intraPredAngle) (degrees) or (90 - tan ^-1 (32/intraPredAngle) (degrees) using the IntraPredAngle angular parameter in the horizontal direction and a fixed number of 32 in vertical direction.

[00330] In intra-prediction, an adjacent pixel may be determined using a fixed number and an angle parameter IntraPredAngle.

[00331] A process for determining an adjacent pixel 2911 indicated by a particular direction 2911 relative to the current pixel 2910 will now be described. It is assumed that the position difference in the vertical direction between the current pixel 2910 and the adjacent pixel 2911 is n. In this respect, based on the trigonometric function, a proportional ratio corresponding to (y+1):n=32:intraPredAngle is set. From the proportional ratio, we can deduce n=(y+1)*intraPredAngle/32. The operation n=(y+1)* intraPredAngle/32 can be performed via a bit operation as n=(y+1)*intraPredAngle>>5. Thus, the location of an adjacent pixel can be determined using intraPredAngle, provided that the size of the current block and the location of the current pixel 2910 are known.

[00332] When the value of (y+1)*intraPredAngle is a multiple of 32, p indicates an adjacent pixel at an integer location, and when the value of (y+1)*intraPredAngle is not a multiple of 32, a specific direction based on intraPredAngle indicates the gap between two adjacent pixels (k and k+1). When a particular direction based on intraPredAngle indicates the gap between two adjacent pixels (k and k+1), the weighted average of the two adjacent pixels (k and k+1) may be used as the prediction value of the current pixel 2910.

[00333] In intra prediction, an adjacent pixel in a particular direction is used as a reference pixel, i.e., prediction value, for the current pixel 2910. Assuming a fixed number in the horizontal or vertical direction, the directions of the intra prediction angular modes can be are specified using a single parameter of the IntraPredAngle angular parameter. Therefore, as described above with reference to FIG. 27 and 28, an angle parameter IntraPredAngle indicating specific directions of intra prediction angular modes corresponding to intra prediction mode indices (predModeIntra) of the intra prediction modes may be predetermined as a lookup table.

[00334] The disclosure has been specifically shown and described with reference to its embodiments. In this regard, one skilled in the art will appreciate that various changes in form and detail may be made without departing from the scope of the disclosure. Therefore, the embodiments are to be considered in a descriptive sense only and not by way of limitation. The scope of the disclosure is not defined by the detailed descriptions of the disclosure, but by the following claims, and all differences within the scope will be understood to be included in the disclosure.

[00335] Meanwhile, the above-described embodiments of the disclosure may be written as a program executable on a computer, and may be implemented in mainframe digital computers that execute the program using a computer-readable recording medium. Examples of the computer-readable recording media include magnetic storage media (eg, ROMs, floppy disks, hard disks, etc.), optical recording media (eg, CD-ROMs or DVDs), or the like.

Claims (8)

A video decoding method, comprising the steps of: obtaining reference sample information indicating the position of adjacent pixels of the current block to be used as reference samples of the current block, wherein the adjacent pixels are in contact with the top border and left border of the current block or are removed by a predetermined distance from the top border and left border of the current block ; when it is determined that adjacent pixels that are a predetermined distance away from the top border and the left border of the current block are used as reference samples of the current block, using the reference sample information, it is determined that the planar mode should not be the intra-prediction mode of the current block; configuring an intra prediction mode candidate list including a plurality of intra prediction mode candidates based on determining that the planar mode should not be the intra prediction mode of the current block; obtaining, from the bitstream, an index indicating an intra-prediction mode from a plurality of intra-prediction modes included in the list of intra-prediction mode candidates; determining an intra-prediction mode of the current block using the index; and perform intra-prediction on the current block using the intra-prediction mode of the current block, wherein the intra prediction mode candidate list is obtained by using at least one of the left block intra prediction mode adjacent to the left side of the current block and the top block intra prediction mode adjacent to the top side of the current block.

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