WO2020130705A1 - Method and apparatus for coding transform coefficient levels of transform coefficients - Google Patents

Abstract

An image decoding method, which is performed by a decoding apparatus according to the present disclosure, comprises the steps of: receiving a bitstream including residual information; deriving quantized transform coefficients for a current block on the basis of the residual information included in the bitstream; deriving transform coefficients for the current block from the quantized transform coefficients on the basis of a dequantization process; deriving residual samples for the current block by applying inverse transform to the derived transform coefficients; and generating a reconstructed picture on the basis of the residual sample for the current block.

Description

Method and apparatus for coding transform coefficient level of transform coefficients

The present disclosure relates to image coding technology, and more particularly, to a method and apparatus for coding a transform coefficient level of transform coefficients in an image coding system.

Recently, demand for high-resolution, high-quality video/video, such as 4K or 8K or higher Ultra High Definition (UHD) video/video, is increasing in various fields. As the video/video data becomes higher-resolution and higher-quality, the amount of information or bits transmitted relative to the existing video/video data increases, so the video data is transmitted using a medium such as a conventional wired/wireless broadband line or an existing storage medium. When using to store video/video data, transmission cost and storage cost increase.

In addition, recently, interest and demand for immersive media such as VR (Virtual Reality), AR (Artificial Realtiy) content, or holograms is increasing, and video/video having a video characteristic different from a real video such as a game video The broadcast for is increasing.

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

The technical problem of the present disclosure is to provide a method and apparatus for improving image coding efficiency.

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

Another technical problem of the present disclosure is to provide a method and apparatus for improving coding efficiency of a transform coefficient level of transform coefficients.

Another technical problem of the present disclosure relates to a parity level flag for a parity of a transform coefficient level, a second transform coefficient level flag indicating whether a transform coefficient level is greater than a second threshold in syntax structure with respect to a specific transform coefficient. Disclosed is a method and apparatus for reducing coding complexity and reducing delay by being coded in a pass such as a first transform coefficient level flag indicating whether a transform coefficient level is greater than a first threshold.

Another technical problem of the present disclosure is the number of valid coefficient flags for transform coefficients for the current block, indicating whether the transform coefficient level of each of the transform coefficients for the current block is a non-zero valid coefficient, the first transform coefficient level Disclosed is a method and apparatus for reducing coding complexity and reducing delay by limiting the sum of the number of flags, the number of second transform coefficient level flags, and the number of parity level flags to a predetermined threshold or less.

According to an embodiment of the present disclosure, an image decoding method performed by a decoding apparatus is provided. The method comprises: receiving a bitstream including residual information, deriving quantized transform coefficients for a current block based on the residual information included in the bitstream, an inverse quantization process Deriving transform coefficients for the current block from the quantized transform coefficients based on ), and applying residual inverse transform to the derived transform coefficients to derive residual samples for the current block And generating a reconstructed picture based on the residual sample for the current block, wherein the transform coefficients for the current block are a first transform coefficient and a second transform coded after the first transform coefficient. A coefficient, and the residual information includes: a first transform coefficient level flag for the first transform coefficient indicating whether the transform coefficient level of the first transform coefficient is greater than a first threshold, a conversion of the first transform coefficient A second transform coefficient level flag for the first transform coefficient indicating whether a coefficient level is greater than a second threshold, a second transform coefficient indicating whether the transform coefficient level of the second transform coefficient is greater than the first threshold A first transform coefficient level flag for the second transform coefficient level flag for the second transform coefficient indicating whether the transform coefficient level of the second transform coefficient is greater than the second threshold value, and wherein the second threshold value is The step of deriving the quantized transform coefficients for the current block greater than a first threshold includes: the first transform coefficient level flag for the first transform coefficient, and the second transform coefficient level for the first transform coefficient Parsing the flag, the first transform coefficient level flag for the second transform coefficient and the second transform coefficient level flag for the second transform coefficient, and deriving the transform coefficients for the current block Step 1, the first transformation The first transform coefficient level flag for the coefficient, the second transform coefficient level flag for the first transform coefficient, the first transform coefficient level flag for the second transform coefficient, and the first for the second transform coefficient And deriving the transform coefficients for the current block based on a 2 transform coefficient level flag, wherein the second transform coefficient level flag for the first transform coefficient is the first transform for the second transform coefficient. It is characterized in that it is parsed before the counting level flag.

According to another embodiment of the present disclosure, a decoding apparatus for performing image decoding is provided. The decoding apparatus receives an bitstream including residual information, and an entropy decoding unit for deriving quantized transform coefficients for a current block based on the residual information included in the bitstream, an inverse quantization process (inverse an inverse quantization unit that derives transform coefficients for the current block from the quantized transform coefficients based on a quantization process, and applies a inverse transform to the derived transform coefficients, resulting in a residual sample for the current block An inverse transform unit for deriving them and an adder for generating a reconstructed picture based on the residual sample for the current block, wherein the transform coefficients for the current block are later than the first transform coefficient and the first transform coefficient. A second transform coefficient to be coded, the residual information comprising: a first transform coefficient level flag for the first transform coefficient indicating whether a transform coefficient level of the first transform coefficient is greater than a first threshold, the first A second transform coefficient level flag for the first transform coefficient indicating whether the transform coefficient level of one transform coefficient is greater than a second threshold, the transform coefficient level of the second transform coefficient is greater than the first threshold, A first transform coefficient level flag for a second transform coefficient and a second transform coefficient level flag for the second transform coefficient indicating whether the transform coefficient level of the second transform coefficient is greater than the second threshold, and wherein The second threshold is greater than the first threshold, and deriving the quantized transform coefficients for the current block performed by the entropy decoding unit includes: the first transform coefficient level flag for the first transform coefficient, Parsing the second transform coefficient level flag for the first transform coefficient, the first transform coefficient level flag for the second transform coefficient and the second transform coefficient level flag for the second transform coefficient. And the inverse quantum The step of deriving the transform coefficients for the current block performed by the processor may include: the first transform coefficient level flag for the first transform coefficient, the second transform coefficient level flag for the first transform coefficient, and the And deriving the transform coefficients for the current block based on the first transform coefficient level flag for the second transform coefficient and the second transform coefficient level flag for the second transform coefficient, wherein the first transform coefficient is The second transform coefficient level flag for the transform coefficient is parsed before the first transform coefficient level flag for the second transform coefficient.

According to another embodiment of the present disclosure, a video encoding method performed by an encoding device is provided. The method comprises: deriving residual samples for the current block, transforming the residual samples for the current block to derive transform coefficients for the current block, from the transform coefficients based on a quantization process Deriving quantized transform coefficients and encoding residual information including information about the quantized transform coefficients, wherein the transform coefficients for the current block include a first transform coefficient and the first transform coefficient. A second transform coefficient that is coded later than a transform coefficient, and the residual information is a first transform coefficient level for the first transform coefficient indicating whether the transform coefficient level of the first transform coefficient is greater than a first threshold Flag, a second transform coefficient level flag for the first transform coefficient indicating whether the transform coefficient level of the first transform coefficient is greater than a second threshold, whether a transform coefficient level of the second transform coefficient is greater than the first threshold A first transform coefficient level flag for the second transform coefficient indicating whether and a second transform coefficient level flag for the second transform coefficient indicating whether the transform coefficient level of the second transform coefficient is greater than the second threshold Including, the second threshold is greater than the first threshold, and encoding the residual information, based on the transform coefficients for the current block, the first transform coefficient level for the first transform coefficient Encoding a flag, the second transform coefficient level flag for the first transform coefficient, the first transform coefficient level flag for the second transform coefficient, and the second transform coefficient level flag for the second transform coefficient. And the second transform coefficient level flag for the first transform coefficient is encoded before the first transform coefficient level flag for the second transform coefficient.

According to another embodiment of the present disclosure, an encoding apparatus for performing video encoding is provided. The encoding apparatus includes a subtraction unit for deriving residual samples for the current block, a transformation unit for transforming the residual samples for the current block to derive transform coefficients for the current block, and the transformation based on a quantization process A quantization unit for deriving quantized transform coefficients from coefficients and an entropy encoding unit for encoding residual information including information about the quantized transform coefficients, wherein the transform coefficients for the current block are first transformed A coefficient and a second transform coefficient coded after the first transform coefficient, and the residual information is for the first transform coefficient indicating whether the transform coefficient level of the first transform coefficient is greater than a first threshold value A first transform coefficient level flag, a second transform coefficient level flag for the first transform coefficient indicating whether the transform coefficient level of the first transform coefficient is greater than a second threshold, and a transform coefficient level of the second transform coefficient are A first transform coefficient level flag for the second transform coefficient indicating whether it is greater than a first threshold and a second transform coefficient for the second transform coefficient indicating whether the transform coefficient level of the second transform coefficient is greater than the second threshold A transform coefficient level flag, wherein the second threshold is greater than the first threshold, and encoding the residual information performed by the entropy encoding unit comprises: based on the transform coefficients for the current block, The first transform coefficient level flag for the first transform coefficient, the second transform coefficient level flag for the first transform coefficient, the first transform coefficient level flag for the second transform coefficient, and the second transform coefficient Encoding the second transform coefficient level flag for and wherein the second transform coefficient level flag for the first transform coefficient is encoded before the first transform coefficient level flag for the second transform coefficient. It is characterized by.

According to another embodiment of the present disclosure, a decoder readable storage medium is provided that stores information about instructions that cause a video decoding apparatus to perform decoding methods according to some embodiments.

According to another embodiment of the present disclosure, a decoder readable storage medium is provided that stores information on instructions that cause a video decoding apparatus to perform a decoding method according to an embodiment. The decoding method according to the embodiment may include receiving a bitstream including residual information, and deriving quantized transform coefficients for a current block based on the residual information included in the bitstream, inverse Deriving transform coefficients for the current block from the quantized transform coefficients based on an inverse quantization process, and applying an inverse transform to the derived transform coefficients to register the current block Deriving dual samples and generating a reconstructed picture based on the residual sample for the current block, wherein the transform coefficients for the current block are greater than the first transform coefficient and the first transform coefficient. A second transform coefficient that is coded later, and the residual information includes: a first transform coefficient level flag for the first transform coefficient indicating whether the transform coefficient level of the first transform coefficient is greater than a first threshold, the A second transform coefficient level flag for the first transform coefficient indicating whether the transform coefficient level of the first transform coefficient is greater than a second threshold, and whether the transform coefficient level of the second transform coefficient is greater than the first threshold A first transform coefficient level flag for the second transform coefficient and a second transform coefficient level flag for the second transform coefficient indicating whether the transform coefficient level of the second transform coefficient is greater than the second threshold, The second threshold is greater than the first threshold, and deriving the quantized transform coefficients for the current block includes: the first transform coefficient level flag for the first transform coefficient, and the first transform coefficient for the first transform coefficient. Parsing the second transform coefficient level flag, the first transform coefficient level flag for the second transform coefficient, and the second transform coefficient level flag for the second transform coefficient, and for the current block. Deriving the transform coefficients The steps include: the first transform coefficient level flag for the first transform coefficient, the second transform coefficient level flag for the first transform coefficient, the first transform coefficient level flag for the second transform coefficient, and the first And deriving the transform coefficients for the current block based on the second transform coefficient level flag for the second transform coefficient, wherein the second transform coefficient level flag for the first transform coefficient is the second transform. It is characterized in that it is parsed before the first transform coefficient level flag for the coefficient.

According to the present disclosure, overall image/video compression efficiency can be improved.

According to the present disclosure, the efficiency of residual coding can be increased.

According to the present disclosure, coding efficiency of a transform coefficient level of transform coefficients can be increased.

According to the present disclosure, with respect to a specific transform coefficient, a second transform coefficient level flag indicating whether a transform coefficient level is greater than a second threshold in syntax structure includes a parity level flag and a transform coefficient level for parity of the transform coefficient level. It is possible to reduce coding complexity and reduce delay by being coded in a pass such as a first transform coefficient level flag indicating whether it is greater than a first threshold.

According to the present disclosure, the number of valid coefficient flags for transform coefficients for the current block, the number of first transform coefficient level flags, indicating whether the transform coefficient level of each of the transform coefficients for the current block is a non-zero valid coefficient, By limiting the sum of the number of second transform coefficient level flags and the number of parity level flags to a predetermined threshold or less, coding complexity and delay can be reduced.

1 schematically shows an example of a video/image coding system to which the present disclosure can be applied.

2 is a diagram schematically illustrating a configuration of a video/video encoding apparatus to which the present disclosure can be applied.

3 is a diagram schematically illustrating a configuration of a video/video decoding apparatus to which the present disclosure can be applied.

4 is a block diagram of a CABAC encoding system according to an embodiment.

5 is a diagram showing an example of transform coefficients in a 4x4 block.

6 is a flowchart illustrating an operation of an encoding apparatus according to an embodiment.

7 is a block diagram showing the configuration of an encoding apparatus according to an embodiment.

8 is a flowchart illustrating an operation of a decoding apparatus according to an embodiment.

9 is a block diagram showing the configuration of a decoding apparatus according to an embodiment.

10 shows an example of a content streaming system to which the invention disclosed in this document can be applied.

According to an embodiment of the present disclosure, an image decoding method performed by a decoding apparatus is provided. The method comprises: receiving a bitstream including residual information, deriving quantized transform coefficients for a current block based on the residual information included in the bitstream, an inverse quantization process Deriving transform coefficients for the current block from the quantized transform coefficients based on ), and applying residual inverse transform to the derived transform coefficients to derive residual samples for the current block And generating a reconstructed picture based on the residual sample for the current block, wherein the transform coefficients for the current block are a first transform coefficient and a second transform coded after the first transform coefficient. A coefficient, and the residual information includes: a first transform coefficient level flag for the first transform coefficient indicating whether the transform coefficient level of the first transform coefficient is greater than a first threshold, a conversion of the first transform coefficient A second transform coefficient level flag for the first transform coefficient indicating whether a coefficient level is greater than a second threshold, a second transform coefficient indicating whether the transform coefficient level of the second transform coefficient is greater than the first threshold A first transform coefficient level flag for the second transform coefficient level flag for the second transform coefficient indicating whether the transform coefficient level of the second transform coefficient is greater than the second threshold value, and wherein the second threshold value is The step of deriving the quantized transform coefficients for the current block greater than a first threshold includes: the first transform coefficient level flag for the first transform coefficient, and the second transform coefficient level for the first transform coefficient Parsing the flag, the first transform coefficient level flag for the second transform coefficient and the second transform coefficient level flag for the second transform coefficient, and deriving the transform coefficients for the current block Step 1, the first transformation The first transform coefficient level flag for the coefficient, the second transform coefficient level flag for the first transform coefficient, the first transform coefficient level flag for the second transform coefficient, and the first for the second transform coefficient And deriving the transform coefficients for the current block based on a 2 transform coefficient level flag, wherein the second transform coefficient level flag for the first transform coefficient is the first transform for the second transform coefficient. It is characterized in that it is parsed before the counting level flag.

The present disclosure may be variously modified and may have various embodiments, and specific embodiments will be illustrated in the drawings and described in detail. However, this is not intended to limit the present disclosure to specific embodiments. Terms used in this specification are only used to describe specific embodiments, and are not intended to limit the technical spirit of the present disclosure. Singular expressions include plural expressions unless the context clearly indicates otherwise. In this specification, the terms “include” or “have” are intended to indicate that a feature, number, step, operation, component, part, or combination thereof described in the specification exists, or that one or more other features or It should be understood that numbers, steps, operations, components, parts, or combinations thereof do not preclude the presence or the likelihood of addition.

Meanwhile, each configuration in the drawings described in the present disclosure is independently illustrated for convenience of description of different characteristic functions, and does not mean that each configuration is implemented with separate hardware or separate software. For example, two or more components of each component may be combined to form one component, or one component may be divided into a plurality of components. Embodiments in which each configuration is integrated and/or separated are also included in the scope of the present disclosure without departing from the essence of the present disclosure.

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

1 schematically shows an example of a video/image coding system to which the present disclosure can be applied.

This document is about video/video coding. For example, the methods/embodiments disclosed in this document may include 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 next-generation video/ It can be applied to the method disclosed in the video coding standard (ex. H.267 or H.268, etc.).

In this document, various embodiments of video/image coding are proposed, and the above embodiments may be performed in combination with each other unless otherwise specified.

In this document, video may refer to 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. The slice/tile may include one or more coding tree units (CTUs). One picture may be composed of one or more slices/tiles. One picture may be composed of one or more tile groups. One tile group may include one or more tiles. The brick may represent a rectangular region of CTU rows within a tile in a picture. Tiles can be partitioned into multiple bricks, and each brick can be composed of one or more CTU rows in the tile (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 can indicate a specific sequential ordering of CTUs partitioning a picture, the CTUs can be aligned with a CTU raster scan within a brick, and bricks in a tile can be aligned sequentially with a raster scan of the bricks of the tile. A, and tiles in a picture can be sequentially aligned with a 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 area of CTUs, the rectangular area has a height equal to the height of the picture, and the width can 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 the height can 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 can indicate a specific sequential ordering of CTUs partitioning a picture, the CTUs can be successively aligned with a CTU raster scan in a tile, and the tiles in a picture can be successively aligned with 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 are used interchangeably in this document. For example, the tile group/tile group header in this document 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. The sample may generally represent a pixel or a pixel value, may represent only a pixel/pixel value of a luma component, or may represent only a pixel/pixel value of a chroma component.

The unit may represent a basic unit of image processing. The unit may include at least one of a specific region of a picture and information related to the region. 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 area depending on the case. In the general case, the MxN block may include samples (or sample arrays) of M columns and N rows or a set (or array) of transform coefficients.

In this document, "/" and "," are interpreted as "and/or". For example, “A/B” is interpreted as “A and/or B”, and “A, B” is interpreted as “A and/or B”. Additionally, “A/B/C” means “at least one of A, B and/or C”. Also, “A, B, and C” means “at least one of A, B, and/or C”. (In this document, the term "/" and "," should be interpreted to indicate "and/or." For instance, the expression "A/B" may mean "A and/or B." Further, "A, B" may mean "A and/or B." Further, "A/B/C" may mean "at least one of A, B, and/or C." Also, "A/B/C" may mean " at least one of A, B, and/or C.")

Additionally, "or" in this document is interpreted as "and/or." For example, “A or B” may mean 1) only “A”, 2) only “B”, or 3) “A and B”. In other words, “or” in this document may mean “additionally or alternatively”. (Further, in the document, the term "or" should be interpreted to indicate "and/or." For instance, the expression "A or B" may comprise 1) only A, 2) only B, and/or 3) both A and B. In other words, the term "or" in this document should be interpreted to indicate "additionally or alternatively.")

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

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 apparatus, and a renderer. The encoding device may be called a video/video encoding device, and the decoding device may be called a video/video decoding device. The transmitter can 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 capture, synthesis, or generation process of the video/image. The video source may include a video/image capture device and/or a video/image generation 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 capture process may be replaced by a process of generating related data.

The encoding device can 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/image information) may be output in the form of a bitstream.

The transmitting unit may transmit the encoded video/video information or data output in the form of a bitstream to a receiving unit of a receiving device through a digital storage medium or a network in a file or streaming format. The digital storage media may include various storage media such as USB, SD, CD, DVD, Blu-ray, HDD, 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 deliver it to a decoding device.

The decoding apparatus 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 apparatus.

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

2 is a diagram schematically illustrating a configuration of a video/video encoding apparatus to which the present disclosure can be applied. Hereinafter, the video encoding device may include a video encoding device.

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

The image division 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 called a coding unit (CU). In this case, the coding unit is recursively divided according to a quad-tree binary-tree ternary-tree (QTBTTT) structure from a coding tree unit (CTU) or a largest coding unit (LCU). 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, a binary tree structure may be applied first. The coding procedure according to the present disclosure can be performed based on the final coding unit that is no longer split. In this case, the maximum coding unit may be directly used as a final coding unit based on coding efficiency according to image characteristics, or the coding unit may be recursively divided into coding units having a lower depth than optimal, if necessary. The coding unit of the size of can be used as the final coding unit. Here, the coding procedure may include procedures such as prediction, transformation, and reconstruction, which will be 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 partitioned or partitioned from the above-described final coding unit, respectively. The prediction unit may be a unit of sample prediction, and the transformation unit may be a unit for deriving a transform coefficient and/or a unit for deriving a residual signal from the transform coefficient.

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

The encoding device 200 subtracts a prediction signal (a predicted block, a prediction sample array) output from the inter prediction unit 221 or the intra prediction unit 222 from the input image signal (original block, original sample array). A signal (residual signal, residual block, residual sample array) may be generated, and the generated residual signal is transmitted to the conversion unit 232. In this case, as illustrated, a unit for subtracting a prediction signal (a prediction block, a prediction sample array) from an 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 is applied to the current block or CU or inter prediction is applied. As described later in the description of each prediction mode, the prediction unit may generate various information about prediction, such as prediction mode information, and transmit it to the entropy encoding unit 240. The prediction information 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 neighbor of the current block or may be located apart depending on a 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 the degree of detail 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 using a prediction mode applied to neighboring blocks.

The inter prediction unit 221 may derive the predicted block for the current block based on a reference block (reference sample array) specified by a motion vector on the reference picture. At this time, 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 the correlation of motion information between a neighboring block and a 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 present in the current picture and a temporal neighboring block present 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 or a colCU, and a reference picture including the temporal neighboring block may be called a collocated picture (colPic). It might be. For example, the inter prediction unit 221 constructs a motion information candidate list based on neighboring blocks, and provides information indicating which candidates are used to derive the motion vector and/or reference picture index of the current block. Can be created. Inter prediction may be performed based on various prediction modes. For example, in the case of the skip mode and the merge mode, the inter prediction unit 221 may use motion information of neighboring blocks as motion information of the current block. In the skip mode, unlike the merge mode, the residual signal may not be transmitted. In the motion vector prediction (MVP) mode, the motion vector of the current block is obtained by using the motion vector of the neighboring block as a motion vector predictor and signaling a motion vector difference. I can order.

The prediction unit 220 may generate a prediction signal based on various prediction methods described below. For example, the prediction unit may apply intra prediction or inter prediction as well as intra prediction and inter prediction at the same time for prediction for one block. This can be called combined inter and intra prediction (CIIP). Also, the prediction unit may be based on an intra block copy (IBC) prediction mode or a palette mode for prediction of a block. The IBC prediction mode or palette mode may be used for content video/video coding such as a game, such as screen content coding (SCC). IBC basically performs prediction in the current picture, but can be performed similarly to inter prediction in that a reference block is derived in the current picture. That is, the IBC can use at least one of the inter prediction techniques described in this document. The palette mode can be regarded 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 on the palette table and palette index.

The prediction signal generated through 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, at least one of a DCT (Discrete Cosine Transform), DST (Discrete Sine Transform), KLT (Karhunen-Loeve Transform), GBT (Graph-Based Transform), or CNT (Conditionally Non-linear Transform) It can contain. Here, GBT refers to a transformation obtained from this graph when it is said to graphically represent relationship information between pixels. CNT means a transform obtained by generating a prediction signal using all previously reconstructed pixels and based on it. Further, the transform process may be applied to pixel blocks having the same size of a square, or may be applied to blocks of variable sizes other than squares.

The quantization unit 233 quantizes the transform coefficients and transmits them to the entropy encoding unit 240, and the entropy encoding unit 240 encodes a quantized signal (information about quantized transform coefficients) and outputs it as a bitstream. have. Information about the quantized transform coefficients may be referred to as residual information. The quantization unit 233 may rearrange block-type quantized transform coefficients into a one-dimensional vector form based on a coefficient scan order, and quantize the quantized transform coefficients based on the one-dimensional vector form. Information regarding transform coefficients may be generated. The entropy encoding unit 240 may perform various encoding methods such as exponential Golomb (CAVLC), context-adaptive variable length coding (CAVLC), and context-adaptive binary arithmetic coding (CABAC). The entropy encoding unit 240 may encode information necessary for video/image reconstruction (eg, a value of syntax elements, etc.) together with the quantized transform coefficients together or separately. The encoded information (ex. encoded video/video information) may be transmitted or stored in units of network abstraction layer (NAL) units in the form of a bitstream. The video/image information may further include information regarding various parameter sets such as an adaptation parameter set (APS), a picture parameter set (PPS), a sequence parameter set (SPS), or a video parameter set (VPS). In addition, the video/image information may further include general constraint information. In this document, information and/or syntax elements transmitted/signaled from an encoding device to a decoding device may be included in video/video information. The video/video information may be encoded through the above-described encoding procedure and included in the bitstream. The bitstream can be transmitted over a network or stored on a digital storage medium. Here, the network may include a broadcasting network and/or a communication network, and the digital storage medium may include various storage media such as USB, SD, CD, DVD, Blu-ray, HDD, SSD. The signal output from the entropy encoding unit 240 may be configured as an internal/external element of the encoding device 200 by a transmitting unit (not shown) and/or a storing unit (not shown) for storing, or the transmitting 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 transformation through the inverse quantization unit 234 and the inverse transformation unit 235 to the quantized transform coefficients. The adder 155 adds the reconstructed residual signal to the predicted signal output from the inter predictor 221 or the intra predictor 222, so that the reconstructed signal (restored picture, reconstructed block, reconstructed sample array) Can be generated. If there is no residual for the block to be processed, such as when the skip mode is applied, the predicted block may be used as a reconstructed block. The adder 250 may be called a restoration unit or a restoration block generation unit. The generated reconstructed signal may be used for intra prediction of a next processing target block in a current picture, or may be used for inter prediction of a next picture through filtering as described below.

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

The filtering unit 260 may apply subjective/objective filtering to improve subjective/objective image quality. For example, the filtering unit 260 may generate a modified restoration picture by applying various filtering methods to the restoration picture, and the modified restoration picture may be a DPB of the memory 270, specifically, the memory 270. Can be stored in. 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 various information regarding filtering as described later in the description of each filtering method, and transmit the generated information to the entropy encoding unit 240. 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 the inter prediction is applied through the encoding apparatus, prediction mismatch between the encoding apparatus 100 and the decoding apparatus can be avoided, and encoding efficiency can be improved.

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 has already been reconstructed. The stored motion information may be transmitted to the inter prediction unit 221 to be used as motion information of a spatial neighboring block or motion information of a temporal neighboring block. The memory 270 may store reconstructed samples of blocks reconstructed in the current picture, and may transmit the reconstructed samples to the intra prediction unit 222.

3 is a diagram schematically illustrating a configuration of a video/video decoding apparatus to which the present disclosure can be applied.

Referring to FIG. 3, the decoding apparatus 300 includes an entropy decoder (310), a residual processor (320), a prediction unit (predictor, 330), an adder (340), and a filtering unit (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 deequantizer (321) and an inverse transformer (321). The entropy decoding unit 310, the residual processing unit 320, the prediction unit 330, the adding unit 340, and the filtering unit 350 described above may include one hardware component (eg, a decoder chipset or processor) according to an embodiment. ). Also, the memory 360 may include a decoded picture buffer (DPB), or may be configured by a digital storage medium. The hardware component may further include a memory 360 as an internal/external component.

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

The decoding apparatus 300 may receive the 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/image information) necessary for image reconstruction (or picture reconstruction). The video/image information may further include information regarding various parameter sets such as an adaptation parameter set (APS), a picture parameter set (PPS), a sequence parameter set (SPS), or a video parameter set (VPS). In addition, the video/image information may further include general constraint information. The decoding apparatus may decode a picture further based on the information on the parameter set and/or the general restriction information. Signaling/receiving 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 a bitstream based on a coding method such as exponential Golomb coding, CAVLC, or CABAC, and quantizes a value of a syntax element required for image reconstruction and a transform coefficient for residual. Can output More specifically, the CABAC entropy decoding method receives bins corresponding to each syntax element in a bitstream, and decodes syntax element information to be decoded and decoding information of neighboring and decoded blocks or symbol/bin information decoded in the previous step. The context model is determined by using, and the probability of occurrence of the bin is predicted according to the determined context model, and arithmetic decoding of the bin is performed to generate a symbol corresponding to the value of each syntax element. have. At this time, the CABAC entropy decoding method may update the context model using the decoded symbol/bin information for the next symbol/bin context model after determining the context model. Among the information decoded by the entropy decoding unit 310, prediction information is provided to a prediction unit (inter prediction unit 332 and intra prediction unit 331), and the entropy decoding unit 310 performs entropy decoding. The dual value, that is, quantized transform coefficients and related parameter information may be input to the residual processor 320. The residual processing unit 320 may derive a residual signal (residual block, residual samples, residual sample array). Also, information related to filtering among information decoded by the entropy decoding unit 310 may be provided to the filtering unit 350. Meanwhile, a receiving unit (not shown) receiving a signal output from the encoding device may be further configured as an internal/external element of the decoding device 300, or the receiving unit may be a component of the entropy decoding unit 310. Meanwhile, the decoding device according to this document may be called a video/picture/picture decoding device, and the decoding device may be classified into an information decoder (video/picture/picture information decoder) and a sample decoder (video/picture/picture sample decoder). It might be. The information decoder may include the entropy decoding unit 310, and the sample decoder may include the inverse quantization unit 321, an inverse transformation unit 322, an addition unit 340, a filtering unit 350, and a memory 360 ), at least one of an inter prediction unit 332 and an intra prediction unit 331.

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

The inverse transform unit 322 inversely transforms the transform coefficients to obtain a residual signal (residual block, residual sample array).

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 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 described below. For example, the prediction unit may apply intra prediction or inter prediction as well as intra prediction and inter prediction at the same time for prediction for one block. This can be called combined inter and intra prediction (CIIP). Also, the prediction unit may be based on an intra block copy (IBC) prediction mode or a palette mode for prediction of a block. The IBC prediction mode or palette mode may be used for content video/video coding such as a game, such as screen content coding (SCC). IBC basically performs prediction in the current picture, but can be performed similarly to inter prediction in that a reference block is derived in the current picture. That is, the IBC can use at least one of the inter prediction techniques described in this document. The palette mode can be regarded as an example of intra coding or intra prediction. When the pallet mode is applied, information on the pallet table and pallet index may be included in the video/image 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 neighbor of the current block or may be located apart depending on a 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 using a prediction mode applied to neighboring blocks.

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. At this time, 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 the correlation of motion information between a neighboring block and a 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 present in the current picture and a temporal neighboring block present 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 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 information on the prediction may include information indicating a mode of inter prediction for the current block.

The adding unit 340 reconstructs the obtained residual signal by adding it 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). A signal (restored picture, reconstructed block, reconstructed sample array) can be generated. If there is no residual for the block to be processed, such as when the skip mode is applied, the predicted block may be used as a reconstructed block.

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

Meanwhile, LMCS (luma mapping with chroma scaling) may be applied in a 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 a DPB of the memory 360, specifically, 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 (corrected) 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 has already been reconstructed. The stored motion information may be transmitted to the inter prediction unit 260 to be used as motion information of a spatial neighboring block or motion information of a temporal neighboring block. The memory 360 may store reconstructed samples of blocks reconstructed in the current picture, and may transmit the reconstructed samples to the intra prediction unit 331.

In the present specification, the embodiments described in the filtering unit 260, the inter prediction unit 221, and the intra prediction unit 222 of the encoding device 100 are respectively the filtering unit 350 and the inter prediction of the decoding device 300. The unit 332 and the intra prediction unit 331 may be applied to the same or corresponding.

As described above, in performing video coding, prediction is performed to improve compression efficiency. Through this, a predicted block including prediction samples for a current block, which is a block to be coded, may be generated. Here, the predicted block includes prediction samples in a spatial domain (or pixel domain). The predicted block is derived equally from an encoding device and a decoding device, and the encoding device decodes information (residual information) about the residual between the original block and the predicted block, not the original sample value itself of the original block. Signaling to the device can improve video coding efficiency. The decoding apparatus may derive a residual block including residual samples based on the residual information, and combine the residual block and the predicted block to generate a reconstructed block including reconstructed samples, and reconstruct the reconstructed blocks. It is possible to generate a reconstructed picture that includes.

The residual information may be generated through transformation and quantization procedures. For example, the encoding device derives a residual block between the original block and the predicted block, and derives transformation coefficients by performing a transformation procedure on residual samples (residual sample array) included in the residual block And, by performing a quantization procedure on the transform coefficients, the quantized transform coefficients are derived to signal related residual information (via a bitstream) to a decoding apparatus. Here, the residual information may include information such as value information of the quantized transform coefficients, location information, a transform technique, a transform kernel, and quantization parameters. The decoding apparatus may perform an inverse quantization/inverse transformation 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 device may also dequantize/inverse transform quantized transform coefficients for reference for inter prediction of a picture to derive a residual block, and generate a reconstructed picture based thereon.

4 is a block diagram of a CABAC encoding system according to an embodiment.

4, a block diagram of CABAC for encoding a single syntax element is shown. In the encoding process of CABAC, first, when the input signal is a syntax element rather than a binary value, the input signal may be converted to a binary value through binarization. If the input signal is already binary, it can be bypassed without going through binarization. Here, each binary 0 or 1 constituting a binary value may be referred to as a bin. For example, when the binary string after binarization is 110, each of 1, 1, and 0 may be referred to as one bin.

Binary bins may be input to a regular encoding engine or a bypass encoding engine. The regular encoding engine may allocate a context model (or context model) reflecting a probability value for the bin, and encode the bin based on the assigned context model. In the regular encoding engine, after encoding for each bin, the probability model for the bin can be updated. These encoded bins are called context-coded bins. The bypass encoding engine may omit the procedure of estimating the probability of the input bin and the procedure of updating the probability model applied to the bin after encoding. Instead of allocating context, it is possible to improve the encoding speed by encoding the input bin by applying a uniform probability distribution. The bins thus coded may be referred to as bypass bins.

Entropy encoding may determine whether to perform encoding through a regular encoding engine or to perform encoding through a bypass encoding engine, and may switch encoding paths. Entropy decoding can be performed in the same order as encoding.

In one embodiment, the (quantized) transformation coefficients are coded based on the syntax elements such as transform_skip_flag, 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, rem_abs_gt1_flag, rem_abs_gt2_flag, abs_remainder, coeff_sign_flag, mts_idx (syntax elements) And/or decrypted. Table 1 below shows syntax elements related to residual data encoding.

residual_coding(　x0,　y0,　log2TbWidth,　log2TbHeight,　cIdx　) {	Descriptor
if( transform_skip_enabled_flag && (　cIdx　!　=　0　　|　|　　cu_mts_flag[　x0　]][　y0　]　=　=　0　) && (　log2TbWidth　　<=　　2　) && (　log2TbHeight　　<=　　2　))
transform_skip_flag[　x0　][　y0　][　cIdx　]	ae(v)
last_sig_coeff_x_prefix	ae(v)
last_sig_coeff_y_prefix	ae(v)
if( last_sig_coeff_x_prefix> 3)
last_sig_coeff_x_suffix	ae(v)
if( last_sig_coeff_y_prefix> 3)
last_sig_coeff_y_suffix	ae(v)
log2SbSize　=　( Min( log2TbWidth, log2TbHeight )　<　2? 1: 2)
numSbCoeff = 1 << (log2SbSize　<<　1)
lastScanPos = numSbCoeff
lastSubBlock = (1　　<<　　( log2TbWidth　+　log2TbHeight　-　2　*　log2SbSize) )　-1
do {
if( lastScanPos =　= 0) {
lastScanPos = numSbCoeff
lastSubBlock--
}
lastScanPos--
xS = DiagScanOrder[　log2TbWidth　-　log2SbSize　][　log2TbHeight　*?*log2SbSize　] [　lastSubBlock　][　0　]
yS = DiagScanOrder[　log2TbWidth　-　log2SbSize　][　log2TbHeight　*?*log2SbSize　] [　lastSubBlock　][　1　]
xC = (xS << log2SbSize) + DiagScanOrder[　log2SbSize　][　log2SbSize　][　lastScanPos　][　0　]
yC = (yS << log2SbSize) + DiagScanOrder[　log2SbSize　][　log2SbSize　][　lastScanPos　][　1　]
} while( (xC != LastSignificantCoeffX) |　| (yC != LastSignificantCoeffY))
QState = 0
for( i = lastSubBlock; i >= 0; i--) {
startQStateSb = QState
xS = DiagScanOrder[　log2TbWidth　-　log2SbSize　][　log2TbHeight　-log2SbSize　] [　lastSubBlock　][　0　]
yS = DiagScanOrder[　log2TbWidth　-　log2SbSize　][　log2TbHeight　-log2SbSize　] [　lastSubBlock　][　1　]
inferSbDcSigCoeffFlag = 0
if( (i　<　lastSubBlock) && (i　>　0)) {
coded_sub_block_flag[　xS　][　yS　]	ae(v)
inferSbDcSigCoeffFlag = 1
}
firstSigScanPosSb = numSbCoeff
lastSigScanPosSb = -1
for( n = (i =　= lastSubBlock)? lastScanPos　-　1: numSbCoeff　-1; n >= 0; n--) {
xC = (xS << log2SbSize) + DiagScanOrder[　log2SbSize　][　log2SbSize　][　n　][　0　]
yC = (yS << log2SbSize) + DiagScanOrder[　log2SbSize　][　log2SbSize　][　n　][　1　]
if( coded_sub_block_flag[　xS　][　yS　] && (n　>　0 |　| !inferSbDcSigCoeffFlag)) {
sig_coeff_flag[　xC　][　yC　]	ae(v)
}
if( sig_coeff_flag[　xC　][　yC　]) {
par_level_flag[　n　]	ae(v)
rem_abs_gt1_flag[　n　]	ae(v)
if( lastSigScanPosSb =　= -1)
lastSigScanPosSb = n
firstSigScanPosSb = n
}
AbsLevelPass1[　xC　][　yC　] = sig_coeff_flag[　xC　][　yC　] + par_level_flag[　n　] + 2 * rem_abs_gt1_flag[　n　]
if( dep_quant_enabled_flag)
QState = QStateTransTable[　QState　][　par_level_flag[　n　]　]
}
for( n = numSbCoeff　-　1; n >= 0; n--) {
if( rem_abs_gt1_flag[　n　])
rem_abs_gt2_flag[　n　]	ae(v)
}
for( n = numSbCoeff　-　1; n >= 0; n--) {
xC = (xS << log2SbSize) + DiagScanOrder[　log2SbSize　][　log2SbSize　][　n　][　0　]
yC = (yS << log2SbSize) + DiagScanOrder[　log2SbSize　][　log2SbSize　][　n　][　1　]
if( rem_abs_gt2_flag[　n　])
abs_remainder[　n　]
AbsLevel[　xC　][　yC　] = AbsLevelPass1[　xC　][　yC　] + 2 * (rem_abs_gt2_flag[　n　] + abs_remainder[　n　])
}
if( dep_quant_enabled_flag |　| !sign_data_hiding_enabled_flag)
signHidden = 0
else
signHidden = (lastSigScanPosSb-firstSigScanPosSb> 3? 1: 0)
for( n = numSbCoeff　-　1; n >= 0; n--) {
xC = (xS << log2SbSize) + DiagScanOrder[　log2SbSize　][　log2SbSize　][　n　][　0　]
yC = (yS << log2SbSize) + DiagScanOrder[　log2SbSize　][　log2SbSize　][　n　][　1　]
if( sig_coeff_flag[　xC　][　yC　] && (!signHidden |　| (n != firstSigScanPosSb)))
coeff_sign_flag[　n　]	ae(v)
}
if( dep_quant_enabled_flag) {
QState = startQStateSb
for( n = numSbCoeff　-　1; n >= 0; n--) {
xC = (xS << log2SbSize) + DiagScanOrder[　log2SbSize　][　log2SbSize　][　n　][　0　]
yC = (yS << log2SbSize) + DiagScanOrder[　log2SbSize　][　log2SbSize　][　n　][　1　]
if( sig_coeff_flag[　xC　][　yC　])
TransCoeffLevel[　x0　][　y0　][　cIdx　][　xC　][　yC　] = (2 * AbsLevel[　xC　][　yC　]-(QState> 1 1: 0)) * (1-2 * coeff_sign_flag[　n　])
QState = QStateTransTable[　QState　][　par_level_flag[　n　]　]
} else {
sumAbsLevel = 0
for( n = numSbCoeff　-　1; n >= 0; n--) {
xC = (xS << log2SbSize) + DiagScanOrder[　log2SbSize　][　log2SbSize　][　n　][　0　]
yC = (yS << log2SbSize) + DiagScanOrder[　log2SbSize　][　log2SbSize　][　n　][　1　]
if( sig_coeff_flag[　xC　][　yC　]　) {
TransCoeffLevel[　x0　][　y0　][　cIdx　][　xC　][　yC　] = AbsLevel[　xC　][　yC　] * (1-2 * coeff_sign_flag[　n　])
if( signHidden) {
sumAbsLevel += AbsLevel[　xC　][　yC　]
if( (n =　= firstSigScanPosSb) && (sumAbsLevel　%　2　) =　= 1　))
TransCoeffLevel[　x0　][　y0　][　cIdx　][　xC　][　yC　] = -TransCoeffLevel[　x0　][　y0　][　cIdx　][　xC　][　yC　]
}
}
}
}
}
if(　　cu_mts_flag[　x0　][　y0　]　　&&　　(　cIdx　　=　=　　0　) && !transform_skip_flag[　x0　][　y0　][　cIdx　] && ((　CuPredMode[　x0　][　y0　]　　　　　　　　　　　　　　　　　　　　　　　　　　[　X0　][　y0　]　　=　=　　MODE_INTER　) )　　) {
mts_idx[　x0　][　y0　]	ae(v)
}

transform_skip_flag indicates whether transform is omitted in an associated block. The associated block may be a coding block (CB) or a transform block (TB). With regard to transform (and quantization) and residual coding procedures, CB and TB can be mixed. For example, it is as described above that residual samples are derived for CB, and (quantized) transform coefficients can be derived through transformation and quantization of the residual samples, through the residual coding procedure. Information (eg, syntax elements) that efficiently indicates the position, size, and sign of the (quantized) transform coefficients may be generated and signaled. The quantized transform coefficients can simply be called transform coefficients. In general, if the CB is not larger than the maximum TB, the size of the CB may be the same as the size of the TB, and in this case, the target block to be transformed (and quantized) and residual coded may be called CB or TB. On the other hand, when the CB is larger than the maximum TB, the target block to be transformed (and quantized) and residual coded may be called TB. Hereinafter, syntax elements related to residual coding are described as being signaled in units of a transform block (TB), but as an example, the TB may be mixed with a coding block (CB) as described above.

In one embodiment, (x, y) position information of the last non-zero transform coefficient in a transform block may be encoded based on the syntax elements last_sig_coeff_x_prefix, last_sig_coeff_y_prefix, last_sig_coeff_x_suffix, and last_sig_coeff_y_suffix. More specifically, last_sig_coeff_x_prefix represents the prefix of the column position of the last significant coefficient in the scan order in the transform block, last_sig_coeff_y_prefix is the scan in the transform block The prefix of the row position of the last significant coefficient in the scanning order, and last_sig_coeff_x_suffix is the last in the scanning order in the transform block ) Represents the suffix of the column position of the significant coefficient, and last_sig_coeff_y_suffix is the row of the last significant coefficient in the scanning order in the transform block Represents the suffix of the row position. Here, the effective coefficient may represent the non-zero coefficient. The scan order may be a diagonal upward 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.

Then, after dividing the transform block into 4x4 sub-blocks, a 1-bit syntax element coded_sub_block_flag for each 4x4 sub-block may be used to indicate whether a non-zero coefficient exists in the current sub-block.

If the value of coded_sub_block_flag is 0, since there is no more information to transmit, the encoding process for the current subblock can be ended. Conversely, if the value of coded_sub_block_flag is 1, the encoding process for sig_coeff_flag can be continuously performed. Since the subblock containing the last non-zero coefficient does not require encoding for coded_sub_block_flag, and the subblock containing the DC information of the transform block has a high probability of including the nonzero coefficient, coded_sub_block_flag is not encoded and its value This can be assumed to be 1.

If the value of coded_sub_block_flag is 1 and it is determined that a non-zero coefficient exists in the current subblock, sig_coeff_flag having a binary value may be encoded according to the reversed order. A 1-bit syntax element sig_coeff_flag can be encoded for each coefficient according to the scan order. If the value of the transform coefficient at the current scan position is not 0, the value of sig_coeff_flag may be 1. Here, in the case of a sub-block including the last non-zero coefficient, since it is not necessary to encode sig_coeff_flag for the last non-zero coefficient, the encoding process for the sub-block 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. More 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. In one embodiment, sig_coeff_flag may correspond to an example of a valid coefficient flag indicating whether the quantized transform coefficient is a valid coefficient other than 0.

The remaining level value after encoding for sig_coeff_flag may be equal to Equation 1 below. That is, the syntax element remAbsLevel indicating the level value to be encoded may be equal to Equation 1 below. Here, coeff means the actual transform coefficient value.

[Equation 1]

remAbsLevel = |coeff| - One

Through par_level_flag, as shown in Equation 2 below, a least significant coefficient (LSB) value of remAbsLevel described in Equation 1 may be encoded. Here, par_level_flag[n] may indicate parity of the transform coefficient level (value) at the scanning position n. After par_leve_flag encoding, the transform coefficient level value remAbsLevel to be encoded may be updated as shown in Equation 3 below.

[Equation 2]

par_level_flag = remAbsLevel & 1

[Equation 3]

remAbsLevel' = remAbsLevel >> 1

rem_abs_gt1_flag may indicate whether remAbsLevel' at the corresponding scanning position n is greater than 1, and rem_abs_gt2_flag indicates whether remAbsLevel' at the corresponding scanning position n is greater than 2. The encoding for abs_remainder can be performed only when rem_abs_gt2_flag is 1. Summarizing the relationship between the actual transform coefficient value coeff and each syntax element, for example, it may be as shown in Equation 4 below, and Table 2 below shows examples related to Equation 4. In addition, the sign of each coefficient can be coded using a 1-bit symbol coeff_sign_flag. | coeff | represents the transform coefficient level (value), and may be expressed as AbsLevel for the transform coefficient.

[Equation 4]

| coeff | = sig_coeff_flag + par_level_flag + 2 * (rem_abs_gt1_flag + rem_abs_gt2_flag + abs_remainder)

|coeff|	sig_coeff_flag	par_level_flag	rem_abs_gt1_flag	rem_abs_gt2_flag	abs_remainder
0	0
One	One	0	0
2	One	One	0
3	One	0	One	0
4	One	One	One	0
5	One	0	One	One	0
6	One	One	One	One	0
7	One	0	One	One	One
8	One	One	One	One	One
9	One	0	One	One	2
10	One	One	One	One	2
11	One	0	One	One	3
...	...	...	...	...	...

Meanwhile, in one embodiment, the par_level_flag represents an example of a parity level flag indicating the parity of the transform coefficient level of the transform coefficient, and the rem_abs_gt1_flag is the first transform coefficient for whether the transform coefficient level of the transform coefficient is greater than a first threshold An example of the level flag is shown, and the rem_abs_gt2_flag or rem_abs_gt3_flag may represent an example of the second transform coefficient level flag as to whether the transform coefficient level of the transform coefficient is greater than a second threshold.

In another embodiment, the first transform coefficient level flag may be represented by abs_level_gt1_flag, and the second transform coefficient level flag may be represented by abs_level_gt3_flag or abs_level_gt2_flag.

In another embodiment, rem_abs_gt1_flag and rem_abs_gt2_flag may appear based on abs_level_gtx_flag[n][j]. abs_level_gtx_flag[n][j] may be a flag indicating whether an absolute value of a transform coefficient level (or a value obtained by shifting the transform coefficient level by 1 to the right) at scanning position n is greater than (j<<1)+1. . In one example, the rem_abs_gt1_flag may perform the same and/or similar functions as abs_level_gtx_flag[n][0], and the rem_abs_gt2_flag may perform the same and/or similar functions as abs_level_gtx_flag[n][1]. That is, the abs_level_gtx_flag[n][0] may correspond to an example of the first transform coefficient level flag, and the abs_level_gtx_flag[n][1] may correspond to an example of the second transform coefficient level flag. have. In some cases, (j<<1)+1 may be replaced with a predetermined threshold, such as a first threshold and a second threshold.

5 is a diagram showing an example of transform coefficients in a 4x4 block.

The 4x4 block of FIG. 5 shows an example of quantized coefficients. The block illustrated in FIG. 5 may be a 4x4 transform block or a 4x4 subblock of 8x8, 16x16, 32x32, and 64x64 transform blocks. The 4x4 block of FIG. 5 may represent a luminance block or a color difference block. The encoding result of the inverse diagonally scanned coefficients of FIG. 5 may be as shown in Table 3, for example. In Table 3, scan_pos indicates the position of the coefficient according to the inverse diagonal scan. scan_pos 15 is the coefficient of the bottom right corner that is scanned first in the 4x4 block, and scan_pos 0 represents the coefficient of the top left corner that is scanned last. Meanwhile, in one embodiment, the scan_pos may be referred to as a scan position. For example, scan_pos 0 may be referred to as scan position 0.

scan_pos	15	14	13	12	11	10	9	8	7	6	5	4	3	2	One	0
coefficients	0	0	0	0	One	-One	0	2	0	3	-2	-3	4	6	-7	10
sig_coeff_flag	0	0	0	0	One	One	0	One	0	One	One	One	One	One	One	One
par_level_flag					0	0		One		0	One	0	One	One	0	One
rem_abs_gt1_flag					0	0		0		One	0	One	One	One	One	One
rem_abs_gt2_flag										0		0	0	One	One	One
abs_remainder														0	One	2
ceoff_sign_flag					0	One		0		0	One	One	0	0	One	0

As described in Table 1, in one embodiment, 4x4 sub-block unit main syntax elements may include sig_coeff_flag, par_level_flag, rem_abs_gt1_flag, rem_abs_gt2_flag, abs_remainder, coeff_sign_flag, and the like. Among them, sig_coeff_flag, par_level_flag, rem_abs_gt1_flag, and rem_abs_gt2_flag can represent context encoding bins that are encoded using a regular encoding engine (that is, context-based coding is applied), and abs_remainder and coeff_sign_flag are bypass encoding engines. Can be used to indicate the bypass bin to be encoded.

In one embodiment, in the residual coding syntax, a valid coefficient flag (eg, sig_coeff_flag), a first transform coefficient level flag (eg, abs_level_gt1_flag or abs_level_gtx_flag[n) based on a repetition statement (eg, for statement, etc.) ][0], where n is an integer), and the second transform coefficient level flag (for example, abs_level_gt3_flag or abs_level_gtx_flag[n][1], where n is an integer), etc. It may be as shown in Table 4 or Table 5.

for (k...){

sig_coeff_flag[k]

if(sig_coeff_flag[k]){

abs_level_gt1_flag[k]

if(abs_level_gt1_flag[k])

par_level_flag[k]

}

}

for(k...){

if(abs_level_gt1_flag[k])

abs_level_gt3_flag[k]

}

for (k...){

abs_remainder[k]

}

for(k...){

dec_abs_level[k]

}

...

for (k...){

sig_coeff_flag[k]

if(sig_coeff_flag[k]){

abs_level_gtx_flag[k][0]

if(abs_level_gtx_flag[k][0])

par_level_flag[k]

}

}

for(k...){

if(abs_level_gtx_flag[k][0])

abs_level_gtx_flag[k][1]

}

for (k...){

abs_remainder[k]

}

for(k...){

dec_abs_level[k]

}

...

In one example according to Table 4 or Table 5, with respect to the first for statement, up to 28 bins may be allocated for a 4x4 sub-block, and up to 6 bins may be allocated for a 2x2 sub-block. In relation to the second for statement, up to 4 bins may be allocated for a 4x4 sub-block, and up to 2 bins may be allocated for a 2x2 sub-block. Bypass bins may be derived based on bypass coding in relation to the third for statement and the fourth for statement.

In one embodiment, the first transform coefficient level flags, the parity level flags and the second transform coefficient level flags may be included in one for statement in syntax to form one pass. have. Examples for this embodiment may be as shown in Table 6 or Table 7 below.

for (k...){

sig_coeff_flag[k]

if(sig_coeff_flag[k]){

abs_level_gt1_flag[k]

if(abs_level_gt1_flag[k]){

{

par_level_flag[k]

abs_level_gt3_flag[k]

}

}

}

for (k...){

abs_remainder[k]

}

for(k...){

dec_abs_level[k]

}

...

for (k...){

sig_coeff_flag[k]

if(sig_coeff_flag[k]){

abs_level_gtx_flag[k][0]

if(abs_level_gtx_flag[k][0]){

{

par_level_flag[k]

abs_level_gtx_flag[k][1]

}

}

}

for (k...){

abs_remainder[k]

}

for(k...){

dec_abs_level[k]

}

...

When the syntax elements are included in one for statement as shown in Table 6 or Table 7, all three syntax elements are parsed with respect to one transform coefficient, and then the next transform coefficient is considered, so that coding complexity is complex. And reduce coding delay.

In one example according to Table 6 or Table 7, with respect to the first for statement, up to K bins may be allocated for a 4x4 sub-block, and up to L bins may be allocated for a 2x2 sub-block.

Context-encoded bins can exhibit high data dependencies because they use the updated probability state and range while processing the previous bins. That is, parallel encoding may be difficult for the context-encoded bean since encoding/decoding of the current bin can be performed after encoding/decoding of the current bin is performed. In addition, it may take a long time to read the probability interval and determine the current state. Accordingly, in one embodiment, a method of improving CABAC throughput by reducing the number of context-encoding bins and increasing the number of bypass bins may be proposed.

In one embodiment, coefficient level information may be encoded in an inverse scan order. That is, it can be encoded after being scanned in the upper left direction starting from the coefficients in the lower right of the unit block. In one example, the count level that is first scanned in the reverse scan order may indicate a small value. Signaling par_level_flag, rem_abs_gt1_flag (or abs_level_gt1_flag: applies equally below) and rem_abs_gt2_flag (or abs_level_gt3_flag: equally applies below) for these first scanned coefficients reduces the length of the binarization bins to indicate the coefficient level Each syntax element can be efficiently coded through arithmetic coding based on a previously coded context using a predetermined context.

However, in the case of a coefficient level having some large values, that is, a coefficient level located at the upper left of the unit block, signaling par_level_flag, rem_abs_gt1_flag, and rem_abs_gt2_flag may not help to improve compression performance. Using par_level_flag, rem_abs_gt1_flag, and rem_abs_gt2_flag may decrease encoding efficiency.

In one embodiment, the context encoding bins are quickly switched to the abs_remainder syntax element encoded by the bypass encoding engine, that is, encoded by the bypass encoding engine (par_level_flag, rem_abs_gt1_flag, rem_abs_gt2_flag). The number can be reduced.

scan_pos	15	14	13	12	11	10	9	8	7	6	5	4	3	2	One	0
coefficients	0	0	0	0	One	-One	0	2	0	3	-2	-3	4	6	-7	10
sig_coeff_flag	0	0	0	0	One	One	0	One	0	One	One	One	One	One	One	One
par_level_flag					0	0		One		0	One	0	One	One	X	X
rem_abs_gt1_flag					0	0		0		One	0	One	One	One	X	X
rem_abs_gt2_flag										0		X	X	X	X	X
abs_remainder												0	0	One	6	9
ceoff_sign_flag					0	One		0		0	One	One	0	0	One	0

In one embodiment, a method for limiting the sum of the number of sig_coeff_flag, par_level_flag and rem_abs_gt1_flag may be proposed. When limiting the sum of the number of sig_coeff_flag, par_level_flag, and rem_abs_gt1_flag to K, K may have a value of 0 to 48. In this embodiment, if the sum of the number of sig_coeff_flag, par_level_flag, and rem_abs_gt1_flag exceeds K, and encoding for sig_coeff_flag, par_level_flag, and rem_abs_gt1_flag is not performed, rem_abs_gt2_flag may also not be encoded. Table 9 shows an example when K is determined to be 30.

scan_pos	15	14	13	12	11	10	9	8	7	6	5	4	3	2	One	0
coefficients	0	0	0	0	One	-One	0	2	0	3	-2	-3	4	6	-7	10
sig_coeff_flag	0	0	0	0	One	One	0	One	0	One	One	One	One	One	X	X
par_level_flag					0	0		One		0	One	0	One	One	X	X
rem_abs_gt1_flag					0	0		0		One	0	One	One	One	X	X
rem_abs_gt2_flag										0		0	0	One	X	X
abs_remainder														0	7	10
ceoff_sign_flag					0	One		0		0	One	One	0	0	One	0

In one embodiment, a method of limiting the sum of the numbers of sig_coeff_flag, par_level_flag, and rem_abs_gt1_flag and a method of limiting the number of rem_abs_gt2_flag described above may be combined. When the sum of the numbers of sig_coeff_flag, par_level_flag, and rem_abs_gt1_flag is limited to K, and the number of rem_abs_gt2_flag is limited to N, K may have a value from 0 to 48, and N may have a value from 0 to 16. Table 10 shows a case in which K is limited to 30 and N is limited to 2.

scan_pos	15	14	13	12	11	10	9	8	7	6	5	4	3	2	One	0
coefficients	0	0	0	0	One	-One	0	2	0	3	-2	-3	4	6	-7	10
sig_coeff_flag	0	0	0	0	One	One	0	One	0	One	One	One	One	One	X	X
par_level_flag					0	0		One		0	One	0	One	One	X	X
rem_abs_gt1_flag					0	0		0		One	0	One	One	One	X	X
rem_abs_gt2_flag										0		0	X	X	X	X
abs_remainder													0	One	7	10
ceoff_sign_flag					0	One		0		0	One	One	0	0	One	0

Referring to Table 6 or Table 7 described above again, in another example based on Table 6 or Table 7, the syntax elements sig_coeff_flag, abs_level_gt1_flag (or abs_level_gtx_flag[n][0]), par_level_flag, abs_level_gt3_flag(or abs_level_gtx_flag[n] [1]), abs_remainder, dec_abs_level, sig_coeff_flag, abs_level_gt1_flag (or abs_level_gtx_flag[n][0]), abs_level_gt3_flag (or abs_level_gt3_flag) which is encoded as a context encoding bin to improve throughput performance when encoding is performed in the order of dec_abs_level, coeff_sign_flag A method of limiting the sum of the number of abs_level_gtx_flag[n][1]) can be proposed. When the sum of the numbers of sig_coeff_flag, abs_level_gt1_flag (or abs_level_gtx_flag[n][0]), par_level_flag, and abs_level_gt3_flag (or abs_level_gtx_flag[n][1]) is limited to K, K may vary according to the size of the subblock. . In one example, if the size of the sub-block is 4x4, K can have an integer value of one of the integers from 0 to 64, and when the size of the sub-block is 2x2, K is one of the integers from 0 to 16 It can have an integer value of. Table 11 below shows another example of the case where the K is determined as 30 in the encoding process for the 4x4 sub-block as shown in FIG.

scan_pos	15	14	13	12	11	10	9	8	7	6	5	4	3	2	One	0
coefficients	0	0	0	0	One	-One	0	2	0	3	-2	-3	4	6	-7	10
sig_coeff_flag	0	0	0	0	One	One	0	One	0	One	One	One	One	X	X	X
abs_level_gt1_flagorabs_level_gtx_flag[n][0]					0	0		One		One	One	One	One	X	X	X
par_level_flag								0		One	0	One	0	X	X	X
abs_level_gt3_flagorabs_level_gtx_flag[n][1]								0		0	0	0	One	X	X	X
abs_remainder													0	X	X	X
dec_abs_level														6	7	10
coeff_sign_flag					0	One		0		0	One	One	0	0	One	0

6 is a flowchart illustrating an operation of an encoding device according to an embodiment, and FIG. 7 is a block diagram showing a configuration of an encoding device according to an embodiment.

The encoding device according to FIGS. 6 and 7 may perform operations corresponding to the decoding device according to FIGS. 8 and 9. Accordingly, the operations of the decoding device to be described later in FIGS. 8 and 9 can be applied to the encoding device according to FIGS. 6 and 7 as well.

Each step disclosed in FIG. 6 may be performed by the encoding apparatus 200 disclosed in FIG. 2. More specifically, S600 may be performed by the subtraction unit 231 illustrated in FIG. 2, S610 may be performed by the conversion unit 232 illustrated in FIG. 2, and S620 may be performed by the quantization unit 233 illustrated in FIG. 2. ), and S630 may be performed by the entropy encoding unit 240 illustrated in FIG. 2. In addition, the operations according to S600 to S630 are based on some of the contents described in FIGS. 4 and 5. Accordingly, detailed descriptions that overlap with those described above in FIGS. 2, 4, and 5 will be omitted or simplified.

As illustrated in FIG. 7, the encoding apparatus according to an embodiment may include a subtraction unit 231, a conversion unit 232, a quantization unit 233, and an entropy encoding unit 240. However, in some cases, all of the components shown in FIG. 7 may not be essential components of the encoding device, and the encoding device may be implemented by more or less components than those shown in FIG. 7.

In the encoding apparatus according to an embodiment, the subtraction unit 231, the conversion unit 232, the quantization unit 233, and the entropy encoding unit 240 may be implemented as separate chips, or at least two or more components may be used. It can also be implemented through a single chip.

The encoding apparatus according to an embodiment may derive residual samples for the current block (S600). More specifically, the subtraction unit 231 of the encoding device may derive residual samples for the current block.

The encoding apparatus according to an embodiment may transform the residual samples for the current block to derive transform coefficients for the current block (S610). More specifically, the conversion unit 232 of the encoding device may convert the residual samples for the current block to derive conversion coefficients for the current block.

The encoding apparatus according to an embodiment may derive quantized transform coefficients from the transform coefficients based on a quantization process (S620). More specifically, the quantization unit 233 of the encoding apparatus may derive quantized transform coefficients from the transform coefficients based on a quantization process.

The encoding apparatus according to an embodiment may encode residual information including information about the quantized transform coefficients (S630). More specifically, the entropy encoding unit 240 of the encoding device may encode residual information including information about the quantized transform coefficients.

In one embodiment, the transform coefficients for the current block may include a first transform coefficient and a second transform coefficient coded later than the first transform coefficient. The residual information includes a first transform coefficient level flag for the first transform coefficient indicating whether the transform coefficient level of the first transform coefficient is greater than a first threshold, and a transform coefficient level of the first transform coefficient is second. A second transform coefficient level flag for the first transform coefficient indicating whether it is greater than a threshold, a first transform coefficient for the second transform coefficient indicating whether the transform coefficient level of the second transform coefficient is greater than the first threshold A level flag and a second transform coefficient level flag for the second transform coefficient indicating whether the transform coefficient level of the second transform coefficient is greater than the second threshold may be included. At this time, the second threshold may be greater than the first threshold.

Encoding apparatus according to an embodiment encoding the residual information, the first transform coefficient level flag for the first transform coefficient, the first transform coefficient based on the transform coefficients for the current block And encoding the second transform coefficient level flag for, the first transform coefficient level flag for the second transform coefficient, and the second transform coefficient level flag for the second transform coefficient.

In one embodiment, the second transform coefficient level flag for the first transform coefficient may be encoded before the first transform coefficient level flag for the second transform coefficient.

In one embodiment, the residual information includes a parity level flag for the first transform coefficient indicating the parity of the transform coefficient level of the first transform coefficient and the transform coefficient level of the second transform coefficient. A parity level flag for the second transform coefficient indicating parity may be further included. In this case, the second transform coefficient level flag for the first transform coefficient may be encoded before the parity level flag for the second transform coefficient.

In one embodiment, the second transform coefficient level flag for the first transform coefficient is encoded before the first transform coefficient level flag for the second transform coefficient, and the first transform for the second transform coefficient The coefficient level flag may be encoded before the parity level flag for the second transform coefficient.

In one embodiment, the first transform coefficient level flag for the first transform coefficient is encoded before the parity level flag for the first transform coefficient, and the parity level flag for the first transform coefficient is the first transform coefficient. The first transform coefficient level flag for the first transform coefficient is encoded before the second transform coefficient level flag for the first transform coefficient, and the second transform coefficient level flag for the first transform coefficient is encoded before the first transform coefficient level flag for the second transform coefficient. , The first transform coefficient level flag for the second transform coefficient is encoded before the parity level flag for the second transform coefficient, and the parity level flag for the second transform coefficient is assigned to the second transform coefficient. For the second transform coefficient level flag.

In one embodiment, the residual information comprises: the transform for the current block including the first transform coefficient level flag for the first transform coefficient and the first transform coefficient level flag for the second transform coefficient. To the current block including first transform coefficient level flags for coefficients, the second transform coefficient level flag for the first transform coefficient, and the second transform coefficient level flag for the second transform coefficient. The second transform coefficient level flags for the transform coefficients for, the transform for the current block including the parity level flag for the first transform coefficient and the parity level flag for the second transform coefficient A validity coefficient flag for the transform coefficients for the current block, including parity level flags for the coefficients, and indicating whether the transform coefficient level of each of the transform coefficients for the current block is a non-zero valid coefficient. The sum of the number of first transform coefficient level flags, the number of second transform coefficient level flags, the number of parity level flags, and the number of valid coefficient flags may be less than or equal to a predetermined threshold.

In one embodiment, based on the determination that the size of the current block is a 4x4 block size, the predetermined threshold is determined as a first threshold, and based on the determination that the size of the current block is a 2x2 block size, the predetermined The threshold may be determined as a second threshold.

In one embodiment, context-based coding may be applied to the first transform coefficient level flags, the second transform coefficient level flags, the parity level flags, and the effective coefficient flags.

According to the encoding apparatus of FIG. 6 and FIG. 7 and an operating method of the encoding apparatus, the encoding apparatus derives residual samples for the current block (S600), converts the residual samples for the current block, and converts the residual samples to the current block. Derivation of transform coefficients for (S610), deriving quantized transform coefficients from the transform coefficients based on a quantization process (S620), and encoding residual information including information about the quantized transform coefficients (S630) ), wherein the transform coefficients for the current block include a first transform coefficient and a second transform coefficient that is coded later than the first transform coefficient, and the residual information comprises: A first transform coefficient level flag for the first transform coefficient indicating whether a transform coefficient level is greater than a first threshold, a first transform coefficient indicating whether the transform coefficient level of the first transform coefficient is greater than a second threshold Second transform coefficient level flag for, the first transform coefficient level flag for the second transform coefficient indicating whether the transform coefficient level of the second transform coefficient is greater than the first threshold, and the transform coefficient level of the second transform coefficient The second transform coefficient level flag for the second transform coefficient indicating whether the second threshold value is greater than or equal to the second threshold value, wherein the second threshold value is greater than the first threshold value, and encoding the residual information includes: Based on the transform coefficients for the current block, the first transform coefficient level flag for the first transform coefficient, the second transform coefficient level flag for the first transform coefficient, and the first for the second transform coefficient Encoding a first transform coefficient level flag and the second transform coefficient level flag for the second transform coefficient, and the second transform coefficient level flag for the first transform coefficient is for the second transform coefficient It may be characterized in that it is encoded before the first transform coefficient level flag.

That is, according to the present disclosure, coding efficiency of a transform coefficient level of transform coefficients can be increased. In addition, according to the present disclosure, a parity level flag and a transform coefficient for a parity of a transform coefficient level include a second transform coefficient level flag indicating whether a transform coefficient level is greater than a second threshold in syntax structure. Coding complexity and delay can be reduced by having the level coded in the same pass as the first transform coefficient level flag indicating whether the level is greater than the first threshold. In addition, according to the present disclosure, the number of valid coefficient flags for transform coefficients for the current block indicating whether the transform coefficient level of each of the transform coefficients for the current block is a non-zero valid coefficient, the first transform coefficient level flags By limiting the sum of the number, the number of second transform coefficient level flags, and the number of parity level flags to a predetermined threshold or less, coding complexity and delay can be reduced.

8 is a flowchart illustrating an operation of a decoding apparatus according to an embodiment, and FIG. 9 is a block diagram showing a configuration of a decoding apparatus according to an embodiment.

Each step disclosed in FIG. 8 may be performed by the decoding apparatus 300 disclosed in FIG. 3. More specifically, S800 and S810 may be performed by the entropy decoding unit 310 disclosed in FIG. 3, S820 may be performed by the inverse quantization unit 321 illustrated in FIG. 3, and S830 disclosed by FIG. 3 It may be performed by the inverse transform unit 322, S840 may be performed by the adder 340 disclosed in FIG. In addition, the operations according to S800 to S840 are based on some of the contents described in FIGS. 4 to 5. Therefore, detailed descriptions that overlap with those described above in FIGS. 3 to 5 will be omitted or simplified.

As illustrated in FIG. 9, the decoding apparatus according to an embodiment may include an entropy decoding unit 310, an inverse quantization unit 321, an inverse transformation unit 322, and an addition unit 340. However, in some cases, all of the components illustrated in FIG. 9 may not be essential components of the decoding apparatus, and the decoding apparatus may be implemented by more or fewer components than those illustrated in FIG. 9.

In the decoding apparatus according to an embodiment, the entropy decoding unit 310, the inverse quantization unit 321, the inverse conversion unit 322, and the addition unit 340 are each implemented as separate chips, or at least two or more components May be implemented through a single chip.

The decoding apparatus according to an embodiment may receive a bitstream including residual information (S800). More specifically, the entropy decoding unit 310 of the decoding apparatus may receive a bitstream including residual information.

The decoding apparatus according to an embodiment may derive quantized transform coefficients for the current block based on the residual information included in the bitstream (S810). More specifically, the entropy decoding unit 310 of the decoding apparatus may derive quantized transform coefficients for the current block based on the residual information included in the bitstream.

The decoding apparatus according to an embodiment may derive transform coefficients for the current block from the quantized transform coefficients based on an inverse quantization process (S820). More specifically, the inverse quantization unit 321 of the decoding apparatus may derive transform coefficients for the current block from the quantized transform coefficients based on an inverse quantization process.

The decoding apparatus according to an embodiment may derive residual samples for the current block by applying an inverse transform to the derived transform coefficients (S830). More specifically, the inverse transform unit 322 of the decoding apparatus may derive residual samples for the current block by applying an inverse transform to the derived transform coefficients.

The decoding apparatus according to an embodiment may generate a reconstructed picture based on the residual sample for the current block (S840). More specifically, the adder 340 of the decoding apparatus may generate a reconstructed picture based on the residual sample for the current block.

In one embodiment, the transform coefficients for the current block may include a first transform coefficient and a second transform coefficient coded later than the first transform coefficient. The residual information includes a first transform coefficient level flag for the first transform coefficient indicating whether the transform coefficient level of the first transform coefficient is greater than a first threshold, and a transform coefficient level of the first transform coefficient is second. A second transform coefficient level flag for the first transform coefficient indicating whether it is greater than a threshold, a first transform coefficient for the second transform coefficient indicating whether the transform coefficient level of the second transform coefficient is greater than the first threshold A level flag and a second transform coefficient level flag for the second transform coefficient indicating whether the transform coefficient level of the second transform coefficient is greater than the second threshold may be included. At this time, the second threshold may be greater than the first threshold.

In one example, when the index corresponding to the first transform coefficient is z and the index corresponding to the second transform coefficient is z+1 (where z is an integer), the first transform to the first transform coefficient The coefficient level flag is represented by abs_level_gt1_flag[z], the second transform coefficient level flag for the first transform coefficient is abs_level_gt3_flag[z], and the first transform coefficient level flag for the second transform coefficient is abs_level_gt1_flag[ z+1], and the second transform coefficient level flag for the second transform coefficient may be represented by abs_level_gt3_flag[z+1].

In another example, when an index corresponding to the first transform coefficient is z and an index corresponding to the second transform coefficient is z+1 (where z is an integer), the first transform coefficient is relative to the first transform coefficient. The transform coefficient level flag is represented by abs_level_gtx_flag[z][0], the second transform coefficient level flag for the first transform coefficient is abs_level_gtx_flag[z][1], and the first for the second transform coefficient The transform coefficient level flag is represented by abs_level_gtx_flag[z+1][0], and the second transform coefficient level flag for the second transform coefficient can be represented by abs_level_gtx_flag[z+1][1]. In this case, the first threshold may be determined as (0<<1)+1=1, and the second threshold may be determined as (1<<1)+1=3, but embodiments are not limited thereto. For example, the first threshold may be determined as 1 and the second threshold may be 2.

The decoding apparatus according to an embodiment deriving the quantized transform coefficients for the current block includes: the first transform coefficient level flag for the first transform coefficient and the second transform for the first transform coefficient And parsing a coefficient level flag, the first transform coefficient level flag for the second transform coefficient, and the second transform coefficient level flag for the second transform coefficient.

The decoding apparatus according to an embodiment deriving the transform coefficients for the current block includes: the first transform coefficient level flag for the first transform coefficient, and the second transform coefficient level for the first transform coefficient Deriving the transform coefficients for the current block based on a flag, the first transform coefficient level flag for the second transform coefficient, and the second transform coefficient level flag for the second transform coefficient. have.

In one embodiment, the second transform coefficient level flag for the first transform coefficient may be parsed before the first transform coefficient level flag for the second transform coefficient. In one example, abs_level_gtx_flag[z][1] may be parsed before abs_level_gtx_flag[z+1][0].

In one embodiment, the residual information includes a parity level flag for the first transform coefficient indicating the parity of the transform coefficient level of the first transform coefficient and the transform coefficient level of the second transform coefficient. A parity level flag for the second transform coefficient indicating parity may be further included. At this time, the second transform coefficient level flag for the first transform coefficient may be parsed before the parity level flag for the second transform coefficient.

In one example, when an index corresponding to the first transform coefficient is z and an index corresponding to the second transform coefficient is z+1, the parity level flag for the first transform coefficient is represented by par_level_flag[z] , The parity level flag for the second transform coefficient may be represented by par_level_flag[z+1].

In one embodiment, the second transform coefficient level flag for the first transform coefficient is parsed before the first transform coefficient level flag for the second transform coefficient, and the first transform for the second transform coefficient The coefficient level flag may be parsed before the parity level flag for the second transform coefficient.

In one embodiment, the first transform coefficient level flag for the first transform coefficient is parsed before the parity level flag for the first transform coefficient, and the parity level flag for the first transform coefficient is the first transform coefficient. The second transform coefficient level flag for the first transform coefficient is parsed before the second transform coefficient level flag for the first transform coefficient, and the second transform coefficient level flag for the first transform coefficient is parsed before the first transform coefficient level flag for the second transform coefficient , The first transform coefficient level flag for the second transform coefficient is parsed before the parity level flag for the second transform coefficient, and the parity level flag for the second transform coefficient is assigned to the second transform coefficient. May be parsed before the second transform coefficient level flag.

In one embodiment, the residual information comprises: the transform for the current block including the first transform coefficient level flag for the first transform coefficient and the first transform coefficient level flag for the second transform coefficient. To the current block including first transform coefficient level flags for coefficients, the second transform coefficient level flag for the first transform coefficient, and the second transform coefficient level flag for the second transform coefficient. The second transform coefficient level flags for the transform coefficients for, the transform for the current block including the parity level flag for the first transform coefficient and the parity level flag for the second transform coefficient A validity coefficient flag for the transform coefficients for the current block, including parity level flags for the coefficients, and indicating whether the transform coefficient level of each of the transform coefficients for the current block is a non-zero valid coefficient. The sum of the number of first transform coefficient level flags, the number of second transform coefficient level flags, the number of parity level flags, and the number of valid coefficient flags may be less than or equal to a predetermined threshold.

In one embodiment, based on the determination that the size of the current block is a 4x4 block size, the predetermined threshold is determined as a first threshold, and based on the determination that the size of the current block is a 2x2 block size, the predetermined The threshold may be determined as a second threshold.

In one embodiment, context-based coding may be applied to the first transform coefficient level flags, the second transform coefficient level flags, the parity level flags, and the effective coefficient flags.

In one embodiment, the first transform coefficient level flags, the parity level flags and the second transform coefficient level flags may be included in one for statement in syntax to form one pass. have. When the syntax elements are included in one for statement, all three syntax elements are parsed with respect to one transform coefficient, and then the next transform coefficient is considered, thereby reducing coding complexity and reducing coding delay. have. In order to reduce coding delay by forming a pass by including the first transform coefficient level flags, the parity level flags, and the second transform coefficient level flags in one for statement in syntax, for example, Table 12 below The syntax structure described in can be used. Table 12 below may be the same and/or similar to Table 7 above.

for (k...){

sig_coeff_flag[k]

if(sig_coeff_flag[k]){

abs_level_gtx_flag[k][0]

if(abs_level_gtx_flag[k][0]){

{

par_level_flag[k]

abs_level_gtx_flag[k][1]

}

}

}

for (k...){

abs_remainder[k]

}

for(k...){

dec_abs_level[k]

}

...

In Table 12, sig_coeff_flag[k] represents an example of valid coefficient flags, abs_level_gtx_flag[k][0] represents an example of the first transform coefficient level flags, and par_level_flag[k] represents one of the parity level flags. An example is illustrated, and abs_level_gtx_flag[k][1] represents an example of the second transform coefficient level flags.

According to the decoding apparatus and an operating method of the decoding apparatus disclosed in FIGS. 8 and 9, the decoding apparatus receives a bitstream including residual information (S800), and is currently based on the residual information included in the bitstream. Derive quantized transform coefficients for the block (S810), derive transform coefficients for the current block from the quantized transform coefficients based on an inverse quantization process (S820), and inverse transform the derived transform coefficients Apply to derive residual samples for the current block (S830), and may generate a reconstructed picture based on the residual sample for the current block (S840), wherein the transform coefficients for the current block are , A first transform coefficient and a second transform coefficient coded later than the first transform coefficient, and the residual information indicates whether the transform coefficient level of the first transform coefficient is greater than a first threshold value. A first transform coefficient level flag for the transform coefficient, a second transform coefficient level flag for the first transform coefficient indicating whether the transform coefficient level of the first transform coefficient is greater than a second threshold, a transform of the second transform coefficient A first transform coefficient level flag for the second transform coefficient indicating whether a coefficient level is greater than the first threshold and a second transform coefficient indicating whether a transform coefficient level of the second transform coefficient is greater than the second threshold And a second transform coefficient level flag for, wherein the second threshold is greater than the first threshold, and deriving the quantized transform coefficients for the current block includes: the first transform coefficient for the first transform coefficient; A transform coefficient level flag, the second transform coefficient level flag for the first transform coefficient, the first transform coefficient level flag for the second transform coefficient, and the second transform coefficient level flag for the second transform coefficient Parsing, and deriving the transform coefficients for the current block, The first transform coefficient level flag for the first transform coefficient, the second transform coefficient level flag for the first transform coefficient, the first transform coefficient level flag for the second transform coefficient, and the second transform coefficient And deriving the transform coefficients for the current block based on the second transform coefficient level flag for and wherein the second transform coefficient level flag for the first transform coefficient is for the second transform coefficient. It may be characterized in that it is parsed before the first transform coefficient level flag.

That is, according to the present disclosure, coding efficiency of a transform coefficient level of transform coefficients can be increased. In addition, according to the present disclosure, a parity level flag and a transform coefficient for a parity of a transform coefficient level include a second transform coefficient level flag indicating whether a transform coefficient level is greater than a second threshold in syntax structure. Coding complexity and delay can be reduced by having the level coded in the same pass as the first transform coefficient level flag indicating whether the level is greater than the first threshold. In addition, according to the present disclosure, the number of valid coefficient flags for transform coefficients for the current block indicating whether the transform coefficient level of each of the transform coefficients for the current block is a non-zero valid coefficient, the first transform coefficient level flags By limiting the sum of the number, the number of second transform coefficient level flags, and the number of parity level flags to a predetermined threshold or less, coding complexity and delay can be reduced.

In the above-described embodiment, the methods are described based on a flow chart as a series of steps or blocks, but the present disclosure is not limited to the order of steps, and some steps may occur in a different order or simultaneously with other steps as described above. have. In addition, those skilled in the art will understand 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 the present disclosure.

The above-described method according to the present disclosure may be implemented in software form, and the encoding device and/or the decoding device according to the present disclosure may perform image processing, such as a TV, computer, smartphone, set-top box, display device, etc. Device.

When embodiments are implemented in software in the present disclosure, the above-described method may be implemented as a module (process, function, etc.) performing the above-described function. Modules are stored in memory and can be executed by a processor. The memory may be internal or external to the processor, and may be connected to the processor by various well-known means. The processor may include an application-specific integrated circuit (ASIC), other chipsets, logic circuits, and/or data processing devices. The memory may include read-only memory (ROM), random access memory (RAM), flash memory, memory cards, storage media and/or other storage devices. That is, the embodiments described in the present disclosure may be implemented and implemented on a processor, microprocessor, controller, or chip. For example, the functional units shown in each figure may be implemented and implemented 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, the decoding device and encoding device to which the present disclosure is applied include a multimedia broadcast transmission/reception device, a mobile communication terminal, a home cinema video device, a digital cinema video device, a surveillance camera, a video communication device, a real-time communication device such as video communication, mobile streaming Devices, storage media, camcorders, video-on-demand (VoD) service providers, OTT video (Over the top video) devices, Internet streaming service providers, 3D (3D) video devices, VR (virtual reality) devices, AR (argumente) reality) devices, video telephony video devices, transportation terminal (ex. vehicles (including self-driving vehicles) terminals, airplane terminals, ship terminals, etc.) and medical video devices, and may be used to process video signals or data signals Can. For example, the 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, or a digital video recorder (DVR).

Further, the processing method to which the present disclosure is applied can be produced in the form of a computer-implemented program and stored in a computer-readable recording medium. Multimedia data having a data structure according to the present disclosure 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 Disc (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. In addition, the computer-readable recording medium includes media implemented in the form of a carrier wave (for example, transmission via 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, embodiments of the present disclosure may be implemented as computer program products using program codes, and the program codes may be executed on a computer by embodiments of the present disclosure. The program code can be stored on a computer readable carrier.

10 shows an example of a content streaming system to which the invention disclosed in this document can be applied.

Referring to FIG. 10, a content streaming system to which the present disclosure is applied may largely include an encoding server, a streaming server, a web server, a media storage, a user device, and a multimedia input device.

The encoding server serves to compress a content input from multimedia input devices such as a smart phone, a camera, and a camcorder into digital data to generate a bitstream and transmit it to the streaming server. As another example, when multimedia input devices such as a smart phone, a camera, and a camcorder directly generate a bitstream, the encoding server may be omitted.

The bitstream may be generated by an encoding method or a bitstream generation method to which the present disclosure is applied, and the streaming server may temporarily store the bitstream in the process of 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 to inform the user of the service. When a user requests a desired service from the web server, the web server delivers it to the streaming server, and the streaming server transmits multimedia data to the user. At this time, the content streaming system may include a separate control server, in which 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 terminal for digital broadcasting, a personal digital assistants (PDA), a portable multimedia player (PMP), navigation, a slate PC, Tablet PC, ultrabook, wearable device (e.g., smartwatch, smart glass, head mounted display (HMD)), digital TV, desktop Computers, digital signage, and the like.

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

Claims (15)

1. In the video decoding method performed by the decoding device,

   Receiving a bitstream including residual information;

   Deriving quantized transform coefficients for the current block based on the residual information included in the bitstream;

   Deriving transform coefficients for the current block from the quantized transform coefficients based on an inverse quantization process;

   Deriving residual samples for the current block by applying an inverse transform to the derived transform coefficients; And

   Generating a reconstructed picture based on the residual samples for the current block,

   The transform coefficients for the current block include a first transform coefficient and a second transform coefficient coded after the first transform coefficient,

   The residual information includes a first transform coefficient level flag for the first transform coefficient indicating whether the transform coefficient level of the first transform coefficient is greater than a first threshold, and a transform coefficient level of the first transform coefficient is second. A second transform coefficient level flag for the first transform coefficient indicating whether it is greater than a threshold, a first transform coefficient for the second transform coefficient indicating whether the transform coefficient level of the second transform coefficient is greater than the first threshold A level flag and a second transform coefficient level flag for the second transform coefficient indicating whether the transform coefficient level of the second transform coefficient is greater than the second threshold,

   The second threshold is greater than the first threshold,

   Deriving the quantized transform coefficients for the current block,

   The first transform coefficient level flag for the first transform coefficient, the second transform coefficient level flag for the first transform coefficient, the first transform coefficient level flag for the second transform coefficient, and the second transform coefficient Parsing the second transform coefficient level flag for,

   Deriving the transform coefficients for the current block,

   The first transform coefficient level flag for the first transform coefficient, the second transform coefficient level flag for the first transform coefficient, the first transform coefficient level flag for the second transform coefficient, and the second transform coefficient Deriving the transform coefficients for the current block based on the second transform coefficient level flag for,

   And the second transform coefficient level flag for the first transform coefficient is parsed before the first transform coefficient level flag for the second transform coefficient.
2. According to claim 1,

   The residual information may include a parity level flag for the first transform coefficient indicating the parity of the transform coefficient level of the first transform coefficient and a parity of the transform coefficient level of the second transform coefficient. 2 further includes a parity level flag for the transform coefficient,

   And the second transform coefficient level flag for the first transform coefficient is parsed before the parity level flag for the second transform coefficient.
3. According to claim 2,

   The second transform coefficient level flag for the first transform coefficient is parsed before the first transform coefficient level flag for the second transform coefficient, and the first transform coefficient level flag for the second transform coefficient is the And parsing before the parity level flag for a second transform coefficient.
4. According to claim 1,

   The first transform coefficient level flag for the first transform coefficient is parsed before the parity level flag for the first transform coefficient, and the parity level flag for the first transform coefficient is for the first transform coefficient. The second transform coefficient level flag is parsed before the second transform coefficient level flag, and the second transform coefficient level flag for the first transform coefficient is parsed before the first transform coefficient level flag for the second transform coefficient, and the second transform is The first transform coefficient level flag for a coefficient is parsed before the parity level flag for the second transform coefficient, and the parity level flag for the second transform coefficient is the second transform for the second transform coefficient. And parsing before the coefficient level flag.
5. According to claim 1,

   The residual information is:

   First transform coefficient level flags for the transform coefficients for the current block including the first transform coefficient level flag for the first transform coefficient and the first transform coefficient level flag for the second transform coefficient Including,

   Second transform coefficient level flags for the transform coefficients for the current block including the second transform coefficient level flag for the first transform coefficient and the second transform coefficient level flag for the second transform coefficient Including,

   And parity level flags for the transform coefficients for the current block including the parity level flag for the first transform coefficient and the parity level flag for the second transform coefficient,

   And effective coefficient flags for the transform coefficients for the current block indicating whether the transform coefficient level of each of the transform coefficients for the current block is a non-zero valid coefficient,

   The sum of the number of first transform coefficient level flags, the number of second transform coefficient level flags, the number of parity level flags, and the number of valid coefficient flags is equal to or less than a predetermined threshold.
6. The method of claim 5,

   Based on the determination that the size of the current block is a 4x4 block size, the predetermined threshold is determined as a first threshold,

   Based on the determination that the size of the current block is a 2x2 block size, the predetermined threshold is determined as a second threshold.
7. The method of claim 5,

   Video decoding, characterized in that context-based coding is applied to the first transform coefficient level flags, the second transform coefficient level flags, the parity level flags, and the effective coefficient flags Way.
8. In the video encoding method performed by the encoding device,

   Deriving residual samples for the current block;

   Transforming the residual samples for the current block to derive transform coefficients for the current block;

   Deriving quantized transform coefficients from the transform coefficients based on a quantization process; And

   Encoding residual information including information about the quantized transform coefficients,

   The transform coefficients for the current block include a first transform coefficient and a second transform coefficient coded after the first transform coefficient,

   The residual information includes a first transform coefficient level flag for the first transform coefficient indicating whether the transform coefficient level of the first transform coefficient is greater than a first threshold, and a transform coefficient level of the first transform coefficient is second. A second transform coefficient level flag for the first transform coefficient indicating whether it is greater than a threshold, a first transform coefficient for the second transform coefficient indicating whether the transform coefficient level of the second transform coefficient is greater than the first threshold A level flag and a second transform coefficient level flag for the second transform coefficient indicating whether the transform coefficient level of the second transform coefficient is greater than the second threshold,

   The second threshold is greater than the first threshold,

   Encoding the residual information,

   Based on the transform coefficients for the current block, the first transform coefficient level flag for the first transform coefficient, the second transform coefficient level flag for the first transform coefficient, and the second transform coefficient Encoding a first transform coefficient level flag and the second transform coefficient level flag for the second transform coefficient,

   And the second transform coefficient level flag for the first transform coefficient is encoded before the first transform coefficient level flag for the second transform coefficient.
9. The method of claim 8,

   The residual information may include a parity level flag for the first transform coefficient indicating the parity of the transform coefficient level of the first transform coefficient and a parity of the transform coefficient level of the second transform coefficient. 2 further includes a parity level flag for the transform coefficient,

   And the second transform coefficient level flag for the first transform coefficient is encoded before the parity level flag for the second transform coefficient.
10. The method of claim 9,

    The second transform coefficient level flag for the first transform coefficient is encoded before the first transform coefficient level flag for the second transform coefficient, and the first transform coefficient level flag for the second transform coefficient is the And encoding the parity level flag for a second transform coefficient.
11. The method of claim 8,

    The first transform coefficient level flag for the first transform coefficient is encoded before the parity level flag for the first transform coefficient, and the parity level flag for the first transform coefficient is for the first transform coefficient. The second transform coefficient level flag is encoded before the second transform coefficient level flag, and the second transform coefficient level flag for the first transform coefficient is encoded before the first transform coefficient level flag for the second transform coefficient, and the second transform is The first transform coefficient level flag for a coefficient is encoded before the parity level flag for the second transform coefficient, and the parity level flag for the second transform coefficient is the second transform for the second transform coefficient. Video encoding method characterized in that it is encoded before the coefficient level flag.
12. The method of claim 8,

    The residual information is:

    First transform coefficient level flags for the transform coefficients for the current block including the first transform coefficient level flag for the first transform coefficient and the first transform coefficient level flag for the second transform coefficient Including,

    Second transform coefficient level flags for the transform coefficients for the current block including the second transform coefficient level flag for the first transform coefficient and the second transform coefficient level flag for the second transform coefficient Including,

    And parity level flags for the transform coefficients for the current block including the parity level flag for the first transform coefficient and the parity level flag for the second transform coefficient,

    And effective coefficient flags for the transform coefficients for the current block indicating whether the transform coefficient level of each of the transform coefficients for the current block is a non-zero valid coefficient,

    The sum of the number of first transform coefficient level flags, the number of second transform coefficient level flags, the number of parity level flags, and the number of valid coefficient flags is equal to or less than a predetermined threshold.
13. The method of claim 12,

    Based on the determination that the size of the current block is a 4x4 block size, the predetermined threshold is determined as a first threshold,

    Based on the determination that the size of the current block is a 2x2 block size, the predetermined threshold is determined as a second threshold, the video encoding method.
14. The method of claim 12,

    Video encoding, characterized in that context-based coding is applied to the first transform coefficient level flags, the second transform coefficient level flags, the parity level flags, and the effective coefficient flags Way.
15. In the decoding apparatus for performing video decoding,

    An entropy decoding unit receiving a bitstream including residual information and deriving quantized transform coefficients for a current block based on the residual information included in the bitstream;

    An inverse quantization unit that derives transform coefficients for the current block from the quantized transform coefficients based on an inverse quantization process;

    An inverse transform unit for deriving residual samples for the current block by applying an inverse transform to the derived transform coefficients; And

    And an adder for generating a reconstructed picture based on the residual sample for the current block,

    The transform coefficients for the current block include a first transform coefficient and a second transform coefficient coded later than the first transform coefficient,

    The residual information includes a first transform coefficient level flag for the first transform coefficient indicating whether the transform coefficient level of the first transform coefficient is greater than a first threshold, and a transform coefficient level of the first transform coefficient is second. A second transform coefficient level flag for the first transform coefficient indicating whether it is greater than a threshold, a first transform coefficient for the second transform coefficient indicating whether the transform coefficient level of the second transform coefficient is greater than the first threshold A level flag and a second transform coefficient level flag for the second transform coefficient indicating whether the transform coefficient level of the second transform coefficient is greater than the second threshold,

    The second threshold is greater than the first threshold,

    Deriving the quantized transform coefficients for the current block performed by the entropy decoding unit,

    The first transform coefficient level flag for the first transform coefficient, the second transform coefficient level flag for the first transform coefficient, the first transform coefficient level flag for the second transform coefficient, and the second transform coefficient Parsing the second transform coefficient level flag for,

    The step of deriving the transform coefficients for the current block performed by the inverse quantization unit may include:

    The first transform coefficient level flag for the first transform coefficient, the second transform coefficient level flag for the first transform coefficient, the first transform coefficient level flag for the second transform coefficient, and the second transform coefficient Deriving the transform coefficients for the current block based on the second transform coefficient level flag for,

    And the second transform coefficient level flag for the first transform coefficient is parsed before the first transform coefficient level flag for the second transform coefficient.

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