RU2809033C2 - Method and equipment for image encoding/decoding using quantization matrix and method for bitstream transmission - Google Patents

Abstract

FIELD: encoding/decoding images.

SUBSTANCE: image decoding equipment by means of image decoding equipment configured to obtain quantization mode information for a current block from a bitstream, determining whether or not a quantization matrix is constructed for the current block from a reference quantization matrix based on the quantization mode information, and constructing a quantization matrix for the current block, based on the result of the determination. When the quantization matrix for the current block is constructed from the reference quantization matrix, the quantization matrix for the current block may be constructed based on the identification information of the reference quantization matrix. When the quantization matrix for the current block is not constructed from the reference quantization matrix, the quantization matrix for the current block may be constructed based on the value of the quantization matrix obtained from the bitstream. When the current block is an intra-predicted chrominance block, a quantization matrix for the current block may be constructed only when the size of the current block is larger than 2×2.

EFFECT: increasing the efficiency of encoding/decoding images using a quantization matrix.

12 cl, 24 dwg, 1 tbl

Description

Field of technology to which the invention relates

[1] The present disclosure relates to a method and equipment for encoding/decoding images and to a method for transmitting a bit stream, and more specifically, to a method and equipment for encoding/decoding images using a quantization matrix and to a method for transmitting a bit stream generated by the method/equipment encoding images of the present disclosure.

State of the art

[2] Recently, the demand for high-quality, high-definition images, such as high-definition (HD) images and ultra-high-definition (UHD) images, has been increasing in various fields of technology. As the resolution and quality of image data increases, the amount of transmitted information or bits increases relatively compared to existing image data. Increasing the amount of information or bits transmitted results in increased transmission costs and storage costs.

[3] Accordingly, there is a need for high-performance image compression technology for efficiently transmitting, storing and reproducing information regarding high-quality, high-resolution images.

The essence of the invention

Technical problem

[4] The purpose of the present disclosure is to provide an image encoding/decoding method and equipment with improved encoding/decoding efficiency.

[5] Another object of the present disclosure is to provide an image encoding/decoding method and equipment capable of efficiently signaling a quantization matrix.

[6] Another object of the present disclosure is to provide a method for transmitting a bit stream generated by an image encoding method or equipment according to the present disclosure.

[7] Another object of the present disclosure is to provide a recording medium storing a bitstream generated by an image encoding method or equipment according to the present disclosure.

[8] Another object of the present disclosure is to provide a recording medium storing a bitstream received, decoded, and used to reconstruct an image by the image decoding equipment according to the present disclosure.

[9] The technical problems addressed by the present disclosure are not limited to the above technical problems, and other technical problems not described herein should become apparent to those skilled in the art from the following description.

Technical solution

[10] An image decoding method performed by the image decoding equipment according to an aspect of the present disclosure may comprise obtaining quantization mode information for a current block from a bit stream, determining whether or not a quantization matrix for the current block is constructed from a reference quantization matrix based on the information quantization mode, and constructing a quantization matrix for the current block based on the determination result. Based on the quantization matrix for the current block constructed from the reference quantization matrix, the quantization matrix for the current block can be constructed based on the identification information of the reference quantization matrix. Based on the quantization matrix for the current block not constructed from the reference quantization matrix, the quantization matrix for the current block may be constructed based on the quantization matrix value obtained from the bit stream. Based on the current block being an internally predicted chroma block, a quantization matrix for the current block can be constructed only when the size of the current block is greater than 2×2.

[11] The image decoding equipment according to an aspect of the present disclosure may comprise a storage device and at least one processor. The at least one processor may obtain quantization mode information for a current block from the bit stream, determine whether or not a quantization matrix for the current block is constructed from a reference quantization matrix based on the quantization mode information, and construct a quantization matrix for the current block based on result of the determination. Based on the quantization matrix for the current block constructed from the reference quantization matrix, the quantization matrix for the current block can be constructed based on the identification information of the reference quantization matrix. Based on the quantization matrix for the current block not constructed from the reference quantization matrix, the quantization matrix for the current block may be constructed based on the quantization matrix value obtained from the bit stream. Based on the current block being an internally predicted chroma block, a quantization matrix for the current block can be constructed only when the size of the current block is greater than 2×2.

[12] An image encoding method carried out by image encoding equipment according to an aspect of the present disclosure may comprise encoding quantization mode information for a current block from a bit stream, determining whether or not a quantization matrix is constructed for the current block from a reference quantization matrix based on the information quantization mode, and encoding information regarding the quantization matrix for the current block based on the determination result. Based on the quantization matrix for the current block constructed from the quantization reference matrix, identification information of the quantization reference matrix may be encoded. Based on a quantization matrix for the current block not constructed from a reference quantization matrix, the value of the quantization matrix for the current block may be encoded. Based on the current block being an internally predicted chrominance block, a quantization matrix for the current block can be constructed only when the size of the current block is greater than 2×2.

[13] In addition, the transmission method according to another aspect of the present disclosure may transmit a bit stream generated by the image encoding equipment or the image encoding method of the present disclosure.

[14] In addition, the computer-readable recording medium according to another aspect of the present disclosure can store a bit stream generated by the image encoding equipment or the image encoding method of the present disclosure.

[15] The features briefly summarized above with respect to the present disclosure are merely exemplary aspects of the following detailed description of the present disclosure and do not limit the scope of the present disclosure.

Advantages of the invention

[16] According to the present disclosure, it is possible to provide an image encoding/decoding method and equipment with improved encoding/decoding efficiency.

[17] In addition, according to the present disclosure, it is possible to provide an image encoding/decoding method and equipment capable of encoding/decoding only a quantization matrix having a size larger than a predetermined size.

[18] In addition, according to the present disclosure, it is possible to provide an image encoding/decoding method and equipment capable of differently designing a quantization matrix according to the current block prediction mode and the color component.

[19] In addition, according to the present disclosure, it is possible to provide a method for transmitting a bitstream generated by an image encoding method or equipment according to the present disclosure.

[20] In addition, according to the present disclosure, it is possible to provide a recording medium storing a bit stream generated by the image encoding method or equipment according to the present disclosure.

[21] In addition, according to the present disclosure, it is possible to provide a recording medium storing a bitstream received, decoded, and used to reconstruct an image by the image decoding equipment according to the present disclosure.

[22] Those skilled in the art will appreciate that the advantages that may be achieved through the present disclosure are not limited to those specifically described above, and other advantages of the present disclosure will be more clearly understood from the detailed description.

Brief description of drawings

[23] FIG. 1 is a view schematically showing a video encoding system to which an embodiment of the present disclosure is applicable.

[24] FIG. 2 is a view schematically showing image encoding equipment to which an embodiment of the present disclosure is applicable.

[25] FIG. 3 is a view schematically showing image decoding equipment to which an embodiment of the present disclosure is applicable.

[26] FIG. 4 is a view showing an image segmentation structure according to the embodiment.

[27] FIG. 5A to 5C are views illustrating examples of frame segmentation.

[28] FIG. 6 is a view showing an embodiment of a block segmentation type according to a multi-type tree structure.

[29] FIG. 7 is a view showing a signaling mechanism for blocking information in a quadtree with a nested multi-type tree structure according to the present disclosure.

[30] FIG. 8 is a view showing an example in which a CTU is segmented into multiple CUs by applying a multi-type tree after applying a quadtree.

[31] FIG. 9 shows the redundant partitioning patterns that can occur in binary tree partitioning and ternary tree partitioning.

[32] FIG. 10 is a view illustrating examples in which CU partitioning is limited.

[33] FIG. 11 is a flowchart illustrating a video/image encoding method based on inter-prediction.

[34] FIG. 12 is a view illustrating the configuration of the inter-prediction module 180 according to the present disclosure.

[35] FIG. 13 is a flowchart illustrating a video/image decoding method based on inter-prediction.

[36] FIG. 14 is a view illustrating the configuration of the inter-prediction module 260 according to the present disclosure.

[37] FIG. 15 is a view illustrating an example of sizeId for each size of the quantization matrix.

[38] FIG. 16 is a view illustrating an example of a quantization matrix for a current block designed based on the example of FIG. 15.

[39] FIG. 17 is a flowchart illustrating a quantization matrix encoding method according to an embodiment of the present disclosure.

[40] FIG. 18 is a view illustrating an example of syntax for implementing a quantization matrix encoding method based on the example of FIG. 16.

[41] FIG. 19 is a view illustrating an example of a quantization matrix for a current block according to an embodiment of the present disclosure.

[42] FIG. 20 is a view illustrating an example of syntax for implementing a quantization matrix encoding method based on the example of FIG. 19.

[43] FIG. 21 is a flowchart illustrating a method for decoding a quantization matrix according to an embodiment of the present disclosure.

[44] FIG. 22 is a view showing a content streaming system to which an embodiment of the present disclosure is applicable.

Optimal mode for carrying out the invention

[45] Embodiments of the present disclosure are described in detail hereinafter with reference to the accompanying drawings so that they can be easily implemented by those skilled in the art. However, the present disclosure may be implemented in a variety of forms and is not limited to the embodiments described herein.

[46] In describing the present disclosure, if it is determined that a detailed description of a related known function or construct would cause unnecessary ambiguity to the scope of the present disclosure, the detailed description thereof is omitted. In the drawings, parts not related to the description of the present disclosure are omitted, and like reference numbers are added to like parts.

[47] In the present disclosure, when a component is “connected,” “coupled,” or “linked” to another component, this may include not only a direct connection-based relationship, but also an indirect connection-based relationship in which an intermediate component is present. In addition, when a component “includes” or “has” other components, it means that other components may be additionally included, not the exclusion of other components, unless otherwise noted.

[48] In the present disclosure, the terms “first”, “second”, etc. may be used only for the purpose of distinguishing one component from other components and does not limit the order or importance of the components unless otherwise noted. Accordingly, within the scope of the present disclosure, a first component in one embodiment may be referred to as a “second component” in another embodiment, and likewise, a second component in one embodiment may be referred to as a “first component” in another embodiment.

[49] In the present disclosure, components that are different from each other are intended to clearly describe each feature and do not mean that the components are necessarily separate. Thus, multiple components may be integrated and implemented in a single hardware or software module, or a single component may be distributed and implemented in multiple hardware or software modules. Therefore, even if not stated otherwise, such embodiments in which components are integrated or a component is distributed are also included within the scope of the present disclosure.

[50] In the present disclosure, the components described in the various embodiments do not necessarily mean essential components, and some components may be optional components. Accordingly, an embodiment consisting of a subset of the components described in the embodiment is also included within the scope of the present disclosure. In addition, embodiments including other components in addition to the components described in the various embodiments are included within the scope of the present disclosure.

[51] The present disclosure relates to image encoding and decoding, and the terms used in the present disclosure may have a general meaning commonly used in the art to which the present disclosure pertains if not defined for the first time in the present disclosure.

[52] In the present disclosure, "frame" generally means a unit representing one image at a particular time period, and a slice/tile is an encoding unit constituting part of a frame, and one frame may consist of one or more slices/ tiles In addition, a slice/tile may include one or more coding tree units (CTUs).

[53] In the present disclosure, "pixel" or "pixel" can mean the smallest unit constituting one frame (or image). In addition, "sample" can be used as a term corresponding to a pixel. A sample may generally represent a pixel or a pixel value, and may represent only a pixel/pixel value of a luma component or only a pixel/pixel value of a chrominance component.

[54] In the present disclosure, a "unit" may represent a basic unit of image processing. The unit may include at least one of a specific frame area and information associated with the area. The unit may be used interchangeably with terms such as "sample array", "block" or "zone" in some cases. In general, an MxN block may include samples (or arrays of samples) or a set (or array) of transform coefficients of M columns and N rows.

[55] In the present disclosure, "current block" may mean one of "current encoding block", "current encoding unit", "target encoding block", "target decoding block" or "target processing block". When prediction is performed, "current block" may mean "current prediction block" or "target prediction block". When transform (inverse transform)/quantization (dequantization) is performed, "current block" can mean "current transform block" or "transform target block". When filtering is performed, "current block" can mean "target filtering block".

[56] In addition, in the present disclosure, "current block" may mean a block including both a luminance component block and a chroma component block, or a "current block luminance block" unless explicitly stated in as a block of color signals. The chroma component block of the current block may be expressed by including an explicit description of the luma component block, such as "luminance block" or "current luma block". In addition, the chrominance component block of the current block may be explicitly expressed by including an explicit description of the chrominance component block, such as “chrominance block” or “current chrominance block”.

[57] In the present disclosure, the terms "/" and "," are to be interpreted to indicate "and/or". For example, the expression "A/B" and "A, B" can mean "A and/or B". Additionally, "A/B/C" and "A/B/C" may mean "at least one of A, B and/or C".

[58] In the present disclosure, the term “or” should be interpreted to indicate “and/or.” For example, the expression "A or B" may contain 1) only "A", 2) only "B", and/or 3) "both A and B". In other words, in the present disclosure, the term “or” is to be interpreted as indicating “in addition or alternatively.”

[59] Video Coding System Overview

[60] FIG. 1 is a view showing a video coding system to which an embodiment of the present disclosure is applicable.

[61] The video encoding system according to an embodiment may include encoding equipment 10 and decoding equipment 20. The encoding equipment 10 may deliver encoded information or video and/or image data to the decoding equipment 20 in the form of a file or streaming via a digital storage medium or a network.

[62] The encoding equipment 10 according to an embodiment may include a video source generator 11, an encoding unit 12, and a transmitter 13. The decoding equipment 20 according to an embodiment may include a receiver 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 transmitter 13 may be included in the encoding module 12. The receiver 21 may be included in the decoding module 22. The rendering module 23 may include a display, and the display may be configured as a separate device or an external component.

[63] The video source generator 11 may obtain video/image through a video/image capturing, synthesizing, or shaping process. The video source generator 11 may include a video/image capture device and/or a video/image generation device. The video/image capturing device may include, for example, one or more cameras, video/image archives including previously captured video/images, and the like. The video/image generating apparatus may include, for example, computers, tablet computers and smartphones and may (electronically) generate video/images. For example, a virtual video/image may be generated via a computer or the like. In this case, the video/image capturing process can be replaced by the associated data generation process.

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

[65] The transmitter 13 may transmit encoded information or video/image data output in the form of a bit stream to the receiver 21 of the decoding equipment 20 via 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, and the like. The transmitter 13 may include an element for generating a multimedia file through a predefined file format and may include an element for transmission through a broadcast/communications network. The receiver 21 may retrieve/receive a bit stream from the storage medium or network and transmit the bit stream to the decoding unit 22.

[66] The decoding unit 22 can decode the video/image by performing a series of procedures such as dequantization, deconversion and prediction corresponding to the operation of the encoding unit 12.

[67] The rendering unit 23 may prepare a decoded video/image by rendering. The video/image prepared by rendering can be displayed through the display.

[68] General introduction to image encoding equipment

[69] FIG. 2 is a view schematically showing image encoding equipment to which an embodiment of the present disclosure is applicable.

[70] As shown in FIG. 2, the image encoding equipment 100 may include an image segmentation unit 110, a subtractor 115, a converter 120, a quantizer 130, a dequantizer 140, an inverse converter 150, an adder 155, a filter 160, a memory 170, an inter-prediction unit 180, an intra-prediction unit 185 and an entropy encoder 190. The inter-prediction module 180 and the intra-prediction module 185 may be collectively referred to as a “prediction module”. Converter 120, quantizer 130, dequantizer 140, and inverse converter 150 may be included in the residual processor. The residual processor may further include a subtractor 115.

[71] All or at least a portion of the plurality of components configuring image encoding equipment 100 may be configured by a single hardware component (eg, an encoder or processor) in some embodiments. In addition, storage device 170 may include a decoded frame buffer (DPB) and may be configured with a digital storage medium.

[72] The image segmentation module 110 may segment an input image (either a frame or a movie frame) input to the image encoding equipment 100 into one more processing unit. For example, the processing unit may be called a "coding unit (CU)". A coding unit may be obtained by recursively segmenting a coding tree unit (CTU) or largest coding unit (LCU) according to a quadtree, binary tree, and ternary tree (QT/BT/TT) structure. For example, one coding unit may be segmented into multiple coding units of greater depth based on a quadtree structure, a binary tree structure, and/or a ternary structure. To segment a coding unit, a quadtree structure may first be applied, and subsequently a binary tree structure and/or a ternary structure may be applied. The encoding procedure of the present disclosure may be performed based on a final encoding unit that is no longer segmented. The largest coding unit may be used as the final coding unit, or a coding unit of greater depth obtained by segmenting the largest coding unit may be used as the final coding unit. Here, the encoding procedure may include a prediction, transformation and reconstruction procedure, which is described below. As another example, the processing unit of the encoding procedure may be a prediction unit (PU) or a transformation unit (TU). The prediction unit and the transformation unit may be split or segmented from the final encoding unit. The prediction unit may be a sample prediction unit, and the transformation unit may be a unit for extracting a transformation coefficient and/or a unit for extracting a residual signal from the transformation coefficient.

[73] The prediction module (inter-prediction module 180 or intra-prediction module 185) may perform prediction regarding a block to be processed (the current block) and generate a predicted block including prediction samples for the current block. The prediction module may determine whether intra prediction or inter prediction is applied based on the current block or CU. The prediction module may generate various information related to prediction of the current block and transmit the generated information to the entropy encoder 190. Information regarding the prediction may be encoded in the entropy encoder 190 and output in the form of a bitstream.

[74] The intra prediction module 185 may predict the current block by reference to the samples in the current frame. Samples for reference may be located in the surroundings of the current block or may be spaced apart according to an intra-prediction mode and/or intra-prediction technology. The intra prediction modes may include a plurality of non-directional modes and a plurality of directed modes. The omnidirectional mode may include, for example, DC mode and planar mode. The directional mode may include, for example, 33 directional prediction modes or 65 directional prediction modes according to the granularity of the prediction direction. However, this is merely an example; more or less directional prediction modes may be used depending on the setting. The intra prediction module 185 may determine the prediction mode applied to the current block by using the prediction mode applied to the adjacent block.

[75] The inter-prediction unit 180 may extract a predicted block for the current block based on a reference block (an array of reference samples) indicated by a motion vector for the reference frame. In this case, in order to reduce the amount of motion information transmitted in the inter-prediction mode, the motion information may be predicted in units of blocks, sub-blocks, or samples based on the correlation of the motion information between a neighboring block and the current block. The motion information may include a motion vector and a reference frame index. The motion information may further include inter-prediction direction information (L0-prediction, L1-prediction, bi-prediction, etc.). In the case of inter-prediction, the neighbor block may include a spatial neighbor block present in the current frame and a temporal neighbor block present in the reference frame. The reference frame including the reference block and the reference frame including the temporary adjacent block may be identical or different. A temporary neighbor block may be referred to as a "co-located reference block", "co-located CU (colCU)", or the like. A reference frame including a temporary adjacent block may be referred to as a "co-located frame (colPic)". For example, the inter-prediction module 180 may configure a list of motion information candidates based on neighboring blocks and generate information indicating which candidate is used to retrieve the motion vector and/or reference frame index of the current block. Mutual prediction can be performed based on different prediction modes. For example, in the case of the skip mode and the merge mode, the inter-prediction unit 180 may use the motion information of a neighboring block as the motion information of the current block. In the case of the skip mode, unlike the combining mode, the residual signal may not be transmitted. In the case of the motion vector prediction (MVP) mode, the motion vector of an adjacent block can be used as a motion vector predictor, and the motion vector of the current block can be signaled by encoding the motion vector difference and an indicator for the motion vector predictor. The motion vector difference may mean the difference between the motion vector of the current block and the motion vector predictor.

[76] The prediction module can generate a prediction signal based on various prediction methods and prediction technologies described below. For example, the prediction module may not only apply intra-prediction or inter-prediction, but also simultaneously apply both intra-prediction and inter-prediction to predict the current block. A prediction method that simultaneously uses both intra prediction and inter prediction to predict the current block may be called "combined inter and intra prediction (CIIP)". In addition, the prediction module can perform intra-block copying (IBC) to predict the current block. In-block copying can be used to encode game image/video content and the like, such as screen content encoding (SCC). IBC is a method of predicting the current frame using a previously reconstructed reference block in the current frame at a location spaced from the current block by a predetermined distance. When IBC is applied, the location of the reference block in the current frame can be encoded as a vector (block vector) corresponding to a predetermined distance. IBC essentially performs prediction within the current frame, but can be performed similarly to inter-prediction in that the reference block is retrieved within the current frame. Thus, the IBC may use at least one of the inter-prediction technologies described in the present disclosure.

[77] The prediction signal generated by the prediction module can be used to generate a reconstructed signal or generate a residual signal. The subtractor 115 may generate a residual signal (a residual block or an array of residual samples) by subtracting a prediction signal (a prediction block or an array of prediction samples) output from the prediction module from an input image signal (a source block or an array of original samples). The generated residual signal can be transmitted to the converter 120.

[78] Converter 120 can generate conversion coefficients by applying conversion technology to the residual signal. For example, the transform technology may include at least one of a discrete cosine transform (DCT), a discrete sine transform (DST), a Karhunen-Loeve transform (KLT), a graph-based transform (GBT), or a conditionally nonlinear transform (CNT). ). Here, GBT means a graph-derived transformation when the relationship information between pixels is represented by the graph. CNT means the transformation obtained from the prediction signal generated using all the previously reconstructed pixels. In addition, the conversion process can be applied to square pixel blocks that are identical in size, or can be applied to blocks that are variable in size rather than square.

[79] Quantizer 130 may quantize the transform coefficients and pass them to entropy encoder 190. Entropy encoder 190 may encode the quantized signal (information regarding the quantized transform coefficients) and output a bit stream. Information regarding the quantized transform coefficients may be referred to as "residual information". Quantizer 130 may re-arrange the quantized transform coefficients in block form into one-dimensional vector form based on the scan order of the coefficients, and generate information regarding the quantized transform coefficients based on the quantized transform coefficients in one-dimensional vector form.

[80] The entropy encoder 190 may implement various encoding techniques, such as, for example, exponential Golomb coding, context adaptive variable length coding (CAVLC), context adaptive binary arithmetic coding (CABAC), and the like. Entropy encoder 190 may encode information needed to reconstruct video/images other than quantized transform coefficients (eg, syntax element values, etc.), together or separately. Encoded information (eg, encoded video/image information) may be transmitted or stored in network abstraction layer (NAL) units in the form of a bit stream. The video/image information may further include information regarding various parameter sets, such as an adaptation parameter set (APS), a frame parameter set (PPS), a sequence parameter set (SPS), or a video parameter set (VPS). In addition, the video/image information may further include general restriction information. The signaling information, transmission information, and/or syntax elements described in the present disclosure may be encoded through the encoding procedure described above and included in the bitstream.

[81] The bitstream may be transmitted over a network or may be stored on a digital storage medium. The network may include a broadcast network and/or a communications network, and the digital storage medium may include various storage media such as USB, SD, CD, DVD, Blu-Ray, HDD, SSD, and the like. A transmitter (not shown) transmitting the signal output from the entropy encoder 190 and/or a storage module (not shown) storing the signal may be included as an internal/external element of the encoding equipment 100, and alternatively, the transmitter may be included in the entropy encoder 190 .

[82] The quantized transform coefficients output from quantizer 130 can be used to generate a residual signal. For example, a residual signal (residual block or residual samples) may be recovered by applying dequantization and inverse transform to the quantized transform coefficients via dequantizer 140 and inverse transformer 150.

[83] An adder 155 adds the reconstructed residual signal with the prediction signal output from the inter-prediction module 180 or the intra-prediction module 185 so as to generate a reconstructed signal (reconstructed frame, reconstructed block, reconstructed sample array). If there is no remainder for a block to be processed, for example in a case in which the skip mode is applied, the predicted block can be used as a reconstructed block. The adder 155 may be referred to as a "recovery module" or a "recovered block generator." The generated reconstructed signal can be used to internally predict the next block to be processed in the current frame, and can be used to inter-predict the next frame through filtering, as described below.

[84] Filter 160 may enhance the subjective/objective quality of images by applying filtering to the reconstructed signal. For example, filter 160 may generate a modified reconstructed frame by applying various filtering techniques to the reconstructed frame and store the modified reconstructed frame in storage device 170, namely, a DPB of storage device 170. Various filtering techniques may include, for example, deblocking filtering. , filtering based on sampled adaptive offset, adaptive loop filter, bilateral filter, etc. The filter 160 may generate various filtering-related information and transmit the generated information to the entropy encoder 190, as described below in the description of each filtering method. Information associated with filtering may be encoded by entropy encoder 190 and output in the form of a bit stream.

[85] The modified reconstructed frame transferred to the storage device 170 can be used as a reference frame in the inter-prediction module 180. When mutual prediction is applied through the image encoding equipment 100, prediction mismatch between the image encoding equipment 100 and the image decoding equipment can be eliminated, and encoding efficiency can be improved.

[86] The DPB of the storage device 170 may store the modified reconstructed frame for use as a reference frame in the inter-prediction module 180 . The storage device 170 may store block motion information from which motion information in the current frame is retrieved (or encoded) and/or motion information of blocks in a frame that have already been reconstructed. The stored motion information may be transmitted to the inter-prediction unit 180 and used as spatial neighbor block motion information or temporal neighbor block motion information. Memory 170 may store reconstructed samples of reconstructed blocks in the current frame and may transmit reconstructed samples to intra prediction module 185.

[87] General introduction to image decoding equipment

[88] FIG. 3 is a view schematically showing image decoding equipment to which an embodiment of the present disclosure is applicable.

[89] As shown in FIG. 3, the image decoding equipment 200 may include an entropy decoder 210, a dequantizer 220, an inverse converter 230, an adder 235, a filter 240, a memory 250, an inter-prediction unit 260, and an intra-prediction unit 265. The inter-prediction module 260 and the intra-prediction module 265 may be collectively referred to as a “prediction module”. A dequantizer 220 and an inverse converter 230 may be included in the residual processor.

[90] All or at least a portion of the plurality of components configuring the image decoding equipment 200 may be configured by a hardware component (eg, a decoder or processor) according to an embodiment. In addition, storage device 250 may include a decoded frame buffer (DPB) or may be configured with a digital storage medium.

[91] The image decoding equipment 200, which receives the bit stream including video/image information, can reconstruct the image by performing a process corresponding to the process performed by the image encoding equipment 100 in FIG. 2. For example, the image decoding equipment 200 may perform decoding using a processing unit used in the image encoding equipment. Thus, a decoding processing unit, for example, may be an encoding unit. A coding unit may be obtained by segmenting a coding tree unit or a largest coding unit. The reconstructed image signal decoded and output by the decoding equipment 200 can be reproduced by the playback equipment.

[92] The image decoding equipment 200 may receive a signal output from the image encoding equipment of FIG. 2 in the form of a bitstream. The received signal may be decoded through entropy decoder 210. For example, entropy decoder 210 may parse the bitstream to extract information (eg, video/image information) needed to reconstruct images (or reconstruct frames). The video/image information may further include information regarding various parameter sets, such as an adaptation parameter set (APS), a frame parameter set (PPS), a sequence parameter set (SPS), or a video parameter set (VPS). In addition, the video/image information may further include general restriction information. The image decoding equipment may further decode the frame based on information regarding the parameter set and/or general constraint information. The signaling/receiving information and/or syntax elements described in the present disclosure may be decoded by a decoding procedure and obtained from the bit stream. For example, entropy decoder 210 decodes information in a bitstream based on an encoding method, such as exponential Golomb, CAVLC, or CABAC encoding, and the output values of the syntax elements required for image reconstruction and the quantized values of the transform coefficients for the remainder. More specifically, the entropy CABAC decoding method may take a resolution element corresponding to each syntax element in the bitstream, determine a context model using information of a target decoding syntax element, decoding information of an adjacent block and a target decoding block, or information of a symbol/resolution element decoded on a previous one. stage, and perform arithmetic decoding for the resolution element by predicting the probability of occurrence of the permission element according to the determined context model and generating a symbol corresponding to the meaning of each syntactic element. In this case, the entropy CABAC decoding method can update the context model by using the decoded symbol/grant element information for the context model of the next symbol/grant element after determining the context model. The prediction-related information from the information decoded by the entropy decoder 210 may be provided to the prediction module (inter-prediction module 260 and intra-prediction module 265), and the residual value for which entropy decoding is performed in the entropy decoder 210, i.e. quantized conversion coefficients and related parameter information may be input to the dequantizer 220. In addition, information regarding filtering from information decoded by the entropy decoder 210 may be provided to the filter 240. Meanwhile, a receiver (not shown) for receiving a signal output from the equipment image encoding device may be further configured as an internal/external element of image decoding equipment 200, or the receiver may be a component of entropy decoder 210.

[93] Meanwhile, the image decoding equipment according to the present disclosure may be referred to as “video/image/frame decoding equipment.” The image decoding equipment can be classified into an information decoder (video/image/frame information decoder) and a sample decoder (video/image/frame sample decoder). The information decoder may include an entropy decoder 210. The sample decoder may include at least one of a dequantizer 220, an inverse converter 230, an adder 235, a filter 240, a memory 250, an inter-prediction module 260, or an intra-prediction module 265.

[94] Dequantizer 220 may dequantize the quantized transform coefficients and output the transform coefficients. Dequantizer 220 may re-arrange the quantized transform coefficients in the form of a two-dimensional block. In this case, rearrangement may be performed based on the order of coefficient scanning performed in the image encoding equipment. Dequantizer 220 may perform dequantization on the quantized transform coefficients by using a quantization parameter (eg, quantization step size information) and obtain the transform coefficients.

[95] The inverse converter 230 may inversely convert the transform coefficients to obtain a residual signal (residual block, residual sample array).

[96] The prediction module may perform prediction for the current block and may generate a predicted block including prediction samples for the current block. The prediction module may determine whether intra prediction or inter prediction is applied to the current block based on the prediction information output from the entropy decoder 210, and may determine a particular intra/inter prediction mode.

[97] Identical to that described in the prediction module of the image encoding equipment 100, the prediction module can generate a prediction signal based on various prediction methods (techniques), which are described below.

[98] Intra prediction module 265 may predict the current block by reference to samples in the current frame. The description of the intra prediction module 185 applies equally to the intra prediction module 265.

[99] The inter-prediction module 260 may extract a predicted block for the current block based on a reference block (an array of reference samples) indicated by a motion vector for the reference frame. In this case, in order to reduce the amount of motion information transmitted in the inter-prediction mode, the motion information may be predicted in units of blocks, sub-blocks, or samples based on the correlation of the motion information between a neighboring block and the current block. The motion information may include a motion vector and a reference frame index. The motion information may further include inter-prediction direction information (L0-prediction, L1-prediction, bi-prediction, etc.). In the case of inter-prediction, the neighbor block may include a spatial neighbor block present in the current frame and a temporal neighbor block present in the reference frame. For example, the inter-prediction module 260 may configure a motion information candidate list based on neighboring blocks and extract the current block's motion vector and/or reference frame index based on the received candidate selection information. The inter-prediction may be performed based on various prediction modes, and the information regarding the prediction may include information indicating the inter-prediction mode for the current block.

[100] The adder 235 can generate a reconstructed signal (recovered frame, reconstructed block, reconstructed sample array) by adding the resulting residual signal with a prediction signal (predicted block, predicted sample array) output from a prediction module (including inter-prediction module 260 and /or internal prediction module 265). If there is no remainder for a block to be processed, for example when a skip mode is applied, the predicted block can be used as the reconstructed block. The description of adder 155 is equally applicable to adder 235. Adder 235 may be referred to as a “recovery module” or a “recovered block generator.” The generated reconstructed signal can be used to internally predict the next block to be processed in the current frame, and can be used to inter-predict the next frame through filtering, as described below.

[101] Filter 240 may enhance the subjective/objective quality of images by applying filtering to the reconstructed signal. For example, filter 240 may generate a modified reconstructed frame by applying various filtering techniques to the reconstructed frame and store the modified reconstructed frame in storage device 250, namely, a DPB of storage device 250. Various filtering techniques may include, for example, deblocking filtering. , filtering based on sampled adaptive offset, adaptive loop filter, bilateral filter, etc.

[102] The (modified) reconstructed frame stored in the DPB of the storage device 250 can be used as a reference frame in the inter-prediction unit 260. Memory 250 may store block motion information from which motion information in the current frame is retrieved (or decoded) and/or motion information of blocks in a frame that have already been reconstructed. The stored motion information may be transmitted to the inter-prediction unit 260 so that it is used as spatial neighbor block motion information or temporal neighbor block motion information. Memory 250 may store reconstructed samples of reconstructed blocks in the current frame and transmit the reconstructed samples to intra prediction module 265.

[103] In the present disclosure, the embodiments described in the filter 160, the inter-prediction module 180, and the intra-prediction module 185 of the image encoding equipment 100 may be equally or correspondingly applied to the filter 240, the inter-prediction module 260, and the intra-prediction module 265 image decoding equipment 200.

[104] General introduction to image segmentation

[105] The video/image encoding method according to the present disclosure can be implemented based on an image segmentation structure as follows. In particular, the prediction, residual processing ((in)transformation, (de)-quantization, etc.), syntax element encoding and filtering procedures described below can be performed on a CTU, CU (and/or TU, PU) basis ), extracted based on the image segmentation structure. The image may be segmented in units of blocks, and the block segmentation procedure may be performed in the image segmentation unit 110 of the encoding equipment. Segmentation-related information may be encoded by entropy encoder 190 and transmitted to decoding equipment in the form of a bit stream. The entropy decoder 210 of the decoding equipment can extract the block segmentation structure of the current frame based on the segmentation-related information obtained from the bit stream, and based on this, can perform a series of procedures (eg, prediction, residual processing, block/frame reconstruction, in-loop filtering, and etc.) for decoding images. The CU size and TU size may be identical, or multiple TUs may be present in a CU area. Meanwhile, the CU size may generally represent the CB size of the component (sample) luminance signals. The TU size may generally represent the TB size of the component (sample) luminance signals. The CB or TB size of the chroma component samples may be extracted based on the CB or TB size of the luminance component samples according to the component ratio according to the chrominance signal format (color format, e.g., 4:4:4, 4:2 :2, 4:2:0, etc.) frame/image. The TU size may be retrieved based on maxTbSize indicating the maximum TB size available. For example, when the CU size exceeds maxTbSize, a plurality of TUs (TB) with maxTbSize may be retrieved from the CU, and conversion/reconversion may be performed in TU units (TB). In addition, for example, when applying intra prediction, the intra prediction mode/type may be retrieved in CU (or CB) units, and the procedure for retrieving adjacent reference samples and generating prediction samples can be performed in TU (or TB) units. In this case, one or multiple TUs (or TBs) may be present in one CU (or CB) zone, and, in this case, multiple TUs or (TBs) may share an identical intra prediction mode/type.

[106] In addition, when encoding and decoding images according to the present disclosure, the image processing module may have a hierarchical structure. For example, one frame may be segmented into one or more tiles or groups of tiles. One tile group may include one or more tiles. One tile may include one or more CTUs. A CTU may be segmented into one or more CUs as described above. A tile may consist of a rectangular area including CTUs collected in a particular row and a particular column in a frame. A group of tiles may include an integer number of tiles according to a raster scan of the tiles. The tile group header may signal information/parameters applicable to the corresponding tile group. When the encoding/decoding hardware has a multi-core processor, the encoding/decoding procedure for a tile or group of tiles can be performed in parallel. Here, the tile group may have one of the types of tile groups including an internal (I) tile group, a predictive (P) tile group, and a bipredictive (B) tile group. For blocks in an I-tile group, inter-prediction may not be used, and only intra-prediction may be used for prediction. Of course, even in this case, the original sample value may be encoded and signaled without prediction. For blocks in a P-tile group, intra-forecasting or inter-forecasting can be used, and only uni-forecasting can be used in inter-forecasting. Meanwhile, for blocks in a B-tile group, intra-forecasting or inter-forecasting can be used, and up to bi-forecasting can be used when inter-forecasting is used.

[107] In encoding equipment, the tile/group of tiles, the slice and the size of the maximum and minimum encoding unit may be determined according to the characteristics (eg, resolution) of the image and taking into account the efficiency of encoding or parallel processing, and information therefor or information capable of retrieval thereof, may be included in the bit stream.

[108] In decoding equipment, information indicating whether a slice of the current frame, tile/tile group, or CTU in a tile is segmented into a plurality of encoding units may be obtained. When this information is received (transmitted) only under specific conditions, efficiency can increase.

[109] A slice header or tile group header (tile group header syntax) may include information/parameters typically applicable to a group of slices or tiles. APS (APS Syntax) or PPS (PPS Syntax) may include information/parameters typically applicable to one or more frames. SPS (SPS syntax) may include information/parameters typically applicable to one or more sequences. VPS (VPS syntax) may include information/parameters generally applicable to the entire video. In the present disclosure, the high-level syntax may include at least one of APS syntax, PPS syntax, SPS syntax, or VPS syntax.

[110] In addition, for example, information regarding segmentation and construction of a tile/group of tiles may be constructed in the encoding stage via high-level syntax and transmitted to the decoding equipment in the form of a bit stream.

[111] Segmentation structure

[112] Frames may be segmented into a sequence of coding tree units (CTUs). A CTU may correspond to a coding tree block (CTB). Alternatively, the CTU may include a luma sample coding tree block and two coding tree blocks of corresponding chrominance samples. For example, for a frame that contains three sample arrays, the CTU may include a block of NxN luma samples and two corresponding blocks of chroma samples. Fig. 4 shows an example in which a frame is segmented into CTUs.

[113] The maximum allowed CTU size for encoding and prediction may be different from the maximum allowed CTU size for translation. For example, even when the maximum luminance block size of a CTU for conversion is 64×64, the maximum luminance block size of a CTU for encoding and prediction may be 128×128.

[114] In addition, a frame may be segmented into one or more rows of tiles and one or more columns of tiles. A tile can be a sequence of CTUs covering a rectangular area in a frame.

[115] A tile may be segmented into one or more bricks, and each brick may consist of multiple CTU rows within the tile. In the present disclosure, a tile that is not segmented into a plurality of bricks may be referred to as a "brick".

[116] A slice may include many tiles in a frame or many bricks in a tile. Two slicing modes can be supported. One may be a raster scan-based slicing mode, and the other may be a rectangular slicing mode.

[117] In raster slicing mode, a slice may include multiple consecutive tiles in a frame according to the raster scan order. In the present disclosure, a slice according to a raster scan-based slicing mode may be referred to as a “raster scan-based slice.”

[118] In rectangular slice mode, a slice can include multiple bricks constructing a rectangular area in the frame. In the present disclosure, a slice according to the rectangular slice division mode may be referred to as a "rectangular slice". A plurality of bricks included in a rectangular slice may exist according to the raster scanning order of the slice bricks.

[119] FIG. 5A to 5C are views illustrating examples of frame segmentation.

[120] First, referring to FIG. 5A, in the raster scan slicing mode, a frame can be segmented into 12 tiles and three raster scan slices.

[121] Referring to FIG. 5B, in the rectangular slice mode, a frame can be segmented into 24 tiles (ie, six rows of tiles and four columns of tiles) and nine rectangular slices.

[122] Referring to FIG. 5C, a frame can be segmented into four tiles (i.e., two rows of tiles and two columns of tiles), 11 bricks (i.e., one top left brick, five top right bricks, two left bottom bricks, and three bottom right bricks). brick) and into four rectangular cuts.

[123] CTU segmentation overview

[124] As described above, a coding unit (CU) can be obtained by recursively segmenting a coding tree unit (CTU) or a largest coding unit (LCU) according to a quadtree/binary tree/ternary tree (QT/BT/TT) structure. For example, a CTU may first be segmented into quadtree structures. Thereafter, the leaf nodes of the quadtree structure can be further segmented by a multi-type tree structure.

[125] Quadtree segmentation means that the current CU (or CTU) is segmented equally into four. Through segmentation according to the quadtree, the current CU can be segmented into four CUs having identical width and identical height. When the current CU is no longer segmented into a quadtree structure, the current CU corresponds to a leaf node of the quadtree structure. The CU corresponding to the leaf node of the quadtree structure can no longer be segmented and can be used as the final encoding unit described above. Alternatively, the CU corresponding to a leaf node of the quadtree structure may further be segmented by a multi-type tree structure.

[126] FIG. 6 is a view showing an embodiment of a block segmentation type according to a multi-type tree structure. Segmentation according to a multi-type tree structure may include two types of partitioning according to a binary tree structure and two types of partitioning according to a ternary tree structure.

[127] Two types of partitioning according to the binary tree structure may include vertical binary partitioning (SPLIT_BT_VER) and horizontal binary partitioning (SPLIT_BT_HOR). Vertical binary splitting (SPLIT_BT_VER) means that the current CU is split equally in half in the vertical direction. As shown in FIG. 5, through vertical binary partitioning, two CUs having a height identical to the height of the current CU and having a width that is half the width of the current CU can be formed. Horizontal binary splitting (SPLIT_BT_HOR) means that the current CU is split equally in half in the horizontal direction. As shown in FIG. 5, through horizontal binary partitioning, two CUs having a height that is half the height of the current CU and having a width identical to the width of the current CU can be formed.

[128] Two types of partitioning according to the ternary tree structure may include vertical ternary partitioning (SPLIT_TT_VER) and horizontal ternary partitioning (SPLIT_TT_HOR). In vertical ternary splitting (SPLIT_TT_VER), the current CU is split in the vertical direction in a ratio of 1:2:1. As shown in FIG. 5, through vertical ternary partitioning, two CUs having a height identical to the height of the current CU and having a width that is 1/4 of the width of the current CU, and a CU having a height identical to the height of the current CU and having a width that is half the width of the current CU. In horizontal ternary splitting (SPLIT_TT_HOR), the current CU is split horizontally in a ratio of 1:2:1. As shown in FIG. 5, through horizontal ternary partitioning, two CUs having a height that is 1/4 of the height of the current CU and having a width identical to the width of the current CU, and a CU having a height that is half the height of the current CU and having width identical to the width of the current CU.

[129] FIG. 7 is a view showing a signaling mechanism for blocking information in a quadtree with a nested multi-type tree structure according to the present disclosure.

[130] Here, the CTU is treated as the root node of a quadtree and is segmented for the first time into a quadtree structure. Information (eg, qt_split_flag) indicating whether or not quadtree splitting is performed for the current CU (CTU or QT_node) is signaled. For example, when qt_split_flag has the first value (for example, "1"), the current CU can be segmented into a quadtree. In addition, when qt_split_flag has a second value (for example, "0"), the current CU is not split into the quadtree, but becomes a leaf node (QT_leaf_node) of the quadtree. Each quadtree leaf node can then be further segmented into multi-type tree structures. Thus, a quadtree leaf node can become a node (MTT_node) of a multi-type tree. In a multi-type tree structure, the first flag (eg, Mtt_split_cu_flag) is signaled to indicate whether or not the current node is further segmented. If the corresponding node is further split (eg, if the first flag is 1), a second flag (eg, Mtt_split_cu_vertical_flag) may be signaled to indicate the direction of the split. For example, the split direction may be a vertical direction if the second flag is 1, and may be a horizontal direction if the second flag is 0. A third flag (for example, Mtt_split_cu_binary_flag) may then be signaled to indicate what represents the split type is a binary partition type or a ternary partition type. For example, the partition type may be a binary partition-based type when the third flag is 1, and may be a ternary partition-based type when the third flag is 0. A node of a multi-type tree obtained by a binary partition or a ternary partition may further be segmented into multi-type tree structures. However, a multi-type tree node may not be segmented into quadtree structures. If the first flag is 0, the corresponding multi-type tree node is no longer split, but becomes a leaf node (MTT_leaf_node) of the multi-type tree. The CU corresponding to a leaf node of a multi-type tree can be used as the final encoding unit described above.

[131] Based on mtt_split_cu_vertical_flag and mtt_split_cu_binary_flag, the multi-tree split mode (MttSplitMode) of the CU can be retrieved as shown in Table 1 below. In the following description, the multi-tree split mode may be called “multi-tree split type” or "partition type".

[132]

Table 1 MttSplitMode mtt_split_cu_vertical_flag mtt_split_cu_binary_flag SPLIT_TT_HOR 0 0 SPLIT_BT_HOR 0 1 SPLIT_TT_VER 1 0 SPLIT_BT_VER 1 1

[133] FIG. 8 is a view showing an example in which a CTU is segmented into multiple CUs by applying a multi-type tree after applying a quadtree. In fig. 8, bold block edges 810 represent quadtree-based segmentation, and remaining block edges 820 represent multi-tree segmentation. The CU may correspond to a coding block (CB). In an embodiment, the CU may include a luma sample encoder and two chroma sample encoders corresponding to the luma samples.

[134] The CB or TB size of the chrominance signal components may be extracted based on the CB or TB size of the luminance signal components according to the component ratio according to the color format (chrominance signal format, e.g., 4:4:4, 4:2:2, 4:2:0, etc.) frame/image. In the case of a 4:4:4 color format, the CB/TB size of the chrominance signal components may be set to be equal to the CB/TB size of the luma signal components. In the case of a 4:2:2 color format, the width of the CB/TB chrominance components may be set equal to half the width of the CB/TB chrominance components, and the height of the CB/TB chrominance components may be set to be equal to the height of the CB/TB luminance components. In the case of a 4:2:0 color format, the width of the CB/TB chrominance components may be set equal to half the width of the CB/TB chrominance components, and the height of the CB/TB chrominance components may be set to be equal to half the height of the CB/TB luminance components.

[135] In the embodiment, when the CTU size is 128 based on the unit of luminance samples, the CU size may have a size from 128x128 to 4x4, which is the same size as the CTU. In one embodiment, in the case of a 4:2:0 color format (or chroma format), the CB size of the chrominance signals may be from 64x64 to 2x2.

[136] Meanwhile, in an embodiment, the CU size and the TU size may be identical. Alternatively, a plurality of TUs may be provided in the CU area. The TU size generally represents the size of the transform unit (TB) of component (sampled) luminance signals.

[137] The TU size may be derived based on the largest valid TB size maxTbSize, which is a predetermined value. For example, when the CU size exceeds maxTbSize, a plurality of TUs (TB) having maxTbSize may be retrieved from the CU, and conversion/reconversion may be performed in TU units (TB). For example, the largest allowable TB size for luma signals may be 64×64, and the largest allowable TB size for chrominance signals may be 32×32. If the width or height of a CB segmented according to the tree structure is greater than the largest width or height of the transform, the CB may be automatically (or implicitly) segmented until the TB size limit in the horizontal and vertical directions is satisfied.

[138] In addition, for example, when intra prediction is applied, the intra prediction mode/type may be retrieved in CU (or CB) units, and the procedure for retrieving neighboring reference samples and generating prediction samples can be performed in TU (or TB) units. In this case, one or a plurality of TUs (or TBs) may be provided in one CU (or CB) area, and, in this case, the plurality of TUs or TBs may share the same intra prediction mode/type.

[139] Meanwhile, for a quadtree-based encoding scheme with a nested multi-type tree, the following parameters may be signaled as SPS syntax elements from the encoding equipment to the decoding equipment. For example, at least one of CTU-size, which is a parameter representing the size of the quadtree root nodes, MinQTSize, which is a parameter representing the minimum allowed size of the quadtree leaf nodes, MaxBtSize, which is a parameter representing the maximum the allowed size of the root nodes of a binary tree, MaxTtSize, which is a parameter representing the maximum allowed size of the root nodes of a ternary tree, MaxMttDepth, which is a parameter representing the maximum allowed depth of a multi-tree based partition hierarchy from a quadtree leaf node, MinBtSize, which is a parameter representing the minimum allowed size of binary tree leaf nodes, or MinTtSize, which is a parameter representing the minimum allowed size of ternary tree leaf nodes, is signaled.

[140] As an embodiment of using a 4:2:0 chrominance signal format, the CTU size may be set to 128x128 luma blocks and two 64x64 chroma blocks corresponding to luma blocks. In this case, MinOTSize can be set to 16x16, MaxBtSize can be set to 128x128, MaxTtSzie can be set to 64x64, MinBtSize and MinTtSize can be set to 4x4, and MaxMttDepth can be set to 4. Quadtree Segmentation can be applied to a CTU to form quadtree leaf nodes. A quadtree leaf node may be called a "QT leaf node". Quadtree leaf nodes can range in size from 16x16 (for example, MinOTSize) to 128x128 (for example, CTU-size). If the QT leaf node is 128x128, it may not be further segmented into a binary tree/ternary tree. This is due to the fact that in this case, even with segmentation, it exceeds MaxBtsize and MaxTtszie (for example, 64x64). In other cases, QT leaf nodes may further be segmented into a multi-type tree. Therefore, a QT leaf node is the root node for a multi-type tree, and a QT leaf node can have a value of 0 for the multi-type tree depth (mttDepth). If the depth of the multi-type tree reaches MaxMttdepth (for example, 4), additional segmentation may no longer be considered. If the node width of a multi-type tree is MinBtSize and less than or equal to 2xMinTtSize, then additional horizontal segmentation may not be considered. If the node height of a multi-type tree is MinBtSize and less than or equal to 2xMinTtSize, additional vertical segmentation may not be considered. When segmentation is not considered, the encoding equipment may omit the signaling of segmentation information. In this case, the decoding equipment can extract segmentation information with a predetermined value.

[141] Meanwhile, one CTU may include a luminance signal sample encoding unit (hereinafter referred to as a "luminance signal unit") and two chrominance signal sample encoding units corresponding thereto (hereinafter referred to as "chrominance signal units"). The above-described coding tree-based scheme can be applied equally or separately to the luma signal block and the chrominance signal block of the current CU. In particular, luma and chroma blocks in the same CTU may be segmented into an identical block tree structure, in which case, the tree structure is represented as SINGLE_TREE. Alternatively, blocks of luma and chrominance signals in a single CTU may be segmented into separate block tree structures, in which case, the tree structure may be represented as DUAL_TREE. Thus, when a CTU is segmented into dual trees, a block tree structure for a luma block and a block tree for a chrominance block may be separately present. In this case, the block tree structure for the luminance signal block may be called "DUAL_TREE_LUMA", and the block tree structure for the chrominance signal component may be called "DUAL_TREE_CHROMA". For groups of P- and B-slices/tiles, luma and chrominance blocks in the same CTU may be limited to having identical encoding tree structure. However, for groups of I-slices/tiles, luma and chroma blocks may have a separate block tree structure relative to each other. If a separate block tree structure is used, the luma CTB may be segmented into CUs based on a particular coding tree structure, and the chroma CTB may be segmented into chrominance CUs based on a different coding tree structure. Thus, this means that a CU in an I-slice/tile group to which a separate block tree structure is applied may include a luma component encoding unit or two chrominance component encoding units, and CUs of a P- or B- group. slices/tiles may include blocks of three color components (a luma component and two chrominance components).

[142] Although a structure in the form of a quadtree-based coding tree with a nested multi-type tree is described, the structure in which the CU is segmented is not limited to this. For example, a BT structure and a TT structure may be interpreted as a concept included in a multi-partitioning tree (MPT) structure, and a CU may be interpreted as segmentable through a QT structure and an MPT structure. In an example in which the CU is segmented across a QT structure and an MPT structure, a syntax element (for example, MPT_split_type) including information regarding how many blocks the leaf node of the QT structure is segmented into, and a syntax element (for example, MPT_split_mode) , including information regarding in which of the vertical and horizontal directions the leaf node of the QT structure is segmented, may be signaled to determine the segmentation structure.

[143] In another example, the CU may be segmented in a manner different from the QT structure, BT structure, or TT structure. Thus, in contrast to a smaller CU being segmented 1/4 of a larger depth CU according to the QT structure, a shallower CU being segmented 1/2 of a larger depth CU according to the BT structure, or a shallower CU being segmented by 1 /4 or 1/2 of a deeper CU according to the TT structure, a shallower CU can be segmented to 1/5, 1/3, 3/8, 3/5, 2/3 or 5/8 of a deeper CU in some cases, and the CU segmentation method is not limited to this.

[144] When a portion of a tree node block exceeds the lower frame boundary and/or the right frame boundary for a frame, the corresponding tree node block may be constrained such that the samples in all coded CUs are located at the frame boundaries. In this case, for example, the following partitioning rules may apply.

[145] Partitioning Rule 1: As a case in which a portion of a tree node block exceeds both the bottom frame boundary and the right frame boundary, when the tree node block is a QT node having a size greater than the minimum QT size, the node block The tree can be split in QT split mode, and when a tree node block is equal to or less than the minimum QT size, or is not a QT node, the tree node block is split in horizontal binary split mode (SPLIT_BT_HOR mode).

[146] Splitting Rule 2: As a case in which splitting rule 1 is not satisfied and a portion of the tree node block exceeds the lower frame boundary, the tree node block is split in QT splitting mode when the tree node block is a QT node having a size greater than the minimum QT size and the maximum BT size, and the tree node block is split in a horizontal binary split mode when the tree node block is a BTT node having a size equal to or less than the minimum QT size.

[147] Splitting rule 3: As a case in which splitting rule 1 and splitting rule 2 are not satisfied and a portion of the tree node block exceeds the right frame boundary, the tree node block is split in QT splitting mode when the tree node block is a QT -a node having a size greater than the minimum QT size and maximum BT size, and the tree node block is split in QT split mode or in horizontal binary mode when the tree node block has a size greater than the minimum QT size and equal to or less maximum BT size. Alternatively, when the tree node block is a BTT node or has a size equal to or less than the minimum QT size, the tree node block is split in horizontal binary mode.

[148] As described above, a multi-type tree quadtree coding block structure can provide a very flexible block segmentation structure. Due to the segmentation types supported in a multi-type tree, different segmentation patterns can potentially result in an identical encoding block structure in some cases. In the encoding equipment and decoding equipment, by limiting the occurrence of such redundant segmentation patterns, the data amount of segmentation information can be reduced.

[149] For example, FIG. 9 shows the redundant partitioning patterns that can occur in binary tree partitioning and ternary tree partitioning. As shown in FIG. 9, the continuous binary partition 910 and 920 for one direction of the two-stage layers has a coding block structure identical to the coding block structure for the binary partition for the center segment after the ternary partition. In this case, binary tree splitting for the central ternary tree splitting units 930 and 940 may be prohibited. this prohibition is applicable to all frame CUs. When such a particular split is prohibited, the signaling of the corresponding syntax elements may be modified to reflect this prohibited case, thereby reducing the number of bits signaled for the split. For example, as shown in the example shown in FIG. 9, when binary splitting for a central CU is disabled, a syntax element mtt_split_cu_binary_flag indicating whether the split is a binary split or a ternary split is not signaled, and its value may be extracted as 0 by the decoding equipment.

[150] Virtual Pipeline Data Unit

[151] Virtual Pipeline Data Units (VPDUs) may be specified for pipelining within a frame. VPDUs may be specified as non-overlapping units in the same frame. In decoding hardware, successive VPDUs can be processed simultaneously through multiple pipeline stages. In most pipeline stages, the VPDU size can be approximately proportional to the buffer size. Accordingly, keeping the VPDU size small is important when considering buffer size from a hardware perspective. In most types of decoding equipment, the VPDU size can be set to the maximum transform block (TB) size. For example, the VPDU size may be 64×64 (64×64 luminance samples). In addition, the VPDU size may change (increase or decrease) taking into account the above-described ternary tree (TT) and/or binary tree (BT) partitioning.

[152] Meanwhile, in order to keep the VPDU size equal to 64×64, at least one of the following restrictions may be applied.

[153] Constraint 1: Ternary tree splitting is not allowed for a CU having at least one of width or height 128.

[154] Limitation 2: Horizontal binary tree splitting for a CU having a width of 128 and a height of 64 or less (ie, a 128xN CU with N≤64) is not allowed.

[155] Limitation 3: Vertical tree partitioning for a CU having a width of 64 or less or a height of 128 (ie, an Nx128 CU with N≤64) is not allowed.

[156] Examples of CU partitioning now allowed under the above restrictions are shown in FIG. 10. In FIG. 10, the bold solid lines indicate block partitioning, and the remaining solid lines indicate CUs.

[157] Referring to FIG. 10, according to constraint 1, vertical ternary tree partitioning is not allowed for CU 1010 128×128. In addition, according to constraint 1, horizontal ternary tree partitioning is not allowed for CU 1020 128x128. In addition, according to constraint 3, vertical binary tree partitioning is not allowed for the CU 1030 64x128. In addition, according to constraint 2, horizontal binary tree partitioning is not allowed for the CU 1040 128x64. In addition, according to constraint 1, vertical ternary tree partitioning is not allowed for the CU 1050 64x128. In addition, according to constraint 1, horizontal ternary tree partitioning is not allowed for CU 1060 128x64. In addition, according to constraint 1, horizontal ternary partitioning is not permitted for the CU 1070 64x128. In addition, according to constraint 1, vertical ternary partitioning is not allowed for the CU 1080 128x64.

[158] Meanwhile, in the dual tree in the inner frame, different segmentation structures may be applied to the luma coding tree and the chrominance coding tree. In a dual tree, a larger encoding pipeline can be introduced and, in a chroma encoding tree, a chroma block having a small size, for example, 2x2, 4x2 and 2x4, can be resolved according to the QTBT value range MinQTSizeC, MinBtSizeY and MinTTSizeY. However, this can make it difficult to design practical decoding equipment. In addition, multiplication operation is required in Cross Component Linear Model (CCLM) mode, planar mode, corner mode, etc. To solve the above problems, in a dual tree, a chrominance signal block having a small size, for example, 2x2, 4x2 and 2x4, can be limited through segmentation constraints.

[159] General introduction to quantization/dequantization

[160] Quantization/dequantization according to the present disclosure is described later in this document.

[161] As described above, the encoding equipment quantization unit can extract the quantized transform coefficients by applying quantization to the transform coefficients, and the encoding equipment dequantization unit or the decoding equipment dequantization unit can extract the transform coefficients by applying dequantization to the quantized transform coefficients.

[162] In general, when encoding video/images, the quantization rate may be changed, and the compression ratio may be adjusted using the changed quantization rate. From an implementation point of view, the quantization parameter (QP) can be used instead of directly using the complexity-aware quantization rate. For example, a quantization parameter of an integer value from 0 to 63 may be used, and the value of each quantization parameter may correspond to the actual quantization rate. The quantization parameter QPY for the luminance signal component (luminance signal sample) may be set to a value different from the value of the quantization parameter QPC for the chrominance signal component (chrominance signal sample).

[163] In the quantization process, the transform coefficient C may be received as input and divided by the quantization rate Qstep, thereby extracting the quantized transform coefficient C'. In this case, in consideration of the computational complexity, the quantization rate is multiplied by the scale to form an integer operation, and the shift operation can be performed by a value corresponding to the scale value. Based on the product of the quantization rate and the scale value, the quantization scale can be extracted. Thus, the quantization scale can be extracted according to the QP. By applying the quantization scale to the transform coefficient C, the quantized transform coefficient C' can be extracted based on it.

[164] The dequantization process is the inverse process of the quantization process, and the quantized transform coefficient C' can be multiplied by the quantization rate Qstep, thereby extracting a reconstructed transform coefficient C''. In this case, the level scale can be extracted according to the quantization parameter, and the level scale can be applied to the quantized transform coefficient C', thereby extracting the reconstructed transform coefficient C''. The reconstructed transform coefficient C'' may differ slightly from the original transform coefficient C due to losses in the conversion and/or quantization process. Accordingly, even encoding equipment can perform dequantization in the same manner as decoding equipment.

[165] Meanwhile, an adaptive frequency quantization technology with weighting for adjusting the quantization intensity according to frequency can be used. Weighted adaptive frequency quantization technology is a method of applying quantization intensity differently according to frequency. In adaptive frequency quantization with weighting, the quantization intensity can be applied differently according to frequency using a predefined quantization scaling matrix. Thus, the above-described quantization/dequantization process can be further performed based on the quantization scaling matrix. For example, a different quantization scaling matrix may be used according to the size of the current block and/or whether the prediction mode applied to the current block to generate the residual signal of the current block is inter-prediction or intra-prediction. The quantization scaling matrix may also be referred to as the "quantization matrix" or "scaling matrix". The quantization scaling matrix can be predefined. In addition, the frequency quantization scale information for the quantization scaling matrix for frequency adaptive scaling may be constructed/encoded by the encoding equipment and signaled to the decoding equipment. The frequency quantization scale information may be referred to as “quantization scaling information.” The frequency quantization scale information may include scaling list data scaling_list_data. Based on the scaling list data, a (modified) quantization scaling matrix can be extracted. In addition, the frequency quantization scale information may include presence flag information indicating whether or not scale list data is present. Alternatively, when zoom list data is signaled at the upper layer (e.g., SPS), information indicating whether or not the zoom list data at the lower layer (e.g., PPS or tile group header, etc.) may be further included. .

[166] General presentation of mutual forecasting

[167] This document further describes mutual prediction according to the present disclosure.

[168] The image encoding equipment/image decoding equipment prediction module according to the present disclosure can perform inter-prediction in units of blocks to extract a prediction sample. The inter-prediction may represent a prediction extracted in a manner that depends on data elements (eg, sample values, motion information, etc.) of frame(s) other than the current frame. When inter-prediction is applied to the current block, a predicted block (prediction block or prediction sample array) for the current block can be retrieved based on the reference block (reference sample array) indicated by the motion vector for the reference frame indicated by the reference frame index. In this case, in order to reduce the amount of motion information transmitted in the inter-prediction mode, the motion information of the current block may be predicted in units of blocks, sub-blocks or samples based on the correlation of the motion information between a neighboring block and the current block. The motion information may include a motion vector and a reference frame index. The motion information may further include inter-prediction type information (L0 prediction, L1 prediction, bi-prediction, etc.). In the case of inter-prediction, the neighbor block may include a spatial neighbor block present in the current frame and a temporal neighbor block present in the reference frame. The reference frame including the reference block and the reference frame including the temporary adjacent block may be identical or different. A temporary neighbor block may be referred to as a "co-located reference block", "col-located CU (colCU)" or "colBlock", and a reference frame including a temporary neighboring block may be referred to as a "col-located frame (colPic)" or "colPicture". . For example, a list of candidate motion information may be constructed based on neighboring blocks relative to the current block, and flag or index information indicating which candidate is selected (used) may be signaled so as to retrieve the motion vector of the current block and/or or reference frame index.

[169] Inter-prediction can be performed based on different prediction modes. For example, in the case of the skip mode and the merge mode, the motion information of the current block may be equal to the motion information of the selected adjacent block. In the case of the skip mode, the residual signal may not be transmitted, unlike the combine mode. In the case of the motion information prediction (MVP) mode, the motion vector of the selected neighboring block can be used as a motion vector predictor, and the motion vector difference can be signaled. In this case, the motion vector of the current block can be extracted using the sum of the motion vector predictor and the motion vector difference. In the present disclosure, the MVP mode may have a meaning identical to that of Advanced Motion Vector Prediction (AMVP).

[170] The motion information may include L0 motion information and/or L1 motion information according to a type of inter-prediction (L0 prediction, L1 prediction, bi-prediction, etc.). The motion vector in the L0 direction may be referred to as the "L0 motion vector" or "MVL0", and the motion vector in the L1 direction may be referred to as the "L1 motion vector" or "MVL1". Prediction based on L0 motion vector may be referred to as “L0 prediction,” prediction based on L1 motion vector may be referred to as “L1 prediction,” and prediction based on both L0 motion vector and L1 motion vector may be referred to as “biprediction.” ". Here, the L0 motion vector may indicate a motion vector associated with a reference frame list (L0) L0, and the L1 motion vector may indicate a motion vector associated with a reference frame list (L1) L1. The reference frame list L0 may include frames before the current frame in output order as reference frames, and the reference frame list L1 may include frames after the current frame in output order. Previous frames may be referred to as "forward (reference) frames" and subsequent frames may be referred to as "reverse (reference) frames". The reference frame list L0 may further include frames after the current frame in the order of output as reference frames. In this case, in the reference frame list L0, previous frames may be indexed first, and subsequent frames may then be indexed. The reference frame list L1 may further include frames before the current frame in the order of output as reference frames. In this case, in the reference frame list L1, subsequent frames may be indexed first, and previous frames may then be indexed. Here, the order of output may correspond to the order of numbers in the sequence of frames (POC).

[171] FIG. 11 is a flowchart illustrating a video/image encoding method based on inter-prediction.

[172] FIG. 12 is a view illustrating the configuration of the inter-prediction module 180 according to the present disclosure.

[173] The encoding method of FIG. 11 may be implemented by the image encoding equipment of FIG. 2. Specifically, step S1110 may be performed by the inter-prediction unit 180, and step S1120 may be performed by the residual processor. Specifically, step S1120 may be performed by the subtractor 115. Step S1130 may be performed by the entropy encoder 190. The prediction information of step S1130 may be extracted by the inter-prediction unit 180, and the residual information of step S1130 may be extracted by the residual processor. Residual information is information regarding the residual samples. The residual information may include information regarding quantized transform coefficients for the residual samples. As described above, the residual samples can be extracted as transform coefficients through the image encoding equipment transformer 120, and the transform coefficients can be extracted as quantized transform coefficients through the quantizer 130. Information regarding the quantized transform coefficients can be encoded by the entropy encoder 190 through a residual encoding procedure.

[174] The image encoding equipment may perform inter-prediction for the current block (S1110). The image encoding equipment can extract the inter-prediction mode and motion information of the current block and generate predictive samples of the current block. Here, the procedures for determining the mutual prediction mode, extracting motion information, and generating prediction samples may be performed simultaneously, or any of them may be performed before the other procedures. For example, as shown in FIG. 12, the inter-prediction unit 180 of the image encoding equipment 100 may include a prediction mode determining unit 181, a motion information extracting unit 182, and a prediction sample extracting unit 183. The prediction mode determining unit 181 may determine the prediction mode of the current block, the motion information extracting unit 182 may extract motion information of the current block, and the prediction sample extracting unit 183 may extract prediction samples of the current block. For example, the image encoding equipment inter-prediction unit 180 can search for a block similar to the current block in a predetermined area (search area) of reference frames through motion estimation, and extract a reference block whose difference with respect to the current block is equal to or less than a predetermined criterion or minimum. Based on this, a reference frame index indicating the reference frame in which the reference block is located can be retrieved, and a motion vector can be retrieved based on the position difference between the reference block and the current block. The image encoding equipment may determine the mode applied to the current block from various prediction modes. The image encoding equipment can compare the distortion cost functions as a function of the bit rate (RD) for different prediction modes and determine the optimal prediction mode of the current block. However, the method for determining the prediction mode of the current block by the image encoding equipment is not limited to the above example, and various methods can be used.

[175] For example, when a skip mode or a merge mode is applied to a current block, the image encoding equipment may extract merge candidates from neighboring blocks relative to the current block and construct a list of merge candidates using the extracted merge candidates. In addition, the image encoding equipment can extract a reference block whose difference with respect to the current block is equal to or less than a predetermined criterion or minimum from the reference blocks indicated by the combine candidates included in the list of combine candidates. In this case, a combine candidate associated with the extracted reference block can be selected, and combine index information indicating the selected merge candidate can be generated and signaled to the image decoding equipment. The motion information of the current block may be extracted using the motion information of the selected combining candidate.

[176] As another example, when the MVP mode is applied to the current block, the image encoding equipment may extract motion vector predictor (MVP) candidates from neighboring blocks relative to the current block and construct a list of MVP candidates using the extracted MVP candidates . In addition, the image encoding equipment may use a motion vector of an MVP candidate selected from among the MVP candidates included in the MVP candidate list as the MVP of the current block. In this case, for example, the motion vector indicating the reference block extracted by the above-described motion estimation can be used as the motion vector of the current block, and a possible MVP variant with a motion vector having the smallest difference with respect to the motion vector of the current block among the possible MVP variants , may represent a selected candidate MVP. A motion vector difference (MVD), which is a difference obtained by subtracting the MVP from the motion vector of the current block, can be extracted. In this case, index information indicating the selected MVP candidate and information regarding the MVD may be signaled to the image decoding equipment. In addition, when the MVP mode is applied, the reference frame index value can be constructed as reference frame index information and separately signaled to the image decoding equipment.

[177] The image encoding equipment may extract residual samples based on the predictive samples (S1120). The image encoding hardware can extract residual samples through a comparison between the current block's original samples and the predicted samples. For example, the residual sample may be extracted by subtracting the corresponding predictive sample from the original sample.

[178] The image encoding equipment can encode image information including prediction information and residual information (S1130). The image encoding equipment 100 may output encoded image information in the form of a bit stream. The prediction information may include prediction mode information (eg, a skip flag, a merge flag, or a mode index, etc.) and motion information as information associated with the prediction procedure. From the prediction mode information, the skip flag indicates whether or not the skip mode is applied to the current block, and the merge flag indicates whether or not the merge mode is applied to the current block. Alternatively, the prediction mode information may indicate one of a plurality of prediction modes, eg, a mode index. When the skip flag and the merge flag are 0, it can be determined that the MVP mode is applied to the current block. The information regarding the motion information may include candidate selection information (eg, a pooling index, an MVP flag, or an MVP index), which is information for extracting a motion vector. From the candidate selection information, the combining index may be signaled when a combining mode is applied to the current block, and may be information for selecting one of the combining candidates included in the combining candidate list. Of the candidate selection information, an MVP flag or an MVP index may be signaled when the MVP mode is applied to the current block, and may be information for selecting one of the candidate MVP candidates in the candidate MVP candidate list. In addition, information regarding the motion information may include information regarding the above-described MVD and/or reference frame index information. In addition, information regarding the motion information may include information indicating whether L0 prediction, L1 prediction, or bi-prediction should be applied. Residual information is information regarding the residual samples. The residual information may include information regarding quantized transform coefficients for the residual samples.

[179] The output bitstream may be stored on a (digital) storage medium and transmitted to the image decoding equipment, or may be transmitted to the image decoding equipment via a network.

[180] As described above, the image encoding equipment can generate a reconstructed frame (a frame including reconstructed samples and a reconstructed block) based on the reference samples and residual samples. This serves to extract, by the image encoding equipment, a prediction result identical to the prediction performed by the image decoding equipment, thereby improving encoding efficiency. Accordingly, the image encoding equipment may store the reconstructed frame (or the reconstructed samples and the reconstructed block) in a storage device and use it as a reference frame for inter-prediction. As described above, an in-loop filtering procedure may further be applied to the reconstructed frame.

[181] FIG. 13 is a flowchart illustrating a video/image decoding method based on inter-prediction.

[182] FIG. 14 is a view illustrating the configuration of the inter-prediction module 260 according to the present disclosure.

[183] The image decoding equipment may perform an operation corresponding to the operation performed by the image encoding equipment. The image decoding equipment may perform prediction for the current block based on the received prediction information and extract prediction samples.

[184] The decoding method of FIG. 13 may be implemented by the image decoding equipment of FIG. 3. Steps S1310 to S1330 may be performed by the prediction module and prediction information of step S1310, and the residual information of step S1340 may be obtained from the bitstream by the entropy decoder 210. The residual processor of the image decoding equipment may extract residual samples for the current block based on the residual information (S1340 ). In particular, the residual processor dequantizer 220 may perform dequantization based on the dequantized transform coefficients extracted based on the residual information to extract transform coefficients, and the residual processor inverter 230 may perform inverse transform on the transform coefficients to extract residual samples for the current block. Step S1350 may be performed by the adder 235 or the recovery module.

[185] Specifically, the image decoding equipment may determine a prediction mode of the current block based on the received prediction information (S1310). The image decoding equipment can determine which inter-prediction mode is applied to the current block based on the prediction mode information in the prediction information.

[186] For example, it may be determined whether or not skip mode is applied to the current block based on the skip flag. In addition, it can be determined whether the merge mode or MVP mode is applied to the current block based on the merge flag. Alternatively, one of the various possible inter-prediction mode options may be selected based on the mode index. Options for inter-prediction modes may include a skip mode, a merge mode, and/or an MVP mode, or may include various inter-prediction modes, which are described below.

[187] The image decoding equipment may extract motion information of the current block based on the determined inter-prediction mode (S1320). For example, when a skip mode or a combine mode is applied to the current block, the image decoding equipment may construct a list of combine candidates, which is described below, and select one of the combine candidates included in the list of combine candidates. The selection may be made based on the candidate selection information (merging index) described above. The motion information of the current block may be extracted using the motion information of the selected combining candidate. For example, the motion information of the selected combining candidate may be used as the motion information of the current block.

[188] As another example, when the MVP mode is applied to the current block, the picture decoding equipment may construct a list of candidate MVPs and use a motion vector of a candidate MVP selected from among candidate MVPs included in the list of candidate MVPs. options as the MVP of the current block. The selection may be made based on the candidate selection information described above (MVP flag or MVP index). In this case, the MVD of the current block can be extracted based on information regarding the MVD, and the motion vector of the current block can be extracted based on the MVP and MVD of the current block. In addition, the reference frame index of the current block may be retrieved based on the reference frame index information. The frame indicated by the reference frame index in the reference frame list of the current block may be retrieved as a reference frame referred to for inter-prediction of the current block.

[189] The image decoding equipment can generate predictive samples of the current block based on motion information of the current block (S1330). In this case, the reference frame can be retrieved based on the reference frame index of the current block, and the prediction samples of the current block can be retrieved using the reference block samples indicated by the motion vector of the current block for the reference frame. In some cases, the prediction sample filtering procedure may additionally be performed on all or some of the prediction samples of the current block.

[190] For example, as shown in FIG. 14, the image decoding equipment inter-prediction unit 260 may include a prediction mode determining unit 261, a motion information extracting unit 262, and a prediction sample extracting unit 263. In the image decoding equipment inter-prediction unit 260, the prediction mode determining unit 261 can determine the prediction mode of the current block based on the received prediction mode information, the motion information extracting unit 262 can extract motion information (motion vector and/or reference frame index, etc. ) of the current block based on the received motion information, and the prediction sample extracting unit 263 can extract the prediction samples of the current block.

[191] The image decoding equipment may generate residual samples of the current block based on the received residual information (S1340). The image decoding equipment can generate reconstructed samples of the current block based on the prediction samples and residual samples, and generate a reconstructed frame based on it (S1350). After this, the in-loop filtering procedure can be applied to the reconstructed frame as described above.

[192] As described above, the inter-prediction procedure may include a step of determining the inter-prediction mode, a step of extracting motion information according to the determined prediction mode, and a step of performing prediction (generating prediction samples) based on the extracted motion information. The inter-prediction procedure may be performed by the image encoding equipment and the image decoding equipment as described above.

[193] Understanding Intra Block Copy (IBC) Forecasting

[194] This document further describes IBC prediction according to the present disclosure.

[195] IBC prediction may be performed by an image encoding/decoding equipment prediction module. IBC forecasting may simply be called "IBC". IBC can be used for content/moving image coding, such as Screen Content Coding (SCC). IBC prediction may essentially be performed within the current frame, but may be performed similarly to inter-prediction in that the reference block is retrieved within the current frame. Thus, the IBC may use at least one of the inter-prediction technologies described in the present disclosure. For example, the IBC may use at least one of the above-described methods for extracting motion information (motion vectors). At least one of the mutual forecasting technologies may be partially modified and used to accommodate IBC forecasting. The IBC may refer to the current frame and may therefore be called a "Current Frame Reference (CPR)".

[196] For IBC, image encoding equipment 100 may perform block matching (BM) and extract an optimal block vector (or motion vector) for the current block (eg, CU). The extracted block vector (or motion vector) may be signaled to the image decoding equipment via a bitstream using a method similar to signaling motion information (motion vector) in the above-described inter-prediction. The image decoding equipment can extract a reference block for a current block in a current frame through a signaled block vector (motion vector), and extract a prediction signal (predicted block or prediction samples) for the current block through it. Here, the block vector (or motion vector) may indicate an offset from the current block to a reference block located in the already reconstructed area in the current frame. Accordingly, the block vector (or motion vector) may be referred to as a "displacement vector". Later in this document, in IBC, the motion vector may correspond to a block vector or a displacement vector. In addition, in IBC, motion vector difference (MVD) can also be called "block vector difference (BVD)". The motion vector of the current block may include a motion vector for the luma signal component (luminance motion vector) or a motion vector for the chrominance signal component (chrominance motion vector). For example, the luminance motion vector for an IBC-coded CU may be an integer unit of samples (ie, integer precision). The motion vector of chrominance signals may be clipped in integer sample units. As described above, the IBC may use at least one of the inter-prediction technologies and, for example, when the IBC is used as AMVR, the 1-pel and 4-pel motion vector precisions can be switched.

[197] In IBC, a reference block is retrieved from an already reconstructed area in the current frame. In this case, in order to reduce the storage consumption and the complexity of the image decoding equipment, it is possible to refer only to a predetermined area from the already reconstructed areas in the current frame. The predefined zone may include the current CTU in which the current block is included. By limiting the restored referenceable zone to a predefined zone, the IBC mode can be implemented in hardware using local on-chip storage.

[198] Image encoding equipment for performing IBC can search in a predetermined area to determine a reference block with the least RD cost and extract a motion vector (block vector) based on the positions of the reference block and the current block.

[199] Whether or not IBC should be applied to the current block may be signaled as IBC performance information at the CU level. Information regarding the signaling method (IBC MVP mode or IBC skip/merge mode) of the motion vector of the current block may be signaled. The IBC performance information can be used to determine the prediction behavior of the current block. Accordingly, IBC performance information may be included in information regarding the prediction mode of the current block.

[200] In the case of IBC-skip/merge mode, a combine candidate index may be signaled to indicate a block vector that should be used to predict the current luma block from block vectors included in the list of combine candidates. In this case, the list of possible combinations may include IBC-encoded neighboring blocks. The list of join options may be configured to include spatial join options and not include temporal join options. In addition, the list of fusion candidates may further include history-based motion vector predictor (HMVP) candidates and/or pairwise candidates.

[201] In the case of the IBC MVP mode, the difference value of block vectors can be encoded using a method identical to that for the difference value of motion vectors of the above-described mutual mode. The block vector prediction method may construct and use a list of candidate MVPs, including two candidate candidates, as predictors, similar to the MVP mode for the reciprocal mode. One of the two possibilities may be retrieved from a left adjacent block, and the other candidate may be retrieved from an upper adjacent block. In this case, only when the left or top neighbor block is IBC-encoded, candidates can be retrieved from the corresponding neighbor block. If the left or top neighbor block is not available, for example not IBC encoded, the default block vector may be included in the list of possible MVP candidates as a predictor. In addition, information (eg, a flag) indicating one of the two block vector predictors is signaled and used as candidate selection information similar to the MVP mode for the mutual mode. The list of candidate MVPs may include a candidate HMVP and/or a null motion vector as a default block vector.

[202] An HMVP candidate may be referred to as a “history-based MVP candidate,” and an MVP candidate used before encoding/decoding the current block, a concatenation candidate, or a block vector candidate may be stored in the HMVP list as candidates. HMVP options. Thereafter, when the list of possible merge options of the current block or the list of possible MVP options does not include the maximum number of possible options, the options stored in the HMVP list can be added to the list of possible merge options or the list of possible MVP options of the current block in as possible HMVP options.

[203] A pairwise candidate may mean a candidate extracted by selecting two candidates according to a predetermined order from among the candidates already included in the list of candidate options for combining the current block, and averaging the selected two candidates.

[204] Embodiment

[205] Exemplary embodiments of the present disclosure are described in detail below with reference to the accompanying drawings.

[206] During the quantization/dequantization process for the current block, a quantization matrix may be constructed. The image encoding/decoding equipment may quantize/dequantize the transform coefficients of the current block using a quantization matrix. The quantization matrix may be called a "scaling list". In addition, one or more quantization matrix coefficients included in the quantization matrix may be referred to as “scaling list data.”

[207] In an example, the quantization matrix may be identical in size to the current block. For example, when the size of the current block is 4x4, the size of the quantization matrix for the current block may also be 4x4. The size of the quantization matrix may be specified using a predefined size identifier (eg, sizeId). Fig. 15 is a view illustrating an example of sizeId for each size of the quantization matrix.

[208] Referring to FIG. 15, the sizeId value for a 1×1 quantization matrix may be 0, and the sizeId value for a 2×2 quantization matrix may be 1. In addition, the sizeId value for a 4×4 quantization matrix may be 2, and the sizeId value for a quantization matrix 8x8 quantization matrix can be 3. In addition, the sizeId value for a 16x16 quantization matrix can be 4, and the sizeId value for a 32x32 quantization matrix can be 5. In addition, the sizeId value for a 64x64 quantization matrix may be equal to 6. In an example, the size of the quantization matrix may change (increase or decrease) during the encoding process.

[209] In an example, the quantization matrix may be constructed differently according to the size (eg, sizeId) of the quantization matrix, the prediction mode (eg, intra-prediction mode, inter-prediction mode, etc.) of the current block, and the color component (eg, Y , Cb, Cr). Fig. 16 is a view illustrating an example of a quantization matrix for a current block designed based on the example of FIG. 15.

[210] Referring to FIG. 16, the image encoding equipment can construct the first to sixth quantization matrices matrixId=0 to matrixId=5 having different sizes sizeId based on the prediction mode CuPredMode of the current block and the color component cIdx.

[211] In particular, for a luminance signal component (cIdx=0) (eg, Y) in the current block encoded using the intra prediction mode, a first quantization matrix (matrixId=0) may be constructed. In this case, the size of the first quantization matrix may be equal to or greater than 2×2 and equal to or less than 64×64 (ie, 2≤sizeId≤6). In addition, for the first chrominance signal component (cIdx=1) (eg, Cb) in the current block encoded using the intra prediction mode, a second quantization matrix (matrixId=1) may be constructed. In this case, the size of the second quantization matrix may be equal to or greater than 1×1 and equal to or less than 64×64 (ie, 1≤sizeId≤6). In addition, for a second chrominance signal component (cIdx=2) (eg, Cr) in the current block encoded using the intra prediction mode, a third quantization matrix (matrixId=2) may be constructed. In this case, the size of the third quantization matrix is equal to or greater than 1×1 and equal to or less than 64×64 (ie, 1≤sizeId≤6). In addition, for the luminance signal component (cIdx=0) in the current block encoded using the inter-prediction mode or the inter-block copy (IBC) mode, a fourth quantization matrix (matrixId=3) may be constructed. In this case, the size of the fourth quantization matrix may be equal to or greater than 2×2 and equal to or less than 64×64 (ie, 2≤sizeId≤6). In addition, for the first chrominance signal component (cIdx=1) in the current block encoded using the inter-prediction mode or the IBC mode, a fifth quantization matrix (matrixId=4) may be constructed. In this case, the size of the fifth quantization matrix may be equal to or greater than 1×1 and equal to or less than 64×64 (ie, 1≤sizeId≤6). In addition, for the second chrominance signal component (cIdx=2) in the current block encoded using the inter-prediction mode or the IBC mode, a sixth quantization matrix (matrixId=5) may be constructed. In this case, the size of the fifth quantization matrix may be equal to or greater than 1×1 and equal to or less than 64×64 (ie, 1≤sizeId≤6).

[212] In the examples of FIGS. 15 and 16, the quantization matrix for the current block may be indicated by a size identifier (eg, sizeId) and a quantization matrix identifier (eg, matrixId).

[213] Meanwhile, the image encoding equipment can encode the quantization matrix for the current block and signal it to the image decoding equipment. For example, the image encoding equipment may encode a quantization matrix coefficient included in the quantization matrix, or encode an identifier of a quantization reference matrix corresponding to the quantization matrix, and signal it to the image decoding equipment. Hereinafter, this document describes in detail a method for encoding a quantization matrix.

[214] FIG. 17 is a flowchart illustrating a quantization matrix encoding method according to an embodiment of the present disclosure. The encoding method of FIG. 17 may be implemented by the image encoding equipment of FIG. 2. Specifically, steps S1710 to S1740 may be performed by the quantization unit 130 and/or the dequantization unit 140.

[215] Referring to FIG. 17, the image encoding equipment may encode quantization mode information of a method for constructing a quantization matrix for the current block (S1710).

[216] In an example, the quantization mode information may include first mode information indicating whether or not a quantization matrix is constructed based on a reference quantization matrix. The first mode information may be encoded using a predetermined flag. For example, first mode information may be encoded using scaling_list_pred_mode_flag. In this case, the first value (eg, 0) of scaling_list_pred_mode_flag may indicate that the quantization matrix for the current block is identical to the reference quantization matrix. Here, the quantization reference matrix may be specified using the quantization reference matrix identification information (eg, scaling_list_pred_matrix_id_delta). In contrast, a second value (eg, 1) of scaling_list_pred_mode_flag may indicate that the quantization matrix for the current block is not identical to the reference quantization matrix. When scaling_list_pred_mode_flag has a second value, the value of the quantization matrix for the current block may be explicitly signaled.

[217] In another example, the quantization mode information may include first mode information and second mode information.

[218] The first mode information may indicate that the quantization matrix is configured to be identical to the reference quantization matrix. The first mode information may be encoded using a predetermined first mode flag. For example, first mode information may be encoded using scaling_list_copy_mode_flag. In this case, when the first value (eg, 0) of the scaling_list_copy_mode_flag may indicate that the quantization matrix for the current block is identical to the reference quantization matrix. In contrast, a second value (eg, 1) of scaling_list_copy_mode_flag may indicate that the quantization matrix for the current block is not identical to the reference quantization matrix. When scaling_list_copy_mode_flag is not signaled, scaling_list_copy_mode_flag may be inferred to have the first value.

[219] The second mode information may indicate whether or not a quantization matrix is extracted from the reference quantization matrix. The second mode information may be encoded using a predetermined second mode flag only when the quantization matrix for the current block is not identical to the reference quantization matrix. For example, the second mode information may be encoded using scaling_list_pred_mode_flag only when the scaling_list_copy_mode_flag indicating the first mode information has a second value (eg, 1). In this case, the first value (eg, 0) of the scaling_list_pred_mode_flag may indicate that the quantization matrix for the current block is derived from the reference quantization matrix. In contrast, a second value (eg, 1) of scaling_list_pred_mode_flag may indicate that the quantization matrix for the current block is not derived from the reference quantization matrix. When scaling_list_pred_mode_flag has a second value, the value of the quantization matrix for the current block may be explicitly signaled.

[220] The image encoding equipment can determine whether or not a quantization matrix is constructed for the current block from the reference quantization matrix based on the quantization mode information encoded in step S1710 (S1720). For example, the image encoding equipment may determine whether or not a quantization matrix for the current block is constructed such that it is identical to the reference quantization matrix based on the first mode information. Alternatively, the image encoding equipment may determine whether or not the quantization matrix for the current block is derived from the reference quantization matrix based on the second mode information.

[221] When the quantization matrix for the current block is constructed from the reference quantization matrix (“Yes” in S1720), the image encoding equipment may encode identification information of the reference quantization matrix to indicate the reference quantization matrix (S1730). The identification information of the quantization reference matrix may be encoded using a predefined syntax element, for example, scaling_list_pred_matrix_id_delta. When scaling_list_pred_matrix_id_delta has the first value (eg 0), the quantization matrix for the current block can be retrieved from the predefined default matrix. All one or more quantization matrix coefficients included in the default matrix may have the same value. In the example, the values of the quantization matrix coefficients included in the default matrix could be 16. In contrast, when scaling_list_pred_matrix_id_delta has a value (e.g. 1, 2, 3, etc.) other than the first value, the quantization matrix for the current block can be retrieved from the reference quantization matrix specified based on scaling_list_pred_matrix_id_delta. For example, the quantization reference matrix may be specified based on scaling_list_pred_matrix_id_delta, as shown in Equation 1 below.

[222] equation 1

refMatrixId=matrixID-scaling_list_pred_matrix_id_delta[sizeId][matrixId] * (sizeId==6?3:1)

[223] In Equation 1, refMatrixId may denote a reference quantization matrix identifier, and matrixID may denote a quantization matrix identifier for the current block, as described above with reference to FIG. 16. In addition, sizeId may indicate the size of the quantization matrix for the current block, as shown above with reference to FIG. 15 and 16.

[224] Based on the refMatrixId obtained by Equation 1, the quantization ScalingList matrix for the current block can be retrieved as shown in Equation 2.

[225] equation 2

ScalingList [SizeId][matrixId][i]=ScalingList [SizeId][refMatrixId][i] with i=0...Min(63, (1<<(sizeId<<1))-1)

[226] In Equation 2, i denotes each element of the quantization matrix ScalingList for the current block, and i may have the smallest value of 63 and (1<<(sizeId<<1))-1 as the maximum value.

[227] When the quantization matrix for the current block is not constructed from the reference quantization matrix (“No” in S1720), the value of the quantization matrix for the current block may be encoded (S1740).

[228] The quantization matrix value for the current block may be encoded using predefined syntax elements. For example, the quantization matrix value for the current block may be encoded using scaling_list_dc_coef_minus8 indicating the scaling factor of the quantization matrix for the current block, and scaling_list_delta_coef indicating the difference between the (i-1)th quantization matrix coefficient and the i-th quantization matrix coefficient in the quantization matrix.

[229] In addition, the quantization matrix value for the current block may be encoded according to a predetermined scanning method. For example, one or more quantization matrix coefficients in the quantization matrix for the current block may be sequentially encoded according to a diagonal scan order.

[230] An example syntax for implementing the quantization matrix encoding method described above with reference to FIG. 17 is shown in FIG. 18.

[231] Referring to FIG. 18, based on FIG. 16, quantization matrices (eg, matrixId=0 - matrixId=5) having a size of 2x2 or more can be encoded using scaling_list_data syntax (1810). In addition, all quantization matrices except the quantization matrix (for example, sizeId=1 andand matrixId%3=0) having a size of 2x2 for the luminance signal component of the current block, or the quantization matrix (for example, sizeId=6 andand matrixId%3 !=0) having a size of 64x64 for the chroma component of the current block may be encoded with scaling_list_data (1820) syntax.

[232] As a result, a quantization matrix (eg, matrixId=1, 2, 4, or 5) having a size of 2x2 for the chrominance signal component (eg, matrixId%3!=0) of the current block can be encoded using scaling_list_data syntax . However, as described above, in a twin-tree structure, a 2x2 chroma block is prohibited through a segmentation constraint, the 2x2 quantization matrix encoding process may be optional. In addition, when a quantization matrix having a small size, such as 2×2, is encoded, the amount of overhead information transmitted may increase.

[233] To solve such a problem, the quantization matrix encoding method according to an embodiment of the present disclosure can only be performed with respect to a quantization matrix having a size greater than 2×2. That is, the process of encoding a quantization matrix having a sizeId value of 0 or 1 (ie, having a size of 2×2 or less) described above with reference to FIG. 15 and 16 may be skipped.

[234] FIG. 19 is a view illustrating an example of a quantization matrix for a current block according to an embodiment of the present disclosure.

[235] Referring to FIG. 19, the image encoding equipment can construct the first to sixth quantization matrices (matrixId=0 - matrixId=5) having different sizes sizeId based on the prediction mode CuPredMode of the current block and the color component cIdx.

[236] In particular, for a luminance signal component (cIdx=0) (eg, Y) in the current block encoded using the intra prediction mode CuPredMode=MODE_INTRA, a first quantization matrix (matrixId=0) may be constructed. In addition, for the first chrominance signal component (cIdx=1) (eg, Cb) in the current block encoded using the intra prediction mode, a second quantization matrix (matrixId=1) may be constructed. In addition, for a second chrominance signal component (cIdx=2) (eg, Cr) in the current block encoded using the intra prediction mode, a third quantization matrix (matrixId=2) may be constructed. In addition, for the luminance signal component (cIdx=0) in the current block encoded using the inter-prediction mode or the inter-block copy (IBC) mode (CuPredMode=MODE_INTER or MODE_IBC), a fourth quantization matrix (matrixId=3) may be constructed. In addition, for the first chroma block (cIdx=1) in the current block encoded using the inter-prediction mode or the IBC mode, a fifth quantization matrix (matrixId=4) may be constructed. In addition, for the second chrominance signal component (cIdx=2) in the current block encoded using the inter-prediction mode or the IBC mode, a sixth quantization matrix (matrixId=5) may be constructed.

[237] The size of each of the first to sixth quantization matrices (matrixId=0 - matrixId=5) may be equal to or greater than 4×4 and equal to or less than 64×64 (ie, 1≤sizeId≤6). Thus, unlike the example of FIG. 16, a quantization matrix having a size of 2×2 (eg, sizeId=1) may not be constructed.

[238] An example syntax for implementing the quantization matrix encoding method described with reference to FIG. 19 is shown in FIG. 20.

[239] Referring to FIG. 20, based on the example of FIG. 19, quantization matrices (eg, matrixId=0 - matrixId=5) having a size of 4x4 or larger (eg, sizeId≥2) can be encoded using the scaling_list_data syntax (2010). In addition, all quantization matrices except the quantization matrix (eg, sizeId=6 andand matrixId%3!=0) having a size of 64x64 for the chroma component of the current block can be encoded using the scaling_list_data syntax (2020).

[240] As a result, a quantization matrix having a size of 2x2 (eg, sizeId=1) for the luma component (eg, matrixId%3=0) of the current block may not be encoded by the scaling_list_data syntax. In addition, a 2x2 quantization matrix (eg, sizeId=1) for the chrominance signal component (eg, matrixId%3!=0) of the current block encoded using an intra prediction mode (eg, CuPredMode=MODE_INTRA) may not encoded via scaling_list_data syntax.

[241] Thus, unlike the scaling_list_data syntax described above with reference to FIG. 18, according to the scaling_list_data syntax of FIG. 20, since a quantization matrix (for example, matrixId=1, 2, 4 or 5) having a size of 2×2 (for example, sizeId=1) is not encoded, by skipping the optional encoding process, it is possible to suppress an increase in the amount of transmitted overhead information and improve coding efficiency.

[242] Later in this document, a method for decoding a quantization matrix is described in detail.

[243] FIG. 21 is a flowchart illustrating a method for decoding a quantization matrix according to an embodiment of the present disclosure. The decoding method of FIG. 21 may be implemented by the image decoding equipment of FIG. 3. Specifically, steps S2110 to S2160 may be performed by the dequantization unit 220.

[244] Steps S2110 and S2120 of FIG. 21 may correspond to steps S1710 and S1720 of FIG. 17, respectively. In addition, steps S2130 and S2140 may correspond to step S1730 in FIG. 17. In addition, steps S2150 and S2160 may correspond to step S1740 in FIG. 17. Accordingly, the repeated description of FIG. 17 is omitted or simplified.

[245] Referring to FIG. 21, the image decoding equipment can decode, from the bit stream, quantization mode information of a method for constructing a quantization matrix for the current block (S2110).

[246] In an example, the quantization mode information may include first mode information indicating whether or not a quantization matrix is constructed based on a reference quantization matrix. The first mode information may be obtained by decoding a predefined flag (eg, scaling_list_pred_mode_flag).

[247] In another example, the quantization mode information may include first mode information and second mode information. The first mode information may indicate whether or not the quantization matrix for the current block is identical to the reference quantization matrix. The first mode information may be obtained by decoding a predefined first mode flag (eg, scaling_list_copy_mode_flag). The second mode information may indicate whether or not a quantization matrix for the current block is derived from a reference quantization matrix. Mode 2 information can be signaled via the bit stream only when the quantization matrix for the current block is not constructed such that it is identical to the reference quantization matrix (eg, scaling_list_copy_mode_flag=1). The second mode information may be obtained by decoding a predefined second mode flag (eg, scaling_list_pred_mode_flag).

[248] The image decoding equipment can determine whether or not a quantization matrix is constructed for the current block from the reference quantization matrix based on the quantization mode information obtained in step S2110 (S2120).

[249] In an example where the scaling_list_pred_mode_flag, which represents the first mode information, has a first value (eg, 0), the quantization matrix for the current block may be constructed such that it is identical to the reference quantization matrix.

[250] In another example, when the scaling_list_copy_mode_flag, which represents the first mode information, has a first value (eg, 0), the quantization matrix for the current block may be constructed such that it is identical to the reference quantization matrix. Alternatively, when the scaling_list_copy_mode_flag, which represents the first mode information, has a second value (for example, 1), and the scaling_list_pred_mode_flag, which represents the second mode information, has a first value (for example, 0), the quantization matrix for the current block may be derived from the reference matrix quantization.

[251] When the quantization matrix for the current block is constructed from the reference quantization matrix (“Yes” in S2120), the image decoding equipment can decode, from the bit stream, identification information of the reference quantization matrix to indicate the reference quantization matrix (S2130). The identification information of the quantization reference matrix may be signaled using a predefined syntax element, for example, scaling_list_pred_matrix_id_delta.

[252] The image decoding equipment may construct a quantization matrix for the current block based on the identification information of the reference quantization matrix obtained in step S2130 (S2140). For example, when scaling_list_pred_matrix_id_delta has the first value (eg, 0), the quantization matrix for the current block can be retrieved from the predefined default matrix. All one or more quantization matrix coefficients included in the default matrix may have the same value. In the example, the values of the quantization matrix coefficients included in the default matrix could be 16. In contrast, when scaling_list_pred_matrix_id_delta has a value (e.g. 1, 2, 3, etc.) other than the first value, the quantization matrix for the current block may be extracted from the reference quantization matrix specified based on the scaling_list_pred_matrix_id_delta, as described above with reference to Equation 1 and Equation 2.

[253] When the quantization matrix for the current block is not constructed from the reference quantization matrix ("No" in S2120), the image decoding equipment can decode, from the bit stream, the value of the quantization matrix for the current block (S2150). The quantization matrix value for the current block may be obtained by decoding predetermined syntax elements according to a predetermined scanning method (eg, diagonal scanning). For example, the image decoding equipment may obtain the quantization matrix value by decoding scaling_list_dc_coef_minus8 indicating the quantization matrix scaling factor for the current block, and scaling_list_delta_coef indicating the difference between the (i-1)th quantization matrix coefficient and the i-th quantization matrix coefficient in the quantization matrix.

[254] The image decoding equipment may construct a quantization matrix for the current block based on the quantization matrix value obtained in step S2150 (S2160).

[255] As described above, the quantization matrix decoding method of FIG. 21 may be implemented using the syntax (eg, scaling_list_data) described above with reference to FIG. 19 and 20. In this case, a quantization matrix having a size of 2×2 or less (eg, sizeId≤1) may not be decoded. As a result, since the optional decoding process for a 2×2 chroma block that is not resolved in the twin-tree structure can be skipped, decoding efficiency can be improved.

[256] Although the exemplary methods of the present disclosure described above are presented as a sequence of operations for clarity of description, it is not intended to limit the order in which the steps are performed, and the steps may be performed simultaneously or in a different order as necessary. To implement the method of the present disclosure, the described steps may further include other steps, may include the remaining steps except some steps, or may include other additional steps except some steps.

[257] In the present disclosure, image encoding equipment or image decoding equipment that performs a predetermined operation (step) may perform an operation (step) of confirming a condition or situation for executing the corresponding operation (step). For example, if it is described that a predetermined operation is performed when a predetermined condition is satisfied, the image encoding equipment or the image decoding equipment may perform the predetermined operation after determining whether or not the predetermined condition is satisfied.

[258] The various embodiments of the present disclosure do not constitute a list of all possible combinations and are intended to describe characteristic aspects of the present disclosure, and the matters described in the various embodiments may be applied independently or in combination of two or more of them.

[259] Various embodiments of the present disclosure may be implemented in hardware, firmware, software, or a combination of the above. If the present disclosure is implemented in hardware, the present disclosure may be implemented in application specific integrated circuits (ASICs), digital signal processors (DSPs), digital signal processing devices (DSPDs), programmable logic devices (PLDs), field programmable gate arrays. (FPGA), general processors, controllers, microcontrollers, microprocessors, etc.

[260] In addition, the image decoding equipment and image encoding equipment to which embodiments of the present disclosure apply may be included in a multimedia broadcast transceiver device, a mobile communication terminal, a home theater system video device, a digital cinema system video device, a surveillance camera, video chat device, real-time communication device such as video communication, mobile streaming device, storage medium, video recording camera, video-on-demand (VoD) service device, OTT video device ( video over networks), Internet streaming service device, 3D video device, video telephony system video device, medical video device, etc. and can be used to process video or data signals. For example, OTT video devices may include a gaming console, Blu-ray player, Internet-enabled television, home theater system, smartphone, tablet PC, digital video recorder (DVR), etc.

[261] FIG. 22 is a view showing a content streaming system to which an embodiment of the present disclosure is applicable.

[262] Referring to FIG. 22, the content streaming system to which the embodiment(s) of this document applies may mainly include an encoding server, a streaming server, a web server, a media storage, a user device, and a media input device.

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

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

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

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

[267] Examples of a user device may include a mobile phone, a smartphone, a laptop computer, a digital broadcast terminal, a personal digital assistant (PDA), a portable media player (PMP), a navigation device, a tablet PC, tablet PCs, ultrabooks, wearable devices (such as smart watches, smart glasses, head-mounted displays), digital TVs, desktop computers, digital signage system, etc.

[268] Each server in a content streaming system may operate as a distributed server, in which case data received from each server may be distributed.

[269] The scope of the disclosure includes software or computer-executable instructions (e.g., operating system, application, firmware, program, etc.) to enable operations according to the methods of various embodiments in hardware or computer, non-transitory computer-readable media having such software or instructions stored and executed in hardware or a computer.

Industrial applicability

[270] Embodiments of the present disclosure can be used to encode or decode an image.

Claims (43)

1. Decoding equipment for decoding images, containing: Memory device; And at least one processor coupled to the storage device, wherein the at least one processor is configured to: obtain quantization mode information for the current block from the bit stream; determining whether or not a quantization matrix is constructed for the current block from the reference quantization matrix based on the quantization mode information; And construct a quantization matrix for the current block, based on the result of the determination, wherein, based on the quantization matrix for the current block constructed from the reference quantization matrix, the quantization matrix for the current block is constructed based on the identification information of the reference quantization matrix, wherein, based on the quantization matrix for the current block, which is not constructed from the reference quantization matrix, the quantization matrix for the current block is constructed based on the value of the quantization matrix obtained from the bit stream, wherein, based on the current block, which is an internally predicted block of chrominance signals, a quantization matrix for the current block is constructed only when the size of the current block is greater than 2×2, wherein the quantization mode information includes a first mode flag indicating whether or not a quantization matrix for the current block is constructed such that it is identical to a reference quantization matrix, and a second mode flag indicating whether or not a quantization matrix for the current block is retrieved from the quantization reference matrix, and wherein the second value of the second mode flag, indicating the values of the quantization matrix for the current block, is explicitly signaled. 2. The decoding equipment of claim 1, wherein based on the first mode flag having the first value, a quantization matrix for the current block is constructed based on the identification information of the reference quantization matrix. 3. The decoding equipment of claim 1, wherein based on the first mode flag having the second value, a quantization matrix for the current block is constructed based on the quantization matrix value obtained from the bit stream. 4. The decoding equipment of claim 1, wherein based on the second mode flag having the first value, a quantization matrix for the current block is constructed based on the identification information of the reference quantization matrix. 5. The decoding equipment of claim 1, wherein based on the second mode flag having the second value, a quantization matrix for the current block is constructed based on the quantization matrix value obtained from the bit stream. 6. The decoding equipment of claim 1, wherein based on the identification information of the quantization reference matrix having the first value, the quantization matrix for the current block is constructed as a predetermined default matrix. 7. The decoding equipment of claim 6, wherein one or more coefficients of the quantization matrix included in the default matrix have an identical value. 8. The decoding equipment of claim 7, wherein all values of the quantization matrix coefficients included in the default matrix are 16. 9. The decoding equipment of claim 1, wherein the value of the quantization matrix is obtained by, from the bit stream, decoding a first syntax element indicating a scaling factor of the quantization matrix for the current block, and a second syntax element indicating the difference between the coefficients of the quantization matrix in the quantization matrix. 10. The decoding equipment of claim 1, wherein the quantization matrix for the current block has a configuration varying according to the prediction mode for the current block and the color component. 11. Encoding equipment for encoding images, containing: Memory device; And at least one processor coupled to the storage device, wherein the at least one processor is configured to: encode quantization mode information for the current block; determining whether or not a quantization matrix is constructed for the current block from the reference quantization matrix based on the quantization mode information; And encode quantization matrix information for the current block, based on the determination result, wherein, based on the quantization matrix for the current block constructed from the reference quantization matrix, the identification information of the reference quantization matrix is encoded, wherein, based on the quantization matrix for the current block, which is not constructed from the reference quantization matrix, the value of the quantization matrix for the current block is encoded, wherein, based on the current block, which is an internally predicted block of chrominance signals, a quantization matrix for the current block is constructed only when the size of the current block is greater than 2×2, wherein the quantization mode information includes a first mode flag indicating whether or not a quantization matrix for the current block is constructed such that it is identical to a reference quantization matrix, and a second mode flag indicating whether or not a quantization matrix for the current block is retrieved from the quantization reference matrix, and wherein the second value of the second mode flag, indicating the values of the quantization matrix for the current block, is explicitly signaled. 12. Image data transmission equipment containing: at least one processor configured to receive a bit stream generated by an encoding method performed by the encoding equipment for encoding images; And a transmitter configured to transmit a bit stream, In this case, the method of encoding images contains stages in which: encoding quantization mode information for the current block from the bitstream; determining whether or not a quantization matrix is constructed for the current block from the reference quantization matrix based on the quantization mode information; And encode quantization matrix information for the current block based on the determination result, wherein, based on the quantization matrix for the current block constructed from the reference quantization matrix, the identification information of the reference quantization matrix is encoded, wherein, based on the quantization matrix for the current block, which is not constructed from the reference quantization matrix, the value of the quantization matrix for the current block is encoded, wherein, based on the current block, which is an internally predicted block of chrominance signals, a quantization matrix for the current block is constructed only when the size of the current block is greater than 2×2, wherein the quantization mode information includes a first mode flag indicating whether or not a quantization matrix for the current block is constructed such that it is identical to a reference quantization matrix, and a second mode flag indicating whether or not a quantization matrix for the current block is retrieved from the quantization reference matrix, and wherein the second value of the second mode flag, indicating the values of the quantization matrix for the current block, is explicitly signaled.