RU2811779C1 - Image decoding method and device and image coding method and device in image coding system - Google Patents

Abstract

FIELD: image encoding.

SUBSTANCE: list of potentially suitable variants of the intra-prediction modes of the current block is constructed, including the DC intra-prediction mode, based on the intra-prediction modes of neighbouring blocks relative to the current block. The intra-prediction mode of the current block is retrieved based on the list of potentially suitable variants of intra-prediction modes. A discrete prediction sample of the current block is retrieved based on the intra-prediction mode. The intra-prediction types include the first-intra prediction type using an intra-prediction reference line adjacent to the current block, the second intra-prediction type using an intra-prediction reference line not adjacent to the current block, and the third intra-prediction type, to which the mode based on intra-subsegments is applied. The lists of potentially suitable intra-prediction mode options constructed for cases in which the intra-prediction type is the first intra-prediction type, the second intra-prediction type, and the third intra-prediction type are identical.

EFFECT: improved efficiency of image encoding.

3 cl, 25 dwg

Description

State of the art

Field of technology to which the invention relates

[1] The present disclosure relates to image encoding technology, and more particularly, to an image decoding method and apparatus for performing intra-prediction by retrieving a list of potentially suitable intra-prediction mode candidates from a plurality of intra-prediction types in an image encoding system.

Description of the Prior Art

[2] Recently, the demand for high-quality, high-definition images, such as high-definition (HD) images and ultra-high-definition (UHD) images, has been increasing in various fields of technology. Since the image data is high resolution and high quality, the amount of information or bits that must be transmitted increases relative to the legacy image data. Therefore, when image data is transmitted using a medium such as a traditional wired/wireless broadband line, or image data is stored using an existing storage medium, transmission costs and storage costs for them increase.

[3] Accordingly, there is a need for high-performance image compression technology to efficiently transmit, store and reproduce high-quality, high-resolution image information.

The essence of the invention

[4] The purpose of the present disclosure is to provide a method and apparatus for improving image encoding efficiency.

[5] Another object of the present disclosure is to provide a method and apparatus for improving intra-prediction performance.

[6] It is yet another object of the present disclosure to provide a method and apparatus for applying an identical construction process to intra-prediction types when constructing a list of potentially suitable intra-prediction mode candidates for retrieving the intra-prediction mode.

[7] It is yet another object of the present disclosure to provide a method and apparatus for extracting a reference sample sample used in DC intra-prediction mode, taking into account a reference line index.

[8] According to an embodiment of the present disclosure, an image decoding method performed by a decoding apparatus is provided. The method includes receiving image information including prediction-related information for a current block, and generating a reconstructed sample of the current block based on the image information.

[9] According to another embodiment of the present disclosure, a decoding apparatus that performs image decoding is provided. The decoding apparatus includes an entropy decoder configured to receive image information including prediction-related information for a current block, and a prediction module configured to generate a reconstructed sample of the current block based on the image information.

[10] According to another embodiment of the present disclosure, an image encoding method performed by an encoding apparatus is provided. The method includes generating a reconstructed sample of the current block, generating prediction-related information for the current block, and encoding image information including the prediction-related information.

[11] According to another embodiment of the present disclosure, an image encoding apparatus is provided. The encoding device includes a prediction module configured to generate a reconstructed sample of the current block, and an entropy encoder configured to generate prediction-related information for the current block, encode image information including prediction-related information.

Advantages of the invention

[12] According to the present disclosure, it is possible to improve the overall efficiency of image/video compression.

[13] According to the present disclosure, it is possible to reduce hardware and software implementation complexity by using a unified process for constructing lists of intra-prediction modes for intra-prediction types.

[14] According to the present disclosure, it is possible to improve the efficiency of intra-prediction coding by reducing the dependence on intra-prediction types using a unified process for constructing lists of intra-prediction modes for intra-prediction types.

[15] According to the present disclosure, it is possible to improve intra-prediction coding efficiency by extracting a reference sample sample used when MRL is applied and the intra-prediction mode is extracted as a DC-intra-prediction mode based on the reference frame index.

[16] According to the present disclosure, it is possible to improve intra-prediction encoding efficiency by extracting a reference sample used when MRL is applied, and the intra-prediction mode is extracted as a DC-intra-prediction mode based on the index of the reference frame and the shape of the current block.

[17] According to the present disclosure, it is possible to improve the intra-prediction coding efficiency by extracting a reference sample sample used when MRL is applied, and the intra-prediction mode is extracted as a planar intra-prediction mode based on the reference frame index.

Brief description of drawings

[18] FIG. 1 briefly illustrates an example of a video/image encoding apparatus to which embodiments of the present disclosure are applicable.

[19] FIG. 2 is a circuit diagram illustrating the configuration of a video/image encoding apparatus to which embodiment(s) of the present disclosure may be applied.

[20] FIG. 3 is a circuit diagram illustrating the configuration of a video/image decoding apparatus to which embodiment(s) of the present disclosure may be applied.

[21] FIG. 4 schematically shows a hierarchical structure for a coded image/video.

[22] FIG. 5 schematically shows context-adaptive binary arithmetic coding (CABAC) for encoding a syntactic element.

[23] FIG. 6 illustrates an example of a video/image encoding method based on intra-prediction.

[24] FIG. 7 illustrates an example of a video/image decoding method based on intra-prediction.

[25] FIG. 8 schematically shows the intra-prediction procedure.

[26] FIG. 9 illustrates directional intra-modes in 65 prediction directions.

[27] FIG. 10 illustrates several reference lines that can be used in MRL.

[28] FIG. 11 illustrates an example in which a block to which an ISP is applied is segmented into subblocks based on block sizes.

[29] FIG. 12 illustrates an example of retrieving an MPM list according to the applied intra-prediction.

[30] FIG. 13 illustrates an example of constructing an MPM list of a current block and retrieving an intra-prediction mode according to the present embodiment.

[31] FIG. 14 illustrates an example of intra-prediction based coding according to the present embodiment.

[32] FIG. 15 illustrates an example of intra-prediction based coding according to the present embodiment.

[33] FIG. 16 illustrates an example of intra-prediction based coding according to the present embodiment.

[34] FIG. 17 illustrates a reference sample used to extract a DC value when the intra-prediction type of the current block is MRL and the intra-prediction mode of the current block is a DC-intra-prediction mode.

[35] FIG. 18 illustrates a reference sample used when the intra-prediction type of the current block is MRL, and the intra-prediction mode of the current block is the planar intra-prediction mode.

[36] FIG. 19 illustrates a reference sample used to extract a DC value when the intra-prediction type of the current block is MRL and the intra-prediction mode of the current block is a DC-intra-prediction mode.

[37] FIG. 20 illustrates a reference sample used when the intra-prediction type of the current block is MRL, and the intra-prediction mode of the current block is the planar intra-prediction mode.

[38] FIG. 21 schematically illustrates an image encoding method performed by the encoding apparatus according to the present disclosure.

[39] FIG. 22 schematically illustrates an encoding apparatus that implements an image encoding method according to the present disclosure.

[40] FIG. 23 schematically illustrates an image decoding method performed by a decoding apparatus according to the present disclosure.

[41] FIG. 24 schematically illustrates a decoding apparatus that implements an image decoding method according to the present disclosure.

[42] FIG. 25 illustrates a block diagram of a content streaming system to which the present disclosure applies.

Detailed Description of Embodiments

[43] The present disclosure may be modified in various forms, and specific embodiments thereof are described and illustrated in the drawings. However, these embodiments are not intended to limit the disclosure. The terms used in the following description are used to simply describe specific embodiments, but are not intended to limit the disclosure. The singular expression includes the plural expression so far, so far, so long as they are clearly interpreted differently. Terms such as “include” and “have” are intended to indicate that there are features, numbers, steps, operations, elements, components, or combinations thereof used in the following description, and as such are to be understood that the possibility of the presence or addition of one or more other features, numbers, steps, operations, elements, components or combinations of the above is not excluded.

[44] Meanwhile, elements in the drawings described in the disclosure are drawn independently for convenience in explaining various specific functions and do not imply that the elements are implemented by independent hardware or independent software. For example, two or more elements of the elements may be combined to form a single element, or a single element may be segmented into multiple elements. Embodiments in which elements are combined and/or segmented are within the scope of the disclosure.

[45] The present disclosure relates to video/image coding. For example, the methods/embodiments disclosed in the present disclosure may be applied to a method disclosed in the Versatile Video Coding (VVC) standard. In addition, the methods/embodiments disclosed in the present disclosure may be applied to a method disclosed in the EVC (fundamental video coding) standard, the AOMedia Video 1 (AV1) standard, the second generation audio/video coding standard (AVS2), or the video coding standard /next generation images (for example (H.267 or (H.268, etc.).

[46] The present disclosure presents various embodiments of video/image encoding, and the embodiments may be performed in combination with each other unless otherwise indicated.

[47] Exemplary embodiments of the present disclosure are described in detail below with reference to the accompanying drawings. In addition, like reference numerals are used to identify like elements throughout the drawings, and identical descriptions of like elements are omitted.

[48] FIG. 1 briefly illustrates an example of a video/image encoding device to which embodiments of the present disclosure are applicable.

[49] Referring to FIG. 1, the video/image encoding system may include a first device (source device) and a second device (receiver device). A source device may deliver encoded information or video/image data in file or streaming form to a receiving device via a digital storage medium or network.

[50] The source device may include a video source, an encoder, and a transmitter. The receiving device may include a receiver, a decoding device, and a rendering module. The encoding device may be called a “video/image encoding device” and the decoding device may be called a “video/image decoding device”. The transmitter can be included in the encoding device. The receiver may be included in the decoding device. The rendering module may include a display, and the display may be configured as a separate device or an external component.

[51] A video source may obtain video/image through a video/image capture, synthesis, or shaping process. The video source may include a video/image capture device and/or a video/image generation device. The video/image capturing device may include, for example, one or more cameras, video/image archives including previously captured video/images, and the like. The video/image generating apparatus may include, for example, computers, tablet computers and smartphones and may (electronically) generate video/images. For example, a virtual video/image may be generated via a computer or the like. In this case, the video/image capturing process can be replaced by the associated data generation process.

[52] The encoding device can encode the input video/image. The encoder may perform a sequence of procedures such as prediction, transform, and quantization for compression and encoding efficiency. Encoded data (encoded video/image information) may be output in the form of a bitstream.

[53] The transmitter may transmit information or encoded video/image data output in the form of a bitstream to a receiver of a receiving device via a digital storage medium or network in the form of a file or streaming. The digital storage medium may include various storage media such as USB, SD, CD, DVD, Blu-Ray, HDD, SSD, and the like. The transmitter may include an element for generating a multimedia file through a predefined file format and may include an element for transmission through a broadcast/communication network. The receiver may receive/extract the bit stream and transmit the received bit stream to a decoding device.

[54] A decoding apparatus may decode a video/image by performing a series of procedures such as dequantization, deconversion, and prediction corresponding to the operation of the encoding apparatus.

[55] The rendering module may prepare a decoded video/image by rendering. The video/image prepared by rendering can be displayed through the display.

[56] In the present disclosure, video may refer to a sequence of images over time. A frame generally means a unit representing one image in a particular time zone, and a slice/tile is a unit that constitutes part of a frame when encoded. A slice/tile may include one or more coding tree units (CTUs). One frame can consist of one or more slices/tiles. A tile is a rectangular CTU area in a particular column of tiles and a particular row of tiles in a frame. A column of tiles is a rectangular area of CTUs having a height equal to the height of the frame and a width specified by syntax elements in the frame parameter set. A row of tiles is a rectangular area of CTUs having a height specified by syntax elements in the frame parameter set and a width equal to the width of the frame. A tile scan is a specific sequential ordering of the CTUs segmenting a frame, in which CTUs are ordered sequentially in a raster scan of the CTUs in a tile, whereas tiles in a frame are ordered sequentially in a raster scan of the frame's tiles. A slice may include an integer number of complete tiles or an integer number of consecutive complete CTU lines in a frame tile, which may be exclusively contained in a single NAL unit.

[57] Meanwhile, a frame may be divided into two or more subframes. A subframe may be a rectangular area of one or more slices in a frame.

[58] Pixel or pel can mean the smallest unit that makes up one frame (or image). Additionally, "sample" may be used as a term corresponding to a pixel. A sample may generally represent a pixel or a pixel value, and may represent only a pixel/pixel value of a luma component or only a pixel/pixel value of a chrominance signal component.

[59] The unit may represent a basic image processing unit. The unit may include at least one of a specific frame area and information associated with the area. One unit may include one block of luma signals and two blocks of chrominance signals (eg, Cb, Cr). Unit may be used interchangeably with terms such as block or zone in some cases. In general, an MxN block may include samples (or arrays of samples) or a set (or array) of conversion coefficients of M columns and N rows.

[60] As used herein, “A or B” may mean “A only,” “B only,” or “both A and B.” In other words, "A or B" may be interpreted as "A and/or B" in the present specification. For example, "A, B or C" may mean "A only", "B only", "C only" or "any combination of A, B and C" as used herein.

[61] A slash (/) or comma (comma) as used herein can mean “and/or.” For example, "A/B" could mean "A and/or B". Accordingly, "A/B" can mean "A only", "B only" or "both A and B". For example, "A, B, C" could mean "A, B or C".

[62] As used herein, “at least one of A and B” may mean “A only,” “B only,” or “both A and B.” Additionally, “at least one of A or B” or “at least one of A and/or B” may be construed as “at least one of A and B” in the present specification.

[63] Moreover, “at least one of A, B, and C” may mean “A only,” “B only,” “C only,” or “any combination of A, B, and C” as used herein. In addition, "at least one of A, B or C" or "at least one of A, B and/or C" may mean "at least one of A, B and C".

[64] In addition, the parenthesis used in the present description of the invention may mean "for example." In particular, in the case of "prediction (intra-prediction (intra-prediction))", it may represent that "intra-prediction" is proposed as an example of "prediction". In other words, “prediction” in the present specification is not limited to “intra-prediction”, and “intra-prediction” may be offered as an example of “prediction”. Additionally, in the case of "prediction (ie, intra-prediction)", it may also represent that "intra-prediction" is proposed as an example of "prediction".

[65] Technical features separately described in one drawing may be implemented separately or simultaneously in the present specification.

[66] FIG. 2 is a circuit diagram illustrating the configuration of a video/image encoding apparatus to which embodiment(s) of the present disclosure may be applied. Hereinafter, in this document, the encoding device may include an image encoding device and/or a video encoding device. In addition, the image encoding method/apparatus may include a video encoding method/apparatus. Alternatively, the video encoding method/apparatus may include an image encoding method/apparatus.

[67] Referring to FIG. 2, the encoding apparatus 200 includes an image segmentation module 210, a prediction module 220, a residual processor 230 and an entropy encoder 240, an adder 250, a filter 260, and a memory 270. The prediction module 220 may include an inter-prediction module 221 and an inter-prediction module 222. intra-predictions. Residual processor 230 may include a transformer 232, a quantizer 233, a dequantizer 234, and an inverse transformer 235. Residual processor 230 may further include a subtractor 231. The adder 250 may be referred to as a “recovery module” or a “recovery block generator.” The image segmentation module 210, prediction module 220, residual processor 230, entropy encoder 240, adder 250, and filter 260 may be configured by at least one hardware component (eg, a chipset or encoder processor) according to an embodiment. In addition, storage device 270 may include a decoded frame buffer (DPB) or may be configured with a digital storage medium. The hardware component may further include a storage device 270 as an internal/external component.

[68] The image segmentation module 210 may segment an input image (either a frame or a movie frame) input to the encoder 200 into one more processing units. For example, a processing unit may be called a "coding unit (CU)". In this case, the coding unit may be recursively segmented according to a quadtree, binary tree, and ternary tree (QTBTTT) structure from a coding tree unit (CTU) or largest coding unit (LCU). For example, one coding unit may be segmented into multiple coding units of greater depth based on a quadtree structure, a binary tree structure, and/or a ternary structure. In this case, for example, a quadtree structure may be applied first, and a binary tree structure and a ternary structure may be subsequently applied. Alternatively, a binary tree structure may be used first. The encoding procedure of the present disclosure may be performed based on a final encoding unit that is no longer segmented. In this case, the largest coding unit can be used as the final coding unit based on the coding efficiency according to the characteristics of the images, or if necessary, the coding unit can be recursively segmented into coding units of greater depth, and the coding unit having the optimal size can be used as the final coding units. Here, the encoding procedure may include a prediction, transformation and reconstruction procedure, which is described below. As another example, the processing unit may further include a prediction unit (PU) or a transformation unit (TU). In this case, the prediction unit and the transformation unit may be split or segmented from the above final encoding unit. The prediction unit may be a sample prediction unit, and the transform unit may be a unit for extracting a transform coefficient and/or a unit for extracting a residual signal from the transform coefficient.

[69] Unit may be used interchangeably with terms such as block or zone in some cases. In general, an MxN block can represent a set of discrete samples or transform coefficients consisting of M columns and N rows. The sample may generally represent a pixel or a pixel value, may represent only a pixel/pixel value of a luma signal component, or may represent only a pixel/pixel value of a chrominance signal component. Discrete count can be used as a term corresponding to one frame (or image) for a pixel or pel.

[70] In the encoding device 200, a prediction signal (predicted block, prediction sample array) output from the inter-prediction unit 221 or intra-prediction unit 222 is subtracted from the input image signal (original block, original sample array) to generate a residual signal (residual block, residual sample array), and the generated residual signal is transmitted to the converter 232. In this case, as shown, a module for subtracting a prediction signal (predicted block, prediction sample array) from an input image signal (source block , array of original discrete samples) in the encoder 200 may be called "subtractor 231". The prediction module may perform a prediction on a block to be processed (hereinafter referred to as a "current block"), and generate a predicted block including prediction samples for the current block. The prediction module may determine whether intra-prediction or inter-prediction is applied based on the current block or CU. As described below in the description of each prediction mode, the prediction module may generate various prediction-related information, such as prediction mode information, and transmit the generated information to the entropy encoder 240. Information regarding the prediction may be encoded in the entropy encoder 240 and output in the form of a stream bits

[71] The intra-prediction module 222 may predict the current block by reference to the samples in the current frame. The samples for reference may be located in the surroundings of the current block or may be spaced apart according to the prediction mode. In intra-prediction, prediction modes may include a plurality of undirected modes and a plurality of directed modes. The omnidirectional mode may include, for example, DC mode and planar mode. The directional mode may include, for example, 33 directional prediction modes or 65 directional prediction modes according to the granularity of the prediction direction. However, this is merely an example; more or less directional prediction modes may be used depending on the setting. The intra-prediction module 222 may determine the prediction mode applied to the current block by using the prediction mode applied to the adjacent block.

[72] The inter-prediction unit 221 may extract a predicted block for the current block based on a reference block (an array of reference samples) indicated by a motion vector for the reference frame. Here, in order to reduce the amount of motion information transmitted in the inter-prediction mode, the motion information may be predicted in units of blocks, sub-blocks or discrete samples based on the correlation of the motion information between a neighboring block and the current block. The motion information may include a motion vector and a reference frame index. The motion information may further include inter-prediction direction information (L0 prediction, L1 prediction, bi-prediction, etc.). In the case of inter-prediction, the neighbor block may include a spatial neighbor block present in the current frame and a temporal neighbor block present in the reference frame. The reference frame including the reference block and the reference frame including the temporary adjacent block may be identical or different. A temporary neighbor block may be called a “co-located reference block”, a “col-located CU (colCU)”, etc., and a reference frame including a temporary neighboring block may be called a “col-located frame (colPic)”. For example, the inter-prediction module 221 may configure a list of motion information candidates based on neighboring blocks and generate information indicating which candidates are used to extract the motion vector and/or reference frame index of the current block. Inter-prediction can be performed based on various prediction modes. For example, in the case of the skip mode and the combine mode, the inter-prediction unit 221 may use the motion information of the adjacent block as the motion information of the current block. In the skip mode, unlike the combine mode, the residual signal may not be transmitted. In the case of the motion vector prediction (MVP) mode, the motion vector of an adjacent block can be used as a motion vector predictor, and the motion vector of the current block can be indicated by signaling a motion vector difference.

[73] The prediction module 220 may generate a prediction signal based on various prediction methods described below. For example, the prediction module may not only apply intra-prediction or inter-prediction to predict one block, but also simultaneously apply both intra-prediction and inter-prediction. This may be called "coupled inter- and intra-prediction (CIIP)". In addition, the prediction module may be based on an intra-block copy (IBC) prediction mode or a palette mode for block prediction. The IBC prediction mode or palette mode can be used for encoding image/video content of a game and the like, for example, screen content encoding (SCC). IBC essentially performs prediction in the current frame, but can be performed similarly to inter-prediction in which the reference block is retrieved in the current frame. Thus, the IBC may use at least one of the inter-prediction technologies described in the present disclosure. Palette mode can be considered an example of intra-encoding or intra-prediction. When palette mode is applied, a sampled value in a frame may be signaled based on information regarding the palette table and palette index.

[74] The prediction signal generated by the prediction module (including the inter-prediction module 221 and/or the intra-prediction module 222) can be used to generate a reconstructed signal or generate a residual signal. Converter 232 may generate conversion coefficients by applying conversion technology to the residual signal. For example, the transform technology may include at least one of a discrete cosine transform (DCT), a discrete sine transform (DST), a graph-based transform (GBT), or a conditionally nonlinear transform (CNT). Here, GBT means a graph-derived transformation when the relationship information between pixels is represented by the graph. CNT means a transform generated based on a prediction signal generated using all previously reconstructed pixels. In addition, the conversion process can be applied to square pixel blocks that are identical in size, or can be applied to blocks that are variable in size rather than square.

[75] Quantizer 233 may quantize the transform coefficients and transmit them to entropy encoder 240, and entropy encoder 240 may encode the quantized signal (information regarding the quantized transform coefficients) and output a bit stream. Information regarding the quantized transform coefficients may be referred to as "residual information". Quantizer 233 may re-arrange the block quantized transform coefficients into one-dimensional vector form based on the scanning order of the coefficients, and generate information regarding the quantized transform coefficients based on the quantized transform coefficients in one-dimensional vector form. Information regarding conversion coefficients can be generated. The entropy encoder 240 may implement various encoding techniques, such as, for example, exponential Golomb coding, context adaptive variable length coding (CAVLC), context adaptive binary arithmetic coding (CABAC), and the like. Entropy encoder 240 may encode information needed for video/image reconstruction other than quantized transform coefficients (eg, syntax element values, etc.) together or separately. Encoded information (eg, encoded video/image information) may be transmitted or stored in NAL (Network Abstraction Layer) units in the form of a bit stream. The video/image information may further include information regarding various parameter sets, such as an adaptation parameter set (APS), a frame parameter set (PPS), a sequence parameter set (SPS), or a video parameter set (VPS). In addition, the video/image information may further include general restriction information. In the present disclosure, information and/or syntax elements transmitted/signalled from an encoding device to a decoding device may be included in video/frame information. The video/image information may be encoded through the encoding procedure described above and included in the bitstream. The bit stream may be transmitted over a network or may be stored on a digital storage medium. The network may include a broadcast network and/or a communications network, and the digital storage medium may include various storage media such as USB, SD, CD, DVD, Blu-Ray, HDD, SSD, and the like. A transmitter (not shown) transmitting the signal output from the entropy encoder 240 and/or a storage module (not shown) storing the signal may be included as an internal/external element of the encoding device 200, and alternatively, the transmitter may be included in the entropy encoder 240 .

[76] The quantized transform coefficients output from quantizer 233 can be used to generate a prediction signal. For example, a residual signal (residual block or residual samples) may be recovered by applying dequantization and inverse transform to the quantized transform coefficients through dequantizer 234 and inverter 235. Adder 250 adds the reconstructed residual signal with a prediction signal output from inter-prediction module 221 or intra-prediction module 222 to generate a reconstructed signal (reconstructed frame, reconstructed block, reconstructed sample array). If there is no remainder for a block to be processed, for example in a case in which the skip mode is applied, the predicted block can be used as the reconstructed block. The adder 250 may be referred to as a "recovery module" or a "recovered block generator." The generated reconstructed signal can be used to intra-predict the next block to be processed in the current frame, and can be used to inter-predict the next frame through filtering, as described below.

[77] Meanwhile, luma conversion with chrominance scaling (LMCS) can be applied during encoding and/or reconstruction of frames.

[78] Filter 260 may enhance the subjective/objective quality of images by applying filtering to the reconstructed signal. For example, filter 260 may generate a modified reconstructed frame by applying various filtering techniques to the reconstructed frame and store the modified reconstructed frame in storage device 270, namely, a DPB of storage device 270. Various filtering techniques may include, for example, deblocking filtering. , sampled adaptive bias, adaptive contour filter, bilateral filter, etc. The filter 260 may generate various filtering-related information and transmit the generated information to the entropy encoder 240, as described below in the description of each filtering method. Information associated with filtering may be encoded by entropy encoder 240 and output in the form of a bit stream.

[79] The modified reconstructed frame transferred to the storage device 270 can be used as a reference frame in the inter-prediction unit 221. When inter-prediction is applied by the encoding apparatus, prediction mismatch between the encoding apparatus 200 and the decoding apparatus can be eliminated, and encoding efficiency can be improved.

[80] The DPB of the storage device 270 may store the modified reconstructed frame for use as a reference frame in the inter-prediction module 221. Memory 270 may store block motion information from which motion information in the current frame is retrieved (or encoded) and/or motion information of blocks in a frame that have already been reconstructed. The stored motion information may be transmitted to the inter-prediction unit 221 and used as spatial neighbor block motion information or temporal neighbor block motion information. Memory 270 may store reconstructed samples of reconstructed blocks in the current frame and may provide reconstructed samples to intra-prediction module 222.

[81] FIG. 3 is a circuit diagram illustrating the configuration of a video/image decoding apparatus to which embodiment(s) of the present disclosure may be applied. Hereinafter, hereinafter, the decoding apparatus may include an image decoding apparatus and/or a video decoding apparatus. In addition, the image decoding method/device may include a video decoding method/device. Alternatively, the video decoding method/device may include an image decoding method/device.

[82] Referring to FIG. 3, the decoding apparatus 300 may include an entropy decoder 310, a residual processor 320, a prediction unit 330, an adder 340, a filter 350, a memory 360. The prediction unit 330 may include an inter-prediction unit 331 and an intra-prediction unit 332. Residual processor 320 may include a dequantizer 321 and an inverse converter 322. Entropy decoder 310, residual processor 320, predictor 330, adder 340, and filter 350 may be configured by a hardware component (eg, a chipset or decoder processor) according to an embodiment. In addition, storage device 360 may include a decoded frame buffer (DPB) or may be configured with a digital storage medium. The hardware component may further include storage device 360 as an internal/external component.

[83] When a bitstream including video/image information is input, the decoding apparatus 300 can reconstruct an image corresponding to the process in which the video/image information is processed in the encoding apparatus of FIG. 2. For example, decoding apparatus 300 may extract units/blocks based on block segmentation-related information obtained from the bit stream. The decoding apparatus 300 may perform decoding using a processing unit employed in the encoding apparatus. Thus, the decoding processing unit, for example, may be a coding unit, and the coding unit may be segmented according to a quadtree structure, a binary tree structure, and/or a ternary tree structure from a coding tree unit or a largest coding unit. One or more transformation units may be derived from a coding unit. The reconstructed image signal decoded and output by the decoding device 300 can be reproduced by the playback device.

[84] The decoding apparatus 300 may receive a signal output from the encoding apparatus of FIG. 2 in the form of a bit stream, and the received signal may be decoded through entropy decoder 310. For example, entropy decoder 310 may parse the bit stream to extract information (eg, video/image information) needed for image reconstruction (or frame reconstruction). The video/image information may further include information regarding various parameter sets, such as an adaptation parameter set (APS), a frame parameter set (PPS), a sequence parameter set (SPS), or a video parameter set (VPS). In addition, the video/image information may further include general restriction information. The decoding apparatus may further decode the frame based on information regarding the parameter set and/or general constraint information. The signaling/receiving information and/or syntax elements described later in the present disclosure may be decoded, may be decoded by a decoding procedure, and obtained from the bitstream. For example, entropy decoder 310 decodes information in a bitstream based on an encoding method, such as exponential Golomb, CAVLC, or CABAC encoding, and the output syntax elements required for image reconstruction and the quantized values of the transform coefficients for the remainder. More specifically, the entropy CABAC decoding method may receive a resolution element corresponding to each syntax element in the bitstream, determine a context model using information of a target decoding syntax element, decoding information of a target decoding block, or information of a symbol/resolution element decoded in a previous stage, and perform arithmetic decoding for the permission element by predicting the probability of occurrence of the permission element according to the determined context model and generating a symbol corresponding to the meaning of each syntactic element. In this case, the entropy CABAC decoding method can update the context model by using the decoded symbol/grant element information for the context model of the next symbol/grant element after determining the context model. The prediction-related information from the information decoded by the entropy decoder 310 may be provided to the prediction module (inter-prediction module 332 and intra-prediction module 331), and the residual value for which entropy decoding is performed in the entropy decoder 310, i.e. e. the quantized transform coefficients and associated parameter information may be input to residual processor 320. Residual processor 320 may extract a residual signal (residual block, residual samples, array of residual samples). In addition, information regarding filtering from information decoded by the entropy decoder 310 may be provided to the filter 350. Meanwhile, a receiver (not shown) for receiving a signal output from the encoding device may be further configured as an internal/external element of the device 300 decoding device, or the receiver may be a component of the entropy decoder 310. Meanwhile, the decoding apparatus according to this document may be called a “video/image/frame decoding apparatus,” and the decoding apparatus may be classified into an information decoder (video/image/frame information decoder) and selective decoder (decoder of discrete samples of video/images/frames). The information decoder may include an entropy decoder 310, and the sample decoder may include at least one of a dequantizer 321, an inverse converter 322, an adder 340, a filter 350, a memory 360, an inter-prediction module 332, and an intra-prediction module 331. -predictions.

[85] The dequantizer 321 may dequantize the quantized transform coefficients and output the transform coefficients. The dequantizer 321 may re-arrange the quantized transform coefficients into a two-dimensional block form. In this case, re-arrangement can be performed based on the order of coefficient scanning performed in the encoder. The dequantizer 321 may perform dequantization on the quantized transform coefficients by using a quantization parameter (eg, quantization step size information) and obtain the transform coefficients.

[86] An inverse converter 322 inversely converts the conversion coefficients to obtain a residual signal (residual block, array of residual samples).

[87] Prediction module 230 may perform prediction for the current block and may generate a predicted block including prediction samples for the current block. The prediction module can determine whether intra-prediction or inter-prediction is applied to the current block based on the prediction information output from the entropy decoder 310, and can determine a particular intra/inter-prediction mode.

[88] Prediction module 320 may generate a prediction signal based on various prediction methods described below. For example, the prediction module may not only apply intra-prediction or inter-prediction to predict one block, but also simultaneously apply intra-prediction and inter-prediction. This may be called "coupled inter- and intra-prediction (CIIP)". In addition, the prediction module may be based on an intra-block copy (IBC) prediction mode or a palette mode for block prediction. The IBC prediction mode or palette mode can be used for encoding image/video content of a game and the like, for example, screen content encoding (SCC). IBC essentially performs prediction in the current frame, but can be performed similarly to inter-prediction in which the reference block is retrieved in the current frame. Thus, the IBC may use at least one of the inter-prediction technologies described in the present disclosure. Palette mode can be considered an example of intra-encoding or intra-prediction. When palette mode is applied, a sampled value in a frame may be signaled based on information regarding the palette table and palette index.

[89] The intra-prediction module 331 may predict the current block by reference to the samples in the current frame. The samples for reference may be located in the surroundings of the current block or may be spaced apart according to the prediction mode. In intra-prediction, prediction modes may include a plurality of undirected modes and a plurality of directed modes. The intra-prediction module 331 can determine the prediction mode applied to the current block by using the prediction mode applied to the adjacent block.

[90] The inter-prediction unit 332 may extract a predicted block for the current block based on a reference block (an array of reference samples) indicated by a motion vector for the reference frame. In this case, in order to reduce the amount of motion information transmitted in the inter-prediction mode, the motion information may be predicted in units of blocks, sub-blocks or discrete samples based on the correlation of the motion information between a neighboring block and the current block. The motion information may include a motion vector and a reference frame index. The motion information may further include inter-prediction direction information (L0 prediction, L1 prediction, bi-prediction, etc.). In the case of inter-prediction, the neighbor block may include a spatial neighbor block present in the current frame and a temporal neighbor block present in the reference frame. For example, the inter-prediction module 332 may configure a list of candidate motion information candidates based on neighboring blocks, and extract a motion vector of the current block and/or a reference frame index based on the received candidate candidate selection information. Inter-prediction may be performed based on various prediction modes, and information regarding the prediction may include information indicating an inter-prediction mode for the current block.

[91] The adder 340 may generate a reconstructed signal (recovered frame, reconstructed block, reconstructed sample array) by adding the resulting residual signal with a prediction signal (predicted block, predicted sample array) output from a prediction module (including inter module 332). -predictions and/or module 331 intra-predictions). If there is no remainder for a block to be processed, for example when skip mode is applied, the predicted block can be used as the reconstructed block.

[92] The adder 340 may be referred to as a “recovery module” or a “recovered block generator.” The generated reconstructed signal may be used to intra-predict the next block to be processed in the current frame, may be output by filtering as described below, or may be used to inter-predict the next frame.

[93] Meanwhile, luma conversion with chrominance scaling (LMCS) can be applied in the frame decoding process.

[94] Filter 350 may enhance the subjective/objective quality of images by applying filtering to the reconstructed signal. For example, filter 350 may generate a modified reconstructed frame by applying various filtering techniques to the reconstructed frame and store the modified reconstructed frame in storage device 360, namely, a DPB of storage device 360. Various filtering techniques may include, for example, deblocking filtering. , sampled adaptive bias, adaptive loop filter, bilateral filter, etc.

[95] The (modified) reconstructed frame stored in the DPB of the storage device 360 can be used as a reference frame in the inter-prediction unit 332. Memory 360 may store block motion information from which motion information in the current frame is retrieved (or decoded) and/or motion information of blocks in a frame that have already been reconstructed. The stored motion information may be transmitted to the inter-prediction unit 260 so that it is used as spatial neighbor block motion information or temporal neighbor block motion information. Storage device 360 may store reconstructed samples of reconstructed blocks in the current frame and transmit the reconstructed samples to intra-prediction module 331.

[96] In the present disclosure, the embodiments described in the filter 260, inter-prediction module 221, and intra-prediction module 222 of the encoding device 200 may be identical or appropriately applied so that they correspond to the filter 350, inter-prediction module 332 and the intra-prediction module 331 of the decoding device 300. The same may also apply to the intra-prediction module 332 and the intra-prediction module 331.

[97] FIG. 4 schematically shows a hierarchical structure for a coded image/video.

[98] Referring to FIG. 4, the encoded image/video is divided into a video coding layer (VCL), which performs image/video decoding processing, and itself, a subsystem that transmits and stores the encoded information, and a network abstraction layer (NAL), which exists between these VCLs. and subsystem and is responsible for network adaptation functions.

[99] In the VCL, VCL data may be generated including compressed video data (slice data), or a message with additional enhancement information (SEI) additionally required for the video decoding process, or a set of parameters including such information, may be generated. , as Frame Parameter Set (PPS), Sequence Parameter Set (SPS), Video Parameter Set (VPS).

[100] In NAL, a NAL unit may be generated by adding header information (NAL unit header) to a primary data byte sequence (RBSP) generated in the VCL. In this case, RBSP means the slice data, parameter set, SEI message, etc. generated in the VCL. The NAL unit header may include NAL unit type information indicated according to the RBSP data included in the corresponding NAL unit.

[101] As shown in the drawing, the NAL unit can be divided into a VCL NAL unit and a non-VCL NAL unit according to the RBSP generated in the VCL. A VCL NAL unit may mean a NAL unit including information regarding an image (slice data), a non-VCL NAL unit may mean a NAL unit including information (a set of parameters or SEI message) necessary for decoding an image .

[102] The above-described VCL NAL unit and non-VCL NAL unit can be transmitted over the network by attaching header information according to the subsystem data standard. For example, a NAL unit may be converted into a predefined standard data form such as H.266/VVC file format, Real Time Transport Protocol (RTP), Transport Stream (TS), and transmitted over various networks.

[103] As described above, in a NAL unit, a NAL unit type may be indicated according to an RBSP data structure included in a corresponding NAL unit, and information regarding this NAL unit type may be stored and signaled in a NAL header. units.

[104] For example, a NAL unit can be classified into a VCL NAL unit type and a non-VCL NAL unit type according to whether or not the NAL unit includes information (slice data) regarding an image. The VCL type of a NAL unit can be classified according to the properties and types of frames included in the VCL NAL unit, and the type of a non-VCL NAL unit can be classified according to a parameter set type.

[105] The following is an example of a NAL unit type specified according to the type of a parameter set included in a non-VCL NAL unit type.

[106] - Adaptation Parameter Set (APS) NAL unit: type for the NAL unit containing the APS

[107] - Decoding Parameter Set (DPS) NAL unit: type for the NAL unit containing the DPS

[108] - Video Parameter Set (VPS) NAL unit: type for the NAL unit containing the VPS

[109] - Sequence Parameter Set (SPS) NAL unit: type for the NAL unit containing the SPS

[110] - NAL unit PPS (frame parameter set): type for NAL unit containing PPS

[111] - NAL unit frame header (PH): type for NAL unit containing PH

[112] The above-described NAL unit types may have syntax information for the NAL unit type, and the syntax information may be stored and signaled in the NAL unit header. For example, the syntax information may be nal_unit_type, and the NAL unit types may be indicated by the nal_unit_type value.

[113] Meanwhile, as described above, one frame may include a plurality of slices, and one slice may include a slice header and slice data. In this case, one frame header may further be added for multiple slices (for a slice header and a slice data set) in one frame. The frame header (frame header syntax) may include information/parameters typically applicable to the frame. In the present disclosure, the slice may be mixed or replaced by a group of tiles. Moreover, in the present disclosure, the slice header may be mixed or replaced with a type group header.

[114] The slice header (slice header syntax) may include information/parameters typically applicable to the slice. APS (APS Syntax) or PPS (PPS Syntax) may include information/parameters typically applicable to one or more slices or frames. SPS (SPS syntax) may include information/parameters typically applicable to one or more sequences. VPS (VPS syntax) may include information/parameters typically applicable to multiple layers. DPS (DPS syntax) may include information/parameters generally applicable to the entire video. The DPS may include information/parameters associated with coded video sequence (CVS) concatenation. In the present disclosure, the high-level syntax (HLS) may include at least one of APS syntax, PPS syntax, SPS syntax, VPS syntax, DPS syntax, frame header syntax, and slice header syntax.

[115] In the present disclosure, image/video information encoded by the encoding device and signaled in the form of a bitstream to the decoding device may include not only frame segmentation related information, intra/inter-prediction information, residual information, in-loop filtering information, etc., but also information included in the slice header, information included in the frame header, information included in APS, information included in PPS, information included in SPS, information included in VPS and/or information included in the DPS. In addition, the image/video information may further include NAL unit header information.

[116] In addition, as described above, the encoder can perform various exponential Golomb code encoding methods, such as, for example, context adaptive variable length coding (CAVLC) and context adaptive binary arithmetic coding (CABAC). In addition, the decoding apparatus may decode the information in the bit stream based on the encoding method, for example, exponential Golomb, CAVLC, or CABAC encoding, and output the value of the syntax element required for image reconstruction and the quantized value of the transform coefficient associated with the remainder.

[117] For example, the above-described encoding methods may be implemented as described below.

[118] FIG. 5 schematically shows context-adaptive binary arithmetic coding (CABAC) for encoding a syntactic element. For example, in a CABAC encoding process, when the input signal is a syntax element instead of a binary value, the encoding device may convert the input signal to a binary value by binarizing the value of the input signal. In addition, when the input signal is already a binary value (ie, when the input signal value is a binary value), conversion to binary form may not be performed and may be bypassed. Here, each binary number 0 or 1 constituting the binary value may be called a "permission element". For example, if the binary string, when converted to binary form, is 110, each of the 1s, 1s, and 0s is called "one resolution element." The permission element(s) for one syntax element may specify the value of the syntax element.

[119] The binarized syntax element resolution elements can then be input into the regular encoding engine or the bypass encoding engine. The regular encoding mechanism of the encoding device may extract a context model reflecting the probability value into a corresponding resolution element, and may encode the corresponding resolution element based on the extracted context model. The regular encoding mechanism of the encoder may update the context model for the corresponding permission element after encoding for each permission element. An encoded permission element, as described above, may be referred to as a "context-encoded permission element".

[120] Meanwhile, when the binarized syntax element resolution elements are input into the bypass encoding mechanism, they can be encoded as follows. For example, the encoder's bypass encoding mechanism omits the probability estimation procedure relative to the input resolution element and the probabilistic model updating procedure applied to the resolution element after encoding. When bypass encoding is applied, the encoder can encode the input resolution element by applying a uniform probability distribution instead of extracting the context model, thereby increasing encoding speed. The encoded permission element, as described above, may be referred to as a "bypass permission element".

[121] Entropy decoding may represent the process of performing an identical process with the above entropy encoding in reverse order.

[122] For example, when a syntax element is decoded based on a context model, the decoding device may receive a resolution element corresponding to the syntax element via a bit stream, may determine the context model using the syntax element and decoding information of the target decoding block or neighboring blocks or symbol information/ the permission elements decoded in the previous step may extract the value of the syntactic element by predicting the probability of occurrence of the received permission element according to the determined context model and performing arithmetic decoding of the permission element. Thereafter, the context model of the next decoded permission element can be updated with the determined context model.

[123] In addition, for example, when bypass decoding of a syntax element is performed, the decoding apparatus may receive a resolution element corresponding to the syntax element via a bitstream, and may decode the input resolution element by applying a uniform probability distribution. In this case, the decoding apparatus may omit a procedure for retrieving the context model of the syntax element and a procedure for updating the context model applied to the permission element after decoding.

[124] Meanwhile, when video encoding is performed as described above, prediction is performed in order to improve compression efficiency. Accordingly, a predicted block may be generated including prediction samples for the current block, which is a target encoding block. For example, when the above intra-prediction is performed, the correlation between the samples can be used, and the difference between the original block and the predicted block, i.e. the remainder may work out. The above transformation and quantization can be applied to the remainder to remove spatial redundancy. Specifically, the encoding method and the intra-prediction decoding method may be as follows.

[125] FIG. 6 illustrates an example of a video/image encoding method based on intra-prediction.

[126] Referring to FIG. 6, the encoder performs intra prediction for the current block (S600). The encoding device extracts the intra-prediction mode/type for the current block, extracts the adjacent reference samples of the current block, generates prediction samples in the current block based on the intra-prediction mode/type and the adjacent reference samples. Here, the procedures for determining the intra-prediction mode/type, extracting adjacent reference samples, and generating prediction samples may be performed simultaneously, or one procedure may be performed before the other procedure. The encoding device may determine a mode/type applied to the current block from a plurality of intra-prediction modes/types. The encoder may compare RD costs for intra-prediction mode/types and determine the optimal intra-prediction mode/type for the current block.

[127] Meanwhile, the encoding device may perform a filtering procedure on the prediction samples. Filtering of discrete prediction samples may be referred to as "post-filtering". Some or all of the prediction samples may be filtered through a prediction sample filtering procedure. In some cases, the prediction sample filtering procedure may be omitted.

[128] The encoder generates residual samples for the current block based on the (filtered) prediction samples (S610). The encoder may compare the prediction samples in the original samples of the current block based on phase and extract the residual samples.

[129] The encoding device can encode image information including information regarding intra-prediction (prediction information) and residual information regarding residual samples (S620). The prediction information may include intra-prediction mode information and intra-prediction type information. The encoding apparatus may output encoded image information in the form of a bitstream. The output bit stream may be transmitted to a decoding device via a storage medium or a network.

[130] The residual information may include residual encoding syntax, which is described below. The encoder may transform/quantize the residual samples so as to extract the quantized transform coefficients. The residual information may include information regarding the quantized transform coefficients.

[131] Meanwhile, as described above, the image encoding device can generate a reconstructed frame (including reconstructed samples and a reconstructed block). To this end, the encoder can extract the (modified) residual samples by performing inverse transform/inverse quantization on the quantized transform coefficients again. The reason for performing inverse transform/inverse quantization again after transforming/quantizing the residual samples in this manner is to extract identical residual samples as residual samples extracted in the decoding apparatus as described above. The encoder may generate a reconstructed block including reconstructed samples for the current block based on the prediction samples and the (modified) residual samples. A reconstructed frame for the current frame may be generated based on the reconstructed block. As described above, an in-loop filtering procedure may further be applied to the reconstructed frame.

[132] FIG. 7 illustrates an example of a video/image decoding method based on intra-prediction.

[133] The decoding apparatus may perform an operation corresponding to an operation performed by the encoding apparatus.

[134] Prediction information and residual information may be obtained from the bitstream. Residual samples for the current block can be extracted based on the residual information. In particular, transform coefficients may be extracted by performing inverse quantization based on quantized transform coefficients extracted based on residual information, residual samples for the current block may be extracted by performing inverse transform on the transform coefficients.

[135] Specifically, the decoding device can extract the intra-prediction mode/type for the current block based on the received prediction information (intra-prediction mode/type information) (S700). The decoder may extract adjacent reference samples of the current block. The decoding apparatus may generate prediction samples in the current block based on the intra-prediction mode/type and adjacent reference samples. In this case, the image decoding apparatus may perform a filtering procedure on the prediction samples. Filtering the predictive samples may be called "post-filtering". Some or all of the prediction samples may be filtered through a prediction sample filtering procedure. In some cases, the prediction sample filtering procedure may be omitted.

[136] The decoding apparatus generates residual samples for the current block based on the received residual information (S730). The decoding apparatus can generate reconstructed samples for the current block based on the prediction samples and residual samples, and can extract the reconstructed block including the reconstructed samples (S740). A reconstructed frame for the current frame may be generated based on the reconstructed block. As described above, an in-loop filtering procedure may further be applied to the reconstructed frame.

[137] The intra-prediction mode information may include, for example, flag information (e.g., intra_luma_mpm_flag) indicating whether or not the most probable mode (MPM) or remaining mode is applied to the current block, and when the MPM is applied to the current block, the prediction mode information may further include index information (eg, intra_luma_mpm_idx) indicating one of the potentially eligible intra-prediction mode options (potentially eligible MPM options). Potentially suitable options for intra-prediction modes (potentially suitable MPM options) can be constructed from a list of potentially suitable MPM options or an MPM list. In addition, when an MPM is not applied to the current block, intra-prediction mode information includes remaining mode information (e.g., intra_luma_mpm_remainder) indicating one of the remaining intra-prediction modes excluding potentially eligible intra-prediction mode options (potentially eligible MPMs) -options). The decoding apparatus may determine the intra-prediction mode of the current block based on the intra-prediction mode information.

[138] In addition, intra-prediction type information can be implemented in various forms. For example, the intra-prediction type information may include intra-prediction type index information indicating one of the intra-prediction types. As another example, intra-prediction type information may include at least one of reference sample line information (e.g., intra_luma_ref_idx) representing whether or not the MRL is applied to the current block, and if applied, which reference the sample line is used, ISP flag information representing whether or not ISP is applied to the current block (eg, intra_subpartitions_mode_flag), ISP-type information indicating the type of subsegment splitting when ISP is applied (eg, intra_subpartitions_split_flag), flag information representing whether whether PDCP is applied or not, or flag information representing whether LIP is applied or not. In addition, the intra-prediction type information may include a MIP flag representing whether or not matrix intra-prediction (MIP) is applied to the current block.

[139] The intra-prediction mode information and/or the intra-prediction type information may be encoded/decoded via the encoding method described in the present disclosure. For example, intra-prediction mode information and/or intra-prediction type information may be encoded/decoded by entropy coding (eg, CABAC, CAVLC).

[140] FIG. 8 schematically shows the intra-prediction procedure.

[141] Referring to FIG. 8, as described above, the intra-prediction procedure may include a step of determining an intra-prediction mode/type, a step of retrieving adjacent reference samples, and a step of performing intra-prediction (generating a prediction sample). The inter-prediction procedure may be performed by the encoding apparatus and the decoding apparatus as described above. In the present disclosure, the encoding device may include an encoding device and/or a decoding device.

[142] Referring to FIG. 8, the encoding device determines the intra-prediction mode/type (S800).

[143] The encoding apparatus may determine an intra-prediction mode/type applied to the current block from among the various intra-prediction modes/types described above, and may generate prediction-related information. The prediction-related information may include intra-prediction mode information representing an intra-prediction mode applied to the current block and/or intra-prediction type information representing an intra-prediction type applied to the current block. The decoding apparatus may determine an intra-prediction mode/type applied to the current block based on the prediction-related information.

[144] The intra prediction mode information may include, for example, flag information (e.g., intra_luma_mpm_flag) representing whether the most likely mode (MPM) is applied to the current block or the remaining mode is applied, and when the MPM is applied to the current block, the prediction mode information may further include index information (eg, intra_luma_mpm_idx) indicating one of the potentially eligible intra-prediction mode options (potentially eligible MPM options). Potentially suitable options for intra-prediction modes (potentially suitable MPM options) can be constructed from a list of potentially suitable MPM options or an MPM list. In addition, when the MPM is not applied to the current block, the intra-prediction mode information may further include remaining mode information (e.g., intra_luma_mpm_remainder) indicating one of the remaining intra-prediction modes, excluding potentially suitable intra-prediction mode options (potentially suitable MPM options). The decoding apparatus may determine the intra-prediction mode of the current block based on the intra-prediction mode information.

[145] In addition, intra-prediction type information can be implemented in various forms. For example, the intra-prediction type information may include intra-prediction type index information indicating one of the intra-prediction types. As another example, the intra-prediction type information may include at least one of reference sample line information (e.g., intra_luma_ref_idx) representing whether or not the MRL is applied to the current block, and if applied, which reference the sample line is used, ISP flag information representing whether or not ISP is applied to the current block (eg, intra_subpartitions_mode_flag), ISP-type information indicating the type of subsegment splitting when ISP is applied (eg, intra_subpartitions_split_flag), flag information representing whether whether PDCP is applied or not, or flag information representing whether LIP is applied or not. In addition, the intra-prediction type information may include a MIP flag representing whether or not matrix intra-prediction (MIP) is applied to the current block.

[146] For example, when intra prediction is applied, the intra prediction mode applied to the current block can be determined using the intra prediction mode of the adjacent block. For example, the encoder may select one of the potential candidate most probable modes (MPMs) in an MPM list retrieved based on additional potential candidate modes and/or intra-prediction mode of the neighboring block (e.g., left neighbor and/or top neighbor block) of the current block, or select one of the remaining intra-prediction modes not included in the potentially eligible MPM options (and planar mode), based on the remaining MPM information (remaining intra-prediction mode information). The MPM list may be configured to include or not include planar mode as a potential candidate. For example, when an MPM list includes planar mode as a potential candidate, the MPM list may have 6 potential candidates, and when an MPM list does not include planar mode as a potential candidate, the MPM list may have 5 potentially suitable options. When the MPM list does not include planar mode as a potential candidate, a non-planar flag (eg, intra_luma_not_planar_flag) representing whether the current block is not an intra-prediction mode or not a planar mode may be signaled. For example, the MPM flag may be signaled first and the MPM index and the non-planar flag may be signaled when the value of the MPM flag is 1. Additionally, the MPM index may be signaled when the value of the non-planar flag is 1. Here, the fact that the MPM list is configured to not include planar mode as a potential candidate is that planar mode is always considered an MPM, not that planar mode is not an MPM , so that a flag (non-planar flag) is signaled first to check whether it represents planar mode or not.

[147] For example, whether or not the intra-prediction mode applied to the current block is among the potentially eligible MPM options (and planar mode) or remaining modes can be indicated based on the MPM flag (eg, intra_luma_mpm_flag). An MPM flag with a value of 1 may indicate that the intra-prediction mode for the current block is in potentially eligible MPM variants (and planar mode), and an MPM flag with a value of 0 may indicate that the intra-prediction mode for the current block is not in potentially suitable MPM variants (and planar mode). A non-planar flag (e.g., intra_luma_not_planar_flag) with a value of 0 may indicate that the intra-prediction mode for the current block is a planar mode, and a non-planar flag with a value of 1 may indicate that the intra-prediction mode for the current block is not a planar mode . The MPM index may be signaled in the form of the mpm_idx or intra_luma_mpm_idx syntax element, and the remaining intra prediction mode information may be signaled in the form of the rem_intra_luma_pred_mode or intra_luma_mpm_remainder syntax element. For example, the remaining intra-prediction mode information may indicate one of the remaining intra-prediction modes not included in the potentially eligible MPM (and planar mode) options among all intra-prediction modes by indexing in prediction mode number order. The intra-prediction mode may be an intra-prediction mode for a component (sample) of the luminance signal. Hereinafter herein, the intra prediction mode information may include at least one of an MPM flag (eg, intra_luma_mpm_flag), a non-planar flag (eg, intra_luma_not_planar_flag), an MPM index (eg, mpm_idx or intra_luma_mpm_idx), or information from the remaining intra-prediction modes (rem_intra_luma_luma_mpm_mode or intra_luma_mpminder). In the present disclosure, an MPM list may be referred to by various terms such as "candidMode List" and "candModeList".

[148] When a MIP is applied to the current block, a separate MPM flag (eg, intra_mip_mpm_flag) for the MIP, an MPM index (eg, intra_mip_mpm_idx), and remaining intra-prediction mode information (eg, intra_mip_mpm_remainder) may be signaled, and non-planar the flag may not be transmitted in service signals.

[149] In other words, in general, when block segmentation is performed on an image, the current block to be encoded and the adjacent block have similar image characteristics. Therefore, there is a high probability that the current block and the neighboring block have identical or similar intra-prediction modes. Accordingly, the encoder may use the intra-prediction mode of an adjacent block to encode the intra-prediction mode of the current block.

[150] The encoder may construct a list of most probable modes (MPM) for the current block. An MPM list may be referred to as a "potentially eligible MPM candidate list." Here, MPM may refer to modes used to improve encoding efficiency by taking into account the similarity between the current block and neighboring blocks during intra-prediction mode encoding. As described above, the MPM list may be configured to include a planar mode or may be configured to exclude a planar mode. For example, when the MPM list includes planar mode, the number of potential candidates in the MPM list may be 6. Likewise, when the MPM list does not include planar mode, the number of potential candidates in the MPM list may be equal to 5.

[151] The encoding apparatus may perform prediction based on various intra-prediction modes, and may determine an optimal intra-prediction mode based on rate-dependent distortion optimization (RDO) based thereon. In this case, the encoder can determine the optimal intra-prediction mode only by using the potentially suitable MPM options and the planar mode configured in the MPM list, or by additionally using the remaining intra-prediction modes, as well as the potentially suitable MPM options and planar mode configured in the MPM list. In particular, for example, if the intra-prediction type of the current block is a particular type (eg, LIP, MRL, or ISP) other than the normal intra-prediction type, the encoder may determine the optimal intra-prediction mode by considering only the potentially suitable MPMs. options and planar mode as potentially suitable intra-prediction mode options for the current block. Thus, in this case, the intra-prediction mode for the current block can be determined only from among the potentially suitable MPM options and the planar mode, and in this case, encoding/signaling of the MPM flag may not be performed. In this case, the decoding apparatus may logically output that the MPM flag is 1 without separately signaling the MPM flag.

[152] Meanwhile, in general, when the intra-prediction mode of the current block is not a planar mode and is one of the potentially suitable MPM options in the MPM list, the encoder generates an MPM index (mpm idx) indicating one of potentially suitable MPM options. when the intra-prediction mode of the current block is not included in the MPM list, the encoder generates remaining MPM information (remaining intra-prediction modes information) indicating a mode identical to the intra-prediction mode of the current block from the remaining intra-prediction modes not included to MPM list (and planar mode). The remaining MPM information may include, for example, the intra_luma_mpm_remainder syntax element.

[153] The decoding apparatus obtains intra-prediction mode information from the bit stream. As described above, the intra-prediction mode information may include at least one of an MPM flag, a non-planar flag, an MPM index, and remaining MPM information (remaining intra-prediction mode information). The decoding device can construct an MPM list. The construction of the MPM list is identical to the MPM list built in the encoding device. Thus, the MPM list may include intra-prediction modes of neighboring blocks or may further include specific intra-prediction modes according to a predetermined method.

[154] The decoding apparatus may determine the intra-prediction mode of the current block based on the MPM list and the intra-prediction mode information. For example, when the value of the MPM flag is 1, the decoder may extract the planar mode as the intra-prediction mode of the current block (based on the non-planar flag) or retrieve a candidate candidate indicated by the MPM index from among the candidate MPM candidates in MPM list as an intra-prediction mode for the current block. Here, the potential MPM candidates may represent only the candidates included in the MPM list, or may include not only the candidates included in the MPM list, but also the planar mode applicable when the value of the MPM flag equals 1.

[155] As another example, when the value of the MPM flag is 0, the decoding apparatus may extract the intra-prediction mode indicated by the remaining intra-prediction mode information (which may be referred to as “remaining MPM information”) from the remaining intra-prediction modes, not included in the MPM list, and planar mode as the intra-prediction mode of the current block. Meanwhile, as another example, when the intra-prediction type of the current block is a specific type (such as LIP, MRL or ISP, etc. .), the decoder may retrieve a potential candidate indicated by an MPM flag in planar mode or an MPM list as the intra-prediction mode of the current block without parsing/decoding/checking the MPM flag.

[156] The encoder extracts adjacent reference samples of the current block (S810). When intra-prediction is applied to the current block, adjacent reference samples that should be used for intra-prediction of the current block can be retrieved. The adjacent reference samples of the current block may include a sample adjacent to the left boundary of the current block of size nWxnH, and the sum of 2xnH samples adjacent to the bottom left of the current block, a sample adjacent to the top boundary of the current block, and the sum of 2xnW discrete samples adjacent to the upper right part relative to, and a discrete sample adjacent to the upper left part relative to the current block. Alternatively, the neighboring reference samples of the current block may include a plurality of columns of top neighboring samples and a plurality of rows of left neighboring samples. In addition, the adjacent reference samples of the current block may include the sum of nH samples adjacent to the right border of the current block with size nWxnH, the sum of nW samples adjacent to the bottom boundary of the current block, and the sample adjacent to the bottom right with respect to current block.

[157] On the other hand, when MRL is applied (i.e., when the MRL index value is greater than 0), adjacent reference samples may be located on lines 1-2 instead of line 0 adjacent to the current block on the left/top side, and in this case, the number of adjacent reference samples may further increase. Meanwhile, when ISP is applied, adjacent reference samples can be retrieved in sub-segment units.

[158] The encoding device extracts prediction samples by performing intra-prediction for the current block (S820). The encoder may extract prediction samples based on the intra-prediction mode/type and neighboring samples. The encoding device can extract a reference sample according to an intra-prediction mode of the current block from adjacent reference samples of the current block, and can extract a prediction sample of the current block based on the reference sample.

[159] Meanwhile, when intra prediction is applied to the current block, the encoding device/decoding device can extract the intra prediction mode for the current block and extract prediction samples for the current block based on the intra prediction mode as described above. Thus, the encoder/decoder can extract prediction samples of the current block by applying a directed or undirected mode based on the adjacent reference samples of the current block.

[160] By comparison, intra-prediction modes may include, for example, two non-directional (or non-angular) intra-prediction modes and 65 directional (or angular) intra-prediction modes. The non-directional intra-prediction modes may include planar intra-prediction mode #0 and DC-intra-prediction mode #1, and the directed intra-prediction modes may include 65 intra-prediction modes #2 to #66. However, this is an example, and the present disclosure can also be applied to cases of different numbers of intra-prediction modes. An intra-prediction mode #67 may further be used if necessary, and an intra-prediction mode #67 may represent a linear model (LM) based mode.

[161] FIG. 9 illustrates directional intra-modes in 65 prediction directions.

[162] Referring to FIG. 9, the intra-prediction modes can be divided into intra-prediction modes having a horizontal direction and intra-prediction modes having a vertical direction based on the intra-prediction mode #34 in the left upper diagonal prediction direction. In fig. 9, H and V stand for horizontal directivity and vertical directivity, and the numbers -32 to 32 indicate the offset in units of 1/32 in position on the sampling grid. Intra-prediction modes #2-#33 have a horizontal focus, and intra-prediction modes #34-#66 have a vertical focus. Intra-prediction mode #18 and intra-prediction mode #30 are respectively horizontal intra-prediction mode and vertical intra-prediction mode, intra-prediction mode #2 may be called "left lower diagonal intra-prediction mode", mode # The intra-prediction 34 may be referred to as the “left upper diagonal intra-prediction mode”, and the intra-prediction mode #55 may be referred to as the “right upper diagonal intra-prediction mode”.

[163] As an embodiment of intra-prediction, a method for selecting a reference sample line having the highest prediction accuracy from a plurality of reference sample lines of a current block and extracting a prediction sample using a reference sample located in the prediction direction in the selected reference sample may be provided. lines. This method may be called "multiple reference line (MRL) intra-prediction" or "MRL-based intra-prediction".

[164] In particular, only the first line adjacent samples above the current block and the first line adjacent samples to the left of the current block can be used as reference samples for intra-prediction in conventional intra-prediction. However, in MRL, intra-prediction can be performed using adjacent samples positioned in the top and/or left sample lines, separated from the current block by 1, 2 or 3 sample distances, as reference samples.

[165] FIG. 10 illustrates several reference lines that can be used in MRL. When MRL is executed, the decoding device may receive the reference line index. The reference line index may indicate one of a plurality of reference lines. The decoding apparatus may perform intra-prediction based on reference samples in the reference line indicated by the reference line index. The reference line index syntax element may be intra_luma_ref_idx. Additionally, the MRL may be disabled for first line (ie, first row) blocks in the CTU.

[166] As an embodiment of intra-prediction, a method for segmenting a current block in a horizontal direction or a vertical direction and performing intra-prediction in units of the segmented blocks may be provided. Thus, a method for segmenting a current block in a horizontal direction or a vertical direction to extract sub-blocks and performing intra-prediction for the sub-blocks may be provided. In this case, encoding/decoding may be performed per segmented subblock to form a reconstructed block, and the reconstructed block may be used as a reference block of the next segmented subblock. The above method may also be called "intra-subsegment-based prediction (ISP prediction)", "intra-subsegment-based (ISP) mode" or "intra-subsegment-based (ISP) mode-based prediction". Otherwise, the above method may also be called "ISP-based intra-prediction". Additionally, a sub-block may be referred to as an "intra-sub-segment". Otherwise, sub-blocks (or sub-segments) segmented according to the ISP may be called "translation units (TUs)".

[167] According to ISP, the current block can be segmented into two or four sub-segments in the vertical or horizontal direction based on the size of the current block. For example, when ISP is running, the current block may be segmented into the number of subblocks shown in the following table, depending on the size of the current block.

[168]

Table 1 Unit size (CU) Number of segments 4x4 Not segmented 4x8, 8x4 2 Other cases 4

[169] Referring to Table 1, the ISP may be disabled when the current block size is 4x4. The current block can be segmented into two subblocks when the current block size is 4x8 or 8x4, and can be segmented into four subblocks when the current block has sizes other than 4x4, 4x8, and 8x4 (i.e. i.e. sizes larger than 4x8 or 8x4).

[170] FIG. 11 illustrates an example in which a block to which an ISP is applied is segmented into subblocks based on block sizes. Referring to (a) of FIG. 11, the current block may be segmented into two sub-blocks when the size of the current block is 4×8 or 8×4. Referring to (b) of FIG. 11, the current block may be segmented into four sub-blocks when the current block has dimensions other than 4x4, 4x8, and 8x4 (ie, sizes larger than 4x8 or 8x4).

[171] Meanwhile, Mx128 (M≤64) and 128xN (N≤64) ISP blocks (i.e., intra-subsegments) may cause potential problems for 64x64 VDPUs. For example, an Mx128 CU in a single tree may have TBs of Mx128 luma signals and two TBs of M/2x64 chrominance signals corresponding to TBs of luma signals. When ISP is applied to a CU, TBs of luminance signals can be segmented into four Mx32 TBs, i.e. four Mx32 subblocks (only horizontal partitioning is possible), and each TB is smaller than a 64x64 block. However, in this case, the chroma block to which the ISP is applied may not be segmented in the design according to current video standards. Accordingly, the size of two TB chrominance signal components for TB luminance signal components exceeds 32×32. Likewise, the CU 128xN may cause a situation similar to the above situation. Accordingly, the above two cases may become problems in the 64x64 decoder pipeline. For this reason, the maximum CU size for which an ISP can be used may be limited to 64x64.

[172] When an ISP is applied, the encoder can generate an MPM list depending on the segmentation method (eg, horizontal partitioning or vertical partitioning) to reduce encoding complexity, and compare the intra-prediction modes in the generated MPM list in terms of distortion optimization depending on the bit rate (RDO) to extract the optimal intra-prediction mode. When the above MRL is used, the ISP cannot be used. Thus, ISP can only be used when the zero reference line is used for intra-prediction (ie when the value of intra_luma_ref_idx is 0). Additionally, when ISP is used, position-dependent intra-prediction (PDPC) cannot be used.

[173] A flag indicating whether or not ISP is applied may be transmitted on a per-block basis, and when ISP is applied to the current block, the flag indicating whether the partition type is a horizontal partition or a vertical partition, i.e. Whether the dividing direction is the horizontal direction or the vertical direction can be encoded/decoded. The flag indicating whether or not ISP is applied may be referred to as an "ISP flag", and the syntax element of the ISP flag may be intra_subpartitions_mode_flag. Additionally, the flag indicating the split type may be referred to as an “ISP split flag”, and the ISP split type syntax element may be intra_subpartitions_split_flag.

[174] The syntax elements associated with ISP are shown in the following table.

[175] Tab. 2

[176] In Table 2, intra_luma_ref_idx may be a reference line index syntax element. When ISP is applied, the intra-prediction mode for the current block can be equally applied to sub-segments of the current block, and intra-prediction can be performed by retrieving a neighboring reference sample per sub-segment to improve intra-prediction performance. Thus, when ISP is applied, the residual sample processing procedure can be performed on a per sub-segment basis. In other words, intra-prediction may be performed on each sub-segment to extract prediction samples, and the residual signal(s) regarding each sub-segment may be summed with the prediction samples regarding each sub-segment to extract reconstructed samples. The residual signal (residual samples) may be extracted through an inverse quantization/inverse transform procedure based on the residual information (quantized transform coefficient information or residual encoding syntax) in the bitstream. Intra-prediction for subsegments may be performed from the leftmost subsegment to the rightmost subsegment when the partition type is a vertical partition, and may be performed from the topmost subsegment to the bottommost subsegment when the partition type is a horizontal partition.

[177] For example, intra-prediction may be performed on the first subsegment of the current block to extract prediction samples, residual samples regarding the first subsegment may be extracted based on residual information regarding the first subsegment, and reconstructed samples regarding the first subsegment may be extracted based on the samples. prediction samples and residual discrete samples. Here, the first sub-segment may represent the leftmost sub-block if the partition type for the current block to which the ISP is applied is a vertical partition, and the first sub-segment may represent the topmost sub-block if the partition type for the current block to which the ISP is applied is represents a horizontal split.

[178] Then, some of the reconstructed samples in the first subsegment can be used as adjacent reference samples relative to the second subsegment (eg, the left or upper adjacent reference samples of the second subsegment) in the process of retrieving prediction samples regarding the second subsegment. Specifically, intra-prediction may be performed on the second subsegment of the current block to extract prediction samples, residual samples regarding the second subsegment may be extracted based on residual information regarding the second subsegment, and reconstructed samples regarding the second subsegment may be extracted based on the prediction samples. and residual discrete readings. Likewise, when the process of extracting prediction samples regarding the third sub-segment is performed, some recovered samples in the second sub-segment can be used as adjacent reference samples relative to the third sub-segment (eg, the left or upper adjacent reference samples of the third sub-segment). Likewise, when the process of extracting prediction samples regarding the fourth sub-segment is performed, some recovered samples in the third sub-segment can be used as adjacent reference samples relative to the fourth sub-segment (eg, the left or upper adjacent reference samples of the fourth sub-segment).

[179] Meanwhile, as another embodiment of intra-prediction, combined inter- and intra-prediction (CIIP) may be proposed. CIIP may represent a process of extracting a prediction sample of a current block based on inter-prediction and intra-prediction. For example, when CIIP is applied to the current block, the intra-prediction mode of the current block may be retrieved, and the first prediction sample of the current block may be retrieved based on the intra-prediction mode. Thereafter, the second prediction sample of the current block may be extracted by performing inter-prediction on the current block, and the prediction sample of the current block may be extracted by weighting summation (i.e., weighting averaging) of the first prediction sample and the second prediction sample . Here, the first prediction sample may be called an “intra-prediction sample”, and the second prediction sample may be called an “inter-prediction sample”. In addition, for example, the inter-prediction for the current block may be an inter-prediction according to the general combining mode. Specifically, for example, a list of potential merge candidates for the current block may be constructed based on motion information of neighboring blocks relative to the current block, and motion information of the current block may be retrieved based on a potential merge candidate in the list of potential merge candidates indicated by the merge index for of the current block, and a second prediction sample of the current block may be extracted based on the motion information.

[180] In addition, for example, a CIIP flag representing whether or not CIIP is applied to the current block may be signaled, and whether or not CIIP is applied to the current block may be determined based on the CIIP flag. For example, the CIIP flag may be signaled when the current block is encoded in concatenated mode and the current block includes at least 64 luminance samples (i.e., the product of the current block's width and height is 64 or greater ).

[181] In addition, for example, the intra-prediction mode of the current block when CIIP is applied can be extracted based on two syntax elements. For example, one of up to four intra-prediction modes may be used as the intra-prediction mode. The four intra-prediction modes may include a DC intra-prediction mode, a planar intra-prediction mode, a horizontal intra-prediction mode, and/or a vertical intra-prediction mode.

[182] For example, in CIIP, for the luminance signal component, up to four intra-prediction modes may be used, including a DC intra-prediction mode, a planar intra-prediction mode, a horizontal intra-prediction mode, and a vertical intra-prediction mode. Additionally, for example, when the width of the current block is twice the height, the vertical intra-prediction mode may not be available. In this case, only three intra-prediction modes are available. Additionally, for example, when the height of the current block is twice the width, the vertical intra-prediction mode may not be available. In this case, only three intra-prediction modes are available.

[183] In particular, for example, when CIIP is applied to the current block, the intra-prediction mode of the current block can be retrieved as follows. For example, a list of most probable modes (MPMs), including potentially suitable MPM options for the current block, can be constructed as follows. For example, an MPM list might include three potentially suitable MPM options.

[184] For example, the left neighbor block relative to the current block may be set to A, and the top neighbor block may be set to B. Thereafter, the intra-prediction modes of the left neighbor A and the top neighbor B, indicated by intraModeA and intraModeB, can be retrieved in the following way.

[185] - Set X to A or B

[186] - 1) when block X is not available, 2) when block X is not predicted using CIIP or intra-prediction mode, 3) when block B is located outside the current CTU, intraModeX may be set equal to DC-intra-prediction mode. Here, the current CTU may mean a CTU including the current block.

[187] - Otherwise, 1) when the intra-prediction mode of block X is a DC intra-prediction mode or a planar intra-prediction mode, intraModeX may be set equal to the intra-prediction mode of block X, i.e. DC intra-prediction mode or planar intra-prediction mode, or 2) when the X block intra-prediction mode is a vertical directional intra-prediction mode (i.e., intra-prediction modes #35-#66), intraModeX can be set equal to the vertical intra-prediction mode, or 3) when the intra-prediction mode of block X is a horizontal directional intra-prediction mode (i.e., intra-prediction modes #2-#34), intraModeX may be set equal to the horizontal intra-prediction mode .

[188] Potentially suitable MPM variants can then be retrieved based on the retrieved intraModeA and intraModeB.

[189] - For example, when intraModeA and intraModeB are identical:

[190] - When intraModeA is a planar intra-prediction mode or a DC-intra-prediction mode, three potentially suitable MPM options can be sequentially set to {planar intra-prediction mode, DC-intra-prediction mode, vertical intra-prediction mode }.

[191] - Alternatively, otherwise, i.e. when intraModeA is not a planar intra-prediction mode and a DC-intra-prediction mode, the three potentially suitable MPM options may be sequentially set to {intraModeA, planar intra-prediction mode, DC-intra-prediction mode}.

[192] - Otherwise, i.e. when intraModeA and intraModeB are not identical:

[193] - The first two potentially eligible MPM options can be set to {intraModeA, intraModeB}.

[194] - Thereafter, when confirmation is performed as an intra-prediction mode other than the retrieved MPM candidate candidate by checking whether it is included or not in the previously retrieved MPM candidate candidates in the order of the planar intra-prediction mode, DC intra-prediction mode and vertical intra-prediction mode, it can be added as a third potentially suitable MPM option.

[195] Meanwhile, for example, when the width of the current block is twice the height, or the height of the current block is twice the width, the MPM flag may be logically output to 1 without signaling. Otherwise, the MPM flag for the current block may be signaled.

[196] For example, when the value of the MPM flag is 1, an MPM index indicating one of the potential MPM candidates of the MPM list may be signaled, and the potential MPM candidate indicated by the MPM index may be retrieved as an intra-prediction mode for the current block. In addition, for example, when the value of the MPM flag is 0, the intra-prediction mode of the current block may be set to the "skip" mode. Here, the omitted mode may represent an intra-prediction mode not included in the MPM list of the four intra-prediction modes available in the CIIP. For example, when the planar intra prediction mode is not included in the MPM list, the skipped mode may be the planar intra prediction mode, and when the value of the MPM flag is 0, the intra prediction mode of the current block may be retrieved as the planar intra prediction mode , which represents the skipped mode. Meanwhile, for example, the intra-prediction mode of a CIIP-encoded CU can be stored and used to predict neighboring CUs encoded after the CU.

[197] Meanwhile, as described above, the first prediction sample and the second prediction sample may be averaged with weighting. Here, for example, weights for the first prediction sample and the second prediction sample may be derived based on the intra-prediction mode of the current block and/or the position of the current sample in the current block.

[198] In particular, for example, when the intra-prediction mode of the current block is a DC-intra-prediction mode or a planar intra-prediction mode, or the width or height of the current block is less than 4, an identical weighting factor may be applied to the first prediction sample and the second discrete prediction sample. Thus, when the intra prediction mode of the current block is a DC intra prediction mode or a planar intra prediction mode, or the width or height of the current block is less than 4, the weight coefficients for the first prediction sample and the second prediction sample can be extracted as identical meaning.

[199] In addition, in cases other than the above-described cases, weights for the first prediction sample and the second prediction sample may be extracted based on the intra-prediction mode of the current block and the position of the current sample in the current block. For example, when the intra prediction mode of the current block is a horizontal intra prediction mode, the current block may be divided into segments of size (W/4)xH. Also, when the current sample is located in the closest segment to the reference inter-prediction sample of the current block, the weight coefficient for the first prediction sample of the current sample may be set to 6, and the weight coefficient for the second prediction sample may be set to 2, or when the current sample is located in the second closest segment to the reference inter-prediction sample of the current block, the weight coefficient for the first prediction sample of the current sample may be set to 5, and the weight coefficient for the second prediction sample may be set to 3, or when the current sample sample is located in the third closest segment to the reference inter-prediction sample of the current block, the weight coefficient for the first prediction sample of the current sample may be set to 3, and the weight coefficient for the second prediction sample may be set to 5, or when the current sample located in the segment farthest from the reference inter-prediction sample of the current block, the weight coefficient for the first prediction sample of the current sample may be set to 2, and the weight coefficient for the second prediction sample may be set to 6. Here, the size of the current block may be WxH, W can represent the width of the current block, and H can represent the height of the current block.

[200] In addition, for example, when the intra-prediction mode of the current block is a vertical intra-prediction mode, the current block may be divided into segments of size Wx(H/4). Also, when the current sample is located in the closest segment to the reference inter-prediction sample of the current block, the weight coefficient for the first prediction sample of the current sample may be set to 6, and the weight coefficient for the second prediction sample may be set to 2, or when the current sample is located in the second closest segment to the reference inter-prediction sample of the current block, the weight coefficient for the first prediction sample of the current sample may be set to 5, and the weight coefficient for the second prediction sample may be set to 3, or when the current sample sample is located in the third closest segment to the reference inter-prediction sample of the current block, the weight coefficient for the first prediction sample of the current sample may be set to 3, and the weight coefficient for the second prediction sample may be set to 5, or when the current sample located in the segment farthest from the reference inter-prediction sample of the current block, the weight coefficient for the first prediction sample of the current sample may be set to 2, and the weight coefficient for the second prediction sample may be set to 6.

[201] Thereafter, the prediction sample of the current sample may be extracted by weighting average of the first prediction sample and the second prediction sample based on the weights. For example, the prediction sample may be extracted by the following equation.

[202] equation 1

[203] Herein, PCII _P may represent a prediction sample, P _intra may represent a first prediction sample, P _inter may represent a second prediction sample, wt may represent a weight for the first prediction sample, and (8-wt) may represent a weighting factor for the second prediction sample.

[204] Meanwhile, when intra-prediction is performed as described above, general intra-prediction, MRL and/or ISP may be applied. Here, various methods of generating MPM lists can be used in general intra-prediction, MRL and ISP. 67 intra-prediction modes can be used in general intra-prediction, 65 intra-prediction modes excluding planar intra-prediction mode and DC-intra-prediction mode can be used in MRL-based intra-prediction, and 66 intra-prediction modes , with the exception of DC-intra-prediction mode can be used with ISP. Since encoding/decoding is performed on three intra-predictions (general intra-prediction, MRL-based intra-prediction and ISP) using different numbers of intra-prediction modes, the method of generating MPM lists may be different for the corresponding intra-predictions.

[205] In particular, when general intra-prediction is performed, an MPM list including six potential MPM candidates can be constructed using all 67 intra-prediction modes. When MRL-based intra-prediction is performed, an MPM list including six potentially eligible MPM candidates can be constructed using all 65 intra-prediction modes except planar intra-prediction mode and DC-intra-prediction mode. Additionally, when ISP is executed, an MPM list including six potential MPM candidates can be constructed using 66 intra-prediction modes, excluding the DC-intra-prediction mode. Here, the MPM list can be constructed in a manner depending on whether the ISP partition type is a horizontal partition or a vertical partition.

[206] FIG. 12 illustrates an example of retrieving an MPM list according to the applied intra-prediction. Referring to FIG. 12, the decoding device can determine whether or not an MRL or ISP is applied to the current block (S1205). If the MRL or ISP is applied to the current block, the decoding apparatus may determine whether or not the MRL is applied to the current block (S1210). If the MRL is applied to the current block, the decoding apparatus may generate an MRL MPM list for the current block (S1215). Here, the MRL MPM list may be an MPM list generated through an MPM list generation method when MRL is applied. Next, the decoding device can parse the MPM index (S1220). The MPM index may indicate a potential candidate MPM candidate that is retrieved as an intra-prediction mode of the current block from among the potential candidate MPM candidates. The decoding apparatus may retrieve a candidate MPM candidate indicated by the MPM index from among the candidate MPM candidates of the MRL MPM list as the intra-prediction mode of the current block.

[207] If ISP instead of MRL is applied to the current block, the decoding device can generate an ISP MPM list for the current block (S1225). Here, the ISP MPM list may be an MPM list generated through an MPM list generation method when an ISP is applied. Thereafter, the decoding device can parse the MPM index (S1220). The decoding apparatus may retrieve a candidate MPM candidate indicated by the MPM index from among the candidate MPM candidates of the ISP MPM list as an intra-prediction mode of the current block.

[208] If any of the MRL and ISP are not applied to the current block, the decoding apparatus may parse the MPM flag for the current block (S1230). Next, the decoding apparatus can determine whether or not the intra-prediction mode of the current block is an MPM mode based on the MPM flag, i.e. whether or not the intra-prediction mode of the current block represents a potentially suitable MPM candidate included in the MPM list based on the MPM flag (S1235). Here, the MPM flag may indicate whether or not the intra-prediction mode of the current block is included in the MPM list.

[209] If the intra prediction mode of the current block is the MPM mode, the decoding apparatus can generate an MPM list in general intra prediction (S1240) and parse the MPM index for the current block (S1220). The decoding apparatus may retrieve a candidate MPM candidate indicated by the MPM index from among the candidate MPM candidates of the MPM list as an intra-prediction mode of the current block.

[210] On the other hand, if the intra-prediction mode of the current block is not an MPM mode, i.e. if the current block's intra-prediction mode is not included in the potentially eligible MPM options, the decoder may parse remaining intra-prediction mode information representing one of the remaining intra-prediction modes that is not included in the potentially eligible MPM options of the MPM list ( S1245). The decoding apparatus may extract the intra-prediction mode indicated by the information of the remaining intra-prediction modes from among the remaining intra-prediction modes as the intra-prediction mode of the current block.

[211] As described above, an MPM list including six potential MPM candidates can be configured in various ways according to intra-predictions. However, if the method of generating MPM lists depends on the method of performing intra-prediction, coding complexity may increase and coding efficiency may deteriorate.

[212] Accordingly, the present disclosure provides a method for modifying the MPM list generation methods used in traditional general intra-prediction, MRL-based intra-prediction and ISP to a generalized method. Thus, the present disclosure provides a method for generating an MPM list using a generalized method. It is possible to simplify the intra-prediction encoding/decoding structure and improve the encoding/decoding efficiency using the intra-prediction mode to improve video encoding efficiency by using a generalized MPM list generation method.

[213] As an embodiment, a method is provided for generating an MPM list using a generalized method and then applying a potentially suitable MPM candidate in the MPM list as an intra-prediction mode in conventional general intra-prediction, MRL-based intra-prediction and ISP intra-prediction.

[214] For example, a method for generating an MPM list including six potentially suitable MPM candidates used in conventional general intra-prediction can be used as a method for generating MPM lists for MRL-based intra-prediction and intra-prediction on ISP based. Here, the MPM list generation method may be a conventional MPM list generation method or a method improved from the conventional MPM list generation method. The above method of generating an MPM list including six potentially suitable MPM options used in conventional general intra-prediction is a method of generating an MPM list taking into account all 67 intra-prediction modes, and the MPM list may include the mode planar intra-prediction and/or DC-intra-prediction mode as potentially suitable MPM options. However, since the planar intra-prediction mode and DC-intra-prediction mode are not used in MRL-based intra-prediction, and the DC-intra-prediction mode is not used in ISP-based intra-prediction, the MPM list construction method different from the traditional method, may be required for MRL-based intra-prediction and ISP-based intra-prediction.

[215] FIG. 13 illustrates an example of constructing an MPM list of a current block and retrieving an intra-prediction mode according to the present embodiment. Referring to FIG. 13, the decoding device can determine whether or not an MRL or ISP is applied to the current block (S1310). If the MRL or ISP is applied to the current block, the decoding apparatus may generate an MPM list of the current block (S1320) and parse the MPM index for the current block (S1330). The decoding apparatus may retrieve a candidate MPM candidate indicated by the MPM index from among the candidate MPM candidates of the MPM list as an intra-prediction mode of the current block.

[216] If any of the MRL and ISP is not applied to the current block, the decoding apparatus may parse the MPM flag for the current block (S1340) and determine whether or not the intra-prediction mode of the current block is included in the MPM list based on the MPM -flag (S1350). The MPM flag may indicate whether or not the current block's intra-prediction mode is included in the potentially eligible MPM candidates of the MPM list.

[217] When the intra prediction mode of the current block is the MPM mode, i.e. when the MPM flag indicates that the intra prediction mode of the current block is included in the potential candidate MPM candidates of the MPM list (eg, when the MPM flag is 1), the decoding apparatus may generate an MPM list of the current block (S1320). Here, the MPM list may be identical to the MPM list generated when the MRL or ISP is applied to the current block. Then, the decoding apparatus can parse the MPM index for the current block (S1330) and extract the candidate MPM candidate indicated by the MPM index from among the candidate MPM candidates of the MPM list as the intra-prediction mode of the current block.

[218] On the other hand, when the intra-prediction mode of the current block is not an MPM mode, i.e. when the MPM flag indicates that the intra-prediction mode of the current block is not included in the potentially eligible MPM options of the MPM list (eg, when the MPM flag is 0), the decoder may parse the information of the remaining intra-prediction modes of the current block ( S1360). The decoding apparatus may extract the intra-prediction mode indicated by the information of the remaining intra-prediction modes from among the remaining intra-prediction modes as the intra-prediction mode for the current block.

[219] The MPM list generation method proposed in the present embodiment and widely used in general intra-prediction, MRL-based intra-prediction and ISP-based intra-prediction may be identical to the following examples.

[220] An example of a method for generating MPM lists may be as shown in the following table.

[221]

Table 3

Generalized method of MPM formation, example 1 (6 MPM)

[222] According to an example of the MPM list generation method shown in Table 3, the encoding device/decoding device can retrieve the candidate MPM candidate 0 as the intra-prediction mode of the left adjacent block relative to the current block, and can retrieve the candidate MPM candidate 1 as a DC intra-prediction mode if the retrieved potential candidate MPM candidate 0 is a planar intra-prediction mode, may retrieve the potential candidate MPM candidate 1 as a planar intra-prediction mode if the retrieved potential candidate MPM candidate 0 is not is a planar intra-prediction mode, can retrieve potentially eligible MPM option 2 as a vertical intra-prediction mode, can retrieve potentially eligible MPM option 3 as a horizontal intra-prediction mode, can retrieve potentially eligible MPM option 4 as intra-prediction mode corresponding to the mode number obtained by subtracting 4 from the mode number for the vertical intra-prediction mode, i.e. intra-prediction mode #46, and can retrieve a potentially suitable MPM variant 5 as the intra-prediction mode corresponding to the mode number obtained by adding 4 with the mode number for the vertical intra-prediction mode, i.e. mode #54 intra-prediction.

[223] Thereafter, the encoding device/decoding device can determine whether or not the intra-prediction mode of the left neighboring block with respect to the current block is identical to the intra-prediction mode of the upper neighboring block, and construct an MPM list based on whether or not the intra-prediction mode of the left neighboring block is identical to the intra-prediction mode of the upper neighboring block. For example, when the intra-prediction mode of the left neighbor block is identical to the intra-prediction mode of the upper neighbor block, the encoding device/decoding device can determine whether or not the mode number for the intra-prediction mode of the left neighbor block is greater than the mode number for the DC-intra mode. prediction mode, and if the mode number for the intra-prediction mode of the left adjacent block is greater than the mode number for the DC-intra-prediction mode, retrieve the MPM list of the current block, which includes the retrieved potential candidate MPM candidate 0 - potential candidate candidate MPM 5 , as described below.

[224] - mpm[0]=leftIntraDir

[225] - mpm[1]=PLANAR_IDX

[226] - mpm[2]=DC_IDX

[227] - mpm[3]=((leftIntraDir+offset)%mod)+2

[228] - mpm[4]=((leftIntraDir-1)%mod)+2

[229] - mpm[5]=((leftIntraDir+offset-1)%mod)+2

[230] Thus, a potential MPM candidate candidate 0 of the MPM list may be retrieved as a left neighbor block intra-prediction mode, a potential candidate MPM candidate MPM list 1 may be retrieved as a planar intra-prediction mode, a potential candidate MPM option 2 of the MPM list can be retrieved as a DC intra-prediction mode, a potentially suitable MPM option 3 of the MPM list can be retrieved as an intra-prediction mode having a mode number ((leftIntraDir+offset)%mod)+2, t .e. intra-prediction mode having a value obtained by performing modulo arithmetic on the sum of the mode number for the intra-prediction mode of the left adjacent block and offset and summing 2 with the result of modulo arithmetic as the mode number, potentially suitable MPM option 4 The MPM list can be retrieved as an intra-prediction mode having a mode number ((leftIntraDir-1)%mod)+2, i.e. an intra-prediction mode having a value obtained by performing modulo arithmetic on a value obtained by subtracting 1 from the mode number for the intra-prediction mode of the left adjacent block and adding 2 with the result of the modulo arithmetic as the mode number, and potentially a suitable MPM variant 5 of the MPM list can be retrieved as an intra-prediction mode having a mode number ((leftIntraDir+offset-1)%mod)+2, i.e. an intra-prediction mode having a value obtained by performing a modulo arithmetic operation on the sum of the mode number for the intra-prediction mode of the left adjacent block and (offset-1) and summing 2 with the result of the modulo arithmetic operation as the mode number.

[231] For example, if the intra-prediction mode of the left adjacent block is identical to the intra-prediction mode of the upper adjacent block, and the mode number for the intra-prediction mode of the left adjacent block does not exceed the mode number for the DC-intra-prediction mode, the encoder/device decoding can retrieve the MPM list of the current block, which includes the previously retrieved potential candidate MPM candidate 0 - potential candidate MPM candidate 5.

[232] On the other hand, if the intra-prediction mode of the left neighbor block is not identical to the intra-prediction mode of the upper neighbor block, for example, the encoder/decoder device may extract the intra-prediction mode of the left neighbor block relative to the current block as a potentially suitable MPM - MPM-list variant 0 and may retrieve the intra-prediction mode of the upper neighboring block relative to the current block as a potentially suitable MPM-list variant 1. Additionally, the encoder/decoder may retrieve maxCandModeIdx as 0 if the mode number of MPM candidate candidate 0 is greater than the mode number of MPM candidate candidate 1, and may retrieve maxCandModeIdx as 1 if the mode number of MPM candidate candidate 0 is 0 does not exceed the mode number of a potentially suitable MPM option 1.

[233] Then, if the mode number for the intra-prediction mode of the left adjacent block and the mode number for the intra-prediction mode of the upper adjacent block exceed the mode number for the DC-intra-prediction mode, the encoding device/decoding device can extract the planar intra-prediction mode into as a potential candidate MPM candidate 2 of the MPM list and may retrieve the DC intra-prediction mode as a potential candidate MPM candidate 3 of the MPM list.

[234] Then, if the value obtained by subtracting the mode number mpm[!maxCandModeIdx] from the mode number mpm[maxCandModeIdx] is less than 63 and greater than 1, the encoder/decoder may extract the intra-prediction mode having the mode number ((mpm[maxCandModeIdx ]+offset)%mod)+2 as a potential candidate MPM variant 4 of the MPM list and retrieve the intra-prediction mode having mode number ((mpm[maxCandModeIdx]-1)%mod)+2 as a potential candidate MPM variant 5 MPM list. Here, mpm[maxCandModeIdx] may indicate a potential candidate MPM candidate 0, and mpm[!maxCandModeIdx] may indicate a potential candidate MPM candidate 1, if maxCandModeIdx is 0 and mpm[maxCandModeIdx] may indicate a potential candidate MPM candidate 1, and mpm [!maxCandModeIdx] can indicate a potentially suitable MPM option 0 if maxCandModeIdx is 1.

[235] Additionally, if the value obtained by subtracting the mode number mpm[!maxCandModeIdx] from the mode number mpm[maxCandModeIdx] is equal to or greater than 63 or equal to or less than 1, the encoding device/decoding device may extract the intra-prediction mode having the number mode ((mpm[maxCandModeIdx]+offset-1)%mod)+2, as a potentially suitable MPM variant 4 of the MPM list, and can retrieve the intra-prediction mode having mode number ((mpm[maxCandModeIdx])%mod )+2, as a potentially suitable MPM variant of the 5 MPM list.

[236] For example, if at least one of the mode number for the intra-prediction mode of the left adjacent block and the mode number for the intra-prediction mode of the upper adjacent block does not exceed the mode number for the DC-intra-prediction mode, the encoder/device decoding may determine whether the sum of the mode number for the intra-prediction mode of the left neighbor block and the mode number for the intra-prediction mode of the upper neighbor block 2 is equal to or greater than or not, and if the sum of the mode number for the intra-prediction mode of the left neighbor block and the mode number for the intra-prediction mode of the upper neighboring block is equal to or greater than 2, extract potential candidate MPM candidate 2 - potential candidate MPM candidate 5 as follows.

[237] - mpm[2]=(mpm[!maxCandModeIdx]==PLANAR_IDX)? DC_IDX: PLANAR_IDX

[238] - mpm[3]=((mpm[maxCandModeIdx]+offset)%mod)+2

[239] - mpm[4]=((mpm[maxCandModeIdx]-1)%mod)+2

[240] - mpm[5]=((mpm[maxCandModeIdx]+offset-1)%mod)+2

[241] Thus, a potentially suitable MPM variant 2 of the MPM list may be retrieved as a DC intra-prediction mode if mpm[!maxCandModeIdx] is a planar intra-prediction mode, and may be retrieved as a planar intra-prediction mode , if mpm[!maxCandModeIdx] does not represent a planar intra-prediction mode. In addition, a potentially suitable MPM variant 3 of the MPM list may be retrieved as an intra-prediction mode having a mode number ((mpm[maxCandModeIdx]+offset)%mod)+2, i.e. intra-prediction mode having a value obtained by performing modulo arithmetic on the sum of mpm[maxCandModeIdx] and offset and summing 2 with the result of modulo arithmetic as the mode number, a potentially suitable MPM variant 4 of the MPM list can be retrieved into as an intra-prediction mode with mode number ((mpm[maxCandModeIdx]-1)%mod)+2, i.e. an intra-prediction mode having a value obtained by performing modulo arithmetic on a value obtained by subtracting 1 from mpm[maxCandModeIdx] and summing 2 with the result of modulo arithmetic as the mode number, and a potentially suitable MPM variant of 5 MPM -list can be retrieved as an intra-prediction mode having a mode number ((mpm[maxCandModeIdx]+offset-1)%mod)+2, i.e. an intra-prediction mode having a value obtained by performing modulo arithmetic on the sum of mpm[maxCandModeIdx] and (offset-1) and summing 2 with the result of modulo arithmetic as the mode number.

[242] Otherwise, another example of a method for generating MPM lists may be used. Another example of how MPM lists are generated could be as shown in the following table.

[243] Tab. 4

Generalized MPM shaping method, example 2 (6 MPM, identical to JVET-MO783)

[244] According to an example of the MPM list generation method shown in Table 4, the encoding device/decoding device can retrieve the candidate MPM candidate 0 for the current block as an intra-prediction mode of the left neighboring block with respect to the current block, can retrieve the potential candidate MPM -option 1 as a DC intra-prediction mode if the extracted potentially eligible MPM option 0 is a planar intra-prediction mode may retrieve a potentially eligible MPM option 1 as a planar intra-prediction mode if the extracted potentially eligible MPM- option 0 is not a planar intra-prediction mode, can retrieve a potentially suitable MPM option 2 as a vertical intra-prediction mode, can retrieve a potentially suitable MPM option 3 as a horizontal intra-prediction mode, can retrieve a potentially suitable MPM option 4 as the intra-prediction mode corresponding to the mode number obtained by subtracting 4 from the mode number for the vertical intra-prediction mode, i.e. intra-prediction mode #46, and can retrieve a potentially suitable MPM variant 5 as the intra-prediction mode corresponding to the mode number obtained by adding 4 with the mode number for the vertical intra-prediction mode, i.e. mode #54 intra-prediction.

[245] Thereafter, the encoding device/decoding device can determine whether or not the intra-prediction mode of the left neighboring block with respect to the current block is identical to the intra-prediction mode of the upper neighboring block, and construct an MPM list based on whether or not the intra-prediction mode of the left neighboring block is identical to the intra-prediction mode of the upper neighboring block. For example, when the intra-prediction mode of the left neighbor block is identical to the intra-prediction mode of the upper neighbor block, the encoding device/decoding device can determine whether or not the mode number for the intra-prediction mode of the left neighbor block is greater than the mode number for the DC-intra mode. prediction mode, and if the mode number for the intra-prediction mode of the left adjacent block is greater than the mode number for the DC-intra-prediction mode, retrieve the MPM list of the current block, which includes the retrieved potential candidate MPM candidate 0 - potential candidate candidate MPM 5 , as described below.

[246] - mpm[0]=leftIntraDir

[247] - mpm[1]=PLANAR_IDX

[248] - mpm[2]=((leftIntraDir+offset)%mod)+2

[249] - mpm[3]=((leftIntraDir-1)%mod)+2

[250] - mpm[4]=DC_IDX

[251] - mpm[5]=((leftIntraDir+offset-1)%mod)+2

[252] Thus, a potential MPM candidate candidate 0 of the MPM list may be retrieved as a left neighbor block intra-prediction mode, a potential candidate MPM candidate MPM list 1 may be retrieved as a planar intra-prediction mode, a potential candidate MPM option 2 of the MPM list can be retrieved as an intra-prediction mode having a mode number ((leftIntraDir+offset)%mod)+2, i.e. intra-prediction mode having a value obtained by performing modulo arithmetic on the sum of the mode number for the intra-prediction mode of the left adjacent block and offset and summing 2 with the result of modulo arithmetic as the mode number, potentially suitable MPM option 3 The MPM list can be retrieved as an intra-prediction mode having a mode number ((leftIntraDir-1)%mod)+2, i.e. an intra-prediction mode having a value obtained by performing a modulo arithmetic operation on a value obtained by subtracting 1 from the mode number for the intra-prediction mode of a left adjacent block and adding 2 to the result of the modulo arithmetic operation as the mode number, potentially suitable An MPM list MPM variant 4 may be retrieved as a DC intra-prediction mode, and a potentially suitable MPM list MPM variant 5 may be retrieved as an intra-prediction mode having a mode number ((leftIntraDir+offset-1)%mod )+2, i.e. an intra-prediction mode having a value obtained by performing a modulo arithmetic operation on the sum of the mode number for the intra-prediction mode of the left adjacent block and (offset-1) and summing 2 with the result of the modulo arithmetic operation as the mode number.

[253] For example, if the intra-prediction mode of the left adjacent block is identical to the intra-prediction mode of the upper adjacent block, and the mode number for the intra-prediction mode of the left adjacent block does not exceed the mode number for the DC-intra-prediction mode, the encoder/device decoding can retrieve the MPM list of the current block, which includes the previously retrieved potential candidate MPM candidate 0 - potential candidate MPM candidate 5.

[254] On the other hand, if the intra-prediction mode of the left neighbor block is not identical to the intra-prediction mode of the upper neighbor block, for example, the encoder/decoder device may extract the intra-prediction mode of the left neighbor block relative to the current block as a potentially suitable MPM - MPM-list variant 0 and may retrieve the intra-prediction mode of the upper neighboring block relative to the current block as a potentially suitable MPM-list variant 1. Additionally, the encoder/decoder may retrieve maxCandModeIdx as 0 if the mode number of MPM candidate candidate 0 is greater than the mode number of MPM candidate candidate 1, and may retrieve maxCandModeIdx as 1 if the mode number of MPM candidate candidate 0 is 0 does not exceed the mode number of a potentially suitable MPM option 1.

[255] Then, if the mode number for the intra-prediction mode of the left adjacent block and the mode number for the intra-prediction mode of the upper adjacent block exceed the mode number for the DC-intra-prediction mode, the encoding device/decoding device can extract the planar intra-prediction mode into as a potential candidate MPM candidate 1 of the MPM list and may retrieve the intra-prediction mode of the upper neighbor block as a potential candidate MPM candidate 2 of the MPM list. Additionally, the encoder/decoder may extract maxCandModeIdx as 0 if the mode number of MPM candidate candidate 0 is greater than the mode number of MPM candidate candidate 2, and may extract maxCandModeIdx as 2 if the mode number of MPM candidate candidate 0 is 0 does not exceed the mode number of MPM candidate 2. In addition, the encoder/decoder may extract minCandModeidx as 2 if the mode number of MPM candidate 0 is greater than the mode number of MPM candidate 2, and may extract maxCandModeIdx as as 0 if the mode number of the candidate MPM candidate 0 is not greater than the mode number of the candidate MPM candidate 2. Additionally, the encoder/decoder may extract the DC intra-prediction mode as the candidate MPM candidate 3 of the MPM list.

[256] Then, if the value obtained by subtracting the mode number mpm[minCandModeidx] from the mode number mpm[maxCandModeIdx] is less than 63 and greater than 1, the encoder/decoder may extract the intra-prediction mode having the mode number ((mpm[maxCandModeIdx ]+offset)%mod)+2 as a potential candidate MPM variant 4 of the MPM list and retrieve the intra-prediction mode having mode number ((mpm[maxCandModeIdx]-1)%mod)+2 as a potential candidate MPM variant 5 MPM list. Here, mpm[maxCandModeIdx] may represent a potential candidate MPM candidate 0 if maxCandModeIdx is 0, mpm[maxCandModeIdx] may represent a potential candidate MPM candidate 1 if maxCandModeIdx is 1, mpm[maxCandModeIdx] may represent a potential candidate MPM -option 2 if maxCandModeIdx is 2, mpm[minCandModeidx] may be a potential candidate MPM option 0 if minCandModeidx is 0 and mpm[minCandModeidx] may be a potential candidate MPM option 2 if minCandModeidx is 2.

[257] Additionally, if the value obtained by subtracting the mode number mpm[minCandModeidx] from the mode number mpm[maxCandModeIdx] is equal to or greater than 63 or equal to or less than 1, the encoding device/decoding device may extract the intra-prediction mode having the mode number ((mpm[maxCandModeIdx]+offset-1)%mod)+2, as a potentially suitable MPM variant 4 of the MPM list, and can retrieve the intra-prediction mode having the mode number ((mpm[maxCandModeIdx])%mod) +2, as a potentially suitable MPM option for the 5 MPM list.

[258] For example, if at least one of the mode number for the intra-prediction mode of the left adjacent block and the mode number for the intra-prediction mode of the upper adjacent block does not exceed the mode number for the DC-intra-prediction mode, the encoder/device decoding may determine whether the sum of the mode number for the intra-prediction mode of the left adjacent block and the mode number for the intra-prediction mode of the upper adjacent block 2 is equal to or greater than or not, and if the sum of the mode number for the intra-prediction mode of the left adjacent block and the mode number for the intra-prediction mode of the upper adjacent block is equal to or greater than 2, determine whether or not at least one of the intra-prediction mode of the left adjacent block and the intra-prediction mode of the upper adjacent block is identical to the planar intra-prediction mode.

[259] If at least one of the left neighbor block intra-prediction mode and the top neighbor block intra-prediction mode is identical to the planar intra-prediction mode, the encoder/decoder may extract a potential candidate MPM candidate 0 and a potential candidate MPM option 1 is as follows.

[260] - mpm[0]=PLANAR_IDX

[261] - mpm[1]=(leftIntraDir<aboveIntraDir)? aboveIntraDir: leftIntraDir

[262] Thus, a potential candidate MPM variant 0 of an MPM list may be retrieved as a planar intra-prediction mode, a potential candidate MPM variant 1 of an MPM list may be retrieved as an intra-prediction mode of an upper neighbor block if the mode number for the intra-prediction mode of the left neighbor block is less than the mode number for the intra-prediction mode of the upper neighbor block, and a potentially suitable MPM variant 1 of the MPM list can be retrieved as the intra-prediction mode of the left neighbor block if the mode number for the intra-prediction mode of the left of the neighboring block is equal to or greater than the mode number for the intra-prediction mode of the upper neighboring block. Additionally, maxCandModeIdx can be retrieved as 1.

[263] On the other hand, if the intra-prediction mode of the left neighbor block and the intra-prediction mode of the top neighbor block are not identical to the planar intra-prediction mode, the potential candidate MPM candidate 0 and the potential candidate MPM candidate 1 of the MPM list may in advance extract intra-prediction modes. Additionally, the maxCandModeIdx value may be retrieved in advance.

[264] Additionally, if the sum of the mode number for the intra-prediction mode of the left adjacent block and the mode number for the intra-prediction mode of the upper adjacent block is equal to or greater than 2, the encoding device/decoding device may extract the potential candidate MPM candidate 2 - the potential candidate MPM -option 5 as follows.

[265] - mpm[2]=(mpm[!maxCandModeIdx]==PLANAR_IDX)? DC_IDX: PLANAR_IDX

[266] - mpm[3]=((mpm[maxCandModeIdx]+offset)%mod)+2

[267] - mpm[4]=((mpm[maxCandModeIdx]-1)%mod)+2

[268] - mpm[5]=((mpm[maxCandModeIdx]+offset-1)%mod)+2

[269] Thus, a potentially suitable MPM variant 2 of the MPM list may be retrieved as a DC intra-prediction mode if mpm[!maxCandModeIdx] is a planar intra-prediction mode, and may be retrieved as a planar intra-prediction mode , if mpm[!maxCandModeIdx] does not represent a planar intra-prediction mode. In addition, a potentially suitable MPM variant 3 of the MPM list may be retrieved as an intra-prediction mode having a mode number ((mpm[maxCandModeIdx]+offset)%mod)+2, i.e. intra-prediction mode having a value obtained by performing modulo arithmetic on the sum of mpm[maxCandModeIdx] and offset and summing 2 with the result of modulo arithmetic as the mode number, a potentially suitable MPM variant 4 of the MPM list can be retrieved into as an intra-prediction mode with mode number ((mpm[maxCandModeIdx]-1)%mod)+2, i.e. an intra-prediction mode having a value obtained by performing modulo arithmetic on a value obtained by subtracting 1 from mpm[maxCandModeIdx] and summing 2 with the result of modulo arithmetic as the mode number, and a potentially suitable MPM variant of 5 MPM -list can be retrieved as an intra-prediction mode having a mode number ((mpm[maxCandModeIdx]+offset-1)%mod)+2, i.e. an intra-prediction mode having a value obtained by performing modulo arithmetic on the sum of mpm[maxCandModeIdx] and (offset-1) and summing 2 with the result of modulo arithmetic as the mode number.

[270] Otherwise, another example of a method for generating MPM lists may be used. Another example of how MPM lists are generated could be as shown in the following table.

[271] Tab. 5

Generalized MPM shaping method, example 3 (6 MPM, identical to VTM1.0)

[272] According to an example of the MPM list generation method shown in Table 5, the encoding device/decoding device can determine whether or not the intra-prediction mode of the left neighboring block with respect to the current block is identical to the intra-prediction mode of the upper neighboring block.

[273] If the intra prediction mode of the left neighbor block is identical to the intra prediction mode of the upper neighbor block, the encoding device/decoding device can determine whether the mode number for the intra prediction mode of the left neighbor block is greater than the mode number for the DC intra mode -prediction, and if the mode number for the intra-prediction mode of the left adjacent block is greater than the mode number for the DC-intra-prediction mode, may retrieve an MPM list of the current block that includes a potentially eligible MPM option 0 is a potentially eligible MPM option 2, extracted as described below.

[274] - mpm[0]=g_intraMode65to33AngMapping[leftIntraDir]

[275] - mpm[1]=((g_intraMode65to33AngMapping[leftIntraDir]+offset)%mod)+2

[276] - mpm[2]=((g_intraMode65to33AngMapping[leftIntraDir]-1)%mod)+2

[277] Thus, a potentially suitable MPM variant 0 of the MPM list can be retrieved as the intra-prediction mode of the left neighbor block. In addition, a potentially suitable MPM variant 1 of the MPM list can be retrieved as an intra-prediction mode having a mode number ((g_intraMode65to33AngMapping[leftIntraDir]+offset)%mod)+2, i.e. an intra-prediction mode having a value obtained by performing modulo arithmetic on the sum of the mode number for the intra-prediction mode of the left adjacent block and offset and summing 2 with the result of the modulo arithmetic as the mode number, and a potentially suitable MPM variant 2 MPM list can be retrieved as an intra-prediction mode having a mode number ((g_intraMode65to33AngMapping[leftIntraDir]-1)%mod)+2, i.e. an intra-prediction mode having a value obtained by performing a modulo arithmetic operation on a value obtained by subtracting 1 from the mode number for the intra-prediction mode of the left adjacent block and adding 2 with the result of the modulo arithmetic operation as the mode number.

[278] If the mode number for the intra-prediction mode of the left adjacent block is equal to or less than the mode number for the DC-intra-prediction mode, the encoder/decoder may retrieve an MPM list of the current block that includes a potentially suitable MPM option 0 - Potentially suitable MPM option 2, extracted as described below.

[279] - mpm[0]=g_intraMode65to33AngMapping[PLANAR_IDX]

[280] - mpm[1]=g_intraMode65to33AngMapping[DC_IDX]

[281] - mpm[2]=g_intraMode65to33AngMapping[VER_IDX]

[282] Thus, the potential MPM candidate candidate 0 of the MPM list can be retrieved as a planar intra-prediction mode, the potential candidate MPM variant 1 of the MPM list can be retrieved as the DC intra-prediction mode, and the potential candidate MPM-list option 2 of the MPM list can be retrieved as a vertical intra-prediction mode.

[283] On the other hand, the intra-prediction mode of the left neighbor block is not identical to the intra-prediction mode of the upper neighbor block, the encoder/decoder may extract a potentially suitable MPM variant 0 as the intra-prediction mode of the left neighbor block relative to the current block and can retrieve a potentially suitable MPM option 1 as the intra-prediction mode of the upper neighboring block relative to the current block.

[284] If both the left neighbor block intra-prediction mode and the top neighbor block intra-prediction mode are not planar intra-prediction mode, the encoder/decoder device may retrieve a potentially suitable MPM variant 2 as the planar intra-prediction mode. If at least one of the intra-prediction mode of the left adjacent block and the intra-prediction mode of the upper adjacent block is a planar intra-prediction mode, the encoding apparatus/decoding apparatus may determine whether the sum of the mode number for the intra-prediction mode is less than or equal to prediction of the left neighboring block and the mode number for the intra-prediction mode of the upper neighboring block 2, extract a potentially suitable MPM variant 2 as the vertical intra-prediction mode if the sum of the mode number for the intra-prediction mode of the left neighboring block and the mode number for the intra-mode -prediction of the top neighbor block is less than 2, and extract a potentially suitable MPM option 2 as the DC intra-prediction mode if the sum of the mode number for the intra-prediction mode of the left neighbor block and the mode number for the intra-prediction mode of the top neighbor block is equal to or above 2.

[285] In addition, the present disclosure provides another embodiment of modifying the MPM list generation methods used in traditional general intra-prediction, MRL-based intra-prediction and ISP-based intra-prediction to a generalized method. A method is proposed that does not take into account the intra-prediction mode, which is not used for multiple reference line intra-prediction and sub-segment-based intra-prediction at the encoder stage.

[286] As an example, when the encoder performs intra-prediction of a multiple reference line, the encoder performs inter-prediction only taking into account the intra-prediction modes included in the MPM list. For example, an example in which intra-prediction modes that are not used for MRL and/or ISP are not considered in MPM list generation may be proposed in the present embodiment.

[287] Thus, when the encoding device performs intra-prediction based on the MRL, for example, the encoding device may perform intra-prediction only taking into account the intra-prediction modes included in the MPM list. Thus, when the MPM list includes a planar intra-prediction mode or a DC-intra-prediction mode, the encoding device may not select the planar intra-prediction mode or the DC-intra-prediction mode as the intra-prediction mode of the current block in the present embodiment. Additionally, as an example similar to the above example, when the encoding apparatus performs ISP, the encoding apparatus may skip the DC intra-prediction mode when the MPM list includes the DC intra-prediction mode.

[288] The MPM mode generation method and the mode-based decoding method proposed in the present embodiment may be identical to the MPM mode generation method and the mode-based decoding method of the above-described embodiment, and may include a feature in which a particular intra mode -predictions are not taken into account only during encoding. Accordingly, the coding efficiency may be reduced to some extent during encoding and decoding of the MPM index, but the complexity of hardware and software implementation can be reduced according to the formation of a generalized MPM list, and intra-prediction based on MRL and ISP that does not use a specific mode can be supported. intra-predictions.

[289] The present embodiment provides a method for performing intra-prediction, by an encoding device, regardless of the specific intra-prediction mode when MRL-based and/or ISP-based intra-prediction is applied. In this case, the MPM index parsed by the decoding apparatus may not indicate a particular intra-prediction mode.

[290] For example, an example may be provided in which encoding using the planar intra-prediction mode and the DC-intra-prediction mode when MRL-based intra-prediction is applied is prohibited, and encoding using the DC-intra-prediction mode is prohibited. when ISP is applied.

[291] FIG. 14 illustrates an example of intra-prediction based coding according to the present embodiment. Referring to FIG. 14, the encoder can determine whether or not an MRL or ISP is applied to the current block (S1405). If the MRL or ISP is applied to the current block, the encoder can determine whether the MRL is applied or not (S1410).

[292] If the MRL is applied to the current block, the encoder can generate an MPM list for the current block through the MPM list generation process (S1415). Thereafter, the encoder can perform intra-prediction for the current block based on the potential MPM candidates in the MPM list, excluding the planar intra-prediction mode and the DC-intra-prediction mode, (i.e., the intra-prediction modes retrieved as potentially suitable MPM candidates of the MPM list, excluding the planar intra-prediction mode and the DC-intra-prediction mode) (S1420), and select the optimal intra-prediction mode for the current block (S1425).

[293] If the ISP is applied to the current block instead of the MRL, the encoder can generate an MPM list for the current block through the MPM list generation process (S1430). Here, the MPM list generation process may be identical to the above-described MPM list generation process performed when MRL is applied. Thereafter, the encoder may perform intra-prediction for the current block based on the candidate MPM candidates in the MPM list, excluding the DC intra-prediction mode (i.e., intra-prediction modes retrieved as candidate MPM candidates). options of the MPM list, except for the DC intra-prediction mode) (S1435), and select the optimal intra-prediction mode for the current block (S1440).

[294] If MRL and ISP are not applied to the current block, the encoding device may perform general intra-prediction for the current block based on the 67 intra-prediction modes (S1445) and select the optimal intra-prediction mode for the current block (S1450).

[295] As another example, an example may be provided in which encoding using the planar intra-prediction mode when MRL-based intra-prediction is applied is prohibited, and encoding using the DC intra-prediction mode is prohibited when ISP is applied.

[296] FIG. 15 illustrates an example of intra-prediction based coding according to the present embodiment. Referring to FIG. 15, the encoder can determine whether or not an MRL or ISP is applied to the current block (S1505). If the MRL or ISP is applied to the current block, the encoder can determine whether the MRL is applied or not (S1510).

[297] If the MRL is applied to the current block, the encoder can generate an MPM list for the current block through the MPM list generation process (S1515). Thereafter, the encoder may perform intra-prediction for the current block based on the candidate MPM candidates in the MPM list, excluding the planar intra-prediction mode (i.e., intra-prediction modes retrieved as candidate MPM candidates MPM list, excluding planar intra-prediction mode) (S1520), and select the optimal intra-prediction mode for the current block (S1525).

[298] If the ISP is applied to the current block instead of the MRL, the encoder can generate an MPM list for the current block through the MPM list generation process (S1530). Here, the MPM list generation process may be identical to the above-described MPM list generation process performed when MRL is applied. Thereafter, the encoder may perform intra-prediction for the current block based on the candidate MPM candidates in the MPM list, excluding the DC intra-prediction mode (i.e., intra-prediction modes retrieved as candidate MPM candidates). options of the MPM list, except for the DC intra-prediction mode) (S1535), and select the optimal intra-prediction mode for the current block (S1540).

[299] If MRL and ISP are not applied to the current block, the encoding device may perform general intra-prediction for the current block based on the 67 intra-prediction modes (S1545) and select the optimal intra-prediction mode for the current block (S1550).

[300] As another example, an example may be provided in which encoding using the planar intra-prediction mode when MRL-based intra-prediction is applied is prohibited.

[301] FIG. 16 illustrates an example of intra-prediction based coding according to the present embodiment. Referring to FIG. 16, the encoder can determine whether or not an MRL or ISP is applied to the current block (S1605). If the MRL or ISP is applied to the current block, the encoder can determine whether the MRL is applied or not (S1610).

[302] If the MRL is applied to the current block, the encoder can generate an MPM list for the current block through the MPM list generation process (S1615). Thereafter, the encoder may perform intra-prediction for the current block based on the candidate MPM candidates in the MPM list, excluding the planar intra-prediction mode (i.e., intra-prediction modes retrieved as candidate MPM candidates MPM list, excluding the planar intra-prediction mode) (S1620), and select the optimal intra-prediction mode for the current block (S1625).

[303] If the ISP is applied to the current block instead of the MRL, the encoder can generate an MPM list for the current block through the MPM list generation process (S1630). Here, the MPM list generation process may be identical to the above-described MPM list generation process performed when MRL is applied. Thereafter, the encoding apparatus may perform intra-prediction for the current block based on the candidate MPM candidates in the MPM list (i.e., the intra-prediction modes retrieved as the candidate MPM candidates of the MPM list) (S1635), and select the optimal intra-prediction mode for the current block (S1640).

[304] If MRL and ISP are not applied to the current block, the encoder may perform general intra-prediction for the current block based on the 67 intra-prediction modes (S1645) and select the optimal intra-prediction mode for the current block (S1650).

[305] Meanwhile, the present disclosure proposes a method for more efficiently performing intra-prediction performed based on the DC-intra-prediction mode when MRL is applied. For example, the present embodiment proposes a method for calculating a DC value when the DC intra-prediction mode is applied in MRL-based intra-prediction (i.e., when the intra-prediction type of the current block is MRL, and the intra-prediction mode of the current block represents DC-intra-prediction mode).

[306] FIG. 17 illustrates a reference sample used to extract a DC value when the intra-prediction type of the current block is MRL and the intra-prediction mode of the current block is a DC-intra-prediction mode.

[307](a) of FIG. 17 may represent a reference sample used to extract a DC value when the current block is a square block. For example, when the reference line indicated by the reference line index is reference line 0, reference line 1, reference line 2 or reference line 3, the DC value can be extracted based on the reference samples in the area (1700) shown in (a ) according to Fig. 17. Thus, the DC value can be retrieved based on the number of reference samples equal to the width from the left reference sample in the top reference line of the current block, and the number of reference samples equal to the width from the top end reference sample in the left reference line of the current block. block. In other words, when the size of the current block is WxH, and the X-axis component and the Y-axis component of the top left position of the current block are 0, the DC value can be retrieved based on the reference sample with coordinates (0,-refIdx-1) before the reference coordinate sample (W-1,-refIdx-1) at the upper reference line indicated by the reference line index, and coordinate reference sample (-refIdx-1, 0) to the coordinate reference sample (-refIdx-1 , H-1) in the left reference line, indicated by the reference line index.

[308] For example, the DC value may be retrieved as the following equation.

[309] equation 2

[310] Herein, dcVal may represent a DC value, nTbW may represent a width of the current block, refIdx may represent a reference line indicated by a reference line index.

[311] Additionally, (b) of FIG. 17 may represent a reference sample used to extract a DC value when the current block is a non-square block. In the present embodiment, when the current block is a non-square block, the DC value can be extracted based on the reference samples in the reference line on the longer side from the width and height of the current block. For example, when the reference line indicated by the reference line index is reference line 0, reference line 1, reference line 2 or reference line 3, the DC value can be extracted based on the reference samples in the reference line area (1710) on the longer reference line side of the width and height of the current block. For example, when the width of the current block exceeds the height, the DC value may be retrieved based on the number of reference samples identical to the width from the left reference sample in the top reference line of the current block. In other words, when the size of the current block is WxH, and the X-axis component and the Y-axis component of the top left position of the current block are 0, the DC value can be retrieved based on the reference sample with coordinates (0,-refIdx-1) before the reference discrete reference with coordinates (W-1,-refIdx-1) in the upper reference line, indicated by the reference line index. The DC value can be retrieved as the following equation.

[312] equation 3

[313] Herein, dcVal may represent a DC value, nTbW may represent a width of the current block, refIdx may represent a reference line indicated by a reference line index.

[314] In addition, for example, when the width of the current block is less than the height, the DC value may be extracted based on the number of reference samples identical to the height from the upper end reference sample in the left reference line of the current block. In other words, when the size of the current block is WxH, and the X-axis component and the Y-axis component of the top left position of the current block are 0, the DC value can be retrieved based on the reference sample with coordinates (-refIdx-1, 0) before the reference discrete reference with coordinates (-refIdx-1, H-1) in the left reference line, indicated by the reference line index. The DC value can be retrieved as the following equation.

[315] equation 4

[316] Herein, dcVal may represent a DC value, nTbH may represent the height of the current block, refIdx may represent a reference line indicated by a reference line index.

[317] Thereafter, the prediction sample of the current block can be retrieved as a DC value.

[318] Meanwhile, the present disclosure proposes a method for more efficiently performing intra-prediction performed based on a planar intra-prediction mode when MRL is applied. For example, the present embodiment provides a method for determining reference samples for planar prediction when the planar intra-prediction mode is applied in MRL-based intra-prediction (i.e., when the intra-prediction type of the current block is MRL, and the intra-prediction mode is prediction of the current block is a planar intra-prediction mode).

[319] FIG. 18 illustrates a reference sample used when the intra-prediction type of the current block is MRL, and the intra-prediction mode of the current block is the planar intra-prediction mode.

[320] Referring to FIG. 18, when the reference line indicated by the reference line index is reference line 0, reference line 1, reference line 2 or reference line 3, planar prediction can be performed based on the reference samples in the reference line region (1800) shown in FIG. . 18. According to the present embodiment, planar prediction can be performed based on a discrete end+1 sample from the width/height of the current block, regardless of the reference line index. That is, according to the present embodiment, when the X-axis component and the Y-axis component of the top left position of the current block are 0, the intra-prediction type of the current block is MRL, and the intra-prediction mode of the current block is the planar intra-prediction mode , planar prediction for the current block can be performed based on a reference sample with coordinates (W,-refIdx-1) in the top reference line and a reference sample with coordinates (-refIdx-1, H) in the left reference line.

[321] Referring to the present embodiment, planar intra prediction can be performed using the reference samples of the reference line indicated by the reference line index, and specifically, planar intra prediction can be performed based on the left reference samples in the identical row (i.e. identical to the Y coordinate) with the position of the current discrete sample in the current block and the top reference discrete sample in an identical column (i.e. identical to the X coordinate) with the position of the current discrete sample, from the reference discrete samples of the reference line and the reference discrete sample with coordinates (W ,-refIdx-1) in the upper reference line and a reference discrete sample with coordinates (-refIdx-1, H) in the left reference line. In this case, the prediction sample value of the current sample can be retrieved by performing bidirectional linear interpolation based on the values of the above-described four reference samples. Here, bidirectional linear interpolation can be performed under the condition that the left lower reference sample is located at the bottom side of the current sample, and the right upper reference sample is located at the right side of the current sample.

[322] Meanwhile, an embodiment different from the embodiments of the MPM list generation method widely used in the above-described general intra-prediction, MRL and ISP can be used. Thus, the present disclosure offers another example of a method for generating MPM lists widely used in general intra-prediction, MRL and ISP. Another example of how MPM lists are generated could be as shown in the following table.

[323] Tab. 6

[324] According to an example of the MPM list generation method shown in Table 6, the encoding device/decoding device can extract the intra-prediction mode of the left neighboring block and the intra-prediction mode of the upper neighboring block with respect to the current block. The intra-prediction mode of the left adjacent block may be expressed as leftIntraDir, and the intra-prediction mode of the upper adjacent block may be expressed as aboveIntraDir.

[325] In addition, for example, the encoder/decoder may retrieve the default MPM list. For example, the encoder/decoder may retrieve the planar intra-prediction mode as the default MPM candidate candidate 0, the DC intra-prediction mode as the default MPM candidate candidate 1, the vertical mode intra-prediction as a potential candidate MPM candidate 2 of the default MPM list, horizontal intra-prediction mode as a potential candidate MPM candidate 3 of the default MPM list, intra-prediction mode of the mode number obtained by subtracting 4 from the mode number for the vertical intra-prediction mode, i.e. intra-prediction mode #46 as a potentially suitable MPM option 4 of the default MPM list, the intra-prediction mode of the mode number obtained by adding 4 with the mode number for the vertical intra-prediction mode, i.e. intra-prediction mode #54 as a potentially suitable MPM option 5 for the default MPM list.

[326] Thereafter, the encoding apparatus/decoding apparatus can determine whether or not the intra-prediction mode of the left neighboring block and the intra-prediction mode of the upper neighboring block with respect to the current block are identical, and whether or not the mode number for the intra-prediction mode is greater than or equal to left adjacent block prediction mode number for DC-intra-prediction mode.

[327] For example, when the intra-prediction mode of the left adjacent block and the intra-prediction mode of the upper adjacent block are identical, and the mode number for the intra-prediction mode of the left adjacent block is greater than the mode number for the DC-intra-prediction mode, the encoder/device The decoder may retrieve an MPM list of the current block including the retrieved candidate MPM candidate 0 through candidate candidate MPM 5, as described below.

[328] - mpm[0]=PLANAR_IDX

[329] - mpm[1]=leftIntraDir

[330] - mpm[2]=2+((leftIntraDir+61)%64)

[331] - mpm[3]=2+((leftIntraDir-1)%64)

[332] - mpm[4]=DC_IDX

[333] - mpm[5]=2+((leftIntraDir+60)%64)

[334] Thus, a potential MPM candidate candidate 0 of the MPM list may be retrieved as a planar intra-prediction mode, a potential candidate MPM candidate 1 of the MPM list may be retrieved as a left neighbor block intra-prediction mode, a potential candidate MPM option 2 of the MPM list can be retrieved as an intra-prediction mode having mode number 2+((leftIntraDir+61)%64), i.e. an intra-prediction mode having a value obtained by performing a modulo 64 arithmetic operation on a value obtained by adding 61 to the mode number for the intra-prediction mode of the left adjacent block and adding 2 to the result of the modulo arithmetic operation as the mode number, a potentially suitable MPM variant 3 of the MPM list may be retrieved as an intra-prediction mode having mode number 2+((leftIntraDir-1)%64), i.e. an intra-prediction mode having a value obtained by performing a modulo 64 arithmetic operation on a value obtained by subtracting 1 from the mode number for the intra-prediction mode of the left adjacent block and adding 2 with the result of the modulo arithmetic operation as the mode number, a potential candidate MPM candidate 4 of the MPM list may be retrieved as a DC intra-prediction mode, and a potential candidate MPM candidate 5 of the MPM list may be retrieved as an intra-prediction mode having mode number 2+((leftIntraDir+60) %64), i.e. an intra-prediction mode having a value obtained by performing a modulo 64 arithmetic operation on a value obtained by adding 60 to the mode number for the intra-prediction mode of the left adjacent block and adding 2 to the result of the modulo arithmetic operation as the mode number.

[335] Meanwhile, when the intra-prediction mode of the left neighboring block relative to the current block and the intra-prediction mode of the upper neighboring block are not identical, the encoding device/decoding device can determine that the mode number for the intra-prediction mode of the left neighboring block exceeds the mode number for the DC-intra-prediction mode, and the mode number for the intra-prediction mode of the upper adjacent block is greater than the mode number for the DC-intra-prediction mode.

[336] When the mode number for the intra-prediction mode of the left adjacent block exceeds the mode number for the DC-intra-prediction mode, and the mode number for the intra-prediction mode of the upper adjacent block exceeds the mode number for the DC-intra-prediction mode, the encoder/ The decoding device may extract the planar intra-prediction mode as a potential MPM candidate candidate 0 of the MPM list, the intra-prediction mode of the left neighbor block as a potential candidate MPM candidate 1 of the MPM list, the intra-prediction mode of the top neighbor block as a potential a suitable MPM variant 2 of the MPM list, a DC intra-prediction mode as a potentially suitable MPM variant 3 of the MPM list. In addition, when the mode number of potential MPM candidate 1 is greater than the mode number of potential MPM candidate 2, the encoder/decoder may extract maxCandModeIdx as 1 when the mode number of potential MPM candidate 1 is not greater than the mode number of potential MPM candidate -Option 2, the encoder/decoder may extract maxCandModeIdx as 2.

[337] Thereafter, when the value obtained by subtracting the mode number mpm[minCandModeidx] from the mode number mpm[maxCandModeIdx] is less than 63 and greater than 1, the encoding device/decoding device can extract the intra-prediction mode with mode number 2+(( maxAB+61)%64) as a potentially eligible MPM option 4 of the MPM list and intra-prediction mode with mode number 2+((maxAB-1)%64) as a potentially eligible MPM option 5 of the MPM list. Here, when maxCandModeIdx is equal to 1, mpm[maxCandModeIdx] may represent a potential eligible MPM option 1, when maxCandModeIdx is equal to 2, mpm[maxCandModeIdx] may represent a potential eligible MPM option 2, when minCandModeidx is equal to 1, mpm[minCandModeidx] may represent a potential candidate MPM candidate 1, when minCandModeidx is 2, mpm[minCandModeidx] may represent a potential candidate MPM candidate 2. In addition, here, maxAB can be the larger value of the mode number for the intra-prediction mode of the left neighbor block and number mode for the intra-prediction mode of the upper neighboring block.

[338] Alternatively, when the value obtained by subtracting the mode number mpm[minCandModeidx] from the mode number mpm[maxCandModeIdx] is greater than or equal to 63 or less than or equal to 1, the encoder/decoder may extract the intra-prediction mode with mode number 2 +((maxAB+60)%64) as a potentially suitable MPM variant 4 of the MPM list and the intra-prediction mode with mode number 2+(maxAB%64) as a potentially suitable MPM variant 5 of the MPM list.

[339] Meanwhile, when the intra-prediction mode of the left adjacent block and the intra-prediction mode of the upper adjacent block with respect to the current block are not identical, or at least one of the mode numbers for the intra-prediction mode of the left adjacent block and the intra-prediction mode - the prediction of the upper adjacent block is less than the mode number for the DC intra-prediction mode, the encoding device/decoding device can determine whether the sum of the mode number for the intra-prediction mode of the left adjacent block and the mode number for the intra-prediction mode of the upper adjacent mode number block for DC-intra-prediction mode.

[340] When the sum of the mode number for the intra-prediction mode of the left adjacent block and the mode number for the intra-prediction mode of the upper adjacent block is equal to or greater than the mode number for the DC-intra-prediction mode, the encoding device/decoding device may retrieve the MPM list of the current block including the extracted potential MPM candidate 0 - potential MPM candidate 5, as described below.

[341] - mpm[0]=PLANAR_IDX

[342] - mpm[1]=(leftIntraDir<aboveIntraDir)? aboveIntraDir:leftIntraDir

[343] - mpm[2]=DC_IDX

[344] 2+((maxAB+61)%64)

[345] - mpm[4]=2+((maxAB-1)%64)

[346] - mpm[5]=2+((maxAB+60)%64)

[347] Thus, a potential MPM candidate candidate 0 of an MPM list may be retrieved as a planar intra-prediction mode, a potential candidate MPM candidate 1 of an MPM list may be retrieved as an intra-prediction mode of an upper neighbor block when the mode number for the intra-prediction mode of the left neighbor block is less than the mode number for the intra-prediction mode of the upper neighbor block, a potentially suitable MPM variant 1 of the MPM list can be retrieved as the intra-prediction mode of the left neighbor block when the mode number for the intra-prediction mode of the left neighbor block is greater than or equal to the mode number for the intra-prediction mode of the left adjacent block, a potential candidate MPM variant 2 of the MPM list may be retrieved as a DC-intra-prediction mode, a potential candidate MPM variant 3 of the MPM list may be retrieved as an intra mode -prediction with mode number 2+((maxAB+61)%64), i.e. an intra-prediction mode having a value obtained by performing an arithmetic operation modulo 64 on the value obtained by adding 61 with the larger value of the mode number for the intra-prediction mode of the left adjacent block and the mode number for the intra-prediction mode of the upper adjacent block and summing 2 with the result of the modulo arithmetic operation as a mode number, a potentially suitable MPM variant 4 of the MPM list can be retrieved as an intra-prediction mode having a mode number 2+((maxAB-1)%64), i.e. . an intra-prediction mode having a value obtained by performing a modulo-64 arithmetic operation on a value obtained by subtracting 1 from the larger value from the mode number for the intra-prediction mode of the left adjacent block and the mode number for the intra-prediction mode of the upper adjacent block, and summing 2 with the result of the modulo arithmetic operation as a mode number, a potentially suitable MPM variant 5 of the MPM list can be retrieved as an intra-prediction mode having a mode number 2+((maxAB+60)%64), i.e. . an intra-prediction mode having a value obtained by performing a modulo 64 arithmetic operation on a value obtained by adding 60 with the larger value of the mode number for the intra-prediction mode of the left adjacent block and the mode number for the intra-prediction mode of the upper adjacent block and summing 2 with the result of the modulo arithmetic operation as the mode number.

[348] Meanwhile, an embodiment of the above-described method for generating an MPM list can be shown in the following table as source code.

[349] Tab. 7

Generalized MPM generation method 1 (6 MPM), version based on source code

[350]

[351] In addition, an embodiment of the above-described method for generating an MPM list can be shown in the following table in a standard format.

[352] Tab. 8

Generalized method 1 MPM formation (6 MPM) specification version 8.4.2 from the VVC specification

Extraction process for luminance intra-prediction mode

The inputs to this process are as follows:

- location (xCb, yCb) of the luminance signal indicating the upper left sample of the current luminance coding block relative to the upper left sample of the luminance signal of the current frame,

- variable cbWidth, indicating the width of the current coding block in discrete samples of the brightness signal,

- variable cbHeight, indicating the height of the current encoding block in discrete samples of the brightness signal. In this process, the intra-prediction mode of luminance signals IntraPredModeY[xCb][yCb] is extracted.

Table 8-1 specifies the meaning for the intraprediction mode IntraPredModeY[xCb][yCb] and associated names.

Table 8-1. Specification of intra-prediction mode and associated names Intra-prediction mode Associated title 0 INTRA_PLANAR 1 INTRA_DC 2...66 INTRA_ANGULAR2...INTRA_ANGULAR66 81...83 INTRA_LT_CCLM, INTRA_L_CCLM, INTRA_T_CCLM

Note: The intra prediction modes INTRA_LT_CCLM, INTRA_L_CCLM and INTRA_T_CCLM are only applicable to chrominance signal components.

IntraPredModeY[xCb][yCb] is retrieved through the following ordered steps:

1. Neighboring locations (xNbA, yNbA) and (xNbB, yNbB) are set to (xCb-1, yCb+cbHeight-1) and (xCb+cbWidth-1, yCb-1), respectively.

2. To replace X by A or by B, the candIntraPredModeX variables are retrieved as follows:

- The process of retrieving availability for a block, as specified in Section 6.4.X [Ed. (BB): Neighbor Block Availability Process, TBD] is activated with location (xCurr, yCurr) set to (xCb, yCb) and neighbor location (xNbY, yNbY) set to (xNbX, yNbX) as inputs, and the output is assigned to availableX.

- A potentially suitable intraprediction mode candIntraPredModeX is retrieved as follows:

- If one or more of the following conditions are true, candIntraPredModeX is set to INTRA_PLANAR.

- The availableX variable is false.

CuPredMode[xNbX][yNbX] is not equal to MODE_INTRA, and ciip_flag[xNbX][yNbX] is not equal to 1.

- pcm_flag[xNbX][yNbX] is equal to 1.

X is equal to B, and yCb-1 is less than ((yCb>>CtbLog2SizeY)<<CtbLog2SizeY). Otherwise, candIntraPredModeX is set to IntraPredModeY[xNbX][yNbX].

[353] 3. candModeList[x] with x=0...5 is retrieved as follows:

- If candIntraPredModeB is equal to candIntraPredModeA, and candIntraPredModeA is greater than INTRA_DC, candModeList[x] with x=0...5 is retrieved as follows:

- candModeList[0]=INTRA_PLANAR (8-9)

- candModeList[1]=candIntraPredModeA (8-10)

- candModeList[2]=2+((candIntraPredModeA+61)%64) (8-12)

- candModeList[3]=2+((candIntraPredModeA-1)%64) (8-13)

- candModeList[4]=INTRA_DC (8-11)

- candModeList[5]=2+((candIntraPredModeA+60)%64) (8-14)

- Otherwise, if candIntraPredModeB is not equal to candIntraPredModeA, and candIntraPredModeA or candIntraPredModeB exceeds INTRA_DC, the following applies:

- The minAB and maxAB variables are retrieved as follows: - minAB=Min(candIntraPredModeA, candIntraPredModeB) (8-24)

- maxAB=Max(candIntraPredModeA, candIntraPredModeB) (8-25)

- If candIntraPredModeA and candIntraPredModeB are greater than INTRA_DC, candModeList[x] with x=0...5 is retrieved as follows:

- candModeList[0]= INTRA_PLANAR (8-26)

- candModeList[1]=candIntraPredModeA (8-27)

- candModeList[2]=candIntraPredModeB

- candModeList[3]=INTRA_DC (8-29)

- If maxAB-minAB is in the range 2-62, inclusive, the following applies:

- candModeList[4]=2+((maxAB+61)%64) (8-30)

- candModeList[5]=2+((maxAB-1)%64) (8-31)

- Otherwise, the following applies:

- candModeList[4]=2+((maxAB+60)%64) candModeList[5] (8-32)=2+((maxAB)%64) (8-33)

[354] - Otherwise (candIntraPredModeA or candIntraPredModeB exceeds INTRA_DC), candModeList[x] with x=0...5 is retrieved as follows:

- candModeList[0]=INTRA_PLANAR (8-64)

- candModeList[1]=maxAB (8-65)

candModeList[2]=INTRA_DC (8-66)

- candModeList[3]=2+((maxAB+61)%64) (8-66)

- candModeList[4]=2+((maxAB-1)%64) (8-67)

- candModeList[5]=2+((maxAB+60)%64) (8-68)

- Otherwise, the following applies:

- candModeList[0]=INTRA_PLANAR (8-70)

- candModeList[1]=INTRA_DC (8-71)

- candModeList[2]=INTRA_ANGULAR50 (8-72)

- candModeList[3]=INTRA_ANGULAR18 (8-73)

- candModeList[4]=INTRA_ANGULAR46 (8-74)

- candModeList[5]=INTRA_ANGULAR54 (8-75)

(8-81)

4. IntraPredModeY[xCb][yCb] is retrieved by applying the following procedure:

- If intra_luma_mpm_flag[xCb][yCb] is equal to 1, IntraPredModeY[xCb][yCb] is set to candModeList [intra_luma_mpm_idx[xCb][yCb]].

- Otherwise, IntraPredModeY[xCb][yCb] is retrieved by applying the following ordered steps:

1. When candModeList[i] exceeds candModeList[j] for i=0...4 and for each i, j=(i+1)...5, both values are rearranged as follows:

(candModeList[i], candModeList[j])=Swap(candModeList[i], candModeList[j]) (8-94)

2. IntraPredModeY[xCb][yCb] is retrieved through the following ordered steps:

- i. IntraPredModeY[xCb][yCb] is set to intra_luma_mpm_remainder[xCb][yCb].

- ii. For i equal to 0-5, inclusive, when IntraPredModeY[xCb][yCb] is greater than or equal to candModeList[i], the value of IntraPredModeY[xCb][yCb] is incremented by one.

The variable IntraPredModeY[x][y] with x=xCb...xCb+cbWidth-1 and y=yCb...yCb+cbHeight-1 is set to IntraPredModeY[xCb][yCb].

[355] Meanwhile, when intra prediction according to the intra prediction mode of the current block is expressed in a standard format, it may be as shown in the following table.

[356] Tab. 9

8.4.4.2.1 according to VVC specification

The discrete sample intra-prediction process according to predModeIntra is applied as follows:

- If predModeIntra is INTRA_PLANAR, the corresponding intra-prediction mode-based process specified in section 8.4.4.2.5 is activated with the transform block width nTbW and transform block height nTbH, the intra-prediction reference line index refIdx and the reference sample array p in as inputs, and the output is an array of predSamples of predicted samples.

- Otherwise, if predModeIntra is equal to INTRA_DC, the corresponding intra-prediction mode-based process specified in section 8.4.4.2.6 is activated with the transform block width nTbW, transform block height nTbH, the intra-prediction reference line index refIdx and the array p reference samples as inputs, and the output is an array of predSamples of predicted samples.

- Otherwise, if predModeIntra is equal to INTRA_LT_CCLM, INTRA_L_CCLM or INTRA_T_CCLM, the corresponding intra-prediction mode-based process specified in section 8.4.4.2.8 is activated with predModeIntra intra-prediction mode, sample location (xTbC, yTbC) set to (xTbCmp, yTbCmp), width nTbW and height nTbH of the transform block and an array of p reference samples as inputs, and the output is an array of predSamples of predicted samples.

- Otherwise, the corresponding intra-prediction mode-based process specified in section 8.4.4.2.7 is activated with predModeIntra intra-prediction mode, intra-prediction reference line index refIdx, transform block width nTbW, transform block height nTbH, width refW of the reference sample, height refH of the reference sample, width nCbW and height nCbH of the encoding block, color component index cIdx and array p of reference samples as inputs and a modified intra-prediction mode predModeIntra and array predSamples of predicted samples as outputs.

[357] In addition, an embodiment of intra-prediction based on the planar intra-prediction mode performed when MRL is applied in the present disclosure can be shown in the following table in a standard format.

[358] Tab. 10

INTRA_PLANAR intra-prediction mode specification

The inputs to this process are as follows:

- nTbW variable indicating the width of the conversion block,

- nTbH variable indicating the height of the transformation block,

- refIdx variable indicating the index of the intra-prediction reference line,

- adjacent discrete samples p[x][y], with x=-1-refIdx, y=-1-refIdx...nTbH and x=-refIdx...nTbW, y=-1-refIdx. The outputs of this process are the predicted discrete samples predSamples[x][y], with x=0...nTbW-1, y=0...nTbH-1.

The variables nW and nH are retrieved as follows:

- nW=Max(nTbW, 2) (8-116)

- nH=Max(nTbH, 2) (8-117)

The prediction sample values predSamples[x][y], with x=0...nTbW-1 and y=0...nTbH-1, are extracted as follows: predV[x][y]=((nH-1 -y)*p[x][-1-refIdx]+(y+1)*p[-1-refIdx][nTbH])<<Log2(nW) (8-118)

- predH[x][y]=((nW-1-x)*p[-1-refldx][y]+(x+1)*p[nTbW][-1-refldx])<<Log2 ( nH) (8-119)

- predSamples[x][y]=(predV[x][y]+predH[x][y]+nW*nH)>>(Log2(nW)+Log2(nH)+1) (8-120)

[359] In addition, an embodiment of intra-prediction based on the DC-intra-prediction mode performed when MRL is applied in the present disclosure can be shown in the following table in a standard format.

[360] Tab. eleven

DC-intra-prediction mode specification

The inputs to this process are as follows:

- nTbW variable indicating the width of the conversion block,

- nTbH variable indicating the height of the transformation block,

- refIdx variable indicating the index of the intra-prediction reference line,

- adjacent discrete samples p[x][y], with x=-1-refIdx, y=-1-refIdx...nTbH-1 and x=-refIdx...nTbW-1, y=-1-refIdx .

The outputs of this process are the predicted discrete samples predSamples[x][y], with x=0...nTbW-1, y=0...nTbH-1.

The prediction sample values predSamples[x][y], with x=0...nTbW-1, y=0...nTbH-1, are extracted through the following ordered steps:

1. The dcVal variable is retrieved as follows:

- When nTbW is equal to nTbH:

(8-121)

- When nTbW is greater than nTbH:

(8-122)

- When nTbW is less than nTbH:

(8-123)

1. Discrete prediction samples predSamples[x][y] are extracted as follows: predSamples[x][y]=dcVal, with x=0...nTbW-1, y=0...nTbH-1 (8-124 )

[361] In addition, the horizontal transformation kernel and the vertical transformation kernel extracted according to the intra-prediction mode may be as follows.

[362] Tab. 12

[363] For example, when the intra-prediction mode of the current block is determined to be the DC-intra-prediction mode, DCT2 may be used as a vertical transform kernel for transform/de-transform for the remainder of the current block, and DCT2 may be used as a horizontal transform kernel.

[364] Meanwhile, according to the present disclosure, the first permission element of the permission elements in the permission element string of the MPM index syntax element may be encoded based on contextual regular encoding, the remaining permission elements in the permission element string may be bypass encoded.

[365] In this case, the context index increment ctxInc to indicate the context model of the first permission element may be set differently based on at least one of the ISP flag value for the current block and/or the reference line index value for the current block in the following way.

[366] Tab. 13

[367] For example, referring to Table 13, when the reference line index value is not 0, ctxInc may be retrieved as 2, when the reference line index value is 0, if the ISP flag value is 1, ctxInc may be retrieved as 0, and if the ISP flag value is not 1, ctxInc may be retrieved as 1.

[368] Meanwhile, the present disclosure provides another embodiment for more efficiently performing intra-prediction performed based on the DC-intra-prediction mode when MRL is applied.

[369] FIG. 19 illustrates a reference sample used to extract a DC value when the intra-prediction type of the current block is MRL and the intra-prediction mode of the current block is a DC-intra-prediction mode.

[370](a) of FIG. 19 may represent a reference sample used to extract a DC value when the current block is a square block. For example, when the reference line indicated by the reference line index is reference line 0, reference line 1, reference line 2 or reference line 3, the DC value can be extracted based on the reference samples in the area (1900) shown in (a ) according to Fig. 19. Thus, when the X-axis component and the Y-axis component of the top left position of the current block are 0, the DC value can be retrieved based on the number of reference samples equal to the width from the reference sample with coordinates (-refIdx, -refIdx- 1) in the upper reference line of the current block, and the number of reference discrete samples equal to the width of the reference discrete sample with coordinates (-refIdx-1,-refIdx) in the left reference line of the current block. For example, when the reference line index value is 0, the DC value may be retrieved based on the number of reference samples equal to the width from the reference sample at coordinates (0,-1) in the upper reference line 0 of the current block, and the number of reference samples equal to the width from the reference sample with coordinates (-1, 0) in the left reference line 0 of the current block, when the reference line index value is 1, the DC value can be retrieved based on the number of reference samples equal to the width from the reference sample (- 1,-2) coordinates in the upper reference line 1 of the current block, and the number of reference discrete samples equal to the width from the reference discrete sample with coordinates (-2,-1) in the left reference line 1 of the current block, when the value of the reference line index is 2 , the DC value can be retrieved based on the number of reference samples equal to the width from the reference sample (-2,-3) coordinate in the upper reference line 2 of the current block, and the number of reference samples equal to the width from the reference sample with coordinates ( -3,-2) in the left reference line 2 of the current block, when the reference line index value is 3, the DC value can be retrieved based on the number of reference samples equal to the width from the reference sample at coordinates (-3,-4) in the upper reference line 3 of the current block, and the number of reference discrete samples equal to the width of the reference discrete sample with coordinates (-4,-3) in the left reference line 3 of the current block.

[371] Additionally, (b) of FIG. 19 may represent a reference sample used to extract a DC value when the current block is a non-square block. In the present embodiment, when the current block is a non-square block, the DC value can be extracted based on the reference samples in the reference line on the longer side from the width and height of the current block. For example, when the reference line indicated by the reference line index is reference line 0, reference line 1, reference line 2 or reference line 3, the DC value can be extracted based on the reference samples in the reference line area (1910) on the longer reference line side of the width and height of the current block. For example, when the width of the current block exceeds the height, the DC value may be retrieved based on the number of reference samples identical to the width from the reference sample at coordinates (-refIdx, -refIdx-1) at the top reference line of the current block. For example, when the reference line index value is 0, the DC value may be retrieved based on the number of reference samples equal to the width from the reference sample at coordinates (0,-1) in the top reference line 0 of the current block when the reference line index value is 1, the DC value can be retrieved based on the number of reference samples equal to the width from the reference sample (-1,-2) coordinate in the upper reference line 1 of the current block, when the reference line index value is 2, the DC value can be retrieved by based on the number of reference samples equal to the width from the reference sample (-2,-3) of the coordinate in the upper reference line 2 of the current block, when the reference line index value is 3, the DC value can be retrieved based on the number of reference samples equal to the width from the reference discrete sample with coordinates (-3,-4) in the upper reference line 3 of the current block.

[372] In addition, for example, when the width of the current block is less than the height, the DC value may be retrieved based on the number of reference samples identical to the height from the reference sample with coordinates (-refIdx-1, -refIdx) in the left reference line of the current block . For example, when the reference line index value is 0, the DC value may be retrieved based on the number of reference samples equal to the height from the reference sample at coordinates (-1, 0) in the left reference line 0 of the current block when the reference line index value is 1, the DC value can be retrieved based on the number of reference samples equal to the height from the reference sample with coordinates (-2,-1) in the left reference line 1 of the current block, when the reference line index value is 2, the DC value can be retrieved based on the number of reference samples equal to the height from the reference sample with coordinates (-3,-2) in the left reference line 2 of the current block, when the reference line index value is 3, the DC value can be extracted based on the number of reference samples, equal to the height from the reference discrete sample with coordinates (-4,-3) in the left reference line 3 of the current block.

[373] Thereafter, the prediction sample of the current block can be retrieved as a DC value.

[374] An embodiment of intra-prediction based on the DC-intra-prediction mode performed when MRL is applied in the present disclosure can be shown in the following table in a standard format.

[375] Tab. 14

INTRA_DC intra-prediction mode specification

The inputs to this process are as follows:

- nTbW variable indicating the width of the conversion block,

- nTbH variable indicating the height of the transformation block,

- refIdx variable indicating the index of the intra-prediction reference line,

- adjacent discrete samples p[x][y], with x=-1-refIdx, y=-1-refIdx...nTbH-1 and x=-refIdx...nTbW-1, y=-1-refIdx .

The outputs of this process are the predicted discrete samples predSamples[x][y], with x=0...nTbW-1, y=0...nTbH-1.

The prediction sample values predSamples[x][y], with x=0...nTbW-1, y=0...nTbH-1, are extracted through the following ordered steps:

1. The dcVal variable is retrieved as follows:

- When nTbW is equal to nTbH:

(8-121)

- When nTbW is greater than nTbH:

(8-122)

- When nTbW is less than nTbH:

(8-123)

1. The prediction samples predSamples[x][y] are extracted as follows:

- predSamples[x][y]=dcVal, with x=0...nTbW-1, y=0...nTbH-1 (8-124)

[376] Meanwhile, the present disclosure offers another embodiment of more efficient performance of intra-prediction performed based on the planar intra-prediction mode when MRL is applied.

[377] FIG. 20 illustrates a reference sample used when the intra-prediction type of the current block is MRL, and the intra-prediction mode of the current block is the planar intra-prediction mode.

[378] Referring to FIG. 20, when the reference line indicated by the reference line index is reference line 0, reference line 1, reference line 2 or reference line 3, planar prediction can be performed based on the reference samples in the reference line region (2000) shown in FIG. . 20. According to the present embodiment, planar prediction can be performed based on the sample width/height end+1-refIdx of the current block, regardless of the reference line index. That is, according to the present embodiment, when the X-axis component and the Y-axis component of the top left position of the current block are 0, the intra-prediction type of the current block is MRL, and the intra-prediction mode of the current block is the planar intra-prediction mode , planar prediction for the current block can be performed based on a reference sample with coordinates (W-refIdx, -refIdx-1) in the upper reference line and a reference sample with coordinates (-refIdx-1, H-refIdx) in the left reference line.

[379] Referring to the present embodiment, planar intra prediction may be performed using the reference samples of the reference line indicated by the reference line index, and specifically, planar intra prediction may be performed based on the left reference sample in the identical row (i.e. identical to the Y coordinate) with the position of the current discrete sample in the current block and the top reference discrete sample in an identical column (i.e. identical to the X coordinate) with the position of the current discrete sample, from the reference discrete samples of the reference line and the reference discrete sample with coordinates (W -refIdx,-refIdx-1) in the top reference line and a reference discrete sample with coordinates (-refIdx-1, H-refIdx) in the left reference line. In this case, the prediction sample value of the current sample can be retrieved by performing bidirectional linear interpolation based on the values of the above-described four reference samples. Here, bidirectional linear interpolation can be performed under the condition that the left lower reference sample is located at the bottom side of the current sample, and the right upper reference sample is located at the right side of the current sample.

[380] An embodiment of intra-prediction based on the planar intra-prediction mode performed when MRL is applied in the present disclosure can be shown in the following table in a standard format.

[381] Tab. 15

INTRA_PLANAR intra-prediction mode specification

The inputs to this process are as follows:

- nTbW variable indicating the width of the conversion block,

- nTbH variable indicating the height of the transformation block,

- refIdx variable indicating the index of the intra-prediction reference line,

- adjacent discrete samples p[x][y], with x=-1-refIdx, y=-1-refIdx...nTbH and x=-refIdx...nTbW, y=-1-refIdx. The outputs of this process are the predicted discrete samples predSamples[x][y], with x=0...nTbW-1, y=0...nTbH-1.

The variables nW and nH are retrieved as follows:

- nW=Max(nTbW, 2) (8-116)

- nH=Max(nTbH, 2) (8-117)

The prediction sample values predSamples[x][y], with x=0...nTbW-1 and y=0...nTbH-1, are extracted as follows: predV[x][y]=((nH-1 -y)*p[x][-1-refIdx]+(y+1)*p[-1-refIdx][nTbH-refIdx])<<Log2(nW) (8-118)

- predH[x][y]=((nW-1-x)*p[-1-refIdx][y]+(x+1)*p[nTbW-refIdx][-1-refIdx])<< Log2(nH) (8-119)

- predSamples[x][y]=(predV[x][y]+predH[x][y]+nW*nH)>>(Log2(nW)+Log2(nH)+1) (8-120)

[382] FIG. 21 schematically illustrates an image encoding method performed by the encoding apparatus according to the present disclosure. The method disclosed in FIG. 21 may be performed by the encoding device disclosed in FIG. 2. In particular, for example, S2100 of FIG. 21 may be performed by the encoding device prediction unit, and S2110 to S2120 may be performed by the entropy encoder of the encoding device. In addition, although not illustrated, the process of extracting a residual sample about the current block based on the original sample and the prediction sample about the current block may be performed by a subtractor of the encoding device, the process of generating residual information regarding the current block based on the residual sample may be performed by the residual processor of the encoding device, and the process of encoding image information including residual information can be performed by an entropy encoder of the encoding device.

[383] The encoder generates a reconstructed sample of the current block (S2100). The encoding apparatus may extract a prediction sample of the current block by performing prediction on the current block, extract a residual sample of the current block based on the prediction sample, and generate a reconstructed current block sample based on the prediction sample and the residual sample.

[384] For example, the encoder may determine the intra-prediction type for the current block from among the intra-prediction types described above. For example, the encoder may determine the type of intra-prediction for the current block taking into account a distortion cost function as a function of the bit rate (RD). The above-described types of intra-prediction may include a first type of intra-prediction using intra-prediction reference lines adjacent to the current block, a second type of intra-prediction using intra-prediction reference lines that are not adjacent to the current block, and a third the type of intra-prediction to which the intra-subsegment-based (ISP) mode applies. The first type of intra-prediction may indicate the general intra-prediction described above, the second type of intra-prediction may indicate the above-described MRL, and the third type of intra-prediction may indicate the above-described ISP.

[385] For example, the encoder may generate and encode a reference line index indicating the intra-prediction reference line of the current block. It may be determined whether or not the intra-prediction type for the current block is a second intra-prediction type based on the reference line index. If the intra-prediction type for the current block is not a second intra-prediction type, for example, the encoder may generate and encode an ISP flag representing whether or not the third intra-prediction type is applied to the current block. It may be determined whether or not the intra-prediction type for the current block is a third intra-prediction type based on the ISP flag. The intra-prediction type for the current block may be retrieved as a third intra-prediction type if the ISP flag indicates that the third intra-prediction type is applied to the current block, and the intra-prediction type for the current block may be retrieved as the first intra-prediction type. -prediction, if the ISP flag indicates that the third type of intra-prediction is not applied to the current block. The prediction-related information may include a reference line index, an ISP flag, and/or an ISP index. The prediction-related information may include a reference line index and may further include an ISP flag when the reference line index is 0. When the ISP flag is 1, the prediction-related information may further include an ISP index.

[386] For example, the encoder may construct a list of potentially candidate intra-prediction modes of the current block based on the intra-prediction modes of neighboring blocks relative to the current block.

[387] For example, the encoding device lists the potential candidate intra-prediction mode options of the current block through the process of constructing lists of the potential candidate intra-prediction mode options shown in Table 3. Meanwhile, the list of potential candidate intra-prediction mode options may mean the list described above most probable modes (MPM).

[388] For example, the encoder may construct a list of potential inter-prediction mode candidates based on the first potential intra-prediction mode candidate and the second potential intra-prediction mode candidate. The encoder may construct a list of potential inter-prediction mode candidates based on whether or not the first potential intra-prediction mode candidate is identical to the second potential intra-prediction mode candidate, and/or whether or not the mode number of the first candidate is greater than or equal to the first potential intra-prediction mode candidate. a suitable intra-prediction mode option and/or a mode number of a second potentially suitable intra-prediction mode option; a mode number for the DC-intra-prediction mode. Here, the first potential intra-prediction mode candidate may be retrieved based on the intra-prediction mode of the left neighboring block relative to the current block, and the second potential intra-prediction mode candidate may be retrieved based on the intra-prediction mode of the upper neighboring block relative to the current block. For example, the intra-prediction mode of a left neighbor block relative to the current block may be retrieved as a first potential candidate intra-prediction mode, and the intra-prediction mode of an upper neighbor block relative to the current block may be retrieved as a second potential candidate intra-prediction mode.

[389] In particular, when the first potential intra-prediction mode candidate is identical to the second potential intra-prediction mode candidate, for example, the encoder may determine whether or not the mode number of the first potential intra-prediction mode candidate is greater than the mode number for DC-intra-prediction mode, and if the mode number of the first potentially eligible intra-prediction mode option is greater than the mode number for the DC-intra-prediction mode, retrieve a list of potentially eligible intra-prediction mode options for the current block that includes the potentially eligible options intra-prediction modes as follows.

[390] - mpm[0]=leftIntraDir

[391] - mpm[1]=PLANAR_IDX

[392] - mpm[2]=DC_IDX

[393] - mpm[3]=((leftIntraDir+offset)%mod)+2

[394] - mpm[4]=((leftIntraDir-1)%mod)+2

[395] - mpm[5]=((leftIntraDir+offset-1)%mod)+2

[396] Here, mpm[0], mpm[1], mpm[2], mpm[3], mpm[4] and mpm[5] represent potential intra-prediction mode candidate 0, potential intra-prediction mode candidate 1 -predictions, potential intra-prediction mode candidate 2, potential intra-prediction mode candidate 3, potential intra-prediction mode candidate 4 and potential intra-prediction mode candidate 5, leftIntraDir represents the first potential intra-prediction mode candidate, PLANAR_IDX represents the planar intra-prediction mode, and DC_IDX represents the DC-intra-prediction mode. Thus, potential intra-prediction mode candidate 0 from the list of potential intra-prediction mode candidates may be retrieved as the first potential intra-prediction mode candidate, potential intra-prediction mode candidate 1 from the list of potential intra-prediction mode candidates may be retrieved as a planar intra-prediction mode, potential intra-prediction mode candidate 2 from the list of potential intra-prediction mode candidates may be retrieved as a DC-intra-prediction mode, potential intra-prediction mode candidate 3 from the list of potentially suitable intra-prediction modes options for intra-prediction modes can be retrieved as an intra-prediction mode having a mode number (leftIntraDir+offset)%mod),+2, i.e. an intra-prediction mode having a value obtained by performing a modulo arithmetic operation on the sum of the mode number of the first potentially suitable intra-prediction mode option and offset and summing 2 with the result of the modulo arithmetic operation as the mode number, a potentially suitable intra-prediction mode option 4 -predictions from the list of potentially suitable intra-prediction mode options can be retrieved as an intra-prediction mode having a mode number ((leftIntraDir-1)%mod)+2, i.e. an intra-prediction mode having a value obtained by performing modulo arithmetic on a value obtained by subtracting 1 from the mode number of the first potentially suitable intra-prediction mode option and adding 2 with the result of the modulo arithmetic as the mode number, and potentially a suitable intra-prediction mode option 5 from the list of potentially suitable intra-prediction mode options can be retrieved as an intra-prediction mode having a mode number ((leftIntraDir+offset-1)%mod)+2, i.e. an intra-prediction mode having a value obtained by performing a modulo arithmetic operation on the sum of the mode number of the first potentially suitable intra-prediction mode option and (offset-1) and summing 2 with the result of the modulo arithmetic operation as the mode number.

[397] For example, when the first potential intra-prediction mode candidate is not identical to the second potential intra-prediction mode candidate, the encoder may retrieve potential intra-prediction mode candidate 0 and potential intra-prediction mode candidate 1 as follows.

[398] - mpm[0]=leftIntraDir

[399] - mpm[1]=aboveIntraDir

[400] Thus, potential intra-prediction mode candidate 0 from the list of potential intra-prediction mode candidates may be retrieved as the first potential intra-prediction mode candidate, and potential intra-prediction mode candidate 1 from the list of potential candidates. intra-prediction modes may be retrieved as a second potentially suitable intra-prediction mode option. Additionally, maxCandModeIdx may be retrieved as 0 if the mode number of potential intra-prediction mode candidate 0 is greater than the mode number of intra-prediction mode candidate 1, and maxCandModeIdx may be retrieved as 1 if the mode number of potential intra-prediction mode candidate 0 prediction does not exceed the mode number of potentially suitable intra-prediction mode option 1.

[401] If the mode number of the first potentially suitable intra-prediction mode candidate and the mode number of the second potentially suitable intra-prediction mode candidate exceed the mode number for the DC-intra-prediction mode, the encoder may retrieve the potential intra-prediction mode candidate 2 and potentially suitable option 3 of intra-prediction mode as follows.

[402] - mpm[2]=PLANAR_IDX

[403] - mpm[3]=DC_IDX

[404] Thus, potential intra-prediction mode candidate 2 from the list of potential intra-prediction mode candidates may be retrieved as a planar intra-prediction mode, and potential intra-prediction mode candidate 3 from the list of potential intra-prediction mode candidates. predictions can be retrieved as DC-intra-prediction mode.

[405] Then, if the value obtained by subtracting the mode number mpm[!maxCandModeIdx] from the mode number mpm[maxCandModeIdx] is less than 63 and greater than 1, the encoder/decoder may extract the potential intra-prediction mode candidate 4 and the potential candidate 5 intra-prediction mode as follows.

[406] - mpm[4]=((mpm[maxCandModeIdx]+offset)%mod)+2

[407] - mpm[5]=((mpm[maxCandModeIdx]-1)%mod)+2

[408] Thus, potential intra-prediction mode candidate 4 from the list of potential intra-prediction mode candidates may be retrieved as an intra-prediction mode having mode number ((mpm[maxCandModeIdx]+offset)%mod)+2. those. an intra-prediction mode having a value obtained by performing modulo arithmetic on the sum of mpm[maxCandModeIdx] and offset and summing 2 with the result of the modulo arithmetic as the mode number, and potentially a suitable intra-prediction mode option 5 from the list of potentially suitable intra-prediction mode options can be retrieved as an intra-prediction mode having a mode number ((mpm[maxCandModeIdx]-1)%mod)+2, i.e. an intra-prediction mode having a value obtained by performing modulo arithmetic on a value obtained by subtracting 1 from mpm[maxCandModeIdx] and adding 2 to the result of modulo arithmetic as the mode number.

[409] If the value obtained by subtracting the mode number mpm[!maxCandModeIdx] from the mode number mpm[maxCandModeIdx] is equal to or greater than 63 or equal to or less than 1, the encoder/decoder may retrieve a potentially suitable intra-prediction mode option 4 and Potentially suitable option 5 of intra-prediction mode is as follows.

[410] - mpm[4]=((mpm[maxCandModeIdx]+offset-1)%mod)+2

[411] - mpm[5]=((mpm[maxCandModeIdx])%mod)+2

[412] Thus, a potential candidate intra-prediction mode option 4 from a list of potential candidate intra-prediction mode candidates may be retrieved as an intra-prediction mode having a mode number ((mpm[maxCandModeIdx]+offset-1)%mod)+ 2, i.e. an intra-prediction mode having a value obtained by performing modulo arithmetic on the sum of mpm[maxCandModeIdx] and (offset-1) and summing 2 with the result of the modulo arithmetic as the mode number, and a potentially suitable intra-prediction mode option 5 prediction from the list of potentially suitable intra-prediction mode options can be retrieved as an intra-prediction mode having a mode number ((mpm[maxCandModeIdx]%mod)+2, i.e., an intra-prediction mode having a value obtained by performing arithmetic modulo operations for mpm[maxCandModeIdx] and summing 2 with the result of the arithmetic modulo operation as the mode number.

[413] If at least one of the mode number of the first potentially suitable intra-prediction mode option and the mode number of the second potentially suitable intra-prediction mode option is not greater than the mode number for the DC-intra-prediction mode, the encoder may determine whether is equal to or greater than or not the sum of the mode number of the first potentially suitable intra-prediction mode option and the mode number of the second potentially suitable intra-prediction mode option 2. If the sum of the mode number of the first potentially suitable intra-prediction mode option and the mode number of the second potentially suitable intra-prediction mode option -prediction is equal to or greater than 2, the encoder may retrieve potential candidate intra-prediction mode candidate 2 - potential candidate intra-prediction mode candidate 5 as follows.

[414] - mpm[2]=(mpm[!maxCandModeIdx]==PLANAR_IDX)? DC_IDX: PLANAR_IDX

[415] - mpm[3]=((mpm[maxCandModeIdx]+offset)%mod)+2

[416] - mpm[4]=((mpm[maxCandModeIdx]-1)%mod)+2

[417] - mpm[5]=((mpm[maxCandModeIdx]+offset-1)%mod)+2

[418] Thus, potential intra-prediction mode candidate 2 from the list of potential intra-prediction mode candidates may be retrieved as a DC intra-prediction mode if mpm[!maxCandModeIdx] is a planar intra-prediction mode, and may be retrieved as the planar intra-prediction mode if mpm[!maxCandModeIdx] is not a planar intra-prediction mode. In addition, the potential intra-prediction mode candidate 3 from the list of potential intra-prediction mode candidates may be retrieved as an intra-prediction mode having a mode number ((mpm[maxCandModeIdx]+offset)%mod)+2, i.e. . intra-prediction mode having the value obtained by performing modulo arithmetic on the sum of mpm[maxCandModeIdx] and offset and summing 2 with the result of modulo arithmetic as the mode number, potentially suitable intra-prediction mode option 4 from the list of potentially suitable intra-prediction mode options can be retrieved as an intra-prediction mode having a mode number ((mpm[maxCandModeIdx]-1)%mod)+2, i.e. an intra-prediction mode having a value obtained by performing modulo arithmetic on a value obtained by subtracting 1 from mpm[maxCandModeIdx] and summing 2 with the result of modulo arithmetic as the mode number, and potentially a suitable intra-prediction mode option 5 prediction from the list of potentially suitable intra-prediction mode options can be retrieved as an intra-prediction mode having a mode number ((mpm[maxCandModeIdx]+offset-1)%mod)+2, i.e. an intra-prediction mode having a value obtained by performing modulo arithmetic on the sum of mpm[maxCandModeIdx] and (offset-1) and summing 2 with the result of modulo arithmetic as the mode number.

[419] If the above conditions are not satisfied, the encoder may extract potential intra-prediction mode candidate 0 - potential intra-prediction mode candidate 5 as follows.

[420] - mpm[0]=leftIntraDir

[421] - mpm[1]=(mpm[0]==PLANAR_IDX)? DC_IDX: PLANAR_IDX

[422] - mpm[2]=VER_IDX

[423] - mpm[3]=HOR_IDX

[424] - mpm[4]=VER_IDX-4

[425] - mpm[5]=VER_IDX+4

[426] Thus, potential intra-prediction mode candidate 0 from the list of potential intra-prediction mode candidates may be retrieved as the first potential intra-prediction mode candidate, intra-prediction mode candidate 1 from the list of potential intra-prediction mode candidates. intra-prediction mode may be retrieved as a DC-intra-prediction mode if the potential intra-prediction mode candidate 0 is a planar intra-prediction mode, and retrieved as a planar intra-prediction mode if the potential intra-prediction mode candidate 0 is an intra-prediction mode does not represent a planar intra-prediction mode, potentially suitable intra-prediction mode option 2 from the list of potentially suitable intra-prediction mode options can be retrieved as a vertical intra-prediction mode, potentially suitable intra-prediction mode option 3 from the list of potentially suitable intra-prediction mode options intra-prediction mode may be retrieved as a horizontal intra-prediction mode, potential intra-prediction mode candidate 4 from the list of potential intra-prediction mode candidates may be retrieved as an intra-prediction mode corresponding to the mode number obtained by subtracting 4 from the mode number for the vertical intra-prediction mode, i.e. intra-prediction mode #46 and potential intra-prediction mode candidate 5 from the list of potential intra-prediction mode candidates may be retrieved as the intra-prediction mode corresponding to the mode number obtained by summing 4 with the mode number for the vertical intra-prediction mode , i.e. mode #54 intra-prediction.

[427] For example, the encoder may perform the list-building process of potential intra-prediction mode candidates shown in Table 4 to construct a list of potential intra-prediction mode candidates for the current block.

[428] For example, the encoder may construct a list of potential intra-prediction mode candidates based on the first potential intra-prediction mode candidate and the second potential intra-prediction mode candidate. The encoder may construct a list of potential inter-prediction mode candidates based on whether or not the first potential intra-prediction mode candidate is identical to the second potential intra-prediction mode candidate, and/or whether or not the mode number of the first candidate is greater than or equal to the first potential intra-prediction mode candidate. a suitable intra-prediction mode option and/or a mode number of a second potentially suitable intra-prediction mode option; a mode number for the DC-intra-prediction mode. Here, the first potential intra-prediction mode candidate may be retrieved based on the intra-prediction mode of the left neighboring block relative to the current block, and the second potential intra-prediction mode candidate may be retrieved based on the intra-prediction mode of the upper neighboring block relative to the current block. For example, the intra-prediction mode of a left neighbor block relative to the current block may be retrieved as a first potential candidate intra-prediction mode, and the intra-prediction mode of an upper neighbor block relative to the current block may be retrieved as a second potential candidate intra-prediction mode.

[429] In particular, when the first potential intra-prediction mode candidate is identical to the second potential intra-prediction mode candidate, for example, the encoder may determine whether or not the mode number of the first potential intra-prediction mode candidate is greater than the mode number for DC-intra-prediction mode, and if the mode number of the first potentially eligible intra-prediction mode option is greater than the mode number for the DC-intra-prediction mode, retrieve a list of potentially eligible intra-prediction mode options for the current block that includes the potentially eligible options intra-prediction modes as follows.

[430] - mpm[0]=leftIntraDir

[431] - mpm[1]=PLANAR_IDX

[432] - mpm[2]=((leftIntraDir+offset)%mod)+2

[433] - mpm[3]=((leftIntraDir-1)%mod)+2

[434] - mpm[4]=DC_IDX

[435] - mpm[5]=((leftIntraDir+offset-1)%mod)+2

[436] Here, mpm[0], mpm[1], mpm[2], mpm[3], mpm[4] and mpm[5] represent potential intra-prediction mode candidate 0, potential intra-prediction mode candidate 1 -predictions, potential intra-prediction mode candidate 2, potential intra-prediction mode candidate 3, potential intra-prediction mode candidate 4 and potential intra-prediction mode candidate 5, leftIntraDir represents the first potential intra-prediction mode candidate, PLANAR_IDX represents the planar intra-prediction mode, and DC_IDX represents the DC-intra-prediction mode. Thus, potential intra-prediction mode candidate 0 from the list of potential intra-prediction mode candidates may be retrieved as the first potential intra-prediction mode candidate, potential intra-prediction mode candidate 1 from the list of potential intra-prediction mode candidates may be retrieved as a planar intra-prediction mode, potential intra-prediction mode candidate 2 from the list of potential intra-prediction mode candidates may be retrieved as an intra-prediction mode having mode number ((leftIntraDir+offset)%mod)+2 , i.e. an intra-prediction mode having a value obtained by performing a modulo arithmetic operation on the sum of the mode number of the first potentially suitable intra-prediction mode option and offset and summing 2 with the result of the modulo arithmetic operation as the mode number, a potentially suitable intra-prediction mode option 3 -predictions from the list of potentially suitable intra-prediction mode options can be retrieved as an intra-prediction mode having a mode number ((leftIntraDir-1)%mod)+2, i.e. an intra-prediction mode having a value obtained by performing a modulo arithmetic operation on a value obtained by subtracting 1 from the mode number of the first potentially suitable intra-prediction mode option and summing 2 with the result of the modulo arithmetic operation as the mode number potentially suitable intra-prediction mode option 4 from the list of potentially suitable intra-prediction mode options may be retrieved as a DC-intra-prediction mode, and potential intra-prediction mode option 5 from the list of potentially suitable intra-prediction mode options may be retrieved as the intra-prediction mode -prediction with mode number ((leftIntraDir+offset-1)%mod)+2, i.e. an intra-prediction mode having a value obtained by performing a modulo arithmetic operation on the sum of the mode number of the first potentially suitable intra-prediction mode option and (offset-1) and summing 2 with the result of the modulo arithmetic operation as the mode number.

[437] For example, when the first potential intra-prediction mode candidate is not identical to the second potential intra-prediction mode candidate, the encoder may retrieve potential intra-prediction mode candidate 0 and potential intra-prediction mode candidate 1 as follows.

[438] - mpm[0]=leftIntraDir

[439] - mpm[1]=aboveIntraDir

[440] Thus, potential intra-prediction mode candidate 0 from the list of potential intra-prediction mode candidates may be retrieved as the first potential intra-prediction mode candidate, and potential intra-prediction mode candidate 1 from the list of potential candidates. intra-prediction modes may be retrieved as a second potentially suitable intra-prediction mode option. Additionally, the encoder may extract maxCandModeIdx as 0 if the mode number of intra-prediction mode candidate 0 is greater than the mode number of intra-prediction mode candidate 1, and extract maxCandModeIdx as 1 if the mode number of intra-prediction mode candidate 0 is greater than the mode number of intra-prediction mode candidate 1. -prediction does not exceed the mode number of potentially suitable option 1 intra-prediction mode.

[441] If the mode number of the first potentially suitable intra-prediction mode candidate and the mode number of the second potentially suitable intra-prediction mode candidate exceed the mode number for the DC-intra-prediction mode, the encoder may retrieve potential intra-prediction mode candidate 1 - potentially suitable option 3 of intra-prediction mode as follows.

[442] - mpm[1]=PLANAR_IDX

[443] - mpm[2]=aboveIntraDir

[444] - maxCandModeIdx=mpm[0]>mpm[2]? 0:2

[445] - interval minCandModeidx=mpm[0]>mpm[2]? 20

[446] - mpm[3]=DC_IDX;

[447] Thus, potential candidate intra-prediction mode option 1 from the list of potential candidates for intra-prediction modes can be retrieved as a planar intra-prediction mode, potential candidate intra-prediction mode option 2 from the list of potential candidates for intra-prediction modes may be retrieved as a second potential intra-prediction mode candidate, and intra-prediction mode candidate 3 from the list of potential intra-prediction mode candidates may be retrieved as a DC intra-prediction mode. Additionally, the encoder may extract maxCandModeIdx as 0 if the mode number of intra-prediction mode candidate 0 is greater than the mode number of intra-prediction mode candidate 2, and extract maxCandModeIdx as 2 if the mode number of intra-prediction mode candidate 0 is greater than the mode number of intra-prediction mode candidate 2. -prediction does not exceed the mode number of the potentially suitable option 2 of the intra-prediction mode. Additionally, the encoder may extract minCandModeidx as 2 if the mode number of intra-prediction mode candidate 0 is greater than the mode number of intra-prediction mode candidate 2, and extract minCandModeidx as 0 if the mode number of intra-prediction mode candidate 0 is greater than the mode number of intra-prediction mode candidate 2. -prediction does not exceed the mode number of the potentially suitable option 2 of the intra-prediction mode.

[448] If the value obtained by subtracting the mode number mpm[minCandModeidx] from the mode number mpm[maxCandModeIdx] is less than 63 and greater than 1, the encoder/decoder may retrieve a potential intra-prediction mode candidate 4 and a potential intra-prediction mode candidate 5 intra-predictions as follows.

[449] - mpm[4]=((mpm[maxCandModeIdx]+offset)%mod)+2

[450] - mpm[5]=((mpm[maxCandModeIdx]-1)%mod)+2

[451] Thus, a potential candidate intra-prediction mode option 4 from the list of potential candidate intra-prediction mode candidates may be retrieved as an intra-prediction mode having a mode number ((mpm[maxCandModeIdx]+offset)%mod)+2. those. an intra-prediction mode having a value obtained by performing modulo arithmetic on the sum of mpm[maxCandModeIdx] and offset and summing 2 with the result of the modulo arithmetic as the mode number, and potentially a suitable intra-prediction mode option 5 from the list of potentially suitable intra-prediction mode options can be retrieved as an intra-prediction mode having a mode number ((mpm[maxCandModeIdx]-1)%mod)+2, i.e. an intra-prediction mode having a value obtained by performing modulo arithmetic on a value obtained by subtracting 1 from mpm[maxCandModeIdx] and adding 2 to the result of modulo arithmetic as the mode number.

[452] If the value obtained by subtracting the mode number mpm[minCandModeidx] from the mode number mpm[maxCandModeIdx] is equal to or greater than 63 or equal to or less than 1, the encoder/decoder may retrieve a potentially suitable intra-prediction mode option 4 and potentially suitable option 5 of intra-prediction mode as follows.

[453] - mpm[4]=((mpm[maxCandModeIdx]+offset-1)%mod)+2

[454] - mpm[5]=((mpm[maxCandModeIdx])%mod)+2

[455] Thus, potential intra-prediction mode candidate 4 from the list of potential intra-prediction mode candidates may be retrieved as an intra-prediction mode having mode number ((mpm[maxCandModeIdx]+offset-1)%mod)+ 2, i.e. an intra-prediction mode having a value obtained by performing modulo arithmetic on the sum of mpm[maxCandModeIdx] and (offset-1) and summing 2 with the result of the modulo arithmetic as the mode number, and a potentially suitable intra-prediction mode option 5 prediction from the list of potentially suitable intra-prediction mode options can be retrieved as an intra-prediction mode having mode number ((mpm[maxCandModeIdx])%mod)+2, i.e. an intra-prediction mode having a value obtained by performing modulo arithmetic on mpm[maxCandModeIdx] and summing 2 with the result of modulo arithmetic as the mode number.

[456] If at least one of the mode number of the first potentially suitable intra-prediction mode option and the mode number of the second potentially suitable intra-prediction mode option is not greater than the mode number for the DC-intra-prediction mode, the encoder may determine whether is equal to or greater than or not the sum of the mode number of the first potentially suitable intra-prediction mode option and the mode number of the second potentially suitable intra-prediction mode option 2. If the sum of the mode number of the first potentially suitable intra-prediction mode option and the mode number of the second potentially suitable intra-prediction mode option -prediction is equal to or greater than 2, the encoder can determine whether or not at least one of the first potentially suitable intra-prediction mode option and the second potentially suitable intra-prediction mode option is a planar intra-prediction mode.

[457] If at least one of the first potential intra-prediction mode candidate and the second potential intra-prediction mode candidate is a planar intra-prediction mode, the encoder may retrieve intra-prediction mode candidate 0 and potentially suitable option 1 of intra-prediction mode as follows.

[458] - mpm[0]=PLANAR_IDX

[459] - mpm[1]=(leftIntraDir<aboveIntraDir)? aboveIntraDir:leftIntraDir

[460] - maxCandModeIdx=1

[461] Thus, potential intra-prediction mode candidate 0 from the list of potential intra-prediction mode candidates may be retrieved as a planar intra-prediction mode, potential intra-prediction mode candidate 1 from the list of potential intra-prediction mode candidates may be retrieved as the second potential intra-prediction mode candidate if the mode number of the first intra-prediction mode candidate is less than the mode number of the second intra-prediction mode candidate, and retrieved as the first intra-prediction mode candidate if the mode number of the first potentially suitable intra-prediction mode option is equal to or greater than the mode number of the second potentially suitable intra-prediction mode option. Additionally, the encoder may retrieve maxCandModeIdx as 1.

[462] If the first potential intra-prediction mode candidate and the second potential intra-prediction mode candidate are not planar intra-prediction mode, the encoder may retrieve potential intra-prediction mode candidate 2 - potential intra-prediction mode candidate 5 predictions as follows.

[463] - mpm[2]=(mpm[!maxCandModeIdx]==PLANAR_IDX)? DC_IDX: PLANAR_IDX

[464] - mpm[3]=((mpm[maxCandModeIdx]+offset)%mod)+2

[465] - mpm[4]=((mpm[maxCandModeIdx]-1)%mod)+2

[466] - mpm[5]=((mpm[maxCandModeIdx]+offset-1)%mod)+2

[467] Thus, potential intra-prediction mode candidate 2 from the list of potential intra-prediction mode candidates may be retrieved as a DC intra-prediction mode if mpm[!maxCandModeIdx] is a planar intra-prediction mode, and may be retrieved as the planar intra-prediction mode if mpm[!maxCandModeIdx] is not a planar intra-prediction mode. In addition, the potential intra-prediction mode candidate 3 from the list of potential intra-prediction mode candidates may be retrieved as an intra-prediction mode having a mode number ((mpm[maxCandModeIdx]+offset)%mod)+2, i.e. . intra-prediction mode having the value obtained by performing modulo arithmetic on the sum of mpm[maxCandModeIdx] and offset and summing 2 with the result of modulo arithmetic as the mode number, potentially suitable intra-prediction mode option 4 from the list of potentially suitable intra-prediction mode options can be retrieved as an intra-prediction mode having a mode number ((mpm[maxCandModeIdx]-1)%mod)+2, i.e. an intra-prediction mode having a value obtained by performing modulo arithmetic on a value obtained by subtracting 1 from mpm[maxCandModeIdx] and summing 2 with the result of modulo arithmetic as the mode number, and potentially a suitable intra-prediction mode option 5 prediction from the list of potentially suitable intra-prediction mode options can be retrieved as an intra-prediction mode having a mode number ((mpm[maxCandModeIdx]+offset-1)%mod)+2, i.e. an intra-prediction mode having a value obtained by performing modulo arithmetic on the sum of mpm[maxCandModeIdx] and (offset-1) and summing 2 with the result of modulo arithmetic as the mode number.

[468] If the above conditions are not satisfied, the encoder may extract potential intra-prediction mode candidate 0 - potential intra-prediction mode candidate 5 as follows.

[469] - mpm[0]=leftIntraDir

[470] - mpm[1]=(mpm[0]==PLANAR_IDX)? DC_IDX: PLANAR_IDX

[471] - mpm[2]=VER_IDX

[472] - mpm[3]=HOR_IDX

[473] - mpm[4]=VER_IDX-4

[474] - mpm[5]=VER_IDX+4

[475] Thus, potential intra-prediction mode candidate 0 from the list of potential intra-prediction mode candidates may be retrieved as the first potential intra-prediction mode candidate, intra-prediction mode candidate 1 from the list of potential intra-prediction mode candidates. intra-prediction mode may be retrieved as a DC-intra-prediction mode if the potential intra-prediction mode candidate 0 is a planar intra-prediction mode, and retrieved as a planar intra-prediction mode if the potential intra-prediction mode candidate 0 is an intra-prediction mode does not represent a planar intra-prediction mode, potentially suitable intra-prediction mode option 2 from the list of potentially suitable intra-prediction mode options can be retrieved as a vertical intra-prediction mode, potentially suitable intra-prediction mode option 3 from the list of potentially suitable intra-prediction mode options intra-prediction mode may be retrieved as a horizontal intra-prediction mode, potential intra-prediction mode candidate 4 from the list of potential intra-prediction mode candidates may be retrieved as an intra-prediction mode corresponding to the mode number obtained by subtracting 4 from the mode number for the vertical intra-prediction mode, i.e. intra-prediction mode #46 and potential intra-prediction mode candidate 5 from the list of potential intra-prediction mode candidates may be retrieved as the intra-prediction mode corresponding to the mode number obtained by summing 4 with the mode number for the vertical intra-prediction mode , i.e. mode #54 intra-prediction.

[476] For example, the encoder may perform the list-building process of potential intra-prediction mode candidates shown in Table 5 to construct a list of potential intra-prediction mode candidates for the current block.

[477] For example, the encoder may construct a list of potential intra-prediction mode candidates based on the first potential intra-prediction mode candidate and the second potential intra-prediction mode candidate. The encoder may construct a list of potential inter-prediction mode candidates based on whether or not the first potential intra-prediction mode candidate is identical to the second potential intra-prediction mode candidate, and/or whether or not the mode number of the first candidate is greater than or equal to the first potential intra-prediction mode candidate. a suitable intra-prediction mode option and/or a mode number of a second potentially suitable intra-prediction mode option; a mode number for the DC-intra-prediction mode. Here, the first potential intra-prediction mode candidate may be retrieved based on the intra-prediction mode of the left neighboring block relative to the current block, and the second potential intra-prediction mode candidate may be retrieved based on the intra-prediction mode of the upper neighboring block relative to the current block. For example, the intra-prediction mode of a left neighbor block relative to the current block may be retrieved as a first potential candidate intra-prediction mode, and the intra-prediction mode of an upper neighbor block relative to the current block may be retrieved as a second potential candidate intra-prediction mode.

[478] In particular, when the first potential intra-prediction mode candidate is identical to the second potential intra-prediction mode candidate, for example, the encoder may determine whether or not the mode number of the first potential intra-prediction mode candidate is greater than the mode number for DC-intra-prediction mode, and if the mode number of the first potentially eligible intra-prediction mode option is greater than the mode number for the DC-intra-prediction mode, retrieve a list of potentially eligible intra-prediction mode options for the current block that includes the potentially eligible options intra-prediction modes as follows.

[479] - mpm[0]=g_intraMode65to33AngMapping[leftIntraDir]

[480] - mpm[1]=((g_intraMode65to33AngMapping[leftIntraDir]+offset)%mod)+2

[481] - mpm[2]=((g_intraMode65to33AngMapping[leftIntraDir]-1)%mod)+2

[482] Thus, potential intra-prediction mode candidate 0 from the list of potential intra-prediction mode candidates may be retrieved as the first potential intra-prediction mode candidate. In addition, potentially suitable intra-prediction mode option 1 from the list of potentially suitable intra-prediction mode options can be retrieved as an intra-prediction mode having mode number ((g_intraMode65to33AngMapping[leftIntraDir]+offset)%mod)+2, i.e. . an intra-prediction mode having a value obtained by performing a modulo arithmetic operation on the sum of the mode number of the first potentially suitable intra-prediction mode option and offset and summing 2 with the result of the modulo arithmetic operation as the mode number, and the potentially suitable mode option 2 intra-prediction from the list of potentially suitable intra-prediction mode options can be retrieved as an intra-prediction mode having a mode number ((g_intraMode65to33AngMapping[leftIntraDir]-1)%mod)+2, i.e. an intra-prediction mode having a value obtained by performing a modulo arithmetic operation on a value obtained by subtracting 1 from the mode number of the first potentially suitable intra-prediction mode option and adding 2 with the result of the modulo arithmetic operation as the mode number.

[483] If the mode number of the first potentially eligible intra-prediction mode candidate is not greater than the mode number for the DC-intra-prediction mode, the encoder may retrieve a list of potentially eligible intra-prediction mode candidates for the current block that includes the potential candidate mode options intra-predictions as follows.

[484] - mpm[0]=g_intraMode65to33AngMapping[PLANAR_IDX]

[485] - mpm[1]=g_intraMode65to33AngMapping[DC_IDX]

[486] - mpm[2]=g_intraMode65to33AngMapping[VER_IDX]

[487] Thus, potential intra-prediction mode candidate 0 from the list of potential intra-prediction mode candidates may be retrieved as a planar intra-prediction mode, potential intra-prediction mode candidate 1 from the list of potential intra-prediction mode candidates may be retrieved as a DC intra-prediction mode, and a potential intra-prediction mode candidate 2 from the list of potential intra-prediction mode candidates may be retrieved as a vertical intra-prediction mode.

[488] Additionally, if the first potential intra-prediction mode candidate is not identical to the second potential intra-prediction mode candidate, the encoder may retrieve potential intra-prediction mode candidate 0 and potential intra-prediction mode candidate 1.

[489] - mpm[0]=g_intraMode65to33AngMapping[leftIntraDir]

[490] - mpm[1]=g_intraMode65to33AngMapping[aboveIntraDir]

[491] Thus, potential intra-prediction mode candidate 0 from the list of potential intra-prediction mode candidates may be retrieved as the first potential intra-prediction mode candidate, and potential intra-prediction mode candidate 1 from the list of potential candidates. intra-prediction modes may be retrieved as a second potentially suitable intra-prediction mode option.

[492] Then, if both the first potential intra-prediction mode candidate and the second potential intra-prediction mode candidate are planar intra-prediction mode, the encoder may retrieve the intra-prediction mode candidate 2 as follows.

[493] - mpm[2]=g_intraMode65to33AngMapping[PLANAR_IDX]

[494] Thus, potential intra-prediction mode candidate 2 from the list of potential intra-prediction mode candidates may be retrieved as a planar intra-prediction mode.

[495] Alternatively, if at least one of the first potential intra-prediction mode candidate and the second potential intra-prediction mode candidate is a planar intra-prediction mode, the encoder may retrieve intra-prediction candidate 2. -predictions as follows.

[496] - mpm[2]=g_intraMode65to33AngMapping [(leftIntraDir+aboveIntraDir)<2? VER_IDX:DC_IDX]

[497] Thus, potential intra-prediction mode candidate 2 from the list of potentially suitable intra-prediction mode candidates may be retrieved as a vertical intra-prediction mode if the sum of the mode number of the first potentially suitable intra-prediction mode candidate and the mode number of the second potentially suitable intra-prediction mode candidate is less than 2, and retrieved as a DC-intra-prediction mode if the sum of the mode number of the first potentially suitable intra-prediction mode candidate and the mode number of the second potentially suitable intra-prediction mode candidate is equal to or greater than 2.

[498] For example, the encoding device may construct a list of potential intra-prediction mode candidates of the current block based on the intra-prediction modes of neighboring blocks relative to the current block, as shown in Table 6. Meanwhile, the list of potential intra-prediction mode candidates may mean the above list of most probable modes (MPM).

[499] For example, the encoder may construct a list of potentially suitable intra-prediction mode candidates based on the intra-prediction mode of the left neighbor block relative to the current block and the intra-prediction mode of the top neighbor block relative to the current block. The encoding device can determine whether or not the intra-prediction mode of the left adjacent block and the intra-prediction mode of the upper adjacent block are identical with respect to the current block, and whether or not the mode number for the intra-prediction mode of the left adjacent block is greater than the mode number for the DC mode. -intra-predictions. The encoder may construct a list of potentially suitable intra-prediction mode candidates based on whether or not the intra-prediction mode of a left adjacent block and the intra-prediction mode of an upper adjacent block relative to the current block are identical, and/or the mode number for the intra-prediction mode the left adjacent block exceeds the mode number for the DC-intra-prediction mode.

[500] When the intra-prediction mode of the left adjacent block and the intra-prediction mode of the upper adjacent block with respect to the current block are identical, and the mode number for the intra-prediction mode of the left adjacent block is greater than the mode number for the DC-intra-prediction mode, the encoding device may retrieve a list of potential candidate intra-prediction mode options for the current block, including potential candidate intra-prediction mode options, as described below.

[501] - mpm[0]=INTRA_PLANAR

[502] - mpm[1]=candIntraPredModeA

[503] 2+((candIntraPredModeA+61)%64)

[504] - mpm[3]=2+((candIntraPredModeA-1)%64)

[505] - mpm[4]=INTRA_DC

[506] - mpm[5]=2+((candIntraPredModeA+60)%64)

[507] Thus, potential intra-prediction mode candidate 0 from the list of potential intra-prediction mode candidates may be retrieved as a planar intra-prediction mode, potential intra-prediction mode candidate 1 from the list of potential intra-prediction mode candidates can be retrieved as the intra-prediction mode of the left adjacent block, a potential candidate intra-prediction mode option 2 from the list of potential candidates for intra-prediction modes can be retrieved as an intra-prediction mode having mode number 2+((candIntraPredModeA+61)% 64), i.e. an intra-prediction mode having a value obtained by performing a modulo 64 arithmetic operation on a value obtained by adding 61 to the mode number for the intra-prediction mode of the left adjacent block and adding 2 to the modulo arithmetic operation result as the mode number, Potentially suitable intra-prediction mode option 3 from the list of potentially suitable intra-prediction mode options may be retrieved as an intra-prediction mode having mode number 2+((candIntraPredModeA-1)%64), i.e. an intra-prediction mode having a value obtained by performing a modulo 64 arithmetic operation on a value obtained by subtracting 1 from the mode number for the intra-prediction mode of the left adjacent block and adding 2 with the result of the modulo arithmetic operation as the mode number, potential intra-prediction mode candidate 4 from the list of potential intra-prediction mode candidates may be retrieved as a DC-intra-prediction mode, and potential intra-prediction mode candidate 5 from the list of potential intra-prediction mode candidates may be retrieved as intra-prediction mode having mode number 2+((candIntraPredModeA+60)%64), i.e. an intra-prediction mode having a value obtained by performing a modulo 64 arithmetic operation on a value obtained by adding 60 to the mode number for the intra-prediction mode of the left adjacent block and adding 2 to the result of the modulo arithmetic operation as the mode number. Thus, for example, when the intra-prediction mode of the left adjacent block and the intra-prediction mode of the upper adjacent block are identical, and the mode number for the intra-prediction mode of the left adjacent block is greater than the mode number for the DC-intra-prediction mode, a list of potentially suitable candidates intra-prediction modes may include a left adjacent block intra-prediction mode, an upper adjacent block intra-prediction mode, an intra-prediction mode with mode number 2+((candIntraPredModeA+61)%64), an intra-prediction mode with mode number 2+((candIntraPredModeA-1)%64) and intra-prediction mode with mode number 2+((candIntraPredModeA+60)%64) as potentially suitable intra-prediction mode options. Here, candIntraPredModeA may represent the mode number for the intra-prediction mode of the left neighboring block relative to the current block.

[508] Meanwhile, when the intra-prediction mode of the left neighboring block and the intra-prediction mode of the upper neighboring block with respect to the current block are not identical, for example, the encoding device may determine whether or not at least one of the mode number for the intra-prediction mode of the left adjacent block and the mode number for the intra-prediction mode of the upper adjacent block; the mode number for the DC-intra-prediction mode. When at least one of the mode number for the intra-prediction mode of the left adjacent block and the mode number for the intra-prediction mode of the upper adjacent block exceeds the mode number for the DC-intra-prediction mode, the minAB variable and the maxAB variable can be retrieved as follows.

[509] - minAB=Min (candIntraPredModeA, candIntraPredModeB)

[510] - maxAB=Max (candIntraPredModeA, candIntraPredModeB)

[511] Here, candIntraPredModeA may represent a mode number for the intra-prediction mode of a left adjacent block relative to the current block, and candIntraPredModeB may represent a mode number for the intra-prediction mode of an upper adjacent block relative to the current block. Thus, minAB may represent the smaller value of the mode number for the intra-prediction mode of the left adjacent block, and the mode number for the intra-prediction mode of the upper adjacent block, maxAB may represent the larger value of the mode number for the intra-prediction mode of the left adjacent block and number mode for the intra-prediction mode of the upper neighboring block.

[512] In addition, when the intra-prediction mode of the left neighbor block and the intra-prediction mode of the upper neighbor block with respect to the current block are not identical, the encoding device can determine whether or not the mode number for the intra-prediction mode of the left neighbor block is greater than the mode number for the DC-intra-prediction mode, and the mode number for the intra-prediction mode of the upper adjacent block is greater than the mode number for the DC-intra-prediction mode.

[513] For example, when the mode number for the intra-prediction mode of the left adjacent block exceeds the mode number for the DC-intra-prediction mode, and the mode number for the intra-prediction mode of the upper adjacent block exceeds the mode number for the DC-intra-prediction mode, the device encoding may extract potential intra-prediction mode candidate 0 - potential intra-prediction mode candidate 3, as described below.

[514] - mpm[0]=INTRA_PLANAR

[515] - mpm[1]=candIntraPredModeA

[516] - mpm[2]=candIntraPredModeB

[517] - mpm[3]=INTRA_DC

[518] Thus, potential intra-prediction mode candidate 0 from the list of potential intra-prediction mode candidates may be retrieved as a planar intra-prediction mode, potential intra-prediction mode candidate 1 from the list of potential intra-prediction mode candidates may be retrieved as the intra-prediction mode of the left adjacent block, potential intra-prediction mode candidate 2 from the list of potential intra-prediction mode candidates may be retrieved as the intra-prediction mode of the top adjacent block, and potential intra-prediction mode candidate 3 from the list of potentially suitable intra-prediction mode candidates may be retrieved as the DC-intra-prediction mode. Here, candIntraPredModeB may represent the mode number for the intra-prediction mode of the upper neighboring block relative to the current block. Thus, for example, when the intra-prediction mode of the left adjacent block and the intra-prediction mode of the upper adjacent block are not identical, and the mode number for the intra-prediction mode of the left adjacent block and the mode number for the intra-prediction mode of the upper adjacent block exceed the mode number for a DC intra-prediction mode, the list of potentially candidate intra-prediction modes may include a left neighbor block intra-prediction mode and a top neighbor block intra-prediction mode as potential candidate intra-prediction modes.

[519] Thereafter, potential candidates for the remaining intra-prediction modes (potential intra-prediction mode candidate 4 and potential intra-prediction mode candidate 5) can be retrieved based on maxAB and minAB. Specifically, potentially suitable candidates for the remaining intra-prediction modes are retrieved based on the difference between a larger value and a smaller value among the mode number for the intra-prediction mode of the left adjacent block and the mode number for the intra-prediction mode of the upper adjacent block.

[520] For example, when the value obtained by subtracting minAB from maxAB is less than 63 and greater than 1 (i.e., when the value obtained by subtracting minAB from maxAB is one of 2-62), the encoder may retrieve a potential candidate 4 intra-prediction modes and a potentially suitable option 5 intra-prediction mode, as described below.

[521] 2+((maxAB+61)%64)

[522] - mpm[5]=2+((maxAB-1)%64)

[523] Thus, potentially suitable intra-prediction mode option 4 from the list of potentially suitable intra-prediction mode options may be retrieved as intra-prediction mode with mode number 2+((maxAB+61)%64), i.e. an intra-prediction mode having a value obtained by performing modulo arithmetic with 64 on a value obtained by adding 61 with maxAB and adding 2 with the result of the modulo arithmetic as the mode number, and a potentially suitable intra-prediction mode option 5 from the list of potentially suitable intra-prediction mode options can be extracted as an intra-prediction mode with mode number 2+((maxAB-1)%64), i.e. an intra-prediction mode having a value obtained by performing a modulo arithmetic operation with 64 on a value obtained by subtracting 1 from maxAB and adding 2 with the result of a modulo arithmetic operation as the mode number. Here, maxAB may represent the greater of the mode number for the intra-prediction mode of the left adjacent block and the mode number for the intra-prediction mode of the upper adjacent block.

[524] Alternatively, when the value obtained by subtracting minAB from maxAB is equal to or greater than 63 or equal to or less than 1, the encoder may extract the potential intra-prediction mode candidate 4 and the potential intra-prediction mode candidate 5, as described below .

[525] - mpm[4]=2+((maxAB+60)%64)

[526] - mpm[5]=2+(maxAB%64)

[527] Thus, potentially suitable intra-prediction mode option 4 from the list of potentially suitable intra-prediction mode options can be retrieved as intra-prediction mode with mode number 2+((maxAB+60)%64), i.e. an intra-prediction mode having a value obtained by performing modulo arithmetic with 64 on a value obtained by adding 60 with maxAB and adding 2 with the result of the modulo arithmetic as the mode number, and a potentially suitable intra-prediction mode option 5 from the list of potentially suitable intra-prediction mode options can be extracted as an intra-prediction mode with mode number 2+(maxAB%64), i.e. an intra-prediction mode having a value obtained by performing a modulo arithmetic operation from 64 to maxAB and adding 2 to the result of the modulo arithmetic operation as the mode number. Here, maxAB may represent the greater of the mode number for the intra-prediction mode of the left adjacent block and the mode number for the intra-prediction mode of the upper adjacent block.

[528] Meanwhile, when the intra-prediction mode of the left neighbor block and the intra-prediction mode of the upper neighbor block with respect to the current block are not identical, or at least one of the mode numbers for the intra-prediction mode of the left neighbor block and the intra mode - the prediction of the upper adjacent block is less than the mode number for the DC intra-prediction mode, the encoding device can determine whether the sum of the mode number for the intra-prediction mode of the left adjacent block and the mode number for the intra-prediction mode of the upper adjacent block number are equal to or greater than mode for DC-intra-prediction mode.

[529] For example, when the sum of the mode number for the intra-prediction mode of the left adjacent block and the mode number for the intra-prediction mode of the upper adjacent block is equal to or greater than the mode number for the DC-intra-prediction mode, the encoder may retrieve a list of potentially suitable mode candidates intra-prediction of the current block, including potentially suitable intra-prediction mode options, as described below.

[530] - mpm[0]=INTRA_PLANAR

[531] - mpm[1]=maxAB

[532] - mpm[2]=INTRA_DC

[533] 2+((maxAB+61)%64)

[534] - mpm[4]=2+((maxAB-1)%64)

[535] - mpm[5]=2+((maxAB+60)%64)

[536] Thus, potential intra-prediction mode candidate 0 from the list of potential intra-prediction mode candidates may be retrieved as the planar intra-prediction mode, potential intra-prediction mode candidate 1 may be retrieved as maxAB, i.e. . Potentially suitable intra-prediction mode option 1 may be retrieved as the intra-prediction mode of the upper adjacent block when the mode number for the intra-prediction mode of the left adjacent block is less than the mode number for the intra-prediction mode of the upper adjacent block, and potential candidate intra-prediction mode option 1 -predictions can be retrieved as the intra-prediction mode of the left neighboring block when the mode number for the intra-prediction mode of the left neighboring block is greater than or equal to the mode number for the intra-prediction mode of the upper neighboring block, potentially suitable option 2 intra-prediction modes from the list of potentially of suitable intra-prediction mode candidates may be retrieved as a DC-intra-prediction mode, potential intra-prediction mode candidate 3 from the list of potential intra-prediction mode candidates may be retrieved as an intra-prediction mode having mode number 2+(( maxAB+61)%64), i.e. intra-prediction mode having the value obtained by performing modulo 64 arithmetic on the value obtained by summing 61 with maxAB and summing 2 with the result of modulo arithmetic as the mode number, potentially suitable intra-prediction mode option 4 from list of potentially suitable intra-prediction mode options can be retrieved as an intra-prediction mode having mode number 2+((maxAB-1)%64), i.e. an intra-prediction mode having a value obtained by performing modulo 64 arithmetic on a value obtained by subtracting 1 from maxAB and adding 2 to the result of the modulo arithmetic as the mode number, and potentially a suitable intra-prediction mode option 5 from the list of potentially suitable intra-prediction mode options can be retrieved as an intra-prediction mode having mode number 2+((maxAB+60)%64), i.e. an intra-prediction mode having a value obtained by performing a modulo arithmetic operation with 64 on a value obtained by adding 60 with maxAB and adding 2 with the result of a modulo arithmetic operation as the mode number.

[537] Alternatively, for example, when the above conditions are not satisfied, the encoder may retrieve a list of potential candidate intra-prediction modes of the current block including potential candidate intra-prediction modes, as described below.

[538] - mpm[0]=INTRA_PLANAR

[539] - mpm[1]=INTRA_DC

[540] - mpm[2]=INTRA_ANGULAR50

[541] - mpm[3]=INTRA_ANGULAR18

[542] - mpm[4]=INTRA_ANGULAR46

[543] - mpm[5]=INTRA_ANGULAR54

[544] Thus, potential intra-prediction mode candidate 0 from the list of potential intra-prediction mode candidates may be retrieved as a planar intra-prediction mode, potential intra-prediction mode candidate 1 from the list of potential intra-prediction mode candidates may be retrieved as a DC intra-prediction mode, potential intra-prediction mode candidate 2 from the list of potential intra-prediction mode candidates may be retrieved as a vertical intra-prediction mode (i.e., intra-prediction mode #50), Potentially suitable intra-prediction mode option 3 from the list of potentially suitable intra-prediction mode options may be retrieved as a horizontal intra-prediction mode (i.e., intra-prediction mode #18), potentially suitable intra-prediction mode option 4 from the list of potentially suitable intra-prediction mode options can be extracted as an intra-prediction mode mode number obtained by subtracting 4 from the mode number for the vertical intra-prediction mode, i.e. intra-prediction mode #46, potential intra-prediction mode candidate 5 from the list of potential intra-prediction mode candidates may be retrieved as the intra-prediction mode of the mode number obtained by summing 4 with the mode number for the vertical intra-prediction mode, i.e. .e. mode #54 intra-prediction. Thus, for example, when the above conditions are not satisfied, the list of potentially suitable intra-prediction mode options may include DC-intra-prediction mode, intra-prediction mode #50, intra-prediction mode #18, intra-prediction mode #46 and intra-prediction mode #54 as potentially suitable intra-prediction mode options.

[545] Meanwhile, for example, when the left neighbor block is not available, intra prediction is not applied to the left neighbor block, and the intra prediction mode of the left neighbor block corresponding to at least one of the cases in which the value of the CIIP flag the top neighbor block is not 1, and the case in which the PCM flag value of the left neighbor block is 1 can be extracted as the planar intra prediction mode. In addition, when the upper neighboring block is not available, intra prediction is not applied to the upper neighboring block, and the intra prediction mode of the left neighboring block corresponding to at least one of the cases in which the value of the CIIP flag of the upper neighboring block is not equal to 1, the case in which the PCM flag value of the upper neighboring block is 1, and the case in which the upper neighboring block is not included in the current CTU, can be extracted as a planar intra-prediction mode.

[546] Meanwhile, a list of potentially suitable intra-prediction mode options generated when the intra-prediction type is the first intra-prediction type, a list of potentially suitable intra-prediction mode options generated when the intra-prediction type is the second type intra-prediction, and the list of potentially suitable intra-prediction mode options generated when the intra-prediction type is the third intra-prediction type may be identical. Thus, an identical list of potentially suitable intra-prediction mode options can be built regardless of the type of intra-prediction for the current block. A list of potentially suitable intra-prediction mode options can be constructed through an identical intra-prediction mode construction process regardless of the intra-prediction type for the current block. The process of constructing the intra-prediction mode may be identical to one of the above-described embodiments.

[547] For example, the encoder may retrieve the intra-prediction mode of the current block based on a list of potentially suitable intra-prediction mode candidates. The encoding device may extract the intra-prediction mode having the optimal RD cost as the intra-prediction mode for the current block by executing various intra-prediction modes. For example, the encoder may retrieve the intra-prediction mode having the optimal RD cost from among the candidate intra-prediction mode candidates in the list of potential intra-prediction mode candidates as the intra-prediction mode for the current block. The intra-prediction mode may be one of two non-directional intra-prediction modes and 65 directed intra-prediction modes. The two non-directional intra-prediction modes may include a DC intra-prediction mode and a planar intra-prediction mode as described above.

[548] For example, the intra-prediction mode of the current block may be selected as one of the intra-prediction modes, except for the planar intra-prediction mode and the DC-intra-prediction mode, where the intra-prediction type for the current block is retrieved as the second type intra-prediction, and selected as one of the intra-prediction modes, except for the DC-intra-prediction mode, where the intra-prediction type for the current block is retrieved as the third intra-prediction type.

[549] For example, the intra-prediction mode of the current block may be selected as one of the intra-prediction modes, except for the planar intra-prediction mode, where the intra-prediction type for the current block is retrieved as the second intra-prediction type, and selected in as one of the intra-prediction modes, except for the DC-intra-prediction mode, where the intra-prediction type for the current block is retrieved as the third intra-prediction type.

[550] For example, the intra-prediction mode of the current block may be selected as one of the intra-prediction modes, except for the planar intra-prediction mode, where the intra-prediction type for the current block is retrieved as the second intra-prediction type.

[551] The encoder may generate an MPM flag indicating whether or not a particular intra-prediction mode is included in the intra-prediction mode candidates from the list of intra-prediction mode candidates. The MPM flag may also be referred to as the "potentially suitable intra-prediction mode option flag". If a particular intra-prediction mode is included among the potential candidate intra-prediction modes from the list of potential candidate intra-prediction modes, the encoder may generate an MPM index indicating the specific intra-prediction mode from among the potential candidates of the intra-prediction modes. The MPM index may also be referred to as the "potentially suitable intra-prediction mode option index". If a specific intra-prediction mode is not included in the potential candidate intra-prediction modes from the list of potential candidate intra-prediction modes, the encoding device may generate remaining intra-prediction mode information indicating the specific intra-prediction mode from among the remaining intra-prediction modes. , which are not included in potentially suitable intra-prediction mode options. Additionally, if a certain intra-prediction mode is included in the candidate intra-prediction mode candidates from the list of potential intra-prediction mode candidates, the encoder may not signal the MPM flag, and the value of the MPM flag may be retrieved as 1. Prediction-related information for the current block may include an MPM flag, an MPM index, and/or remaining intra-prediction mode information.

[552] For example, the encoder may extract a prediction sample of the current block based on the intra-prediction type and the intra-prediction mode.

[553] For example, when the intra-prediction type is extracted as the first intra-prediction type, the encoder may extract at least one reference sample from among the reference samples in the intra-prediction reference lines adjacent to the current block based on intra-prediction mode, and generate discrete prediction samples of the current block based on the reference discrete sample. The reference samples may include a left top reference sample, top reference samples, and left reference samples of the current block. For example, when the size of the current block is WxH, the X-axis component of the current block's top left sample position is xN, and its Y-axis component is yN, the left reference samples may be p[xN-1][yN] - p[xN -1][2H+yN-1], the top left reference sample may be p[xN-1][yN-1], and the top reference sample may be p[xN][yN-1] - p[2W +xN-1][yN-1].

[554] For example, when an intra-prediction type is extracted as a second intra-prediction type, the encoder may extract at least one reference sample from among the reference samples in the intra-prediction reference lines that are not adjacent to the current block, based on the intra-prediction mode, and generate discrete prediction samples of the current block based on the reference discrete sample. Here, the intra-prediction reference lines may be reference lines separated from the top border and/or left border of the current block by 1, 2 or 3 sample distances.

[555] For example, when the intra-prediction type is extracted as the third intra-prediction type, the encoding device may determine the ISP partition type of the current block and segment the current block according to the ISP partition type to extract sub-blocks. The split type may be a horizontal split type or a vertical split type. For example, when the current block size is 4x4, the current block may not be segmented. For example, when the size of the current block is 4x8 and the partition type is a horizontal partition type, the current block may be segmented into two 4x4 sub-blocks. For example, when the size of the current block is 4x8 and the partition type is a vertical partition type, the current block may be segmented into two 2x8 sub-blocks. For example, when the size of the current block is 8×4 and the partition type is a horizontal partition type, the current block may be segmented into two 8×2 sub-blocks. For example, when the size of the current block is 8x4 and the partition type is a vertical partition type, the current block may be segmented into two 4x4 sub-blocks. For example, when the size of the current block is WxH (sizes other than 4x8, 8x4, and 4x4) and the partition type is a horizontal partition type, the current block may be segmented into four WxH/4 sub-blocks. For example, when the current block size is WxH and the partition type is a vertical partition type, the current block may be segmented into four W/4xH sub-blocks. Thereafter, the encoder can perform intra-prediction on the sub-blocks to generate discrete prediction samples. Thus, the encoding device can extract at least one of the reference samples in the intra-prediction reference lines of each sub-block relative to the current block based on the intra-prediction mode, and generate prediction samples based on the reference sample. The intra-prediction reference lines of each sub-block may be reference lines adjacent to each sub-block. Meanwhile, the encoding device can generate and encode an ISP split flag indicating the type of ISP split. The above prediction-related information may include an ISP split flag.

[556] For example, when the intra-prediction mode of the current block is retrieved as the DC-intra-prediction mode, the current block is a square block, the size of the current block is WxH, the X-axis component and the Y-axis component of the top left position of the current block are equal 0, the DC value may be retrieved based on the reference sample at coordinates (0,-refIdx-1) to the reference sample at coordinates (W-1,-refIdx-1) in the upper intra-prediction reference line indicated by the reference index line of the current block, and a reference sample with coordinates (-refIdx-1, 0) to a reference sample with coordinates (-refIdx-1, H-1) in the left intra-prediction reference line indicated by the reference line index. The prediction sample of the current block may be retrieved as a DC value.

[557] For example, when the intra-prediction mode of the current block is retrieved as the DC-intra-prediction mode, the current block is a non-square block whose width is greater than its height, the size of the current block is WxH, an X-axis component, and a Y-axis component the top left position of the current block is 0, the DC value can be retrieved based on the reference sample with coordinates (0,-refIdx-1) to the reference sample with coordinates (W-1,-refIdx-1) in the upper reference line of the intra- prediction indicated by the reference line index of the current block. The prediction sample of the current block may be retrieved as a DC value.

[558] For example, when the intra-prediction mode of the current block is retrieved as the DC-intra-prediction mode, the current block is a non-square block whose height is greater than its width, the size of the current block is WxH, an X-axis component, and a Y-axis component the top left position of the current block is 0, the DC value can be retrieved based on the reference sample with coordinates (-refIdx-1, 0) to the reference sample with coordinates (-refIdx-1, H-1) in the left reference line of the intra- prediction indicated by the reference line index of the current block. The prediction sample of the current block may be retrieved as a DC value.

[559] For example, when the intra-prediction mode of the current block is retrieved as a planar intra-prediction mode, the size of the current block is WxH, the X-axis component and the Y-axis component of the top left position of the current block are 0, the prediction sample can be retrieved at based on a reference sample with coordinates (W-1, -refIdx-1) and a reference sample with coordinates (-refIdx-1, H-1) in the intra-prediction reference line indicated by the reference line index of the current block.

[560] In addition, for example, the encoder may extract a residual sample of the current block based on the prediction sample. The encoding device may extract a residual sample from a difference between the original sample and the prediction sample. Then, for example, the encoder can generate a reconstructed sample of the current block based on the prediction sample and the residual sample. Thereafter, the encoder may apply an in-loop filtering procedure, such as a deblocking and/or SAO filtering procedure, to the recovered sample (i.e., the reconstructed frame) to improve the subjective/objective quality of the frames as needed, as described higher.

[561] The encoder generates prediction-related information for the current block (S2110). The encoder may generate prediction-related information for the current block.

[562] For example, the prediction-related information may include a reference line index of the current block. The reference line index may indicate the intra-prediction reference line of the current block. For example, when the reference line index value is 0, the reference line index may indicate a reference line adjacent to the top border and/or left border of the current block; when the reference line index value is 1, the reference line index may indicate a reference line separated by one sample distance separated by one sample distance from the top and/or left border of the current block when the value of the reference line index is 2, the reference line index may indicate a reference line separated by 2 sample distances from the top and/or left border of the current block when The value of the reference line index is 3, the reference line index may indicate a reference line separated by 3 sample distances from the top border and/or left border of the current block.

[563] In addition, for example, when the reference line index indicates a reference line adjacent to the current block, i.e. when the reference line index value is 0, the prediction-related information may include an intra-subsegment-based (ISP) mode flag. The ISP flag may represent whether or not a third type of intra-prediction to which the ISP is applied is applied to the current block. Thus, the ISP flag may represent whether or not ISP is applied to the current block. For example, when the value of the IPS flag is 1, the ISP flag may represent that the third type of intra-prediction is applied to the current block; when the value of the IPS flag is 0, the ISP flag may represent that the third type of intra-prediction is not applied to the current block. In addition, for example, when the value of the ISP flag is 1, the prediction-related information may include an ISP split flag representing an ISP split type.

[564] In addition, for example, the prediction-related information may include a most probable mode (MPM) flag. Alternatively, for example, the prediction-related information may not include an MPM flag, in which case, the encoder may extract the value of the MPM flag as 1. The MPM flag may represent whether or not the intra-prediction mode of the current block is present. is one of the potentially suitable intra-prediction mode options from a list of potentially suitable intra-prediction mode options. The MPM flag may be referred to as a "potentially suitable intra-prediction mode option flag".

[565] In addition, for example, when the value of the MPM flag is 1, the prediction-related information may include an MPM index. The MPM index may indicate one of the potential candidate intra-prediction modes in the list of potential candidate intra-prediction modes. The MPM index may be signaled in the form of the mpm_idx or intra_luma_mpm_idx syntax element. The MPM index may be referred to as a “potentially suitable intra-prediction mode option index”.

[566] In addition, for example, when the value of the MPM flag is 0, the prediction-related information may include information of the remaining intra-prediction modes. The remaining intra-prediction mode information may indicate one of the remaining intra-prediction modes other than the potential candidate intra-prediction modes in the list of potential candidate intra-prediction modes. The remaining intra-prediction mode information may be signaled in the form of the rem_intra_luma_pred_mode or intra_luma_mpm_remainder syntax element.

[567] The encoding device encodes image information including prediction-related information (S2120). The encoding apparatus can encode image information including prediction-related information, and can output the image information in the form of a bit stream. The prediction-related information may include a reference line index, an ISP flag, and/or an ISP index. In addition, the prediction-related information may include an MPM flag, an MPM index, and/or remaining intra-prediction mode information. In addition, although not illustrated, the encoding apparatus may generate residual information for the current block based on the residual sample, and may encode image information including the residual information, and may output image information in the form of a bitstream. Meanwhile, the bit stream can be transmitted to the decoding device via a network or a (digital) storage medium. Here, the network may include a broadcast network and/or a communications network, and the digital storage medium may include various storage media such as USB, SD, CD, DVD, Blu-Ray, HDD and SSD.

[568] FIG. 22 schematically illustrates an encoding apparatus implementing an image encoding method according to the present disclosure. The method disclosed in FIG. 21 may be performed by the encoding device disclosed in FIG. 22. Specifically, the prediction module of the encoding device of FIG. 22 can perform S2100 of FIG. 21, and the entropy encoder of the encoding device of FIG. 22 may perform S2110-S2120 of FIG. 21. Although not illustrated, the process of extracting the residual sample for the current block based on the original sample and prediction samples for the current block may be performed by the encoder subtractor of FIG. 20, the process of generating residual information regarding the current block based on the residual sample can be performed by the residual processor of the encoding device of FIG. 20, and the encoding process of image information including residual information can be performed by the entropy encoder of the encoding device in FIG. 20.

[569] FIG. 23 schematically illustrates an image decoding method performed by a decoding apparatus according to the present disclosure. The method disclosed in FIG. 23 may be performed by the decoding apparatus disclosed in FIG. 3. In particular, S2300 of FIG. 23 may be performed by an entropy decoder of the decoding device, and S2310 of FIG. 23 may be performed by a prediction unit of the decoding device. In addition, although not illustrated, the process of obtaining image information including residual information for the current block through the bit stream may be performed by an entropy decoder of the decoding apparatus, and the process of extracting a residual sample for the current block based on the residual information may be performed by an inverse converter decoding devices.

[570] The decoding apparatus receives image information including prediction-related information for the current block (S2300). For example, a decoding apparatus may receive and parse image information including prediction-related information and/or residual information for a current block through a bit stream. For example, the prediction-related information may be as shown in Table 2 above.

[571] For example, the prediction-related information may include a reference line index of the current block. The reference line index may indicate the intra-prediction reference line of the current block. For example, when the reference line index value is 0, the reference line index may indicate a reference line adjacent to the top and/or left border of the current block; when the reference line index value is 1, the reference line index may indicate a reference line separated by one sample distance from the top border and/or left border of the current block when the reference line index value is 2, the reference line index may indicate a reference line separated by 2 sample distances from the top border and/or left border of the current block when the reference line index value is 3, the reference line index may indicate a reference line separated by 3 sample distances from the top border and/or left border of the current block.

[572] In addition, for example, when the reference line index indicates a reference line adjacent to the current block, i.e. when the reference line index value is 0, the prediction-related information may include an intra-subsegment-based (ISP) mode flag. The ISP flag may represent whether or not the third type of intra-prediction to which the ISP is applied is applied to the current block. Thus, the ISP flag may represent whether or not ISP is applied to the current block. For example, when the value of the IPS flag is 1, the ISP flag may represent that the third type of intra-prediction is applied to the current block; when the value of the IPS flag is 0, the ISP flag may represent that the third type of intra-prediction is not applied to the current block. In addition, for example, when the value of the ISP flag is 1, the prediction-related information may include an ISP split flag representing the type of ISP split.

[573] In addition, for example, the prediction-related information may include a most likely mode (MPM) flag. Alternatively, for example, the prediction-related information may not include an MPM flag, in which case, the decoding device may extract the value of the MPM flag as 1. The MPM flag may represent whether or not the intra-prediction mode of the current block is present. is one of the potentially suitable intra-prediction mode options from a list of potentially suitable intra-prediction mode options. The MPM flag may be referred to as a "potentially suitable intra-prediction mode option flag".

[574] In addition, for example, when the value of the MPM flag is 1, the prediction-related information may include an MPM index. The MPM index may indicate one of the potential candidate intra-prediction modes in the list of potential candidate intra-prediction modes. The MPM index may be signaled in the form of the mpm_idx or intra_luma_mpm_idx syntax element. The MPM index may be referred to as a “potentially suitable intra-prediction mode option index”.

[575] In addition, for example, when the value of the MPM flag is 0, the prediction-related information may include information of the remaining intra-prediction modes. The remaining intra-prediction mode information may indicate one of the remaining intra-prediction modes other than the potential candidate intra-prediction modes in the list of potential candidate intra-prediction modes. The remaining intra-prediction mode information may be signaled in the form of the rem_intra_luma_pred_mode or intra_luma_mpm_remainder syntax element.

[576] The decoding apparatus generates a reconstructed sample of the current block based on the image information (S2310). The decoding apparatus may extract the prediction sample by performing prediction for the current block, extract the residual sample of the current block based on the residual information for the current block, and generate a reconstructed sample of the current block based on the prediction sample and the residual sample.

[577] For example, the decoding apparatus may extract the intra-prediction type for the current block from the intra-prediction types based on the prediction-related information. The decoding apparatus may extract the intra-prediction type for the current block based on the prediction-related information. Here, the intra-prediction types may include a first type of intra-prediction using intra-prediction reference lines adjacent to the current block, a second type of intra-prediction using intra-prediction reference lines that are not adjacent to the current block, and the third type of intra-prediction, to which the intra-subsegment-based (ISP) mode is applied. The first type of intra-prediction may indicate the above-described general intra-prediction, the second type of intra-prediction may indicate the above-described MRL, and the third type of intra-prediction may indicate the above-described ISP.

[578] For example, the decoding apparatus may extract an intra-prediction type for the current block based on the prediction-related information shown in Table 2. For example, the decoding apparatus may determine whether or not the intra-prediction type for the current block is a second intra-prediction type. -predictions based on the reference line index of the current block. The prediction-related information may include a reference line index. The reference line index may indicate the intra-prediction reference line of the current block. For example, the reference line index may indicate a reference line adjacent to the top and/or left border of the current block, when the reference line index is 0, the reference line index may indicate a reference line separated from the top and/or left border of the current block by one sample distance, when the reference line index is 1, the reference line index may indicate a reference line separated from the top border and/or left border of the current block by 2 sample distances, when the reference line index is 2, and the reference line index may indicate the reference line, separated from the top boundary and/or left boundary of the current block by 3 sample distances when the reference line index is 3. When the reference line index indicates a reference line adjacent to the current block, the decoding device may extract the reference line adjacent to the current block as a reference intra-prediction lines of the current block, and determine that the intra-prediction type for the current block is not a second intra-prediction type. Further, when the reference line index indicates a reference line that is not adjacent to the current block, the decoding apparatus may extract the reference line that is not adjacent to the current block as an intra-prediction reference line of the current block, and extract a second type of intra-prediction in as the intra-prediction type for the current block. Here, a reference line that is not adjacent to the current block may be a reference line separated from the top border and/or left border of the current block by 1, 2 or 3 sample distances.

[579] In addition, when the reference line index indicates a reference line adjacent to the current block, i.e. when the intra-prediction type for the current block is not a second intra-prediction type, the decoding apparatus can determine whether the intra-prediction type for the current block is a third intra-prediction type based on the intra-subsegment-based mode flag (ISP) ). The prediction-related information may include an ISP flag. The ISP flag may indicate whether or not the third type of intra-prediction to which the ISP applies is applied to the current block. Thus, the ISP flag may indicate whether or not ISP is applied to the current block. For example, the ISP flag may indicate that the third type of intra-prediction is applied to the current block when it is set to 1 and may indicate that the third type of intra-prediction is not applied to the current block when it is set to 0. The decoding apparatus may extract the third intra-prediction type as the intra-prediction type for the current block when the ISP flag indicates that the third intra-prediction type is applied, and extract the first intra-prediction type as the intra-prediction type for the current block. , when the ISP flag indicates that the third type of intra-prediction is not applied.

[580] For example, the decoder may construct a list of potentially suitable intra-prediction mode candidates of the current block based on the intra-prediction modes of neighboring blocks relative to the current block.

[581] For example, the decoding device lists the potential candidate intra-prediction mode options of the current block through the process of constructing lists of the potential candidate intra-prediction mode options shown in Table 3. Meanwhile, the list of potential candidate intra-prediction mode options may mean the list described above most probable modes (MPM).

[582] For example, the decoding apparatus may construct a list of potential inter-prediction mode candidates based on the first potential intra-prediction mode candidate and the second potential intra-prediction mode candidate. The decoding apparatus may construct a list of potential inter-prediction mode candidates based on whether or not the first potential intra-prediction mode candidate is identical to the second potential intra-prediction mode candidate, and/or whether or not the mode number of the first candidate is greater than or equal to the first potential intra-prediction mode candidate. a suitable intra-prediction mode option and/or a mode number of a second potentially suitable intra-prediction mode option; a mode number for the DC-intra-prediction mode. Here, the first potential intra-prediction mode candidate may be retrieved based on the intra-prediction mode of the left neighboring block relative to the current block, and the second potential intra-prediction mode candidate may be retrieved based on the intra-prediction mode of the upper neighboring block relative to the current block. For example, the intra-prediction mode of a left neighbor block relative to the current block may be retrieved as a first potential candidate intra-prediction mode, and the intra-prediction mode of an upper neighbor block relative to the current block may be retrieved as a second potential candidate intra-prediction mode.

[583] In particular, when the first potential intra-prediction mode candidate is identical to the second potential intra-prediction mode candidate, for example, the decoding apparatus may determine whether or not the mode number of the first potential intra-prediction mode candidate is greater than the mode number for DC-intra-prediction mode, and if the mode number of the first potentially eligible intra-prediction mode option is greater than the mode number for the DC-intra-prediction mode, retrieve a list of potentially eligible intra-prediction mode options for the current block that includes the potentially eligible options intra-prediction modes as follows.

[584] - mpm[0]=leftIntraDir

[585] - mpm[1]=PLANAR_IDX

[586] - mpm[2]=DC_IDX

[587] - mpm[3]=((leftIntraDir+offset)%mod)+2

[588] - mpm[4]=((leftIntraDir-1)%mod)+2

[589] - mpm[5]=((leftIntraDir+offset-1)%mod)+2

[590] Here, mpm[0], mpm[1], mpm[2], mpm[3], mpm[4] and mpm[5] represent potential intra-prediction mode candidate 0, potential intra-prediction mode candidate 1 -predictions, potential intra-prediction mode candidate 2, potential intra-prediction mode candidate 3, potential intra-prediction mode candidate 4 and potential intra-prediction mode candidate 5, leftIntraDir represents the first potential intra-prediction mode candidate, PLANAR_IDX represents the planar intra-prediction mode, and DC_IDX represents the DC-intra-prediction mode. Thus, potential intra-prediction mode candidate 0 from the list of potential intra-prediction mode candidates may be retrieved as the first potential intra-prediction mode candidate, potential intra-prediction mode candidate 1 from the list of potential intra-prediction mode candidates. may be retrieved as a planar intra-prediction mode, potential intra-prediction mode candidate 2 from the list of potential intra-prediction mode candidates may be retrieved as a DC-intra-prediction mode, potential intra-prediction mode candidate 3 from the list of potential candidates options for intra-prediction modes can be retrieved as an intra-prediction mode having a mode number (leftIntraDir+offset)%mod),+2, i.e. an intra-prediction mode having a value obtained by performing a modulo arithmetic operation on the sum of the mode number of the first potentially suitable intra-prediction mode option and offset and summing 2 with the result of the modulo arithmetic operation as the mode number, a potentially suitable intra-prediction mode option 4 -predictions from the list of potentially suitable intra-prediction mode options can be retrieved as an intra-prediction mode having a mode number ((leftIntraDir-1)%mod)+2, i.e. an intra-prediction mode having a value obtained by performing modulo arithmetic on a value obtained by subtracting 1 from the mode number of the first potentially suitable intra-prediction mode option and adding 2 with the result of the modulo arithmetic as the mode number, and potentially a suitable intra-prediction mode option 5 from the list of potentially suitable intra-prediction mode options can be retrieved as an intra-prediction mode having a mode number ((leftIntraDir+offset-1)%mod)+2, i.e. an intra-prediction mode having a value obtained by performing a modulo arithmetic operation on the sum of the mode number of the first potentially suitable intra-prediction mode option and (offset-1) and summing 2 with the result of the modulo arithmetic operation as the mode number.

[591] For example, when the first potential intra-prediction mode candidate is not identical to the second potential intra-prediction mode candidate, the decoding apparatus may retrieve potential intra-prediction mode candidate 0 and potential intra-prediction mode candidate 1 as follows.

[592] - mpm[0]=leftIntraDir

[593] - mpm[1]=aboveIntraDir

[594] Thus, potential intra-prediction mode candidate 0 from the list of potential intra-prediction mode candidates may be retrieved as the first potential intra-prediction mode candidate, and potential intra-prediction mode candidate 1 from the list of potential candidates. intra-prediction modes may be retrieved as a second potentially suitable intra-prediction mode option. Additionally, the decoder may extract maxCandModeIdx as 0 if the mode number of intra-prediction mode candidate 0 is greater than the mode number of intra-prediction mode candidate 1, and extract maxCandModeIdx as 1 if the mode number of intra-prediction mode candidate 0 -prediction does not exceed the mode number of potentially suitable option 1 intra-prediction mode.

[595] If the mode number of the first potentially suitable intra-prediction mode candidate and the mode number of the second potentially suitable intra-prediction mode candidate exceed the mode number for the DC-intra-prediction mode, the decoding device may retrieve the potential intra-prediction mode candidate 2 and potentially suitable option 3 of intra-prediction mode as follows.

[596] - mpm[2]=PLANAR_IDX

[597] - mpm[3]=DC_IDX

[598] Thus, potential intra-prediction mode candidate 2 from the list of potential intra-prediction mode candidates may be retrieved as a planar intra-prediction mode, and potential intra-prediction mode candidate 3 from the list of potential intra-prediction mode candidates. predictions can be retrieved as DC-intra-prediction mode.

[599] Then, if the value obtained by subtracting the mode number mpm[!maxCandModeIdx] from the mode number mpm[maxCandModeIdx] is less than 63 and greater than 1, the decoder may extract the potential intra-prediction mode candidate 4 and the potential intra-prediction mode candidate 5. predictions as follows.

[600] - mpm[4]=((mpm[maxCandModeIdx]+offset)%mod)+2

[601] - mpm[5]=((mpm[maxCandModeIdx]-1)%mod)+2

[602] Thus, a potential candidate intra-prediction mode option 4 from the list of potential candidate intra-prediction mode candidates may be retrieved as an intra-prediction mode having a mode number ((mpm[maxCandModeIdx]+offset)%mod)+2. those. an intra-prediction mode having a value obtained by performing modulo arithmetic on the sum of mpm[maxCandModeIdx] and offset and summing 2 with the result of the modulo arithmetic as the mode number, and potentially a suitable intra-prediction mode option 5 from the list of potentially suitable intra-prediction mode options can be retrieved as an intra-prediction mode having a mode number ((mpm[maxCandModeIdx]-1)%mod)+2, i.e. an intra-prediction mode having a value obtained by performing modulo arithmetic on a value obtained by subtracting 1 from mpm[maxCandModeIdx] and adding 2 to the result of modulo arithmetic as the mode number.

[603] If the value obtained by subtracting the mode number mpm[!maxCandModeIdx] from the mode number mpm[maxCandModeIdx] is equal to or greater than 63 or equal to or less than 1, the decoder/decoder may retrieve a potentially suitable intra-prediction mode option 4 and A potentially suitable intra-prediction mode option 5 is as follows.

[604] - mpm[4]=((mpm[maxCandModeIdx]+offset-1)%mod)+2

[605] - mpm[5]=((mpm[maxCandModeIdx])%mod)+2

[606] Thus, a potential candidate intra-prediction mode option 4 from the list of potential candidate intra-prediction mode candidates may be retrieved as an intra-prediction mode having a mode number ((mpm[maxCandModeIdx]+offset1)%mod)+2. those. intra-prediction mode having the value obtained by performing modulo arithmetic on the sum of mpm[maxCandModeIdx] and (offset-1) and summing 2 with the result of modulo arithmetic as the mode number, and potentially suitable intra-prediction mode option 5 prediction from the list of potentially suitable intra-prediction mode candidates can be retrieved as an intra-prediction mode having a mode number ((mpm[maxCandModeIdx]%mod)+2, i.e., an intra-prediction mode having a value obtained by performing arithmetic modulo operations for mpm[maxCandModeIdx] and summing 2 with the result of the arithmetic modulo operation as the mode number.

[607] If at least one of the mode number of the first potential intra-prediction mode candidate and the mode number of the second intra-prediction mode candidate is not greater than the mode number for the DC-intra-prediction mode, the decoding device may determine whether is equal to or greater than or not the sum of the mode number of the first potentially suitable intra-prediction mode option and the mode number of the second potentially suitable intra-prediction mode option 2. If the sum of the mode number of the first potentially suitable intra-prediction mode option and the mode number of the second potentially suitable intra-prediction mode option -prediction is equal to or higher than 2, the decoding apparatus may extract the potential candidate intra-prediction mode candidate 2 - potential candidate intra-prediction mode candidate 5 as follows.

[608] - mpm[2]=(mpm[!maxCandModeIdx]==PLANAR_IDX)? DC_IDX: PLANAR_IDX

[609] - mpm[3]=((mpm[maxCandModeIdx]+offset)%mod)+2

[610] - mpm[4]=((mpm[maxCandModeIdx]-1)%mod)+2

[611] - mpm[5]=((mpm[maxCandModeIdx]+offset-1)%mod)+2

[612] Thus, potential intra-prediction mode candidate 2 from the list of potential intra-prediction mode candidates may be retrieved as a DC intra-prediction mode if mpm[!maxCandModeIdx] is a planar intra-prediction mode, and may be retrieved as the planar intra-prediction mode if mpm[!maxCandModeIdx] is not a planar intra-prediction mode. In addition, a potentially suitable intra-prediction mode option 3 from the list of potentially suitable intra-prediction mode options may be retrieved as an intra-prediction mode having a mode number ((mpm[maxCandModeIdx]+offset)%mod)+2, i.e. . intra-prediction mode having the value obtained by performing modulo arithmetic on the sum of mpm[maxCandModeIdx] and offset and summing 2 with the result of modulo arithmetic as the mode number, potentially suitable intra-prediction mode option 4 from the list of potentially suitable intra-prediction mode options can be retrieved as an intra-prediction mode having a mode number ((mpm[maxCandModeIdx]-1)%mod)+2, i.e. an intra-prediction mode having a value obtained by performing modulo arithmetic on a value obtained by subtracting 1 from mpm[maxCandModeIdx] and summing 2 with the result of modulo arithmetic as the mode number, and potentially a suitable intra-prediction mode option 5 prediction from the list of potentially suitable intra-prediction mode options can be retrieved as an intra-prediction mode having a mode number ((mpm[maxCandModeIdx]+offset-1)%mod)+2, i.e. an intra-prediction mode having a value obtained by performing modulo arithmetic on the sum of mpm[maxCandModeIdx] and (offset-1) and summing 2 with the result of modulo arithmetic as the mode number.

[613] If the above conditions are not satisfied, the decoding device may extract the potential intra-prediction mode candidate 0 - potential intra-prediction mode candidate 5 as follows.

[614] - mpm[0]=leftIntraDir

[615] - mpm[1]=(mpm[0]==PLANAR_IDX)? DC_IDX: PLANAR_IDX

[616] - mpm[2]=VER_IDX

[617] - mpm[3]=HOR_IDX

[618] - mpm[4]=VER_IDX-4

[619] - mpm[5]=VER_IDX+4

[620] Thus, potential intra-prediction mode candidate 0 from the list of potential intra-prediction mode candidates may be retrieved as the first potential intra-prediction mode candidate, potential intra-prediction mode candidate 1 from the list of potential intra-prediction mode candidates. intra-prediction mode may be retrieved as a DC-intra-prediction mode if the potential intra-prediction mode candidate 0 is a planar intra-prediction mode, and retrieved as a planar intra-prediction mode if the potential intra-prediction mode candidate 0 is an intra-prediction mode does not represent a planar intra-prediction mode, potentially suitable intra-prediction mode option 2 from the list of potentially suitable intra-prediction mode options can be retrieved as a vertical intra-prediction mode, potentially suitable intra-prediction mode option 3 from the list of potentially suitable intra-prediction mode options intra-prediction mode may be retrieved as a horizontal intra-prediction mode, potential intra-prediction mode candidate 4 from the list of potential intra-prediction mode candidates may be retrieved as an intra-prediction mode corresponding to the mode number obtained by subtracting 4 from the mode number for the vertical intra-prediction mode, i.e. intra-prediction mode #46 and potential intra-prediction mode candidate 5 from the list of potential intra-prediction mode candidates may be retrieved as the intra-prediction mode corresponding to the mode number obtained by summing 4 with the mode number for the vertical intra-prediction mode , i.e. mode #54 intra-prediction.

[621] For example, the decoding device may perform the list-building process of potential intra-prediction mode candidate candidates shown in Table 4 to construct a list of potential intra-prediction mode candidate candidates for the current block.

[622] For example, the decoding apparatus may construct a list of potential intra-prediction mode candidates based on the first potential intra-prediction mode candidate and the second potential intra-prediction mode candidate. The decoding apparatus may construct a list of potential inter-prediction mode candidates based on whether or not the first potential intra-prediction mode candidate is identical to the second potential intra-prediction mode candidate, and/or whether or not the mode number of the first candidate is greater than or equal to the first potential intra-prediction mode candidate. a suitable intra-prediction mode option and/or a mode number of a second potentially suitable intra-prediction mode option; a mode number for the DC-intra-prediction mode. Here, the first potential intra-prediction mode candidate may be retrieved based on the intra-prediction mode of the left neighboring block relative to the current block, and the second potential intra-prediction mode candidate may be retrieved based on the intra-prediction mode of the upper neighboring block relative to the current block. For example, the intra-prediction mode of a left neighbor block relative to the current block may be retrieved as a first potential candidate intra-prediction mode, and the intra-prediction mode of an upper neighbor block relative to the current block may be retrieved as a second potential candidate intra-prediction mode.

[623] In particular, when the first potential intra-prediction mode candidate is identical to the second potential intra-prediction mode candidate, for example, the decoding apparatus may determine whether or not the mode number of the first potential intra-prediction mode candidate is greater than the mode number for DC-intra-prediction mode, and if the mode number of the first potentially eligible intra-prediction mode option is greater than the mode number for the DC-intra-prediction mode, retrieve a list of potentially eligible intra-prediction mode options for the current block that includes the potentially eligible options intra-prediction modes as follows.

[624] - mpm[0]=leftIntraDir

[625] - mpm[1]=PLANAR_IDX

[626] - mpm[2]=((leftIntraDir+offset)%mod)+2

[627] - mpm[3]=((leftIntraDir-1)%mod)+2

[628] - mpm[4]=DC_IDX

[629] - mpm[5]=((leftIntraDir+offset-1)%mod)+2

[630] Here, mpm[0], mpm[1], mpm[2], mpm[3], mpm[4] and mpm[5] represent potential intra-prediction mode candidate 0, potential intra-prediction mode candidate 1 -predictions, potential intra-prediction mode candidate 2, potential intra-prediction mode candidate 3, potential intra-prediction mode candidate 4 and potential intra-prediction mode candidate 5, leftIntraDir represents the first potential intra-prediction mode candidate, PLANAR_IDX represents the planar intra-prediction mode, and DC_IDX represents the DC-intra-prediction mode. Thus, potential intra-prediction mode candidate 0 from the list of potential intra-prediction mode candidates may be retrieved as the first potential intra-prediction mode candidate, potential intra-prediction mode candidate 1 from the list of potential intra-prediction mode candidates may be retrieved as a planar intra-prediction mode, potential intra-prediction mode candidate 2 from the list of potential intra-prediction mode candidates may be retrieved as an intra-prediction mode having mode number ((leftIntraDir+offset)%mod)+2 , i.e. an intra-prediction mode having a value obtained by performing a modulo arithmetic operation on the sum of the mode number of the first potentially suitable intra-prediction mode option and offset and summing 2 with the result of the modulo arithmetic operation as the mode number, a potentially suitable intra-prediction mode option 3 -predictions from the list of potentially suitable intra-prediction mode options can be retrieved as an intra-prediction mode having a mode number ((leftIntraDir-1)%mod)+2, i.e. an intra-prediction mode having a value obtained by performing a modulo arithmetic operation on a value obtained by subtracting 1 from the mode number of the first potentially suitable intra-prediction mode option and summing 2 with the result of the modulo arithmetic operation as the mode number potentially suitable intra-prediction mode option 4 from the list of potentially suitable intra-prediction mode options may be retrieved as a DC-intra-prediction mode, and potential intra-prediction mode option 5 from the list of potentially suitable intra-prediction mode options may be retrieved as the intra-prediction mode -prediction with mode number ((leftIntraDir+offset-1)%mod)+2, i.e. an intra-prediction mode having a value obtained by performing a modulo arithmetic operation on the sum of the mode number of the first potentially suitable intra-prediction mode option and (offset-1) and summing 2 with the result of the modulo arithmetic operation as the mode number.

[631] For example, when the first potential intra-prediction mode candidate is not identical to the second potential intra-prediction mode candidate, the decoding apparatus may retrieve potential intra-prediction mode candidate 0 and potential intra-prediction mode candidate 1 as follows.

[632] - mpm[0]=leftIntraDir

[633] - mpm[1]=aboveIntraDir

[634] Thus, potential intra-prediction mode candidate 0 from the list of potential intra-prediction mode candidates may be retrieved as the first potential intra-prediction mode candidate, and potential intra-prediction mode candidate 1 from the list of potential candidates. intra-prediction modes may be retrieved as a second potentially suitable intra-prediction mode option. Additionally, the decoder may extract maxCandModeIdx as 0 if the mode number of intra-prediction mode candidate 0 is greater than the mode number of intra-prediction mode candidate 1, and extract maxCandModeIdx as 1 if the mode number of intra-prediction mode candidate 0 is greater than the mode number of intra-prediction mode candidate 1. -prediction does not exceed the mode number of potentially suitable option 1 intra-prediction mode.

[635] If the mode number of the first potentially suitable intra-prediction mode candidate and the mode number of the second potentially suitable intra-prediction mode candidate exceed the mode number for the DC-intra-prediction mode, the decoding device may retrieve the potential intra-prediction mode candidate 1 - potentially suitable option 3 of intra-prediction mode as follows.

[636] - mpm[1]=PLANAR_IDX

[637] - mpm[2]=aboveIntraDir

[638] - maxCandModeIdx=mpm[0]>mpm[2]? 0:2

[639] - interval minCandModeidx=mpm[0]>mpm[2]? 20

[640] - mpm[3]=DC_IDX;

[641] Thus, potential candidate intra-prediction mode option 1 from the list of potential candidates for intra-prediction modes may be retrieved as a planar intra-prediction mode, potential candidate intra-prediction mode option 2 from the list of potential candidates for intra-prediction modes may be retrieved as a second potential intra-prediction mode candidate, and intra-prediction mode candidate 3 from the list of potential intra-prediction mode candidates may be retrieved as a DC intra-prediction mode. Additionally, the decoder may extract maxCandModeIdx as 0 if the mode number of intra-prediction mode candidate 0 is greater than the mode number of intra-prediction mode candidate 2, and extract maxCandModeIdx as 2 if the mode number of intra-prediction mode candidate 0 is greater than the mode number of intra-prediction mode candidate 2. -prediction does not exceed the mode number of the potentially suitable option 2 of the intra-prediction mode. Additionally, the decoder may extract minCandModeidx as 2 if the mode number of intra-prediction mode candidate 0 is greater than the mode number of intra-prediction mode candidate 2, and extract minCandModeidx as 0 if the mode number of intra-prediction mode candidate 0 -prediction does not exceed the mode number of the potentially suitable option 2 of the intra-prediction mode.

[642] If the value obtained by subtracting the mode number mpm[minCandModeidx] from the mode number mpm[maxCandModeIdx] is less than 63 and greater than 1, the decoder/decoding device may retrieve a potential intra-prediction mode candidate 4 and a potential intra-prediction mode candidate 5 intra-predictions as follows.

[643] - mpm[4]=((mpm[maxCandModeIdx]+offset)%mod)+2

[644] - mpm[5]=((mpm[maxCandModeIdx]-1)%mod)+2

[645] Thus, a potential candidate intra-prediction mode option 4 from the list of potential candidate intra-prediction mode candidates may be retrieved as an intra-prediction mode having a mode number ((mpm[maxCandModeIdx]+offset)%mod)+2. those. an intra-prediction mode having a value obtained by performing modulo arithmetic on the sum of mpm[maxCandModeIdx] and offset and summing 2 with the result of the modulo arithmetic as the mode number, and potentially a suitable intra-prediction mode option 5 from the list of potentially suitable intra-prediction mode options can be retrieved as an intra-prediction mode having a mode number ((mpm[maxCandModeIdx]-1)%mod)+2, i.e. an intra-prediction mode having a value obtained by performing modulo arithmetic on a value obtained by subtracting 1 from mpm[maxCandModeIdx] and adding 2 to the result of modulo arithmetic as the mode number.

[646] If the value obtained by subtracting the mode number mpm[minCandModeidx] from the mode number mpm[maxCandModeIdx] is equal to or greater than 63 or equal to or less than 1, the decoding device/decoding device may retrieve a potentially suitable intra-prediction mode option 4 and potentially suitable option 5 of intra-prediction mode as follows.

[647] - mpm[4]=((mpm[maxCandModeIdx]+offset-1)%mod)+2

[648] - mpm[5]=((mpm[maxCandModeIdx])%mod)+2

[649] Thus, a potential candidate intra-prediction mode option 4 from a list of potential candidate intra-prediction mode candidates may be retrieved as an intra-prediction mode having a mode number ((mpm[maxCandModeIdx]+offset-1)%mod)+ 2, i.e. an intra-prediction mode having a value obtained by performing modulo arithmetic on the sum of mpm[maxCandModeIdx] and (offset-1) and summing 2 with the result of the modulo arithmetic as the mode number, and a potentially suitable intra-prediction mode option 5 prediction from the list of potentially suitable intra-prediction mode options can be retrieved as an intra-prediction mode having mode number ((mpm[maxCandModeIdx])%mod)+2, i.e. an intra-prediction mode having a value obtained by performing modulo arithmetic on mpm[maxCandModeIdx] and summing 2 with the result of modulo arithmetic as the mode number.

[650] If at least one of the mode number of the first potential intra-prediction mode candidate candidate and the mode number of the second intra-prediction mode candidate candidate is not greater than the mode number for the DC intra-prediction mode, the decoding apparatus may determine whether is equal to or greater than or not the sum of the mode number of the first potentially suitable intra-prediction mode option and the mode number of the second potentially suitable intra-prediction mode option 2. If the sum of the mode number of the first potentially suitable intra-prediction mode option and the mode number of the second potentially suitable intra-prediction mode option -prediction is equal to or greater than 2, the decoding apparatus may determine whether or not at least one of the first potentially suitable intra-prediction mode option and the second potentially suitable intra-prediction mode option is a planar intra-prediction mode.

[651] If at least one of the first potential intra-prediction mode candidate and the second potential intra-prediction mode candidate is a planar intra-prediction mode, the decoding apparatus may extract potential intra-prediction mode candidate 0 and potentially suitable option 1 of intra-prediction mode as follows.

[652] - mpm[0]=PLANAR_IDX

[653] - mpm[1]=(leftIntraDir<aboveIntraDir)? aboveIntraDir: leftIntraDir

[654] - maxCandModeIdx=1

[655] Thus, potential intra-prediction mode candidate 0 from the list of potential intra-prediction mode candidates may be retrieved as a planar intra-prediction mode, potential intra-prediction mode candidate 1 from the list of potential intra-prediction mode candidates may be retrieved as the second potential intra-prediction mode candidate if the mode number of the first intra-prediction mode candidate is less than the mode number of the second intra-prediction mode candidate, and retrieved as the first intra-prediction mode candidate if the mode number of the first potentially suitable intra-prediction mode option is equal to or greater than the mode number of the second potentially suitable intra-prediction mode option. Additionally, the decoder may extract maxCandModeIdx as 1.

[656] If the first potential intra-prediction mode candidate and the second potential intra-prediction mode candidate are not a planar intra-prediction mode, the decoding device may retrieve potential intra-prediction mode candidate 2 - potential intra-prediction mode candidate 5 predictions as follows.

[657] - mpm[2]=(mpm[!maxCandModeIdx]==PLANAR_IDX)? DC_IDX: PLANAR_IDX

[658] - mpm[3]=((mpm[maxCandModeIdx]+offset)%mod)+2

[659] - mpm[4]=((mpm[maxCandModeIdx]-1)%mod)+2

[660] - mpm[5]=((mpm[maxCandModeIdx]+offset-1)%mod)+2

[661] Thus, potential intra-prediction mode candidate 2 from the list of potential intra-prediction mode candidates may be retrieved as a DC intra-prediction mode if mpm[!maxCandModeIdx] is a planar intra-prediction mode, and may be retrieved as the planar intra-prediction mode if mpm[!maxCandModeIdx] is not a planar intra-prediction mode. In addition, the potential intra-prediction mode candidate 3 from the list of potential intra-prediction mode candidates may be retrieved as an intra-prediction mode having a mode number ((mpm[maxCandModeIdx]+offset)%mod)+2, i.e. . intra-prediction mode having the value obtained by performing modulo arithmetic on the sum of mpm[maxCandModeIdx] and offset and summing 2 with the result of modulo arithmetic as the mode number, potentially suitable intra-prediction mode option 4 from the list of potentially suitable intra-prediction mode options can be retrieved as an intra-prediction mode having a mode number ((mpm[maxCandModeIdx]-1)%mod)+2, i.e. an intra-prediction mode having a value obtained by performing modulo arithmetic on a value obtained by subtracting 1 from mpm[maxCandModeIdx] and summing 2 with the result of modulo arithmetic as the mode number, and potentially a suitable intra-prediction mode option 5 prediction from the list of potentially suitable intra-prediction mode options can be retrieved as an intra-prediction mode having a mode number ((mpm[maxCandModeIdx]+offset-1)%mod)+2, i.e. an intra-prediction mode having a value obtained by performing modulo arithmetic on the sum of mpm[maxCandModeIdx] and (offset-1) and summing 2 with the result of modulo arithmetic as the mode number.

[662] If the above conditions are not satisfied, the decoding apparatus may extract the intra-prediction mode candidate candidate 0 to the intra-prediction mode candidate candidate 5 as follows.

[663] - mpm[0]=leftIntraDir

[664] - mpm[1]=(mpm[0]==PLANAR_IDX)? DC_IDX: PLANAR_IDX

[665] - mpm[2]=VER_IDX

[666] - mpm[3]=HOR_IDX

[667] - mpm[4]=VER_IDX-4

[668] - mpm[5]=VER_IDX+4

[669] Thus, potential intra-prediction mode candidate 0 from the list of potential intra-prediction mode candidates may be retrieved as the first potential intra-prediction mode candidate, potential intra-prediction mode candidate 1 from the list of potential intra-prediction mode candidates. intra-prediction mode may be retrieved as a DC-intra-prediction mode if the potential intra-prediction mode candidate 0 is a planar intra-prediction mode, and retrieved as a planar intra-prediction mode if the potential intra-prediction mode candidate 0 is an intra-prediction mode does not represent a planar intra-prediction mode, potentially suitable intra-prediction mode option 2 from the list of potentially suitable intra-prediction mode options can be retrieved as a vertical intra-prediction mode, potentially suitable intra-prediction mode option 3 from the list of potentially suitable intra-prediction mode options intra-prediction mode may be retrieved as a horizontal intra-prediction mode, potential intra-prediction mode candidate 4 from the list of potential intra-prediction mode candidates may be retrieved as an intra-prediction mode corresponding to the mode number obtained by subtracting 4 from the mode number for the vertical intra-prediction mode, i.e. intra-prediction mode #46 and potential intra-prediction mode candidate 5 from the list of potential intra-prediction mode candidates may be retrieved as the intra-prediction mode corresponding to the mode number obtained by summing 4 with the mode number for the vertical intra-prediction mode , i.e. mode #54 intra-prediction.

[670] For example, the decoding device may perform the list-building process of potential intra-prediction mode candidate candidates shown in Table 5 to construct a list of potential intra-prediction mode candidate candidates for the current block.

[671] For example, the decoding device may construct a list of potential intra-prediction mode candidates based on the first potential intra-prediction mode candidate and the second potential intra-prediction mode candidate. The decoding apparatus may construct a list of potential inter-prediction mode candidates based on whether or not the first potential intra-prediction mode candidate is identical to the second potential intra-prediction mode candidate, and/or whether or not the mode number of the first candidate is greater than or equal to the first potential intra-prediction mode candidate. a suitable intra-prediction mode option and/or a mode number of a second potentially suitable intra-prediction mode option; a mode number for the DC-intra-prediction mode. Here, the first potential intra-prediction mode candidate may be retrieved based on the intra-prediction mode of the left neighboring block relative to the current block, and the second potential intra-prediction mode candidate may be retrieved based on the intra-prediction mode of the upper neighboring block relative to the current block. For example, the intra-prediction mode of a left neighbor block relative to the current block may be retrieved as a first potential candidate intra-prediction mode, and the intra-prediction mode of an upper neighbor block relative to the current block may be retrieved as a second potential candidate intra-prediction mode.

[672] In particular, when the first potential intra-prediction mode candidate is identical to the second potential intra-prediction mode candidate, for example, the decoding device may determine whether or not the mode number of the first potential intra-prediction mode candidate is greater than the mode number for DC-intra-prediction mode, and if the mode number of the first potentially eligible intra-prediction mode option is greater than the mode number for the DC-intra-prediction mode, retrieve a list of potentially eligible intra-prediction mode options for the current block that includes the potentially eligible options intra-prediction modes as follows.

[673] - mpm[0]=g_intraMode65to33AngMapping[leftIntraDir]

[674] - mpm[1]=((g_intraMode65to33AngMapping[leftIntraDir]+offset)%mod)+2

[675] - mpm[2]=((g_intraMode65to33AngMapping[leftIntraDir]-1)%mod)+2

[676] Thus, potential intra-prediction mode candidate 0 from the list of potential intra-prediction mode candidates may be retrieved as the first potential intra-prediction mode candidate. In addition, potentially suitable intra-prediction mode option 1 from the list of potentially suitable intra-prediction mode options can be retrieved as an intra-prediction mode having mode number ((g_intraMode65to33AngMapping[leftIntraDir]+offset)%mod)+2, i.e. . an intra-prediction mode having a value obtained by performing a modulo arithmetic operation on the sum of the mode number of the first potentially suitable intra-prediction mode option and offset and summing 2 with the result of the modulo arithmetic operation as the mode number, and the potentially suitable mode option 2 intra-prediction from the list of potentially suitable intra-prediction mode options can be retrieved as an intra-prediction mode having a mode number ((g_intraMode65to33AngMapping[leftIntraDir]-1)%mod)+2, i.e. an intra-prediction mode having a value obtained by performing a modulo arithmetic operation on a value obtained by subtracting 1 from the mode number of the first potentially suitable intra-prediction mode option and adding 2 with the result of the modulo arithmetic operation as the mode number.

[677] If the mode number of the first potentially eligible intra-prediction mode candidate is not greater than the mode number for the DC-intra-prediction mode, the decoding device may retrieve a list of potentially eligible intra-prediction mode candidates for the current block that includes the potential candidate mode options intra-predictions as follows.

[678] - mpm[0]=g_intraMode65to33AngMapping[PLANAR_IDX]

[679] - mpm[1]=g_intraMode65to33AngMapping[DC_IDX]

[680] - mpm[2]=g_intraMode65to33AngMapping[VER_IDX]

[681] Thus, potential intra-prediction mode candidate 0 from the list of potential intra-prediction mode candidates may be retrieved as a planar intra-prediction mode, potential intra-prediction mode candidate 1 from the list of potential intra-prediction mode candidates may be retrieved as a DC intra-prediction mode, and a potential intra-prediction mode candidate 2 from the list of potential intra-prediction mode candidates may be retrieved as a vertical intra-prediction mode.

[682] Additionally, if the first potential intra-prediction mode candidate is not identical to the second potential intra-prediction mode candidate, the decoding apparatus may retrieve potential intra-prediction mode candidate 0 and potential intra-prediction mode candidate 1.

[683] - mpm[0]=g_intraMode65to33AngMapping[leftIntraDir]

[684] - mpm[1]=g_intraMode65to33AngMapping[aboveIntraDir]

[685] Thus, potential intra-prediction mode candidate 0 from the list of potential intra-prediction mode candidates may be retrieved as the first potential intra-prediction mode candidate, and potential intra-prediction mode candidate 1 from the list of potential candidates. intra-prediction modes may be retrieved as a second potentially suitable intra-prediction mode option.

[686] Then, if both the first potential intra-prediction mode candidate and the second potential intra-prediction mode candidate are planar intra-prediction mode, the decoding device may retrieve the intra-prediction mode candidate 2 as follows.

[687] - mpm[2]=g_intraMode65to33AngMapping[PLANAR_IDX]

[688] Thus, potential intra-prediction mode candidate 2 from the list of potential intra-prediction mode candidates may be retrieved as a planar intra-prediction mode.

[689] Alternatively, if at least one of the first potential intra-prediction mode candidate and the second potential intra-prediction mode candidate is a planar intra-prediction mode, the decoding device may retrieve intra-prediction candidate 2. -predictions as follows.

[690] - mpm[2]=g_intraMode65to33AngMapping [(leftIntraDir+aboveIntraDir)<2? VER_IDX:DC_IDX]

[691] Thus, potential intra-prediction mode candidate 2 from the list of potentially suitable intra-prediction mode candidates may be retrieved as a vertical intra-prediction mode if the sum of the mode number of the first potentially suitable intra-prediction mode candidate and the mode number of the second potentially suitable intra-prediction mode candidate is less than 2, and retrieved as a DC-intra-prediction mode if the sum of the mode number of the first potentially suitable intra-prediction mode candidate and the mode number of the second potentially suitable intra-prediction mode candidate is equal to or greater than 2.

[692] For example, the decoding device may construct a list of potentially suitable intra-prediction mode candidates of the current block based on the intra-prediction modes of neighboring blocks relative to the current block, as shown in Table 6. Meanwhile, the list of potentially suitable intra-prediction mode candidates may mean the above list of most probable modes (MPM).

[693] For example, the decoder may construct a list of potentially suitable intra-prediction mode candidates based on the intra-prediction mode of the left neighbor block relative to the current block and the intra-prediction mode of the top neighbor block relative to the current block. The decoding apparatus can determine whether or not the intra-prediction mode of the left neighbor block and the intra-prediction mode of the upper neighbor block are identical with respect to the current block, and whether or not the mode number for the intra-prediction mode of the left neighbor block is greater than the mode number for the DC mode. -intra-predictions. The decoding apparatus may construct a list of potentially suitable intra-prediction mode candidates based on whether or not the intra-prediction mode of a left adjacent block and the intra-prediction mode of an upper adjacent block relative to the current block are identical, and/or the mode number for the intra-prediction mode the left adjacent block exceeds the mode number for the DC-intra-prediction mode.

[694] When the intra-prediction mode of the left adjacent block and the intra-prediction mode of the upper adjacent block with respect to the current block are identical, and the mode number for the intra-prediction mode of the left adjacent block is greater than the mode number for the DC-intra-prediction mode, the decoding device may retrieve a list of potential candidate intra-prediction mode options for the current block, including potential candidate intra-prediction mode options, as described below.

[695] - mpm[0]=INTRA_PLANAR

[696] - mpm[1]=candIntraPredModeA

[697] 2+((candIntraPredModeA+61)%64)

[698] - mpm[3]=2+((candIntraPredModeA-1)%64)

[699] - mpm[4]=INTRA_DC

[700] - mpm[5]=2+((candIntraPredModeA+60)%64)

[701] Thus, potential intra-prediction mode candidate 0 from the list of potential intra-prediction mode candidates may be retrieved as a planar intra-prediction mode, potential intra-prediction mode candidate 1 from the list of potential intra-prediction mode candidates can be retrieved as the intra-prediction mode of the left adjacent block, a potential candidate intra-prediction mode option 2 from the list of potential candidates for intra-prediction modes can be retrieved as an intra-prediction mode having mode number 2+((candIntraPredModeA+61)% 64), i.e. an intra-prediction mode having a value obtained by performing a modulo 64 arithmetic operation on a value obtained by adding 61 to the mode number for the intra-prediction mode of the left adjacent block and adding 2 to the modulo arithmetic operation result as the mode number, Potentially suitable intra-prediction mode option 3 from the list of potentially suitable intra-prediction mode options may be retrieved as an intra-prediction mode having mode number 2+((candIntraPredModeA-1)%64), i.e. an intra-prediction mode having a value obtained by performing a modulo 64 arithmetic operation on a value obtained by subtracting 1 from the mode number for the intra-prediction mode of the left adjacent block and adding 2 with the result of the modulo arithmetic operation as the mode number, potential intra-prediction mode candidate 4 from the list of potential intra-prediction mode candidates may be retrieved as a DC-intra-prediction mode, and potential intra-prediction mode candidate 5 from the list of potential intra-prediction mode candidates may be retrieved as intra-prediction mode having mode number 2+((candIntraPredModeA+60)%64), i.e. an intra-prediction mode having a value obtained by performing a modulo 64 arithmetic operation on a value obtained by adding 60 to the mode number for the intra-prediction mode of the left adjacent block and adding 2 to the result of the modulo arithmetic operation as the mode number. Thus, for example, when the intra-prediction mode of the left adjacent block and the intra-prediction mode of the upper adjacent block are identical, and the mode number for the intra-prediction mode of the left adjacent block is greater than the mode number for the DC-intra-prediction mode, a list of potentially suitable candidates intra-prediction modes may include a left adjacent block intra-prediction mode, an upper adjacent block intra-prediction mode, an intra-prediction mode with mode number 2+((candIntraPredModeA+61)%64), an intra-prediction mode with mode number 2+((candIntraPredModeA-1)%64) and intra-prediction mode with mode number 2+((candIntraPredModeA+60)%64) as potentially suitable intra-prediction mode options. Here, candIntraPredModeA may represent the mode number for the intra-prediction mode of the left neighboring block relative to the current block.

[702] Meanwhile, when the intra-prediction mode of the left neighboring block and the intra-prediction mode of the upper neighboring block with respect to the current block are not identical, for example, the decoding apparatus may determine whether or not at least one of the mode number for the intra-prediction mode of the left adjacent block and the mode number for the intra-prediction mode of the upper adjacent block; the mode number for the DC-intra-prediction mode. When at least one of the mode number for the intra-prediction mode of the left adjacent block and the mode number for the intra-prediction mode of the upper adjacent block exceeds the mode number for the DC-intra-prediction mode, the minAB variable and the maxAB variable can be retrieved as follows.

[703] - minAB=Min (candIntraPredModeA, candIntraPredModeB)

[704] - maxAB=Max (candIntraPredModeA, candIntraPredModeB)

[705] Here, candIntraPredModeA may represent a mode number for the intra-prediction mode of a left neighboring block relative to the current block, and candIntraPredModeB may represent a mode number for the intra-prediction mode of an upper neighboring block relative to the current block. Thus, minAB may represent the smaller value of the mode number for the intra-prediction mode of the left adjacent block, and the mode number for the intra-prediction mode of the upper adjacent block, maxAB may represent the larger value of the mode number for the intra-prediction mode of the left adjacent block and number mode for the intra-prediction mode of the upper neighboring block.

[706] In addition, when the intra-prediction mode of the left neighbor block and the intra-prediction mode of the upper neighbor block with respect to the current block are not identical, the decoding apparatus can determine whether or not the mode number for the intra-prediction mode of the left neighbor block is greater than the mode number for the DC-intra-prediction mode, and the mode number for the intra-prediction mode of the upper adjacent block is greater than the mode number for the DC-intra-prediction mode.

[707] For example, when the mode number for the intra-prediction mode of the left adjacent block exceeds the mode number for the DC-intra-prediction mode, and the mode number for the intra-prediction mode of the upper adjacent block exceeds the mode number for the DC-intra-prediction mode, the device decoding may extract potential intra-prediction mode candidate 0 - potential intra-prediction mode candidate 3, as described below.

[708] - mpm[0]=INTRA_PLANAR

[709] - mpm[1]=candIntraPredModeA

[710] - mpm[2]=candIntraPredModeB

[711] - mpm[3]=INTRA_DC

[712] Thus, potential intra-prediction mode candidate 0 from the list of potential intra-prediction mode candidates may be retrieved as a planar intra-prediction mode, potential intra-prediction mode candidate 1 from the list of potential intra-prediction mode candidates may be retrieved as the intra-prediction mode of the left adjacent block, potential intra-prediction mode candidate 2 from the list of potential intra-prediction mode candidates may be retrieved as the intra-prediction mode of the top adjacent block, and potential intra-prediction mode candidate 3 from the list of potentially suitable intra-prediction mode candidates may be retrieved as the DC-intra-prediction mode. Here, candIntraPredModeB may represent the mode number for the intra-prediction mode of the upper neighboring block relative to the current block. Thus, for example, when the intra-prediction mode of the left adjacent block and the intra-prediction mode of the upper adjacent block are not identical, and the mode number for the intra-prediction mode of the left adjacent block and the mode number for the intra-prediction mode of the upper adjacent block exceed the mode number for a DC intra-prediction mode, the list of potentially candidate intra-prediction modes may include a left neighbor block intra-prediction mode and a top neighbor block intra-prediction mode as potential candidate intra-prediction modes.

[713] Thereafter, potential candidates for the remaining intra-prediction modes (potential intra-prediction mode candidate 4 and potential intra-prediction mode candidate 5) can be retrieved based on maxAB and minAB. Specifically, potentially suitable candidates for the remaining intra-prediction modes are retrieved based on the difference between a larger value and a smaller value among the mode number for the intra-prediction mode of the left adjacent block and the mode number for the intra-prediction mode of the upper adjacent block.

[714] For example, when the value obtained by subtracting minAB from maxAB is less than 63 and greater than 1 (i.e., when the value obtained by subtracting minAB from maxAB is one of 2-62), the decoding device may extract a potential candidate 4 intra-prediction modes and a potentially suitable option 5 intra-prediction mode, as described below.

[715] 2+((maxAB+61)%64)

[716] - mpm[5]=2+((maxAB-1)%64)

[717] Thus, potentially suitable intra-prediction mode option 4 from the list of potentially suitable intra-prediction mode options may be retrieved as intra-prediction mode with mode number 2+((maxAB+61)%64), i.e. an intra-prediction mode having a value obtained by performing a modulo arithmetic operation with 64 on a value obtained by adding 61 with maxAB and adding 2 with the result of a modulo arithmetic operation as the mode number, and a potentially suitable intra-prediction mode option 5 from the list of potentially suitable intra-prediction mode options can be extracted as an intra-prediction mode with mode number 2+((maxAB-1)%64), i.e. an intra-prediction mode having a value obtained by performing a modulo arithmetic operation with 64 on a value obtained by subtracting 1 from maxAB and adding 2 with the result of a modulo arithmetic operation as the mode number. Here, maxAB may represent the greater of the mode number for the intra-prediction mode of the left adjacent block and the mode number for the intra-prediction mode of the upper adjacent block.

[718] Alternatively, when the value obtained by subtracting minAB from maxAB is equal to or greater than 63 or equal to or less than 1, the decoding device may extract the potential intra-prediction mode candidate 4 and the potential intra-prediction mode candidate 5, as described below. .

[719] - mpm[4]=2+((maxAB+60)%64)

[720] - mpm[5]=2+(maxAB%64)

[721] Thus, potentially suitable intra-prediction mode option 4 from the list of potentially suitable intra-prediction mode options may be retrieved as intra-prediction mode with mode number 2+((maxAB+60)%64), i.e. an intra-prediction mode having a value obtained by performing modulo arithmetic with 64 on a value obtained by adding 60 with maxAB and adding 2 with the result of the modulo arithmetic as the mode number, and a potentially suitable intra-prediction mode option 5 from the list of potentially suitable intra-prediction mode options can be extracted as an intra-prediction mode with mode number 2+(maxAB%64), i.e. an intra-prediction mode having a value obtained by performing a modulo arithmetic operation from 64 to maxAB and adding 2 to the result of the modulo arithmetic operation as the mode number. Here, maxAB may represent the greater of the mode number for the intra-prediction mode of the left adjacent block and the mode number for the intra-prediction mode of the upper adjacent block.

[722] Meanwhile, when the intra-prediction mode of the left neighbor block and the intra-prediction mode of the upper neighbor block with respect to the current block are not identical, or at least one of the mode numbers for the intra-prediction mode of the left neighbor block and the intra mode -prediction of the upper neighboring block is less than the mode number for the DC intra-prediction mode, the decoding device can determine whether the sum of the mode number for the intra-prediction mode of the left neighboring block and the mode number for the intra-prediction mode of the upper neighboring block number are equal to or greater than mode for DC-intra-prediction mode.

[723] For example, when the sum of the mode number for the intra-prediction mode of the left adjacent block and the mode number for the intra-prediction mode of the upper adjacent block is equal to or greater than the mode number for the DC-intra-prediction mode, the decoding device may retrieve a list of potentially suitable mode candidates intra-prediction of the current block, including potentially suitable intra-prediction mode options, as described below.

[724] - mpm[0]=INTRA_PLANAR

[725] - mpm[1]=maxAB

[726] - mpm[2]=INTRA_DC

[727] 2+((maxAB+61)%64)

[728] - mpm[4]=2+((maxAB-1)%64)

[729] - mpm[5]=2+((maxAB+60)%64)

[730] Thus, potential intra-prediction mode candidate 0 from the list of potential intra-prediction mode candidates may be retrieved as the planar intra-prediction mode, potential intra-prediction mode candidate 1 may be retrieved as maxAB, i.e. . Potentially suitable intra-prediction mode option 1 may be retrieved as the intra-prediction mode of the upper adjacent block when the mode number for the intra-prediction mode of the left adjacent block is less than the mode number for the intra-prediction mode of the upper adjacent block, and potential candidate intra-prediction mode option 1 -predictions can be retrieved as the intra-prediction mode of the left neighboring block when the mode number for the intra-prediction mode of the left neighboring block is greater than or equal to the mode number for the intra-prediction mode of the upper neighboring block, potentially suitable option 2 intra-prediction modes from the list of potentially of suitable intra-prediction mode candidates may be retrieved as a DC-intra-prediction mode, potential intra-prediction mode candidate 3 from the list of potential intra-prediction mode candidates may be retrieved as an intra-prediction mode having mode number 2+(( maxAB+61)%64), i.e. intra-prediction mode having the value obtained by performing modulo 64 arithmetic on the value obtained by summing 61 with maxAB and summing 2 with the result of modulo arithmetic as the mode number, potentially suitable intra-prediction mode option 4 from list of potentially suitable intra-prediction mode options can be retrieved as an intra-prediction mode having mode number 2+((maxAB-1)%64), i.e. an intra-prediction mode having a value obtained by performing modulo 64 arithmetic on a value obtained by subtracting 1 from maxAB and adding 2 to the result of the modulo arithmetic as the mode number, and potentially a suitable intra-prediction mode option 5 from the list of potentially suitable intra-prediction mode options can be retrieved as an intra-prediction mode having mode number 2+((maxAB+60)%64), i.e. an intra-prediction mode having a value obtained by performing a modulo arithmetic operation with 64 on a value obtained by adding 60 with maxAB and adding 2 with the result of a modulo arithmetic operation as the mode number.

[731] Alternatively, for example, when the above conditions are not satisfied, the decoding apparatus may retrieve a list of potential candidate intra-prediction mode candidates of the current block including potential candidate intra-prediction mode candidates, as described below.

[732] - mpm[0]=INTRA_PLANAR

[733] - mpm[1]=INTRA_DC

[734] - mpm[2]=INTRA_ANGULAR50

[735] - mpm[3]=INTRA_ANGULAR18

[736] - mpm[4]=INTRA_ANGULAR46

[737] - mpm[5]=INTRA_ANGULAR54

[738] Thus, potential intra-prediction mode candidate 0 from the list of potential intra-prediction mode candidates may be retrieved as a planar intra-prediction mode, potential intra-prediction mode candidate 1 from the list of potential intra-prediction mode candidates may be retrieved as a DC intra-prediction mode, potential intra-prediction mode candidate 2 from the list of potential intra-prediction mode candidates may be retrieved as a vertical intra-prediction mode (i.e., intra-prediction mode #50), Potentially suitable intra-prediction mode option 3 from the list of potentially suitable intra-prediction mode options may be retrieved as a horizontal intra-prediction mode (i.e., intra-prediction mode #18), potentially suitable intra-prediction mode option 4 from the list of potentially suitable intra-prediction mode options can be extracted as an intra-prediction mode mode number obtained by subtracting 4 from the mode number for the vertical intra-prediction mode, i.e. intra-prediction mode #46, potential intra-prediction mode candidate 5 from the list of potential intra-prediction mode candidates may be retrieved as the intra-prediction mode of the mode number obtained by summing 4 with the mode number for the vertical intra-prediction mode, i.e. .e. mode #54 intra-prediction. Thus, for example, when the above conditions are not satisfied, the list of potentially suitable intra-prediction mode options may include DC-intra-prediction mode, intra-prediction mode #50, intra-prediction mode #18, intra-prediction mode #46 and intra-prediction mode #54 as potentially suitable intra-prediction mode options.

[739] Meanwhile, for example, when the left neighbor block is not available, intra prediction is not applied to the left neighbor block, and the intra prediction mode of the left neighbor block corresponding to at least one of the cases in which the value of the CIIP flag the top neighbor block is not 1, and the case in which the PCM flag value of the left neighbor block is 1 can be extracted as the planar intra prediction mode. In addition, when the upper neighboring block is not available, intra prediction is not applied to the upper neighboring block, and the intra prediction mode of the left neighboring block corresponding to at least one of the cases in which the value of the CIIP flag of the upper neighboring block is not equal to 1, the case in which the PCM flag value of the upper neighboring block is 1, and the case in which the upper neighboring block is not included in the current CTU, can be extracted as a planar intra-prediction mode.

[740] Meanwhile, a list of potentially suitable intra-prediction mode options generated when the intra-prediction type is the first intra-prediction type, a list of potentially suitable intra-prediction mode options generated when the intra-prediction type is the second type intra-prediction, and the list of potentially suitable intra-prediction mode options generated when the intra-prediction type is the third intra-prediction type may be identical. Thus, an identical list of potentially suitable intra-prediction mode options can be built regardless of the intra-prediction type for the current block. A list of potentially suitable intra-prediction mode options can be constructed through an identical intra-prediction mode construction process regardless of the intra-prediction type for the current block. The process of constructing the intra-prediction mode may be identical to one of the above-described embodiments.

[741] For example, the decoder may retrieve the intra-prediction mode of the current block based on a list of potentially suitable intra-prediction mode candidates.

[742] For example, the decoder may extract the MPM flag relative to the current block. The prediction-related information may include an MPM flag. For example, the decoding apparatus may receive prediction-related information for the current block, and the prediction-related information may include an MPM flag regarding the current block. The prediction-related information may not include an MPM flag. In this case, the decoding apparatus may extract the value of MPM flag 1. The MPM flag may indicate whether or not the intra-prediction mode of the current block is one of the potentially suitable intra-prediction mode candidates from a list of potential intra-prediction mode candidates. The MPM flag may also be referred to as the "potentially suitable intra-prediction mode option flag".

[743] When the MPM flag is 1, the decoder may retrieve a candidate intra-prediction mode candidate indicated by the MPM index from the list of potential intra-prediction mode candidates as an intra-mode candidate. -predictions for the current block. The MPM index may be signaled in the form of the mpm_idx or intra_luma_mpm_idx syntax element. The MPM index may also be referred to as the "potentially suitable intra-prediction mode option index".

[744] When the MPM flag is 0, the decoding apparatus may extract the intra-prediction mode indicated by the remaining intra-prediction modes information from among the remaining intra-prediction modes as the intra-prediction mode for the current block. The remaining intra-prediction modes may represent intra-prediction modes that are not included in the potential candidate intra-prediction modes from the list of potential candidate intra-prediction modes. The above prediction-related information may include information from the remaining intra-prediction modes. The remaining intra-prediction mode information may be signaled in the form of the rem_intra_luma_pred_mode or intra_luma_mpm_remainder syntax element.

[745] For example, the intra-prediction mode of the current block may be retrieved as one of the intra-prediction modes, except for the planar intra-prediction mode and the DC-intra-prediction mode, where the intra-prediction type for the current block is retrieved as the second type intra-prediction, and retrieved as one of the intra-prediction modes, except for the DC-intra-prediction mode, where the intra-prediction type for the current block is retrieved as the third intra-prediction type.

[746] For example, the intra-prediction mode of the current block may be retrieved as one of the intra-prediction modes, except for the planar intra-prediction mode, where the intra-prediction type for the current block is retrieved as the second intra-prediction type, and retrieved into as one of the intra-prediction modes, except for the DC-intra-prediction mode, where the intra-prediction type for the current block is retrieved as the third intra-prediction type.

[747] For example, the intra-prediction mode of the current block may be retrieved as one of the intra-prediction modes, except for the planar intra-prediction mode, where the intra-prediction type for the current block is retrieved as the second intra-prediction type.

[748] For example, the decoding device may extract prediction samples of the current block based on the intra-prediction type and the intra-prediction mode.

[749] For example, when the intra-prediction type is extracted as the first intra-prediction type, the decoding device may extract at least one reference sample from among the reference samples in the intra-prediction reference lines adjacent to the current block based on intra-prediction mode, and generate discrete prediction samples of the current block based on the reference discrete sample. The reference samples may include a left top reference sample, top reference samples, and left reference samples of the current block. For example, when the size of the current block is WxH, the X-axis component of the current block's top left sample position is xN, and its Y-axis component is yN, the left reference samples may be p[xN-1][yN] - p[xN -1][2H+yN-1], the top left reference sample may be p[xN-1][yN-1], and the top reference sample may be p[xN][yN-1] - p[2W +xN-1][yN-1].

[750] For example, when an intra-prediction type is extracted as a second intra-prediction type, the decoding apparatus may extract at least one reference sample from among the reference samples in the intra-prediction reference lines that are not adjacent to the current block, based on the intra-prediction mode, and generate discrete prediction samples of the current block based on the reference discrete sample. Here, the intra-prediction reference lines may be reference lines separated from the top border and/or left border of the current block by 1, 2 or 3 sample distances.

[751] For example, when an intra-prediction type is extracted as a third intra-prediction type, the decoding apparatus may extract the ISP split type of the current block based on an ISP split flag indicating that the ISP split dials and segments the current block according to the type ISP splits to extract subblocks. The split type may be a horizontal split type or a vertical split type. For example, when the current block size is 4x4, the current block may not be segmented. For example, when the size of the current block is 4x8 and the partition type is a horizontal partition type, the current block may be segmented into two 4x4 sub-blocks. For example, when the size of the current block is 4x8 and the partition type is a vertical partition type, the current block may be segmented into two 2x8 sub-blocks. For example, when the size of the current block is 8×4 and the partition type is a horizontal partition type, the current block may be segmented into two 8×2 sub-blocks. For example, when the size of the current block is 8x4 and the partition type is a vertical partition type, the current block may be segmented into two 4x4 sub-blocks. For example, when the size of the current block is WxH (sizes other than 4x8, 8x4, and 4x4) and the partition type is a horizontal partition type, the current block may be segmented into four WxH/4 sub-blocks. For example, when the current block size is WxH and the partition type is a vertical partition type, the current block may be segmented into four W/4xH sub-blocks. Thereafter, the decoding apparatus may perform intra-prediction on the sub-blocks to generate a discrete prediction sample. Thus, the decoding device can extract at least one of the reference samples in the intra-prediction reference lines of each sub-block relative to the current block based on the intra-prediction mode, and generate a prediction sample based on the reference sample. The intra-prediction reference lines of each sub-block may be reference lines adjacent to each sub-block.

[752] For example, when the intra-prediction mode of the current block is retrieved as the DC-intra-prediction mode, the current block is a square block, the size of the current block is WxH, the X-axis component and the Y-axis component of the top left position of the current block are equal 0, the DC value may be retrieved based on the reference sample at coordinates (0,-refIdx-1) to the reference sample at coordinates (W-1,-refIdx-1) in the upper intra-prediction reference line indicated by the reference index line of the current block, and a reference sample with coordinates (-refIdx-1, 0) to a reference sample with coordinates (-refIdx-1, H-1) in the left intra-prediction reference line indicated by the reference line index. The prediction sample of the current block may be retrieved as a DC value.

[753] For example, when the intra-prediction mode of the current block is retrieved as the DC-intra-prediction mode, the current block is a non-square block whose width is greater than its height, the size of the current block is WxH, an X-axis component, and a Y-axis component the top left position of the current block is 0, the DC value can be retrieved based on the reference sample with coordinates (0,-refIdx-1) to the reference sample with coordinates (W-1,-refIdx-1) in the upper reference line of the intra- prediction indicated by the reference line index of the current block. The prediction sample of the current block may be retrieved as a DC value.

[754] For example, when the intra-prediction mode of the current block is retrieved as the DC-intra-prediction mode, the current block is a non-square block whose height is greater than its width, the size of the current block is WxH, an X-axis component, and a Y-axis component the top left position of the current block is 0, the DC value can be retrieved based on the reference sample with coordinates (-refIdx-1, 0) to the reference sample with coordinates (-refIdx-1, H-1) in the left reference line of the intra- prediction indicated by the reference line index of the current block. The prediction sample of the current block may be retrieved as a DC value.

[755] For example, when the intra prediction mode of the current block is retrieved as a planar intra prediction mode, the size of the current block is WxH, the X-axis component and the Y-axis component of the top left position of the current block are 0, the prediction sample may be retrieved at based on a reference sample with coordinates (W-1, -refIdx-1) and a reference sample with coordinates (-refIdx-1, H-1) in the intra-prediction reference line indicated by the reference line index of the current block.

[756] In addition, for example, the decoding apparatus may extract a residual sample of the current block based on the residual information for the current block. The image information may include residual information. The residual information may include a conversion factor for the residual sample. The decoding apparatus may extract a residual sample (or an array of residual samples) for the current block based on the residual information.

[757] Then, for example, the decoding device can generate a reconstructed sample of the current block based on the prediction sample and the residual sample. For example, the decoding device may generate a reconstructed sample by adding the residual sample to the prediction sample.

[758] The decoding apparatus may then apply an in-loop filtering procedure, such as a deblocking and/or SAO filtering procedure, to the recovered sample (i.e., the reconstructed frame) to improve the subjective/objective quality of the frames as needed. , as described above.

[759] FIG. 24 schematically illustrates a decoding apparatus that implements an image decoding method according to the present disclosure. The method disclosed in FIG. 23 may be performed by the decoding apparatus illustrated in FIG. 24. In particular, for example, the entropy decoder of the decoding apparatus of FIG. 24 can perform S2300 of FIG. 23, and the decoding device prediction module of FIG. 24 can perform S2310 of FIG. 23. In addition, although not illustrated, the process of obtaining image information including residual information regarding the current block through the bitstream may be performed by the entropy decoder of the decoding apparatus of FIG. 24, and the process of extracting a residual sample relative to the current block based on the residual information can be performed by the residual processor of the decoding apparatus of FIG. 24.

[760] According to the above-described present disclosure, it is possible to reduce hardware and software implementation complexity by using a unified process for constructing lists of intra-prediction modes for intra-prediction types.

[761] In addition, according to the present disclosure, it is possible to reduce the dependence on the intra-prediction type by using a unified process for constructing intra-prediction mode lists for intra-prediction types to improve intra-prediction encoding efficiency.

[762] In addition, according to the present disclosure, it is possible to improve intra-prediction coding efficiency by extracting a reference sample sample used when MRL is applied and the intra-prediction mode is extracted as a DC-intra-prediction mode based on the reference frame index.

[763] In addition, according to the present disclosure, it is possible to improve intra-prediction coding efficiency by extracting a reference sample sample used when MRL is applied and the intra-prediction mode is extracted as a DC-intra-prediction mode based on the reference frame index and shape current block.

[764] In addition, according to the present disclosure, it is possible to improve intra-prediction coding efficiency by extracting a reference sample sample used when MRL is applied and the intra-prediction mode is extracted as a planar intra-prediction mode based on the reference frame index.

[765] In the above-described embodiment, the methods are described on the basis of a flowchart having a sequence of steps or blocks. The present disclosure is not limited to the order of the above steps or blocks. Some stages or blocks may occur simultaneously or in a different order from other stages or blocks as described above. Additionally, those skilled in the art will understand that the steps shown in the above flowchart are not exhaustive and other steps may be included or one or more steps in the flowchart may be deleted without affecting scope of this disclosure.

[766] The embodiments described in this detailed description may be implemented through implementation in a processor, in a microprocessor, in a controller, or in a chip. For example, the functional modules shown in each drawing may be implemented through implementation on a computer, a processor, a microprocessor, a controller, or a chip. In this case, implementation information (eg, information regarding instructions) or algorithm may be stored on a digital storage medium.

[767] In addition, the decoding device and the encoding device to which the present disclosure applies may be included in a multimedia broadcasting device, a mobile communication terminal, a home theater system video device, a digital cinema system video device, a surveillance camera, a video chat device, a real-time communications, e.g., video communications, mobile streaming device, storage medium, video recording camera, VoD service device, over-the-top (OTT) video device, Internet streaming service device, 3D video device, video teleconferencing device , a transport user equipment (eg, a user equipment in a vehicle, a user equipment in an aircraft, a user equipment in a marine vessel, etc.) and a medical video device, and can be used to process video signals and data signals. For example, an over-the-top (OTT) video device may include a game console, Blu-ray player, Internet-enabled television, home theater system, smartphone, tablet PC, digital video recorder (DVR), etc.

[768] Additionally, the processing method to which the present disclosure applies may be formed in the form of a program to be executed by a computer and may be stored on a computer-readable recording medium. Multimedia data having a data structure according to the present disclosure may also be stored on computer-readable recording media. Computer readable recording media includes all types of storage devices on which data readable by a computer system is stored. Computer readable recording media, for example, may include BD, universal serial bus (USB), ROM, PROM, EPROM, EEPROM, RAM, CD-ROM, magnetic tape, floppy disk, and optical storage device. In addition, computer-readable recording media include media implemented in the form of carrier waves (eg, as transmission over the Internet). In addition, the bitstream generated by the encoding method may be stored in a computer-readable recording medium or may be transmitted over wired/wireless communication networks.

[769] In addition, embodiments of the present disclosure may be implemented with a computer program product according to program codes, and program codes may be executed on a computer by embodiments of the present disclosure. The program codes may be stored on a medium that can be read by a computer.

[770] FIG. 25 illustrates a block diagram of a content streaming system to which the present disclosure applies.

[771] A content streaming system to which the embodiment(s) of the present disclosure applies may generally include an encoding server, a streaming server, a web server, a media storage, a user device, and a media input device.

[772] The encoding server compresses content input from media input devices such as a smartphone, camera, video recorder, etc. Into digital data to form a bit stream and transmit the bit stream to the streaming server. As another example, when media input devices such as smartphones, cameras, video recorders, etc. directly generate a bit stream, the encoding server may be omitted.

[773] The bitstream may be generated by an encoding method or a bitstream generation method to which the embodiment(s) of the present disclosure applies, and the streaming server may temporarily store the bitstream while transmitting or receiving the bitstream.

[774] The streaming server transmits media data to the user device based on the user's request through the web server, and the web server serves as a medium for informing the user regarding the service. When a user requests a required service from a web server, the web server delivers it to the streaming server and the streaming server transmits the media data to the user. In this case, the content streaming system may include a separate control server. In this case, the control server serves to manage the command/response between devices in the content streaming system.

[775] The streaming server may receive content from a media storage and/or encoding server. For example, when content is received from an encoding server, the content may be received in real time. In this case, in order to provide a smooth streaming service, the streaming server may store the bit stream for a predetermined time.

[776] Examples of a user device may include a mobile phone, a smartphone, a laptop computer, a digital broadcast terminal, a personal digital assistant (PDA), a portable media player (PMP), a navigation device, a tablet PC, tablet PCs, ultrabooks, wearable devices (e.g. smart watches, smart glasses, head-mounted displays (HMDs)), digital TVs, desktop computers, digital signage system, etc. Each server in a content streaming system may operate as a distributed server, in which case data received from each server may be distributed.

[777] The claims of the present disclosure may be combined in various ways. For example, the technical features of the process claims of the present disclosure may be combined and implemented as an apparatus, and the technical features of the apparatus claims of the present disclosure may be combined and implemented as a method. In addition, the technical process requirement features and the technical features of the device claim of the present disclosure may be combined and implemented as the device and process requirement technical features, and the technical features of the device claim of the present disclosure may be combined and implemented as a method.

Provision 1. A method for decoding an image, carried out by means of a decoding device, containing the steps of:

receiving image information including prediction-related information for the current block; And

form a reconstructed discrete sample of the current block based on image information,

in this case, the formation of a reconstructed discrete sample contains stages in which:

extracting an intra-prediction type for the current block from the intra-prediction types based on the prediction-related information;

constructing a list of potentially suitable options for intra-prediction modes of the current block based on the intra-prediction modes of neighboring blocks relative to the current block,

wherein the intra-prediction types include a first intra-prediction type based on an intra-prediction reference line adjacent to the current block, a second intra-prediction type based on an intra-prediction reference line not adjacent to the current block, and a third intra-prediction type -prediction to which the intra-subsegment (ISP) mode is applied, and

wherein a list of potentially suitable intra-prediction mode options built for the case in which the intra-prediction type is the first intra-prediction type, a list of potentially suitable intra-prediction mode options built for the case in which the intra-prediction type is the second intra-prediction type, and the list of potentially suitable intra-prediction mode options constructed for the case in which the intra-prediction type is the third intra-prediction type, are identical.

Position 2. A method for decoding an image according to Position 1, in which the formation of a reconstructed discrete sample contains the stages of:

extracting the intra-prediction mode of the current block based on the list of potentially suitable intra-prediction mode options;

extracting a prediction sample of the current block based on the intra-prediction type and the intra-prediction mode;

extracting a residual sample of the current block based on the residual information for the current block; And

forming a reconstructed discrete sample based on the prediction discrete sample and the residual discrete sample,

wherein the image information includes residual information.

Regulation 3. Image decoding method according to Regulation 1,

in which the neighboring blocks include the left neighboring block and the upper neighboring block relative to the current block,

wherein, when the intra-prediction mode of the left adjacent block and the intra-prediction mode of the upper adjacent block are identical, and the mode number for the intra-prediction mode of the left adjacent block is greater than the mode number for the DC-intra-prediction mode, a list of potentially suitable intra-mode candidates -prediction includes the intra-prediction mode of the left adjacent block, the intra-prediction mode with mode number 2+((candIntraPredModeA+61)%64), the intra-prediction mode with mode number 2+((candIntraPredModeA-1)%64) and an intra-prediction mode with mode number 2+((candIntraPredModeA+60)%64) as potentially suitable intra-prediction mode options, and

wherein candIntraPredModeA represents the mode number for the intra-prediction mode of the left adjacent block.

Regulation 4. Image decoding method according to Regulation 3,

wherein, when the intra-prediction mode of the left adjacent block and the intra-prediction mode of the upper adjacent block are not identical, and the mode number for the intra-prediction mode of the left adjacent block and the mode number for the intra-prediction mode of the upper adjacent block exceed the mode number for the mode DC intra-prediction, the list of potentially suitable intra-prediction mode candidates includes the left neighbor block intra-prediction mode and the top neighbor block intra-prediction mode as potentially suitable intra-prediction mode candidates,

wherein potential candidates for the remaining intra-prediction modes from the list of potential candidates for intra-prediction modes are retrieved based on the difference between the larger value and the smaller value among the mode number for the intra-prediction mode of the left adjacent block and the mode number for the intra-prediction mode of the upper neighbor block.

Statement 5. An image decoding method according to Position 3, in which when intra prediction is not applied to the left neighbor block, the value of the combined inter and intra prediction (CIIP) flag of the left neighbor block is not 1, the intra prediction mode of the left neighbor block is extracted as a planar intra-prediction mode.

Regulation 6. Image decoding method according to Regulation 1,

in which, when the intra-prediction mode of the current block is retrieved as the DC-intra-prediction mode, the current block is a square block, the size of the current block is WxH, the X-axis component and the Y-axis component of the top left position of the current block are 0, The DC value is retrieved based on the reference sample at coordinates (0,-refIdx-1) to the reference sample at coordinates (W-1,-refIdx-1) in the intra-prediction reference line indicated by the reference line index of the current block, and a reference sample with coordinates (-refIdx-1, 0) to a reference sample with coordinates (-refIdx-1, H-1) in the intra-prediction reference line, and the prediction sample is extracted as a DC value,

wherein refIdx is a reference line index value, and the prediction-related information includes the reference line index.

Regulation 7. Image decoding method according to Regulation 1,

in which, when the intra-prediction mode of the current block is retrieved as the DC-intra-prediction mode, the current block is a non-square block whose width is greater than its height, the size of the current block is WxH, the X-axis component and the Y-axis component are left top current block positions are 0, the DC value is retrieved based on the reference sample with coordinates (0,-refIdx-1) to the reference sample with coordinates (W-1,-refIdx-1) in the intra-prediction reference line specified by reference line index of the current block, and the prediction sample is extracted as a DC value,

wherein refIdx is a reference line index value, and the prediction-related information includes the reference line index.

Regulation 8. Image decoding method according to Regulation 1,

in which, when the intra-prediction mode of the current block is retrieved as the DC-intra-prediction mode, the current block is a non-square block whose height is greater than its width, the size of the current block is WxH, the X-axis component and the Y-axis component are left top current block positions are 0, the DC value is retrieved based on the reference sample with coordinates (-refIdx-1, 0) to the reference sample with coordinates (-refIdx-1, H-1) in the intra-prediction reference line specified by reference line index of the current block, and the prediction sample is extracted as a DC value,

wherein refIdx is a reference line index value, and the prediction-related information includes the reference line index.

Regulation 9. Image decoding method according to Regulation 1,

in which, when the intra-prediction mode of the current block is extracted as a planar intra-prediction mode, the size of the current block is WxH, the X-axis component and the Y-axis component of the top left position of the current block are 0, the prediction sample is extracted based on the reference sample a sample with coordinates (W-1, -refIdx-1) and a reference discrete sample with coordinates (-refIdx-1, H-1) in the intra-prediction reference line indicated by the reference line index of the current block,

wherein refIdx is a reference line index value, and the prediction-related information includes the reference line index.

Statement 10. An image decoding method according to Statement 1, in which extracting an intra-prediction type for a current block from the intra-prediction types based on the prediction-related information comprises:

determining whether the intra-prediction type for the current block is a second intra-prediction type based on the reference line index of the current block,

wherein the prediction-related information includes a reference line index, and

wherein, when the reference line index indicates a reference line not adjacent to the current block, the reference line not adjacent to the current block is retrieved as the intra-prediction reference line of the current block, and the second intra-prediction type is retrieved as the intra-prediction type for the current block.

Provision 11. An image decoding method according to Proposition 10, in which extracting an intra-prediction type for a current block from intra-prediction types based on prediction-related information comprises:

determining whether the intra-prediction type for the current block is a third intra-prediction type based on the intra-subsegment-based (ISP) mode flag when the intra-prediction type for the current block is not a second intra-prediction type,

wherein the prediction-related information includes an ISP flag,

wherein the third intra-prediction type is retrieved as the intra-prediction type for the current block when the ISP flag indicates that the third intra-prediction type is applied, and

wherein the first intra-prediction type is retrieved as the intra-prediction type for the current block when the ISP flag indicates that the third intra-prediction type is not applied.

Clause 12. An image encoding method carried out by means of an encoding device, comprising the steps of:

forming a restored discrete sample of the current block;

generating prediction-related information for the current block; And

encode image information including prediction-related information,

in this case, the formation of a reconstructed discrete sample of the current block contains stages in which:

determining an intra-prediction type for the current block from the intra-prediction types;

constructing a list of potentially suitable options for intra-prediction modes of the current block based on the intra-prediction modes of neighboring blocks relative to the current block,

wherein the intra-prediction types include a first type of intra-prediction using an intra-prediction reference line adjacent to the current block, a second type of intra-prediction using an intra-prediction reference line not adjacent to the current block, and a third type of intra-prediction -predictions to which the intra-subsegment-based (ISP) mode is applied,

wherein a list of potentially suitable intra-prediction mode options built for the case in which the intra-prediction type is the first intra-prediction type, a list of potentially suitable intra-prediction mode options built for the case in which the intra-prediction type is the second intra-prediction type, and the list of potentially suitable intra-prediction mode options constructed for the case in which the intra-prediction type is the third intra-prediction type, are identical.

Provision 13. An image encoding method according to Provision 12, in which the formation of a reconstructed discrete sample contains the stages of:

extracting the intra-prediction mode of the current block based on the list of potentially suitable intra-prediction mode options;

extracting a prediction sample of the current block based on the intra-prediction type and the intra-prediction mode;

extracting a residual sample of the current block based on the prediction sample; And

forming a reconstructed discrete sample based on the prediction discrete sample and the residual discrete sample.

Regulation 14. Image encoding method according to Regulation 12,

in which the neighboring blocks include the left neighboring block and the upper neighboring block relative to the current block,

wherein, when the intra-prediction mode of the left adjacent block and the intra-prediction mode of the upper adjacent block are identical, and the mode number for the intra-prediction mode of the left adjacent block is greater than the mode number for the DC-intra-prediction mode, a list of potentially suitable intra-mode candidates -prediction includes the intra-prediction mode of the left adjacent block, the intra-prediction mode with mode number 2+((candIntraPredModeA+61)%64), the intra-prediction mode with mode number 2+((candIntraPredModeA-1)%64) and an intra-prediction mode with mode number 2+((candIntraPredModeA+60)%64) as potentially suitable intra-prediction mode options, and

wherein candIntraPredModeA represents the mode number for the intra-prediction mode of the left adjacent block.

Statement 15: A non-transitory computer-readable storage medium storing a bit stream including image information instructing a decoding device to perform the following steps:

receiving image information including prediction-related information for the current block; And

formation of a reconstructed discrete sample of the current block based on image information,

in this case, the formation of a reconstructed discrete sample contains:

extracting an intra-prediction type for the current block from the intra-prediction types based on the prediction-related information;

constructing a list of potentially suitable options for intra-prediction modes of the current block based on the intra-prediction modes of neighboring blocks relative to the current block,

wherein the intra-prediction types include a first intra-prediction type based on an intra-prediction reference line adjacent to the current block, a second intra-prediction type based on an intra-prediction reference line not adjacent to the current block, and a third intra-prediction type -prediction to which the intra-subsegment (ISP) mode is applied, and

wherein a list of potentially suitable intra-prediction mode options built for the case in which the intra-prediction type is the first intra-prediction type, a list of potentially suitable intra-prediction mode options built for the case in which the intra-prediction type is the second intra-prediction type, and the list of potentially suitable intra-prediction mode options constructed for the case in which the intra-prediction type is the third intra-prediction type, are identical.

Claims (46)

1. A decoding device for decoding images, comprising: memory; And at least one processor coupled to the memory, wherein the at least one processor is configured to: receive image information including prediction-related information for the current block, and generate a reconstructed discrete sample of the current block based on image information, in this case, the restored discrete sample is formed on the basis of: obtaining an intra-prediction type for the current block from the intra-prediction types based on the prediction-related information, constructing a list of potentially suitable options for intra-prediction modes of the current block, including a DC-intra-prediction mode, based on the intra-prediction modes of neighboring blocks relative to the current block; obtaining the intra-prediction mode of the current block based on a list of potentially suitable intra-prediction mode options and obtaining a discrete prediction sample of the current block based on the intra-prediction mode, wherein the intra-prediction types include a first intra-prediction type based on an intra-prediction reference line adjacent to the current block, a second intra-prediction type based on an intra-prediction reference line not adjacent to the current block, and a third intra-prediction type -predictions to which the intra-subsegment-based (ISP) mode is applied, wherein the intra-prediction type for the current block is obtained as a second intra-prediction type based on the prediction-related information, wherein a list of potentially suitable intra-prediction mode options built for the case in which the intra-prediction type is the first intra-prediction type, a list of potentially suitable intra-prediction mode options built for the case in which the intra-prediction type is the second intra-prediction type, and the list of potentially suitable intra-prediction mode options constructed for the case in which the intra-prediction type is the third intra-prediction type, are identical, wherein based on the intra-prediction mode of the current block obtained as the DC-intra-prediction mode, and the width of the current block equal to the height of the current block, the DC value is obtained based on (i) reference discrete samples located at coordinates from (0 , -refIdx-1) to (W-1, -refIdx-1) in the intra-prediction reference line indicated by the reference line index of the current block, and (ii) reference samples located at coordinates from (-refIdx-1, 0) to (-refIdx-1, H-1) in the intra-prediction reference line, and the prediction sample is obtained as a DC value, wherein based on the intra-prediction mode of the current block obtained as the DC-intra-prediction mode, and the width of the current block exceeding the height of the current block, the DC value is obtained based on the reference discrete samples located at coordinates from (0, -refIdx -1) to (W-1, -refIdx-1) in the intra-prediction reference line indicated by the reference line index of the current block, and the prediction sample is obtained as a DC value, wherein based on the intra-prediction mode of the current block obtained as the DC-intra-prediction mode, and the height of the current block exceeding the width of the current block, the DC value is obtained based on the reference discrete samples located at coordinates from (-refIdx-1 , 0) to (-refIdx-1, H-1) in the intra-prediction reference line indicated by the reference line index of the current block, and the prediction sample is obtained as a DC value, and wherein refIdx represents the reference line index value of the current block, W represents the width of the current block, H represents the height of the current block, and the prediction-related information includes the reference line index. 2. An encoding device for encoding images, comprising: memory; And at least one processor coupled to the memory, wherein the at least one processor is configured to: generate a restored discrete sample of the current block; generate prediction-related information for the current block; And encode image information including prediction-related information, in this case, the restored discrete sample of the current block is formed based on: determining the intra-prediction type for the current block from the intra-prediction types, constructing a list of potentially suitable options for intra-prediction modes of the current block, including the DC-intra-prediction mode, based on the intra-prediction modes of neighboring blocks relative to the current block, obtaining the intra-prediction mode of the current block based on a list of potentially suitable intra-prediction mode options and obtaining a discrete prediction sample of the current block based on the intra-prediction mode, wherein the intra-prediction types include a first type of intra-prediction using an intra-prediction reference line adjacent to the current block, a second type of intra-prediction using an intra-prediction reference line not adjacent to the current block, and a third type of intra-prediction -predictions to which the intra-subsegment-based (ISP) mode is applied, in this case, the intra-prediction type for the current block is defined as the second intra-prediction type, wherein a list of potentially suitable intra-prediction mode options built for the case in which the intra-prediction type is the first intra-prediction type, a list of potentially suitable intra-prediction mode options built for the case in which the intra-prediction type is the second intra-prediction type, and the list of potentially suitable intra-prediction mode options constructed for the case in which the intra-prediction type is the third intra-prediction type, are identical, wherein based on the intra-prediction mode of the current block obtained as the DC-intra-prediction mode, and the width of the current block equal to the height of the current block, the DC value is obtained based on (i) reference discrete samples located at coordinates from (0 , -refIdx-1) to (W-1, -refIdx-1) in the intra-prediction reference line indicated by the reference line index of the current block, and (ii) reference samples located at coordinates from (-refIdx-1, 0) to (-refIdx-1, H-1) in the intra-prediction reference line, and the prediction sample is obtained as a DC value, wherein based on the intra-prediction mode of the current block obtained as the DC-intra-prediction mode, and the width of the current block exceeding the height of the current block, the DC value is obtained based on the reference discrete samples located at coordinates from (0, -refIdx -1) to (W-1, -refIdx-1) in the intra-prediction reference line indicated by the reference line index of the current block, and the prediction sample is obtained as a DC value, wherein based on the intra-prediction mode of the current block obtained as the DC-intra-prediction mode, and the height of the current block exceeding the width of the current block, the DC value is obtained based on the reference discrete samples located at coordinates from (-refIdx-1 , 0) to (-refIdx-1, H-1) in the intra-prediction reference line indicated by the reference line index of the current block, and the prediction sample is obtained as a DC value, and wherein refIdx represents the reference line index value of the current block, W represents the width of the current block, H represents the height of the current block, and the prediction-related information includes the reference line index. 3. An image data transmission device, comprising: at least one processor configured to obtain a bit stream for an image, wherein the bit stream is generated based on generating a reconstructed sample of a current block, generating prediction-related information for the current block, and generating a bit stream by encoding image information including associated with predictive information; And a transmitter configured to transmit data comprising a stream of bits, in this case, the restored discrete sample of the current block is formed on the basis of: determining the type of intra-prediction for the current block from the types of intra-prediction; constructing a list of potentially suitable options for intra-prediction modes of the current block, including a DC-intra-prediction mode, based on the intra-prediction modes of neighboring blocks relative to the current block; obtaining the intra-prediction mode of the current block based on the list of potentially suitable intra-prediction mode options; and obtaining a prediction sample of the current block based on the intra-prediction mode, wherein the intra-prediction types include a first type of intra-prediction using an intra-prediction reference line adjacent to the current block, a second type of intra-prediction using an intra-prediction reference line not adjacent to the current block, and a third type of intra-prediction -predictions to which the intra-subsegment-based (ISP) mode is applied, in this case, the intra-prediction type for the current block is defined as the second intra-prediction type, wherein a list of potentially suitable intra-prediction mode options built for the case in which the intra-prediction type is the first intra-prediction type, a list of potentially suitable intra-prediction mode options built for the case in which the intra-prediction type is the second intra-prediction type, and the list of potentially suitable intra-prediction mode options constructed for the case in which the intra-prediction type is the third intra-prediction type, are identical, wherein based on the intra-prediction mode of the current block obtained as the DC-intra-prediction mode, and the width of the current block equal to the height of the current block, the DC value is obtained based on (i) reference discrete samples located at coordinates from (0 , -refIdx-1) to (W-1, -refIdx-1) in the intra-prediction reference line indicated by the reference line index of the current block, and (ii) reference samples located at coordinates from (-refIdx-1, 0) to (-refIdx-1, H-1) in the intra-prediction reference line, and the prediction sample is obtained as a DC value, wherein based on the intra-prediction mode of the current block obtained as the DC-intra-prediction mode, and the width of the current block exceeding the height of the current block, the DC value is obtained based on the reference discrete samples located at coordinates from (0, -refIdx -1) to (W-1, -refIdx-1) in the intra-prediction reference line indicated by the reference line index of the current block, and the prediction sample is obtained as a DC value, wherein based on the intra-prediction mode of the current block obtained as the DC-intra-prediction mode, and the height of the current block exceeding the width of the current block, the DC value is obtained based on the reference discrete samples located at coordinates from (-refIdx-1 , 0) to (-refIdx-1, H-1) in the intra-prediction reference line indicated by the reference line index of the current block, and the prediction sample is obtained as a DC value, and wherein refIdx represents the reference line index value of the current block, W represents the width of the current block, H represents the height of the current block, and the prediction-related information includes the reference line index.