Intra prediction-based image encoding / decoding method and device, and recording medium for storing bitstream

Abstract

Provided are an image encoding / decoding method and device. The image decoding method, according to the present disclosure, comprises the steps of: on the basis of intra prediction information of neighboring blocks of the current block, acquiring one or more candidate intra prediction information; on the basis of the one or more candidate intra prediction information, configuring an intra prediction candidate list; acquiring an intra prediction candidate index representing one candidate intra prediction information included in the intra prediction candidate list; and generating a prediction block of the current block by performing intra prediction on the basis of the candidate intra prediction information indicated by the intra prediction candidate index, wherein the candidate intra prediction information may include at least one among template based intra mode derivation (TIMD) information, decoder side intra mode derivation (DIMD) information or linear model information, linear interpolation intra prediction (LIP) information, position dependent intra prediction (PDPC) information, multi reference line (MRL) information, template-based multiple reference line (TMRL) information, intra sub-partition (ISP) information, matrix-based intra prediction (MIP) information, interpolation filter information, mode dependent intra smoothing (MDIS) information, combined inter and intra prediction (CIIP) information, spatial geometric partition mode (SGPM) information, template matching intra prediction (intraTMP) information, intra prediction directional mode information, extended planar information, intra prediction fusion information, neighboring reference sample characteristics information or intra block copy (IBC) information.

Description

Video encoding / decoding method and device based on intra prediction and recording medium for storing bitstream

[0001] The present disclosure relates to a video encoding / decoding method, a device, and a recording medium for storing a bitstream, and more particularly, to a video encoding / decoding method and device based on intra prediction, and a recording medium for storing a bitstream generated by the video encoding method / device of the present disclosure.

[0002] Recently, demand for high-resolution, high-quality images, such as HD (High Definition) and UHD (Ultra High Definition) images, has been increasing across various fields. As image data becomes higher resolution and higher quality, the amount of information transmitted, or bits, increases relative to conventional image data. This increase in information or bits transmitted leads to increased transmission and storage costs.

[0003] Accordingly, a highly efficient image compression technology is required to effectively transmit, store, and play high-resolution, high-quality image information.

[0004] The present disclosure aims to provide a video encoding / decoding method and device with improved encoding / decoding efficiency.

[0005] In addition, the present disclosure aims to provide an image encoding / decoding method and device that effectively performs intra prediction.

[0006] In addition, the present disclosure aims to provide a video encoding / decoding method and device that effectively generates an intra prediction candidate list.

[0007] In addition, the present disclosure aims to provide a video encoding / decoding method and device including various prediction modes when generating an intra prediction candidate list.

[0008] In addition, the present disclosure aims to provide a non-transitory computer-readable recording medium that stores a bitstream generated by an image encoding method or device according to the present disclosure.

[0009] In addition, the present disclosure aims to provide a non-transitory computer-readable recording medium that stores a bitstream received and decoded by an image decoding device according to the present disclosure and used for restoring an image.

[0010] In addition, the present disclosure aims to provide a method for transmitting a bitstream generated by an image encoding method or device according to the present disclosure.

[0011] The technical problems to be achieved in the present disclosure are not limited to the technical problems mentioned above, and other technical problems not mentioned can be clearly understood by a person having ordinary skill in the technical field to which the present disclosure belongs from the description below.

[0012] According to one embodiment of the present disclosure, there is provided an image decoding method performed by an image decoding device, comprising: a step of obtaining one or more candidate intra prediction information based on intra prediction information of surrounding blocks of a current block; a step of constructing an intra prediction candidate list based on the one or more candidate intra prediction information; a step of obtaining an intra prediction candidate index indicating one candidate intra prediction information included in the intra prediction candidate list; and a step of generating a prediction block of the current block by performing intra prediction based on the candidate intra prediction information indicated by the intra prediction candidate index, wherein the candidate intra prediction information is selected from the group consisting of Template-based intra mode derivation (TIMD) information, Decoder-side intra mode derivation (DIMD) information, linear model information, Linear interpolation intra prediction (LIP) information, Position-dependent intra prediction (PDPC) information, Multi-reference line (MRL) information, Template-based multiple reference line (TMRL) information, Intra sub-partition (ISP) information, Matrix-based intra prediction (MIP) information, Interpolation filter information, MDIS (mode dependent intra smoothing) information, CIIP (combined inter and intra prediction) information, SGPM (spatial geometric partition mode) information, intraTMP (template matching intra prediction) information, intra-screen prediction directionality mode information, extended planar information, intra-prediction fusion information,It may include at least one of surrounding reference sample characteristic information or intra block copy (IBC) information.

[0013] According to one embodiment of the present disclosure, the surrounding blocks may be determined based on one of template matching, bi-lateral matching, or sum of absolute transformed differences (SATD).

[0014] According to one embodiment of the present disclosure, the intra prediction candidate index may be determined based on one of template matching, bi-lateral matching, or sum of absolute transformed differences (SATD).

[0015] According to one embodiment of the present disclosure, the order of the candidate intra prediction information included in the intra prediction candidate list can be re-ordered based on one of template matching or bidirectional matching.

[0016] According to one embodiment of the present disclosure, the candidate intra prediction information may include information regarding whether the candidate intra prediction mode is applied.

[0017] According to one embodiment of the present disclosure, the candidate intra prediction information may further include additional information used in applying the corresponding candidate intra prediction mode.

[0018] According to one embodiment of the present disclosure, the prediction block may be generated based on at least one of the candidate intra prediction mode or the additional information.

[0019] According to one embodiment of the present disclosure, the number of candidate intra prediction information included in the intra prediction candidate list may be determined based on at least one of the size of the current block, the position of a sub-block within the current block, statistical characteristics of the surrounding blocks, or whether a secondary transform is used for the current block.

[0020] According to one embodiment of the present disclosure, the acquisition order of the neighboring blocks may be determined based on at least one of the size of the current block, the position of a sub-block within the current block, statistical characteristics of the neighboring blocks, or whether a secondary transform is used for the current block.

[0021] According to one embodiment of the present disclosure, the positions of the surrounding blocks may be determined based on at least one of the size of the current block, the positions of sub-blocks within the current block, statistical characteristics of the surrounding blocks, or whether a secondary transform is used for the current block.

[0022] According to one embodiment of the present disclosure, based on the current block being a chroma block, the intra prediction candidate list can be constructed based on first candidate intra prediction information of a surrounding block of the chroma block and second candidate intra prediction information of a luma block corresponding to the chroma block.

[0023] According to one embodiment of the present disclosure, based on the second candidate intra prediction information including the linear model information, the intra prediction candidate list may include at least one of a first intra prediction candidate list composed of the linear model information or a second intra prediction candidate list composed of information other than the linear model information.

[0024] According to one embodiment of the present disclosure, a video encoding method performed by a video encoding apparatus comprises the steps of: obtaining one or more candidate intra prediction information based on intra prediction information of surrounding blocks of a current block; constructing an intra prediction candidate list based on the one or more candidate intra prediction information; generating a prediction block of a current block based on one candidate intra prediction information included in the intra prediction candidate list; and encoding an intra prediction candidate index indicating the one candidate intra prediction information, wherein the candidate intra prediction information is selected from the group consisting of Template-based intra mode derivation (TIMD) information, Decoder-side intra mode derivation (DIMD) information, linear model information, Linear interpolation intra prediction (LIP) information, Position-dependent intra prediction (PDPC) information, Multi-reference line (MRL) information, Template-based multiple reference line (TMRL) information, Intra-subpartition (ISP) information, Matrix-based intra-prediction (MIP) information, Interpolation filter information, Mode-dependent intra-smoothing (MDIS) information. It may include at least one of combined inter and intra prediction (CIIP) information, spatial geometric partition mode (SGPM) information, intra TMP (template matching intra prediction) information, intra-screen prediction directionality mode information, extended planar information, intra-prediction fusion information, surrounding reference sample characteristic information, or intra block copy (IBC) information.

[0025] According to one embodiment of the present disclosure, there may be a computer-readable recording medium storing a bitstream generated by an image encoding method.

[0026] According to one embodiment of the present disclosure, a method for transmitting a bitstream generated by an image encoding method, the image encoding method comprises the steps of: obtaining one or more candidate intra prediction information based on intra prediction information of surrounding blocks of a current block; constructing an intra prediction candidate list based on the one or more candidate intra prediction information; generating a prediction block of a current block based on one candidate intra prediction information included in the intra prediction candidate list; and encoding an intra prediction candidate index indicating the one candidate intra prediction information, wherein the candidate intra prediction information is selected from the group consisting of Template-based intra mode derivation (TIMD) information, Decoder-side intra mode derivation (DIMD) information, linear model information, Linear interpolation intra prediction (LIP) information, Position-dependent intra prediction (PDPC) information, Multi-reference line (MRL) information, Template-based multiple reference line (TMRL) information, Intra-subpartition (ISP) information, Matrix-based intra-prediction (MIP) information, Interpolation filter information, Mode-dependent intra-prediction (MDIS) information, smoothing) information, combined inter and intra prediction (CIIP) information, spatial geometric partition mode (SGPM) information, intra-TMP (template matching intra prediction) information, intra-screen prediction directionality mode information, extended planar information, intra-prediction fusion information,It may include at least one of surrounding reference sample characteristic information or intra block copy (IBC) information.

[0027] According to the present disclosure, a video encoding / decoding method and device with improved encoding / decoding efficiency can be provided.

[0028] In addition, according to the present disclosure, an image encoding / decoding method and device that effectively perform intra prediction can be provided.

[0029] In addition, according to the present disclosure, a video encoding / decoding method and device for effectively generating an intra prediction candidate list can be provided.

[0030] In addition, according to the present disclosure, a video encoding / decoding method and device including various prediction modes when generating an intra prediction candidate list can be provided.

[0031] In addition, according to the present disclosure, a non-transitory computer-readable recording medium for storing a bitstream generated by an image encoding method or device according to the present disclosure can be provided.

[0032] In addition, according to the present disclosure, a non-transitory computer-readable recording medium can be provided that stores a bitstream received and decoded by an image decoding device according to the present disclosure and used for restoring an image.

[0033] Additionally, according to the present disclosure, a method for transmitting a bitstream generated by an image encoding method or device according to the present disclosure can be provided.

[0034] The effects that can be obtained from the present disclosure are not limited to the effects mentioned above, and other effects that are not mentioned will be clearly understood by a person having ordinary skill in the art to which the present disclosure pertains from the description below.

[0035] FIG. 1 is a diagram schematically illustrating a video coding system to which an embodiment according to the present disclosure can be applied.

[0036] FIG. 2 is a schematic diagram of an image encoding device to which an embodiment according to the present disclosure can be applied.

[0037] FIG. 3 is a schematic diagram illustrating an image decoding device to which an embodiment according to the present disclosure can be applied.

[0038] Figure 4 is a flowchart illustrating an intra prediction-based video / image encoding method.

[0039] FIG. 5 is a diagram exemplarily illustrating the configuration of an intra prediction unit according to the present disclosure.

[0040] Fig. 6 is a flowchart illustrating an intra prediction-based video / image decoding method.

[0041] FIG. 7 is a diagram exemplarily illustrating the configuration of an intra prediction unit according to the present disclosure.

[0042] FIG. 8 is a diagram illustrating a template area used in a TIMD (Template-based Intra Mode Derivation) mode according to the present disclosure.

[0043] FIG. 9 is a diagram for explaining a template matching-based encoding / decoding method according to the present disclosure.

[0044] FIG. 10 is a diagram illustrating the locations of surrounding blocks for constructing an intra prediction candidate list according to one embodiment of the present disclosure.

[0045] FIG. 11 is a diagram illustrating a surrounding block search location according to one embodiment of the present disclosure.

[0046] Figure 12 is a flowchart showing a method of applying a merge mode according to the present disclosure.

[0047] FIG. 13 is a diagram illustrating a search location of a corresponding luma block according to one embodiment of the present disclosure.

[0048] FIG. 14 is a flowchart illustrating a method for applying a merge mode according to one embodiment of the present disclosure.

[0049] FIG. 15 is a flowchart of an encoding method according to one embodiment of the present disclosure.

[0050] FIG. 16 is a flowchart of a decryption method according to one embodiment of the present disclosure.

[0051] FIG. 17 is a diagram illustrating an example of a content streaming system to which an embodiment according to the present disclosure can be applied.

[0052] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the attached drawings so that those skilled in the art can easily implement the present disclosure. However, the present disclosure may be implemented in various different forms and is not limited to the embodiments described herein.

[0053] In describing embodiments of the present disclosure, detailed descriptions of known configurations or functions will be omitted if they are deemed to obscure the gist of the present disclosure. Furthermore, portions unrelated to the description of the present disclosure in the drawings have been omitted, and similar portions have been designated with similar reference numerals.

[0054] In the present disclosure, when a component is said to be "connected," "coupled," or "connected" to another component, this may include not only a direct connection, but also an indirect connection in which another component exists in between. Furthermore, when a component is said to "include" or "have" another component, unless otherwise specifically stated, this does not exclude the other component, but rather implies that the other component may be included.

[0055] In this disclosure, terms such as first, second, etc. are used solely to distinguish one component from another, and do not limit the order or importance of components unless specifically stated otherwise. Accordingly, within the scope of this disclosure, a first component in one embodiment may be referred to as a second component in another embodiment, and similarly, a second component in one embodiment may be referred to as a first component in another embodiment.

[0056] In this disclosure, distinct components are used to clearly illustrate their respective characteristics, and do not necessarily imply that the components are separated. That is, multiple components may be integrated into a single hardware or software unit, or a single component may be distributed into multiple hardware or software units. Therefore, even if not specifically mentioned, such integrated or distributed embodiments are also included within the scope of this disclosure.

[0057] In the present disclosure, the components described in various embodiments are not necessarily essential components, and some may be optional components. Therefore, embodiments comprising a subset of the components described in one embodiment are also within the scope of the present disclosure. Furthermore, embodiments including other components in addition to the components described in various embodiments are also within the scope of the present disclosure.

[0058] The present disclosure relates to encoding and decoding of images, and terms used in the present disclosure may have their usual meanings commonly used in the technical field to which the present disclosure belongs, unless newly defined in the present disclosure.

[0059] In the present disclosure, “video” may mean a set of images over time.

[0060] In the present disclosure, a "picture" generally refers to a unit representing one image of a specific time period, and a slice / tile is a coding unit that constitutes a part of a picture, and a single picture may be composed of one or more slices / tiles. In addition, a slice / tile may include one or more coding tree units (CTUs).

[0061] In the present disclosure, "pixel" or "pel" may refer to the smallest unit that constitutes a picture (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 chroma component.

[0062] In the present disclosure, a "unit" may represent a basic unit of image processing. A unit may include at least one of a specific region of a picture and information related to the region. In some cases, the term "unit" may be used interchangeably with terms such as "sample array," "block," or "area." In general, an MxN block may include a set (or array) of samples (or sample array) or transform coefficients consisting of M columns and N rows.

[0063] In the present disclosure, the "current block" may mean one of the following: a "current coding block," a "current coding unit," a "block to be encoded," a "block to be decoded," or a "block to be processed." When prediction is performed, the "current block" may mean a "current prediction block" or a "block to be predicted." When transformation (inverse transformation) / quantization (inverse quantization) is performed, the "current block" may mean a "current transformation block" or a "block to be transformed." When filtering is performed, the "current block" may mean a "block to be filtered."

[0064] In the present disclosure, a "current block" may mean a block that includes both a luma component block and a chroma component block, or a "luma block of the current block," unless explicitly described as a chroma block. The luma component block of the current block may be explicitly expressed by including an explicit description of the luma component block, such as "luma block" or "current luma block." Additionally, the chroma component block of the current block may be explicitly expressed by including an explicit description of the chroma component block, such as "chroma block" or "current chroma block."

[0065] In this disclosure, " / " and "," can be interpreted as "and / or". For example, "A / B" and "A, B" can be interpreted as "A and / or B". Additionally, "A / B / C" and "A, B, C" can mean "at least one of A, B, and / or C."

[0066] In this disclosure, "or" may be interpreted as "and / or." For example, "A or B" may mean 1) "A" only, 2) "B" only, or 3) "A and B." Alternatively, "or" in this disclosure may mean "additionally or alternatively."

[0067] In this disclosure, "at least one of A, B, and C" may mean "only A," "only B," "only C," or "any and all combinations of A, B, and C." Additionally, "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."

[0068] The parentheses used in this disclosure may mean "for example." For example, when "prediction (intra-prediction)" is indicated, "intra-prediction" may be suggested as an example of "prediction." In other words, "prediction" in this disclosure is not limited to "intra-prediction," and "intra-prediction" may be suggested as an example of "prediction." Furthermore, even when "prediction (i.e., intra-prediction)" is indicated, "intra-prediction" may be suggested as an example of "prediction."

[0069] Overview of Video Coding Systems

[0070] FIG. 1 is a diagram schematically illustrating a video coding system to which an embodiment according to the present disclosure can be applied.

[0071] A video coding system according to one embodiment may include an encoding device (10) and a decoding device (20). The encoding device (10) may transmit encoded video and / or image information or data to the decoding device (20) in the form of a file or streaming through a digital storage medium or a network.

[0072] An encoding device (10) according to one embodiment may include a video source generation unit (11), an encoding unit (12), and a transmission unit (13). A decoding device (20) according to one embodiment may include a reception unit (21), a decoding unit (22), and a rendering unit (23). The encoding unit (12) may be referred to as a video / image encoding unit, and the decoding unit (22) may be referred to as a video / image decoding unit. The transmission unit (13) may be included in the encoding unit (12). The reception unit (21) may be included in the decoding unit (22). The rendering unit (23) may include a display unit, and the display unit may be configured as a separate device or an external component.

[0073] The video source generation unit (11) can obtain video / images through a process of capturing, synthesizing, or generating video / images. The video source generation unit (11) can include a video / image capture device and / or a video / image generation device. The video / image capture device can include, for example, one or more cameras, a video / image archive including previously captured video / images, etc. The video / image generation device can include, for example, a computer, a tablet, a smartphone, etc., and can (electronically) generate video / images. For example, a virtual video / image can be generated through a computer, etc., in which case the video / image capture process can be replaced with a process of generating related data.

[0074] The encoding unit (12) can encode input video / images. The encoding unit (12) can perform a series of procedures such as prediction, transformation, and quantization to improve compression and encoding efficiency. The encoding unit (12) can output encoded data (encoded video / image information) in the form of a bitstream.

[0075] The transmission unit (13) can obtain encoded video / image information or data output in the form of a bitstream, and transmit it to the reception unit (21) of the decoding device (20) or another external object through a digital storage medium or a 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, etc. The transmission unit (13) may include an element for generating a media file through a predetermined file format, and may include an element for transmission through a broadcasting / communication network. The transmission unit (13) may be provided as a separate transmission device from the encoding unit (120), and in this case, the transmission device may include at least one processor for obtaining encoded video / image information or data output in the form of a bitstream, and a transmission unit for transmitting it in the form of a file or streaming. The reception unit (21) can extract / receive the bitstream from the storage medium or network and transmit it to the decoding unit (22).

[0076] The decoding unit (22) can decode video / image by performing a series of procedures such as inverse quantization, inverse transformation, and prediction corresponding to the operation of the encoding unit (12).

[0077] The rendering unit (23) can render the decrypted video / image. The rendered video / image can be displayed through the display unit.

[0078] Overview of the video encoding device

[0079] FIG. 2 is a schematic diagram illustrating an image encoding device to which an embodiment according to the present disclosure can be applied.

[0080] As illustrated in FIG. 2, the image encoding device (100) may include an image segmentation unit (110), a subtraction unit (115), a transformation unit (120), a quantization unit (130), an inverse quantization unit (140), an inverse transformation unit (150), an addition unit (155), a filtering unit (160), a memory (170), an inter prediction unit (180), an intra prediction unit (185), and an entropy encoding unit (190). The inter prediction unit (180) and the intra prediction unit (185) may be collectively referred to as a “prediction unit.” The transformation unit (120), the quantization unit (130), the inverse quantization unit (140), and the inverse transformation unit (150) may be included in a residual processing unit. The residual processing unit may further include a subtraction unit (115).

[0081] All or at least some of the plurality of components constituting the video encoding device (100) may be implemented as a single hardware component (e.g., an encoder or a processor) according to an embodiment. In addition, the memory (170) may include a decoded picture buffer (DPB) and may be implemented by a digital storage medium.

[0082] The image segmentation unit (110) can segment an input image (or picture, frame) input to the image encoding device (100) into one or more processing units. For example, the processing unit may be called a coding unit (CU). The coding unit may be obtained by recursively segmenting a coding tree unit (CTU) or a largest coding unit (LCU) according to a QT / BT / TT (Quad-tree / binary-tree / ternary-tree) structure. For example, one coding unit may be segmented into a plurality of coding units of deeper depth based on a quad-tree structure, a binary-tree structure, and / or a ternary-tree structure. For segmenting the coding unit, the quad-tree structure may be applied first, and the binary-tree structure and / or the ternary-tree structure may be applied later. The coding procedure according to the present disclosure may be performed based on the final coding unit that is no longer segmented. The maximum coding unit can be used directly as the final coding unit, and the coding unit of the lower depth obtained by dividing the maximum coding unit can be used as the final concatenated unit. Here, the coding procedure may include procedures such as prediction, transformation, and / or restoration described below. As another example, the processing unit of the coding procedure may be a prediction unit (PU) or a transformation unit (TU). The prediction unit and the transformation unit may each be divided or partitioned from the final coding unit. The prediction unit may be a unit of sample prediction, and the transformation unit may be a unit that derives a transform coefficient and / or a unit that derives a residual signal from a transform coefficient.

[0083] The prediction unit (inter-prediction unit (180) or intra-prediction unit (185)) can perform prediction on a block to be processed (current block) and generate a predicted block including prediction samples for the current block. The prediction unit can determine whether intra-prediction or inter-prediction is applied to the current block or CU unit. The prediction unit can generate various information regarding the prediction of the current block and transmit the information to the entropy encoding unit (190). The information regarding the prediction can be encoded by the entropy encoding unit (190) and output in the form of a bitstream.

[0084] The intra prediction unit (185) can predict the current block by referring to samples within the current picture. The referenced samples may be located in the neighborhood of the current block or may be located away from it, depending on the intra prediction mode and / or intra prediction technique. The intra prediction modes may include a plurality of non-directional modes and a plurality of directional modes. The non-directional modes may include, for example, a DC mode and a planar mode. The directional modes may include, for example, 33 directional prediction modes or 65 directional prediction modes, depending on the degree of detail in the prediction direction. However, this is merely an example, and a greater or lesser number of directional prediction modes may be used depending on the settings. The intra prediction unit (185) may also determine the prediction mode applied to the current block by using the prediction mode applied to the neighboring blocks.

[0085] The inter prediction unit (180) can derive a predicted block for the current block based on a reference block (reference sample array) specified by a motion vector on a reference picture. At this time, in order to reduce the amount of motion information transmitted in the inter prediction mode, the motion information can be predicted in units of blocks, sub-blocks, or samples based on the correlation of the motion information between the neighboring blocks and the current block. The motion information can include a motion vector and a reference picture index. The motion information can further include information on the inter prediction direction (L0 prediction, L1 prediction, Bi prediction, etc.). In the case of inter prediction, the neighboring block can include a spatial neighboring block existing in the current picture and a temporal neighboring block existing in the reference picture. The reference picture including the reference block and the reference picture including the temporal neighboring block may be the same or different from each other. The temporal neighboring block may be called a collocated reference block, a collocated CU (colCU), etc. A reference picture including the above temporal neighboring blocks may be called a collocated picture (colPic). For example, the inter prediction unit (180) may construct a motion information candidate list based on neighboring blocks and generate information indicating which candidate is used to derive the motion vector and / or reference picture index of the current block. Inter prediction may be performed based on various prediction modes, and for example, in the case of skip mode and merge mode, the inter prediction unit (180) may use the motion information of neighboring blocks as the motion information of the current block. In the case of skip mode, unlike the merge mode, a residual signal may not be transmitted.In the motion vector prediction (MVP) mode, the motion vector of the current block can be signaled by using the motion vector of the surrounding blocks as the motion vector predictor and encoding the motion vector difference and an indicator for the motion vector predictor. The motion vector difference can mean the difference between the motion vector of the current block and the motion vector predictor.

[0086] The prediction unit can generate a prediction signal based on various prediction methods and / or prediction techniques described below. For example, the prediction unit can apply intra prediction or inter prediction to predict the current block, and can also apply intra prediction and inter prediction simultaneously. A prediction method that simultaneously applies intra prediction and inter prediction to predict the current block may be called combined inter and intra prediction (CIIP). In addition, the prediction unit may perform intra block copy (IBC) to predict the current block. Intra block copy can be used for video / image coding of content such as games, such as screen content coding (SCC). IBC is a method of predicting the current block using a previously restored reference block within the current picture located at a predetermined distance from the current block. When IBC is applied, the location of the reference block within the current picture can be encoded as a vector (block vector) corresponding to the predetermined distance. IBC basically performs prediction within the current picture, but can be performed similarly to inter prediction in that it derives reference blocks within the current picture. That is, IBC can utilize at least one of the inter prediction techniques described in the present disclosure.

[0087] The prediction signal generated through the prediction unit can be used to generate a restoration signal or a residual signal. The subtraction unit (115) can generate a residual signal (residual block, residual sample array) by subtracting the prediction signal (predicted block, predicted sample array) output from the prediction unit from the input image signal (original block, original sample array). The generated residual signal can be transmitted to the conversion unit (120).

[0088] The transform unit (120) can apply a transform technique to the residual signal to generate transform coefficients. For example, the transform technique can include at least one of a Discrete Cosine Transform (DCT), a Discrete Sine Transform (DST), a Karhunen-Loeve Transform (KLT), a Graph-Based Transform (GBT), or a Conditionally Non-linear Transform (CNT). Here, GBT refers to a transform obtained from a graph when the relationship information between pixels is expressed as a graph. CNT refers to a transform obtained based on generating a prediction signal using all previously reconstructed pixels. The transform process can be applied to a pixel block having a square equal size, or can be applied to a block of a non-square variable size.

[0089] The quantization unit (130) can quantize the transform coefficients and transmit them to the entropy encoding unit (190). The entropy encoding unit (190) can encode the quantized signal (information about the quantized transform coefficients) and output it as a bitstream. The information about the quantized transform coefficients can be called residual information. The quantization unit (130) can rearrange the quantized transform coefficients in a block form into a one-dimensional vector form based on a coefficient scan order, and can also generate information about the quantized transform coefficients based on the quantized transform coefficients in the one-dimensional vector form.

[0090] The entropy encoding unit (190) can perform various encoding methods, such as, for example, exponential Golomb, context-adaptive variable length coding (CAVLC), and context-adaptive binary arithmetic coding (CABAC). The entropy encoding unit (190) can also encode, together or separately, information necessary for video / image restoration (e.g., values ​​of syntax elements) in addition to quantized transform coefficients. The encoded information (e.g., encoded video / image information) can be transmitted or stored in the form of a bitstream in the form of a network abstraction layer (NAL) unit. The video / image information may further include information on various parameter sets, such as an adaptation parameter set (APS), a picture parameter set (PPS), a sequence parameter set (SPS), or a video parameter set (VPS). In addition, the video / image information may further include general constraint information. The signaling information, transmitted information and / or syntax elements mentioned in the present disclosure may be encoded through the encoding procedure described above and included in the bitstream.

[0091] The above bitstream may be transmitted via a network or stored in a digital storage medium. Here, the network may include a broadcasting network and / or a communication network, and the digital storage medium may include various storage media such as USB, SD, CD, DVD, Blu-ray, HDD, SSD, etc. A transmission unit (not shown) for transmitting the signal output from the entropy encoding unit (190) and / or a storage unit (not shown) for storing the signal may be provided as an internal / external element of the video encoding device (100), or the transmission unit may be provided as a component of the entropy encoding unit (190).

[0092] The quantized transform coefficients output from the quantization unit (130) can be used to generate a residual signal. For example, by applying inverse quantization and inverse transformation to the quantized transform coefficients through the inverse quantization unit (140) and inverse transformation unit (150), a residual signal (residual block or residual samples) can be restored.

[0093] The addition unit (155) can generate a reconstructed signal (reconstructed picture, reconstructed block, reconstructed sample array) by adding the reconstructed residual signal to the prediction signal output from the inter prediction unit (180) or the intra prediction unit (185). When there is no residual for the block to be processed, such as when skip mode is applied, the predicted block can be used as the reconstructed block. The addition unit (155) can be called a reconstructor or a reconstructed block generation unit. The generated reconstructed signal can be used for intra prediction of the next block to be processed within the current picture, and can also be used for inter prediction of the next picture after filtering as described below.

[0094] Meanwhile, LMCS (luma mapping with chroma scaling) may be applied during the picture encoding and / or restoration process.

[0095] The filtering unit (160) can improve subjective / objective picture quality by applying filtering to the restoration signal. For example, the filtering unit (160) can apply various filtering methods to the restoration picture to generate a modified restoration picture, and store the modified restoration picture in the memory (170), specifically, in the DPB of the memory (170). The various filtering methods may include, for example, deblocking filtering, sample adaptive offset, adaptive loop filter, bilateral filter, etc. The filtering unit (160) can generate various information regarding filtering and transmit the information to the entropy encoding unit (190), as described later in the description of each filtering method. The information regarding filtering may be encoded by the entropy encoding unit (190) and output in the form of a bitstream.

[0096] The modified restored picture transmitted to the memory (170) can be used as a reference picture in the inter prediction unit (180). Through this, when inter prediction is applied, the image encoding device (100) can avoid prediction mismatch between the image encoding device (100) and the image decoding device, and can also improve encoding efficiency.

[0097] The DPB in the memory (170) can store a modified reconstructed picture to be used as a reference picture in the inter prediction unit (180). The memory (170) can store motion information of a block from which motion information in the current picture is derived (or encoded) and / or motion information of blocks in a picture that has already been reconstructed. The stored motion information can be transferred to the inter prediction unit (180) to be used as motion information of a spatial neighboring block or motion information of a temporal neighboring block. The memory (170) can store reconstructed samples of reconstructed blocks in the current picture and transfer them to the intra prediction unit (185).

[0098] Video Decryption Device Overview

[0099] FIG. 3 is a schematic diagram illustrating an image decoding device to which an embodiment according to the present disclosure can be applied.

[0100] As illustrated in FIG. 3, the image decoding device (200) may be configured to include an entropy decoding unit (210), an inverse quantization unit (220), an inverse transformation unit (230), an addition unit (235), a filtering unit (240), a memory (250), an inter prediction unit (260), and an intra prediction unit (265). The inter prediction unit (260) and the intra prediction unit (265) may be collectively referred to as a “prediction unit.” The inverse quantization unit (220) and the inverse transformation unit (230) may be included in a residual processing unit.

[0101] All or at least some of the plurality of components constituting the video decoding device (200) may be implemented as a single hardware component (e.g., a decoder or processor) depending on the embodiment. In addition, the memory (170) may include a DPB and may be implemented by a digital storage medium.

[0102] The video decoding device (200) that receives a bitstream including video / image information can restore the image by performing a process corresponding to the process performed in the video encoding device (100) of FIG. 2. For example, the video decoding device (200) can perform decoding using a processing unit applied in the video encoding device. Therefore, the processing unit for decoding may be, for example, a coding unit. The coding unit may be a coding tree unit or may be obtained by dividing a maximum coding unit. In addition, the restored image signal decoded and output by the video decoding device (200) can be reproduced through a reproduction device (not shown).

[0103] The video decoding device (200) can receive a signal output from the video encoding device of FIG. 2 in the form of a bitstream. The received signal can be decoded through the entropy decoding unit (210). For example, the entropy decoding unit (210) can parse the bitstream to derive information (e.g., video / image information) necessary for image restoration (or picture restoration). The video / image information may further include information on various parameter sets, such as an adaptation parameter set (APS), a picture parameter set (PPS), a sequence parameter set (SPS), or a video parameter set (VPS). In addition, the video / image information may further include general constraint information. The video decoding device may additionally use information on the parameter set and / or the general constraint information to decode the image. The signaling information, received information, and / or syntax elements mentioned in the present disclosure can be obtained from the bitstream by being decoded through the decoding procedure. For example, the entropy decoding unit (210) can decode information in the bitstream based on a coding method such as exponential Golomb coding, CAVLC, or CABAC, and output the values ​​of syntax elements required for image restoration and the quantized values ​​of transform coefficients for residuals. More specifically, the CABAC entropy decoding method receives a bin corresponding to each syntax element in the bitstream, determines a context model using information of the syntax element to be decoded and the decoding information of the surrounding block and the decoding target block or the information of the symbol / bin decoded in the previous step, and predicts the occurrence probability of the bin according to the determined context model to perform arithmetic decoding of the bin to generate a symbol corresponding to the value of each syntax element.At this time, the CABAC entropy decoding method can update the context model using the information of the decoded symbol / bin for the context model of the next symbol / bin after determining the context model. Information regarding prediction among the information decoded by the entropy decoding unit (210) is provided to the prediction unit (inter prediction unit (260) and intra prediction unit (265)), and the residual value on which entropy decoding is performed by the entropy decoding unit (210), i.e., quantized transform coefficients and related parameter information, can be input to the inverse quantization unit (220). In addition, information regarding filtering among the information decoded by the entropy decoding unit (210) can be provided to the filtering unit (240). Meanwhile, a receiving unit (not shown) that receives a signal output from an image encoding device may be additionally provided as an internal / external element of the image decoding device (200), or the receiving unit may be provided as a component of an entropy decoding unit (210).

[0104] Meanwhile, the video decoding device according to the present disclosure may be referred to as a video / video / picture decoding device. The video decoding device may include an information decoder (video / video / picture information decoder) and / or a sample decoder (video / video / picture sample decoder). The information decoder may include an entropy decoding unit (210), and the sample decoder may include at least one of an inverse quantization unit (220), an inverse transformation unit (230), an addition unit (235), a filtering unit (240), a memory (250), an inter prediction unit (260), and an intra prediction unit (265).

[0105] The inverse quantization unit (220) can inverse quantize the quantized transform coefficients and output the transform coefficients. The inverse quantization unit (220) can rearrange the quantized transform coefficients into a two-dimensional block form. In this case, the rearrangement can be performed based on the coefficient scanning order performed in the image encoding device. The inverse quantization unit (220) can perform inverse quantization on the quantized transform coefficients using quantization parameters (e.g., quantization step size information) and obtain transform coefficients.

[0106] In the inverse transform unit (230), the transform coefficients can be inversely transformed to obtain a residual signal (residual block, residual sample array).

[0107] The prediction unit can perform a prediction on the current block and generate a predicted block containing prediction samples for the current block. The prediction unit can determine whether intra-prediction or inter-prediction is applied to the current block based on the prediction information output from the entropy decoding unit (210), and can determine a specific intra / inter-prediction mode (prediction technique).

[0108] The fact that the prediction unit can generate a prediction signal based on various prediction methods (techniques) described below is the same as that mentioned in the description of the prediction unit of the image encoding device (100).

[0109] The intra prediction unit (265) can predict the current block by referring to samples within the current picture. The description of the intra prediction unit (185) can be equally applied to the intra prediction unit (265).

[0110] The inter prediction unit (260) can derive a predicted block for the current block based on a reference block (reference sample array) specified by a motion vector on a reference picture. At this time, in order to reduce the amount of motion information transmitted in the inter prediction mode, the motion information can be predicted in units of blocks, sub-blocks, or samples based on the correlation of the motion information between the neighboring blocks and the current block. The motion information can include a motion vector and a reference picture index. The motion information can further include information on the inter prediction direction (L0 prediction, L1 prediction, Bi prediction, etc.). In the case of inter prediction, the neighboring blocks can include spatial neighboring blocks existing in the current picture and temporal neighboring blocks existing in the reference picture. For example, the inter prediction unit (260) can construct a motion information candidate list based on the neighboring blocks, and derive the motion vector and / or reference picture index of the current block based on the received candidate selection information. Inter prediction can be performed based on various prediction modes (techniques), and the information about the prediction can include information indicating the mode (technique) of inter prediction for the current block.

[0111] The addition unit (235) can generate a restoration signal (restored picture, restoration block, restoration sample array) by adding the acquired residual signal to the prediction signal (predicted block, prediction sample array) output from the prediction unit (including the inter prediction unit (260) and / or the intra prediction unit (265)). When there is no residual for the block to be processed, such as when the skip mode is applied, the predicted block can be used as the restoration block. The description of the addition unit (155) can be equally applied to the addition unit (235). The addition unit (235) can be called a restoration unit or a restoration block generation unit. The generated restoration signal can be used for intra prediction of the next block to be processed within the current picture, and can also be used for inter prediction of the next picture after going through filtering as described below.

[0112] The filtering unit (240) can improve subjective / objective image quality by applying filtering to the restored signal. For example, the filtering unit (240) can apply various filtering methods to the restored picture to generate a modified restored picture, and store the modified restored picture in the memory (250), specifically, in the DPB of the memory (250). The various filtering methods can include, for example, deblocking filtering, sample adaptive offset, adaptive loop filter, bilateral filter, etc.

[0113] The (modified) reconstructed picture stored in the DPB of the memory (250) can be used as a reference picture in the inter prediction unit (260). The memory (250) can store motion information of a block from which motion information is derived (or decoded) within the current picture and / or motion information of blocks within a picture that has already been reconstructed. The stored motion information can be transferred to the inter prediction unit (260) to be used as motion information of a spatial neighboring block or motion information of a temporal neighboring block. The memory (250) can store reconstructed samples of reconstructed blocks within the current picture and transfer them to the intra prediction unit (265).

[0114] In this specification, the embodiments described in the filtering unit (160), the inter prediction unit (180), and the intra prediction unit (185) of the image encoding device (100) can be applied to the filtering unit (240), the inter prediction unit (260), and the intra prediction unit (265) of the image decoding device (200) in the same or corresponding manner, respectively.

[0115] Overview of Intra Prediction

[0116] Hereinafter, intra prediction according to the present disclosure is described.

[0117] Intra prediction may refer to a prediction that generates prediction samples for a current block based on reference samples within a picture to which the current block belongs (hereinafter, referred to as the current picture). When intra prediction is applied to a current block, neighboring reference samples to be used for intra prediction of the current block may be derived. The neighboring reference samples of the current block may include a sample adjacent to the left boundary of the current block of a size nWxnH and a total of 2xnH samples adjacent to the bottom-left, a sample adjacent to the top boundary of the current block and a total of 2xnW samples adjacent to the top-right, and one sample adjacent to the top-left of the current block. Alternatively, the neighboring reference samples of the current block may include upper neighboring samples of multiple columns and left neighboring samples of multiple rows. Additionally, the surrounding reference samples of the current block may include a total of nH samples adjacent to the right boundary of the current block of size nWxnH, a total of nW samples adjacent to the bottom boundary of the current block, and one sample adjacent to the bottom-right of the current block.

[0118] However, some of the surrounding reference samples of the current block may not yet be decoded or available. In this case, the decoder can construct the surrounding reference samples to be used for prediction by substituting the unavailable samples with available samples. Alternatively, the decoder can construct the surrounding reference samples to be used for prediction by interpolating the available samples.

[0119] When neighboring reference samples are derived, (i) a prediction sample can be derived based on an average or interpolation of neighboring reference samples of the current block, and (ii) the prediction sample can be derived based on a reference sample existing in a specific (prediction) direction with respect to the prediction sample among the neighboring reference samples of the current block. The case of (i) can be called a non-directional mode or a non-angular mode, and the case of (ii) can be called a directional mode or an angular mode.

[0120] In addition, the prediction sample may be generated through interpolation between a first surrounding sample located in the prediction direction of the intra prediction mode of the current block and a second surrounding sample located in the opposite direction based on the prediction target sample of the current block among the surrounding reference samples. The above-described case may be referred to as linear interpolation intra prediction (LIP).

[0121] Additionally, chroma prediction samples can be generated based on luma samples using a linear model. This case may be called LM (Linear Model) mode.

[0122] In addition, a temporary prediction sample of the current block may be derived based on filtered peripheral reference samples, and a prediction sample of the current block may be derived by weighting at least one reference sample derived according to the intra prediction mode among the existing peripheral reference samples, i.e., unfiltered peripheral reference samples, with the temporary prediction sample. This case may be called PDPC (Position dependent intra prediction).

[0123] In addition, a reference sample line with the highest prediction accuracy among the surrounding multiple reference sample lines of the current block can be selected, and a prediction sample can be derived using the reference samples located in the prediction direction of the selected line. At this time, information about the used reference sample line (e.g., intra_luma_ref_idx) can be encoded and signaled in the bitstream. This case may be called multi-reference line intra prediction (MRL) or MRL-based intra prediction. If MRL is not applied, reference samples can be derived from reference sample lines directly adjacent to the current block, and in this case, information about the reference sample line may not be signaled.

[0124] In addition, the current block can be divided into vertical or horizontal subpartitions, and intra prediction can be performed based on the same intra prediction mode for each subpartition. At this time, surrounding reference samples for intra prediction can be derived for each subpartition unit. That is, the reconstructed sample of the previous subpartition in the encoding / decoding order can be used as the surrounding reference sample of the current subpartition. In this case, the intra prediction mode for the current block is applied equally to the subpartitions, and by deriving and using surrounding reference samples for each subpartition unit, the intra prediction performance can be improved in some cases. This prediction method can be called intra sub-partitions (ISP) or ISP-based intra prediction.

[0125] The intra prediction techniques described above may be referred to by various terms, such as intra prediction types or additional intra prediction modes, to distinguish them from directional or non-directional intra prediction modes. For example, the intra prediction technique (intra prediction type or additional intra prediction mode, etc.) may include at least one of the above-described LIP, LM, PDPC, MRL, and ISP. A general intra prediction method excluding specific intra prediction types such as the above-described LIP, LM, PDPC, MRL, and ISP may be referred to as a normal intra prediction type. The normal intra prediction type may be generally applied when the above-described specific intra prediction types are not applied, and prediction may be performed based on the above-described intra prediction mode. Meanwhile, post-processing filtering may be performed on the derived prediction samples, if necessary.

[0126] Specifically, the intra prediction procedure may include an intra prediction mode / type determination step, a surrounding reference sample derivation step, and an intra prediction mode / type-based prediction sample derivation step. Additionally, a post-processing filtering step may be performed on the derived prediction samples, if necessary.

[0127] Meanwhile, in addition to the intra prediction types described above, affine linear weighted intra prediction (ALWIP) may be used. The ALWIP may also be called linear weighted intra prediction (LWIP) or matrix weighted intra prediction (MIP or matrix based intra prediction). When the MIP is applied to the current block, prediction samples for the current block may be derived by i) performing a matrix-vector-multiplication procedure using surrounding reference samples on which an averaging procedure has been performed, ii) further performing a horizontal / vertical interpolation procedure as necessary. The intra prediction modes used for the MIP may be configured differently from the intra prediction modes used in the LIP, PDPC, MRL, ISP intra prediction, or normal intra prediction described above. The intra prediction mode for the MIP may be called a MIP intra prediction mode, a MIP prediction mode, or a MIP mode. For example, the metrics and offsets used in the matrix vector multiplication may be set differently depending on the intra prediction mode for the MIP. Here, the metrics may be referred to as (MIP) weight metrics, and the offset may be referred to as (MIP) offset vectors or (MIP) bias vectors. A specific MIP method will be described later.

[0128] The block restoration procedure based on intra prediction and the intra prediction unit within the encoding device are described below with reference to FIGS. 4 and 5.

[0129] Figure 4 is a flowchart illustrating an intra prediction-based video / image encoding method.

[0130] The encoding method of FIG. 4 can be performed by the video encoding device of FIG. 2. Specifically, step S410 can be performed by the intra prediction unit (185), and step S420 can be performed by the residual processing unit. Specifically, step S420 can be performed by the subtraction unit (115). Step S430 can be performed by the entropy encoding unit (190). The prediction information of step S430 is derived by the intra prediction unit (185), and the residual information of step S430 can be derived by the residual processing unit. The residual information is information about the residual samples. The residual information can include information about quantized transform coefficients for the residual samples. As described above, the residual samples are derived as transform coefficients through the transform unit (120) of the image encoding device, and the transform coefficients can be derived as quantized transform coefficients through the quantization unit (130). Information about the quantized transform coefficients can be encoded in the entropy encoding unit (190) through a residual coding procedure.

[0131] An image encoding device can perform intra prediction on a current block (S410). The image encoding device can determine an intra prediction mode / type for the current block, derive peripheral reference samples of the current block, and then generate prediction samples within the current block based on the intra prediction mode / type and the peripheral reference samples. Here, the procedures of determining the intra prediction mode / type, deriving peripheral reference samples, and generating prediction samples may be performed simultaneously, or one procedure may be performed before the other.

[0132] FIG. 5 is a diagram exemplarily illustrating the configuration of an intra prediction unit (185) according to the present disclosure.

[0133] As illustrated in FIG. 5, the intra prediction unit (185) of the video encoding device may include an intra prediction mode / type determination unit (186), a reference sample derivation unit (187), and / or a prediction sample derivation unit (188). The intra prediction mode / type determination unit (186) may determine an intra prediction mode / type for the current block. The reference sample derivation unit (187) may derive surrounding reference samples of the current block. The prediction sample derivation unit (188) may derive prediction samples of the current block. Meanwhile, although not illustrated, when a prediction sample filtering procedure described below is performed, the intra prediction unit (185) may further include a prediction sample filtering unit (not illustrated).

[0134] The video encoding device can determine a mode / type to be applied to the current block among a plurality of intra prediction modes / types. The video encoding device can compare rate distortion costs (RD costs) for the intra prediction modes / types and determine an optimal intra prediction mode / type for the current block.

[0135] Meanwhile, the video encoding device may also perform a predictive sample filtering procedure. Predictive sample filtering may be referred to as post-filtering. Some or all of the predictive samples may be filtered through the predictive sample filtering procedure. In some cases, the predictive sample filtering procedure may be omitted.

[0136] Referring again to FIG. 4, the video encoding device can generate residual samples for the current block based on the predicted samples or the filtered predicted samples (S420). The video encoding device can derive the residual samples by subtracting the predicted samples from the original samples of the current block. In other words, the video encoding device can derive the residual sample value by subtracting the corresponding predicted sample value from the original sample value.

[0137] The video encoding device can encode video information including information about the intra prediction (prediction information) and residual information about the residual samples (S430). The prediction information can include the intra prediction mode information and / or the intra prediction technique information. The video encoding device can output the encoded video information in the form of a bitstream. The output bitstream can be transmitted to the video decoding device via a storage medium or a network.

[0138] The residual information may include the residual coding syntax described below. The video encoding device may transform / quantize the residual samples to derive quantized transform coefficients. The residual information may include information about the quantized transform coefficients.

[0139] Meanwhile, as described above, the video encoding device can generate a restored picture (including restored samples and restored blocks). To this end, the video encoding device can inversely quantize / inversely transform the quantized transform coefficients to derive (corrected) residual samples. The reason for performing inverse quantization / inverse transformation on the residual samples after transforming / quantizing them in this way is to derive residual samples that are identical to the residual samples derived from the video decoding device. The video encoding device can generate a restored block including restored samples for the current block based on the predicted samples and the (corrected) residual samples. A restored picture for the current picture can be generated based on the restored block. As described above, an in-loop filtering procedure, etc. can be further applied to the restored picture.

[0140] Fig. 6 is a flowchart illustrating an intra prediction-based video / image decoding method.

[0141] The image decoding device can perform an operation corresponding to an operation performed by the image encoding device.

[0142] The decoding method of FIG. 6 can be performed by the image decoding device of FIG. 3. Steps S610 to S630 can be performed by the intra prediction unit (265), and the prediction information of step S610 and the residual information of step S640 can be obtained from the bitstream by the entropy decoding unit (210). The residual processing unit of the image decoding device can derive residual samples for the current block based on the residual information (S640). Specifically, the inverse quantization unit (220) of the residual processing unit can derive transform coefficients by performing inverse quantization based on the quantized transform coefficients derived based on the residual information, and the inverse transform unit (230) of the residual processing unit can derive residual samples for the current block by performing inverse transformation on the transform coefficients. Step S650 can be performed by the addition unit (235) or the restoration unit.

[0143] Specifically, the video decoding device can derive an intra prediction mode / type for the current block based on the received prediction information (intra prediction mode / type information) (S610). In addition, the video decoding device can derive surrounding reference samples of the current block (S620). The video decoding device can generate prediction samples within the current block based on the intra prediction mode / type and the surrounding reference samples (S630). In this case, the video decoding device can perform a prediction sample filtering procedure. The prediction sample filtering may be referred to as post-filtering. Some or all of the prediction samples may be filtered by the prediction sample filtering procedure. In some cases, the prediction sample filtering procedure may be omitted.

[0144] The video decoding device can generate residual samples for the current block based on the received residual information (S640). The video decoding device can generate reconstructed samples for the current block based on the prediction samples and the residual samples, and derive a reconstructed block including the reconstructed samples (S650). A reconstructed picture for the current picture can be generated based on the reconstructed block. As described above, an in-loop filtering procedure, etc. can be further applied to the reconstructed picture.

[0145] FIG. 7 is a diagram exemplarily illustrating the configuration of an intra prediction unit (265) according to the present disclosure.

[0146] As illustrated in FIG. 7, the intra prediction unit (265) of the video decoding apparatus may include an intra prediction mode / type determination unit (266), a reference sample derivation unit (267), and a prediction sample derivation unit (268). The intra prediction mode / type determination unit (266) determines the intra prediction mode / type for the current block based on intra prediction mode / type information generated and signaled by the intra prediction mode / type determination unit (186) of the video encoding apparatus, and the reference sample derivation unit (266) may derive surrounding reference samples of the current block from a reconstructed reference region within the current picture. The prediction sample derivation unit (268) may derive prediction samples of the current block. Meanwhile, although not illustrated, when the above-described prediction sample filtering procedure is performed, the intra prediction unit (265) may further include a prediction sample filtering unit (not illustrated).

[0147] The intra prediction mode information may include flag information (e.g., intra_luma_mpm_flag) indicating, for example, whether the most probable mode (MPM) or the remaining mode is applied to the current block, and when the MPM is applied to the current block, the intra prediction mode information may further include index information (e.g., intra_luma_mpm_idx) indicating one of the intra prediction mode candidates (MPM candidates). The intra prediction mode candidates (MPM candidates) may be configured as an MPM candidate list 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 the intra prediction mode candidates (MPM candidates). The image decoding device may determine the intra prediction mode of the current block based on the intra prediction mode information.

[0148] In addition, the intra prediction technique information may be implemented in various forms. For example, the intra prediction technique information may include intra prediction technique index information indicating one of the intra prediction techniques. As another example, the intra prediction technique information may include at least one of reference sample line information (e.g., intra_luma_ref_idx) indicating whether the MRL is applied to the current block and, if so, which reference sample line is used, ISP flag information (e.g., intra_subpartitions_mode_flag) indicating whether the ISP is applied to the current block, ISP type information (e.g., intra_subpartitions_split_flag) indicating a split type of subpartitions if the ISP is applied, flag information indicating whether PDPC is applied, or flag information indicating whether LIP is applied. In addition, the intra prediction type information may include a MIP flag indicating whether MIP is applied to the current block. In the present disclosure, the ISP flag information may be referred to as an ISP application indicator.

[0149] The intra prediction mode information and / or the intra prediction technique information may be encoded / decoded using the coding method described in the present disclosure. For example, the intra prediction mode information and / or the intra prediction technique information may be encoded / decoded using entropy coding (e.g., CABAC, CAVLC) based on a truncated (rice) binary code.

[0150] Meanwhile, the intra prediction mode may further include a CCLM (cross-component linear model) mode for chroma samples in addition to the PLANAR mode, DC mode, and directional intra prediction modes. The CCLM mode may be divided into L_CCLM, T_CCLM, and LT_CCLM depending on whether left samples, upper samples, or both are considered for deriving CCLM parameters, and may only be applied to chroma components.

[0151] Intra prediction modes can be indexed, for example, as shown in Table 1 below.

[0152] Intra prediction modeAssociated name0INTRA_PLANAR1INTRA_DC2..66INTRA_ANGULAR2..INTRA_ANGULAR6681..83INTRA_LT_CCLM, INTRA_L_CCLM, INTRA_T_CCLM

[0153] Meanwhile, the intra prediction type (or additional intra prediction mode, etc.) may include at least one of the above-described LIP, PDPC, MRL, ISP, and MIP. The intra prediction type may be indicated based on intra prediction type information, and the intra prediction type information may 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) indicating whether the MRL is applied to the current block and, if so, which reference sample line is used, ISP flag information (e.g., intra_subpartitions_mode_flag) indicating whether the ISP is applied to the current block, ISP type information (e.g., intra_subpartitions_split_flag) indicating a split type of subpartitions if the ISP is applied, flag information indicating whether PDCP is applied, or flag information indicating whether LIP is applied. Additionally, the intra prediction type information may include a MIP flag (or may be called intra_mip_flag) indicating whether MIP is applied to the current block.

[0154] Overview of TIMD (Template-based intra mode derivation)

[0155] FIG. 8 is a diagram illustrating a template region used in the TIMD mode according to the present disclosure. For the intra prediction mode (IPM) of adjacent intra blocks and inter blocks in the surrounding area, as shown in FIG. 8, the SATD (sum of absolute transformed differences) between the predicted block predicted from the template region and the actual restored sample is calculated, and then the mode with the smallest SATD can be selected as the intra mode of the current block.

[0156] That is, the first two intra prediction modes with the minimum SATD are selected as the TIMD modes. These two TIMD modes are fused with weights, and this weighted intra prediction is used to encode the current CU. Position-dependent intra prediction combination (PDPC) can be included in the derivation of the TIMD mode.

[0157] The costs of the two selected modes are compared with a threshold, and the two cost factors are applied in the test as follows.

[0158] costMode2 < 2*costMode1

[0159] If the above conditions are true, fusion is applied, otherwise only mode 1 is used.

[0160] The weights of the modes are calculated by their SATD costs as follows:

[0161] weight1 = costMode2 / (costMode1+ costMode2)

[0162] weight2 = 1 - weight1

[0163] Template matching(TM)

[0164] FIG. 9 is a diagram for explaining a template matching-based encoding / decoding method according to the present disclosure.

[0165] Template Matching (TM) is a motion vector derivation method performed at the decoder stage. It is a method that can refine the motion information of the current block by finding a template (hereinafter referred to as a “reference template”) within a reference picture that is most similar to a template (hereinafter referred to as a “current template”) adjacent to the current block (e.g., current coding unit, current CU). The current template may be an upper neighboring block and / or a left neighboring block of the current block, or a part of these neighboring blocks. In addition, the reference template may be determined to have the same size as the current template.

[0166] As illustrated in Fig. 9, once the initial motion vector of the current block is derived, a search for a better motion vector can be performed in a surrounding area of ​​the initial motion vector. For example, the range of the surrounding area where the search is performed can be within a [-8, +8]-pel search area centered on the initial motion vector. In addition, the size of the search step for performing the search can be determined based on the AMVR mode of the current block. In addition, template matching can also be performed continuously with the bilateral matching process in merge mode.

[0167] If the prediction mode of the current block is AMVP mode, a motion vector predictor candidate (MVP candidate) may be determined based on a template matching error. For example, a motion vector predictor candidate (MVP candidate) that minimizes the error between the current template and a reference template may be selected. Thereafter, template matching for improving a motion vector may be performed on the selected motion vector predictor candidate. At this time, template matching for improving a motion vector may not be performed on motion vector predictor candidates that are not selected.

[0168] More specifically, the improvement of the selected motion vector predictor candidate can be started from full-pel accuracy within the [-8, +8]-pel search region using an iterative diamond search. Alternatively, it can be started from 4-pel accuracy in the case of 4-pel AMVR mode. This can be followed by a search for half-pel and / or quarter-pel accuracy depending on the AMVR mode. According to the search process, the motion vector predictor candidate can maintain the same motion vector accuracy as indicated by the AMVR mode even after the template matching process. In the iterative search process, the search process is terminated if the difference between the previous minimum cost and the current minimum cost is less than an arbitrary threshold. The threshold can be equal to the area of ​​the block, i.e., the number of samples in the block. Table 2 shows examples of search patterns according to the AMVR mode and the merge mode accompanied by AMVR.

[0169]

[0170] If the prediction mode of the current block is merge mode, a similar search method can be applied to the merge candidate indicated by the merge index. As shown in Table 2 above, template matching can be performed up to 1 / 8-pel accuracy or can skip half-pel accuracy or lower, which can be determined depending on whether an alternative interpolation filter is used according to merge motion information. In this case, the alternative interpolation filter can be a filter used when AMVR is half-pel mode. In addition, if template matching is available, depending on whether bilateral matching (BM) is available, the template matching can operate as an independent process, or can operate as an additional motion vector improvement process between block-based bilateral matching and sub-block-based bilateral matching. The availability of template matching and / or bilateral matching can be determined based on an availability condition check. The accuracy of the motion vector as described above can refer to the accuracy of the motion vector difference (MVD).

[0171] Hereinafter, a video encoding / decoding method according to one embodiment of the present disclosure will be described in detail.

[0172] The present disclosure may relate to intra prediction. Specifically, the present disclosure may relate to a method for adaptively selecting and / or applying an intra prediction method by utilizing encoding information of a neighboring block during intra prediction based on directional and / or non-directional modes in an intra prediction mode. In other words, the present disclosure may relate to a method for selecting and / or applying an intra prediction method by utilizing intra prediction information (e.g., candidate intra prediction information) of a neighboring block during intra prediction.

[0173] FIG. 10 is a diagram illustrating the positions of neighboring blocks for constructing an intra prediction candidate list according to one embodiment of the present disclosure. In the case of conventional intra prediction, the intra prediction candidate list (i.e., MPM list) of the current block (1010) can be constructed by utilizing intra prediction information of neighboring blocks (1020, 1030, 1040, 1050, 1060). In addition, in the case of ECM (Enhanced Compression Model), the intra prediction candidate list of the current block (1010) can be constructed by searching and / or selecting intra prediction modes of neighboring blocks in the following order: left neighboring block (1020), upper neighboring block (1030), lower left neighboring block (1040), upper right neighboring block (1050), and upper left neighboring block (1060).

[0174] At this time, the intra prediction candidate list of the current block (1010) may be composed of a directional intra mode and / or a non-directional intra mode (e.g., planar mode, DC mode). However, various intra prediction modes for predicting the current block may exist in the current Versatile Video Coding (VVC). For example, the intra prediction mode may include prediction modes such as a Multi Reference Line (MRL) prediction mode, an Intra sub-partition (ISP) prediction mode, a Matrix-based Intra Prediction (MIP) prediction mode, a Cross-Component Linear Model (CCLM) prediction mode, and an Intra Block Copy (IBC) prediction mode in addition to the traditional intra mode (directional mode, non-directional mode).

[0175] Additionally, for ECM, the intra prediction mode may include various intra prediction modes such as extended planar mode, gradient PDPC (position dependent intra prediction), TMRL (template-based MRL), 6-tap interpolation filter, DIMD (decoder side intra mode derivation), TIMD (template-based intra mode derivation), CIIP (combined inter and intra prediction) PDPC blending, SGPM (spatial geometric partitioning mode), intra prediction fusion, intraTMP (Intra Template Matching), IBC, LM (linear mode) parameter signaling, MMLM (multi-model linear mode), chroma intra fusion, CCCM (convolutional cross-component model), GLM (gradient linear model), and GL-CCCM (gradient and location based convolutional cross-component model). The various intra prediction modes described above may be referred to as general intra prediction information.

[0176] Existing intra prediction candidate lists can only be composed of traditional intra modes (directional and non-directional). Therefore, various intra prediction modes, such as SGPM and intra-template matching, described above, may not be considered when constructing the intra prediction candidate list. This could lead to the disadvantage of not fully utilizing intra prediction information from surrounding blocks.

[0177] The present disclosure proposes a merge mode-based intra prediction method that utilizes various intra prediction information (i.e., general intra prediction information) of neighboring blocks when performing intra prediction on a current block. In other words, the present disclosure proposes a method for efficiently utilizing all general intra prediction information, such as SGPM, GLM, CCCM, DIMD, and TIMD, in addition to the traditional prediction modes of neighboring blocks.

[0178] Example 1

[0179] The present disclosure proposes a merge mode that utilizes general intra prediction information of surrounding blocks for the current block when intra-predicting a luma block. In other words, the present disclosure proposes a merge mode that utilizes various intra-prediction information of surrounding blocks when intra-predicting a luma block.

[0180] In conventional methods, only traditional intra prediction information from surrounding blocks was considered when predicting the current block's intra prediction. However, because VVC and ECM utilize a wider variety of intra prediction methods, intra prediction that only considers traditional intra prediction information can be inefficient.

[0181] In an embodiment of the present disclosure, a list of intra prediction candidates to be applied to a current coded block and / or a current decoded block can be constructed by utilizing general intra prediction information of surrounding blocks. Accordingly, the present disclosure can select one candidate intra prediction information from among the candidate intra prediction information included in the intra prediction candidate list and apply it to the current block. In other words, the present disclosure can perform intra prediction by selecting one candidate intra prediction information from among the candidate intra prediction information included in the intra prediction candidate list.

[0182] To construct a list of intra prediction candidates, the present disclosure may collect general intra prediction information by searching surrounding blocks of the current block to be encoded and / or decoded. The general intra prediction information of the surrounding blocks may include the following prediction information.

[0183] - Information about the on-screen predictive directionality mode

[0184] - extended planar information

[0185] - MRL information

[0186] - TMRL Information

[0187] - ISP information

[0188] - MIP information

[0189] - Interpolation filter information

[0190] - DIMD Information

[0191] - TIMD Information

[0192] - SGPM Information

[0193] - intra prediction fusion information

[0194] - intraTMP information

[0195] - IBC Information

[0196] - Peripheral reference sample characteristic information

[0197] Here, the specific mode information may include information indicating whether a specific mode is applied. For example, the MRL information may include information indicating whether the MRL is applied. As another example, the TIMD information may include information indicating whether the TIMD is applied. That is, general intra prediction information may include intra prediction coding status information of a neighboring block for which encoding and / or decoding has been completed. More specifically, the above-described "information" may include various types of information, such as mode information, mode index, reference sample index, reference sample characteristics, template matching information, mode merging, and weights.

[0198] For example, if the SGPM mode is applied to the left peripheral block (1020) of FIG. 10, the presence or absence of SGPM application can be True. In addition, information about the applied SGPM (e.g., SGPM direction, intra prediction mode applied to two blocks, etc.) can also be collected. As another example, if the 33rd directional mode and TMRL are applied together to the upper right peripheral block (1050) of FIG. 10, the applied intra prediction mode, information about the reference sample line selected by TMRL, etc. can be additionally collected.

[0199] As another example, when intraTMP is applied to the upper peripheral block (1030) of FIG. 10, whether intraTMP is applied, additional information on the applied intraTMP, etc. can be additionally collected. The method for collecting intra-prediction information of peripheral blocks proposed in the present disclosure is not limited to the examples described above, and if intra-prediction information not included in the examples described above is newly proposed, the corresponding intra-prediction information can also be collected through the same method.

[0200] The present disclosure may select the surrounding blocks (1020, 1030, 1040, 1050, 1060) of FIG. 10 to search for surrounding blocks. Accordingly, the present disclosure may search for the corresponding surrounding blocks (1020, 1030, 1040, 1050, 1060). That is, intra prediction information for the surrounding blocks (1020, 1030, 1040, 1050, 1060) may be collected. At this time, the present disclosure may search for the surrounding blocks in the following search order.

[0201] - Left peripheral block (1020) -> Upper peripheral block (1030) -> Lower left peripheral block (1040) -> Upper right peripheral block (1050) -> Upper left peripheral block (1060)

[0202] - Left peripheral block (1020) -> Upper peripheral block (1030) -> Upper right peripheral block (1050) -> Lower left peripheral block (1040) -> Upper left peripheral block (1060)

[0203] - Upper peripheral block (1030) -> Left peripheral block (1020) -> Upper right peripheral block (1050) -> Lower left peripheral block (1040) -> Upper left peripheral block (1060)

[0204] The order of searching for surrounding blocks according to the present disclosure is not limited to the order described above, and the present disclosure can search for surrounding blocks in various orders.

[0205] FIG. 11 is a diagram illustrating a neighboring block search position according to one embodiment of the present disclosure. In addition to searching neighboring blocks (1120) adjacent to a current block (1110), the present disclosure can also search non-adjacent neighboring blocks (1130) to collect intra prediction information. Referring to FIG. 11, the present disclosure can collect intra prediction information of neighboring blocks (1120) adjacent to a current block and then collect intra prediction information of neighboring blocks (1130) not adjacent to the current block. In addition, according to one embodiment of the present disclosure, the numbers of neighboring blocks illustrated in FIG. 11 may indicate a neighboring block search order. However, the present disclosure is not limited thereto, and neighboring blocks may be searched in various orders.

[0206] According to one embodiment of the present disclosure, after comparing the reference sample characteristics of a current block with the reference sample characteristics of neighboring blocks, intra prediction information of the corresponding block can be collected only if a specific condition is satisfied. In this case, the comparison between the reference samples can be performed based on one of template matching, bidirectional matching, or sum of absolute transformed differences (SATD). That is, the neighboring blocks constituting the intra prediction candidate list can be determined based on the comparison between the reference samples of the current block and the reference samples of the neighboring blocks.

[0207] Additionally, according to one embodiment of the present disclosure, an intra prediction index indicating candidate intra prediction information within an intra prediction candidate list may be determined based on one of template matching, bidirectional matching, or SATD.

[0208] The search positions and / or search orders of adjacent and / or non-adjacent surrounding blocks proposed in the present disclosure are not limited to the examples described above, and may have a wider variety of search positions, numbers of search positions, and / or search orders.

[0209] According to the present disclosure, when collecting intra prediction information from adjacent and / or non-adjacent neighboring blocks, N pieces of intra prediction information to be applied to the current block can be collected from the neighboring blocks on a first-come, first-served basis. That is, after searching the neighboring blocks based on a predetermined order, N pieces of intra prediction information can be collected from the neighboring blocks. When all N pieces of intra prediction information have been collected, the search for the neighboring blocks can be terminated. In this case, N can be various natural numbers such as 3 or 6.

[0210] When collecting N pieces of intra prediction information in a first-come, first-served manner according to the present disclosure, neighboring blocks having the same intra prediction information can be excluded from the intra prediction candidate list by performing a pruning check using the methods below.

[0211] - Method 1. Perform pruning check by checking whether intra prediction mode is applied and all additional information used to apply intra prediction mode.

[0212] - Method 2. Perform pruning check by only checking whether intra prediction mode is applied.

[0213] - Method 3. Failure to perform pruning check

[0214] That is, after searching the surrounding blocks in a predetermined order, the intra prediction information of the surrounding blocks having the same intra prediction information can be excluded from the intra prediction candidate list. For example, when performing the pruning check by only checking whether the intra prediction mode is applied as in Method 2, even if the additional information (hereinafter referred to as “intra prediction additional information”) used to apply the corresponding intra prediction mode are different, the intra prediction information can be excluded from the intra prediction candidate list through the pruning check. That is, if the intra prediction candidate list includes the first intra prediction information and the second intra prediction information, and the intra prediction modes included in the first intra prediction information and the second intra prediction information are the same, even if the intra prediction additional information included in the first intra prediction information and the second intra prediction information are different, the intra prediction information added later (or the intra prediction information added earlier) can be excluded from the intra prediction candidate list.

[0215] Alternatively, the decoding complexity in the image decoding device (200) may be reduced by not performing a pruning check as in method 3. Alternatively, the encoding complexity in the image encoding device (100) may be reduced by not performing a pruning check as in method 3.

[0216] If the intra prediction candidate list is not filled with the preset N pieces of intra prediction information even after searching for adjacent neighboring blocks and / or non-adjacent neighboring blocks, the intra prediction candidate list may be filled with preset default modes. At this time, the default modes may be set according to the number of intra prediction pieces of information in the predetermined intra prediction candidate list. That is, if the intra prediction candidate list is filled with N pieces of intra prediction information, N default modes may be set. The present disclosure is not limited thereto, and M default modes may be set regardless of the number of intra prediction pieces of information in the intra prediction candidate list.

[0217] According to one embodiment of the present disclosure, after N candidate intra prediction information pieces are generated, the order of the candidate intra prediction information pieces may be reordered through template matching, bidirectional matching, or the like. For example, after all N candidate intra prediction information pieces are filled in the intra prediction candidate list, template matching may be performed using surrounding reference samples similar to the TMRL or TIMD method, and then the candidate intra prediction information pieces may be reordered in order of template cost. At this time, the reordering of the candidate intra prediction information pieces in the intra prediction candidate list may be performed in order of lowest template cost.

[0218] The present disclosure can perform intra prediction by selecting one of N candidate intra prediction information generated by the above-described method and applying the selected candidate intra prediction information to a current block. In this case, intra prediction can be performed using the following methods.

[0219] - Method 4. Apply only the intra prediction mode included in the selected candidate intra prediction information to the current block. The intra prediction additional information is transmitted to the image decoding device (200).

[0220] - Method 5. Apply all intra prediction modes and intra prediction additional information included in the selected candidate intra prediction information equally to the current block.

[0221] - Method 6. Modify the intra prediction mode and intra prediction additional information included in the selected candidate intra prediction information to suit the current block and then apply it.

[0222] Taking method 4 as an example, if the selected candidate intra prediction information includes the directional mode 50 as an intra prediction mode and the MRL index 7 as intra prediction additional information, the directional mode 50 can be applied to the current block. In this case, an MRL index more suitable for the current block can be transmitted to the image decoding device (200). That is, the image encoding device (100) can apply only the intra prediction mode among the candidate intra prediction information to the current block, and may not apply the intra prediction additional information to the current block.

[0223] Taking method 5 as an example, if the selected candidate intra prediction information includes the DIMD mode as an intra prediction mode and information that the planner, modes 18, 50, 33, and 66 are combined is included as intra prediction additional information, then intra prediction for the current block can be performed by performing DIMD by combining the predictors generated by the planner, modes 18, 50, 33, and 66.

[0224] Taking Method 6 as an example, if the selected candidate intra prediction information includes the SGPM mode as an intra prediction mode and the block splitting direction and intra prediction information of the two split blocks are included as intra prediction additional information, intra prediction for the current block can be adaptively performed by considering the position of the candidate block (surrounding block) representing the selected candidate intra prediction information and the position of the current block. That is, intra prediction can be performed by adaptively applying the block splitting direction and the intra prediction mode of the two split blocks to the current block.

[0225] According to one embodiment of the present disclosure, the number of candidate intra prediction information constituting the intra prediction candidate list, the neighboring block search position, the neighboring block search order, the candidate intra prediction information to be collected, etc. may be variously determined according to the width of the input block, the height of the input block, the number of pixels of the input block, the position of a sub-block within the input block, explicitly signaled syntax elements, statistical characteristics of neighboring pixels, whether a secondary transformation is used, etc. Here, the input block may be a current block.

[0226] According to one embodiment of the present disclosure, an intra prediction candidate index indicating one candidate intra prediction information included in an intra prediction candidate list may be determined based on at least one of a prediction mode (e.g., inter prediction mode, intra prediction mode), a width of an input block, a height of an input block, a number of pixels of an input block, a position of a sub-block within an input block, an explicitly signaled syntax element, statistical characteristics of surrounding pixels, and whether a secondary transform is used.

[0227] According to the present disclosure, candidate intra prediction information may be binarized using an appropriate binarization method and then transmitted to the image decoding device (200). For example, the intra prediction candidate index may be set to MPM mode, such as intra luma mode transmission, and the remaining intra prediction information may be binarized separately. That is, the intra prediction information of the current block may be binarized by setting it to MPM mode, and the remaining intra prediction information may be binarized separately. The present disclosure may save binarization bits by performing appropriate context modeling when binarizing each intra prediction information. Alternatively, the present disclosure may transmit the candidate intra prediction information to the image decoding device (200) by using a binarization method such as truncated binary, truncated unary, or fixed length, taking into account the number of candidate intra prediction information included in the intra prediction candidate list.

[0228] Information indicating whether the method (i.e., merge mode) proposed in the present disclosure is applied (hereinafter referred to as “merge mode application information”) can be signaled via HLS (High-level syntax). That is, the merge mode application information can be signaled via VPS (video parameter set), SPS (sequence parameter set), PPS (picture parameter set), picture header, slice header, DCI, etc. For example, in order to determine whether merge mode is applied on a PPS basis, the merge mode application information can be signaled via PPS.

[0229] In addition, the video decoding device (200) can adaptively determine whether the merge mode is applied without signaling the merge mode application information. Alternatively, the video decoding device (200) can determine whether the merge mode is applied by parsing the merge mode application information. For example, the video encoding device (100) can transmit the merge mode application information in units of CTU or CU. In this case, the merge mode application information can be transmitted to the video decoding device (200) using a 1-bit flag.

[0230] When the application of merge mode is determined based on the size of a specific block, the shape of a specific block, and whether a specific condition is satisfied, information on whether the merge mode is applied may be signaled only when the condition is satisfied. At this time, the application of merge mode information may be transmitted to the image decoding device (200) using a 1-bit flag. Here, the specific block may be a current block or a neighboring block, and the present disclosure is not limited thereto. For example, when the height of a specific block is four times or more the width of the specific block, the merge mode may not be applied. In this case, signaling of the application of merge mode information may be omitted. In addition, the application of merge mode may be implicitly inferred when the specific condition is satisfied.

[0231] Depending on whether the merge mode is applied or not signaled in HLS, whether the merge mode is applied or not information in the coding unit can be adaptively determined. For example, if the merge mode application information signaled in SPS is false (i.e., merge mode is not applied in the SPS unit), the merge mode may not be applied in the coding unit, and thus the merge mode application information may not be signaled.

[0232] FIG. 12 is a flowchart illustrating a method of applying a merge mode according to the present disclosure. Referring to FIG. 12, the image encoding device (100) and / or the image decoding device (200) may search for adjacent neighboring blocks and / or non-adjacent neighboring blocks (S1210). Here, the adjacent neighboring blocks and non-adjacent neighboring blocks may be the blocks illustrated in FIG. 11. The image encoding device (100) and / or the image decoding device (200) may collect intra prediction information of the adjacent neighboring blocks and / or non-adjacent neighboring blocks (S1230). The image encoding device (100) and / or the image decoding device (200) may configure an intra prediction candidate list based on the collected intra prediction information (S1250). The image encoding device (100) and / or the image decoding device (200) may select intra prediction information within the intra prediction candidate list (S1270). The video encoding device (100) and / or the video decoding device (200) can perform current block prediction based on the selected intra prediction information (S1290). That is, the video encoding device (100) and / or the video decoding device (200) can generate a prediction block of the current block by applying the selected intra prediction information to the current block.

[0233] Example 2

[0234] The present disclosure proposes a merge mode that utilizes general intra prediction information of neighboring blocks and co-located luma blocks for the current block during intra prediction of a chroma block. In other words, the present disclosure proposes a merge mode that utilizes various intra prediction information of neighboring chroma blocks and corresponding luma blocks during intra prediction of a chroma block.

[0235] In conventional methods, intra prediction of the current chroma block did not consider all intra prediction information from surrounding blocks, and only traditional intra prediction information was considered. Therefore, existing methods may be inefficient in terms of intra prediction mode selection and encoding information compression for the current chroma block.

[0236] The present disclosure proposes a method for performing intra prediction by utilizing intra prediction information of chroma neighboring blocks of a current chroma block and corresponding luma blocks. That is, an intra prediction candidate list can be constructed based on intra prediction information of neighboring blocks of the current chroma block and intra prediction information of the corresponding luma block. An image encoding device (100) and / or an image decoding device (200) can select one candidate intra prediction information among the candidate intra prediction information included in the constructed intra prediction candidate list and apply the selected candidate intra prediction information to the current block.

[0237] To construct an intra prediction candidate list, the present disclosure may collect intra prediction information by searching for neighboring blocks and corresponding luma blocks of the current chroma block to be encoded and / or decoded. The intra prediction information of the neighboring blocks of the current chroma block may include the following prediction information.

[0238] - Information about the on-screen predictive directionality mode

[0239] - extended planar information

[0240] - Interpolation filter information

[0241] - DIMD Information

[0242] - TIMD Information

[0243] - Intrachroma prediction fusion information

[0244] - CCLM Information

[0245] - MMLM information

[0246] - LM parameter signaling information

[0247] - CCCM Information

[0248] _ GLM Information

[0249] - GL-CCCM Information

[0250] - Reference sample characteristic information

[0251] Here, the specific mode information may include information indicating whether a specific mode is applied. For example, the CCLM information may include information indicating whether CCLM is applied. As another example, the TIMD information may include information indicating whether TIMD is applied. That is, the intra prediction information may include intra prediction coding status information of the surrounding blocks and the corresponding luma blocks for which encoding and / or decoding has been completed. More specifically, the above-described "information" may include various pieces of information such as mode information, a mode index, a reference sample index, reference sample characteristics, template matching information, mode merging, weights, model parameters, and filter information.

[0252] The method for collecting intra prediction information of surrounding blocks and corresponding luma blocks of the current chroma block according to the present disclosure is not limited to the above-described method, and if a new intra prediction mode is proposed, intra prediction information can be collected in the intra prediction mode through the same method.

[0253] The present disclosure may select the surrounding blocks (1020, 1030, 1040, 1050, 1060) of FIG. 10 to search for surrounding blocks of the current chroma block. Accordingly, the present disclosure may search for the corresponding surrounding blocks (1020, 1030, 1040, 1050, 1060). That is, intra prediction information for the surrounding blocks (1020, 1030, 1040, 1050, 1060) may be collected. At this time, the present disclosure may search for the surrounding blocks in the following search order.

[0254] - Left peripheral block (1020) -> Upper peripheral block (1030) -> Lower left peripheral block (1040) -> Upper right peripheral block (1050) -> Upper left peripheral block (1060)

[0255] - Left peripheral block (1020) -> Upper peripheral block (1030) -> Upper right peripheral block (1050) -> Lower left peripheral block (1040) -> Upper left peripheral block (1060)

[0256] - Upper peripheral block (1030) -> Left peripheral block (1020) -> Upper right peripheral block (1050) -> Lower left peripheral block (1040) -> Upper left peripheral block (1060)

[0257] The order of searching for surrounding blocks according to the present disclosure is not limited to the order described above, and the present disclosure can search for surrounding blocks in various orders.

[0258] The search position of the neighboring blocks of the current chroma block can be applied as described in FIG. 11 described above. That is, in addition to searching the neighboring blocks (1120) adjacent to the current block (1110), the present disclosure can search the non-adjacent neighboring blocks (1130) to collect intra prediction information. Referring to FIG. 11, the present disclosure can collect intra prediction information of the neighboring blocks (1120) adjacent to the current chroma block and then collect intra prediction information of the neighboring blocks (1130) not adjacent to the current chroma block. In addition, according to one embodiment of the present disclosure, the numbers of the neighboring blocks illustrated in FIG. 11 can indicate the search order of the neighboring blocks. However, the present disclosure is not limited thereto, and the neighboring blocks can be searched in various orders.

[0259] FIG. 13 is a diagram illustrating a search position of a corresponding luma block according to an embodiment of the present disclosure. The present disclosure can search for a corresponding luma block (1320) corresponding to a current chroma block (1310). Specifically, the video encoding device (100) and / or the video decoding device (200) can search for a specific position (1321, 1322, 1323, 1324, 1325) within the corresponding luma block and then collect intra prediction information of the corresponding position. In addition, the video encoding device (100) and / or the video decoding device (200) can search for surrounding blocks (1330, 1335, 1340, 1345, 1350) of the corresponding luma block and then collect intra prediction information of the corresponding block.

[0260] The search order of specific locations (1321, 1322, 1323, 1324, 1325) within the corresponding luma block may be in the order of 1321, 1322, 1323, 1324, 1325, but the search order of specific locations within the corresponding luma block according to the present disclosure is not limited thereto and may vary. In addition, the search order of neighboring blocks (1330, 1335, 1340, 1345, 1350) of the corresponding luma block may be in the listed order of 1330, 1335, 1340, 1345, 1350, but the search order of neighboring blocks of the corresponding luma block according to the present disclosure is not limited thereto and may vary. If the intra prediction mode included in the intra prediction information of the searched block is a mode that cannot be applied to the chroma block, the collection of the intra prediction information of the corresponding block may be omitted.

[0261] According to one embodiment of the present disclosure, after comparing the reference sample characteristics of a current block with the reference sample characteristics of neighboring blocks and corresponding luma blocks, intra prediction information of the corresponding block may be collected only when a specific condition is satisfied. At this time, the comparison between the reference samples may be performed based on one of template matching, bidirectional matching, SATD comparison between reference samples, or correlation comparison between reference samples. That is, neighboring blocks and / or corresponding luma blocks constituting an intra prediction candidate list may be determined based on a comparison between the reference samples of the current block and the reference samples of neighboring blocks and / or corresponding luma blocks.

[0262] Additionally, according to one embodiment of the present disclosure, an intra prediction index indicating candidate intra prediction information within an intra prediction candidate list may be determined based on one of template matching, bidirectional matching, SATD comparison between reference samples, or correlation comparison between reference samples.

[0263] The search positions and / or search orders of adjacent neighboring blocks, non-adjacent neighboring blocks, and / or corresponding luma blocks proposed in the present disclosure are not limited to the examples described above, and may have a wider variety of search positions, numbers of search positions, and / or search orders.

[0264] According to the present disclosure, when collecting intra prediction information from adjacent neighboring blocks, non-adjacent neighboring blocks, and / or corresponding luma blocks, N pieces of intra prediction information to be applied to a current block can be collected in a first-come, first-served manner from the neighboring blocks and / or corresponding luma blocks. That is, after searching the neighboring blocks and / or corresponding luma blocks based on a predetermined order, N pieces of intra prediction information can be collected from the neighboring blocks and / or corresponding luma blocks. When all N pieces of intra prediction information are collected, the search for the neighboring blocks and / or corresponding luma blocks can be terminated. At this time, N can be various natural numbers such as 3 or 6.

[0265] When collecting N pieces of intra prediction information in a first-come, first-served manner according to the present disclosure, neighboring blocks and / or corresponding luma blocks having the same intra prediction information can be excluded from the intra prediction candidate list by performing a pruning check using the methods below.

[0266] - Method 7. Perform pruning check by checking whether intra prediction mode is applied and additional information used for applying intra prediction mode.

[0267] - Method 8. Perform pruning check by only checking whether intra prediction mode is applied.

[0268] - Method 9. Failure to perform pruning check

[0269] That is, after searching for neighboring blocks and / or corresponding luma blocks in a predetermined order, intra prediction information of neighboring blocks and / or corresponding luma blocks having the same intra prediction information can be excluded from the intra prediction candidate list. For example, when performing a pruning check by only checking whether an intra prediction mode is applied as in method 8, even if the additional information (hereinafter referred to as “intra prediction additional information”) used for applying the corresponding intra prediction mode is different, the corresponding intra prediction information can be excluded from the intra prediction candidate list through the pruning check. That is, if the intra prediction candidate list includes the first intra prediction information and the second intra prediction information, and the intra prediction modes included in the first intra prediction information and the second intra prediction information are the same, even if the intra prediction additional information included in the first intra prediction information and the second intra prediction information are different, the intra prediction information added later (or the intra prediction information added earlier) can be excluded from the intra prediction candidate list.

[0270] Alternatively, the decoding complexity in the image decoding device (200) may be reduced by not performing a pruning check as in method 9. Alternatively, the encoding complexity in the image encoding device (100) may be reduced by not performing a pruning check as in method 9.

[0271] If the intra prediction candidate list is not filled with preset N pieces of intra prediction information even after searching for adjacent neighboring blocks and / or non-adjacent neighboring blocks and / or corresponding luma blocks, the intra prediction candidate list may be filled with preset default modes. At this time, the default modes may be set according to the number of intra prediction pieces of information in the predetermined intra prediction candidate list. That is, if the intra prediction candidate list is filled with N pieces of intra prediction information, N default modes may be set. The present disclosure is not limited thereto, and M default modes may be set regardless of the number of intra prediction pieces of information in the intra prediction candidate list.

[0272] According to one embodiment of the present disclosure, when collecting N candidate intra prediction information, the video encoding device (100) and / or the video decoding device (200) can generate two intra prediction candidate lists by separating linear models (LM, MMLM, CCCM, GLM, GL-CCCM, CCLM, etc.) and other modes (traditional intra prediction modes). Alternatively, the video encoding device (100) and / or the video decoding device (200) can generate the intra prediction candidate list by selecting only the traditional intra prediction mode. Alternatively, the video encoding device (100) and / or the video decoding device (200) can generate the intra prediction candidate list by selecting only the linear models (LM, MMLM, CCCM, GLM, GL-CCCM, CCLM, etc.).

[0273] According to one embodiment of the present disclosure, after N candidate intra prediction information pieces are generated, the order of the candidate intra prediction information pieces may be re-ordered through template matching, bidirectional matching, or the like. For example, after all N candidate intra prediction information pieces are filled in the intra prediction candidate list, template matching may be performed using surrounding reference samples similar to the TIMD method, and then the candidate intra prediction information pieces may be re-ordered in order of template cost. At this time, the re-ordering of the candidate intra prediction information pieces in the intra prediction candidate list may be performed in order of lowest template cost.

[0274] The present disclosure can perform intra prediction by selecting one of N candidate intra prediction information generated by the above-described method and applying the selected candidate intra prediction information to a current block. In this case, intra prediction can be performed using the following methods.

[0275] - Method 10. Apply only the intra prediction mode included in the selected candidate intra prediction information to the current block. The intra prediction additional information is transmitted to the image decoding device (200).

[0276] - Method 11. Apply all intra prediction modes and intra prediction additional information included in the selected candidate intra prediction information equally to the current block.

[0277] - Method 12. Modify the intra prediction mode and intra prediction additional information included in the selected candidate intra prediction information to suit the current block and then apply it.

[0278] According to one embodiment of the present disclosure, the number of candidate intra prediction information constituting the intra prediction candidate list, the search positions of neighboring blocks and / or corresponding luma blocks, the search order of neighboring blocks and / or corresponding luma blocks, the candidate intra prediction information to be collected, etc. may be variously determined according to the width of the input block, the height of the input block, the number of pixels of the input block, the position of a sub-block within the input block, explicitly signaled syntax elements, statistical characteristics of neighboring pixels, whether a secondary transform is used, etc. Here, the input block may be a current block.

[0279] According to one embodiment of the present disclosure, an intra prediction candidate index indicating one candidate intra prediction information included in an intra prediction candidate list may be determined based on at least one of a prediction mode (e.g., inter prediction mode, intra prediction mode), a width of an input block, a height of an input block, a number of pixels of an input block, a position of a sub-block within an input block, an explicitly signaled syntax element, statistical characteristics of surrounding pixels, and whether a secondary transform is used.

[0280] According to the present disclosure, candidate intra prediction information may be binarized using an appropriate binarization method and then transmitted to the image decoding device (200). For example, the intra prediction candidate index may be set to MPM mode, such as intra luma mode transmission, and the remaining intra prediction information may be binarized separately. That is, the intra prediction information of the current block may be binarized by setting it to MPM mode, and the remaining intra prediction information may be binarized separately. The present disclosure may save binarization bits by performing appropriate context modeling when binarizing each intra prediction information. Alternatively, the present disclosure may transmit the candidate intra prediction information to the image decoding device (200) by using a binarization method such as truncated binary, truncated unary, or fixed length, taking into account the number of candidate intra prediction information included in the intra prediction candidate list.

[0281] Information indicating whether the method (i.e., merge mode) proposed in the present disclosure is applied (hereinafter referred to as “merge mode application information”) can be signaled via HLS (High-level syntax). That is, the merge mode application information can be signaled via VPS (video parameter set), SPS (sequence parameter set), PPS (picture parameter set), picture header, slice header, DCI, etc. For example, in order to determine whether merge mode is applied on a PPS basis, the merge mode application information can be signaled via PPS.

[0282] In addition, the video decoding device (200) can adaptively determine whether the merge mode is applied without signaling the merge mode application information. Alternatively, the video decoding device (200) can determine whether the merge mode is applied by parsing the merge mode application information. For example, the video encoding device (100) can transmit the merge mode application information in units of CTU or CU. In this case, the merge mode application information can be transmitted to the video decoding device (200) using a 1-bit flag.

[0283] When whether to apply the merge mode is determined based on the size of a specific block, the shape of a specific block, whether a specific condition is satisfied, etc., information on whether to apply the merge mode may be signaled only when the condition is satisfied. At this time, the information on whether to apply the merge mode may be transmitted to the image decoding device (200) using a 1-bit flag. Here, the specific block may be a current block, a neighboring block, or a corresponding luma block, and the present disclosure is not limited thereto. For example, when the height of a specific block is four times or more the width of the specific block, the merge mode may not be applied. In this case, signaling information on whether to apply the merge mode may be omitted. In addition, whether to apply the merge mode may be implicitly inferred when the specific condition is satisfied.

[0284] Depending on whether the merge mode is applied or not signaled in HLS, whether the merge mode is applied or not information in the coding unit can be adaptively determined. For example, if the merge mode application information signaled in SPS is false (i.e., merge mode is not applied in the SPS unit), the merge mode may not be applied in the coding unit, and thus the merge mode application information may not be signaled.

[0285] FIG. 14 is a flowchart illustrating a method of applying a merge mode according to the present disclosure. Referring to FIG. 14, the image encoding device (100) and / or the image decoding device (200) may search for adjacent neighboring blocks, non-adjacent neighboring blocks, and / or corresponding luma blocks (S1410). Here, the adjacent neighboring blocks and / or non-adjacent neighboring blocks may be the blocks illustrated in FIG. 11. In addition, the corresponding luma block may be the block (1320) illustrated in FIG. 13. The image encoding device (100) and / or the image decoding device (200) may collect intra prediction information of the adjacent neighboring blocks, non-adjacent neighboring blocks, and / or corresponding luma blocks (S1430). The image encoding device (100) and / or the image decoding device (200) may configure an intra prediction candidate list based on the collected intra prediction information (S1450). The video encoding device (100) and / or the video decoding device (200) can select intra prediction information from the intra prediction candidate list (S1470). The video encoding device (100) and / or the video decoding device (200) can perform current chroma block prediction based on the selected intra prediction information (S1490). That is, the video encoding device (100) and / or the video decoding device (200) can generate a prediction block of the current chroma block by applying the selected intra prediction information to the current chroma block.

[0286] FIG. 15 is a flowchart of an encoding method according to one embodiment of the present disclosure. Referring to FIG. 15, an image encoding device (100) may obtain one or more candidate intra prediction information based on intra prediction information of surrounding blocks of a current block (S1510). Here, the candidate intra prediction information may include at least one of TIMD (Template based intra mode derivation) information, DIMD (Decoder side intra mode derivation) information, linear model information, LIP (Linear interpolation intra prediction) information, PDPC (Position dependent intra prediction) information, MRL (Multi reference line) information, TMRL (Template-based multiple reference line) information, ISP (Intra sub-partition) information, MIP (Matrix-based intra prediction) information, interpolation filter information, MDIS (Mode dependent intra smoothing) information, CIIP (Combined inter and intra prediction) information, SGPM (Spatial geometric partition mode) information, intraTMP (Template matching intra prediction) information, intra prediction directional mode information, extended planar information, intra prediction fusion information, surrounding reference sample characteristic information, or IBC (Intra block copy) information.

[0287] The video encoding device (100) may configure an intra prediction candidate list (S1530). Specifically, the video encoding device (100) may configure the intra prediction candidate list based on one or more candidate intra prediction pieces of information. According to one embodiment of the present disclosure, when the current block is a chrominance block, the intra prediction candidate list may be configured based on first candidate intra prediction information of a neighboring block of the chrominance block and second candidate intra prediction information of a luma block corresponding to the chrominance block. That is, when the current block is a chrominance block, the intra prediction candidate list may be configured based on intra prediction information of a neighboring block of the current block (i.e., first candidate intra prediction information) and intra prediction information of a corresponding luma block (i.e., second candidate intra prediction information).

[0288] In addition, based on the fact that the second candidate intra prediction information includes linear model information, the intra prediction candidate list may include at least one of a first intra prediction candidate list composed of linear model information or a second intra prediction candidate list composed of information other than the linear model information. That is, when the current block is a chrominance block, the video encoding device (100) may separate the linear model information and the other information to construct two intra prediction candidate lists (i.e., a first intra prediction candidate list and a second intra prediction candidate list). Alternatively, when the current block is a chrominance block, the video encoding device (100) may construct an intra prediction candidate list (i.e., a second intra prediction candidate list) using only the linear model information. Alternatively, when the current block is a chrominance block, the video encoding device (100) may construct an intra prediction candidate list (i.e., a first intra prediction candidate list) using only information other than the linear model information.

[0289] The video encoding device (100) can generate a prediction block of the current block (S1550). Specifically, the video encoding device (100) can generate a prediction block of the current block based on one candidate intra prediction information included in the intra prediction candidate list.

[0290] The video encoding device (100) can encode an intra prediction candidate index (S1570). Here, the intra prediction candidate index may be information indicating one candidate intra prediction information included in an intra prediction candidate list.

[0291] FIG. 16 is a flowchart of a decoding method according to one embodiment of the present disclosure. Referring to FIG. 16, an image decoding device (200) may obtain one or more candidate intra prediction information based on intra prediction information of surrounding blocks of a current block (S1610). Here, the candidate intra prediction information may include at least one of TIMD (Template based intra mode derivation) information, DIMD (Decoder side intra mode derivation) information, linear model information, LIP (Linear interpolation intra prediction) information, PDPC (Position dependent intra prediction) information, MRL (Multi reference line) information, TMRL (Template-based multiple reference line) information, ISP (Intra sub-partition) information, MIP (Matrix-based intra prediction) information, interpolation filter information, MDIS (Mode dependent intra smoothing) information, CIIP (Combined inter and intra prediction) information, SGPM (Spatial geometric partition mode) information, intraTMP (Template matching intra prediction) information, intra prediction directional mode information, extended planar information, intra prediction fusion information, surrounding reference sample characteristic information, or IBC (Intra block copy) information.

[0292] The video decoding device (200) may configure an intra prediction candidate list (S1630). Specifically, the video decoding device (200) may configure the intra prediction candidate list based on one or more candidate intra prediction pieces of information. According to one embodiment of the present disclosure, when the current block is a chrominance block, the intra prediction candidate list may be configured based on first candidate intra prediction information of a neighboring block of the chrominance block and second candidate intra prediction information of a luma block corresponding to the chrominance block. That is, when the current block is a chrominance block, the intra prediction candidate list may be configured based on intra prediction information of a neighboring block of the current block (i.e., first candidate intra prediction information) and intra prediction information of a corresponding luma block (i.e., second candidate intra prediction information).

[0293] In addition, based on the fact that the second candidate intra prediction information includes linear model information, the intra prediction candidate list may include at least one of a first intra prediction candidate list composed of linear model information or a second intra prediction candidate list composed of information other than the linear model information. That is, when the current block is a chrominance block, the image decoding device (200) may separate the linear model information and the other information to construct two intra prediction candidate lists (i.e., a first intra prediction candidate list and a second intra prediction candidate list). Alternatively, when the current block is a chrominance block, the image decoding device (200) may construct an intra prediction candidate list (i.e., a second intra prediction candidate list) using only the linear model information. Alternatively, when the current block is a chrominance block, the image decoding device (200) may construct an intra prediction candidate list (i.e., a first intra prediction candidate list) using only information other than the linear model information.

[0294] The video decoding device (200) can obtain an intra prediction candidate index (S1650). Here, the intra prediction candidate index may be information indicating one candidate intra prediction information included in the intra prediction candidate list.

[0295] The video decoding device (200) can generate a prediction block of the current block (S1670). Specifically, the video decoding device (200) can generate a prediction block of the current block by performing intra prediction based on candidate intra prediction information indicated by the intra prediction candidate index.

[0296] While the exemplary methods of this disclosure are presented as a series of operations for clarity of description, this is not intended to limit the order in which the steps are performed, and individual steps may be performed simultaneously or in different orders, if desired. To implement a method according to this disclosure, additional steps may be included in addition to the steps illustrated, some steps may be excluded and the remaining steps included, or some steps may be excluded and additional steps included.

[0297] In the present disclosure, a video encoding device or video decoding device performing a predetermined operation (step) may perform an operation (step) of checking the conditions or circumstances under which the operation (step) is performed. For example, if it is described that a predetermined operation is performed when a predetermined condition is satisfied, the video encoding device or video decoding device may perform an operation of checking whether the predetermined condition is satisfied and then perform the predetermined operation.

[0298] The various embodiments of the present disclosure are not intended to list all possible combinations but rather to illustrate representative aspects of the present disclosure, and the matters described in the various embodiments may be applied independently or in combination of two or more.

[0299] Additionally, various embodiments of the present disclosure may be implemented by hardware, firmware, software, or a combination thereof. In the case of hardware implementation, the embodiments may be implemented by one or more Application Specific Integrated Circuits (ASICs), Digital Signal Processors (DSPs), Digital Signal Processing Devices (DSPDs), Programmable Logic Devices (PLDs), Field Programmable Gate Arrays (FPGAs), general processors, controllers, microcontrollers, microprocessors, etc.

[0300] In addition, the video decoding device and the video encoding device to which the embodiments of the present disclosure are applied may be included in a multimedia broadcasting transmitting and receiving device, a mobile communication terminal, a home cinema video device, a digital cinema video device, a surveillance camera, a video conversation device, a real-time communication device such as a video communication, a mobile streaming device, a storage medium, a camcorder, a video-on-demand (VoD) service providing device, an OTT (Over the top video) device, an Internet streaming service providing device, a three-dimensional (3D) video device, a video phone video device, and a medical video device, and may be used to process a video signal or a data signal. For example, the OTT (Over the top video) device may include a game console, a Blu-ray player, an Internet-connected TV, a home theater system, a smartphone, a tablet PC, a DVR (Digital Video Recorder), and the like.

[0301] FIG. 17 is a diagram illustrating an example of a content streaming system to which an embodiment according to the present disclosure can be applied.

[0302] As illustrated in FIG. 17, a content streaming system to which an embodiment of the present disclosure is applied may largely include an encoding server, a streaming server, a web server, a media storage, a user device, and a multimedia input device.

[0303] The encoding server compresses content input from multimedia input devices such as smartphones, cameras, and camcorders into digital data, generates a bitstream, and transmits it to the streaming server. Alternatively, if multimedia input devices such as smartphones, cameras, and camcorders directly generate bitstreams, the encoding server may be omitted.

[0304] The above bitstream can be generated by an image encoding method and / or an image encoding device to which an embodiment of the present disclosure is applied, and the streaming server can temporarily store the bitstream during the process of transmitting or receiving the bitstream.

[0305] The streaming server transmits multimedia data to a user device based on a user request via a web server, and the web server can act as an intermediary to inform the user of available services. When a user requests a desired service from the web server, the web server transmits the request to the streaming server, and the streaming server can transmit multimedia data to the user. At this time, the content streaming system may include a separate control server, and in this case, the control server may control commands / responses between each device within the content streaming system.

[0306] The streaming server can receive content from a media repository and / or encoding server. For example, when receiving content from the encoding server, the content can be received in real time. In this case, to provide a smooth streaming service, the streaming server can store the bitstream for a certain period of time.

[0307] Examples of the user devices may include mobile phones, smart phones, laptop computers, digital broadcasting terminals, personal digital assistants (PDAs), portable multimedia players (PMPs), navigation devices, slate PCs, tablet PCs, ultrabooks, wearable devices (e.g., smartwatches, smart glasses, HMDs), digital TVs, desktop computers, digital signage, etc.

[0308] Each server within the above content streaming system can be operated as a distributed server, in which case data received from each server can be processed in a distributed manner.

[0309] The scope of the present disclosure includes software or machine-executable instructions (e.g., operating systems, applications, firmware, programs, etc.) that cause operations according to the methods of various embodiments to be executed on a device or a computer, and a non-transitory computer-readable medium having such software or instructions stored thereon and executable on the device or computer.

[0310] Embodiments according to the present disclosure can be used to encode / decode images.

Claims

1. An image decoding method performed by an image decoding device, A step of obtaining one or more candidate intra prediction information based on intra prediction information of surrounding blocks of the current block; A step of constructing an intra prediction candidate list based on one or more candidate intra prediction information; A step of obtaining an intra prediction candidate index representing one candidate intra prediction information included in the intra prediction candidate list; and A step of generating a prediction block of the current block by performing intra prediction based on the candidate intra prediction information indicated by the intra prediction candidate index, The above candidate intra prediction information includes at least one of TIMD (Template based intra mode derivation) information, DIMD (Decoder side intra mode derivation) information, linear model information, LIP (Linear interpolation intra prediction) information, PDPC (Position dependent intra prediction) information, MRL (multi reference line) information, TMRL (Template-based multiple reference line) information, ISP (Intra sub-partition) information, MIP (Matrix-based intra prediction) information, interpolation filter information, MDIS (Mode dependent intra smoothing) information, CIIP (Combined inter and intra prediction) information, SGPM (Spatial geometric partition mode) information, intraTMP (Template matching intra prediction) information, intra-screen prediction directional mode information, extended planar information, intra-prediction fusion information, surrounding reference sample characteristic information, or IBC (Intra block copy) information. How to decrypt video.

2. In paragraph 1, The above surrounding blocks are determined based on one of template matching, bi-lateral matching, or SATD (Sum of absolute transformed differences). How to decrypt video.

3. In paragraph 1, The above intra prediction candidate index is determined based on one of template matching, bi-lateral matching, or SATD (Sum of absolute transformed differences). How to decrypt video.

4. In paragraph 1, The order of the candidate intra prediction information included in the intra prediction candidate list is re-ordered based on either template matching or bidirectional matching. How to decrypt video.

5. In paragraph 1, The above candidate intra prediction information includes information on whether the candidate intra prediction mode is applied. How to decrypt video.

6. In paragraph 5, The above candidate intra prediction information further includes additional information used in applying the corresponding candidate intra prediction mode. How to decrypt video.

7. In paragraph 6, The above prediction block is generated based on at least one of the candidate intra prediction mode or the additional information. How to decrypt video.

8. In paragraph 1, The number of candidate intra prediction information included in the intra prediction candidate list is determined based on at least one of the size of the current block, the position of a sub-block within the current block, the statistical characteristics of the surrounding blocks, or whether a secondary transformation is used for the current block. How to decrypt video.

9. In paragraph 1, The acquisition order of the above-mentioned surrounding blocks is determined based on at least one of the size of the current block, the position of a sub-block within the current block, the statistical characteristics of the surrounding blocks, or whether a secondary transformation is used for the current block. How to decrypt video.

10. In paragraph 1, The positions of the surrounding blocks are determined based on at least one of the size of the current block, the positions of sub-blocks within the current block, the statistical characteristics of the surrounding blocks, or whether a secondary transformation is used for the current block. How to decrypt video.

11. In paragraph 1, Based on the above current block being a chroma block, the intra prediction candidate list is constructed based on first candidate intra prediction information of a surrounding block of the chroma block and second candidate intra prediction information of a luma block corresponding to the chroma block. How to decrypt video.

12. In paragraph 11, Based on the fact that the second candidate intra prediction information includes the linear model information, the intra prediction candidate list includes at least one of a first intra prediction candidate list composed of the linear model information or a second intra prediction candidate list composed of information other than the linear model information. How to decrypt video.

13. An image encoding method performed by an image encoding device, A step of obtaining one or more candidate intra prediction information based on intra prediction information of surrounding blocks of the current block; A step of constructing an intra prediction candidate list based on one or more candidate intra prediction information; A step of generating a prediction block of a current block based on one candidate intra prediction information included in the intra prediction candidate list; and A step of encoding an intra prediction candidate index representing the above one candidate intra prediction information, The above candidate intra prediction information includes at least one of TIMD (Template based intra mode derivation) information, DIMD (Decoder side intra mode derivation) information, linear model information, LIP (Linear interpolation intra prediction) information, PDPC (Position dependent intra prediction) information, MRL (Multi reference line) information, TMRL (Template-based multiple reference line) information, ISP (Intra sub-partition) information, MIP (Matrix-based intra prediction) information, interpolation filter information, MDIS (Mode dependent intra smoothing) information, CIIP (Combined inter and intra prediction) information, SGPM (Spatial geometric partition mode) information, Intra TMP (Template matching intra prediction) information, Intra prediction directional mode information, extended planar information, Intra prediction fusion information, surrounding reference sample characteristic information, or IBC (Intra block copy) information. Video encoding method.

14. A computer-readable recording medium storing a bitstream generated by the image encoding method of Article 13.

15. A method for transmitting a bitstream generated by an image encoding method, wherein the image encoding method comprises: A step of obtaining one or more candidate intra prediction information based on intra prediction information of surrounding blocks of the current block; A step of constructing an intra prediction candidate list based on one or more candidate intra prediction information; A step of generating a prediction block of a current block based on one candidate intra prediction information included in the intra prediction candidate list; and A step of encoding an intra prediction candidate index representing the above one candidate intra prediction information, The above candidate intra prediction information includes at least one of TIMD (Template based intra mode derivation) information, DIMD (Decoder side intra mode derivation) information, linear model information, LIP (Linear interpolation intra prediction) information, PDPC (Position dependent intra prediction) information, MRL (multi reference line) information, TMRL (Template-based multiple reference line) information, ISP (Intra sub-partition) information, MIP (Matrix-based intra prediction) information, interpolation filter information, MDIS (Mode dependent intra smoothing) information, CIIP (Combined inter and intra prediction) information, SGPM (Spatial geometric partition mode) information, Intra TMP (Template matching intra prediction) information, intra prediction directional mode information, extended planar information, Intra prediction fusion information, surrounding reference sample characteristic information, or IBC (Intra block copy) information. Bitstream transmission method.

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