WO2020185039A1

WO2020185039A1 - Residual coding method and device

Info

Publication number: WO2020185039A1
Application number: PCT/KR2020/003543
Authority: WO
Inventors: 유선미; 허진; 최장원; 최정아; 김승환
Original assignee: 엘지전자 주식회사
Priority date: 2019-03-14
Filing date: 2020-03-13
Publication date: 2020-09-17

Abstract

A video decoding method according to the present document is characterized by comprising: a step for obtaining residual information for a current block from a bitstream; a step for deriving non-zero transform coefficients for the current block on the basis of the residual information; a step for deriving residual samples on the basis of the non-zero transform coefficients; and a step for generating reconstructed samples on the basis of the residual samples. The step for deriving non-zero transform coefficients comprises: a step for determining whether to parse one sign flag information for a subblock in the current block; and a step for deriving sign information for the non-zero transform coefficients on the basis of whether the one sign flag information is parsed, wherein the one sign flag information is a syntax element indicating whether all of the non-zero transform coefficients for the subblock in the current block have the same sign.

Description

Residual coding method and apparatus

This document relates to video coding technology, for example, to a residual coding method and apparatus.

Recently, demand for high-resolution, high-quality video/video such as 4K or 8K or higher UHD (Ultra High Definition) video/video is increasing in various fields. As the image/video data becomes high-resolution and high-quality, the amount of information or bits to be transmitted increases relatively compared to the existing image/video data. When video/video data is stored by using it, the transmission cost and storage cost increase.

In addition, interest and demand for immersive media such as VR (Virtual Reality) and AR (Artificial Realtiy) contents or holograms are increasing in recent years, and videos/videos having different image characteristics from real images such as game images. Broadcasting about is increasing.

Accordingly, high-efficiency video/video compression technology is required in order to effectively compress, transmit, store, and reproduce information of high-resolution, high-quality video/video having various characteristics as described above.

The technical problem of this document is to provide a method and apparatus for increasing image coding efficiency.

Another technical problem of this document is to provide a method and apparatus for increasing the efficiency of residual coding.

Another technical problem of this document is to provide a method and apparatus for efficiently coding sign information for transform coefficients in coding residual information.

Another technical problem of this document is to provide a method and apparatus for effectively coding residual information for a block to which transform skip is applied.

According to an embodiment of the present document, an image decoding method performed by a decoding apparatus is provided. The method includes obtaining residual information for a current block from a bitstream, deriving non-zero transform coefficients for the current block based on the residual information, and the non-zero transform Deriving residual samples based on coefficients, generating reconstructed samples based on the residual samples, and deriving the non-zero transform coefficients comprises: a circle for a sub-block in the current block. Determining whether to parse one sign flag information, and deriving sign information for the non-zero transform coefficients based on whether the one sign flag information is parsed, wherein the one sign flag The information is characterized in that it is a syntax element indicating whether signs of non-zero transform coefficients for a subblock in the current block are all the same.

According to another embodiment of the present document, a video encoding method performed by an encoding device is provided. The method includes deriving non-zero transform coefficients for a current block, generating residual information for the non-zero transform coefficients, encoding image information including the residual information Including the step of, the encoding of the image information, determining whether to generate one sign flag information for the sub-block in the current block, the sign for the non-zero transform coefficients Encoding the image information including the one sign flag information based on the information, wherein the one sign flag information includes all signs of non-zero transform coefficients for the sub-blocks in the current block. It is characterized in that it is a syntax element indicating whether they are the same.

According to another embodiment of the present document, there is provided a digital storage medium storing encoded image information that causes the decoding apparatus to perform an image decoding method as a computer-readable digital storage medium.

This document can have various effects. For example, according to an embodiment of this document, it is possible to increase overall image/video compression efficiency. Alternatively, according to an embodiment of the present document, it is possible to increase the efficiency of residual coding. Alternatively, according to an embodiment of the present document, by signaling a flag indicating whether the signs of the transform coefficients are the same in consideration of the high possibility that the sign of the transform coefficients is concentrated on one side of the block to which the transform skip is applied , It is possible to save the bit amount of code information allocated to each of the transform coefficients and improve the overall residual coding efficiency. Alternatively, according to an embodiment of the present document, by placing a certain limit (eg, the number of context-coded bins, the number of transform coefficients, etc.) in the process of parsing the code information of the transform coefficients, the throughput of the residual coding It is possible to improve overall coding efficiency while maintaining.

The effects that can be obtained through the specific embodiments of this document are not limited to the effects listed above. For example, there may be various technical effects that a person having ordinary skill in the related art can understand or derive from this document. Accordingly, the specific effects of this document are not limited to those explicitly described in this document, and may include various effects that can be understood or derived from the technical features of this document.

1 schematically shows an example of a video/image coding system that can be applied to embodiments of this document.

FIG. 2 is a diagram schematically illustrating a configuration of a video/video encoding apparatus applicable to embodiments of the present document.

3 is a diagram schematically illustrating a configuration of a video/video decoding apparatus applicable to embodiments of the present document.

4 shows an example of a schematic video/video encoding method to which embodiments of this document are applicable.

5 shows an example of a schematic video/video decoding method to which embodiments of the present document are applicable.

6 schematically shows an example of an entropy encoding method to which embodiments of the present document can be applied, and FIG. 7 schematically shows an entropy encoding unit in an encoding device.

8 schematically shows an example of an entropy decoding method to which the embodiments of the present document are applicable, and FIG. 9 schematically shows an entropy decoding unit in a decoding apparatus.

10 exemplarily illustrates a context-adaptive binary arithmetic coding (CABAC) based coding method for coding a syntax element.

11 is a diagram illustrating an example of transform coefficients in a 4x4 block.

12 to 14 are diagrams for explaining an example of a method of coding sign information (eg, original sign flag information) for non-zero transform coefficients based on the number of non-zero transform coefficients.

15 is a flowchart schematically illustrating an image encoding method that can be performed by an encoding apparatus according to an embodiment of the present document.

16 is a flowchart schematically illustrating an image decoding method that can be performed by a decoding apparatus according to an embodiment of the present document.

17 shows an example of a content streaming system to which embodiments disclosed in this document can be applied.

In this document, various changes may be made and various embodiments may be provided, and specific embodiments will be illustrated in the drawings and described in detail. However, this is not intended to limit this document to a specific embodiment. Terms commonly used in this document are only used to describe a specific embodiment, and are not intended to limit the technical idea of this document. Singular expressions include plural expressions unless the context clearly indicates otherwise. In this document, terms such as "comprise" or "have" are intended to designate the existence of features, numbers, steps, actions, components, parts, or combinations thereof, described in the document, and one or more other features or numbers. It is to be understood that the possibility of addition or presence of, steps, actions, components, parts or combinations thereof does not preclude in advance.

Meanwhile, each of the components in the drawings described in this document is independently illustrated for convenience of description of different characteristic functions, and does not mean that each component is implemented as separate hardware or separate software. For example, two or more of the configurations may be combined to form one configuration, or one configuration may be divided into a plurality of configurations. Embodiments in which each configuration is integrated and/or separated are also included in the scope of the rights of this document, unless departing from the essence of this document.

In this document, "A or B" may mean "only A", "only B" or "both A and B". In other words, in this document, "A or B (A or B)" may be interpreted as "A and/or B (A and/or B)". For example, in this document "A, B or C (A, B or C)" means "only A", "only B", "only C", or "any and all combinations of A, B and C ( It can mean any combination of A, B and C)".

A forward slash (/) or comma (comma) used in this document may mean "and/or". For example, "A/B" can mean "A and/or B". Accordingly, "A/B" may mean "only A", "only B", or "both A and B". For example, "A, B, C" may mean "A, B or C".

In this document, "at least one of A and B" may mean "only A", "only B", or "both A and B". In addition, in this document, the expression "at least one of A or B" or "at least one of A and/or B" means "at least one A and B (at least one of A and B)" can be interpreted the same.

In addition, in this document, "at least one of A, B and C" means "only A", "only B", "only C", or "A, B and C May mean any combination of A, B and C". In addition, "at least one of A, B or C (at least one of A, B or C)" or "at least one of A, B and/or C (at least one of A, B and/or C)" It can mean "at least one of A, B and C".

In addition, parentheses used in this document may mean "for example". Specifically, when indicated as "prediction (intra prediction)", "intra prediction" may be proposed as an example of "prediction". In other words, "prediction" in this document is not limited to "intra prediction", and "intra prediction" may be suggested as an example of "prediction". In addition, even when displayed as "prediction (ie, intra prediction)", "intra prediction" may be proposed as an example of "prediction".

In this document, technical features that are individually described in one drawing may be implemented individually or at the same time.

This document is about video/image coding. For example, the method/embodiment disclosed in this document is a versatile video coding (VVC) standard, an essential video coding (EVC) standard, an AOMedia Video 1 (AV1) standard, a 2nd generation of audio video coding standard (AVS2), or a next-generation video/ It can be applied to a method disclosed in an image coding standard (ex. H.267 or H.268, etc.).

In this document, various embodiments related to video/image coding are presented, and the embodiments may be performed in combination with each other unless otherwise stated.

In this document, video may mean a set of images over time. A picture generally refers to a unit representing one image in a specific time period, and a slice/tile is a unit constituting a part of a picture in coding. A slice/tile may include one or more coding tree units (CTU). One picture may be composed of one or more slices/tiles. One picture may consist of one or more tile groups. One tile group may include one or more tiles. A brick may represent a rectangular region of CTU rows within a tile in a picture. A tile may be partitioned into multiple bricks, each of which consisting of one or more CTU rows within the tile. ). A tile that is not partitioned into multiple bricks may be also referred to as a brick. A brick scan may represent a specific sequential ordering of CTUs that partition a picture, the CTUs may be arranged in a CTU raster scan within a brick, and bricks in a tile may be sequentially arranged in a raster scan of the bricks of the tile. And, tiles in a picture may be sequentially arranged by raster scan of the tiles of the picture (A brick scan is a specific sequential ordering of CTUs partitioning a picture in which the CTUs are ordered consecutively in CTU raster scan in a brick. , bricks within a tile are ordered consecutively in a raster scan of the bricks of the tile, and tiles in a picture are ordered consecutively in a raster scan of the tiles of the picture). A tile is a rectangular region of CTUs within a particular tile column and a particular tile row in a picture. The tile column is a rectangular region of CTUs, the rectangular region has a height equal to the height of the picture, and the width may be specified by syntax elements in a picture parameter set (The tile column is a rectangular region of CTUs having a height equal to the height of the picture and a width specified by syntax elements in the picture parameter set). The tile row is a rectangular region of CTUs, the rectangular region has a width specified by syntax elements in a picture parameter set, and a height may be the same as the height of the picture (The tile row is a rectangular region of CTUs having a height specified by syntax elements in the picture parameter set and a width equal to the width of the picture). A tile scan may represent a specific sequential ordering of CTUs that partition a picture, the CTUs may be sequentially arranged in a CTU raster scan in a tile, and tiles in a picture may be sequentially arranged in a raster scan of the tiles of the picture. (A tile scan is a specific sequential ordering of CTUs partitioning a picture in which the CTUs are ordered consecutively in CTU raster scan in a tile whereas tiles in a picture are ordered consecutively in a raster scan of the tiles of the picture). A slice may include an integer number of bricks of a picture, and the integer number of bricks may be included in one NAL unit (A slice includes an integer number of bricks of a picture that may be exclusively contained in a single NAL unit). A slice may consist of either a number of complete tiles or only a consecutive sequence of complete bricks of one tile. ). Tile groups and slices can be used interchangeably in this document. For example, in this document, the tile group/tile group header may be referred to as a slice/slice header.

A pixel or pel may mean a minimum unit constituting one picture (or image). In addition,'sample' may be used as a term corresponding to a pixel. A sample may generally represent a pixel or a value of a pixel, may represent only a pixel/pixel value of a luma component, or may represent only a pixel/pixel value of a chroma component. Alternatively, the sample may mean a pixel value in the spatial domain, and when such a pixel value is converted to the frequency domain, it may mean a transform coefficient in the frequency domain.

A unit may represent a basic unit of image processing. The unit may include at least one of a specific area of a picture and information related to the corresponding area. One unit may include one luma block and two chroma (ex. cb, cr) blocks. The unit may be used interchangeably with terms such as a block or an area depending on the case. In general, the MxN block may include samples (or sample arrays) consisting of M columns and N rows, or a set (or array) of transform coefficients.

Hereinafter, exemplary embodiments of the present document will be described in more detail with reference to the accompanying drawings. Hereinafter, the same reference numerals are used for the same constituent elements in the drawings, and duplicate descriptions for the same constituent elements may be omitted.

Referring to FIG. 1, a video/image coding system may include a first device (a source device) and a second device (a receiving device). The source device may transmit the encoded video/image information or data in a file or streaming form to the receiving device through a digital storage medium or a network.

The source device may include a video source, an encoding device, and a transmission unit. The receiving device may include a receiving unit, a decoding device, and a renderer. The encoding device may be referred to as a video/image encoding device, and the decoding device may be referred to as a video/image decoding device. The transmitter may be included in the encoding device. The receiver may be included in the decoding device. The renderer may include a display unit, and the display unit may be configured as a separate device or an external component.

The video source may acquire a video/image through a process of capturing, synthesizing, or generating a video/image. The video source may include a video/image capturing device and/or a video/image generating device. The video/image capture device may include, for example, one or more cameras, a video/image archive including previously captured video/images, and the like. The video/image generating device may include, for example, a computer, a tablet and a smartphone, and may (electronically) generate a video/image. For example, a virtual video/image may be generated through a computer or the like, and in this case, a video/image capturing process may be substituted as a process of generating related data.

The encoding device may encode the input video/video. The encoding apparatus may perform a series of procedures such as prediction, transformation, and quantization for compression and coding efficiency. The encoded data (encoded video/video information) may be output in the form of a bitstream.

The transmission unit may transmit the encoded video/video information or data output in the form of a bitstream to the reception unit of the receiving device through a digital storage medium or a network in a file or streaming form. Digital storage media may include various storage media such as USB, SD, CD, DVD, Blu-ray, HDD, and SSD. The transmission unit may include an element for generating a media file through a predetermined file format, and may include an element for transmission through a broadcast/communication network. The receiver may receive/extract the bitstream and transmit it to the decoding device.

The decoding device may decode the video/image by performing a series of procedures such as inverse quantization, inverse transformation, and prediction corresponding to the operation of the encoding device.

The renderer can render the decoded video/video. The rendered video/image may be displayed through the display unit.

FIG. 2 is a diagram schematically illustrating a configuration of a video/video encoding apparatus applicable to embodiments of the present document. Hereinafter, the video encoding device may include an image encoding device.

2, the encoding device 200 includes an image partitioner 210, a predictor 220, a residual processor 230, an entropy encoder 240, and It may be configured to include an adder 250, a filter 260, and a memory 270. The prediction unit 220 may include an inter prediction unit 221 and an intra prediction unit 222. The residual processing unit 230 may include a transform unit 232, a quantizer 233, an inverse quantizer 234, and an inverse transformer 235. The residual processing unit 230 may further include a subtractor 231. The addition unit 250 may be referred to as a reconstructor or a recontructged block generator. The image segmentation unit 210, the prediction unit 220, the residual processing unit 230, the entropy encoding unit 240, the addition unit 250, and the filtering unit 260 described above may include one or more hardware components ( For example, it may be configured by an encoder chipset or a processor). In addition, the memory 270 may include a decoded picture buffer (DPB), and may be configured by a digital storage medium. The hardware component may further include the memory 270 as an internal/external component.

The image segmentation unit 210 may divide an input image (or picture, frame) input to the encoding apparatus 200 into one or more processing units. For example, the processing unit may be referred to as a coding unit (CU). In this case, the coding unit is recursively divided according to the QTBTTT (Quad-tree binary-tree ternary-tree) structure from a coding tree unit (CTU) or a largest coding unit (LCU). I can. For example, one coding unit may be divided into a plurality of coding units of a deeper depth based on a quad tree structure, a binary tree structure, and/or a ternary structure. In this case, for example, a quad tree structure may be applied first, and a binary tree structure and/or a ternary structure may be applied later. Alternatively, the binary tree structure may be applied first. The coding procedure according to this document may be performed based on the final coding unit that is no longer divided. In this case, based on the coding efficiency according to the image characteristics, the maximum coding unit can be directly used as the final coding unit, or if necessary, the coding unit is recursively divided into coding units of lower depth to be optimal. A coding unit of the size of may be used as the final coding unit. Here, the coding procedure may include a procedure such as prediction, transformation, and restoration described later. As another example, the processing unit may further include a prediction unit (PU) or a transform unit (TU). In this case, the prediction unit and the transform unit may be divided or partitioned from the above-described final coding unit, respectively. The prediction unit may be a unit of sample prediction, and the transform unit may be a unit for inducing a transform coefficient and/or a unit for inducing a residual signal from the transform coefficient.

The unit may be used interchangeably with terms such as a block or an area depending on the case. In general, the MxN block may represent a set of samples or transform coefficients consisting of M columns and N rows. In general, a sample may represent a pixel or a value of a pixel, may represent only a pixel/pixel value of a luminance component, or may represent only a pixel/pixel value of a saturation component. A sample may be used as a term corresponding to one picture (or image) as a pixel or pel.

The encoding apparatus 200 subtracts the prediction signal (predicted block, prediction sample array) output from the inter prediction unit 221 or the intra prediction unit 222 from the input video signal (original block, original sample array) to make a residual. A signal (residual signal, residual block, residual sample array) may be generated, and the generated residual signal is transmitted to the converter 232. In this case, as illustrated, a unit that subtracts the prediction signal (prediction block, prediction sample array) from the input image signal (original block, original sample array) in the encoder 200 may be referred to as a subtraction unit 231. The prediction unit may perform prediction on a block to be processed (hereinafter, referred to as a current block) and generate a predicted block including prediction samples for the current block. The prediction unit may determine whether intra prediction or inter prediction is applied in units of the current block or CU. The prediction unit may generate various information related to prediction, such as prediction mode information, as described later in the description of each prediction mode, and transmit it to the entropy encoding unit 240. The information on prediction may be encoded by the entropy encoding unit 240 and output in the form of a bitstream.

The intra prediction unit 222 may predict the current block by referring to samples in the current picture. The referenced samples may be located in the vicinity of the current block or may be located apart according to the prediction mode. In intra prediction, prediction modes may include a plurality of non-directional modes and a plurality of directional modes. The non-directional mode may include, for example, a DC mode and a planar mode (Planar mode). The directional mode may include, for example, 33 directional prediction modes or 65 directional prediction modes according to a detailed degree of the prediction direction. However, this is an example, and more or less directional prediction modes may be used depending on the setting. The intra prediction unit 222 may determine a prediction mode applied to the current block by using the prediction mode applied to the neighboring block.

The inter prediction unit 221 may derive a predicted block for the current block based on a reference block (reference sample array) specified by a motion vector on the reference picture. In this case, in order to reduce the amount of motion information transmitted in the inter prediction mode, motion information may be predicted in units of blocks, subblocks, or samples based on correlation between motion information between neighboring blocks and the current block. The motion information may include a motion vector and a reference picture index. The motion information may further include inter prediction direction (L0 prediction, L1 prediction, Bi prediction, etc.) information. In the case of inter prediction, the neighboring block may include a spatial neighboring block existing in the current picture and a temporal neighboring block existing in the reference picture. The reference picture including the reference block and the reference picture including the temporal neighboring block may be the same or different. The temporal neighboring block may be referred to by a name such as a collocated reference block, a colCU, or the like, and a reference picture including the temporal neighboring block may be referred to as a collocated picture (colPic). May be. For example, the inter prediction unit 221 constructs a motion information candidate list based on neighboring blocks, and provides information indicating which candidate is used to derive a motion vector and/or a reference picture index of the current block. Can be generated. Inter prediction may be performed based on various prediction modes. For example, in the case of a skip mode and a merge mode, the inter prediction unit 221 may use motion information of a neighboring block as motion information of a current block. In the case of the skip mode, unlike the merge mode, a residual signal may not be transmitted. In the case of motion vector prediction (MVP) mode, the motion vector of the current block is calculated by using the motion vector of the neighboring block as a motion vector predictor and signaling a motion vector difference. I can instruct.

The prediction unit 220 may generate a prediction signal based on various prediction methods to be described later. For example, the prediction unit may apply intra prediction or inter prediction for prediction of one block, as well as simultaneously apply intra prediction and inter prediction. This can be called combined inter and intra prediction (CIIP). In addition, the prediction unit may be based on an intra block copy (IBC) prediction mode or a palette mode to predict a block. The IBC prediction mode or the palette mode may be used for content image/video coding such as a game, for example, screen content coding (SCC). IBC basically performs prediction in the current picture, but can be performed similarly to inter prediction in that it derives a reference block in the current picture. That is, the IBC may use at least one of the inter prediction techniques described in this document. The palette mode can be viewed as an example of intra coding or intra prediction. When the palette mode is applied, a sample value in a picture may be signaled based on information about a palette table and a palette index.

The prediction signal generated by the prediction unit (including the inter prediction unit 221 and/or the intra prediction unit 222) may be used to generate a reconstructed signal or may be used to generate a residual signal. The transform unit 232 may generate transform coefficients by applying a transform technique to the residual signal. For example, the transformation technique is DCT (Discrete Cosine Transform), DST (Discrete Sine Transform), KLT (

), GBT (Graph-Based Transform), or CNT (Conditionally Non-linear Transform) may include at least one. Here, GBT refers to the transformation obtained from this graph when the relationship information between pixels is expressed in a graph. CNT refers to a transformation obtained based on generating a prediction signal using all previously reconstructed pixels. In addition, the conversion process may be applied to a pixel block having the same size of a square, or may be applied to a block having a variable size other than a square.

The quantization unit 233 quantizes the transform coefficients and transmits it to the entropy encoding unit 240, and the entropy encoding unit 240 encodes the quantized signal (information on quantized transform coefficients) and outputs it as a bitstream. have. The information on the quantized transform coefficients may be called residual information. The quantization unit 233 may rearrange the quantized transform coefficients in the form of blocks into a one-dimensional vector form based on a coefficient scan order, and the quantized transform coefficients in the form of the one-dimensional vector It is also possible to generate information about transform coefficients. The entropy encoding unit 240 may perform various encoding methods such as exponential Golomb, context-adaptive variable length coding (CAVLC), and context-adaptive binary arithmetic coding (CABAC). The entropy encoding unit 240 may encode together or separately information necessary for video/image reconstruction (eg, values of syntax elements) in addition to quantized transform coefficients. The encoded information (eg, encoded video/video information) may be transmitted or stored in a bitstream format in units of network abstraction layer (NAL) units. The video/video information may further include information on various parameter sets, such as an adaptation parameter set (APS), a picture parameter set (PPS), a sequence parameter set (SPS), or a video parameter set (VPS). In addition, the video/video information may further include general constraint information. In this document, information and/or syntax elements transmitted/signaled from the encoding device to the decoding device may be included in the video/video information. The video/video information may be encoded through the above-described encoding procedure and included in the bitstream. The bitstream may be transmitted through a network or may be stored in a digital storage medium. Here, the network may include a broadcasting network and/or a communication network, and the digital storage medium may include various storage media such as USB, SD, CD, DVD, Blu-ray, HDD, and SSD. For the signal output from the entropy encoding unit 240, a transmission unit (not shown) for transmitting and/or a storage unit (not shown) for storing may be configured as an internal/external element of the encoding apparatus 200, or the transmission unit It may be included in the entropy encoding unit 240.

The quantized transform coefficients output from the quantization unit 233 may be used to generate a prediction signal. For example, a residual signal (residual block or residual samples) may be restored by applying inverse quantization and inverse transform to the quantized transform coefficients through the inverse quantization unit 234 and the inverse transform unit 235. The addition unit 155 adds the reconstructed residual signal to the prediction signal output from the inter prediction unit 221 or the intra prediction unit 222 to obtain a reconstructed signal (restored picture, reconstructed block, reconstructed sample array). Can be created. When there is no residual for a block to be processed, such as when the skip mode is applied, the predicted block may be used as a reconstructed block. The addition unit 250 may be referred to as a restoration unit or a restoration block generation unit. The generated reconstructed signal may be used for intra prediction of the next processing target block in the current picture, and may be used for inter prediction of the next picture through filtering as described later.

Meanwhile, luma mapping with chroma scaling (LMCS) may be applied during picture encoding and/or reconstruction.

The filtering unit 260 may improve subjective/objective image quality by applying filtering to the reconstructed signal. For example, the filtering unit 260 may apply various filtering methods to the reconstructed picture to generate a modified reconstructed picture, and the modified reconstructed picture may be converted to the memory 270, specifically, the DPB of the memory 270. Can be saved on. The various filtering methods may include, for example, deblocking filtering, sample adaptive offset, adaptive loop filter, bilateral filter, and the like. The filtering unit 260 may generate a variety of filtering information and transmit it to the entropy encoding unit 240 as described later in the description of each filtering method. The filtering information may be encoded by the entropy encoding unit 240 and output in the form of a bitstream.

The modified reconstructed picture transmitted to the memory 270 may be used as a reference picture in the inter prediction unit 221. When inter prediction is applied through this, the encoding device may avoid prediction mismatch between the encoding device 100 and the decoding device, and may improve encoding efficiency.

The memory 270 DPB may store the modified reconstructed picture for use as a reference picture in the inter prediction unit 221. The memory 270 may store motion information of a block from which motion information in a current picture is derived (or encoded) and/or motion information of blocks in a picture that have already been reconstructed. The stored motion information may be transferred to the inter prediction unit 221 in order to be used as motion information of spatial neighboring blocks or motion information of temporal neighboring blocks. The memory 270 may store reconstructed samples of reconstructed blocks in the current picture, and may be transmitted to the intra prediction unit 222.

Referring to FIG. 3, the decoding apparatus 300 includes an entropy decoder 310, a residual processor 320, a predictor 330, an adder 340, and a filtering unit. It may be configured to include (filter, 350) and memory (memoery) 360. The prediction unit 330 may include an inter prediction unit 331 and an intra prediction unit 332. The residual processing unit 320 may include a dequantizer 321 and an inverse transformer 321. The entropy decoding unit 310, the residual processing unit 320, the prediction unit 330, the addition unit 340, and the filtering unit 350 described above are one hardware component (for example, a decoder chipset or a processor). ) Can be configured. In addition, the memory 360 may include a decoded picture buffer (DPB), and may be configured by a digital storage medium. The hardware component may further include the memory 360 as an internal/external component.

When a bitstream including video/image information is input, the decoding apparatus 300 may reconstruct an image in response to a process in which the video/image information is processed by the encoding apparatus of FIG. 2. For example, the decoding apparatus 300 may derive units/blocks based on block division related information obtained from the bitstream. The decoding device 300 may perform decoding using a processing unit applied in the encoding device. Thus, the processing unit of decoding may be, for example, a coding unit, and the coding unit may be divided from a coding tree unit or a maximum coding unit along a quad tree structure, a binary tree structure and/or a ternary tree structure. One or more transform units may be derived from the coding unit. In addition, the reconstructed image signal decoded and output through the decoding device 300 may be reproduced through the playback device.

The decoding apparatus 300 may receive a signal output from the encoding apparatus of FIG. 2 in the form of a bitstream, and the received signal may be decoded through the entropy decoding unit 310. For example, the entropy decoding unit 310 may parse the bitstream to derive information (eg, video/video information) necessary for image restoration (or picture restoration). The video/video information may further include information on various parameter sets, such as an adaptation parameter set (APS), a picture parameter set (PPS), a sequence parameter set (SPS), or a video parameter set (VPS). In addition, the video/video information may further include general constraint information. The decoding apparatus may further decode the picture based on the information on the parameter set and/or the general restriction information. Signaled/received information and/or syntax elements described later in this document may be decoded through the decoding procedure and obtained from the bitstream. For example, the entropy decoding unit 310 decodes information in the bitstream based on a coding method such as exponential Golomb coding, CAVLC, or CABAC, and a value of a syntax element required for image restoration, a quantized value of a transform coefficient related to a residual. Can be printed. In more detail, the CABAC entropy decoding method receives a bin corresponding to each syntax element in a bitstream, and includes information on a syntax element to be decoded and information on a neighboring and decoding target block or information on a symbol/bin decoded in a previous step. A context model is determined using the context model, and a symbol corresponding to the value of each syntax element can be generated by performing arithmetic decoding of the bin by predicting the probability of occurrence of a bin according to the determined context model. have. In this case, the CABAC entropy decoding method may update the context model using information of the decoded symbol/bin for the context model of the next symbol/bin after the context model is determined. Among the information decoded by the entropy decoding unit 310, information about prediction is provided to a prediction unit (inter prediction unit 332 and intra prediction unit 331), and entropy decoding is performed by the entropy decoding unit 310. The dual value, that is, quantized transform coefficients and related parameter information may be input to the residual processing unit 320. The residual processing unit 320 may derive a residual signal (a residual block, residual samples, and a residual sample array). In addition, information about filtering among information decoded by the entropy decoding unit 310 may be provided to the filtering unit 350. Meanwhile, a receiver (not shown) for receiving a signal output from the encoding device may be further configured as an inner/outer element of the decoding device 300, or the receiver may be a component of the entropy decoding unit 310. Meanwhile, the decoding apparatus according to this document may be called a video/video/picture decoding apparatus, and the decoding apparatus can be divided into an information decoder (video/video/picture information decoder) and a sample decoder (video/video/picture sample decoder). May be. The information decoder may include the entropy decoding unit 310, and the sample decoder includes the inverse quantization unit 321, an inverse transform unit 322, an addition unit 340, a filtering unit 350, and a memory 360. ), an inter prediction unit 332 and an intra prediction unit 331 may be included.

The inverse quantization unit 321 may inverse quantize the quantized transform coefficients and output transform coefficients. The inverse quantization unit 321 may rearrange the quantized transform coefficients in a two-dimensional block shape. In this case, the rearrangement may be performed based on the coefficient scan order performed by the encoding device. The inverse quantization unit 321 may perform inverse quantization on quantized transform coefficients by using a quantization parameter (for example, quantization step size information) and obtain transform coefficients.

The inverse transform unit 322 obtains a residual signal (residual block, residual sample array) by inverse transforming the transform coefficients.

The prediction unit may perform prediction on the current block and generate a predicted block including prediction samples for the current block. The prediction unit may determine whether intra prediction or inter prediction is applied to the current block based on the information about the prediction output from the entropy decoding unit 310, and may determine a specific intra/inter prediction mode.

The prediction unit 320 may generate a prediction signal based on various prediction methods to be described later. For example, the prediction unit may apply intra prediction or inter prediction for prediction of one block, as well as simultaneously apply intra prediction and inter prediction. This can be called combined inter and intra prediction (CIIP). In addition, the prediction unit may be based on an intra block copy (IBC) prediction mode or a palette mode to predict a block. The IBC prediction mode or the palette mode may be used for content image/video coding such as a game, for example, screen content coding (SCC). IBC basically performs prediction in the current picture, but can be performed similarly to inter prediction in that it derives a reference block in the current picture. That is, the IBC may use at least one of the inter prediction techniques described in this document. The palette mode can be viewed as an example of intra coding or intra prediction. When the palette mode is applied, information about a palette table and a palette index may be included in the video/video information and signaled.

The intra prediction unit 331 may predict the current block by referring to samples in the current picture. The referenced samples may be located in the vicinity of the current block or may be located apart according to the prediction mode. In intra prediction, prediction modes may include a plurality of non-directional modes and a plurality of directional modes. The intra prediction unit 331 may determine a prediction mode applied to the current block by using the prediction mode applied to the neighboring block.

The inter prediction unit 332 may derive a predicted block for the current block based on a reference block (reference sample array) specified by a motion vector on the reference picture. In this case, in order to reduce the amount of motion information transmitted in the inter prediction mode, motion information may be predicted in units of blocks, subblocks, or samples based on correlation between motion information between neighboring blocks and the current block. The motion information may include a motion vector and a reference picture index. The motion information may further include inter prediction direction (L0 prediction, L1 prediction, Bi prediction, etc.) information. In the case of inter prediction, the neighboring block may include a spatial neighboring block existing in the current picture and a temporal neighboring block existing in the reference picture. For example, the inter prediction unit 332 may construct a motion information candidate list based on neighboring blocks, and derive a motion vector and/or a reference picture index of the current block based on the received candidate selection information. Inter prediction may be performed based on various prediction modes, and the information about the prediction may include information indicating a mode of inter prediction for the current block.

The addition unit 340 is reconstructed by adding the obtained residual signal to the prediction signal (predicted block, prediction sample array) output from the prediction unit (including the inter prediction unit 332 and/or the intra prediction unit 331). Signals (restored pictures, reconstructed blocks, reconstructed sample arrays) can be generated. When there is no residual for a block to be processed, such as when the skip mode is applied, the predicted block may be used as a reconstructed block.

The addition unit 340 may be referred to as a restoration unit or a restoration block generation unit. The generated reconstructed signal may be used for intra prediction of the next processing target block in the current picture, may be output through filtering as described later, or may be used for inter prediction of the next picture.

Meanwhile, luma mapping with chroma scaling (LMCS) may be applied in the picture decoding process.

The filtering unit 350 may improve subjective/objective image quality by applying filtering to the reconstructed signal. For example, the filtering unit 350 may generate a modified reconstructed picture by applying various filtering methods to the reconstructed picture, and the modified reconstructed picture may be converted to the memory 360, specifically, the DPB of the memory 360. Can be transferred to. The various filtering methods may include, for example, deblocking filtering, sample adaptive offset, adaptive loop filter, bilateral filter, and the like.

The (modified) reconstructed picture stored in the DPB of the memory 360 may be used as a reference picture in the inter prediction unit 332. The memory 360 may store motion information of a block from which motion information in a current picture is derived (or decoded) and/or motion information of blocks in a picture that have already been reconstructed. The stored motion information may be transmitted to the inter prediction unit 332 in order to be used as motion information of spatial neighboring blocks or motion information of temporal neighboring blocks. The memory 360 may store reconstructed samples of reconstructed blocks in the current picture, and may be transmitted to the intra prediction unit 331.

In this document, the embodiments described in the filtering unit 260, the inter prediction unit 221, and the intra prediction unit 222 of the encoding apparatus 200 are respectively the filtering unit 350 and the inter prediction of the decoding apparatus 300. The same or corresponding to the unit 332 and the intra prediction unit 331 may be applied.

As described above, prediction is performed to increase compression efficiency in performing video coding. Through this, a predicted block including prediction samples for a current block as a coding target block may be generated. Here, the predicted block includes prediction samples in the spatial domain (or pixel domain). The predicted block is derived equally from the encoding device and the decoding device, and the encoding device signals information about the residual between the original block and the predicted block (residual information), not the original sample value of the original block, to the decoding device. Image coding efficiency can be improved. The decoding apparatus may derive a residual block including residual samples based on the residual information, generate a reconstructed block including reconstructed samples by adding the residual block and the predicted block, and reconstruct including the reconstructed blocks You can create a picture.

The residual information may be generated through transformation and quantization procedures. For example, the encoding apparatus derives a residual block between an original block and a predicted block, performs a transformation procedure on residual samples (residual sample array) included in the residual block to derive transform coefficients, and transforms By performing a quantization procedure on the coefficients, quantized transform coefficients may be derived, and related residual information may be signaled to a decoding apparatus (through a bitstream). Here, the residual information may include information such as value information of quantized transform coefficients, position information, a transform technique, a transform kernel, and a quantization parameter. The decoding apparatus may perform an inverse quantization/inverse transform procedure based on the residual information and derive residual samples (or residual blocks). The decoding apparatus may generate a reconstructed picture based on the predicted block and the residual block. The encoding apparatus may also inverse quantize/inverse transform quantized transform coefficients for reference for inter prediction of a picture to derive a residual block, and generate a reconstructed picture based on this.

The following drawings are prepared to describe a specific example of this document. Since the names of specific devices described in the drawings, specific terms or names (eg, syntax names, etc.) are presented by way of example, the technical features of this document are not limited to the specific names used in the following drawings.

The method disclosed in FIG. 4 may be performed by the encoding apparatus 200 of FIG. 2 described above. Specifically, S400 may be performed by the inter prediction unit 221 or the intra prediction unit 222 of the encoding apparatus 200, and S410, S420, S430, and S440 are respectively subtracted by the subtraction unit 231 of the encoding apparatus 200. ), the transform unit 232, the quantization unit 233, and the entropy encoding unit 240.

Referring to FIG. 4, the encoding apparatus may derive prediction samples through prediction of a current block (S400). The encoding apparatus may determine whether to perform inter prediction or intra prediction on the current block, and may determine a specific inter prediction mode or a specific intra prediction mode based on RD cost. Depending on the determined mode, the encoding apparatus may derive prediction samples for the current block.

The encoding apparatus may derive residual samples by comparing original samples for the current block and prediction samples (S410).

The encoding apparatus may derive transform coefficients through a transform procedure for residual samples (S420) and quantize the derived transform coefficients to derive quantized transform coefficients (S430).

The encoding apparatus may encode image information including prediction information and residual information, and output the encoded image information in the form of a bitstream (S440). The prediction information is information related to a prediction procedure and may include prediction mode information and information about motion information (eg, when inter prediction is applied). The residual information may include information on quantized transform coefficients. The residual information may be entropy coded.

The output bitstream may be delivered to a decoding device through a storage medium or a network.

The method disclosed in FIG. 5 may be performed by the decoding apparatus 300 of FIG. 3 described above. Specifically, S500 may be performed by the inter prediction unit 332 or the intra prediction unit 331 of the decoding apparatus 300. The procedure of deriving values of related syntax elements by decoding prediction information included in the bitstream in S500 may be performed by the entropy decoding unit 310 of the decoding apparatus 300. S510, S520, S530, and S540 may be performed by the entropy decoding unit 310, the inverse quantization unit 321, the inverse transform unit 322, and the addition unit 340 of the decoding apparatus 300, respectively.

Referring to FIG. 5, the decoding apparatus may perform an operation corresponding to an operation performed by the encoding apparatus. The decoding apparatus may perform inter prediction or intra prediction on the current block based on the received prediction information and derive prediction samples (S500).

The decoding apparatus may derive quantized transform coefficients for the current block based on the received residual information (S510). The decoding apparatus may derive quantized transform coefficients from residual information through entropy decoding.

The decoding apparatus may inverse quantize the quantized transform coefficients to derive transform coefficients (S520).

The decoding apparatus derives residual samples through an inverse transform procedure for transform coefficients (S530).

The decoding apparatus may generate reconstructed samples for the current block based on the prediction samples and the residual samples, and generate a reconstructed picture based on this. (S540). As described above, the in-loop filtering procedure may be further applied to the reconstructed picture after that.

Meanwhile, as described above, the encoding device performs entropy encoding based on various encoding methods such as exponential Golomb, context-adaptive variable length coding (CAVLC), and context-adaptive binary arithmetic coding (CABAC). Can be done. In addition, the decoding apparatus may perform entropy decoding based on a coding method such as exponential Golomb coding, CAVLC, or CABAC. Hereinafter, an entropy encoding/decoding procedure will be described.

6 schematically shows an example of an entropy encoding method to which embodiments of the present document can be applied, and FIG. 7 schematically shows an entropy encoding unit in an encoding device. The entropy encoding unit in the encoding apparatus of FIG. 7 may be applied to the entropy encoding unit 240 of the encoding apparatus 200 of FIG. 2 as described above or to correspond to each other.

6 and 7, an encoding apparatus (entropy encoding unit) may perform an entropy coding procedure for image/video information. The image/video information may include partitioning-related information, prediction-related information (ex.inter/intra prediction classification information, intra prediction mode information, inter prediction mode information, etc.), residual information, in-loop filtering-related information, and the like, Or it may include various syntax elements related thereto. Entropy coding may be performed in units of syntax elements. S600 to S610 may be performed by the entropy encoding unit 240 of the encoding apparatus 200 of FIG. 2 described above.

The encoding device may perform binarization on the target syntax element (S600). Here, binarization may be based on various binarization methods such as the Truncated Rice binarization process and the Fixed-length binarization process, and the binarization method for the target syntax element may be predefined. The binarization procedure may be performed by the binarization unit 242 in the entropy encoding unit 240.

The encoding device may perform entropy encoding on the target syntax element (S610). The encoding device is based on an entropy coding technique such as context-adaptive arithmetic coding (CABAC) or context-adaptive variable length coding (CAVLC) based on a regular coding-based (context-based) or bypassing the bin string of the target syntax element. It can encode based on coding, and its output can be included in the bitstream. The entropy encoding procedure may be performed by the entropy encoding processing unit 243 in the entropy encoding unit 240. As described above, the bitstream can be delivered to a decoding device through a (digital) storage medium or a network.

8 schematically shows an example of an entropy decoding method to which the embodiments of the present document are applicable, and FIG. 9 schematically shows an entropy decoding unit in a decoding apparatus. The entropy decoding unit in the decoding apparatus of FIG. 9 may also be applied to the entropy decoding unit 310 of the decoding apparatus 300 of FIG. 3 as described above.

8 and 9, a decoding apparatus (entropy decoding unit) may decode encoded image/video information. The image/video information may include partitioning-related information, prediction-related information (ex.inter/intra prediction classification information, intra prediction mode information, inter prediction mode information, etc.), residual information, in-loop filtering-related information, and the like, Or it may include various syntax elements related thereto. Entropy coding may be performed in units of syntax elements. S700 to S710 may be performed by the entropy decoding unit 310 of the decoding apparatus 300 of FIG. 3 described above.

The decoding apparatus may perform binarization on the target syntax element (S800). Here, binarization may be based on various binarization methods such as the Truncated Rice binarization process and the Fixed-length binarization process, and the binarization method for the target syntax element may be predefined. The decoding apparatus may derive available bin strings (empty string candidates) for available values of a target syntax element through a binarization procedure. The binarization procedure may be performed by the binarization unit 312 in the entropy decoding unit 310.

The decoding apparatus may perform entropy decoding on the target syntax element (S810). The decoding apparatus sequentially decodes and parses each bin for the target syntax element from the input bit(s) in the bitstream, and compares the derived bin string with the available bin strings for the corresponding syntax element. If the derived empty string is the same as one of the available empty strings, a value corresponding to the corresponding empty string may be derived as a value of the corresponding syntax element. If not, it is possible to perform the above-described procedure again after further parsing the next bit in the bitstream. Through this process, the information can be signaled using variable length bits without using a start bit or an end bit for specific information (specific syntax element) in the bitstream. Through this, relatively fewer bits can be allocated to a low value, and overall coding efficiency can be improved.

The decoding apparatus may perform context-based or bypass-based decoding of each bin in the bin string from the bitstream based on an entropy coding technique such as CABAC or CAVLC. Here, the bitstream may include various information for video/video decoding as described above. As described above, the bitstream can be delivered to a decoding device through a (digital) storage medium or a network.

In this document, a table (syntax table) including syntax elements may be used to indicate signaling of information from the encoding device to the decoding device. The order of syntax elements in a syntax table used in this document may indicate a parsing order of syntax elements from a bitstream. The encoding device may configure and encode a syntax table so that the syntax elements can be parsed by the decoding device in parsing order, and the decoding device parses and decodes the syntax elements of the corresponding syntax table from the bitstream according to the parsing order, Can be obtained.

As described above, some or all of the video/image information may be entropy-encoded by the entropy encoding unit 240, and some or all of the video/image information may be entropy-decoded by the entropy decoding unit 310. . In this case, as an example, syntax element(s) included in residual information to be described later may be entropy-coded (encoded/decoded) based on CABAC.

Referring to FIG. 10, in a CABAC coding process, when an input signal is a syntax element other than a binary value, the input signal may be first binarized and converted into a binary value. When the input signal is already a binary value (ie, the input signal is a binary value), the input signal can be bypassed without undergoing binarization. Here, each

binary number

0 or 1 constituting the binary value may be referred to as a bin. For example, if the binary string after binarization is 110, each of 1, 1, and 0 is referred to as one bin. The bean(s) for one syntax element may represent the value of the corresponding syntax element.

The binarized bins of the syntax element may be input to a regular encoding engine or a bypass encoding engine. The regular encoding engine may allocate a context model that reflects a probability value to the corresponding bean, and encode the corresponding bean based on the allocated context model. The regular encoding engine may update the context model for the corresponding bean after encoding each bean. The bin encoded as described above may be referred to as a context-coded bin.

The bypass encoding engine omits the procedure of estimating the probability of the input bin and the procedure of updating the probability model applied to the corresponding bin after encoding. That is, when bypass encoding is applied, an input bin may be encoded by applying a uniform probability distribution instead of allocating a context model, thereby improving the encoding speed. The bin encoded as described above may be referred to as a bypass bin.

Entropy encoding may determine whether to perform encoding through a regular encoding engine or a bypass encoding engine, and switch an encoding path. Entropy decoding may perform the same process as the above-described entropy encoding in reverse order.

For example, when the syntax element is decoded based on the context model, the decoding device may receive a bin corresponding to the syntax element through the bitstream, and the syntax element and decoding information of the decoding object block or neighboring block or a previous step A context model can be determined using information of the symbol/bin decoded in, and arithmetic decoding of the bin is performed by predicting the probability of occurrence of the received bin according to the determined context model. , The value of the syntax element can be derived. Thereafter, the context model of the next decoded bean may be updated with the determined context model.

Also, for example, when the syntax element is bypass decoded, the decoding apparatus may receive a bin corresponding to the syntax element through a bitstream, and may decode an input bin by applying a uniform probability distribution. In this case, the decoding apparatus may omit the procedure of deriving the context model of the syntax element and the procedure of updating the context model applied to the bin after decoding.

As described above, residual samples may be derived into quantized transform coefficients through a transform and quantization process. Quantized transform coefficients may also be called transform coefficients. In this case, the transform coefficients within the block may be signaled in the form of residual information. The residual information may include residual coding syntax. That is, the encoding device may construct a residual coding syntax with residual information, encode it, and output it in the form of a bitstream, and the decoding device decodes the residual coding syntax from the bitstream to obtain residual (quantized) transform coefficients. Can be derived. As will be described later, the residual coding syntax is whether transform is applied to the block, where the position of the last effective transform coefficient in the block is, whether there is an effective transform coefficient in the subblock, what is the size/code of the effective transform coefficient, etc. It may include syntax elements representing.

S For example, the (quantized) transformation coefficients syntax elements such as the last_sig_coeff_x_prefix, last_sig_coeff_y_prefix, last_sig_coeff_x_suffix, last_sig_coeff_y_suffix, coded_sub_block_flag, sig_coeff_flag, par_level_flag, abs_level_gt1_flag, abs_level_gt3_flag, abs_remainder, coeff_sign_flag, dec_abs_level, mts_idx included in the residual information (syntax elements ) Can be encoded and/or decoded. This may be referred to as residual (data) coding or (transform) coefficient coding. In this case, the conversion/quantization process may be omitted. In this case, values of residual samples may be coded and signaled according to a predetermined method. Syntax elements related to residual data encoding/decoding can be represented as shown in Table 1 below.

Referring to Table 1, last_sig_coeff_x_prefix, last_sig_coeff_y_prefix, last_sig_coeff_x_suffix, and last_sig_coeff_y_suffix are syntax elements encoding (x, y) location information of the last non-zero coefficient in an associated block. The associated block may be a coding block (CB) or a transform block (TB). Regarding the transform (and quantization) and residual coding procedure, CB and TB may be used interchangeably. For example, it is as described above that residual samples are derived for CB, and (quantized) transform coefficients can be derived through transform and quantization of the residual samples, and through the residual coding procedure ( Information (or syntax elements) efficiently representing the quantized) transform coefficients (position, size, sign, etc.) can be generated and signaled. Quantized transform coefficients can simply be called transform coefficients. In general, when the CB is not larger than the maximum TB, the size of the CB may be the same as the size of the TB. In this case, the target block to be transformed (and quantized) and residual coded may be referred to as CB, and may be referred to as TB. Alternatively, when CB is greater than the maximum TB, the target block to be transformed (and quantized) and residual coded may be referred to as TB. Hereinafter, it is described that the syntax elements related to residual coding are signaled in units of a transform block (TB), but this is an example, as described above, that TB can be mixed with a coding block (CB).

Specifically, last_sig_coeff_x_prefix represents the prefix of the column position of the last significant coefficient in the scanning order in the transformation block, and last_sig_coeff_y_prefix represents the scanning order in the transformation block (scanning order). The prefix of the row position of the last significant coefficient in order may be indicated. last_sig_coeff_x_suffix represents the suffix of the column position of the last significant coefficient in the scanning order in the transform block, and last_sig_coeff_y_suffix is the scanning order in the transform block The suffix of the row position of the last significant coefficient in may be represented. Here, the effective coefficient may represent a non-zero coefficient. The scan order may be an upward-right diagonal scan order. Alternatively, the scan order may be a horizontal scan order or a vertical scan order. The scan order may be determined based on whether intra/inter prediction is applied to a target block (CB or CB including TB) and/or a specific intra/inter prediction mode.

Next, after dividing the transform block into 4x4 sub-blocks, a 1-bit syntax element coded_sub_block_flag is used for each 4x4 sub-block to indicate whether a non-zero coefficient exists in the current sub-block. The sub-block may be used interchangeably with a coefficient group (CG). Alternatively, when the width or height of a certain block is less than 4, a 1-bit syntax element coded_sub_block_flag is used for each 2x2 subblock to indicate whether a non-zero coefficient exists in the current subblock.

For example, if coded_sub_block_flag is 0, since there is no more information to be transmitted, the encoding process for the current subblock can be terminated. Conversely, if the value of coded_sub_block_flag is 1, the sig_coeff_flag encoding process may be continuously performed. Coded_sub_block_flag coding is unnecessary for the last sub-block containing a non-zero coefficient, and the sub-block containing the DC information of the transform block has a high probability of containing a non-zero coefficient. This can be assumed.

If coded_sub_block_flag indicates that a non-zero coefficient exists in the current sub-block, sig_coeff_flag having a binary value may be encoded according to the reverse scan order. A 1-bit syntax element sig_coeff_flag may be encoded for each coefficient according to the scan order. If the value of the coefficient at the current scan position is not 0, the sig_coeff_flag value may be 1. Here, in the case of a subblock including the last non-zero coefficient, since sig_coeff_flag does not need to be encoded for the last non-zero coefficient, the encoding process may be omitted. Level information encoding can be performed only when sig_coeff_flag is 1, and four syntax elements can be used in the level information encoding process. Specifically, each sig_coeff_flag[xC][yC] may indicate whether the level (value) of the corresponding transform coefficient at each transform coefficient position (xC, yC) in the current TB is non-zero (non-zero). In an embodiment, sig_coeff_flag may correspond to an example of a syntax element of a significant coefficient flag indicating whether a quantized transform coefficient is a non-zero effective coefficient.

The remaining level value remAbsLevel for sig_coeff_flag after encoding may be derived as shown in Equation 1 below. Here, coeff means an actual transform coefficient value.

abs_level_gt1_flag may indicate whether remAbsLevel at the corresponding scanning position n is greater than 1. At this time, if the value of abs_level_gt1_flag is 0, the absolute value of the coefficient at the corresponding position is 1. If the value of abs_level_gt1_flag is 1, it indicates that the level value remAbsLevel to be encoded is remaining, and thus the level value remAbsLevel to be encoded can be derived as in Equation 2 below.

The LSB (least significant coefficient) value of remAbsLevel described in Equation 2 may be encoded using par_level_flag. par_level_flag[n] may represent parity of the transform coefficient level (value) at the scanning position n. That is, par_level_flag can be derived as in Equation 3 below.

After encoding par_leve_flag, the level value remAbsLevel to be encoded may be updated as shown in Equation 4 below.

abs_level_gt3_flag may indicate whether remAbsLevel at the corresponding scanning position n is greater than 3. At this time, encoding for abs_remainder may be performed only when abs_level_gt3_flag is 1. If the relationship between the actual transform coefficient value coeff and each syntax element is summarized, it may be as shown in Equation 5 below.

In addition, Table 2 below shows the relationship between the actual transform coefficient value coeff and each syntax element as an example.

Here, |coeff| represents the transform coefficient level (value), and may be expressed as AbsLevel for the transform coefficient.

Finally, the sign of each coefficient can be encoded using a 1-bit symbol coeff_sign_flag. coeff_sign_flag may represent the sign of the transform coefficient level at the corresponding scanning position n.

On the other hand, CABAC provides high performance, but has a disadvantage of poor throughput performance. This is due to CABAC's regular encoding engine, and regular encoding (that is, encoding through CABAC's regular encoding engine) shows high data dependence because it uses the updated probability state and range through encoding of the previous bin. It can take a lot of time to read the probability interval and determine the current state. This can solve the CABAC throughput problem by limiting the number of context-coded bins.

For example, as shown in Table 1 above, the sum of bins used to express sig_coeff_flag, abs_level_gt1_flag, par_level_flag, abs_level_gt3_flag may be limited according to the size of the sub-block.For example, in the case of a 4x4 sub-block, 32 and a 2x2 sub-block May be limited to 8. In this case, when all limited context encoding bins are used to encode the syntax element, the remaining coefficients may be binarized without using CABAC to perform bypass encoding. In other words, when the number of encoded context encoding bins becomes 32 in a 4x4 coefficient group (ie, sub-block) and 8 in 2x2 CG, sig_coeff_flag, abs_level_gt1_flag, par_level_flag, abs_level_gt3_flag are no longer encoded as context encoding bins, The transform coefficient level (value) |coeff| can be directly encoded using dec_abs_level. The transform coefficient level (value) |coeff| may be derived as in Equation 6 below, and may be directly encoded as dec_abs_level as shown in Table 3 below.

Here, dec_abs_level may represent an intermediate value coded with a Golomb-Rice code at a corresponding scanning position n. The dec_abs_level may be signaled for a scanning position that satisfies the conditions disclosed in Table 1 above, and in this case, the absolute value AbsLevel (i.e. | coeff |) of the corresponding transform coefficient is 0, dec_abs_level+1, dec_abs+ depending on the condition. It can be derived as one of the level values. Alternatively, the sum of bins used to represent sig_coeff_flag, abs_level_gt1_flag, par_level_flag, and abs_level_gt3_flag may be limited according to the size of the TU including the target CG to be coded. In this case, it may be set to a value corresponding to 1.75 times the area of the TU.

The transform coefficients in the 4x4 block shown in FIG. 11 may represent quantized coefficients. In addition, the block shown in FIG. 11 may be a 4x4 transform block or a 4x4 sub-block in an 8x8, 16x16, 32x32, or 64x64 transform block. The 4x4 block of FIG. 11 may represent a luma block or a chroma block.

As an embodiment, a result of encoding by performing an inverse diagonal scan on the coefficients in the block shown in FIG. 11 may be derived as shown in Table 4 below.

In Table 4, scan_pos denotes a position of a coefficient according to an inverse diagonal scan. scan_pos 15 may be the transform coefficient of the first scan, that is, the lower right corner, in the 4x4 block, and scan_pos 0 may be the transform coefficient of the last scan, that is, the upper left corner. Alternatively, scan_pos may be referred to as a scan position. For example, scan_pos 0 may be referred to as scan position 0.

Meanwhile, by expressing the correlation between the residual signals in the transform domain, data is compressed and the compressed data is transmitted to the decoding apparatus. However, if the correlation between the residual signals is insufficient, data compaction may not sufficiently occur. In this case, a conversion process including a complicated calculation process may be omitted, and a residual signal in the pixel domain (spatial domain) may be transmitted to the decoding apparatus. Since the residual signal of the pixel domain to which the transformation is not applied has different characteristics (e.g., the distribution of residual signals, the absolute level of each residual signal, etc.) from the residual signal of the general transformation domain. A residual signal encoding/decoding method for efficiently transmitting a signal to a decoder is proposed. According to the proposed method, coding efficiency can be improved by efficiently transmitting the residual signal expressed in the pixel domain.

In particular, in the case of a residual signal in a pixel domain to which the transformation is not applied, there is a high possibility that a sign between the residual signals is concentrated to one side. Here, the sign may mean + (plus) or-(minus). In addition, the residual signal in the pixel domain to which the transform is not applied may mean coefficients to which the transform is not applied, and a block including the coefficients to which the transform is not applied may be referred to as a transform skip block. Also, the residual signal may include transform coefficients derived by encoding/decoding in the form of residual information, and may be used interchangeably with terms such as transform coefficient and residual coefficient in this document.

Specifically, if the boundary between the objects of the image in the block is very clear, but the amount of change within the object is small or simple, the image quality around the boundary of the object may be greatly degraded when the transformation is applied. I can. In addition, pixels belonging to the same object in the transform-skipped block may have similar levels and codes within the object without significant deviation. Accordingly, the number of bits can be saved by effectively coding the code of the residual signal for the transform skip block having such a characteristic. Therefore, this document proposes a method of first transmitting whether the code is the same for all residual signals for the transform skip block, and then saving the code to be transmitted for each residual coefficient. In other words, this document proposes a method for saving the amount of bits by transmitting code information indicating whether all transform coefficients in the current block have the same code instead of code information to be transmitted for each transform coefficient in the current block. Here, the current block may be a coding block (CB) or a transform block (TB).

As described in Table 1 above, after the significance flag, greater than one flag, parity flag, and greater than three flag are coded for residual coding (encoding/decoding), the residual level value abs_remainder or dec_abs_level may be coded. Then, a code for each residual may be coded. At this time, since codes are coded only for non-zero residual coefficients, it may be more advantageous to perform the coding method proposed in this document when the number of non-zero residual coefficients to which code information is coded is more than a certain number. .

In an embodiment, the number of non-zero residual coefficients may be determined, and accordingly, code information may be coded by determining whether the codes of the non-zero residual coefficients are the same. In this case, the number of non-zero residual coefficients may be a specific value, for example, may be one of 0 to 16. Also, the specific value may be referred to as a threshold. Here, the non-zero residual coefficients may refer to transform coefficients derived by a significance flag, greater than one flag, parity flag, greater than three flag, abs_remainder or dec_abs_level.

As an example, if the TU is divided into 4x4 units of CG (Coefficient group; i.e., sub-block), and the number of non-zero residual coefficients in the CG is set to a threshold value of 5, the non-zero residual in the currently encoded CG in the TU If the number of dual coefficients is 4 or less, encoding of code information is performed according to the conventional method, and if the number of non-zero residual coefficients in the currently encoded CG in the TU is 5 or more, the codes of all residual coefficients in the currently encoded CG It is possible to determine whether or not to be the same, to encode code information for all residual coefficients, and signal this.

In another embodiment, code information may be coded by determining the number of non-zero residual coefficients according to the size of the current block, and determining whether signs of non-zero residual coefficients are the same accordingly. That is, a threshold value may be set based on the size of the current block, and if the number of non-zero residual coefficients in the currently encoded CG is less than the threshold value, encoding of the code information is performed according to the existing method, and If the number of non-zero residual coefficients in the CG is greater than or equal to a threshold value, it is possible to determine whether the codes of all residual coefficients in the currently encoded CG are the same, encode the code information for all residual coefficients, and signal this. Here, the number of non-zero residual coefficients used as the threshold value may be one of a number from 0 to the total number of samples in the current block, or 0 to 16, which is the range of the number of residual coefficients controlled in each CG unit. It can be one of the numbers up to.

For example, when the size of the current block is 8x8, the threshold value may be derived as 5. In this case, if the number of non-zero residual coefficients in the currently encoded CG in the current block of 8x8 size is 4 or less, encoding of the code information is performed according to the conventional method, and 0 in the CG currently encoded in the current block of 8x8 size. If the number of residual coefficients other than these is 5 or more, it is possible to determine whether the codes of all residual coefficients in the currently encoded CG are the same, encode the code information for all residual coefficients, and signal this.

Alternatively, as an example, when the size of the current block is 4x4, the threshold value may be derived as 4. In this case, if the number of non-zero residual coefficients in the currently encoded CG in the current block of 4x4 size is 3 or less, encoding information is performed according to the conventional method, and 0 in the CG currently encoded in the current block of 4x4 size If the number of residual coefficients other than this is 4 or more, it is possible to determine whether the codes of all residual coefficients in the currently encoded CG are the same, to encode code information for all residual coefficients, and signal this.

In another embodiment, code information is coded by determining the number of non-zero residual coefficients based on the size of the current block and the location of the CG, and determining whether the codes of non-zero residual coefficients are the same accordingly. can do. That is, a threshold value may be set based on the size of the current block and the position of the CG, and if the number of non-zero residual coefficients in the currently encoded CG is less than the threshold value, encoding of the code information is performed according to the conventional method. If the number of non-zero residual coefficients in the currently encoded CG is greater than or equal to the threshold value, it is determined whether the codes of all residual coefficients in the currently encoded CG are the same, encoding the code information for all residual coefficients, and signaling this. I can. Here, the number of non-zero residual coefficients used as the threshold value may be one of a number from 0 to the total number of samples in the current block, or 0 to 16, which is the range of the number of residual coefficients controlled in each CG unit. It can be one of the numbers up to.

For example, if the size of the current block is 8x8 and the position of the currently encoded CG in the current block is the 3rd CG that is first encoded by a diagonal scan order, the threshold value may be derived as 5. . In this case, if the number of non-zero residual coefficients in the currently encoded CG in the current block is 4 or less, encoding of the code information is performed according to the conventional method, and non-zero residual coefficients in the currently encoded CG in the current block If the number is 5 or more, it is possible to determine whether the codes of all residual coefficients in the currently encoded CG are the same, to encode the code information for all residual coefficients, and signal this. Here, the diagonal scan order may represent a scan order proceeding from the upper right to the lower left and from the lower right to the upper left. Also, CG 3 may indicate the CG on the lower right of the current block.

Or, as an example, if the size of the current block is 8x8 and the position of the currently encoded CG in the current block is the 0th CG (ie, the lower left CG of the current block) at the upper left position of the current block, the threshold is It can be derived as 7. In this case, if the number of non-zero residual coefficients in the currently encoded CG in the current block is 6 or less, encoding of the code information is performed according to the conventional method, and non-zero residual coefficients in the currently encoded CG in the current block If the number is 7 or more, it is possible to determine whether the codes of all residual coefficients in the currently encoded CG are the same, to encode the code information for all residual coefficients, and signal this.

In another embodiment, the number of non-zero residual coefficients is determined based on the size of the current block, the location of the CG, and the prediction mode, and accordingly, it is determined whether or not the codes of the non-zero residual coefficients are the same. Information can be coded. That is, a threshold value may be set based on the size of the current block, the location of the CG, and the prediction mode, and if the number of non-zero residual coefficients in the currently encoded CG is less than the threshold value, encoding of the code information according to the existing method And, if the number of non-zero residual coefficients in the currently encoded CG is greater than or equal to the threshold value, it is determined whether the codes of all residual coefficients in the currently encoded CG are the same to encode code information for all residual coefficients. You can signal this. Here, the number of non-zero residual coefficients used as the threshold value may be one of a number from 0 to the total number of samples in the current block, or 0 to 16, which is the range of the number of residual coefficients controlled in each CG unit. It can be one of the numbers up to.

As an example, the size of the current block is 8x8, the position of the currently encoded CG in the current block is the 3rd CG that is first encoded according to a diagonal scan order, and the current block is a block predicted in intra prediction mode. In the case of, the code information for all residual coefficients is encoded by determining whether the codes of all residual coefficients in the currently encoded CG are the same regardless of the number of non-zero residual coefficients in the currently encoded CG in the current block. You can signal this.

Or, as an example, the size of the current block is 8x8, the position of the currently encoded CG in the current block is the 0th CG that is last encoded by diagonal scan order, and the current block is predicted in intra prediction mode. In the case of a blocked block, the threshold value can be derived as 5. In this case, if the number of non-zero residual coefficients in the currently encoded CG in the current block is 4 or less, encoding of the code information is performed according to the conventional method, and non-zero residual coefficients in the currently encoded CG in the current block If the number is 5 or more, it is possible to determine whether the codes of all residual coefficients in the currently encoded CG are the same, to encode the code information for all residual coefficients, and signal this.

Or, as an example, the size of the current block is 8x8, the position of the currently encoded CG in the current block is the 3rd CG that is first encoded by diagonal scan order, and the current block is predicted in the inter prediction mode. In the case of a blocked block, the threshold value can be derived as 3. In this case, if the number of non-zero residual coefficients in the currently encoded CG in the current block is 2 or less, encoding of the code information is performed according to the conventional method, and non-zero residual coefficients in the currently encoded CG in the current block If the number is 3 or more, it is possible to determine whether the codes of all residual coefficients in the currently encoded CG are the same, encode the code information for all residual coefficients, and signal this.

Or, as an example, the size of the current block is 8x8, the position of the currently encoded CG in the current block is the 0th CG that is last encoded by diagonal scan order, and the current block is predicted in the inter prediction mode. In the case of a blocked block, the threshold value can be derived as 5. In this case, if the number of non-zero residual coefficients in the currently encoded CG in the current block is 4 or less, encoding of the code information is performed according to the conventional method, and non-zero residual coefficients in the currently encoded CG in the current block If the number is 5 or more, it is possible to determine whether the codes of all residual coefficients in the currently encoded CG are the same, to encode the code information for all residual coefficients, and signal this.

As described above, in this document, a method for effectively coding a residual signal code based on the number of non-zero residual coefficients is proposed. Hereinafter, in coding residual information (e.g., significance flag, greater than one flag, parity flag, greater than three flag, abs_remainder, or dec_abs_level) for the transform skip block, a residual signal based on the number of context-coded bins We propose a method of effectively coding the code of

In performing CABAC-based entropy coding, it is possible to limit the number of context-coded bins in terms of throughput. That is, coding speed and performance can be improved by limiting the number of context-coded bins to a specific number. Therefore, in this document, based on the number of context-coded bins for syntax elements included in the residual information, it is determined whether to transmit code information indicating whether all transform coefficients in the current block have the same code, and code it. Suggest a way to do it.

In one embodiment, the number of context-coded bins may be limited to a specific number in units of CG in the current block, and when context coding code information indicating whether all transform coefficients in the current block have the same code, the code The information may be affected by context coded bins for other syntax elements included in the previously coded residual information. As an example, the number of context coded bins may be limited to 32 for each CG in the current block. In this case, if the number of context-coded bins by other syntax elements included in the residual information is filled with 32 before coding the code information, the proposed code information may not be encoded. By limiting the number of context-coded bins as described above, coding speed can be improved and efficiency can be obtained in terms of performance.

Table 5 below shows whether to transmit code information indicating whether all transform coefficients in the current block have the same code based on the number of context-coded bins, and a method of coding the code information as syntax elements. Table 6 below shows semantics that define information represented by the syntax elements of Table 5. In particular, it shows the semantics for a syntax element representing the code information (that is, code information indicating whether all transform coefficients in the current block have the same code) proposed in this document.

Referring to Tables 5 and 6, one_sign_flag may be a syntax element indicating whether signs of residual level signals (ie, non-zero transform coefficients) are all the same in subblocks within the current block. Here, non-zero transform coefficients may refer to the aforementioned non-zero residual coefficients. For example, if the value of one_sign_flag is 0, it indicates that non-zero transform coefficients in the sub-block have different signs, and if the value of one_sign_flag is 1, all non-zero transform coefficients in the sub-block have the same sign. Can indicate that

The common_sign_flag may be a syntax element indicating whether the same sign is + (plus) or-(minus) when all the signs of the residual level signals (ie, non-zero transform coefficients) in a subblock in the current block are the same. For example, if the value of common_sign_flag is 0, it indicates that all non-zero transform coefficients in the subblock in the current block have a + (plus) sign, and if the value of common_sign_flag is 1, it is a non-zero transform coefficient in the subblock in the current block. Can indicate that they all have a-(minus) sign. Or it can be reversed.

As an embodiment, as shown in Table 5, the number of context-coded bins may be set to remBinsPass1 and limited. For example, remBinsPass1 may be set to a specific value based on the size of the sub-block, remBinsPass1 may be set to 32 in case of 4x4 sub-block, and remBinsPass1 may be set to 8 in case of 2x2 sub-block. When the number of context-coded bins (eg, remBinsPass1) is set to a specific number (eg, 32), syntax elements sig_coeff_flag, abs_level_gt1_flag, par_level_flag and/or in deriving non-zero transform coefficients for subblocks in the current block abs_level_gt3_flag may be coded based on context. At this time, as the binarized bins for the syntax elements sig_coeff_flag, abs_level_gt1_flag, par_level_flag, and/or abs_level_gt3_flag are coded based on the context model, the one_sign_flag syntax element when the number of context-coded bins reaches a specific number (for example, 32). May not be parsed. Otherwise, when the number of context-coded bins by the syntax elements sig_coeff_flag, abs_level_gt1_flag, par_level_flag and/or abs_level_gt3_flag does not fill a specific number (e.g., 32) (when remBinsPass1> 0 conditions shown in Table 5 are satisfied), A parsing process (context-based coding) may be performed on the one_sign_flag syntax element.

If it is determined that all the transform coefficients have the same sign based on a flag indicating whether the sign of all the transform coefficients is the same (for example, one_sign_flag) according to the embodiments proposed in this document described above, the encoding device Information (eg, common_sign_flag) on which code is a code of the transform coefficient may be transmitted, and further code related information may not be encoded. Here, information on what code is, that is, a syntax element of information indicating signs of all transform coefficients may be the above-described common_sign_flag. In addition, when it is determined that all the transform coefficients do not have the same code, the encoding apparatus may encode the codes for all the transform coefficients through the same or similar method as the method described in Table 1 above.

In addition, the above-described embodiments can be applied when the current block is a transform skip block, that is, when no transform is applied to a residual signal for the current block. For example, whether transformation is applied to the residual signal for the current block may be indicated by transformation skip flag information. For example, when the value of the transform skip flag for the current block is 0 (when transform is applied to the residual signal for the current block), the encoding of sign information may be performed according to a conventional method. Alternatively, if the value of the transform skip flag for the current block is 1 (if transform is not applied to the residual signal for the current block), the sign of all transform coefficients of the sub-blocks in the current block ( A flag indicating whether sign) is the same (one_sign_flag) may be transmitted.

12 schematically shows a sign code encoder in an encoding device that encodes sign information (eg, original sign flag information), and FIG. 13 is a sign code decoder in a decoding device that decodes sign information (eg, original sign flag information) Schematically shown. 14 illustrates an example of a method of encoding/decoding sign information (eg, original sign flag information) performed by a sign code encoder in the encoding device of FIG. 12 and/or a sign code decoder in the decoding device of FIG. 13 Schematically shown.

12 to 14, the encoding device/decoding device may determine whether the number of non-zero transform coefficients is greater than a threshold (S1400).

The threshold value may mean a specific value in the above-described embodiments. For example, the threshold value may be one of 0 to the total number of samples of the current block, or may be one of 0 to 16, which is a range of the number of transform coefficients controlled in each CG (sub-block) unit. Alternatively, as in the above-described embodiments, the threshold value may be derived based on at least one of a size of a current block, a position of a subblock in the current block, or a prediction mode of the current block.

In one embodiment, the encoding device/decoding device is based on at least one of a size of a current block, a position of a subblock in the current block, or a prediction mode of the current block in which the number of non-zero transform coefficients for a subblock in the current block is It can be determined whether it is greater than the threshold value determined by.

When the number of non-zero transform coefficients for sub-blocks in the current block is greater than the threshold value, the encoding device/decoding device is a circle sign indicating whether the signs of all non-zero transform coefficients for sub-blocks in the current block are the same. Flag information can be coded (S1410). Here, the one sign flag information may be the above-described one_sign_flag syntax element.

In coding the one sign flag information, the encoding device may determine a value of the one sign flag information and encode the determined value according to whether signs of non-zero transform coefficients for a subblock in the current block are all the same. . For example, if the signs of non-zero transform coefficients are all the same, the one sign flag information value may be determined to be 1 and encoded. Otherwise, the one sign flag information value may be determined to be 0 and encoded. When the number of non-zero transform coefficients in the sub-block is greater than a threshold value, the decoding apparatus may acquire the original sign flag information and decode it.

The encoding device/decoding device may determine whether the value of the original sign flag information is 1 (S1420). When the value of the original sign flag information is 1, the encoding device/decoding device may code information indicating a sign for all non-zero transform coefficients in the sub-block (S1430). This information may be the above-described common_sign_flag syntax element.

In coding common_sign_flag information, if the sign of all non-zero transform coefficients in a sub-block is + (plus), the encoding device may determine and encode the value of common_sign_flag information as 0, and a non-zero transform in the sub-block If the sign of all the coefficients is-(minus), the value of the common_sign_flag information may be determined as 1 and encoded. When the value of the original sign flag information is 1, the decoding device can decode the common_sign_flag syntax element. In this case, if the value of common_sign_flag is 0, the decoding device determines that the signs of all non-zero transform coefficients in the subblock are + (plus). , If the value of common_sign_flag is 1, it may be determined that the signs of all non-zero transform coefficients in the sub-block are-(minus).

When the number of non-zero transform coefficients for sub-blocks in the current block is less than or equal to the threshold value, or when the value of the one sign flag information is not 1, the encoding device/decoding device is used for each of the non-zero transform coefficients in the sub-block. Sign information can be coded (S1440).

As described above, the encoding apparatus (sine code encoder) disclosed in FIG. 12 may encode sign-related information on non-zero transform coefficients based on the residual signal and a transform skip flag (transform_skip_flag). The decoding apparatus (sine code decoder) disclosed in FIG. 13 may decode sine related information for non-zero transform coefficients based on the decoded residual signal and a transform skip flag (transform_skip_flag).

The method disclosed in FIG. 15 may be performed by the encoding apparatus 200 disclosed in FIG. 2. Specifically, step S1500 of FIG. 15 may be performed by the residual processing unit 230 (more specifically, the conversion unit 232) disclosed in FIG. 2, and steps S1510 to S1520 of FIG. 15 are entropy encoding disclosed in FIG. 2. It can be performed by the unit 240. In addition, the method disclosed in FIG. 15 may include the embodiments described above in this document. Accordingly, in FIG. 15, detailed descriptions of content overlapping with the above-described embodiments will be omitted or simplified.

Referring to FIG. 15, the encoding apparatus may derive non-zero transform coefficients for the current block (S1500).

In an embodiment, the encoding apparatus may determine whether to perform inter prediction or intra prediction on the current block, and may determine a specific inter prediction mode or a specific intra prediction mode based on RD cost. According to the determined mode, the encoding apparatus may derive prediction samples for the current block. In addition, the encoding apparatus may derive residual samples by comparing the original samples and the prediction samples for the current block.

Thereafter, the encoding apparatus may derive transform coefficients through a transform procedure for residual samples and quantize the derived transform coefficients to derive quantized transform coefficients. In this case, the encoding device may determine whether or not transformation is applied to the residual samples. When no transformation is applied to the residual samples, the encoding apparatus may derive the residual samples as non-zero transform coefficients. Alternatively, when transform is applied to residual samples, the encoding apparatus may derive transform coefficients by performing transform on the residual samples. As an example, the encoding device may generate and encode transformation skip flag information based on whether transformation is applied to the current block. Transform skip flag information may be represented by a transform_skip_flag syntax element.For example, if the value of transform_skip_flag is 0, it may indicate that transform is applied to the current block, and if the value of transform_skip_flag is 1, the transform is applied to the current block. It can indicate something that doesn't work.

That is, the encoding apparatus may derive non-zero transform coefficients through a transform and/or quantization process for residual samples of the current block. In this case, non-zero transform coefficients may be derived in units of sub-blocks within the current block. For example, a subblock in the current block may have a size of 4x4, and a subblock having a size of 4x4 may include 0 to 16 non-zero transform coefficients. In addition, a non-zero transform coefficient used in this document may be referred to interchangeably with terms such as an effective transform coefficient, a residual coefficient, a residual signal, a coefficient, and a quantized transform coefficient for convenience of description. Also, the sub-block may be referred to as a coefficient group (CG).

The encoding apparatus may generate residual information for non-zero transform coefficients (S1510).

In an embodiment, when quantization is applied to non-zero transform coefficients, the encoding apparatus may quantize non-zero transform coefficients and generate residual information for quantized non-zero transform coefficients. can do. Alternatively, when quantization is not applied to non-zero transform coefficients, the encoding apparatus may generate residual information for non-zero transform coefficients.

Here, the residual information may include information efficiently indicating the position, size, code, etc. of non-zero transform coefficients. For example, the residual information is syntax elements indicating where the position of the last effective transform coefficient in the sub-block is, whether there is an effective transform coefficient in the sub-block, and the size/sign of the effective transform coefficient. It may include. Syntax elements representing residual information may include, as described above, last_sig_coeff_x_prefix, last_sig_coeff_y_prefix, last_sig_coeff_x_suffix, last_sig_coeff_y_suffix, coded_sub_block_flag, sig_coeff_flag, sig_coeff_flag, ab_flag_flag, abs_flag_flag, abs_flag_flag3, as described above.

The encoding device may encode image information including residual information (S1520).

In an embodiment, the encoding device may perform context model-based entropy encoding on syntax elements included in the residual information. For example, the encoding apparatus may perform encoding based on a context model on at least one of syntax elements sig_coeff_flag, par_level_flag, abs_level_gt1_flag, and abs_level_gt3_flag included in the residual information, and derive context-coded bins. Alternatively, the encoding apparatus may perform bypass coding-based entropy encoding on syntax elements included in the residual information. For example, the encoding apparatus may perform bypass encoding on at least one of the syntax elements abs_remainder and dec_abs_level included in the residual information, and derive bypass bins.

Depending on the embodiment, the encoding device may encode image information by including one sign flag information.

Specifically, the encoding device determines whether to generate one sign flag information for a sub-block in the current block, and image information including one sign flag information based on sign information for non-zero transform coefficients. Can be encoded. Here, the one sign flag information may indicate a syntax element indicating whether signs of non-zero transform coefficients for a subblock in the current block are all the same. For example, the one sign flag information may be the above-described one_sign_flag syntax element.

In an embodiment, the encoding apparatus may determine whether to generate one sign flag information for a subblock in a current block based on the number of context-coded bins for syntax elements included in the residual information. Here, the number of context-coded bins may represent the number of context-coded bins for sub-blocks in the current block.

For example, before generating the original sign flag information, the encoding device may not generate the one sign flag information when the number of context-coded bins for the sub-block in the current block reaches a specific number. In this case, the sign information of each of the transform coefficients for the sub-block in the current block may be generated and encoded according to a conventional method. Alternatively, if the number of context-coded bins for sub-blocks in the current block does not reach a specific number before generating the one sign flag information, the encoding device may generate and encode the one sign flag information. In this case, the encoding apparatus may generate the original sign flag information by determining whether all the signs of the transform coefficients for the subblocks in the current block are the same. And, according to the value of the one sign flag information (e.g., when the value of the one sign flag information is 1), information indicating whether the sign of all the transform coefficients for the sub-block in the current block is positive or negative (for example, common_sign_flag) is provided. It can be created and encoded.

Syntax elements that are context coded before generating the original sign flag information may include, for example, sig_coeff_flag, par_level_flag, abs_level_gt1_flag, and abs_level_gt3_flag, and context-coded bins may be derived as a result of context-based coding on these syntax elements. have. At this time, it is possible to determine whether the number of the derived context-coded bins has reached a specific limited number, and to generate original sign flag information and determine whether to context-encode.

As described above, the number of context-coded bins may be limited to a specific number, and may be determined, for example, to a specific number based on the size of sub-blocks. For example, in the case of a 4x4 subblock, the number of context coded bins may be set to 32, and in the case of a 2x2 subblock, the number of context coded bins may be set to eight.

Alternatively, in another embodiment, the encoding apparatus may determine whether to generate one sign flag information for a subblock in the current block based on the number of non-zero transform coefficients. Here, the number of non-zero transform coefficients may be set as a threshold value. For example, the threshold value may be one of 0 to the number of samples of the current block (eg, one of 0 to 64), or may be one of 0 to the number of samples of the sub-block (eg, one of 0 to 16). . Alternatively, the threshold value may be derived based on at least one of the size of the current block, the position of the sub-block in the current block, and the prediction mode of the current block.

For example, when the size of the current block is 8x8, the threshold value may be derived as 5. Alternatively, when the size of the current block is 4x4, the threshold value may be derived as 4.

As another example, when the size of the current block is 8x8 and the subblock is the lower right subblock of the current block, the threshold value may be derived as 5. Alternatively, if the size of the current block is 8x8 and the subblock is the upper left subblock of the current block, the threshold value may be derived as 7.

As another example, when the size of the current block is 8x8, the subblock is a lower-right subblock of the current block, and the prediction mode of the current block is the intra prediction mode, the threshold value may be derived as 0. Alternatively, when the size of the current block is 8x8, the subblock is the upper left subblock of the current block, and the prediction mode of the current block is the intra prediction mode, the threshold value may be derived as 5.

As another example, when the size of the current block is 8x8, the subblock is the lower right subblock of the current block, and the prediction mode of the current block is the inter prediction mode, the threshold value may be derived as 3. Alternatively, when the size of the current block is 8x8, the subblock is the upper left subblock of the current block, and the prediction mode of the current block is the inter prediction mode, the threshold value may be derived as 5.

That is, the encoding apparatus may determine whether to generate one sign flag information for a sub-block in the current block, based on whether the number of non-zero transform coefficients is greater than or equal to the threshold value derived as described above. For example, when the number of non-zero transform coefficients is greater than or equal to a threshold value, the encoding device may generate and encode one-sine flag information for non-zero transform coefficients in a corresponding sub-block. In this case, the encoding apparatus may determine whether all the signs of non-zero transform coefficients in the corresponding sub-block are the same, and generate original sign flag information. And, according to the value of the one sign flag information (e.g., when the value of the one sign flag information is 1), information indicating whether the sign of all the transform coefficients for the sub-block in the current block is positive or negative (for example, common_sign_flag) is provided. It can be created and encoded. Alternatively, when the number of non-zero transform coefficients is less than the threshold value, the encoding device may not generate one-sign flag information for non-zero transform coefficients in the corresponding sub-block. In this case, the encoding apparatus may generate and encode the sign information of each of the transform coefficients for the sub-block in the current block according to a conventional method.

In addition, the encoding apparatus may determine whether to generate one sign flag information for a sub-block in the current block, based on transformation skip flag information indicating whether transformation is applied to the current block. For example, if the transform is not applied to the current block (ie, if the value of the transform skip flag information is 1), the encoding device may generate and encode the one sign flag information.

When the one sign flag information is generated as described above, the encoding apparatus may generate and encode image information including the one sign flag information and residual information, and may output the encoded image information as a bitstream.

In addition, the image information may further include prediction information on the current block based on a result of performing prediction on the current block. For example, the prediction information may include information on an inter prediction mode or an intra prediction mode performed on the current block. The encoding device may generate and encode prediction information for the current block.

The bitstream may be transmitted to a decoding device through a network or a (digital) storage medium. Here, the network may include a broadcasting network and/or a communication network, and the digital storage medium may include various storage media such as USB, SD, CD, DVD, Blu-ray, HDD, and SSD.

The process of generating the prediction samples for the current block described above may be performed by the prediction unit 220 of the encoding apparatus 200 disclosed in FIG. 2, and the process of deriving the residual samples is the encoding apparatus ( It may be performed by the subtraction unit 231 of 200).

The method disclosed in FIG. 16 may be performed by the decoding apparatus 300 disclosed in FIG. 3. Specifically, steps S1600 to S1610 of FIG. 16 may be performed by the entropy decoding unit 310 disclosed in FIG. 3, and step S1620 of FIG. 16 is the residual processing unit 320 disclosed in FIG. 3 (more specifically, inverse quantization It may be performed by the unit 321 and the inverse transform unit 321, and step S1630 of FIG. 16 may be performed by the adder 340 disclosed in FIG. 3. In addition, the method disclosed in FIG. 16 may include the embodiments described above in this document. Accordingly, in FIG. 16, detailed descriptions of contents overlapping with the above-described embodiments will be omitted or simplified.

Referring to FIG. 16, the decoding apparatus may obtain residual information for a current block (S1600). That is, the decoding apparatus may receive image information including residual information for the current block from the bitstream.

In an embodiment, the decoding apparatus may perform context model-based entropy decoding on syntax elements included in the residual information. For example, the decoding apparatus may perform decoding based on a context model on at least one of syntax elements sig_coeff_flag, par_level_flag, abs_level_gt1_flag, and abs_level_gt3_flag included in the residual information, and derive context coded bins. Alternatively, the decoding apparatus may perform bypass coding-based entropy decoding on syntax elements included in the residual information. For example, the decoding apparatus may perform bypass decoding on at least one of the syntax elements abs_remainder and dec_abs_level included in the residual information, and may derive bypass bins.

The decoding apparatus may derive non-zero transform coefficients for the current block based on the residual information (S1610).

In an embodiment, the decoding apparatus may derive non-zero transform coefficients for sub-blocks in the current block by performing context decoding or bypass decoding on syntax elements included in the residual information as described above. The coding process for syntax elements included in the residual information and the process of deriving transform coefficients have been described in detail through Tables 1 to 6 and Equations 1 to 6.

In addition, according to an embodiment, the decoding apparatus may derive non-zero transform coefficients for the current block based on one sign flag information.

Specifically, the decoding apparatus may determine whether to parse the one sign flag information for the subblock in the current block, and derive the sign information for non-zero transform coefficients based on whether the one sign flag information is parsed. . Here, the one sign flag information may indicate a syntax element indicating whether signs of non-zero transform coefficients for a subblock in the current block are all the same. For example, the one sign flag information may be the above-described one_sign_flag syntax element.

In an embodiment, the decoding apparatus may determine whether to parse the original sign flag information for a subblock in the current block based on the number of context-coded bins for syntax elements included in the residual information. Here, the number of context-coded bins may represent the number of context-coded bins for sub-blocks in the current block.

For example, before parsing the original sign flag information, the decoding apparatus may not parse the original sign flag information when the number of context-coded bins for a subblock in the current block reaches a specific number. In this case, the sign information of each of the transform coefficients may be obtained by parsing the sign information of each of the transform coefficients for the sub-block in the current block according to a conventional method. Alternatively, if the number of context-coded bins for sub-blocks in the current block does not reach a specific number before parsing the original sign flag information, the decoding apparatus may parse the original sign flag information to obtain the value. . For example, if the value of the one sign flag information is 1, the decoding apparatus determines that all non-zero transform coefficients for the sub-blocks in the current block have the same sign, and the total transform coefficients for the sub-blocks in the current block It is possible to obtain and parse information indicating whether the sign of the people is positive or negative (for example, common_sign_flag). When the value of the original sign flag information is 0, the decoding apparatus may determine that non-zero transform coefficients for sub-blocks in the current block have different signs, and obtain sign information of each of the transform coefficients.

At this time, the syntax elements context-coded before parsing the original sign flag information may include, for example, sig_coeff_flag, par_level_flag, abs_level_gt1_flag, abs_level_gt3_flag, and context-coded beans are derived as a result of context-based coding on these syntax elements. Can be. At this time, it is possible to determine whether to parse the original sign flag information by determining whether the number of the derived context coded bins has reached a specific limited number.

Alternatively, as another embodiment, the decoding apparatus may determine whether to parse one sign flag information for a subblock in the current block based on the number of non-zero transform coefficients. Here, the number of non-zero transform coefficients may be set as a threshold value. For example, the threshold value may be one of 0 to the number of samples of the current block (eg, one of 0 to 64), or may be one of 0 to the number of samples of the sub-block (eg, one of 0 to 16). . Alternatively, the threshold value may be derived based on at least one of the size of the current block, the position of the sub-block in the current block, and the prediction mode of the current block.

That is, the decoding apparatus may determine whether to parse the one sign flag information for the sub-block in the current block, based on whether the number of non-zero transform coefficients is equal to or greater than the threshold value derived as described above. For example, when the number of non-zero transform coefficients is greater than or equal to a threshold value, the decoding apparatus may parse one-sine flag information for non-zero transform coefficients in a corresponding sub-block. At this time, if the value of the original sign flag information is 1, the decoding apparatus determines that all non-zero transform coefficients for sub-blocks in the current block have the same sign, and the signs of all transform coefficients for sub-blocks in the current block are Information indicating whether it is positive or negative (eg, common_sign_flag) can be obtained and parsed. When the value of the original sign flag information is 0, the decoding apparatus may determine that non-zero transform coefficients for sub-blocks in the current block have different signs, and obtain sign information of each of the transform coefficients. Alternatively, when the number of non-zero transform coefficients is less than the threshold value, the decoding apparatus may not parse the original sign flag information for non-zero transform coefficients in the corresponding sub-block. In this case, the sign information of each of the transform coefficients may be obtained by parsing the sign information of each of the transform coefficients for the sub-block in the current block according to a conventional method.

In addition, the decoding apparatus may determine whether to parse the original sign flag information for the sub-block in the current block based on the transform skip flag information indicating whether the transform is applied to the current block. For example, the decoding apparatus may obtain transformation skip flag information from the bitstream, and based on transformation skip flag information indicating that transformation is not applied to the current block (that is, the value of transformation skip flag information is 1 The original sign flag information can be parsed based on the case of.

As described above, according to whether the original sign flag information is parsed, the decoding apparatus may obtain each sign information for non-zero transform coefficients or obtain full sign information for non-zero transform coefficients. Also, the decoding apparatus may derive level values of non-zero transform coefficients based on the sign information.

The decoding apparatus may derive residual samples based on non-zero transform coefficients (S1620).

In one embodiment, when transformation is not applied to non-zero transform coefficients (when the value of transform skip flag information is 1 for the current block), the decoding apparatus inverse quantizes non-zero transform coefficients Residual samples of can be derived. Or, when transform is applied to non-zero transform coefficients (if the value of transform skip flag information for the current block is 0), the decoding apparatus inverse quantizes non-zero transform coefficients and dequantizes it. Residual samples of the current block can be derived by inverse transforming the coefficients. In this case, the inverse quantization process may be omitted in some cases.

The decoding apparatus may generate reconstructed samples based on the residual samples (S1630).

In an embodiment, the decoding apparatus may determine whether to perform inter prediction or intra prediction for a current block based on prediction information obtained from a bitstream, and perform prediction according to the determination to determine whether to perform prediction on the current block. Predictive samples for can be derived. In addition, the decoding apparatus may generate reconstructed samples based on the prediction samples and the residual samples. In this case, the decoding apparatus may directly use the prediction samples as reconstructed samples according to the prediction mode, or may generate reconstructed samples by adding residual samples to the prediction samples. Also, a reconstructed block or a reconstructed picture may be derived based on the reconstructed samples. Thereafter, as described above, the decoding apparatus may apply an in-loop filtering procedure such as deblocking filtering and/or SAO procedure to the reconstructed picture in order to improve subjective/objective image quality as needed.

In the above-described embodiments, the methods are described on the basis of a flowchart as a series of steps or blocks, but the embodiments of this document are not limited to the order of steps, and certain steps may be in a different order from those described above or It can occur simultaneously. Further, those skilled in the art will appreciate that the steps shown in the flowchart are not exclusive, other steps may be included, or one or more steps in the flowchart may be deleted without affecting the scope of this document.

The above-described method according to this document may be implemented in a software form, and the encoding device and/or decoding device according to this document performs image processing such as a TV, computer, smartphone, set-top box, display device, etc. Can be included in the device.

When the embodiments in this document are implemented as software, the above-described method may be implemented as a module (process, function, etc.) performing the above-described functions. The modules are stored in memory and can be executed by the processor. The memory may be inside or outside the processor, and may be connected to the processor by various well-known means. The processor may include an application-specific integrated circuit (ASIC), another chipset, a logic circuit, and/or a data processing device. The memory may include read-only memory (ROM), random access memory (RAM), flash memory, memory card, storage medium, and/or other storage device. That is, the embodiments described in this document may be implemented and performed on a processor, microprocessor, controller, or chip. For example, the functional units illustrated in each drawing may be implemented and executed on a computer, processor, microprocessor, controller, or chip. In this case, information for implementation (ex. information on instructions) or an algorithm may be stored in a digital storage medium.

In addition, decoding devices and encoding devices to which this document is applied include multimedia broadcasting transmission/reception devices, mobile communication terminals, home cinema video devices, digital cinema video devices, surveillance cameras, video chat devices, real-time communication devices such as video communications, and mobile streaming. Devices, storage media, camcorders, video-on-demand (VoD) service providers, OTT video (Over the top video) devices, Internet streaming service providers, three-dimensional (3D) video devices, virtual reality (VR) devices, AR (argumente) reality) devices, video telephony video devices, transportation means terminals (ex.vehicle (including autonomous vehicles) terminals, airplane terminals, ship terminals, etc.) and medical video devices, and can be used to process video signals or data signals. I can. For example, an OTT video (Over the top video) device may include a game console, a Blu-ray player, an Internet-connected TV, a home theater system, a smartphone, a tablet PC, and a digital video recorder (DVR).

In addition, the processing method to which the present document is applied may be produced in the form of a program executed by a computer, and may be stored in a computer-readable recording medium. Multimedia data having the data structure according to this document can also be stored in a computer-readable recording medium. The computer-readable recording medium includes all kinds of storage devices and distributed storage devices in which computer-readable data is stored. The computer-readable recording medium includes, for example, Blu-ray disk (BD), universal serial bus (USB), ROM, PROM, EPROM, EEPROM, RAM, CD-ROM, magnetic tape, floppy disk, and optical It may include a data storage device. Further, the computer-readable recording medium includes media implemented in the form of a carrier wave (for example, transmission through the Internet). In addition, the bitstream generated by the encoding method may be stored in a computer-readable recording medium or transmitted through a wired or wireless communication network.

Further, an embodiment of this document may be implemented as a computer program product using a program code, and the program code may be executed in a computer according to the embodiment of this document. The program code may be stored on a carrier readable by a computer.

Referring to FIG. 17, a content streaming system applied to embodiments of the present document may largely include an encoding server, a streaming server, a web server, a media storage device, a user device, and a multimedia input device.

The encoding server serves to generate a bitstream by compressing content input from multimedia input devices such as smartphones, cameras, camcorders, etc. into digital data, and transmits it to the streaming server. As another example, when multimedia input devices such as smartphones, cameras, camcorders, etc. directly generate bitstreams, the encoding server may be omitted.

The bitstream may be generated by an encoding method or a bitstream generation method applied to the embodiments of the present document, and the streaming server may temporarily store the bitstream while transmitting or receiving the bitstream. .

The streaming server transmits multimedia data to a user device based on a user request through a web server, and the web server serves as an intermediary for notifying the user of a service. When a user requests a desired service from the web server, the web server transmits it to the streaming server, and the streaming server transmits multimedia data to the user. In this case, the content streaming system may include a separate control server, and in this case, the control server serves to control commands/responses between devices in the content streaming system.

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

Examples of the user device include a mobile phone, a smart phone, a laptop computer, a digital broadcasting terminal, a personal digital assistant (PDA), a portable multimedia player (PMP), a navigation system, a slate PC, and Tablet PC, ultrabook, wearable device, for example, smartwatch, smart glass, head mounted display (HMD)), digital TV, desktop There may be computers, digital signage, etc.

Each server in the content streaming system may be operated as a distributed server, and in this case, data received from each server may be distributedly processed.

The claims set forth in this document may be combined in a variety of ways. For example, the technical features of the method claims of this document may be combined to be implemented as a device, and the technical features of the device claims of this document may be combined to be implemented as a method. In addition, the technical features of the method claim of this document and the technical features of the device claim may be combined to be implemented as a device, and the technical features of the method claim of this document and the technical features of the device claim may be combined to be implemented by a method. (Claims in the present description can be combined in a various way.For instance, technical features in method claims of the present description can be combined to be implemented or performed in an apparatus, and technical features in apparatus claims can be combined to be implemented or performed in a method.Further, technical features in method claim(s) and apparatus claim(s) can be combined to be implemented or performed in an apparatus.Further, technical features in method claim(s) and apparatus claim(s) can be combined to be implemented or performed in a method.)

Claims

In the video decoding method performed by the decoding device,

Obtaining residual information for a current block from the bitstream;

Deriving non-zero transform coefficients for the current block based on the residual information;

Deriving residual samples based on the non-zero transform coefficients; And

And generating reconstructed samples based on the residual samples,

The step of deriving the non-zero transform coefficients,

Determining whether to parse one sign flag information for a sub-block in the current block; And

Including the step of deriving the sign information for the non-zero transform coefficients based on whether the original sign flag information is parsed,

The original sign flag information is a syntax element indicating whether signs of non-zero transform coefficients for subblocks in the current block are all the same.
The method of claim 1,

Determining whether to parse the original sign flag information,

Based on the number of context-coded bins for syntax elements included in the residual information, it is determined whether to parse the original sign flag information for a sub-block in the current block. Video decoding method.
The method of claim 2,

The number of context-coded bins is the number of context-coded bins for sub-blocks in the current block,

Before parsing the one sign flag information, if the number of the context coded bins for the sub-blocks in the current block reaches a specific number, the one sign flag information is not parsed.
The method of claim 3,

The video decoding method, characterized in that the specific number is 32.
The method of claim 1,

Determining whether to parse the original sign flag information,

And determining whether to parse the original sign flag information for a sub-block in the current block, based on whether the number of non-zero transform coefficients is greater than or equal to a threshold value.
The method of claim 5,

The image decoding method, characterized in that the threshold value is derived from one of 0 to 16.
The method of claim 5,

The threshold value is derived based on at least one of a size of the current block, a position of the sub-block in the current block, or a prediction mode of the current block.
The method of claim 7,

When the size of the current block is 8x8, the threshold value is derived as 5,

When the size of the current block is 4x4, the threshold value is derived as 4.
The method of claim 7,

When the size of the current block is 8x8 and the subblock is a subblock on the lower right of the current block, the threshold value is derived as 5,

When the size of the current block is 8x8 and the subblock is an upper left subblock of the current block, the threshold value is derived as 7.
The method of claim 7,

When the size of the current block is 8x8, the subblock is a lower right subblock of the current block, and the prediction mode of the current block is an intra prediction mode, the threshold is derived as 0,

When the size of the current block is 8x8, the subblock is an upper left subblock of the current block, and the prediction mode of the current block is an intra prediction mode, the threshold value is derived as 5 Decoding method.
The method of claim 7,

When the size of the current block is 8x8, the subblock is a lower right subblock of the current block, and the prediction mode of the current block is an inter prediction mode, the threshold value is derived as 3,

When the size of the current block is 8x8, the subblock is an upper left subblock of the current block, and the prediction mode of the current block is an inter prediction mode, the threshold value is derived as 5 Decoding method.
The method of claim 1,

The step of obtaining transformation skip flag information indicating whether transformation is applied to the current block from the bitstream,

Determining whether to parse the original sign flag information,

And parsing the one-sign flag information for a sub-block in the current block based on the transform skip flag information indicating that no transform is applied to the current block.
In the video encoding method performed by the encoding device,

Deriving non-zero transform coefficients for the current block;

Generating residual information for the non-zero transform coefficients; And

Including the step of encoding the image information including the residual information,

Encoding the image information,

Determining whether to generate one sign flag information for a sub-block in the current block; And

Including the step of encoding the image information including the original sign flag information based on the sign information for the non-zero transform coefficients,

The original sign flag information is a syntax element indicating whether signs of non-zero transform coefficients for a subblock in the current block are all the same.
The method of claim 13,

The step of determining whether to generate the original sign flag information,

Based on the number of context-coded bins for syntax elements included in the residual information, it is determined whether to generate the one sign flag information for the sub-block in the current block. Video encoding method.
The method of claim 14,

The number of context-coded bins is the number of context-coded bins for sub-blocks in the current block,

Before generating the one sign flag information, when the number of the context coded bins for the sub-blocks in the current block reaches a specific number, the one sign flag information is not generated.
The method of claim 13,

The step of determining whether to generate the original sign flag information,

And determining whether to generate the one sign flag information based on whether the number of non-zero transform coefficients is greater than or equal to a threshold value.
The method of claim 16,

The threshold value is derived based on at least one of a size of the current block, a position of the subblock in the current block, or a prediction mode of the current block.
A computer-readable digital storage medium, comprising: a digital storage medium storing encoded image information causing to perform an image decoding method by a decoding device,

The video decoding method,

Obtaining residual information for a current block from the bitstream;

Deriving non-zero transform coefficients for the current block based on the residual information;

Deriving residual samples based on the non-zero transform coefficients; And

And generating reconstructed samples based on the residual samples,

The step of deriving the non-zero transform coefficients,

Determining whether to parse one sign flag information for a sub-block in the current block; And

Including the step of deriving the sign information for the non-zero transform coefficients based on whether the original sign flag information is parsed,

The original sign flag information is a syntax element indicating whether signs of non-zero transform coefficients for a subblock in the current block are all the same.